Very high energy cosmic ray events

139c

Nuclear physics A418 (1984) 139~~160~ North-Holland, Amsterdam

Very High Energy Cosmic Ray Events

W. Vernon Jones* Department of Physics and Astronomy, Rouge, LA, 70803-4001, USA

Louisiana

State University,

Baton

Abstract High energy cosmic rays are reviewed in terms of our present understanding The spectral change of prominent features in the primary energy spectrum. observed around lOI eV can be explained either by a change in the primary chemical composition or by a change in the nuclear interaction Anomalous interactions are prevalent at about the same energy characteristics. where galactic propagation effects are expected to lead to the dominance of iron nuclei. 1. INTRODUCTION Measurements

on very high energy cosmic

spectra that can be interpreted composition

or in anomalous

Differentiation accumulated particles

nor the primary

transverse

which

momenta

interaction

of high energy

vertices

gluon plasma

attention which

observed.

Only a

nuclei heavier than

reported approximately

and high

(B-A) collisions.*

as possible

candidates

two by the

The JACEE for quark-

is the prime theme of this conference.

report will not dwell on either the JACEE data or the arguments

phase transition are discussed

from nuclear matter to quark-gluon

in detail

in several accompanying

newest JACEE data are contained JACEE group.4

However,

this paper because

in a separate

the JACEE experiment

it is the only experiment

studies of very high energy B-A interactions, data relevant around

are directly

high multiplicities

nucleus-nucleus

(QGP) formation,3

because most of the

i.e. neither the primary

during the last few years

has reported unexpectedly

have received widespread

in the energy

nuclei.

(E > 100 GeV/nucleon)

Some of these were

in several

structure

is difficult,

indirectly,

ago,I but most have been collected

JACEE project,

This

of the primary

between the two alternatives

helium have been measured.

events

interactions

data has been determined

few dozen interactions

decades

rays exhibit

either in terms of changes in the chemical

to crucial

questions

matter,

papers in this volume. paper presented

carrying

supported

about the primary

by the U.S. National

0375-9474/84/$03.00 @ Elsevier Science Publishers (North-Holland Physics Publishing Division)

Science

B.V.

attention

in

out direct

and because it is also providing cosmic

1013 - 1014 eV.

* Research

The

by Saito for the

will be given special currently

for a

since both topics

Foundation.

ray composition

l4Oc

2.

W. V. Jones / Very High Energy Cosmic Ray Events

INTERPRETATIONS

2.1.

Composition

Cosmic Earth. energies

and spectra

rays consist of the nuclei of essentially

As illustrated are observed

The integral increase

OF COSMIC RAY ENERGY SPECTRA

to cover an enormous

intensity

in energy.

by the integral primary

decreases

1O1' eV it is only 1 nucleus/km2-sr-yr. energies

measure~nts

require a wide

using satellite

energies

around 101' eV.

required

for investigating

found on

shown in Fig. 1, their

range extending

to above 1020 eV.

by a factor of 50 to 100 for each decade

At 1016 eV the flux.is

at different

all the elements

spectrum

about 1 nucleus/m2-sr-yr,

Studies

of the vastly different

range of experimental

and balloon exposures

Indirect

measurements

while at

techniques.

currently

with

fluxes Direct

exist only up to

large area detectors

the low fluxes at higher energies.

These

are

inc'iude

DIRECT ._ I NDI RECT ____ ____rt.__.,._____~, MO 10 t

Fig.

1

Integral

all-particle

of high energ

studies

of underground

studies

of extensive

In principle,

Mans

cosmic

over the approximate

air showers

direct measurements

spectrum

rays.

range 1014 - 10r6 eV and

(EAS) from 1015 - 1Ol6 eV to above lo*' eV. could be made up to -lOI

area (-100 m*) space array, but it is unlikely

eV with a large

that such an array will be

141c

W. V. Jones / Very High Energy Cosmic Ray Events routinely

operating

At low energies measured species

before the end of this century. (< 101' eV) where the flux is large enough to have been

for individual obeys a power

particle

it is observed

types,

law spectrum of the form

Fig. 2 shows the low enerLly differential nuclei:

protons,

helium,

Differential

energy

(E 5 IO4 MeV/nucleon) magnetosphere, Furthermore, helium.

the single

spectra

of low

index fits the flux

by the solar for each species.

index Y = 2.7 is valid for protons, index y = 2.4 observed

carbon, and

for iron were to continue

then iron nuclei would

dominate

the cosmic ray

1015 eV.

for protons

and helium,

spectral

rays have not been made for individual GeVfnucleon.

source

Except for the lowest energies

the fluxes are modulated

to higher energies,

flux above about

For example,

.

