Experimental results and future opportunities in particle physics

EXPERIMENTAL RESULTS AND FUTURE OPPORTUNITIES IN PARTICLE PHYSICS Presented at XVII International Symposium on lepton-photon Beijing, August 15, 1995

interactions,

Samuel C.C. TING

CERN, CH-1211 Geneva 23, Switzerland and MIT, Cambridge MA, USA

ELSES’IER

AMSTERDAM

~ LAUSANNE

~ NEW YORK

- OXFORD

- SHANNON

-- TOKYO

PHYSICS

ELSEVIER

REPORTS

Physics Reports 279 (1997) 203-250

Experimental results and future opportunities in particle physics Presented

at XVII International Symposium on lepton-photon Beijing, August 15, 1995

Samuel

interactions,

C.C. Ting

CERN, CH-1211 Geneva 23, Switzerland and MIT, Cambridge MA, USA Received May 1996; editor: J.V. Allaby

Contents:

I. Introduction 2. Highlights of recent experimental 2.1. Tests of CPT 2.2. Results from IHEP 2.3. Results from CESR

results

2.4. Results from TRISTAN 2.5. Results from BNL 2.6. Fom SLAC 2.7. Results from LEP 2.8. Results from Fermi National Laboratory 2.9. Results from HERA 3. Future plans 3.1. In Italy: INFN Frascati Laboratory

205 205 205 205

205 208 208 210 211 223 225 229 229

3.2. In China: the tau-charm factory 3.3. In the US 3.4. In Japan: at the National Laboratory High Energy Physics, KEK 3.5. In Germany: at DESY 3.6. At CERN 4. Particle physics without accelerators 4.1. The MACRO experiment 4.2. The Super-Kamiokande experiment 4.3. The AMS experiment 5. Conclusion Acknowledgement References

229 230 for 235 235 238 243 243 244 244 250 250 250

Abstract This article is based on the summary talk presented at the XVII International Symposium on Lepton-Photon Interactions in Beijing, China, on 15 August 1995. It includes a selection of highlights of experimental results and future plans of different laboratories, as seen by each Laboratory Management. It also presents some particle physics experiments underground and in space. PAC.9 10. Keywords: Elementary

particles; High energy physics

0370-1573/97/!$32.00 Copyright PII SO370- 1573 (96)00043-9

@ 1997 Elsevier Science B.V. All rights reserved.

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1. Introduction It is a pleasure for me to give this summary talk [ 11. I am impressed by the tremendous amount of important experimental results presented in this Conference. Thirty years ago, when I first started working in this field, I was invited to present a ten minutes’ talk on our results of tests of QED at the Lepton-Photon Conference in Berkeley. There was then a clear separation between results from traditional proton accelerators and results from electron synchrotons. At that time, experimental groups consisted of few people. Typically, an experiment was performed in one or two years-our DESY QED experiment was done by J. Asbury, U.J. Becker, M. Rhode, A.J.S. Smith and myself in eight months’ time. Today, most of the experimental groups have 102-lo3 physicists and it takes an order of 10 years to perform an experiment. This situation makes it more and more difficult for young physicists to plan their career in our field. In order to identify the future of our field, during the preparation of this talk, I have written to Laboratory Directors to ask them to select some of the highlights from their laboratory, the future plans of their laboratory as well as their personal observations of the future of our field. My presentation consists of three chapters: highlights of recent exprimental results, future plans of different laboratories and particle physics without accelerators.

2. Highlights of recent experimental results 2.1. Tests of CPT To begin with, as presented by Professor a very accurate test of CPT in the equality of T+_ and voo, and the measurements of and Figs. 1 and 2. Therefore CPT is tested

E.A. Paschos and Professor Paolo Franzini, we now have of masses of particles and antiparticles, equality of phase the phase $+_. These results are summarized in Table 1 to an accuracy of l/lOus.

2.2. Results from IHEP Table 2 is a summary of recent results from our host Laboratory. They have provided the most accurate measurement of the mass of the tau, a good measurement of the pseudo scalar decay constant fo, and confirmed the existence of [(2230) and shown that this resonance has a very narrow width and is flavor symmetric, thus it is very likely a glueball candidate. Professor Hesheng Chen has shown (in Fig. 3) a very accurate ,u-r universality test providing G,/G, = 1.0026 f 0.0044. 2.3. Results from CESR There are very interesting results from CESR on the study of B-decays. Fig. 4 is an event picture of B” + K-r+. Table 3 summarizes some results from charmless B-decays. Measurements should soon be able to differentiate contributing processes between W emission (which dominates in B -+ zrn) and gluonic penguin (which dominates in B --+ K?r).

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Table I Tests of CPT symmetry Equality of masses for particles and antiparticles (mfl - mfl)IrnK < 3.5 x lo-‘” NA3 1 < 1.3 x lo-‘* E773 < 1.8 x lo-” CP LEAR The phases of v+_ and v,n equal &NO=~+--A~=~~-~+-=O A4 = 0.2” f 2.6” f 1.2” A4 = 0.62” * 0.7 1’ zt 0.75”( stat)

Carosi ( ‘90) NA31 Schwingerheuer et al. E773, PRL 74, 4376 (‘95)

The +sw @+@+4+-

NA31 E773 CP LEAR

phase test 4+_ = 4s~ = tan-’ (-2AM/T) = 43.37” It 0.17” =46.0” zt 2.2” zt 1.1” = 43.53” * 0.58” & 0.49”( stat) = 43.2” f 0.9;,,, zt 0.6&, f 0.7;,

Table 2 Recent BES results M, measurement

( 1994)

M, = 1776.96~~;,~,~~$ MeV G,/G,

(1) (2)

= 0.999 It 0.003

Measurement

of f~?

fo, = (4.3+‘r~J~\~) x 10’ MeV

(3)

B(Ds + eX) = ( lO.O~~~+_‘i~~) %

(4)

Confirm the existence of &(2230) & Found two new decay modes: [( 2230) + 7rt rr-

(5)

02230) + PP (likely to be a gluebal candidate)

(6)

Find new anomalous

suppression

Br($’

-+ prr) < 3.6 x 10e5

Br($’

---f K*K)

Table 3 Charmless

B-decays

< 2.4

x

in vector and tensor decay of t/Q’: (7)

10m5

(8)

= 1.8~‘:;~~~\0;:x 10e5

CLEO

Br( B” + h-r’)

ALEPH

Br( B” + rrfK

DELPHI

Br(Ab + pK) < 3.0

L3

Br(B$ + n-“rr’) < 7.6

) < 4.6 x lo-’ x

90% C.L.

low4 90% CL. x

lop5 90% C.L.

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PDG 94

CP LEAR 95 E773

95

E731

93

CP LEAR 95

-8-

E773

95

E731

93

CP LEAR 92 Geweninger

Gjesdal

74

74

Carithers 75 Geweninger

40

42

44

46

48

50

52

-

74

!1

0.52

Cullen 70

I

I

I

I

0.53

0.54

0.55

0.56

cp+-(“)

Am (1010 R/s) Fig. 1. The measurement

Fig. 2. Measurement

of $+-.

of Am = rnq - m$.

CleoXD Run: 42644

310

290

205

9 I

I

I

17.5

18

18.5

BR (7 + eve VT), % Fig. 3. p-7 universality Fig. 4. B” + K-z-+

test.

candidate.

Event: 1000

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Table 4 CLEO observation

of electromagnetic

Reports 279 (1997) 203-250

“penguin” process

Exclusive decay channel: Br( B” + K*‘y = (4.3t’i:, f 0.6) Combined

X

10e5

with inclusive result:

T(B-+K*y)/T(b--tsy)

=0.19&0.07f0.004

“y” +

charm production, baryon production,

“y” -3

loo

3

4

5

6

7

6

PT WV) Fig. 5. y + y -+ charm production,

CLEO has also provided a clear observation results summarized in Table 4.

baryon production

and jet production.

of the electromagnetic

“penguin”

process

with the

2.4. Results from TRISTAN We have very interesting results from the TRISTAN e+e- collider, particularly on y + y -+ charm production, baryon production and jet production, as shown in Fig. 5. The TRISTAN results established “resolved-photon” processes and selected “gluon-density” parametrizations. Another very interesting and important result from TRISTAN is the high-Q2 measurement of the photon structure function Fl by the AMY Collaboration as shown in Fig. 6. The Q2 dependence clearly shows the scale-breaking behaviour predicted by QCD. At the TRISTAN 12 GeV proton synchrotron, there is a very precise ,uSR study of mononergetic ,U’Sfrom K+ + pv at rest, as shown in Fig. 7. This experiment provides a very accurate measurement of ,$Pcl = -0.9996 f 0.0030 f 0.0048. This sets a new limit on the “right-handed” current. 2.5. Results from BNL At Brookhaven National Laboratory in Long Island, there is continued impressive progress in the study of rare K decays. Professor S. Wojcicki presented the recent progress on the study of KE decay to lepton pairs. This is shown in Table 5. It is important to note that in a very short time, the electron

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ci5, bb subtracted --.-

P+O.l

-

qo=o.50

- - - qo4.0 -_0

FyD/a

I

This Experiment

lo4

i!

lo3

.Ei 102 10 ,

10 lo’

Q2

(GeV2)

0

lo2

16

Fig. 6. High-Q* measurement of the photon structure function Fl by the AMY Collaboration. Fig. 7. pSR study of mono-energetic p’s from K+ + ,uv at rest.

