- Email: [email protected]
Physics potential of muon colliders and linear colliders. Comparison
M [ I I i';~"I ",,I;|'/~ [Ik"l
PROCEEDINGS SUPPLEMENTS Nuclear Physics B (Proc. Suppl.) 51A (1996) 54-57
ELSEVIER
PHYSICS POTENTIAL OF MUON COLLIDERS AND LINEAR COLLIDERS. COMPARISON. Ilya F.Ginzburg Institute of Mathematics. 630090. Novosibirsk. Russia ( E-mail: [email protected]) I discuss the physics potential of photon colliders in the fields which was not discussed in the other reports at Conference. Muon colllider will supplement substantially the photon colliders in the study of problems in gauge boson physics. These colliders provide the best place for study of above problems. Besides, muon eolliders will give quite new field in the study of problems in QCD. 1
• Typically, cross section for 77 mode is larger t h a n t h a t for e+e - / # + # - collision.
Introduction
The expected parameters of discussed colliders are given in the table below.
vq GeV e+e 77 e7 #+~-
/ : (1034
500 1 1500/200( 1 400 1200/160( 450 1350/180( 1400 4000
<
Polar]
cm-2s -1 -~- ~
za-
tion +
1% ~ 5 + 10% ~ 10%
+
~ 5%
+
20
-
0.05%
I
I present here the monochromatic variant of 7 7 / e 7 collider (see [1]). Besides, the supermonochromatic variant of 7 7 / e 7 collider can be realized with E~ ~ 0.95E, A E / E ~ 1 + 1.5%, £.~.y = 0.05, £ ~ .~ 0.2. I will use below abbreviations: LC - for all linear colliders, PLC - for photon colliders (e7 and 77). POSSIBLE SOURCES DIFFERENCE
OF
W i t h the growth of s, the cross section for the production of some system decreases as in s -1 in e + e - / / z + # - collision. For the e 7 / 7 7 collision the similar cross sections either tends to energy independent constant or decreases with s, but more slow than in the e + e - / # + # - collision. • The angular distribution of secondaries is roughly isotropic in e + e - / # + # - collisions. The small energy region is enhanced at PLC. (The observations there are possible - - there are N O P H Y S I C A L and G E N E R A L C O N S T R U C T I V E reasons to close this angular interval.) 2. # + # -
vs e+e - and PLC.
• Initial particle instability. • Higher mass of initial particle. • Much higher real monochromaticity A E / E (Smaller Initial State Radiation, negligible beamsstrahlung). • Higher energy.
1. e + e - / # + #
- vs P L C ( e 7 / " / 3 ' ) .
• Quite different initial state. Mainly J = 1 for e+e - / # + # - and all angular m o m e n t a (except J = 1) for PLC.
• Much higher luminosity. • Relatively small angle region is forbidden for the measurements.
0920-5632/96/$15.00 © 1996 Elsevier Science B.V. All rights reserved. PII: S0920-5632(96)00416-1
LE Ginzburg/Nuclear Physics B (Proc. Suppl.) 51A (1996) 54-57
2
Key points in program used these features
My first impression was that the first point provides really new option for the muon collider. The finite beam size effect kills this option [2]. The next two points provide the spectacular options in the study of Higgs and its SUSY partners. It was discussed in the excellent report of J. Gunion at this conference. The main strategy here will be - - discovery of Higgs at hadron colliders or LC, the measuring of its two-photon width at PLC and detail study of Higgs at muon collider. The higher luminosity provides new option in detail study of t-quark production and CP Violation. These opportunities were discussed in the reports of D. Amedei and A. Soni at this conference. Next, there are almost evident additional opportunities of muon coUider in discovery of new particles related to its higher energy and hminosity. I will not discuss them. I will discuss problems in gauge boson physics and QCD, based on the last three features of muon colliders. I only mark these problems. The detail studies are necessary here.
3
Gauge boson physics
After first results at LEP the main problem in this field will be to test S M mutually. In particular, . It is necessary to describe the delicate details of SM itself, including detail description of SM as the gauge theory of UNSTABLE particles (this theory is absent now). I expect nontrivial effects here at the level a ( F w / M w ) ,,~ 10 -3. Therefore, one should see processes with 1 - 10 millions events. The e+e - LC and muon
55
colliders will give much lower statistics. The PLC's provide here the best opportunities. 2.