P, He, C and Fe nuclei.

a single spectral

If the flatter

indefinitely

Except

where

dN/dE = k E'

fluxes for some dominant

carbon and iron.5

Fig. 2

that each nuclear

Furthermore,

~asure~nts

for high energy cosmic

species above a few hundred

because of statistical

limitations,

the all-particle

142~

W. V. Jones / Very High Energy Cosmic Ray Events

spectrum

is generally

given in integral

form.

Figure 3 shows the integral

all-

_- KT2 k i-

16”

N”

‘5 Kfi4

z z IO5 5 g KY.

t

16’

l

PROTON-1,2,3

+

STATISTICAL

DATA I f

x 1 INDlVlDUAL

i

l6*

1

10’2

IO”

IO’3

ICY

d5

1016

E (eV)

Fig. 3

All-particle

spectrum

from PROTON satellites.

particle which

spectrum

observed

by Grigorov -et a1.6 in the PROTON satellite

showed that the all-particle

spectrum

has a single effective

index of 1.64 i- 0.01 from 1O1l to 1Ol4 eV/nucleus. (calori~ter)

did not resolve individual

direct observations energy

to approach

steepening 10lg eV.

E1a5*

spectrum

data6'13

on the integral

The fluxes of protons,

extrapolations

flux around

points where extensive

be attributed

all-particle

air shower

to a mismatch

means, physical

changes

flux is multiplied

are also indicated.

1Ol5 eV is indicated

at lower energies.

("ankle") around

in Fig. 4, where the

and iron nuclei expected

of low energy ~asure~nts

in the absolute

observations

helium,

of the low

shown in Fig. 1 are a

1Ol5 - 1016 eV and a flattening

The "knee" and "ankle" are more evident

accumulated

those were the first

of iron nuclei.

in the all-particle

("knee") around

species,

spectral

the apparatus

the region where extrapolation

fluxes indicate the dominance

Two obvious features

nuclear

Although

series,

from The uncertainty

by the spread in the data

results are connected Although

to results from direct

some part of the spectral

in joining together

by

spectra measured

are needed for a full explanation.

changes may

by different

The possibilities

W. V. Jones f Very High Energy

CosmicRay Events

143c

I

LOG

ENERGY(ev)

Fig. 4 Integral spectra multiplied by Elo5 showing the "knee and "ankle features.

include:

(1) a change

in chemical

(2) a change in the characteristics

"Knee" as evidence

2.2.

Cosmic galactic

magnetic

effect

nuclei.

leakage from the

fields that contain them, i.e., heavier

nuclei should be

spectrum. would

dependent Within

increasing

relative

Changes

Figure 5 illustrates

schematically

a range of about two decades in energy,

region

abundances

the

leakage from the galaxy would have on the all-

change from dominance

Over the transition

successively

species,

to exhibit

to higher total energies. l4

composition

cosmic rays and/or

rigidity dependent

that rigidity

particle

of primary

of nuclear interactions.

for change in composition

rays are expected

contained

composition

by protons to dominance

the chemical

by iron

(around the "knee") the flux would show

of heavier nuclei as the lighter species are

depleted. in the chemical

composition

e.g., iron, is getting

indicated

by the flatter

crossover

energy the flatter

particles

superimposed

would also result if one or more

relatively

iron spectrum

more abundant with energy,

observed

at low energies.11*15

spectrum would emulate

a separate

on the normal spectrum dominated

spectrum

observed

provided

both the iron and proton spectral

indices

At some

source of

by protons.

for iron below 1OI2 eV indicates a crossover

as

The flat

--1015 eV,

remain constant.

144c

W. V. Jones / Very High Energy Cosmic Ray Events

(PROTOHS)

4 .I**.,,1 ,.ulul

10"

10" TOTAL

10'2 Fig. 5

Spectral dependent

The existing explanations charges,

duration,

large area exposures.

individually

spectral

require

range

long

A space array may offer the only practical

Figure

species.

6 shows the data collected

It is significant

results agree with extrapolations

particle

are great enough to have been by

slopes over the energy

that for both protons

of both absolute

and helium

fluxes and

indices of lower energy data.

Figure

for checking

the composition

models

of light and heavy nuclei in different

7 illustrates

how the average mass number

is to measure

energy

CA> follows

the

iron abundance.17

The JACEE project composition dependent

for individual over the energy

in Fig, 1, such measurements

no change in the spectral

101* - 1014 eV,16

the relative abundances

relative

either of these

spectra measurements

intensities

The best chance at present

regions.

by rigidity-

leakage from the galaxy.

up to 1014 eV.

JACEE, which has observed

the JACEE

1020

the spectra of all but the most abundant

Only the proton and helium

interval

produced

10'8

groups, are needed especially

As was implied

means for measuring

measured

features

Differential

is correct,

eV.