Table 5 Recent progress at BNL on @Ldecay to lepton pairsa BNL rare decays E791 (1989-1991)

K’L-+ p*e* K’L+ e+eK’; -+ pu+/L-

< 3.3 x lo-” (90% CL.) < 4.1 x lo-” (90% CL.) N 700 evts observed

E87 1 (expected, 1995- 1997) N 10-12 -_10-‘2

-10000 evts expected (-4000 on tape already)

a From S. Wojcicki.

Table 6 Recent progress in rare K+decays at BNL E79 1 [ Littenberg] . Rare Kf decays at rest: - first observation of K’ -+ n=‘p”+pL-, Kt -+ r+YY - new lower limits on K+ 4 ~+YV [measures 1L& in SM] - other exotic decay searches, e.g., K+ -+ n-+x0 ES65 [Zeller] . Rare Kt decays in flight: - search for Kt + r’pue [ lepton flavor violation] - first observation of K’ -+ rr’e’e- other exotic decay searches, e.g., K+ + vr+p

channel will reach the limit of - lo-l2 and there are already 4000 events on the pure muon channel. Table 6 summarizes the recent progress in rare K+ decays both at rest and in flight.

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0 60%- gwww?w\ 32 : 3 W 6 5

40%

-

L '2

P m

.g 2

Strained Lattice Cathode for 1994 SLD Run

&&ii

Strained Lattice Cathode for 1994 SLD Run

20%

t?

O%J”“““.““‘~““““‘...‘..~‘~ 0

40,000

60,000

120,000

160,000

Z Count Fig. 8. Beam polarization, SLD 1992-I 995 data.

I

’

I

I

I

I

s A,J, for Z Bosons

l-

Luminositv Bhabha Asvmmetrv

-I

0.00

I

I

1

I

I

I

I

0

20,000

40,000

60,000

80,000

100,000

2 Number

Fig. 9. ALR and luminosity 2.6.

Bhabha asymmetries

in data blocks.

Fom SLAC

At the SLAC linear collider, there is a great achievement in the polarization of the electron beam from the original value of 20% to almost the theoretical limit of 80% as shown in Fig. 8. Fig. 9 shows the measurement of the left-right asymmetry at the 2’ pole which is typically 15% as compared to no asymmetry in Bhabha scattering. Fig. 10 shows the polarized Z --+ b& asymmetry using jet charge to define the charge of the b-quark. The angle & is between the thrust axis of the b-jet and the polarized incident electron beam. Table 7 summarizes the impressive SLD results which provided sin2 & = 0.2305 f 0.0005. In addition to the SLD results, SLAC also provided important information from the study of

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/Jb

e-/R

e+

6 600,

100

I

I

I

I

I

I

I

I

I

I

1

ISLD Preliminary

0 -1.0

I

0.0

-1.0

I 0.0

I 1.0

co68T

Fig. IO. Polarized Table 7 Summary of SLD results on measurements

of electroweak

Z + b& asymmetry.

parameters

1.

Measurement of ALR. 1992, 93, 94195 data combined ALR = 0.155 1 f 0.0040 + sin* & = 0.2305 f 0.0005

2.

Polarized forward-backward asymmetry for b and c quarks A, = 0.57 * 0.10, A/, = 0.861 f 0.053

scattering of polarized muons from polarized protons to measure the spin-dependent structure function d. Professor Vernon Hughes who originated this study from the original Yale-SLAC Collaboration in 1983, has presented impressive results shown in Fig. Il. 2.7. Results .from LEP At LEP-I, the four experimental groups (ALEPH, DELPHI, L3 and OPAL) have collected a total of 20 x lo6 Z” providing a variety of precision tests of electroweak theory. Typical results from the four groups are the following: 2.7.1. From the ALEPH Collaboration Fig. 12 shows the precise measurement of b lifetimes. The exclusive measurements show that the b-baryon decays faster than the b-meson, as expected. The inclusive measurement yields an average b lifetime of 1.533 f 0.026 ps. Fig. 13 shows the quality of the data in the measurement of b-baryon lifetime by the ALEPH Collaboration as a clear signal with a very small combinatorial background.

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2.5

Yale-SLAC (1983) 2

3P 1.5 1 1 0.5 0 -0.5

Fig. 11. $I as function of X measuredover the last 10 years.

100

I

I

1

I

I

I

I

ALEPH 80 T r ZI ‘C E

40

U 20

,”

60 0 i -4

’

*(ps)

Proper Time (ps)

2

Fig. 12. b-lifetimes measured by the ALEPH Collaboration. Fig. 13. Measurement

of b-baryon lifetime.

Professor S.L. Wu showed the important ALEPH study of B”--B” oscillation by measuring the rate of same sign dileptons normalized to the total dilepton rate. As seen from Fig. 14, this provides a clear measurement of Bj: oscillation with small contribution from B,, b --t c and other backgrounds. The ALEPH measurements yield a Amd = 0.430 & 0.032 f 0.071 ps-‘. 2.7.2. From the DELPHI Collaboration The DELPHI group has a very good particle identification capability. Fig. 15 shows the clear separation of various particles by the gas RICH, the liquid RICH and the dE/dX of the central drift chamber. The DELPHI Collaboration provided a very interesting study of the fragmentation function for b-hadrons, B*-mesons and B**-mesons, as shown in Fig. 16.

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Reports 279 (1997) 203-250

5 0 Proper time (ps)

213

10

Fig. 14. ALEPH measurement of B”-B” oscillation as a function of proper time.

Fig. 15. DELPHl particle identification capability (horizonthal axis: p in GeV).

From the OPAL Collaboration OPAL has also provided important results on electroweak physics with heavy flavours. Fig. 17 shows the measurement of the forward-backward asymmetry of b. The results are summarized in Table 8. As seen from Table 8, OPAL obtained an Rb = 0.2197 f 0.0014 f 0.0022. Fig. 18 summarizes the OPAL measurement of b hadron lifetimes, again indicating that the b-baryon decays faster than the b-meson. 2.7.3.

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DELPHI 1.2 w

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4.1

b - hadrons

1-

3

B* - mesons \

G 0.8 u $ d 0.6 .

B** - mesons

1

•I

0.4

t

r 0.2

0 w

0.2

0.4

0.6

0.8

XE

!!I

Fig. 16. DEPHI measurement

1

of fragmentation

Fig. 17. OPAL measurement Table 8 Summary of electroweak

43 (GeW

function for b-hadrons and B-mesons.

of forward-backward

asymmetry

of b.

results from OPAL

OPAL” jet charge A’;B 4

r-~ sin* 0$”

= 0.2313 5 0.0012 * 0.0006

Fraction of Z” + bb events in hadronic Z” decays:h

RI, =

r (‘” + ‘&) F ( Z” + hadrons)

= 0.2 I97 zt 0.0014 + 0.0022

Fraction of Z” ---t CC events in hadronic Z” decays:’

R, =

l- z” + ci’ ) f (Z” + hadrons)

= 0. I525 f 0.006 1 f 0.0095

a OPAL Collaboration [ 21. hOPAL 1991- 1994 data. ’ Average of 3 OPAL measurements.

Fig. 19 is another important OPAL result, showing the evidence states were observed: 03 and DI. 2.7.4. From the L3 Collaboration Professor Hesheng Chen showed the L3 measurement

of B decays to D** (Dj).

of tau polarization

asymmetry

Two

(Fig. 20))

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215

1.523t0.034+0.038

1S3tO.I 2tO.00 1.52d.I 4tQ.09

1.16+O.lliO.O6

z (PS)

Am (GeV) Fig. 18. Summary of b hadron lifetimes from OPAL. Fig. 19. Evidence 0.1

for semileptonic

L3""""'

B decays to D** (0, ).

AT = 0.152&0.010?0.009

_

A, = 0.156+0.016&0.005 Ol

A,,

= 0.163M.009&0.006

-

-0.3 -

No Universality

- - _ Universality -0.4,

’ ’ -0.8

’

-0.4

’

’

’

’

0.4

’

’

0.6

C&3)

Fig. 20. Tau polarization

asymmetry

measurement

by the L3 Collaboration.

giving a sin2 0 w = 0.2308 & 0.0013. The L3 Collaboration studied the production of tensor mesons from 2-photon processes, via the reaction e+e- + e+e-y*y* + e+e-@Ki (see Fig. 21). The mixing angle of the tensor nonet is determined to be 8 = (29.4?‘,*,)“. As seen from Fig. 21, in addition to the &( 1525), there is an indication of another ee state at a mass of N 1800 MeV. The L3 Collaboration also studied the difference between 77 production in the quark and gluon jets. Historically, gluon jets were first observed in 1979 by the MARK-J experiment with major contributions from H. Newman, M. Chen, J. Branson and from Chinese physicists (H.W. Tang, Z.P. Zheng, Z.Q. Yu, H.S. Chen and others). Fig. 22 is a reproduction of the first statistically significant evidence that the 3-jet events cannot only come from fluctuations in fragmentation from heavy quark decays. The MARK-J experiment showed that (a) the 3-jet rate agreed with QCD, (b) the shape agreed with QCD. At LEP energies, the jets are much more collimated, as shown in Fig. 23. Also shown are the yy mass spectra from the two highest energy jets (jet 1 and jet 2), as well as from the gluon jet, jet 3.