We hope to see violations of SM obliged by some underlying interactions. It will be manifest itself as some set of anomalous interactions of gauge bosons. The separation of these anomalies is necessary to understand possible nature of this underlying interaction. The detail study of wide set of processes with W and Z production can separate effects from different anomalies. The classification of possible processes from this point of view is the problem for nearest future. In this problem PLC and muon colliders supplement each other.
3. The third field is the strong interaction in Higgs sector at the energies above 1 TeV (if it exists). This strong interaction should manifest itself in the processes with production of longitudinal W and Z. The processes like 77 ~ W L W L seemed observable at PLC. However, (due to gauge invariance of EM interaction) the fraction of WL in the produced W is expected to be small. One can expect the better opportunities in the processes like # + # u P Z Z at the collider with higher energy and luminosity. . The study of W decay with high accuracy will give new information about CP violation and the delicate details of interaction of gauge fields with the matter. 3.1
Photon
Colliders
The e7 and 77 colliders provide the best opportunities in the discussed studies. They will be W-factories with production of about 10 millions W's per year [3],[4].
LE Ginzburg/Nuclear Physics B (Proc. Suppl.) 51A (1996) 54-57
56
The cross sections of the basic processes 73' ~ W W and e 7 ~ u W are energy independent beginning from c.m. energy 300-400 GeV and their scale is
aw-
8ra ~ - ~ 80 pb. M~v
(1)
initial muon energy is given by the factor a (In sz d n w ,~ 4~rsin2 0 W 4M 2
dz 1)-~--.
(4)
for both transverse and longitudinal W's. The typical relative W ' W * luminosity for v ~ = 4 TeV, ~/s ,,~ 0.3 is
These large enough cross sections provides 3A~ opportunity to study in detail a huge set of £,ww~2"lO= . (5) $ processes of third and forth order in E W interaction at the PLC (with expected high counting With above muon and photon collider lurate 106 + 103 events per year) [4]. T h a t are minosity and for A~/~ = 0.5 we obtain processes £ w w "~ 0 . 0 2 £ ~ . (6) e7 ~ e W W ; e7 ~ v W Z ; Therefore, the new set of reactions between 77 ~ W W Z ; . . . gauge bosons will be accessible for study here. e7 ~ e W W Z ; 77 --+ W W W W ; They complement substantially t h a t at PLC. (2) The constraints due to EM gauge invariance 3'7 ~ W W Z ; ... absent here. 73'--+ ( e + e - ) W W ( # + # - ) ; ... The study of some of these processes will For example, the cross section of the first of continue the similar studies at LC's with higher these processes is about 27 pb at v ~ = 2 TeV. energy and statistics. T h a t are This high potential of PLC is limited parz z , uw" uz, (7*/z*)w* zw, tially by the gauge invariance of electrodynam- w ' w * ics which can constrain the possible violations z'w" H+, ... (7) of SM in the photon collisions. The new set of reactions can be studied at the muon colliders only (with the rate about 3.2 Muon Colliders thousands per year). T h a t are the third order The # + # - collider will provide new opportuni- processes: ties due to its higher energy and luminosity. It relates to fusion processes like W ' W * -+ W W Z , ~ ZZZ; #W* --+ uWZ, (7*/Z*)W* --+ W W W , W Z Z , ... (8) # + # - ---, #uSe; # + # - ~ #+aft-;... (3) with some final state 9r having the squared c.m.s, energy (effective mass) ~. These processes could be described roughly with effective W ' W * , 7*W*, Z ' W * , . . . luminosities (like standard Weizsacker-Williams approximation for the photon fusion). The relative number of W* carrying fraction z from
The additional difference with the e+e - colriders is in the better opportunity to study the reactions with initial Z*. Indeed, the relative number of W* or Z* per muon is the same as that for electron at the same energy. However, the number of 7* per muon is ,,~ ~ in comparison with that per electron (due to difference in logarithms). Therefore, in the (7*/Z*)W*
LE Ginzburg//Vuclear Physics B (Proc. Suppl.) 51A (1996) 54-57
fusion the Z* contribution is enhanced here in comparison with that at e+e - collider. The special studies are necessary to see opportunity to extract final WL, ZL for investigation of strong interaction in Higgs sector.