10'6 ENERGY(eV)

data are too meager to ascertain whether

or at least charge

lOI4 - lOI

, , ,,,,,J I .d

is attempting

to make observations

over the range 1013 - 1014 eV.

energy thresholds,

Because

on the chemical

of biases due to charge

the JACEE data have been reported

so far only for

1452

Jones f Very High Energy Cosmic Ray Events

ENERGY(TeVM Proton and helium spectra

observed

in JACEE balloon exposures.

lRON DC'VlNANCE

;+_;+_:

.-

IO3

100

i0

104

105

107

106

108

'

w

1

109

GEVl NUCLEUS Fig. 7

Relative

abundance

of iron and the average

mass number of the primary energies

above 1Ol4 eV, where the detection

lOO%.lG

Figure

composition.

efficiencies

are essentially

8 shows a sample of 19 events with total energies

1Ol4 eV that was collected

in the first two JACEE balloon

sample

of 54 events selected

represents

a subset

ray energy ZEY 2 10 TeV. the energy spectrum all-particle

The average mass number is -10.

of Grigorov _L et al

This data

on the basis of total gamma

of the highest energy JACEE events

spectrum

exceeding

flights.

Figure

9 shows that

is consistent

with the

146~

W. V Jones / Very High Energy Cosmic Ray Events

co -__--: 51

----j

0

-----j

c

------:

L

----

HI H

.

-----4

bk,MI)

..

s/

---“id.. __.A;

.

.. I

IO" Fig. 8

.

. on

.

*.......I

.I

10'4 E&VI Distribution

10'6

100 TeV.

GRIGOROV ‘El AL. ALL FARTICLES JACEE: ALL MRTICLES

\

Comparison

of the highest

JACEE data with the Grigorov

2.2.

"Ankle" as evidence

For energies

up through

..-

of JACEE events with

total energy exceeding

Fig. 9

.

10'5

for extragalactic

energy

spectrum.

component

the lower EAS energies,

particle

trajectories

are

147c

W. V. Jones / Vety High Energy Cosmic Ray Events

expected

to be highly

irregular

galaxy.

For the highest

energies,

enough that the effects in comparison

in the density

to the field direction directions. produce

however,

of small-scale

to regular circulatory

A gradient

galaxy.

because of tangled

a galactic

At energies north galactic

of particles asymmetry

a radial gradient

north-south

regions of the

in some direction in the observed

perpendicular

arrival

in the plane of the galaxy would

asymmetry.

polar region exceeds

the Virgo cluster

iS large

should become negligible

above about 5 x 1Ol8 eV there is evidence

is thought to be evidence

field lines in the

the radius of gyration

irregularities

motion over limited

would produce

For example,

magnetic

that the flux from the

that from low galactic

latitudes."

for either a new proton component

or, if the particles

This

from the region of

are heavier than helium,

a new component

from the inner part of our galaxy.

The importance

shown in Fig. 10, which

the scale of gyio radii in a uniform

microgauss

illustrates

field for protons,

oxygen,

of the nuclear

charge is 2

and iron nuclei at 7 x 10 lg eV.*'

This

Globularclusters 5

F

Kpc 1 0

Fig. 10

Comparison

of gyro radii for 7 x 101' eV

p, 0, Fe nuclei in the galaxy. is the approximate directions protons,

of showers observed

by the arrow marked

they must be incident

considered evidence

enerw

indicated

to be the favorite

for an excess

"N".

from outside

to have the favored If the primary

the galaxy.

source for an extragalactic

of particles

arriving

arrival

particles

are

The Virgo cluster flux.

from the south polar

There

is

is also

148,

W. V. Jones / Very High Energy Cosmic Ray Events

direction.21 interactions

At energies

above about 10"

with the 3OK cosmological

eV the cross section

microwave

radiation

for

rules out sources

beyond the Virgo supercluster.

2.3.

Information

Analysis standard

interaction

characteristics

a varying chemical

Figure

11 compares

longitudinal by studying (Constant

data,

the zenith

for showers

composition

at several

initiated

production

rising with

by nuclei)

f

I

I

400

ATMOSPHERE

Fig. 11

Longitudinal initiated

angle varies the sampling

and observations

for the

The data were obtained

of shower sizes at equal intensities,

I

I

I

I

600

DEPTH

profiles

I

the zenith

I

IO00

(g cni2)

of air showers

by P and Fe Nuclei.

depth of surface

initiated

3

800

detectors.)

show that cascade maxima occur earlier

nuclei than for showers

also

above about 1015 eV.

shower energies.22

angle variations

using

fixes the energy of the primary, while changing

200

clearly

of air showers

(2) cross sections

the results of calculations

develop~nt

intensity

profiles

(e.g., (1) models of particle

ISR and SPS-Collider

and (3) linear superposition

indicates

shower profiles

of EAS data on the longitudinal

based on FNAL, energy,

from longitudinal

by protons.

