2nd International Workshop on the critical point and the onset of deconfinement
Charged mesons in Au+Au interactions at 62.4 AGeV
Ionut Arsene for the BRAHMS Collaboration University of Oslo, Norway
University of Bucharest, Romania
2nd International Workshop on the critical point and the onset of deconfinement
Experimental overview (1)
Broad RAnge Hadron Magnetic Spectrometer
Two small solid anglespectrometers (FS and MRS)that can rotate from 2.3 to 30 degrees (FS) and from 30 to 90 degrees (MRS) provide very good PID over a wide range of rapidity and Pt.
2nd International Workshop on the critical point and the onset of deconfinement
Experimental overview(2)
Top: MRS PID curves. The pions/kaons are well separated up to 2 GeV/c, and kaons/protons up to 3-4 GeV/c
Bottom: PID plot from the RICH detector. RICH extends the particle identification to ~10GeV/c (pi/K) and ~25 GeV/c (K/p).
2nd International Workshop on the critical point and the onset of deconfinement
Data and phase space coverage
Due to the limited acceptance of the detectors, only a part from the phase space is covered.
2nd International Workshop on the critical point and the onset of deconfinement
Pt spectra (1)
The Pion Pt spectra is well fitted with a power law function of the form f(Pt) ~ (1+Pt/P0)^{-r}
The fitted exponent decrease with centrality.
2nd International Workshop on the critical point and the onset of deconfinement
Pt spectra (2)
Kaons Pt spectra at mid-rapidity.
The spectra is fitted with a Boltzman function.
2nd International Workshop on the critical point and the onset of deconfinement
Mean Pt for pions and kaons
<Pt> constant around mid-rapidity and slightly decrease at forward rapidities.
<Pt> at y=0: pions: ~425 MeV/c kaons: ~650 MeV/c Bottom figure: BRAHMS
200 AGeV
2nd International Workshop on the critical point and the onset of deconfinement
Particle ratios (1)
the pi-/pi+ ratio is ~1 on the entire rapidity range;
the K-/K+ ratio is ~0.9 around mid-rapidity and decrease at forward rapidities.
2nd International Workshop on the critical point and the onset of deconfinement
Particle ratios (2)
pi-/pi+ and K-/K+ ratios as a function of Pt.
2nd International Workshop on the critical point and the onset of deconfinement
Particle ratios (3)
Energy dependence of K/pi ratio at midrapidity (left)Energy dependence of K/pi ratio at midrapidity (left) Rapidity dependence of K/pi ratios (right)Rapidity dependence of K/pi ratios (right) The error bars in the right figure are statistical only.The error bars in the right figure are statistical only.
2nd International Workshop on the critical point and the onset of deconfinement
Particle ratios (4)
Preliminary K/pi ratios as a function
of Pt. K/pi ratio increase with
transverse momentum. At 1 GeV/c the ratios
are ~0.4.
2nd International Workshop on the critical point and the onset of deconfinement
K/pi ratios at 200 AGeV
Midrapidity & Forward rapidity K/pi ratio ~0.4 at 1GeV/c and ~ 0.7 at 2 GeV/c
2nd International Workshop on the critical point and the onset of deconfinement
Energy dependence of widths
Landau hydrodynamics Gaussian rapidity
distribution The widths
depend only on c.m. energy
L.D. Landau, Izv. Akad. Nauk SSSR 17 (1953) 52P.Carruthers, M.Duong-van, PRD 8 (1973) 859
2nd International Workshop on the critical point and the onset of deconfinement
Summary
Pt spectra for mesons Gaussian rapidity distributions 4 yields C.M. energy dependence of widths and K-/K+ ratios Pt dependence of the and K-/K+ ratios Rapidity dependence of K/ ratios Pt dependence of K/ratios Energy dependence of K/ ratio (total yields)
2nd International Workshop on the critical point and the onset of deconfinement
The BRAHMS Collaboration
I.Arsene[12,10],I.G. Bearden[7], D. Beavis[1], C. Besliu[10], Y. Blyakhman[6], J.Brzychczyk[4], B. Budick[6],H. Bøggild[7] ,C. Chasman[1], C. H. Christensen[7], P. Christiansen[7],
J.Cibor[4],R.Debbe[1],J. J. Gaardhøje[7],M. Germinario[7], K. Hagel[8], O. Hansen[7], H. Ito[11], E. Jacobsen[7], A. Jipa[10], J. I. Jordre[10], F. Jundt[2],
C.E.Jørgensen[7], E. J. Kim[5], T. Kozik[3], T.M.Larsen[12], J. H. Lee[1], Y. K.Lee[5], G. Løvhøjden[2], Z. Majka[3], A. Makeev[8], B. McBreen[1], M. Murray[8], J. Natowitz[8], B. Neuman[11],B.S.Nielsen[7], K. Olchanski[1], D. Ouerdane[7], R.Planeta[4], F. Rami[2],
D. Roehrich[9], C.Ristea[7], O.Ristea[10], B. H. Samset[12], S. J. Sanders[11], I. S. Sgura[10], R.A.Sheetz[1], Z.Sosin[3], P. Staszel[7], T.S. Tveter[12], F.Videbæk[1], R. Wada[8] ,A.Wieloch[3],Z. Yin[9]
[1] Brookhaven National Laboratory, USA, [2] IReS and Université Louis Pasteur, Strasbourg, France
[3] Jagiellonian University, Cracow, Poland, [4] Institute of Nuclear Physics, Cracow, Poland[5] Johns Hopkins University, Baltimore, USA,
[6] New York University, USA[7] Niels Bohr Institute, Blegdamsvej 17, University of Copenhagen, Denmark
[8] Texas A&M University, College Station. USA, [9] University of Bergen, Norway
[10] University of Bucharest, Romania, [11] University of Kansas, Lawrence,USA
[12] University of Oslo Norway