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Leptonic and Charged Kaon Decay Modes of the f meson Measured in Heavy-Ion Collisions Leptonic and Charged Kaon Decay Modes of the f meson Measured in Heavy-Ion Collisions at CERN-SPS A. Marín (GSI) Ceres Collaboration Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI)

Motivation Transition from hadronic to quark matter F Chiral symmetry will be restored F Motivation Transition from hadronic to quark matter F Chiral symmetry will be restored F Modification of vector meson properties (r, w, f) F Strangeness Enhancement: signature of QGP formation F Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI)

Light Vector Mesons R. Rapp • baryon effects important even at r. B, tot= Light Vector Mesons R. Rapp • baryon effects important even at r. B, tot= 0 : sensitive tor. Btot • w also melts, f more robust ↔ OZI Rule Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI)

The f puzzle: Pb+Au 158 AGe. V F F Difference observed in yields (factor The f puzzle: Pb+Au 158 AGe. V F F Difference observed in yields (factor 2 -4) and slopes (D. Röhrich J. Phys. G. 27(2001)355) F NA 49: fg. K+K- T=(305± 15)Me. V 2 f/(p++p-) 12. 2(13)10 -3 F NA 50: fgm+m- T=(218± 6)Me. V F F F Thermal Model : 2 f/(p++p-) 19. 10 -3 Reason: (J. Stachel et al. , PLB 465(1999)15) D. Lissauer, E. V. Shuryak, PLB 253 (1991) 15 F. Klingl, T. Waas, W. Weise, PLB 431 (1998) 254 Rescattering of K? F Modification of the mass/width of the f meson? Or the K? F Measurement of both decay channels in the same experiment CERES Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI)

The CERES Setup 2000 Run: 30 x 106 events s/s geo=7% 3 x 106 The CERES Setup 2000 Run: 30 x 106 events s/s geo=7% 3 x 106 events s/s geo=20% Sidc: vertex reconstruction, angle measurement Rich: electron ID TPC: momentum and electron-ID (smass~3. 8% at f gee) Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI)

The Sidc detectors Two 4 The Sidc detectors Two 4" silicon wafers • Charged particle tracking • Vertex reconstruction • Angle measurement Run 2000 Pb-Au Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI) s=205 mm

The RICH detectors Rich 1 Rich 2 • Electron identification • Hough transformation algorithm The RICH detectors Rich 1 Rich 2 • Electron identification • Hough transformation algorithm for ring recognition • Use of Rich 1/2 in combined mode (no Bfield) Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI)

The CERES TPC radial-drift TPC: • charged particle tracking • momentum determination • electron The CERES TPC radial-drift TPC: • charged particle tracking • momentum determination • electron ID via d. E/dx Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI)

Momentum and mass resolution ~3. 8% at f (includes bremsstrahlung contribution) sp/p=2% ⊕ 1%. Momentum and mass resolution ~3. 8% at f (includes bremsstrahlung contribution) sp/p=2% ⊕ 1%. p(Ge. V) Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI)

Centrality and Ncharge of 2000 data D. Miskowiec, nucl-ex/0511010 Measurement done at 7% centrality Centrality and Ncharge of 2000 data D. Miskowiec, nucl-ex/0511010 Measurement done at 7% centrality Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI)

Analysis steps: fg e+e- 1. Charged particle tracking 2. Electron identification 3. Rejection of Analysis steps: fg e+e- 1. Charged particle tracking 2. Electron identification 3. Rejection of combinatorial background Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI)

Electron identification with TPC d. E/dx e p s(d. E/dx)/(d. E/dx)<10% for all tracks Electron identification with TPC d. E/dx e p s(d. E/dx)/(d. E/dx)<10% for all tracks used Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI) Energy loss d. E/dx in TPC

Electron identification: TPC and RICH e. g. at 1. 0 Ge. V/c: 4 x Electron identification: TPC and RICH e. g. at 1. 0 Ge. V/c: 4 x 104 p-rejection factor 68% e-efficiency Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI)

Background rejection Dominant sources are p 0 -Dalitz and g-conversions 1. Dalitz recognition: F Background rejection Dominant sources are p 0 -Dalitz and g-conversions 1. Dalitz recognition: F Rejection of tracks which form a pair Qee < 35 mrad Tracks which form a pair mee < 0. 2 Ge. V/c 2 excluded F from further pairing F …still a large number of tracks remaining from F unrecognized p 0 -Dalitz pairs and g-conversions! F Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI)

Invariant mass fg e+e. F F F Invariant mass for opposite sign pairs with Invariant mass fg e+e. F F F Invariant mass for opposite sign pairs with pt>0. 2 Ge. V/c me+e-2 = 2. pe+. pe- (1 - cos qe+e-) Background subtraction using mixed events normalized to like sign background Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI)