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203-250

600 500 % I a z 3 c P

400 300

W

200 1w

_ Of

0.4

0.5

Fig. 21. Production

0.7

0.6

X+JK-

mass

0.8

0.9

K ZK i

of tensor mesons by the L3 Collaboration

5

from the reaction:

e+e-

mass (GeV) +

e’ e-y’y’

+

e’e-K(s’Kt.

2* Shape agrees with QCD

10 Rate agrees with QCD 1 I , 1 10

2.0

1.5

(GeV)

27.4 + 30 + 31.6 GeV

$1.0

-12 G

0.1

= 425 Me”._--+, I

Fig. 22. Discovery

I 0.2

oa \

of gluon jets by the MARK-J

0.4

experiment

in 1979 as reproduced

in Ref.

[ 3 1 (see also Ref. [ 4) ).

Fig. 24 shows that for # production, the momentum distribution for all 3 jets are well explained by QCD and fragmentation implemented in Monte Carlo programs. But for 7 production, the momentum distribution of the third jet, at large X,,, cannot be explained by Monte Carlo. This may indicate a possible existence of glueball effects which are not included in the current 7 production Monte Carlo. 2.7.5. Summary of LEP-I results (i) Mz: the mass of Z”. Fig. 25 summarizes the LEP measurements of the mass of Z from the four LEP groups. The average mass from the four groups is Mz = 91188.4% 2.2 MeV The 2.2 MeV error includes a common error of 1.5 MeV and the combined statistical error of 1.6 MeV from the four groups. (ii) Fz: the total width of Z”. Fig. 26 summarizes the LEP measurements of the total width of Z from the four LEP groups, providing an average width of Fz = 2496.3 f 3.2 MeV. Also shown in Fig. 26 is the Standard Model calculation of Fz as function of the mass of the top quark, M,, the

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217

1979 Mark-J

Thrus 0.5s

M w (GeV)

Fig. 23. Measurement

I

0

of 71 production

olos x,

0.06

0.08

0.1

of no

Fig. 24. Momentum

0

o,w Mw

0.9 GW

in quark jet and gluon jet.

lo-’ 0.02

0.9

I

0.05

0.1

0.15

I

0.2

0.25

3

xp ofq distribution

of n-” and 77 production

in jets.

mass of the Higgs, M H, and a,, the constraint on M, from the measurement of Mz. (iii) rinr.: the invisible width, and N,: the number ofneutrino species. Fig. 27 summarizes the LEP measurements of the invisible width of Z from the four LEP groups, providing an average r,,,,, = 499.9 f 2.5 MeV. In the framework of the Standard Model, this value of r,,,,. determines the number of neutrino species N,, = 2.990 f 0.016. Also shown in Fig. 27 is the Standard Model calculation of rinl,. (iv) The direct measurement of the number of neutrino species N,. The number of neutrino species can also be directly determined by measuring the single photon reaction e+ + e- ----fv~y. Fig. 28 shows the results from the L3 Collaboration giving an N, = 3.01 f 0.09 f 0.08. Table 9 summarizes the results from ALEPH, L3 and OPAL experiments. (v) The determination of sin2 &. Fig. 29 summarizes the LEP determination of sin’ BW from

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Total width r, 2 495.1 f 5.6 MeV 2 4913 f 5.4 MeV 2 502.2 f 5.4 MeV 2 495.9 f 5.3 MeV

Z Mass ALEPH DELPHI

U

--+-

91184.6 f 3.5 MeV Yb

II II

&d

I 1

= 6.9t3

2480

91200

Fig. 25. The measurement Fig. 26. The measurement

Table 9 Summary of direct determination

57.3 15.7 40.5

M,=60-1OOOGeV

n

as = 0.123 f 0.006

(pb-‘)

u9a

2500

r, WeVl

WV1

&Cdt

#

notcorn 1.6MeV

91190 &

Mz=91188f2MeV

ecmun~n 1.5MeV

I I

I r 91180

91188.4 f 2.2 MeV

II II

I I

combined

notcorn 2.5MeV

91 193.8 f 3.6 MeV

-A-

LEP

L3 ALEPH OPAL

common2.0MeV

91184.9 f 3.4 MeV

L3 OPAL

2 496.3 k 3.2 MeV

91 192.4 f 3.7 MeV

of Z” mass from four LEP groups.

of Tz, the total width Z”, from the four LEP groups.

of N,, from ALEPH, OPAL and L3 rinv (MeV)

N”

503f 15zt 13 450f34Yt 34 539f26xk 17

3.01 It 0.09 f 0.08 2.68 zt 0.20 * 0.20 3.23 i 0.16 it 0.10

507 + 16

3.03 f 0.10

forward-backward asymmetry of leptons, A FB lepton, from average tau polarization and forwardbackward polarization asymmetry, A,, A,, from forward-backward asymmetry of b- and c-quarks, AFB b-quark, AFB c-quark. These measurements yield an average LEP value of sin’ & = 0.23 18 5 0.0004. Combined with the SLAC value of sin2 6’W = 0.2305 f 0.0005, the average value is 0.2314 f 0.0003. Also shown in Fig. 29 is the Standard Model calculation of sin* 19~ and the constraints on M, from these measurements.

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.

Invisible width Fin, ALEPH

499.6 f 3.6 MeV

DELPHI

504.0 f 4.1 MeV

L3

500.3 f 4.4 MeV

OPAL

498.0 f 4.1 MeV

LEP

499.9 f 2.5 MeV wmm~n 1.8 MeV not corn

n

1992 data (corrected)

l

1993 data (corrected)

1.8 MeV

r,, WV1

4s [GeV] Fig. 27. Measurement of rin” from the four LEP groups.

Fig. 28. Direct measurement of the number of neutrino species N, from the L3 Collaboration. Also shown is the energy and angular region of y measurement for this experiment.

2.7.6. Comments on LEP-I results (i) Determination of the top muss, M,. In addition to the measurements at LEP and SLD, the beautiful measurements of Y scatttering on electrons by CHARM II provide an accurate determination of & = -0.503 f O.O06(st) as shown in Fig. 30. Table 10 summarizes the determination of M,, cy, from LEP data alone, LEP data plus SLD and finally from all information including ~JN data and the direct measurement of MW. As seen, the fitted value value of M, shown in the first row of Table 10 agrees with the direct measurements by CDF and DO of M , = 1804~ 12 GeV. (ii) Consistency of electroweak theory. The Standard Model seems to be able to explain all available data over a wide energy region. As an example, Fig. 3 1 shows the comparison of e+ + e- -+ p+ + ,L- + y from PEP, PETRA, TRISTAN and LEP demonstrating excellent agreement of the data with the Standard Model. (iii) The measurement of Rb and R,. The only possible deviation between the data and the Standard Model arises from the measurement of Rb = rb/I’had and R, = rc/lYhod. Fig. 32 shows the comparison with the Standard Model predictions and the LEP average values of Rb and R,. As seen, the LEP average values of Rb and R, deviate from the Standard Model prediction by three standard deviations. Obviously, more measurements are necessary to ascertain the origin of this deviation.

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0.2310 * 0.0007 0.2322 f 0.0010 0.2325 f 0.0011 0.2321+ 0.0006

average LEP

0.2318 f 0.0013

0.8 -

0.2318 ?: 0.0004

0.6 -

0.2305 f 0.0005

0.4 -

A,, (e+e- -+ e+e-) -

0.2314 f 0.0003

X%/do f = l.US

0.228 0.23

M,= 91 188 f 2 MeV

-0.4 -

H

M,= 60 - 1000 GeV

-0.6 -

0

cx-’ = 128.90 10.09

-0.8 -

--

-

I

-1 .o 0.232 0.234

-0.8

I

I

sin’ A..

I

I

0

I

I

0.4

I 0.8

gv

Fig. 29. The determination Fig. 30. CHARM II determination at Z” is also shown.

I

-0.4

of sin’ HW from the four LEP collaborations

of &, and &. The measurement

of the forward-backward

and SLD. asymmetry

AFB(e+e- ----t efe-)

Table IO Summary of fitted results of M, and (Y, from LEP data and L.EP + SLD and finally from all available data. The last three rows are the consequence of the fitted M, and (Y, LEP

LEP + SLD

LEP + SLD + MW and vN data

M, (GeV)

170 + lo”:,

l8O+x +17

178 f S’;,

a.,(Mi)

0.125 f 0.004 f 0.002

0.123 & 0.004 zt 0.002

0.123 zt 0.004 zt 0.002

,$/d.o.f.

