The Japanese-American Cooperative Emulsion Experiment (JACEE) have been investigating high energy nuclear interactions of cosmic ray nuclei by means of balloon-borne emulsion chamber. Current exposure parameters are listed. Analysis of the last two experiments (JACEE4 and JACEE5) are still in progress. A result of semi-inclusive analysis of a sample set of central collision events is presented here, concerning multiplicity, rapidity fluctuation for extremely high multiplicity events and correlation between transverse momentum and estimated energy density

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

164
HE 1.4-4
Nucleus-Nucleus Interaction above Several Hundred GeV/n
The JACEE Collaboration
T.H.Burnett(h), S.Dake(b), M.Fuki(c), J.C.Gregory(g), T.Hayashi(g),
R.Holynski(e,i), J.lwai(h), W.V.Jones(e), A.Jurak(e,i), J.J.Lord(h),
O.Miyamura(d), H.Oda(b), T.Ogata(a), T.A.Parnell(f), T.Saito(a),
S.Strausz(h), M.Szarska(e,i), T:Tabuki_a_, Y.Takahashi(f),
T.Tominaga(d), J.W.Watts(f), J.P.Wefel(e), B.Wilczynska(i),
R.J.Wilkes(h), W.Wolter(e,i), and B.Wosiek(e,i).
(a) Institute for Cosmic Ray Research, University of Tokyo, Tokyo, Japan
(b) Department of Physics, Kobe UniVersity, Kobe, Japan
(c) Department of Physics, Okayama University of Science, Okayama, Japan
(d) Department of Applied Mathematics, Osaka University, Osaka, Japan
(e) Department of Physics and Astronomy, Louisiana State University,
Baton Rouge, Louisiana, USA
(f) Space Science Laboratory, NASA Marshall Space Flight Center,
Huntsville, Alabama, USA
(g) Department of Chemistry, University of Alabama in Huntsville,
Huntsville, Alabama, USA
(h) Department of Physics, University of Washington, Seattle,
Washington, USA
(i) Institute of Nuclear Physics, Krakow, Poland
1. Introduction
At an extreme condition of high pressure, constituents of hadron,
quark and qluon, are expected to be deconfined and then transit into a
plasma phase(Quark-Gluon-Plasma). Such an extreme condition can be
realized through high density hadronic matter and at present, we have no
means other than to observe signals from such state through high energy
heavy ion collision[7].
The Japanese-American Cooperative Emulsion Experiment( JACEE ) have
been investigating high energy nuclear interactions of cosmic ray nuclei
by mean of balloon-borne emulsion chamber. Current exposure parameters
are listed on Table I. Analysis of last two experiments( JACEE4 and JACEE5
) are still in progress. The quasi-inclusive
characteristics of nucleus-nucleus collisions Flight Altitude Time Area
above TeV/n region obtained by first three (g/cm 2) (hrs)(m 2 )
experiments and some anomalous phenomena
_Qbserved in our experiment had been already JACEEO 8.0 29.0 0.20
reported[l,2]. We present here, a result of JACEEI 3.7 26.5 0.80
semi-inclusive_analysis of sample set of JACEE2 4.0 29.6 0.80
central collision events, concerning to (JACEE3 5.0 39.0 0.25)
multiplicity, rapidity fluctuation for JACEE4 4.5 56.0 0.80
extremely high multiplicity events and JACEE5 5.0 15.0 0.80
correlation between transverse momentum and
estimated energy density. Table 1. Exposure Parameter
2. Method
The emulsion chamber have primary, target, space and calorimeter
*) Address for correspondence: Institute for Cosmic Ray Research,
University of Tokyo, 3-2-1, Midori-cho, Tanashi-shi, Tokyo 188, JAPAN
https://ntrs.nasa.gov/search.jsp?R=19850027579 2020-03-20T17:21:21+00:00Z
165
HE 1.4-4
sections. The primary section contains emulsion layers of high and low
sensitivity(Fugi ET7B and ET-6B), coated 0.150-0.200 mm thick on both
side of 0.800 mm acrylic base, and CR-39, where primary charge is
measured by grain counting, delta ray counting on emulsion and etched
pitch rate in CR-39, errors contained in charge measurement being O.2e,
O.5e and le, respectively. The target section contains sandwich of 2.0 mm
thick acryl plate and thin (0.050 - 0.075 mm ) doubly coated emulsion
plates to follow secondary tracks from nuclear collision, thick emulsion
plates are also placed in this section for measurement of heavy fragment
charge, the spacer of honeycomb is located at the downstream thereof to
separate secondary particle. The calorimeter contains 1.0 - 2.5 mm thick
lead plates, X-ray films and thin emulsion plates, where gamma ray, most