4
Q C D and hadron physics
Muon coll]der with high luminosity provides opportunity to study the QCD processes in the new region. The W W fluxes (4,5,6) show opportunity to study with the reasonable rate the processes like (7*/Z*)(7*/Z*) ~ hadrons, (7*/Z*)W* ~ hadrons, ..
at virtual]ties Q~ ,~ (100 GeV) 2 for both 7 or Z and W. At the c.m.s, energy about 1 TeV it will be quite new region for hadron physics which should be described by pQCD good. What is here B F K L Pomeron? What is here Odderon ? In addition to new region of parameters, the new problems could be studied here - How are the specific features of hadronic processes, initiated by charged current ( W ) instead of neutral one ? How are the effects due to P nonconservation (with the 7 / Z initial state) and, perhaps effects of CP violation ? This work is supported by grants of Russian Foundation of Fundamental Investigations and 1NTAS-93-1180. Besides, I am thankful to Soros educational program for support.
References [1] I.F. Ginzburg, G.L. Kotkin, V.G. Serbo, V.I. Telnov, Preprint 81 - 50 Inst.
57
Nucl. Phys. Novosibirsk, 25.02.1981; Sov. ZhETF Pis'ma. 34 (1981) 514; Nucl. Instr. and Methods in Research (NIMR) 205 (1983) 47; I.F. Ginzburg, G.L. Kotkin, S.L. Panfil, V.G. Serbo, V.I. Telnov, NIMR 219 (1983) 5; V.I. Telnov, NIMR
A294(1990) 72. [2] I.F.
Ginzburg. Preprint DESY-95-168 (1995), report in this Conference; K.V. Melnikov, V.G. Serbo. hepph/96-01290.
[3] I.F. Ginzburg, G.L. Kotkin, S.L. Panfil, V.G. Serbo, Nucl. Phys. B228 (1983) 285, E.: B243 (1984) 550.
[4] I.F. Ginzburg, V.A. Ilyin, A.E. Pukhov, V.G. Serbo, S.A. Shichanin, Phys.At.Nucl. 56 (1993) 39; I.F. Ginzburg, V.A. Ilyin, A.E. Pukhov, V.G. Serbo, In preparation; I.F. Ginzburg, Sov.Yad.Fiz. (Phys. At. Nucl.) 58 (1995) 326; NIMR A355 (1995) 63; Proc. 9th Int. Workshop on Photon - Photon Collisions, San Diego (1992) World Sc. Singapore; Proc. 10th Int. Workshop on Photon - Photon Collisions, Sheffield (1995); G. Belanger, F. Boudjema, I.F. Ginzburg. in preparation.
PROCEEDINGS SUPPLEMENTS Nuclear Physics B (Proc. Suppl.) 51A (1996) 54-57
ELSEVIER
PHYSICS POTENTIAL OF MUON COLLIDERS AND LINEAR COLLIDERS. COMPARISON. Ilya F.Ginzburg Institute of Mathematics. 630090. Novosibirsk. Russia ( E-mail: [email protected]) I discuss the physics potential of photon colliders in the fields which was not discussed in the other reports at Conference. Muon colllider will supplement substantially the photon colliders in the study of problems in gauge boson physics. These colliders provide the best place for study of above problems. Besides, muon eolliders will give quite new field in the study of problems in QCD. 1
• Typically, cross section for 77 mode is larger t h a n t h a t for e+e - / # + # - collision.
Introduction
The expected parameters of discussed colliders are given in the table below.
vq GeV e+e 77 e7 #+~-
/ : (1034
500 1 1500/200( 1 400 1200/160( 450 1350/180( 1400 4000
<
Polar]
cm-2s -1 -~- ~
za-
tion +
1% ~ 5 + 10% ~ 10%
+
~ 5%
+
20
-
0.05%
I
I present here the monochromatic variant of 7 7 / e 7 collider (see [1]). Besides, the supermonochromatic variant of 7 7 / e 7 collider can be realized with E~ ~ 0.95E, A E / E ~ 1 + 1.5%, £.~.y = 0.05, £ ~ .~ 0.2. I will use below abbreviations: LC - for all linear colliders, PLC - for photon colliders (e7 and 77). POSSIBLE SOURCES DIFFERENCE
OF
W i t h the growth of s, the cross section for the production of some system decreases as in s -1 in e + e - / / z + # - collision. For the e 7 / 7 7 collision the similar cross sections either tends to energy independent constant or decreases with s, but more slow than in the e + e - / # + # - collision. • The angular distribution of secondaries is roughly isotropic in e + e - / # + # - collisions. The small energy region is enhanced at PLC. (The observations there are possible - - there are N O P H Y S I C A L and G E N E R A L C O N S T R U C T I V E reasons to close this angular interval.) 2. # + # -
vs e+e - and PLC.