18/9

28/12

28/14

sin’ 0:;;

0.23206 f O.O0028t_‘;,;;;;~,

0.23 166 f 0.00025:;;j;l;;FJ

0.23 172 III O.O0024+_‘~j~~~~~

I-M;/M:

0.2247f O.OOIO+'~~'xx" --0.0(X)2 80.295 f 0.057:;';;g

0.2234f0.0009:;;~~; 80.359 * 0.051:,$:4

0.2237 + 0.0009+"~'xxM -o.(xx)2 80.346 zt0.04611':!$,

MW

(GeW

-‘l-211

2.7.7. Comments on the LEP-II program In November of this year, LEP will reach a center of mass energy of 140 GeV. It is intended to have a data sample of 5 pb-’ total luminosity. The machine energy will gradually increase to a final energy of - 193 GeV. Table 11 summarizes the current plan of LEP-II up to 1999. LEP-II

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TRISTAN LEP OCELLO

n VENUS

AMARKJ

r AMV

0.5 MARKS

l L3

1

OCELLO

aVENUS

AMARKJ

.AMY

l L3

B S

as +zi .I

a; +*

0

-1

?'O +s

3 3 b

$

-0.5

40

60 4s

Fig. 31. Comparison Born predictions

of the measured

60

100

20

40 4s

[GeV] forward-backward

asymmetry

60 [GeV]

60

AFLY, and total cross-section,

100

(T, to the lowest order

0.16

Pi7

0.16 a” 0.15

CO8

0.4

_.. II

0.2 x”

:.

0

..*

-0.2 -0.4

0.214

0.218

0.222

cost+,cl! cosl9, et, 1ej

0.226

%

Fig. 32. Comparison

of the Standard Model prediction

Fig. 33. Limits on anomalous couplings

(SM) of R/, and R, with the LEP average value

with s Ldt = 500 pb-’

in the reaction e+e-

---$ W.+W-.

will provide an important opportunity to search for new particles and additional tests of the Standard Model. Fig. 33 shows the sensitivity in the tests of the Standard Model characterized by the measurement of the deviation of the magnetic moment of W’ (puw)

pw=

&Cl

+&+A,). W

Note that in the Standard Model KY = 1, A, = 0, X, = KY - 1, X, = 0. As seen from Fig. 33, in the reaction e+e- -+ W+ W-, the measurement of the W* direction cos 6, the leptonic decay direction, 13~and the hadronic jet direction, lejl, provide very accurate constraints

I

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Table 11 LEP-II program l

November 1995 fi Z 140 GeV - Test of machine and detectors - Search for new particles up to M N 70 GeV

Total luminosity

5 pbb’

l

May 1996 fig 161 GeV - W mass measurement at threshold AMw N 100 MeV - Search for new particles up to M % 80 GeV

Total luminosity

50 pbb’

l

October 1996 fir 175 GeV - Search for Higgs boson up to MH = 80 GeV - Search for new particles up to M = 87 GeV

Total luminosity

30 pb-’

0

1997-1999 fig 183-193 GeV - W mass measurement AMw z 80 MeV - Study of the three gauge boson couplings - Search for Higs boson up to MH = 100 GeV - Search for new particles up to M = 95 GeV

Luminosity

-h

us

=

150 pbb’/year W+ W-

192 GeV

200

4 flO0

60

70

80

90

100

110

120

M, (GeVk?) Fig. 34. Standard Model Higgs search.

on the deviation of the magnetic moment. Fig. 34 provides an example of sensitivities for the 50 discovery limit and the 95% CL exclusion zone for the Standard Model Higgs as function of center of mass energy and luminosity. As seen from Fig. 34, near the end of 1999, one should be able to

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CDF Preliminary

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--I

200

300

Reconstructed Mass (GeV/cZ)

Top Maan (GeV/c2)

Fig. 35. CDF top results based on leptonic decay channels. provide information

on the existence

of the Higgs up to a mass of 100 GeV.

2.8. Results from Fermi National Laboratory The most important physics results over the last two years are the discovery of the top quark, the measurement of the mass of the top M, quark and the measurement of Mw. Fig. 35 summarizes the CDF top results from leptonic decay channels. CDF determined the mass of top quark M, = 176 f 8 (stat) f 10 (sys) GeV/c’ and the production cross-section (T,~(M, = 176 GeV/c*) = 7.6’_2, pb. The DO Collaboration also found the top quark signal. They determined M, = 199% 1_:4GeV and cti( M, = 199 GeV/c*) = 6.4 & 2.2 pb. Fig. 36 shows the CDF top quark results from pure hadronic decay channels. It is important to note that the leptonic and hadronic channels yield a consistent result. Fig. 37 is the determination of the W mass by the CDF Collaboration from both W + ev and W -+ pv. These two measurements yield a determination of M w = 80.41 f 0.18 GeV. The data is based on a total luminosity of 19 pb-‘. In the framework of the Standard Model, the determination of Mw and M, provides a constraint of the mass of the Higgs as shown in Fig. 38. The width of W was measured in two ways: (i) Indirect measurement from crwBr( f?v) /azBr( et). This yields

(ii)

Iw = 2.06 f 0.09 GeV

(ev) ,

Tw = 1.80 f 0.11 GeV

(,uv)

Direct measurement TW =2.ll’f0.32

preliminary.

from fitting the A47 distribution. GeV

These numbers are in good agreement

This yields

(ev). with the Standard Model prediction

of Tw = 2.07 f 0.02 GeV.

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Lifetime of Tagged B’s

W -+ JJ Dijet mass of untagged jets In events with a b tag and a second loose tag

CDF Preliminary

(100

pb-1)

3 eight wenW in pea Mean81.4 t 3.2 Gev

For the

Sigma 9.1 + 6.0 GeV

errorsstatisticalonly

0

-0.1 cx

Invariant

0.1

of tagged jets (cm.)

mass of the two untagged jets

Sea;Eh for fi -+ 6 jets (All hadronic Decay) I

I ’

I

1 Shaded:

1

I

Background

20 N * > Q) 15 (3

z E

10

5

0 100

150

200

mfit

250

300

(GeVk2)

Reconstructed Mass Fig. 36. CDF top results

based

on pure hadronic decay channels.

Both the CDF and the DO Collaboration have provided good tests of the Standard Model, by studying wW~/wWZ couplings. Fig. 39 is the observation of the asymmetry in y rapidity by the CDF Collaboration. The measured asymmetry of 0.77 f 0.07 is in good agreement with the Standard Model prediction of 0.76 k 0.04. Fig. 40 is the combined limit by CDF and DO on the anomalous magnetic moment of W showing excellent agreement with the Standard Model. Finally, the available high center of mass energy provides an excellent opportunity to search for

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120

fl(GeV/&

Mtop(~V/e2)

Fig. 37. Determination of W mass by the CDF Collaboration. Mt;” = 80.3 IO f 0.205( stat) * 0.130( syst) GeV.

Mr

= 80.490 !E O.l45(stat) k 0.175(syst)

GeV,

Fig. 38. Limits on Higgs mass from measurement of MW and M f,,Pas determined by the CDF Collaboration. I

,

95%

I

C.L. limits I 1 I I

I

I

I

, 4

cn24r; P W168preliminary

-4-

I I I -4 -2

I

0

Char&3gnedoPhoton

F&i&y

I

I

I

Arc7: At?

, 2

Fig. 39. Observation of asymmetry in ~]y from p + p --) WY + X. Fig. 40. Limits on anomalous magnetic moment of W new

particles.

Table 12 summarizes

the results of CDF exotic particle searches as well as their future

prospects, 2.9. Results from HERA The luminosity at HERA has increased rapidly over the experiments, ZEUS and Hl each expect lo-15 pbb’ in 1995 Fig. 42 shows the measured total y*p cross section as a squared W. The data for Q* = 0 shows a moderate rise with

years as shown in Fig. 41. The two and 20-40 pb-’ in 1996. function of the center of mass energy increasing W, while data with Q2 > I

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6

1

0

125

175

225 275 Days since Jan 1 rst

325

Fig. 41. HERA luminosity from 1992 to 1995.

m*:

w/i&#

Fig. 42. Measured total y*p cross section as a function of the center of mass energy squared W. The curves, connecting points of the same Q* value, are given to guide the eye.

S.C.C. Ting/Physics Table 12 CDF exotic particle searches:

Reports 279 (1997) 203-250

results and run II prospects

Searches

Current CDF limit (GeV), excluded region at 95% C.L.

Data set

W’ + ev (SM) w’ + wz z’ + ee (SM)

< 652 205 < M < 400 < 650 < 415,440,425,400 < 445,420 200
la (20 pb-‘) a la+ lb (70 pb-‘) la+ lb (70 pbb’) la (20 pbb’)’ la (20 pbb’) A la+ lb (70pb-‘)’ la+ lb (70pb-‘)” la + lb (70 pb-‘) la+ lb (70 pb-‘) la+ lb (70 pb-‘) la (20 pbb’) a la (20 pbb’) ’ la (20 pbb’) a la + lb (70 pb-‘) la+ lb (70 pbb’) ‘88-89 (4 pb-‘) a la (20 pbb’)’ la+ lb (70 pbb’)’ ‘88-89 (4 pb-‘) a la (20 pbb’)’ la (20 pb-‘)’ la (20 pb-‘)’

q,

zq, zx, ZI

ZLR

> ZALRM

axigluon -+ qq techniro + dijet W’ + 99 (SW Z’ + 99 (SW & diquark -+ qq topgluon r = O.lM topgluon r = 0.3M topgluon r = OSM leptoquark (pq) composit. scale (qqqq) composit. scale cqqee) q*(W+jet,y+jet) q* + dijet massive stable pd. gluino squark gaugino

221

Run II (GeV) with 2 fl-’

< 990 a a

< 900

h h a

< 800 < 800 < 1160 200 < M 200 < M 290 < M 200 < M

a a

< < < < < <

< < < <

770 720 720 570

300 2200 5000 820 820 350, < 520

a Current world best limit in direct search mode for the model. h CDF has the world best limit in another decay mode. ’ Same as (a), but DO also has comparable limits.