The calculations

for showers

initiated

by iron

The data are in better agreement

W. V. Jones / Very High Energy Cosmic Ra.v Events

149c

with the curves for iron primaries. In general,

the position

given particle

species,

rate, decreases

of the cascade

able on the energy dependence

the dominant

GeV are clearly

rate is given in Fig. 12, along trends for proton and iron primaries. 23-25

species

showers.

by lo6 GeV.

indicates

cosmic

data, is valid for

at that energy.

with smooth extrapolation

The implication

The EAS data at lo6

of the elongation

rate

is that iron has become the dominant

The steep increase

yet another

galactic

is based on accelerator

cosmic ray component

inconsistent

elongation

The data avail-

of the elongation

The anchor point at 100 GeV, which

for proton

increases with energy for a the so-called

with the atomic mass number of the particle.

with curves to show the expected

protons,

maximum

but the rate of increase,

in the elongation

change in composition,

which

rays relative to an extragalactic

rate above lo6 GeV

may result from depletion component,

presumably

protons.

,+

40 c* ..-a *--t&i&

300-

. &+-*-

FE

TOWARD FE

flEASIREDAWOR IO

I

I

I

I

I

I

I

I

I

I02

K)3

104

105

106

107

108

109

0'0

10"

Eo GeVINUCLEUS

Fig.

Within

will permit

energy

dependence

energy

of the elongation

the very large aperture

definitive

air showers.

based on collider highest

Energy

the next few years,

experiment26 highest

12

of the Fly's Eye profiles

of the

of that data with model calculations

results Will give information

interactions.

rate ~XMAX)

studies on the cascade

Comparison

on both composition

of

rich in

and the

15oc

W. V. Jones / Very High Energy Cosmic Ray Events

3. ANOMALOUS

3.1.

INTERACTIONS

Apparent

threshold

around

100 TeV

The region of the "knee" in the primary with an apparent particles.27

for anomalous

Most of the anomalous

mountaintop energy

threshold

experiments

either direct

extrapolation

interactions energies in either

in interaction

interactions.

described

models,

exhibit

data.

parameters,

interactions

The anomalous

features

is a change in the primary

the incident

flux.

composition,

The latter viewpoint

and transverse

momenta

interactions

and, in part, from speculations

or indirect)

manifestations

of quark-gluon

the

rather than to a change in

In fact, it is often argued that new physics

of high mrltiplicties

for investigating

for deciding whether

because there

is being observed

i.e., as heavier

associated

with nucleus-nucleus

that the anomalies

plasma

nuclei

stems, in part, from reports

may be (direct

(QGP) formation

in the

of two heavy nuclei.

3.2 Secondary

Three

not found

e.g., multiplicities,

composition.

collisions

but at higher

features

experiments

are not adequate

"knee" is related to a new physics threshold

dominate

from

and cross sections.

methods used by the mountaintop

energy

studies over the

Below about 100 TeV the

by standard

ray or accelerator

in most of the traditional

The indirect the highest

by large area

implies a result not expected

(-10%) of the interactions

low energy cosmic

momenta,

approximately

of the primary

of the lower energy data or from model calculations

are satisfactorily

are observed transverse

An anomaly

ideas about hadronic

a large subset

coincides

events have been reported

using air as the target

range 101' - 1015 eV.

using standard

spectrum

interactions

particle

categories

charge distribution (2) collimated unusually

nultiplicities

of so-called

anomalous

among the produced

jets of parallel

particles

energetic

large numbers of produced

rmltiplicities

are: (1) asymmetric

in mountaintop

experiments,

nuons deep underground,

particles

in interactions

and (3)

observed

at the

top of the atmosphere. The

"two-story"

on Mt. Chacaltaya atmosphere

emulsion in Bolivia

by the Brazil-Japan

can study both A-jets,

above the detector,

target of the upper-story reported

chamber employed

and C-jets,

chamber.

interactions

interactions

The widely

collaboration in the

in the pitch

publicized

by this group are A-jets with high multiplicities

Centaur0

(carbon)

events

of charged particles

151c

W. V. Jones / Very High Energy Cosmic Ray Events

= 75) with apparently no accompanying photons.'* Numerous mini-Centaur0 (Nch events, which are similar to Centaur0 except for smaller multiplicities (hch = 15), have also been reported The production

probability

to rise from -10% around other mountaintop consistent

for Centauros

experiments

is reported

(Mt. Fuji, Mt. Pamirs)

by the Chacaltaya Although

of Centauros

is also questioned

group

none of the

have seen events

they seem to confirm the mini-Centaur0

from the UA5 search for Centauro-like which

group.