of all from T°, makes electron cascade shower which is visible on X-ray
films for high energy event. The shower energy is measured by electron
counting method for the most of events which shower cores are separated
enough for electron counting, error in energy measurement for shower core
being 22%. Emission angle Of charged particle is measured by track
position on emulsion plates. Relative error in angle measurement is less
than 0.I in unit of pseudo-rapidity. Transverse momentum of shower core
is obtained from the energy and an angle measured from energy weighted
center of shower cores. The average transverse momentum of an event is
estimated by fitting of the distribution assuming exponential function.
The above procedure with energy measurement overestimates average Pt by
3-7% in average depending on observed gamma ray multiplicity. In
addition to this, one should note that, in exclusive analysis, event to
event fluctuation may be larger than the above error. As an estimation of
Pt of T ° from observed gamma ray Pty, <2Pty> is used for conventionally,
which procedure, from kinematic reason, overestimates 43%, 5% and 0.9 %
for _0 Pt 100, 300 and 700 MeV/c, respectively, and average Pt of pion
in the concerning energy region is known to be over 340 MeV/c[4]. For the
case that shower cores overlap with each other in the most forward region
depending on vertex location in the calorimeter, the transverse momentum
of secondary _0 is estimated from shower transition in forward restricted
angular region, since profile of such superposed shower is determined by
both angular and energy/Pt distribution of the secondary. Some events in
calorimeter permit measurement with each core separated at large angular
region probably due to their very high transverse momenta. In such case,
Pt of shower core should be regarded as that of _0 For the primary
energy estimation, the mean Castagnoli method as well as total radiated
cascade energy ZEy are used.
3. Results
Tables 2-a and 2-b Event Type E0 Nch 2PrY pt_0(cone) dn/dn[nc #
shows seven high (TeVl,) (_Vlc) (_Vlc)
....+300
multiplicity events of Ns Ca + Ph 1.5 _u_u50 0.95±0.31 0.55±0.05 258±12 A88
greater than 400 and of two sl + Ag/Br 4.1 i010±30 0.55±0.05183±10 _3
events of light nucleus with Ca + C i00. 760±30 0.525±0.04 81±i0 G00
Carbon target events. Three
Si + Pb 4. 780 not yet not yet B02
events in Table 2-a were
Ca + Pb 0.5 670±40 not yet 142±8.4 H60
already reported, where
Ca + Pb 1.8 457 2._0.i 100±16 D27
observed multiplicity can be
interpreted within Ar + Pb 1.0 416 i._0.2 134±8 C27
calculation ofMulti-Chain- Table 2-a. High multiplicity events( Nch > 400 ) in JACEE
ModeI(MCM)[3]. And also, all
166
HEI.4-4
observed multiplicity in
Table 2-a are still within Event Type E 0 Neh 2P_ dn/dBlnc Nch(MCM) D
prediction at impact parameter Li + C 15. 217 0.76±0.08 37.5±4.3 154 37
b=O fro,( maximum predictable He + C 20. 156 0.62±0.08 26.5±3.6 122 30
multiplicity is not necessary
Table 2-b. Unit same as Table 2-a. 6 and 7-th column
realized at b=O fm for heavy are model calculation by MCM at b-0 fm.
nuclei, A > 16, depending on
nuclear density distribution),
however events in Table 2-b are out of MCM calculation.
The averaged transverse momentum of listed events, which are
considered to be central collision, exhibit extremely high Pt values
comparing to interpolation value from CERN ISR and SPS collider
experiments[4].
We now estimate energy density of event, for which we use that was
proposed by Bjorken[5], as in the following.
e E / <Pt> 2 + m_ 2 "dn/dn]n c • 1.5/V,
where dn/dnJn c is a pseudo-rapidity density of charged particle at CMS
system, V being an interaction volume for which we choose V=C Amin 2/3,
C=2_. Amin is the minimum of Aproj and Atarget. In the case of heavy
fragment(s) existing in the secondary, mass number reduction is applied
for Aproj. Fig. 1 shows scatter diagram between estimated energy density
and Pt for which we used 2<Pty> for the most case, which procedure
does not significant influence on the result as previously mentioned, for
the events apparently giving 7 ° Pt, measured values are used as
themselves.
At present, pseudo-rapidity fluctuation analysis had been performed
for two high multiplicity events( GO and G3 ), wherein multiplicity and