GeV* (- deep inelastic scattering) show a strong rise with increasing W. Both HERA groups have provided a direct measurement of the gluon structure function. The results agree with each other and with the muon fixed target experiment NMC (results of indirect methods). This is shown in Fig. 43. The HERA groups have also studied photoproduction of vector mesons p and 4 by virtual photons. This is shown in Fig. 44. A fit of the p and 4 production cross sections to a power law W" shows that: (a) For Q* = 0, p production and phi production vary slowly with increasing W. The production of 4 agrees with vector dominance model (VDM) predictions, with a power law exponent IZ in the range 0.2-0.3. (b) For Q* > few GeV*, both p production and 4 production follow the curve W().8.This steep rise is in clear disagreement with VDM predictions. The HERA groups also provided a very important measurement of (Y,. This is shown in Fig. 45. The HERA measurements of as, when evolved tot the scale Q* = M& agree well with the world average of cy, ( MZ) = 0.117, as well as the LEP average, within errors. As was presented in this conference, HERA has also provided very large amounts of data at very

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““‘.’

Hl

.

Hl direct Hl dFddln(Q*)(Prytz) Hi QCD fit NMC (J/y) ZEUS dFddln(Q*)(Prytz

25

GRV CTEQ3L

Fig. 43. Comparison of various methods to measure the gluon density at leading order. A novelty (in DIS) is the measurement of boson gluon fusion events, from a sample of 2-jet events. This result is given at an average Q* of 30 GeV*. Furthermore, indirect measurements (from scaling violations of Fz) are shown at Q* = 20 GeV* as well as with a determination from .l/$ production by NMC evolved to Q* = 30 GeVz.

.

mm0.55

+Hl

3

Tr

:

q

ZEUS 94

A NMC 44

4

4 1.6

+ 2.6

:%

: -

z

0 IO-2r

r

-

t 10’2r

WQ.8

_

b103r

1

Fig. 44. Cross sections for exclusive p and 4 production in deep inelastic scattering: y*p + pp, y*p + qSp, as function of W, the y*p center of mass energy, for several values of Q*. The low energy data (W < 20 GeV) come from tixed target experiments. The high energy data ( W > 50 GeV) come from the ZEUS and Hl experiments. The ZEUS data on p production have for Q* > 5 GeV an additional 31% systematic normalization uncertainty (not shown).

low X down to 4 x 10e5 and high Q2 (to 5000 GeV2). It is the ideal place for studying the interplay between soft and hard processes. As seen from Fig. 41, with increase in luminosity, we expect a tremendous amount of physics from HERA.

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1 q

Hl

n

ZEUS

0.20

I

d 0.15

0.10 HERA fit t lo as (f+) = 0.120t0.005r0.007 0.05

0.00

PDG a* (MZ) = 0.117*0.005

10

Q [GeV]

100

Fig. 45. The measured value of (Y, from the rate of 2-jet events as a function of Q2. The line represents results of Hl and ZEUS.

the combined

3. Future plans In this Chapter I summarize the future plans at high energy physics laboratories vations on the future field from laboratory directors.

and some obser-

3.1. In Italy: INFN Frascati Laboratory The Frascati Laboratory is presently engaged in the construction of the DAQNE e+e-- phi-factory = 10j3/cm2 s) with two detectors, one of which is KLOE under Paolo Franzini’s leadership, as shown in Fig. 46. (L

3.2. In China: the tau-charm factory Our host IHEP in Beijing is planning a tau-charm factory as a logical extension of their successful BEPC project. A tau-charm factory with a luminosity of 103’/cm2 s and energy range of 3-6 GeV will offer a unique opportunity for precision measurements in the tau-charm energy range. Its physics cannot be replaced by other facilities and complements B-factory physics. Table 13 summarizes some of the physics potential of a tau-charm factory. As pointed out by Professor T.D. Lee, the tau-charm factory offers a unique opportunity to study CP and T violation in lepton systems.

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LINAC 550 MeV e+

800 MeVe-

rr t

TEST BEAM

CCUMULATOR 510 MeV

Fig. 46. The Frascati @factory. Table 13 Tau-charm factory physics 0

Unique experimental environment: 0 High statistics: 30-50M r/c yr-’ IO’“-IO” J/$ yr-’ 0 Low backgrounds: D T production below c/b threshold D tagged charm hadrons 0 bgds. exp. measured < threshold 0 high rate calibration sources: J/I++,+’

l

Physics highlights: 0 direct m(v,) limit N I MeV 0 V - A in T decays c preen. in f.~ decay 0 CP violation in r decays to N 0.1% 0 D/OS ---ff_w/rv; fo / fos N 2% precision 0 Do/D” mixing - 10p5, at SM level 0 CP violation in D decays at SM level 0 systematic study of gluonic matter

3.3. In the US 3.3.1. At Cornell University At Cornell, there is a vigorous plan (as shown in Fig. 47) to upgrade the highly successful CESR to a much higher luminosity. The goal of CESR is to reach a luminosity much above 1033/cm2 s. This will offer a unique opportunity to study B-physics. 3.3.2. At Brookhuven National Laboratory Professor Nicholas Samios shares with us the future plans of Brookhaven National Laboratory. Table 14 shows the near term future plans of BNL both at AGS and at RHIC. Of great interest are: (i) the continued study of rare kaon decay, (ii) the definitive gluon exotics search, (iii) the search

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E

231

I

“Goals”

Lx?!,:......

:............................................

;........................&.$!?e?~~.... A..........; ...............................................+3,3xIQ!?..: 7 Bunch

1.0

I++

lo-‘I 1900

1995

1990

1995

2000

Year

Fig. 47. CESR luminosity

Table 14 Near-term

future plans for Brookhaven

upgrade plan.

National Laboratory

Alternating Gradient Synchrotron ( AGS) - seek full utilization of the AGS facility (25 weeks/yr for p’s + 12 weeks/yr - continue upgrades of intensity (now 6 x 10h ppp) - develop beam injection for RHIC (Au and polarized p’s) _ run p production and cooling studies for a /.,+ collider

for Au ions)

RHIC project - complete and commission the RHIC collider - complete 4 baseline heavy-ion detectors STAR, PHENIX, PHOBOS, BRAHMS - complete the RHIC Computing Facility at BNL - commence work on the AEE items for detectors Physics goals _ continue accumulating rare kaon decay events _ complete a definitive gluon/exotics search _ confirm or deny the existence of strangelets

- measure muon (g-2) to 0.3 ppm _ map the transparancy of nuclei for elastic scattering

for strangelets, (iv) the precision measurement of muons (g-2) to 0.3 ppm. Table 15 presents the long-term plan of Brookhaven National Laboratory. Of particular interest is the plan to construct a /_L+,c collider up to a maximum energy of 2 TeV x 2 TeV and with a luminosity larger than 1034/cm2 s. Professor Samios offered his views on the future of high energy physics, reproduced in Table 16, pointing out the need to continue vigorous research with present facilities as well as the need for higher energy and higher intensity complementary colliders.

232 Table I5 Brookhaven

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long-term plans

Program goals _ RHIC heavy ion physics program - 37 weeks/yr - RHIC polarized proton experiments - up to 10 weeks/yr _ other AGS experiments as approved - pursue relevant P/_L collider (if approved) Physics goals _ explore the heavy ion physics of RHIC quark-gluon plasma disordered chiral condensate boson correlation functions mesom mass and width shifts new phenomena... _ explore the physics of polarized protons in RHIC gluon structure functions AC(x) quark spin structure functions Ay(x) transversity structure functions hl( x) search for quark substructure via jet pi shape, other spin physics... _ continue AGS physics as the held develops neutrino oscillation parameters exotic meson states strangelet physics? gluino related states s’? other physics not yet identified...

3.3.3. At Fermi National Laboratory Fermi National Laboratory currently has the highest energy hadron collider and has provided us with truly exciting new results. Dr. John Peoples has presented us his very interesting plans on the future of Fermi National Laboratory, as reproduced in Tables 17 and 18.

3.3.4. At SLAC Professor Burton Richter has provided us with SLAC’s long-range program as summarized in Table 19. Of great importance is the construction at SLAC of the B-factory with physics scheduled to begin in 1999. The BABAR physics collaboration has an excellent detector with major contributions from the United States, from CERN member states and other countries. SLAC is also vigorously planning to realize the Next Linear Collider (NLC) with initial energy of 500 GeV and luminosity of 5 x 1033/cm2 s, with expansion capability to 1.5 TeV. Table 20 summarizes the plans and Fig. 48 shows a schematic of the SLAC version of NLC. Professor Richter also has penetrating views on the future of high energy physics, as reproduced in Table 21. I share his view that “non-accelerator experiments underground, on the surface and in space should be better supported. They are very interesting and cost a lot less than a new machine.”

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233

Table 16 View of the future of high energy physics by N. Samios Physics: Standard Model?