300 TeV to -40% around 3000 TeV.

with Centauros,

The existence

by the Chacaltaya

events.

because of the negative

events in p'p collisions

29

result

at -150 TeV ,30

is only about a factor of two below the energy at which they were

observed

at Chacaltaya.

may be produced

in cosmic

Significant expected proton

advances

hadrons present ray collisions

In

jets of energetic

has not been adequately

particular,

emulsion

has been achieved

high energy

Although

their origin

muons may reflect the

chambers.2s16*!8

similar to that illustrated of rapidity

cosmic

and transverse

with

emulsion

plates,

inert plates of plastic,

(1) the primary

particle

with

of about 200 m2-sr-hr

particles

emanating

The measurements

for individual consists

lead, and/or iron.

is observed

detectors

For a typical

in the top few layers of the in the target, where the angles

cascades

are measured

and (3) the in the

calorimeter. Approximately which ended Therefore, exposure,

half of the JACEE exposure

(25 September,

in which

been observed.

available

approximately

Measurements

was obtained

in the last flight,

1983) just before the start of this conference.

data is currently

from only half of the accumulated

100 nucleus-nucleus

and analysis

of

of approximately

from the vertex are measured,

and angles of the photon-initiated

include

interactions

x-ray films, and plastic

is identified

(2) the first interaction

of the charged

in Fig. 13. yenta

ray nuclei inside the detector, which

300 layers of double-sided interleaved

cosmic ray interactions

so far in four flights of chambers with vertical

configuration

energies

data for single

of bundles of very

A total exposure

distributions

chamber,

in the searches for

with previous

the existence

groups of parallel

group is investigating

balloon-borne

event,

exist they rays or they

cosmic rays can be

employed

nuons seems to be verified.

explained,

cosmic

and decay of massive mesonS.

The JACEE

primary

of penetrating

detectors

The early results are consistent

decay.32

and nnilti-muon events.33

production

in the primary

with air nuclei.

in investigations

from the large, sophisticated

collimated

that if Centauros

It has been speculated31

may result from penetrating

interaction

events have

of these events are still underway.

152c

W. V. Jones / Very High Energy Cosmic Ray Events

Fig.

13

Schematic

diagram of

the J'ACEE emulsion

Generally

speaking,

multiplicity,

Table observed

priority

and highest

of four "high nultiplicity"

A microphotograph

is shown in Fig. 14.

Table

energy,

highest

charge primary events.

so far by JACEE.

Event Type‘

Vertex of Si + AgBr event

is given to the highest

1 lists the properties

Si + AgBr event,

Fig. 14

chamber

of the vertex of one of these, the

Such high rmltiplicities

High Multiplicity

1.

Energy/nucleon

B-A interactions

N

Events from JACEE

ch

Energy Density (GeV/fm3)

(TeV) Si + AgBr

4

1010

Fe + Pb

2

1050

3.0

100

760

4.5

1

>416

4.6

Ca + C Ar + Pb

not predicted of independent

by models that describe collisions

they seem to be consistent

are

B-A collisions

between nucleons, with predictions

4.0

as linear superpositions

i.e., wounded made within

nucleon models,

the framework

of

but

153c

W. V. Jmes / Very High Energy Cosmic Ray Events wounded

quark models.

This

is illustrated

in Fig. 15 which compares

- -

-7

-6

-5

-4

-3

-2

-I

0

2

I

PSEUDO-RAPIDITY Fig. 15

the pseudorapidity collision)

Pseudorapidity

energy

5

6

7

3

distribution

of Si + AgBr event

for the Si + AgBr event with the (central of the wounded nucleon model (WNM) of Bialas et al. 35 and

model

(MCM) of Kinoshita

The most interesting central

4

TeV/n) TeV/n)

distributions

prediction

the rmlti-chain

3

MCM(5 WNM(5

density

et a1.36

feature of these high multiplicity (last column of Table l), which

several times the expected

critical

events is the

is calculated

value (0.6 - 1.5 GeV/fm~)

to be

for transition

from hadron matter to quark matter.3

3.3

Transverse

momenta

The high multiplicity average PTv

transverse

distribution

dashed

of neutral

respectively. exhibit

by JACEE also have abnormally

tPT> associated

for the Ca + C event is

lines indicate

descendents

events observed

momenta

the distributions

The other high multiplicity

in the range 600 - 700 MeV/c.

reproduce

the observed

data.

shown in Fig. 16.2

expected

pions produced with

even the MCM model, which accurately

with the secondary

high

particles.