Invariant mass fg e+ef : mass 0. 9 -1. 1 Ge. V/c 2 F Invariant mass fg e+ef : mass 0. 9 -1. 1 Ge. V/c 2 F 229 ± 53 Counts F S/B=1/12 F Physics Background: in-medium modified rho dilepton yield from QGP 35% contribution in f peak (R. Rapp) Decay cocktail+rho+QGP Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI)

Transverse Momentum Distribution fg e+e- T = 306 ± 82 (stat) Me. V d. Transverse Momentum Distribution fg e+e- T = 306 ± 82 (stat) Me. V d. N/dy=2. 19± 0. 52(stat)± 0. 34(syst) at 2. 1

Invariant mass fg K+KAll charged particles asigned the Kaon mass (no PID) F Selection Invariant mass fg K+KAll charged particles asigned the Kaon mass (no PID) F Selection of target tracks with matched SDD-TPC tracks F Single track cuts: 0. 130. 250 Ge. V/c F Opening angle vs pt cut following the f , Armenteros cut F 1. 5 Ge. V/c < pt < 1. 75 Ge. V/c 2. 2

fg K+K-: Acceptance and efficiency Includes losses due to decay on flight of charged fg K+K-: Acceptance and efficiency Includes losses due to decay on flight of charged kaons Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI)

fg K+K- : Transverse Momentum Distribution T = 273 ± 9(stat) ± 10(sys) Me. fg K+K- : Transverse Momentum Distribution T = 273 ± 9(stat) ± 10(sys) Me. V d. N/dy = 2. 05 ± 0. 14(stat) ± 0. 25(syst) at 2. 0

Comparison between two decay channels Different rapidity d. Nf/dy 2 -2. 4 =0. 93. Comparison between two decay channels Different rapidity d. Nf/dy 2 -2. 4 =0. 93. (d. Nf/dy)2. 1 -2. 65 (from NA 49, PLB 491(2000) 59 ) K+K-: d. N/dy=2. 05± 0. 14(stat)± 0. 25(syst) T = 273± 9(stat)± 10(sys) Me. V e+e- : d. N/dy=2. 04± 0. 49(stat)± 0. 32(syst) T = 306 ± 82(stat) Me. V Results in both channels in close agreement d. N/dy (fge+e-)/d. N/dy(fg. K+ K-)<1. 6 at 95% CL Ceres Collaboration: nucl-ex/0512007 Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI)

Comparison to NA 49/NA 50 results Different measurement conditions: NA 49 CERES centrality: 4% Comparison to NA 49/NA 50 results Different measurement conditions: NA 49 CERES centrality: 4% 7% rapidity: 3. 4 2. 2 Correction h-4%/h-7% CERES d. N/dy NA 49 Scaling factor: F =1. 17 ± 0. 12 NA 49 and NA 50: D. Röhrich, J. Phys. G. 27(2001)355 CERES: nucl-ex/0512007 Strangeness in Collisions Workshop , February 16 (2006) CERES results in K+K- and e+edecay channels agree with NA 49 results A. Marín (GSI)

Expectations from AMPT model and Ur. QMD AMPT: medium modifications and rescatering Ur. QMD: Expectations from AMPT model and Ur. QMD AMPT: medium modifications and rescatering Ur. QMD: K rescattering > 0. 63 at 95% CL S. C. Johnson et al. Eur. Phys. J C 18(2001) 645 S. Pal at al. , Nucl. Phys. A 707(2002) 525 Differences in yields between the two channels up 40 -50% (Ur. QMD) or up to 70% (AMPT) at low pt cannot be ruled out by CERES Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI)

Conclusions • • • For the first time in heavy-ion collisions the leptonic and Conclusions • • • For the first time in heavy-ion collisions the leptonic and charged kaon decay channels of the f meson are measured in the same experiment The measured rapidity densities and transverse momentum spectra are in agreement in both decay channels The data rule out a possible enhancement of the f yield in the leptonic over hadronic channel by a factor larger than 1. 6 at 95% CL. CERES results are in agreement with NA 49 results Possible differences of maximum 40 -50% as expected by models like Ur. QMD or up to 70% at lowest pt as expected by AMPT model cannot be ruled out by CERES results. Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI)

Ceres Collaboration F F F F F D. Adamova, G. Agakichiev, D. Antonczyk, A. Ceres Collaboration F F F F F D. Adamova, G. Agakichiev, D. Antonczyk, A. Andronic, H. Appelshäuser, V. Belaga, J. Bielcikova, P. Braun. Munzinger, O. Busch, A. Castillo, A. Cherlin, S. Damjanovic, T. Dietel, L. Dietrich, A. Drees, S. Esumi, K. Filimonov, K. Fomenko, Z. Fraenkel, C. Garabatos, P. Glässel, G. Hering, J. Holeczek, V. Kushpil, B. Lenkeit, W. Ludolphs, A. Maas, A. Manafov, A. Marin, J. Milosevic, A. Milov, D. Miskowiec, R. Ortega, Yu. Panebrattsev, O. Petchenova, V. Petracek, A. Pfeiffer, M. Ploskon, S. Radomski, J. Rak, I. Ravinovich, P. Rehak, W. Schmitz, J. Schukraft, H. Sako, S. Shimansky, S. Sedykh, J. Stachel, M. Sumbera, H. Tilsner, I. Tserruya, G. Tsiledakis, T. Wienold, B. Windelband, J. P. Wessels, J. P. Wurm, W. Xie, S. Yurevich, V. Yurevich F NPI ASCR, Rez, Czech Republic F GSI Darmstadt, Germany Frankfurt University, Germany Heidelberg University, Germany JINR Dubna, Russia Weizmann Institute, Rehovot, Israel SUNY at Stony Brook, USA CERN, Switzerland BNL, Upton, USA Münster University, Germany F F F F Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI)

