Results on hadron-nucleus interactions from the Japanese-American Cooperation Emulsion Experiment experiment are presented. Angular distributions for charged particles, and angular and transverse momentum spectra for photons have been measured for a sample of events with sigma epsilon sub gamma. Results on central rapidity density and transverse energy flow are discussed

Burnett, T. H.

Dake, S.

Fuki, M.

Gregory, J. C.

Hayashi, T.

Holynski, R.

Iwai, J.

Jones, W. V.

Jurak, A.

Lord, J. J.

English

NASA Technical Reports Server

76 HE 1.2-11
NUCLEON-NUCLEUS INTERACTIONS FROM JACEE
The JA CEE Collaboration:
T. H. Burnett h, S. Dake b, M. Fuki c, J. C. Gregoryg, T. Hayashig, R. Holynski ',i,
J. Iwai h, W. V. Jones e, A. Jurak e,i, J. J. Lord h, O. Miyamura d, T. Ogata a,
A. Olszewski e,i, T. A. Parnell/, T. Saito a, S. Strausz h, M. Szarska e,i,
T. Tabuki a, Y. Takahashi I, Y. Tominaga _, B. Wilczynska i,
J. P. Wefel', R.J.Wilkes h, W. Wolter i, B. Wosiek e,i
a) Institute for Cosmic Ray Research, Tokyo; b) Kobe University; c) Okayama
University of Science; d) Osaka University; e) Louisiana State University; f) NASA
Marshall Space Flight Center; g) University of Alabama, Huntsville; h) University
of Washington; i) Institute for Nuclear Physics, Krakow.
ABSTRACT
Results on hadron-nucleus interactions from the JACEE experiment are
presented. Angular distributions for charged particles, and angular and
transverse momentum spectra for photons have been measured for a sam-
ple of events with EE.f> 1 TeV. Results on central rapidity density and
transverse energy flow are discussed.
1. Introduction
JACEE (Japanese-American Cooperative Emulsion Experiment) was organized
to study cosmic ray nucleus spectra and interactions at total energies approaching
100 TeV. The use of conventional emulsion chamber techniques permits the obser-
vation of secondary charged particles and individual high energy gamma rays. The
results presented here were obtained from a series of balloon flights at 3.5-8 g/cm 2
altitudes 1.
The apparatus used in the experiment has been described in detail elsewhere _.
All emulsion plates are made from 500_800 #m acrylic bases, coated on both sides
with Fuji emulsion. Incident particles are identified in the primary charge detector
section using grain, gap and delta-ray counts from thick (150_200 #m ) emulsion
layers, as well as pit measurements from CR39 etchable plastics. Charge resolution
is typically 0.2,,,2.0 units. The target section contains thin (50-75 #m ) emulsion
plates interleaved with acrylic or Fe target sheets. Thick emulsions and CR39 sheets
are inserted at intervals to permit identification of projectile fragments. Interactions
occuring in the t_pper Pb layers of the calorimeter can also be fully analyzed. The
spacer section permits gamma rays to diverge before reaching the calorimeter sec-
tion, so that individual photon cascades can be observed.
The calorimeter contains ,-,5 vertical radiation lengths of Pb interleaved with
18-20 layers of emulsion plates and x-ray films. Cascades of energy >300 GeV make
spots visible to the naked eye in the x-ray films, which serve both as threshold
detectors and as templates for locating events in the emulsions. In addition, den-
sitometric measurements in x-ray films provide an estimate of the shower energy.
https://ntrs.nasa.gov/search.jsp?R=19850027556 2020-03-20T17:22:20+00:00Z
HE i.2-11
77
Once an event has been located, a region of diameter 1-2 mm (depending upon
vertex height) around the event axis is scanned for lower energy cascades.
Accurate energy determinations are made by performing track counts in the
emulsion layers and comparing the results with calibration curves obtained from
analytical shower theory calculations 3 and monte carlo simulations 4 which have