The

The solid and

if the observed

gamma rays are

of 700 MeV/c and 400 MeVfc, events

listed in Table

Considering

predicted

1 also

these high PT values,

the high multiplicities,

cannot

154c

IV. V. Jones / Very High Energy Cosmic Ray Events

5-

,

,

(

,

,

,

,

,

,

,

-

700 MeV/c

----

4OOMeV.c

-

2 -

5 \ \

2 I

I

‘O 0

\ Lb&l,

III, 500

1000

pT, (GeV/c) Fig. 16

The inclusive

PT distributions

C + C interactions

Fig. 17

PT

PT

distribution

of Ca - C event.

of gamma rays observed

by JACEE for p + C and

are shown in Figs. 17 and 18, respectively.37

distribution

P - C interactions.

for

Fig. 18

PT

distribution

interactions.

In both

for C - C

W. V. Jones / Very High Energy Cosmic Ray Events figures

the solid line represents

the normal exponential

155C

distribution

with

= l/2 = 200 MeV/c. The proton interactions are in good agreement tPTr' with the normally expected distribution, but the carbon interactions have a high PT tail Similar

(PT_, - 500 MeV/c)

two-component

interactions

observed

superimposed

distributions

on the normal distribution.

have been reported for other heavy nuclei

by JACEE.38

High PT tails have been reported for many years observations

based on direct measurements

as on indirect air showers.4o probably

measurements Enhanced

reflects multiple

constituents

the production

of projectile

with multicores

in extensive

in B-A collisions

constituents

Fermi motion inside the nuclei. 41

hand, the large PT associated indicates

chambers, 1~2B*3g as well

muons32 and rmlti-cores

of large PT secondaries

scattering

and, perhaps,

in emulsion

of underground

production

in other cosmic ray

off target

On the other

in air showers most l'ikely

and decay of massive mesons in the early stage of

shower development.

3.4

Cross sections

Two distinctly sections

different

are the so-called

designates

collimated

manifestations

of anomalous

"long flying component"

bundles of particles

much less than that of hadronic

cascades,

The

short interaction

long flying component

studying

cascade profiles

as a cluster eV.

and "anomalons".

with attenuation

projectile

has been observed

in large ionization

fragments with

only in mountaintop calorimeters.

It is interpreted

particle

for this phenomenon, production. 43

verification

Bevalac.45

The current

in experiments

The magnitude

Energy

interest

anomalously

in cosmic rays

in this effect stems from its

carried out with heavy ion beams at the

but it has not disappeared,

somewhat

as

and pro and con

are widespread.

Extensive anomalons

have been reported

of the effect seems to have diminished

more data has been accumulated, arguments

but it may be

has been around for only a few years,

short mean free paths of heavy ion fragments

reported

experiments

100 hadrons with a total energy around 3 x l@

the name anomalon

for almost three decades.44

mean

mean free paths.

of approximately

with charmed

Although

The former

in heavy absorbers

As yet there is no clear explanation

associated

cross

i.e., they have long interaction

free paths, while the latter denote relativistic anomalously

interaction

discussions

were presented

Heavy

of the available

data and possible

a few months before this conference

origins of at the Sixth High

Ion Study and Second Workshop on Anomalons held at the Lawrence

156~

W. V Jones / Very High Energy Cosmic Ray Events

Berkeley

Laboratory

first presented Conference organized exposed

(LBL).

after the LBL workshop

in Bangalore,

stack.

India.46

by the Joint Institute

nuclear emulsions

105 neon interactions charge

Therefore,

this report will be limited to new data at the 18th International

This data was collected of Nuclear Research

to the 4.1 ~eV/nucleon

beam of "Ne

until they interacted

A total of about 5000 interactions

observed,

(JXNR), Dubna, USSR, which

were found, and about lo4 projectile

3 6 Z s 9 were followed

and the average

Cosmic Ray

by a collaboration

at Dubna.

fragments

or left the emulsion

of the Z = 3 - 9 fragments

mean free path as a function

of x, the distance

Result of anomalon of individual

The experimenters data.

concluded

charges produced

data on fragments

4. Concluding

of different

effect was visible in their search on fragments advocates

of the analysis

of changes

In chemical

method used to

charges.

are indirect,

composition

differentiation

and changes

of

need to show

remarks

As long as cosmic ray measurements effects

search on fragments

result , anomalon

that the effect is not merely an artifact combine

from its point of emission.

to report an anomalon

a negative

type the

charges Z = 3 - 9.

that no anomalon

Since this first experiment

individual

were

mean free path for each element was determined.