its dispersion in windows of width 6 on pseudo-rapidity are estimated
from Independent Emission Model(IEM) of pure statistical assumption and
from MCM, respectively. Results is that both of event are favor for IEM
but for MCM, due to the observed fluctuation is not so large comparing to
MCM, events GO and G3 deviating 3o from MCM and within Io and 1.4o from
IEM, respectively.
Azimuthal angle 14 I ' ' I ' i_-----
distribution of four events
from high multiplicity 12
events(A88, GO, G3 and H66) ,JACEEheavy
aJACEE p.C(lO~100 T_)
are also analyzed by 10 * p_=540 GeV
Fourier transformation " "
method• Similar analysis 908
had been already proposed _ ' " " "m_L.S.
by F•Takagi on pseudo- _ .. "
rapidity distribution[6] v 0.6 • " . _ •• • •D
According to this analysis, . . ._ = _%.._,..._
three events (A88, G3 and 0A ....._" .
H60) exhibit dipole " ' = ".D
structure, which 02 e" "
probability is expected to -
I , i I I , 'be one event among several 0 01 to _0
ten to several hundred energydenslty((GeWf_)
events assuming independent
Fig.1 Correlation between energy density and Pt.
167
HE 1.4-4
emission of secondary, while event G3 is almost isotropic in azimuth.
4. Discussions and summary
As shown in Fig.l, the average transverse momentum seems to grow
rapidly over the energy density around 2 GeV/fm . Multiple scattering
effect for possible interpretation for this correlation does not describe
qualitatively. If the observed correlation is attributed to phase
transition of QGP, the observed characteristic energy density is
consistent with the predicted critical value for deconfinement of quark
and qluon at temperature around 200 MeV[7]. Though there still exists
ambiguity in quantitative estimation for energy density such as volume
estimation, the observed correlation characteristics might not change
substantially.
From the view point of multiplicity, MCM gives fairly good
estimation for high multiplicity events, however there still exist the
events above maximum prediction of MCM. In the lower energy region of 20-
60 GeV/n, there also observed extremely high multiplicity events from
minimum bias sample of Fe group primary[8]. Because of a freedom of
impact parameter, event to event analysis for multiplicity in nucleus-
nucleus collision can not result in fruitful conclusion. However, this
kind of analysis not only is a test for assumed conventional picture but
also gives a key to reveal a mechanism which determines a final state of
nuclear collision.
The present fluctuation analysis requires more statistics to get
constructive conclusion. The current result indicates that angular
distribution on pseudo-rapidity as well as on azimuth can not be
interpreted by simple superposition of nucleus-nucleus collisions for
some high multiplicity events.
While the present fluctuation analysis is related to many particles
correlation in final state, few particles correlation analysis of charged
particle is also possible from our data sample. Detail analysis and
discussions on this regard from a short range pair correlation is
presented in this conference[9].
Although there exists still theoretical ambiguity in final state
estimation from QGP, it seems that we might come close to QGP signal.
Acknowledgements
This work is supported in part in Japan by ICR, JSPS and the Kashima
fundation, and in part in the USA by DOE, NASA and NSF.
References
i. Proc. of 18-th ICRC, 5, 214, (1983); Recent review see
AlP Conf. Proc., No.123, 723(1984), and Proc. of Quark Matter '84.
2. Proc. of 18-th ICRC, 5, 218, (1983);
, T.H. Burnett et al., Phys. Rev. Lett., 50, 2062(1983)
3. K. Kinoshita et al., Zeit. fur Phys., C8, 205(1981)
4. G.Giacomelli et al., Phys. Rep., 55, No. 1(1979);
UAI Collaboration, Phys. Lett., l18b, 167(1982)
5. J. D. Bjorken, Phys. Rev., D27, 140(1983)
6. F. Takagi, Phys. Rev. Lett., 53, 427(1984)
7. E.V.Shuryak, Phys. Rep., 61C, 71(1980); M.Jacob et al., Phys. Rep.,
88C,(1982); Proc. of Quark Matter '83, Nucl. Phys., A418(1984)
8. The JACEE Collab., presented by S. Dake and B.Wosiek in this conference
9. The JACEE Collab., presented by Y. Takahashi in this conference


Nucleus-nucleus interaction above several hundred GeV/n

Nucleus-nucleus interaction above several hundred GeV/n

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server