• Initial particle instability. • Higher mass of initial particle. • Much higher real monochromaticity A E / E (Smaller Initial State Radiation, negligible beamsstrahlung). • Higher energy.
1. e + e - / # + #
- vs P L C ( e 7 / " / 3 ' ) .
• Quite different initial state. Mainly J = 1 for e+e - / # + # - and all angular m o m e n t a (except J = 1) for PLC.
• Much higher luminosity. • Relatively small angle region is forbidden for the measurements.
0920-5632/96/$15.00 © 1996 Elsevier Science B.V. All rights reserved. PII: S0920-5632(96)00416-1
LE Ginzburg/Nuclear Physics B (Proc. Suppl.) 51A (1996) 54-57
2
Key points in program used these features
My first impression was that the first point provides really new option for the muon collider. The finite beam size effect kills this option [2]. The next two points provide the spectacular options in the study of Higgs and its SUSY partners. It was discussed in the excellent report of J. Gunion at this conference. The main strategy here will be - - discovery of Higgs at hadron colliders or LC, the measuring of its two-photon width at PLC and detail study of Higgs at muon collider. The higher luminosity provides new option in detail study of t-quark production and CP Violation. These opportunities were discussed in the reports of D. Amedei and A. Soni at this conference. Next, there are almost evident additional opportunities of muon coUider in discovery of new particles related to its higher energy and hminosity. I will not discuss them. I will discuss problems in gauge boson physics and QCD, based on the last three features of muon colliders. I only mark these problems. The detail studies are necessary here.
3
Gauge boson physics
After first results at LEP the main problem in this field will be to test S M mutually. In particular, . It is necessary to describe the delicate details of SM itself, including detail description of SM as the gauge theory of UNSTABLE particles (this theory is absent now). I expect nontrivial effects here at the level a ( F w / M w ) ,,~ 10 -3. Therefore, one should see processes with 1 - 10 millions events. The e+e - LC and muon
55
colliders will give much lower statistics. The PLC's provide here the best opportunities. 2.
We hope to see violations of SM obliged by some underlying interactions. It will be manifest itself as some set of anomalous interactions of gauge bosons. The separation of these anomalies is necessary to understand possible nature of this underlying interaction. The detail study of wide set of processes with W and Z production can separate effects from different anomalies. The classification of possible processes from this point of view is the problem for nearest future. In this problem PLC and muon colliders supplement each other.
3. The third field is the strong interaction in Higgs sector at the energies above 1 TeV (if it exists). This strong interaction should manifest itself in the processes with production of longitudinal W and Z. The processes like 77 ~ W L W L seemed observable at PLC. However, (due to gauge invariance of EM interaction) the fraction of WL in the produced W is expected to be small. One can expect the better opportunities in the processes like # + # u P Z Z at the collider with higher energy and luminosity. . The study of W decay with high accuracy will give new information about CP violation and the delicate details of interaction of gauge fields with the matter. 3.1
Photon
Colliders
The e7 and 77 colliders provide the best opportunities in the discussed studies. They will be W-factories with production of about 10 millions W's per year [3],[4].
LE Ginzburg/Nuclear Physics B (Proc. Suppl.) 51A (1996) 54-57
56
The cross sections of the basic processes 73' ~ W W and e 7 ~ u W are energy independent beginning from c.m. energy 300-400 GeV and their scale is
aw-
8ra ~ - ~ 80 pb. M~v
(1)
initial muon energy is given by the factor a (In sz d n w ,~ 4~rsin2 0 W 4M 2
dz 1)-~--.