The JINR data are given in Fig. 19, which shows for each fragment

Fig. 19

About

with

between

in the properties

of

157c

W. Cr.Jones / Very High Energy Cosmic Ray Events

nuclear

interactions

will

require several

beam can be defined or the details of nuclear then understanding

the other would

The most pressing in the spectrum

follow

on high energy

that depends

important

interactions

composition effects,

simply on magnetic

to measure

can be specified,

in a rather straightforward

is really due to propagation

a flux modulation especially

question

If either the cosmic ray

iterations.

the energy spectra

is whether

manner. the "knee"

i.e., whether

rigidity.

it reflects

Therefore,

directly

it is

over the energy

range 1014 - 1016 eV. The evidence energies showers

that particle

around

i.e., that particle

may be wrong,

to 1Ol6 eV and beyond. unusual

behavior

proton dominant

characteristics

like that observed

might be produced

(electrons,

methods would

in the primary

flux would

at higher energies.

the correct

propagation

evidence

for a different

would

be consistent

the spectral

features

in a

On the other

in the

then our standard energy

primary energy (free quarks,

in the spectrum.

consideration,

A significant

assignments.

anomalons,

photons)

Photons,

because the 3 OK microwave

around

1015 eV, with the opacity

fraction

of photons

in the high

at higher energies.

scenario,

of nuclear

galactic

smoothly

produce a break in the spectum and affect the

rate measurements

characteristics

air

does not indicate

If the energy deposition

becomes opaque to photons

flux would

may not extrapolate

rmons) changes,

also be reflected

decreasing

Whatever

energies.

exotic components

radiation

at

of extensive

at low energies.

result in erroneous

of abundant

background

elongation

as expected

by a change in the interaction

hadrons,

have been given serious

energy primary

physics

data from the jSp collider

above accelerator

The presence

especially,

However,

flux mixture

modes

determination

are not behaving

at a level capable of explaining

hand, the features

traditional

interactions

1014 - 1016 eV implies that our interpretation

it seems remarkable

interactions

effects

are observed

also change.

Perhaps

mode of interaction

with some of the current

that changes

in the

at just the energy where

this should be viewed as

restricted

to heavy nuclei, which

speculations

about QGP formation.

References 1)

K. Ribicki,

Nuovo Cimento

28 (1963) 1437.

2)

T. H. Burnett,

3)

See, for example, the extensive work in: Proceedings of the Bielefeld Workshop on Quark Matter and Very High Energy Heavy Ion Collisions, eds. M. Jacob and H. Sat2 (World Scientific Publishing Co., Singapore, 1982); and Proceedings of Session on Heavy Ions, Mariond Conference, Phy. Rep. -88 (1982) 379.

et al., Phys. Rev. Lett. 50 (1983) 2062.

W. V. Jones / Very High Energy Cosmic Ray Events

IS8C

4)

Presented by T. Saito for the JACEE Collaboration, JACEE Experiment, this volume.

New Phenomena

in the

5)

J. A. Simpson, Elemental and Isotopic Composition of the Galactic Cosmic Rays, in: Annual Review of Nuclear and Particle Science, Vol. 33, eds. J. D. Jackson, H. E. Gove, and R. F. Switters (Annual Reviews, Inc., 1983) p. 323.

6)

N. L. Grigorov, et al., 12th International (University of Tasmania, 1971) p. 1746.

7)

J. Linsley, Very High Energy Cosmic Rays, in: Origin of Cosmic Rays, eds. G. Setti, G. Spada and A. W. Wolfendale (Il.Reidel, Dordrecht, Holland, 1981) p. 53.

8)

M. LaPointe

9)

R. A, Antonov and I. P. Ivanenko, Vol. 8 (Munich, 1975) p. 2708.

Cosmic Ray Conference,

Vol. 5,

et al., Can. J. Phys. 46 (1968) p. 568. 14th International

Cosmic Ray Conference,

10) M. Simon et al., 16th International Cosmic Ray Conference, 1979) p. 346; Astrophys. J. 239 (1980) 712.

Vol. 1 (Kyoto,

11) J. A. Goodman et al., Cosmic Rays and Particle Physics, AIP Conference Proceedings No. 49, ed. T. K. Gaisser (American Institute of Physics, 1979) p. 1; Phys. Rev. Lett. 42 (1979) 854. 12) A. M. Hillas, Cosmic Rays and Particle Physics, AIP Conference Proceedings No. 49, ed. T. K. Gaisser (American Institute of Physics, 1979) p. 373. 13) G. Cunningham, 14) B. Peters,

et al., Astrophys.

Nuovo Cimento

15) V. K. Balasubrahamanyan 16) T. H. Burnett,

J. 236 (1980) L71.

22 (1961) 800. and 3. F. Ormes, Astrophys.

J. 186 (1973) 109.

et al., Phys. Rev. Lett. 51 (1983) 1010.