I7 parameters

Questions: mass fermions, W’s, Z’s (Higgs supersymmetry) Other states of matter: quark gluon plasma glueballs, exotics, strangelets Symmetries: CP violation chiral symmetry W(S)? Strategies: (1) Continued probing and search for deviations from Standard Model with present facilities W, Z, t masses, sin’ @w,(Y+. rare decays K, B, g-2 (2) Accelerators: higher energies, higher intensities and complementivity (hh, @) Ideal: first high energy hh followed by specific ee E> 1/2TeV few new machines L > 103’ High intensity: upgrade present facilities and possibly few new unique ones h > 10’4/pulse ee s 103s_10s4

Table 17 Near-term l l

February 1996: complete the current collider run May 1996-February 1998: operate the Tevatron in fixed-target mode for - NuTeV, measure sit? BW using v and V beams - KTeV, measure E’/E and branching ratios of rare decays of K’L - continue the measurement of the properties of charm decays (FOCUS and SELEX) - observe the interaction of tau Y’S in matter (E-872)

Table 18 Long-term l

l l

l

. .

plans of Fermi National Laboratory

and charmonium

(E-835)

plans of Fermi National Laboratory

Complete the Main Injector Project and related improvements to the Tevatron complex and resume colliding beams in operation ( 1999) Upgrade the CDF and DO detector to handle a peak luminosity of 2 x 10s2 cm-’ s-’ (1999) Increase the peak luminosity from greater than 5 x 103’ cm-* s-’ ( 1999) to 2 x 1O32cm-’ s-’ with a new storage ring, the Recycler (2001) Construct a neutrino beam from the Main Injector suitable for neutrino oscillation experiments (2001) and mount a short baseline and a long baseline experiment Concurrent fixed-target operation with Main Injector and colliding beam operation (2001) Develop a plan to increase the peak luminosity of the Tevatron to 10”’ cm-* s-’

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234

Table 19 Main elements

of SLAC long-range

program

Near term: l SLC/SLD with polarized electrons (500k more Z”) l 50 GeV polarized electron on polarized proton, neutron and deuteron targets l B-factory and BaBar construction . NLCR&D Mid term: exploiting the B-factory l expanded NLC R & D l

Long term: 6 continued exploitation of the B-factory l participation in an international NLC construction

project

Table 20 Next Linear Collider project l

International

consensus

E’ = 500 GeV,

l l

l

that the goal should be

L = 5 x 107’ cm-” s _’

with expansion capability to 1-l .5 TeV Well coordinated worldwide program exists 300/ 1 beam demagnification demonstrated at SLAC by a collaboration including DESY, Orsay, Max Planck, Munich, Novosibirsk, KEK, FNAL, SLAC. Beam size of 70 nm demonstrated A technically possible schedule: D 1997 - choose best technology D 1997-2000 - engineering design, international agreement to construct, site choice D 2001-2006 - construction of machine and detector

1.3 GeV (S)

Injector

3-6 GeV(S)

Linac (L) 1.428 GHz (S) 2.856 GHz (X) 11.424 GHz -

___ _ . . ,._.

2 GeV (L) Positron Accumulator and Damping Ring 2 GeV, 714 MHz

Electron Damping Ring 2 GeV. 714 MHz

Fig. 48. Schematic of the Next Linear Collider.

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235

Table 21 Professor B. Richter’s views on the future of high energy physics

. .

.

. . . . . . .

Great concern exists everywhere about levels of future funding and opportunities for research as facilities grow larger and the number of major detectors shrinks. The next ten years are packed with scientific opportunities: LEP II, Tevatron, HERA, SLC, B-factories, tau/charm factory, non-accelerator experiments. In 2005: LHC will be new, B-factories will be middle-aged, HERA and the Tevatron will be old, LEP II and SLC will be gone. It takes more than ten years from an accelerator concept to the first experiment. Are we investing enough in thinking about the future? If all of the regions are to continue in high energy physics, our future big facilities will have to be built, run, and funded inter-regionally. On the electron physics side, a large international R & D program is providing the basis for a future machine. Muon colliders are beginning to be studied for collision energies of beyond IO-20 TeV. On the proton side, there is no significant work on the high Tc systems that will be required to build affordable machines much beyond LHC. It should begin. Non-accelerator experiments underground, on the surface, and in space should be better supported. They are very interesting and cost a lot less than a new machine. Since it is very unlikely that budgets will continue to increase, it will not be possible to keep increasing the number of people working in the field. How will we keep our field intellectually young? Finally: D If you are less than 40, you should be doing physics. D If you are older than 55, you should be spending most of your time creating opportunities for the next generation. D Those in the middle should see to it that the best young people stay in the field.

3.4. In Japan: at the National Laboratory for High Energy Physics, KEK Professor Hirotaka Sugawara has kindly provided me with the long-term scenario of high energy physics in his laboratory, shown in Table 22, which centers on the commisioning of the KEK B-factory by the end of 1998 and on the construction of the Linear Collider with international collaboration. The Japanese long-term scenario of high energy physics is the result of intensive studies of two committees, the first one chaired by Y. Nagashima, and the second one chaired by S. Komamiya. Professor Sugarawa has summarized the future of our field as reproduced in Table 23. 3.5. In Germany: at DESY Professor Bjom Wiik has provided us with some fascinating progresses in the construction of a large electron-positron linear collider shown in Fig. 49. The developing program of the 1 GeV Tesla Test Facility free electron laser is progressing well.

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Table 22 KEK long-term l

l

scenario on high energy physics, as provided by Professor

Long term scenario of high energy physics: Construction of LC (e+e- collider) through international

l

cooperation

Japan will be willing to host international research institute Time schedule: _ KEKB; commissioning is scheduled in end of JFY 1998 - JHP; commissioning is expected in 2003? _ LC; HEP subcommittee recommends an early construction and the LC can be conducted concurrently.

Table 23 Future of high energy physics as viewed by Professor

Hirotaka Sugawara

of the Phase-l

LC such that experiments

at the LHC

Sugawara

The future of our field: authorization of LHC - Europe 60 TeV hadron collider? - USA pi*“- collider - Japan LC (e+e- collider) TheJirst subcommittee on future projects in Japan [chaired by Y. Nagashima), report in March 1986 1. To immediately launch an accelerator R & D program, aiming at e + e - linear collider (LC) in the TeV range to be built in Japan. 2. To participate in the research program at the SCC through an international collaboration. The second subcommittee (chaired by Y. Nagashima) , interim report in July 1995 1. Physics program at e+e- linear collider: SUSY scenario, light Higgs boson, colorless supersymmetric particles, balanced strategy when combined with hadron collider programs. 2. LHC project: Phase I : ECM= 250-500 GeV, Phase 2: _&M N I TeV or more. 3. Early construction of an e+e- linear collider through international cooperation 4. Mission of KEK: center for Japanese efforts.

.

Reorganization of the Laboratory to serve research requirements of other fields - Nuclear and materials science: JHP (Japan Hadron Project) 3 GeV rapid cycle proton synchrotron for neutron source (beam power: 0.6 MW) and 50 GeV proton synchrotron (4 x IO’” ppp). - Synchrotron radiation science: 2.5 GeV photon factory ring and 6.5 GeV TRISTAN AR ring. - High energy physics: KEKB project, high-current asymmetric efe- storage rings with ECM = 10.6 GeV for studies of CP violation.

Fig. 50 shows the set-up of the Tesla Test Facility and a schematic of the free electron laser with the following schedule: - electron acceleration by first Tesla module: end of 1995, _ start operation of Tesla Test Facility at 500 MeV: end of 1995,

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Highly Intense source of coherent synchrotron radiatlpn with wavelengths of order 1 A

Particle physics (the universe 1O-12seconds after the “big bang”)

Nuclear physics (NuPECC)

Fig. 49. Research

based on the exploitation

of an electron-positron

linear collider facility.

Measurement

1. and 2. phase of comprksion

laser I-

TESIA Test Facility

1. and 2. phase of compression

new HASYLAB Hall

3. phase of compression 10m+15m

earn VUV Free Electron Laser

Fig. 50. Schematic

i

of Tesla Test Facility and VUV Free Electron Laser Facility.

- SASE FEL tests at the Tesla Test Facility with E < 500 MeV: during 1998 (TTF FEL phase I ), of Tesla modules Nos. 5-8 and of full size undulator: 1998-1999, - start commisioning of TTF FEL at 1 GeV: 2000. Fig. 51 shows (a) the prototype cavities for Tesla and (b) the first results reaching the impressive gradient of 25 MeVIm. The physics of the high energy e + e - linear collider is compelling. The - installation

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t4

chl field gradient

I l-

ch2 t-fforward power

-c

chl

ch2

time I ms

Fig. 51. (a) Prototype cavities for Tesla. (b) First results for Tesla. Table 24 Future plans at CERN 1990s Successfully upgrade and exploit LEP (140 GeV in October 1995; E > 2Mw end 1996) + search for Higgs (to beyond Mz) and SUSY, study WWZ/y vertex, Mw...? l Heavy ion physics with Pb beams from SPS, E’/F (NA48), neutrino oscillations (CHORUS/NOMAD)... . Closure of facilities (a and LEAR at end 1996) to free resources and manpower + l Get construction of LHC well underway l

2000-2003 . Install LHC and LHC experiments l 1SOLDE + select/small fixed target program 2004 + l LHC - (ATLAS, CMS, ALICE, LHCB + ?): hope to have 14( +) TeV from the start

vigorous

research

plans at SLAC, KEK and at DESY will ensure that it becomes a reality.