FExtra Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI) FExtra Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI)

Main experimental difficulties in low e+e. Ne+e-/Nch ~10 -5: Electromagnetic decays are rare Ring Main experimental difficulties in low e+e. Ne+e-/Nch ~10 -5: Electromagnetic decays are rare Ring Imaging Cherencov Detectors gamma ~31 Aditional e-PID via TPC-d. E/dx vs momentum Ne+e-/Ng~10 -5: large gamma background Minimize radiation length in the acceptance Still large combinatorial background g g e+ep 0 gg e+e- Reconstruction of pair with small opening angle Good efficiency for low momentum tracks Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI)

The f meson F mf = 1019. 456 Me. V Gf = 4. 26 The f meson F mf = 1019. 456 Me. V Gf = 4. 26 Me. V (~45 fm) F F BR ( f g. K+K-) = 49. 1% BR ( f ge+e-) = 2. 98 x 10 -4 F Measurement of both decay channels in the same experiment CERES Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI)

Armenteros Cut Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI) Armenteros Cut Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI)

Opening Angle vs pt Cut Strangeness in Collisions Workshop , February 16 (2006) A. Opening Angle vs pt Cut Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI)

Background rejection energy loss in SDD Strangeness in Collisions Workshop , February 16 (2006) Background rejection energy loss in SDD Strangeness in Collisions Workshop , February 16 (2006) V-track signature in TPC A. Marín (GSI)

fg e+e-: Acceptance and efficiency Strangeness in Collisions Workshop , February 16 (2006) A. fg e+e-: Acceptance and efficiency Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI)

Counts in each pt bin (dilepton channel) Pt bin Counts Background 0. 0 -0. Counts in each pt bin (dilepton channel) Pt bin Counts Background 0. 0 -0. 4 Ge. V/c F 0. 4 -1. 0 Ge. V/c F 1. 0 -2. 0 Ge. V/c 51. 4+-29 109. 9+-41 67. 6+-24 802 1568 501 F F Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI)

Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI) Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI)

f transverse momentum spectrum We select the events on the f peak and use f transverse momentum spectrum We select the events on the f peak and use two side mass windows to estimate the p. T distribution of the continuum under the peak Then we correct for the acceptance, calculated (by Monte Carlo) as a 2 -dim matrix: p. T and y Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI)

f p. T spectrum versus y and centrality only statistical errors shown fitted curves: f p. T spectrum versus y and centrality only statistical errors shown fitted curves: C exp(-m. T/T) Ø There is no significant variation of the extracted inverse slope parameter, T, with rapidity Ø There is a clear increase from peripheral to central collisions Ø With full statistics, extension up to p. T > 3 Ge. V/c should be feasible Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI)

T(f): NA 60 versus NA 50 and NA 49 Average T(f) In-In values T T(f): NA 60 versus NA 50 and NA 49 Average T(f) In-In values T (Me. V) NA 49 Pb-Pb 1) all p. T 252 ± 3 Me. V 2) p. T < 1. 5 Ge. V (NA 49 range) 256 ± 6 Me. V NA 50 Pb-Pb NA 60 In-In 3) m. T > 1. 65 Ge. V (NA 50 range) 245 ± 5 Me. V Always ~ 250 Me. V Systematic errors still under investigation Expected to be less than 10 Me. V Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI)

Extraction of f KK signal from Monte Carlo Full simulation of In-In collisions (VENUS) Extraction of f KK signal from Monte Carlo Full simulation of In-In collisions (VENUS) Tracks in the same event are combined to build the mass spectrum F Tracks from different events are mixed if events belong to the same centrality class and their vertices are closer than 2 sx, 2 sy, 2 sz F Gaussian fit gives the mass and peak width F F Extracted values agree very well with the inputs of the simulation Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI)

f KK mass spectrum in F In. In collisions (NA 60 -QM 05) The f KK mass spectrum in F In. In collisions (NA 60 -QM 05) The real data follows the same analysis procedure Statistics sufficient to extract the f p. T distribution in 4 centrality bins F … but the background is not yet under sufficient control F Strangeness in Collisions Workshop , February 16 (2006) A. Marín (GSI)