Parallel Session (Hadron 1) 2/Dec/97 Quark Matter ‘97
Kaon and Proton Ratios from Central Pb+Pb Collisions
at the CERN SPS
Masashi Kaneta
for the NA44 collaboration Department of Physics,
Hiroshima University
① Introduction
② mT distributions of K and p from Pb+Pb
③ Particle ratios
④ Summary
e-mail: [email protected]
Masashi Kaneta / Hiroshima univ.
Parallel Session (Hadron 1) 2/Dec/97 Quark Matter ‘97
High energy heavy ion collision
Thermal freeze-out
Introduction
E x
p a
n s
i o
n
Tfo :~ 140MeV at SPS and AGS energies
Lots of hadrons are newly createdHuge number of collisions
Thermo-chemical model To describe the system
Masashi Kaneta / Hiroshima univ.
Parallel Session (Hadron 1) 2/Dec/97 Quark Matter ‘97
I.G.Bearden1, H.Bøggild1, J.Boissevain2, J.Dodd3,
B.Erazmus4, S.Esumi5,a, C.W.Fabjan6, D.Ferenc7,
D.E.Fields2, A.Franz6,b, J.J.Gaardhøje1, M.Hamelin10,
A.G.Hansen1, O.Hansen1, D.Hardtke8, H. van Hecke2,
E.B.Holzer6, T.Humanic8, P.Hummel9, B.V.Jacak2,c, R.Jayanti8,
K.Kaimi5, M.Kaneta5, M.Kopytine2,c, M.Leltchouk3,
A.Ljubicic Jr.7, B.Lörstad10, N.Maeda5,d, R.Malina6
M.Murray10, H.Ohnishi5, G.Paic4,6,
S.U.Pandey8,e, F.Piuz6, J.Pluta4, V.Polychronakos11,
M.Potekhin3, G.Poulard6, D.Reichhold8, A.Sakaguchi5,f,
J.Simon-Gillo2, J.Schmidt-Sørensen9, W.Sondheim2,
M.Spegel8, T.Sugitate5, J.P.Sullivan2, Y.Sumi5,
W.J.Willis3, K.L.Wolf10, N.Xu2,g and D. S. Zachary8
Now at Universität Heidelberg, Physikalisches Institut, 69120 Heidelberg, Germany.Now at Brookhaven National Laboratory, Upton, NY 11973, USA.Now at State University of New York, Stony Brook, NY 11794, USA.Now at Department of Physics, Florida State University, Tallahassee, FL 32306-3016, USA.Now at Wayne State University, Detroit, MI 48202, USA.Now at Department of Physics, Osaka University, Toyonaka, Osaka 560, Japan.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 Department of Physics, University of Lund, S-22362 Lund, Sweden.10 Texas A&M University, College Station, TX 77843, USA.11 Brookhaven National Laboratory, Upton, NY 11973, USA.
The NA44 Collaboration
a
b
c
d
e
f
g
Masashi Kaneta / Hiroshima univ.
Parallel Session (Hadron 1) 2/Dec/97 Quark Matter ‘97
Masashi Kaneta / Hiroshima univ.
Parallel Session (Hadron 1) 2/Dec/97 Quark Matter ‘97
PID
Masashi Kaneta / Hiroshima univ.
Parallel Session (Hadron 1) 2/Dec/97 Quark Matter ‘97
Acceptance
Masashi Kaneta / Hiroshima univ.
Parallel Session (Hadron 1) 2/Dec/97 Quark Matter ‘97
Selection of centrality
Masashi Kaneta / Hiroshima univ.
Parallel Session (Hadron 1) 2/Dec/97 Quark Matter ‘97
K-/K+ and p/p ratio as a function of PT
and centrality
Masashi Kaneta / Hiroshima univ.
Parallel Session (Hadron 1) 2/Dec/97 Quark Matter ‘97
mT distribution
Inverse slope [MeV] dN/dy
K+
K-
pp
237±3 21.3±0.8 238±3 11.5±0.4303±6 25.3±1.0281±8 1.64±0.09
systematic error: <4% for inverse slope <10% for dN/dy
centrality : top 8.5%
Masashi Kaneta / Hiroshima univ.
Parallel Session (Hadron 1) 2/Dec/97 Quark Matter ‘97
Effect for proton yield from weak decays
• Effectsof and + decay to proton spectra are estimated by a Monte-Carlo simulation (Also, antiparticle to antiproton)
– dN/dy and mT slope are referred from RQMD(V1.08) and experimental data
(NA49 coll., Nucl. Phys. A610 (1996) 188c)
Inverse slope [MeV] dN/dy
pp
331±10±11 20.1±1.2±1.3316±13±15 1.11±0.19±0.11
The error by correction reflected the result of increasing and decreasing the (++)/p ratio by a factor of 1.5
Masashi Kaneta / Hiroshima univ.
Parallel Session (Hadron 1) 2/Dec/97 Quark Matter ‘97
Strange neutral hadron gas model
s is given as a function of Tch and q for differents by numerical calculation. Tch, q : 5MeV step s : 0.05 step
s=1
Masashi Kaneta / Hiroshima univ.
Parallel Session (Hadron 1) 2/Dec/97 Quark Matter ‘97
Extract chemical freeze-out temperature and chemical potentials
Tch
q
s
s
= 155 ~ 170 MeV= 75 ~ 85 MeV= 22 ~ 31 MeV= 0.75 ~ 0.95
comparison of ratios from experiment with ratios from model
Masashi Kaneta / Hiroshima univ.
Parallel Session (Hadron 1) 2/Dec/97 Quark Matter ‘97
Comparison of Tch, q, s from Pb+Pb with those from other systems
The Tch and q in Pb+Pb are close to the values in S+A
Tch :q :s :
at SPS energies at AGS energies
155 ~ 200MeV 120 ~ 140MeV
60 ~ 120MeV 160 ~ 200MeV 3 ~ 40MeV 60 ~ 120MeV
Masashi Kaneta / Hiroshima univ.
Parallel Session (Hadron 1) 2/Dec/97 Quark Matter ‘97
Summary
• Collisions system dependence of Tch ,q
and s is less clear than dependence
• At SPS energies,
Chemical freeze-out temperature T
ch
> Tfo( ~ 140MeV)
s
Chemical freeze-out temperature and chemical potentials are extracted fromkaon and proton ratio in Pb+Pb collisions
Tch
q
s
s
= 155 ~ 170 MeV= 75 ~ 85 MeV= 22 ~ 31 MeV= 0.75 ~ 0.95
It is quite natural with view point of thermodynamics