3.6. At CERN The Director General of CERN, Professor Chris Llewllyn Smith shares with us his future plans at CERN, as shown in Table 24. In addition to the vigorous physics program at LEP, CERN will provide a unique opportunity for heavy ion physics, for kaon physics and neutrino oscillations from SPS. From year 2004 onwards, CERN will host the Large Hadron Collider project, with at least four detectors: ATLAS, CMS, ALICE and LHCB (see the LHC layout shown in Fig. 52). Professor Chris Llewellyn Smith has outlined his strategy and plans for the LHC and this is shown in Fig. 53. LHC detectors are rather large and complex. Fig. 54 shows a schematic of the general purpose ATLAS detector which features strong toroidal fields and Fig. 55 presents the CMS detector which features a unique and precise electromagnetic calorimeter.

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Fig. 52. Layout of the CERN Large Hadron Collider.

LHC A

f 2 pp expts

install

Heavy ions

missing magnets

R expt LEP

_L__L__L__l__I_-I--J 1999

1

2004 f 9.3 TeV 5 4x1 033 cm-2 s-1

1

1

1

1

1

1

2008 t 14 TeV 10% err? s-l

b, Heavy ions “Reach” for SUSY, w’, 2’ = 213 of reach at 14 TeV Very poor for Higgs Fig. 53. The development

of the LHC project.

In addition to LEP and LHC, as pointed out by Professor Chris Llewellyn Smith, CERN also has a very active neutrino physics program, CHORUS, shown in Fig. 56, and NOMAD, shown in Fig. 57. These detectors will provide a most sensitive study of neutrino oscillations. Indeed, the measurement of the mass of the neutrino (see Fig. 58) has raised more questions than answers over the last 15 years. Hopefully, this situation will soon be clarified by the CHORUS and NOMAD experiments. Professor Llewellyn Smith who guides the entire CERN research program shares with us his views of the future of particle physics (as presented in Table 25) and expresses his strong conviction that

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Electromagnetic calorimeters

Inner Detector

Forward

Hsdronk calorimeters

Fig. 54. The ATLAS detector at LHC.

Fig. 55. The CMS detector at LHC.

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Kinematical

-i5m

I

Fig. 56. CHORUS detector.

NOMAD Forwerd Calorimeter

Magnet flux return

Trigger Trigger plane plane

Ti.

Tranhon Radiation Detector

Electromagnetic

Murtn Chambers

COll \ Q,=O.4T Hadronic Calorimeter

Fig. 57. NOMAD detector.

searches at LEP-II, Tevatron and LHC for supersymmetric

particles and Higgs boson should have top

priority.

Professor Stan Wojcicki, Chairman of HEPAP, which advises the US Department of Energy on the future of high energy physics, expresses his views in a similar manner as shown in Table 26.

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Table 25 Views of the future of particle physics by Professor

Reports 279 (1997) 203-250

Chris Llewellyn Smith

Physics: Nature is (probably) supersymmetric (but not necessarily minimal) and there is (probably) an elementary Higgs boson _ searches (LEP2, Tevatron, LHC) should have top priority. l Hints of new physics in neutrino physics should be vigorously pursued - eagerly await results from CHORUS, NOMAD, SNO, S-Kamiokande... l CP violation is potentially the Achilles heel of the Standard Model, and must be sought on different systems ( KTeV; NA48; HERAB; PEP II; TRISTAN II; LHC...), but I will not be surprised if the results are standard. l Searches for proton decay (must occur?), dark matter (seems to exist!) ... are important and necessary in parallel with experiments at the high energy frontier. l

Politics/funding: lnterregional collaboration is a sine qua non: major facilities are now at the limit that can be funded by one region alone, and we must optimise the use of limited resources (and demonstrate - to scientists in other fields, as well as politicians - that we are responsible.

Table 26 Wither HEP in the future? View of high energy physics in the future, by Professor S. Wojcicki, Chairman of HEPAP

a) .

.

First 10 years ( f < 2005): Further probes of SM based on new/upgraded facilities e.g. Searches for “light” new particles - Higgs, SUSY. Leptoquarks etc. (LEP II, Tevatron, HERA). Detailed study of CP violation (KEK, SLAC, HERAB,...). Y oscillations and masses (CER, Fermilab, KEK/Super-Kamiokande). Baryon and lepton number violation ( Super-Kamiokande, BNL,...). Continuation of precision studies in b and K decays, e-w parameters (LEP 1, Tevatron, CESR, Frascati, factories). Non-accelerator experiments (Super-Kamiokande, SNO, Gran Sasso,...). Negative (SM-consistent) results + more frustration. Positive ( SM-violating) results -+ definite focus for the future

b) . . .

Following decade (2005-2015): Study of mass scale up to 1 TeV based on LHC and initial c + e - linear collider (Eon 5 1 TeV). Follow-ups on any positive results from previous decade. Large scale astrophysics/cosmology efforts. Departure from SM has to be seen by this time.

cl .

The decade beyond (2015-2025) : Exploitation of next generation accelerator. Could be: - 2nd generation e+e- linear collider (2 2 TeV), - super hadron collider ( 2 50 TeV), - p+p”- collider (few TeV).

d) .

Next decade and beyond (t > 2025): HEP based on new acceleration principles or End of HEP

.

BNL, B

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243

(1) LJUBINOV, ITEP 102

(2) STECKLER, NASA

-(1)

(1)

(2)

(3) SIMPSON

t

10 - +.

zP,’

cz

(6) -

(4) KAYIOKANDE IMB (ATM.v)

a

(6) GALLEX, KAYIOKANDE (SOLARv) (VW)

-

1 (6) LSND, LOS ALAMOS

10-l (4)

lo-* -

l

(5) 0

lo-3

(REINES)

60

(BUOEY)

02

I

I

I

I

I

I

I

a4

66

66

99

92

94

96

Year

Fig. 58. Measurement

of the electron neutrino mass M,.

4. Particle physics without accelerators In recent years, particularly after the construction of the Laboratory of Gran Sasso and the success of Kamiokande, there has been tremendous progress in the study of particle physics without accelerator. I will list three examples: 4.1. The MACRO experiment Fig. 59 shows the MACRO experiment at Gran Sasso underground by a minimum of 3200 meters of water equivalent so as to have a minimum muon energy of 1.2 TeV. The detector is 77 m x 9.5

Fig. 59. MACRO detector at Gran Sasso: 3 cm pitch streamer tubes and strips for tracking, scintillator for timing and energy measurement, track-etch plastic in middle and sides.

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6

MonteCado with no vp oscillalions. the shade ra MC. uncertainties

Bartol MC wlth Am2 = 6x10-3 eV* and sin* (26)=0.67 1 -1

+ t

Downgoing Muons

74 Upgoing Muons

-0.6

f Upgoing Muons

-0.6

-0.4

-0.2

cos (zenith) Horizontal Muons

Fig. 60. Signals of upgoing muons observed at MACRO. Fig. 61. Zenith distribution

for MACRO upgoing muons.

m x 12 m. It uses streamer tubes for tracking (0.2” resolution) and scintillator for timing (0.5 ns resolution). MACRO provides high statistics unambiguous measurements of upgoing muons from neutrinos penetrating the Earth as shown in Fig. 60. The zenith distribution of MACRO upgoing muons is shown in Fig. 61. The data slightly favour neutrino oscillations with Am2 = 8 x 1O-3 eV2 and sin2( 20) = 0.87. Clearly, more data are necessary. MACRO also puts constraints on the magnetic monopole flux, as seen in Fig. 62. In five years’ time, the MACRO results will be below the important Parker limit over a wide range of the monopole mass. 4.2. The Super-Kamiokande

experiment

The Super-Kamiokande detector is a factor 10 more massive than Kamiokande II with a better energy and spatial resolution, as shown in Table 27. Super-Kamiokande will provide nearly two orders of magnitude improvement in sensitivity in the search for proton decays as shown in Fig. 63. 4.3. The AMS experiment Finally, let me present an experiment, the Alpha Magnetic Spectrometer (AMS) for extraterrestial study of antimatter, matter and missing matter on the International Space Station Alpha. This experiment is an international collaboration from Switzerland (M. Bourquin, H. Hofer), Germany (K. Liibelsmeyer), Italy (R. Battiston, F. Palmonari, G. Laurenti, A. Zichichi), China (H.S. Chen), Finland (J. Torsti), US (S. Ahlen, U. Becker), Russia (Y. Galaktionov), Taiwan (S.C. Lee).

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l

// _____ ___ _ . IfI

_-L&Q __Pw::::::o:3~:: I:::::>

__p?K~________p_+__ ______ _ _--f-;z___ __e?&:__...._.____+ a-6 *a-

----,k

._ _______ ___

Monopole Mass (GeV) Fig. 62. Astrophysical Fig. 63. Sensitivity

of Super-Kamiokande

constraints

on monopole

flux and MACRO flux limits.

for different proton decay channels as compared with current experimental

results.