been checked by accelerator calibration experiments s. The error in a single cascade
energy measurement is --_20%. The directly measured event energy parameter is
I]E.t, the total energy observed in the electromagnetic calorimeter. The primary
energy E0 can be estimated from _Evby using the gamma-ray inelasticity factor k 7
derived from measurements on protons at Fermilab s, and independently from the
charged particle angular distribution using the Castagnoli method.
2. Proton-Nucleus Interactions
Charged track angles are measured relative to the energy-weighted center of
the event. Interactions occuring in acrylic base or target plates are assumed to be
on carbon targets. Angular distributions are normally presented in terms of the
pseudorapidity, r/- -loge tan(0/2). In order to combine events of different energies,
one can define a normalized pseudorapidity parameter, _?*= -lOglotan(]DET*O). The
normalized log tan 0 distributions for nucleon interactions in C and Pb are shown
in Fig. 1. For this sample, _E_> 1 TeV and <_2E7>=4.9 TeV (carbon) and 3.5
WeV (Pb).
The central pseudorapidity density Pc for each event has been estimated by
excluding the forward 1.5 rapidity units (projectile fragmentation region) and cal-
culating dn/drl over the next 2 rapidity units. In Fig. 2 we plot < Pc > versus the
target mass A. The data are well represented by the relation < Pc >= kA°'31.
For photons observed in the calorimeter, transverse energy flow as a function of
rapidity y can be analyzed by defining an integral transverse energy flow parameter,
f(y) = _ Eti
yi>y
where Eti = Eisin(Oi). Plotting F(y) vs r/for individual events, and excluding the
low=y region where detection bias may be present, one finds that F(y) can be well
represented by the form F(y) _ e -by. The fitted values for the slope parameter
b have a bimodal distribution shown in Fig. 3, with about 15% of the events
displaying a significantly steeper slope than the rest. In Fig. 4a we show several
, typical events displaying large b; the low-b events shown for comparison in fig 4b
have been chosen to have a similar distribution of target mass and I]E7. The data
in Fig. 4 have been displaced vertically for clarity.
=
3. Acknowledgements
This work supported in part by DOE, NSF and NASA in the US, and JSPS in
Japan.
78 HE 1.2-11
4. References
1. T. Burnett, et al, paper HE-1.4-4, this conference.
2. R.W. Huggett, et al, 17th Int. Cosmic Ray Conf. (Paris), 8, 80 (1981).
3. J. Nishimura, Handbuch der Physik 46/2, 1 (1967).
4. S. Dake, private communication.
5. N. Hotta, et al, Phys. Rev. D22, 1 (1980).
6. S. Dake, et al, 15th Int. Cosmic Ray Conf. (Plovdiv), 7, 322 (1977).
5. Figure Captions
1. Normalized angular distributions for charged tracks observed in p-Pb interac-
tions (solid line) and p-C interactions (dashed line). The normalized pseudorapidity
parameter is defined as r/* = -logl0tan(_E_*8).
2. Central pseudorapidity density Pc versus target mass A. Interactions in plastic
and emulsion are taken to be on A=12 and 82 respectively. The solid line shows
the results of a fit to < Pc >"_ A 6, with t_=0.31.
3. Distribution of fits to slope parameter b in the relation F(y) _ e-by. See text
for definition of the integral transverse energy flow parameter F(y).
4. Plots of the integral photon transverse energy flow F(y) for individual events
a) with slope parameter b > 1.25 and b) with b < 1.25. The events have been
displaced vertically for clarity; the scales shown apply to the lowest data set.
o
o j
-] ----l
ea
° i I I i i
-3 -2 -I o t 5 lO 50 1_0 500 ,,,
ETAN A
Figure 1 Figure 2
.5 1 1.5 2 
b 
Figure 3 
6 7 8 9 6 7 8 9 
V v ' * .  
Figure  4 


Nucleon-nucleus interactions from JACEE

Nucleon-nucleus interactions from JACEE

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