Charged mesons in Au+Au interactions at 62.4 AGeV

1. 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

2. Experimental overview (1) Broad RAnge Hadron Magnetic Spectrometer Two small solid angle spectrometers (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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. Particle ratios (3) • Energy dependence of K/pi ratio at midrapidity (left) • Rapidity dependence of K/pi ratios (right) • The error bars in the right figure are statistical only. 2nd International Workshop on the critical point and the onset of deconfinement

11. 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

12. 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

13. 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) 52 P.Carruthers, M.Duong-van, PRD 8 (1973) 859 2nd International Workshop on the critical point and the onset of deconfinement

14. 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

15. 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 2nd International Workshop on the critical point and the onset of deconfinement