17) G. 8. Yodh, Composition of Cosmic Rays at High Energies, Spring Meeting of the American Physical Society (Baltimore, 1981) Invited talk - unpublished. 18) T. H. Burnett, et al., Proceedings of the 1982 DPF Summer Study on Elementary Particle Physics and Future Facilities, eds., R. Donaldson, Gustofson, and F. Paige (Division of Particles and Fields, American Physical Society, 1982) p. 641.

19)

S. M. Astley, et al., 17th International (Paris, 1981) p. 156.

20)

A. M. Hillas, Proceedings of the Cosmic Ray Workshop, (University of Utah, 1983) p. 1.

21)

C. J. Bell et al., 13th International Cpsmic Ray Conference, (University of Denver, 1973) p. 2525.

221

T. K. Gaisser

Cosmic Ray Conference,

Vol. 2

ed. T. K. Gaisser

Vol. 4

et al. Rev. Mod. Phys. 50 (1978) 859.

23) J. Linsley, 15th International Bulgaria, 1977) p. 89.

Cosmic Ray Conference,

vol.

12 (Piovdiv,

R.

159c

UJ.V. Jones / Very High Energy Cosmic Ray Events

24)

J. Linsley

and A. A. Watson,

Phys. Rev. Lett. 46 (1981) 459.

25) G. B. Yodh, XIII International Symposium (Volendam, The Netherlands, 1982).

on Multiparticle

Dynamics

26) R. Cady et al. Proceedings of the 1982 5PF Summer Study on Elementary Particle Physics and Future Facilities, eds. R. Donaldson, R. Gustofson,and F. Paige (Division of Particles and Fields, American Physical Society, 1982) p. 630. 27) F. Halzen

and H. C. Liu, Phys. Rev. Lett. 48 (1982) 771.

28) See, for example,

C. M. G. Lattes et al. Phys. Rep. C65 (1980) 151.

29) A. S. Borisov et al., Mini-Centaur0 Type Events in Pamir Experiment in: Workshops on Cosmic Ray Interactions and High Energy Results, ed. C. M. G.Lattes (Universidade Estadual de Campinas, Brazil, 1982) p. 445. 30) K. Alpgard

et al. Phys. Lett. 8115

31) See, for example, 2353.

J. 5. Bjorken

(1982) 65.

and L. McLerran,

Phys. Rev. 0 20 (1979)

32) R. M. Bionta et al. Workshop eds. M. L. Cherry, K. Lande, Pennsylvania, 1982) p. 339.

on Very High Energy Cosmic Ray Interactions, and R. I. Steinberg (University of

33) M. L. Cherry et al. Workshop eds. M. L, Cherry, I(. Lande. Pennsylvania, 1982) p. 278.

on Very High Energy Cosmic Ray Interactions, and R. I. Steinberg (University of

34) Y. Muraki, Workshop on Very High Energy Cosmic Ray Interactions, eds. M. L. Cherry, K. Land@, and R. I. Steinberg (University of Pennsylvania, 1982) p. 261. 35) A. Bialas

et al. Nucl. Phys. Blll

36) K. Kinoshita

(1976) 461.

et al. Z. Phys. C8 (1981) 205.

37) T. H. Burnett, et al. 18th International (Bangalore, India, 1983) p. 214.

Cosmic Ray Conference,

Vol. 5

38) T. H. Burnett et al. New Events Types in a Balloon-Borne Cosmic Ray Experment, in: Proton-Antiproton Collider Physics, AIP Conference Proceedings No. 85 (American Institute of Physics, New York, 1982) p. 552. 39) Y. Sato et al. J. Phys. Sot. Japan 41 (1976) 1821. 40) C. 8. A. McCusker,

Phys. Rep. 2OC (1975) 229.

41) See, for example, J. Cronin et al. Phys. Rev. 5 11 (1975) 3105; L. Kolberg et al. Phys. Rev. Lett. 38 (1977), 670; C. Bromberg et al, Phys. Rev. Lett. (1979) 1202. 42) V. I. Yakovlev et al. 16th International (Kyoto. 1979) p. 59.

Cosmic Ray Conference,

Vol. 6,

43) V. 1. Yakovlev et al. 18th International Cosmic Ray Conference, Vol. 5 (Bangalore, India, 1983).abstract, p. 102. Paper to appear in Late Volume.

160~

44)

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See, for example, A. Milone, Nuovo Cimento Can. J. Phys. 35 (1968) 343.

45) E. M. Friedlander

Suppl.

12 (1954) 354; B. Judek,

et al. Phys. Rev. Lett 45 (1980) 1084.

46) Presented by R. Holynski for JINR Collaboration, 18th International Cosmic Ray Conference (Bangalore, India, 1983). To appear in Late Volume.