(4)
for both transverse and longitudinal W's. The typical relative W ' W * luminosity for v ~ = 4 TeV, ~/s ,,~ 0.3 is
These large enough cross sections provides 3A~ opportunity to study in detail a huge set of £,ww~2"lO= . (5) $ processes of third and forth order in E W interaction at the PLC (with expected high counting With above muon and photon collider lurate 106 + 103 events per year) [4]. T h a t are minosity and for A~/~ = 0.5 we obtain processes £ w w "~ 0 . 0 2 £ ~ . (6) e7 ~ e W W ; e7 ~ v W Z ; Therefore, the new set of reactions between 77 ~ W W Z ; . . . gauge bosons will be accessible for study here. e7 ~ e W W Z ; 77 --+ W W W W ; They complement substantially t h a t at PLC. (2) The constraints due to EM gauge invariance 3'7 ~ W W Z ; ... absent here. 73'--+ ( e + e - ) W W ( # + # - ) ; ... The study of some of these processes will For example, the cross section of the first of continue the similar studies at LC's with higher these processes is about 27 pb at v ~ = 2 TeV. energy and statistics. T h a t are This high potential of PLC is limited parz z , uw" uz, (7*/z*)w* zw, tially by the gauge invariance of electrodynam- w ' w * ics which can constrain the possible violations z'w" H+, ... (7) of SM in the photon collisions. The new set of reactions can be studied at the muon colliders only (with the rate about 3.2 Muon Colliders thousands per year). T h a t are the third order The # + # - collider will provide new opportuni- processes: ties due to its higher energy and luminosity. It relates to fusion processes like W ' W * -+ W W Z , ~ ZZZ; #W* --+ uWZ, (7*/Z*)W* --+ W W W , W Z Z , ... (8) # + # - ---, #uSe; # + # - ~ #+aft-;... (3) with some final state 9r having the squared c.m.s, energy (effective mass) ~. These processes could be described roughly with effective W ' W * , 7*W*, Z ' W * , . . . luminosities (like standard Weizsacker-Williams approximation for the photon fusion). The relative number of W* carrying fraction z from
The additional difference with the e+e - colriders is in the better opportunity to study the reactions with initial Z*. Indeed, the relative number of W* or Z* per muon is the same as that for electron at the same energy. However, the number of 7* per muon is ,,~ ~ in comparison with that per electron (due to difference in logarithms). Therefore, in the (7*/Z*)W*
LE Ginzburg//Vuclear Physics B (Proc. Suppl.) 51A (1996) 54-57
fusion the Z* contribution is enhanced here in comparison with that at e+e - collider. The special studies are necessary to see opportunity to extract final WL, ZL for investigation of strong interaction in Higgs sector.
4
Q C D and hadron physics
Muon coll]der with high luminosity provides opportunity to study the QCD processes in the new region. The W W fluxes (4,5,6) show opportunity to study with the reasonable rate the processes like (7*/Z*)(7*/Z*) ~ hadrons, (7*/Z*)W* ~ hadrons, ..
at virtual]ties Q~ ,~ (100 GeV) 2 for both 7 or Z and W. At the c.m.s, energy about 1 TeV it will be quite new region for hadron physics which should be described by pQCD good. What is here B F K L Pomeron? What is here Odderon ? In addition to new region of parameters, the new problems could be studied here - How are the specific features of hadronic processes, initiated by charged current ( W ) instead of neutral one ? How are the effects due to P nonconservation (with the 7 / Z initial state) and, perhaps effects of CP violation ? This work is supported by grants of Russian Foundation of Fundamental Investigations and 1NTAS-93-1180. Besides, I am thankful to Soros educational program for support.
References [1] I.F. Ginzburg, G.L. Kotkin, V.G. Serbo, V.I. Telnov, Preprint 81 - 50 Inst.
57
Nucl. Phys. Novosibirsk, 25.02.1981; Sov. ZhETF Pis'ma. 34 (1981) 514; Nucl. Instr. and Methods in Research (NIMR) 205 (1983) 47; I.F. Ginzburg, G.L. Kotkin, S.L. Panfil, V.G. Serbo, V.I. Telnov, NIMR 219 (1983) 5; V.I. Telnov, NIMR
A294(1990) 72. [2] I.F.
Ginzburg. Preprint DESY-95-168 (1995), report in this Conference; K.V. Melnikov, V.G. Serbo. hepph/96-01290.
[3] I.F. Ginzburg, G.L. Kotkin, S.L. Panfil, V.G. Serbo, Nucl. Phys. B228 (1983) 285, E.: B243 (1984) 550.
[4] I.F. Ginzburg, V.A. Ilyin, A.E. Pukhov, V.G. Serbo, S.A. Shichanin, Phys.At.Nucl. 56 (1993) 39; I.F. Ginzburg, V.A. Ilyin, A.E. Pukhov, V.G. Serbo, In preparation; I.F. Ginzburg, Sov.Yad.Fiz. (Phys. At. Nucl.) 58 (1995) 326; NIMR A355 (1995) 63; Proc. 9th Int. Workshop on Photon - Photon Collisions, San Diego (1992) World Sc. Singapore; Proc. 10th Int. Workshop on Photon - Photon Collisions, Sheffield (1995); G. Belanger, F. Boudjema, I.F. Ginzburg. in preparation.