In the past fourty years, there have been many fundamental discoveries in astrophysics measuring microwaves, X-rays and gamma ray photons. There has never been a sensitive magnetometer in space, due to the extreme difficulty and very high cost of putting a superconducting magnet in orbit. However, recent advancements in permanent magnet material and technology (as shown in Fig. 64) make it possible to use very high grade Nd-Fe-B to construct a permanent magnet with a BL* = 0.15 T m* and with acceptance of - 1 m* sr weighing about 2 tons. The physics objectives of --this experiment are: - To search for antimatter (He, C) in space with a sensitivity of lo4 to lo5 better than current limits. - To search for dark matter by high statistics precision measurements of the e+, y, and p spectra. - To study astrophysics by high statistics precision measurements of D, 3He, B, C, 9Be, “Be spectra. The design principles of the AMS detector are (see Fig. 65) the determinations of: _ Charge IQ\ by measuring energy loss dE/dX in silicon tracker and in scintillation counters Sl to s4. - Momentum and sign of charge (p/Q) by measuring the trajectory with 6 layers of silicon tracker. The magnet (M) provides a bending power of BL* = 0.1 T m*. The six layers of silicon tracker provide x, y, z coordinate measurements to 10 ,um, providing typically: AP/P N 7% at 10 GeV/ N. - Velocity (V) : by measuring the time of flight tl and f2. This is to reject backgrounds. In addition, there are:

246

Table 27 Parameters

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for Super-Kamiokande

and for Kamiokande

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II

Parameters

Super-Kamiokande

Kamiokande

Remarks

total size total mass fiducial mass

41 mh 50000 32000 22000 22 000

16 mh x 19 mh 4500 t 2140 t 1040 t 680 t

supernova proton decay solar neutrino

thickness of anti-counters number of PMT PMT coverage energy resolution

2m 40% 2.6%/a 2.5%

1.2-1.5 m 948 20% 3.6%/a 4%

electrons ( GeV) ,u with Ep < 1 GeV

14%/dqiiGZ

20%/ VqExJ

electrons

position resolution

50 cm N 10cm

II0 cm N 50 cm

IO MeV electron p ---) e+rrO

angular resolution

27” ,-.- I”

27” N 2.7”

IO MeV electron through going p

trigger energy analysis threshold e/p separation pi decay detection

4-5 MeV 5 MeV N 99% 95%

5.0 MeV 7.5 MeV 98* 1% 875 1%

x 39 m o

t t t t

1I 200

Fig. 64. Advancement

of permanent magnet material since 1960.

Fig. 65. Schematic of the AMS detector.

(< 50 MeV)

solar neutrino p-

not included

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1x10 Current

limit

1x10

1x10-5 E 1 z 1x10” r

.o

5 z

z 2 1x10 u 2 ‘F 1x10

$ 1x10

2 $ 1x10

1x10-7

W 2

1x10-s

2 1X10’s

247

Current Limits

z> 9 *Z >2

41 lo4

TZZ

IS experi

ent

Z: .2

Kinetic Energy (GeV/amu) Fig. 66. Sensitivity

(i)

of AMS (3 years on ISSA)

in a search for He and Z > 2 antinuclei

(95% CL).

Two directional Cerenkov counters CI and C2 used to measure velocity, to reject background further and provide indentification of various nuclei. (ii) Transition radiation detectors Stl, St2, St3, St4 used to identify high energy positrons. The physics objectives of AMS are closely related to CP violation and supersymmetry. In the case of the search for antimatter, the Big Bang origin of the Universe requires matter and antimatter to be equally abundant at the very hot beginning. Since there are very little experimental results on the abundance of antimatter in space, there are two classes of theories: (a) the theories predicting the total absence of antimatter and (b) the theories predicting the existence of antimatter. Theories predicting the total absence of antimatter are: (i) Grand Unified Theories: they can explain the absence of antimatter if there is a very strong breakdown of CP. These theories require the existence of heavy neutrinos and the abundance of monopoles. Neither have been found. (ii) Electroweak theories: they can explain the absence of antimatter if there is a very strong breakdown of CP. They require the mass of the Higgs ( MH) to be - 40 GeV (the measurement is M,, > 60 GeV). To ensure that there is indeed a total absence of antimatter, the AMS detector is designed to improve the existing sensitivity by IO4 to 10’ in the search of antimatter, as shown in Fig. 66. Theories predicting the existence of antimatter: The breakdown of time-reversal symmetry in the early Universe might have set different signs for the production of matter and antimatter in different regions of space. Since there are 10’ clusters of galaxies and the observational constraints are limited to the scale of the clusters, the Universe can be symmetric on a large scale. The observed matter-antimatter asymmetry is then a local phenomenon. Fig. 67 shows the sensitivity of AMS in detecting antihelium as compared to the antihelium yield predicted for a symmetric Universe. As seen from Fig. 67, the current limit is not sensitive enough to test the existence of clusters of galaxies of antimatter and AMS is 10” times more sensitive than predictions based on a matter-antimatter symmetric Universe.

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Symmetric

Universe

This experiment

Energy

Fig. 67. AMS antihelium-helium

Launch Date: Altitude

Universe.

200

(deg.):

51.6” 5

crew size: MMon

of a symmetric

04Rl1/98

(nm):

ln~linatlon

(GeV/amu)

sensitivity as a function of energy as compared to the prediction

Dumtlon:

RYS Planned

EVA’s

pafl-*

Extamal Airlock

Am w6F-04

lEtI-

Fig. 68. AMS on shuttle Discovery. The shuttle will fly at an altitude of 200 nautical miles at an inclination

angle of 5 1.6”

with a crew of 5.

The second physics objective of AMS is to search for dark matter. Ninety percent of the Universe is made of dark matter. Most of the physicists (see for examples Refs. [ 5,6] ) believe that Weakly Interacting Massive Particles (WIMP’s) comprise dark matter. This can be tested by direct searches for various annihilation products of WIMP’s in the galactic halo, i.e. p, y, e+,

x+/y-p+... y+...

e++...

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249

II,

0.01

10 1 0.1 Kinetic Energy (GeV)

100

[ 71.

Fig. 70. Location of AMS on the International Space Station Alpha.

The large acceptance of AMS with the Cerenkov counters C, and C2 and time of flight counters, St1 -St4, will enable us to measure very accurately the energy spectrum of p and e+. The third objective of AMS is to study astrophysics. A high statistics measurement of isotopes can address many important issues in astrophysics, for example: (i) The ratio of B/C will enable us to understand cosmic ray propagation in the Galaxy. (ii) The ratio of ‘Be/‘OBe will enable us to determine cosmic ray confinement time in the Galaxy.

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This experiment is scheduled to have a first measurement for ten days on the space shuttle Discovery which is to be launched on 2 April 1998. Fig. 68 shows the arrangement of AMS on the shuttle. This one hundred hours’ flight will enable us to obtain a rather accurate p spectrum below 1.3 GeV as seen from Fig. 69. The p spectrum will provide a sensitive search of supersymmetric particles such as neutralinos. This experiment is currently scheduled to be installed on the International Space Station at the beginning of the year 2001. Fig. 70 shows the location of AMS on the space station.

5. Conclusion Dr. John Peoples, Director of Fermi National Laboratory, has concisely expressed the trend and the future of high energy physics, which I would like to share with you as the conclusion: “The extension of the energy frontier of elementary particle physics will require global collaboration in the construction and operation of the highest energy particle accelerators. Because it is likely that only one major new facility will be built in the world at one time, it wil be necessary to more fully exploit the capabilities of existing facilities than has been the custom in the past. The boundary between the fields of elementary particle physics and astrophysics will provide a great opportunity to understand the early universe and particle physics not accessible to the next generation of accelerators.”

Acknowledgements I want to particularly thank Professor Chris Llewellyn Smith, Professor John Peoples, Professor Burton Richter, Professor Hirotake Sugawara, Professor Bjijm Wiik, Professor Karl Berkelman, Professor Zheng Zhipeng, Professor Klaus Winter and Professor Stan Wojcicki for providing me with most valuable information. I also want to thank the speakers of the Conference for their help and support as well as Professor Guy Coignet, Dr. David Stickland, Dr. Martin Pohl, Dr. Joachim Mnich, Dr. Robert Clare, Dr. Yi Fang Wang, Dr. Jasper Kirkby, Professor Wolfgang Lohmann and Professor Hesheng Chen for their help and the discussions I had with them. I specially want to thank Ms. Laurence Barrin and Ms. Yvette Bernard for their technical support. References [ 1 ] Proceedings of the XVII International Symposium on lepton-photon interactions, Beijing, 15 August 1995, to be published in the review section of Int. J. Mod. Phys. A. [2] OPAL Collaboration, Z. Phys. C 67 ( 1995) 365-378. [3] Proceedings of the 1979 International Symposium on lepton and photon interactions at high energies (August 23-29, 1979). [4] H. Schopper, New results in e+e- annihilation from PETRA, DESY 79179, December 1979. [5] J. Ellis et al., Phys. Lett. B 214 (1988) 403. [6] M.S. Turner, F. Wilzek, Phys. Rev. D 42 (1990) 1001. [7] G. Jungman and M. Kamionkowski, Phys. Rev. D 49 ( 1994) 23 16.