particle ratios from central pb+pb collisions at the cern sps
DESCRIPTION
Particle Ratios from Central Pb+Pb Collisions at the CERN SPS. Masashi Kaneta for the NA44 collaboration Department of Physics, Hiroshima University. Introduction Particle Ratios Ratios as a function of centrality and P t Chemical property Thermal freeze-out Summary. - PowerPoint PPT PresentationTRANSCRIPT
INTERNATIONAL SYMPOSIUM ON STRANGENESS IN QUARK MATTER 1997
Particle Ratios from Central Pb+Pb Collisions
at the CERN SPS
Masashi Kaneta
for the NA44 collaboration
Department of Physics, Hiroshima University
① Introduction
② Particle Ratios
Ratios as a function of centrality and Pt
Chemical property
Thermal freeze-out
③ Summary
Masashi Kaneta / Hiroshima univ. 2
INTERNATIONAL SYMPOSIUM ON STRANGENESS IN QUARK MATTER 1997
I. G. Bearden1, H. Bøggild1, J. Boissevain2, J. Dodd3,
B. Erazmus4, S.Esumi5,A, C. W. Fabjan6, D. Ferenc7,
D. E. Fields2, A, Franz6, J.J.Gaardhøje1, O, Hansen1,
D. Hardtke8, H. van Hecke2, E. B. Holzer9,
T. Humanic8, P. Hummel9, B. V. Jacak2, R. Jayanti8,
M. Kaneta5, M. Kopytine2, M. Leltchouk3,
T.Ljubicic7, B. Lörstad10, N. Maeda5,B, A. Medvedev3,
M. Murray11, S. Nishimura5,C, H. Ohnishi5, G. Paic4,6,
S. U. Pandey8, F. Piuz6, J. Pluta4, V. Polychronakos12,
M. Potekhin3, G. Poulard6, A. Sakaguchi5,D,
J. Simmon-Gillo2, J. Schmidt-Sørensen10, W. Sondheim2,
M. Spegel9, T. Sugitate5, J. P. Sullivan2, Y. Sumi5,
W.J.Willis3, K. Wolf11, N. Xu2,E and D. S. Zachary8
A Now at Universität Heidelberg, Physikalisches Institut, 69120 Heidelberg, Germany.B Now at Department of Physics, Florida State University, Tallahassee, FL 32306-3016, USA.C Now at Institute of Physics, University of Tsukuba, Tsukuba, Ibaraki 305, Japan.D Now at Department of Physics, Osaka University, Toyonaka, Osaka 560, Japan.E Now at Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
1 Niels Bohr Institute, DK-2100 Copenhagen, Denmark.2 Los Alamos National Laboratory, Los Alamos, NM 87545 USA.
3 Department of Physics, Columbia University, New York, NY 10027, USA.4 Nuclear Physics Laboratory of Nantes, 44072 Nantes, France.
5 Hiroshima University, Higashi-Hiroshima 739, Japan.6 CERN, CH-1211 Geneva 23, Switzerland.
7 Rudjer Boskovic Institute, Zagreb, Croatia.8 Department of Physics, Ohio State University, Columbus, OH 43210, USA.
9 Technical University, A-1040, Vienna, Austria.10 Department of Physics, University of Lund, S-22362 Lund, Sweden.
11 Texas A&M University, College Station, TX 77843, USA.12 Brookhaven National Laboratory, Upton, NY 11973, USA.
The NA44 Collaboration
Masashi Kaneta / Hiroshima univ. 3
INTERNATIONAL SYMPOSIUM ON STRANGENESS IN QUARK MATTER 1997
•Particle ratios–Sensitivity to collision dynamics
–Check chemical equilibrium assumption
K-/K
+, p/p ratios
A Scenario
Collisions
Chemical equilibrium state?
Thermal equilibrium state
Freeze-out
Motivations
Masashi Kaneta / Hiroshima univ. 4
INTERNATIONAL SYMPOSIUM ON STRANGENESS IN QUARK MATTER 1997
Masashi Kaneta / Hiroshima univ. 5
INTERNATIONAL SYMPOSIUM ON STRANGENESS IN QUARK MATTER 1997
PID
• Selection between K and p
Masashi Kaneta / Hiroshima univ. 6
INTERNATIONAL SYMPOSIUM ON STRANGENESS IN QUARK MATTER 1997
NA44 acceptance
Masashi Kaneta / Hiroshima univ. 7
INTERNATIONAL SYMPOSIUM ON STRANGENESS IN QUARK MATTER 1997
Selection of centrality
Masashi Kaneta / Hiroshima univ. 8
INTERNATIONAL SYMPOSIUM ON STRANGENESS IN QUARK MATTER 1997
Ratios as a function of Pt and centrality
† Those ratios are measured at the downstream (~20m) of collision point.
A effect of decayed particles is included in it.
Masashi Kaneta / Hiroshima univ. 9
INTERNATIONAL SYMPOSIUM ON STRANGENESS IN QUARK MATTER 1997
Effect of decayed particles
• Tools– RQMD : y, pT distribution
– MC simulation : effect of acceptance
As first step, lambda decay effect to proton yield is studied
pass p,p,, through NA44 detectors
Example of Pt distribution
dN/dy: ±30%mt slope: ±10%As systematic error {
Correction factor for p/p ratio
Masashi Kaneta / Hiroshima univ. 10
INTERNATIONAL SYMPOSIUM ON STRANGENESS IN QUARK MATTER 1997
Strangeness neutral hadron gas
Masashi Kaneta / Hiroshima univ. 11
INTERNATIONAL SYMPOSIUM ON STRANGENESS IN QUARK MATTER 1997
Absolute ratio and ratio around mid rapidity
NA44 acceptance for Kaons and protons are around mid rapidity.
compare ratios as a function of rapidity and absolute ratios in RQMD.
NA44 preliminary
RQMD ver 1.08 (b<2fm)( average)
: ratios around the mid rapidity is the same with absolute ratio.
Kaons
protons : both ratios are close in the region y1.6.
Masashi Kaneta / Hiroshima univ. 12
INTERNATIONAL SYMPOSIUM ON STRANGENESS IN QUARK MATTER 1997
Comparison with model prediction
Masashi Kaneta / Hiroshima univ. 13
INTERNATIONAL SYMPOSIUM ON STRANGENESS IN QUARK MATTER 1997
Thermal freeze-out temperature
Masashi Kaneta / Hiroshima univ. 14
INTERNATIONAL SYMPOSIUM ON STRANGENESS IN QUARK MATTER 1997
SummarySummary
•Ratios–K
-/K
+ and p/p ratios are flat as a function of Pt
–Ratios are insensitive in the central region (top 8.5%)
•Chemical properties–Assuming the system is in
chemical equilibrium state
TemperatureTemperature TTch ch ~ 175MeV~ 175MeV
Chemical potentialChemical potential
qq ~ 80MeV, ~ 80MeV, ss ~ 30MeV ~ 30MeV
TTchch T Tf0f0
In Pb+Pb central collisions