1. XLVII Int. Winter Meeting, Bormio, Jan. 26-30, 2009 CHARGED PION PRODUCTION IN C+C AND Ar+KCl COLLISIONS MEASURED WITH HADES Pavel Tlustý, NPI Řež for the HADES collaboration study of charged  meson production C+C at 1A GeV and 2A GeV, and Ar+KCl at 1.75A GeV multiplicities, m T, rapidity, angular distributions

2. Motivation - study of hadron production gives information about the reaction dynamics, pion production described by transport models - charged pion multiplicities used for normalization of dilepton spectra - check of performance of the HADES spectrometer, in terms of its acceptance, and detector and analysis efficiency, which is crucial for extraction of rare lepton pairs in high hadron multiplicity events XLVII Int. Winter Meeting, Bormio, Jan. 26-30, 2009 p+p cos(θcms)

3. XLVII Int. Winter Meeting, Bormio, Jan. 26-30, 2009 HADES HADES A High-Acceptance Di-Electron SpectrometerHADES (expanded view)  Acceptance: 2  in φ ; six sectors 18 0 < θ < 85 0  Pair acceptance  35 % Tracking: Magnet+MDC - momenta  Superconducting toroid magnet 6 coils, B max = 0.7 T, Bending power 0.34 Tm  low-mass MDC 4 layers of multiwire drift chamber TOF - velocity  META TOF(  =90-140 ps) TOFino (  = 350ps) Pre-Shower  Start detector diamond (  = 30 ps) Lepton Identification  RICH  hadron blind  photon detector: CsI photo cathode LVL1 trigger  multiplicity of charged hits in TOF/TOFino M ≥ 4 for C+C and M ≥ 16 for ArKCl

4. XLVII Int. Winter Meeting, Bormio, Jan. 26-30, 2009 HADES Experiments  November 2002:C+C 2 AGeV [1]  February 2004: p+p 2.2 GeV  August 2004: C+C 1 AGeV [2]  October 2005: Ar+KCl 1.75 AGeV  May 2006: p+p 1.25 GeV  April-May 2007: p+p 3.5 GeV, d+p 1.25 GeV  September 2008: p+Nb 3.5 GeV [1] Phys. Rev. Lett. 98, 052302 (2007) [2] Phys. Lett. B663, 43 (2008)

5. XLVII Int. Winter Meeting, Bormio, Jan. 26-30, 2009 Track Reconstruction and PID Charge * Momentum [MeV/c] ToFino ToF beta [v/c] reconstruction efficiencyparticle identification detection &track reconstruction efficiency from simulations and validated in experiments on elementary processes (pp elastic scattering,..) systematic error 5%

6. XLVII Int. Winter Meeting, Bormio, Jan. 26-30, 2009 Results

7. XLVII Int. Winter Meeting, Bormio, Jan. 26-30, 2009 m T distributions – Ar+KCl 1.75A GeV y 0 = (y lab – y cm )/y cm

8. XLVII Int. Winter Meeting, Bormio, Jan. 26-30, 2009 m T distributions at midrapidity Ar+KCl

9. XLVII Int. Winter Meeting, Bormio, Jan. 26-30, 2009 m T distributions Ar+KCl Inverse slopes at midrapidity Particle50 < m t - m  < 550 DataUrQMD π+π+ 52  3 ; 95  2 41.3  0.6 ; 90.3  0.2 π-π- 51  2 ; 95  340.8  0.5 ; 89.9  0.2 π + :  2 /NDF) 36/16 = 2.330.1/16=1.9 π -  2 /NDF) 15.1/16 = 1.061/16=3.8 Brockman et al. Phys. Rev. Lett. 53, 2012 (1984) Ar +KCl 1.8 AGeV   : T 1 =58 ±3 MeV (95%) T 2 =110 ±10 MeV (5%)

10. HADES coll. meeting, Oct. 31, 2007 m T distributions C+C 1 A GeV

11. HADES coll. meeting, Oct. 31, 2007 m T distributions C+C 2 A GeV

12. XLVII Int. Winter Meeting, Bormio, Jan. 26-30, 2009 C+C momentum distributions – HADES vs KAOS HADES data filtered by the KaoS acceptance filter, and recalculated to minimum bias cross section Agreement for charged pions within errors Kaos data : C. Sturm (KaoS coll.) PhD thesis,TU Darmstadt, 2001 http://elib.tu-darmstadt.de/diss/000166

13. XLVII Int. Winter Meeting, Bormio, Jan. 26-30, 2009 C+C momentum distributions – HADES vs TAPS different shapes of charged and neutral pion distributions at 2A GeV TAPS data - R. Averbeck et al. (TAPS Collaboration), Z. Phys. A 359, 65 (1997).

14. XLVII Int. Winter Meeting, Bormio, Jan. 26-30, 2009 Rapidity distributions to get a proper rapidity distribution, and particle multiplicities, extrapolation of yields outside the accepted phase space region has to be made: 1) low p_t 2) backward and forward rapidities

15. XLVII Int. Winter Meeting, Bormio, Jan. 26-30, 2009 Extrapolation in p t

16. XLVII Int. Winter Meeting, Bormio, Jan. 26-30, 2009 Rapidity distributions C+C symmetrized

17. XLVII Int. Winter Meeting, Bormio, Jan. 26-30, 2009 Rapidity distributions Ar+KCl LVL1 trigger events 1) within HADES acceptance 2) extrapolated to full solid angle, systematic error 9% symmetrized

18. XLVII Int. Winter Meeting, Bormio, Jan. 26-30, 2009 Pion multiplicities per participant centrality selection Ar+KCl UrQMD centrality selection by the LVL1 trigger exp. and simulated multiplicities

19. XLVII Int. Winter Meeting, Bormio, Jan. 26-30, 2009 Pion multiplicities per participant N π / A part = 0.100 (Ca+Ca @ 1.756 AGeV) W. Reisdorf et al., Nucl. Phys. A 781 (2007) 459-508 N π- / A part = 0.086 (Ar+KCl @ 1.8 AGeV) J.W.Harris et al.,Phys.Lett. 153 B (1985) 377 UrQMD C+C 1A GeV 8.6±0.6 0.055 ± 0.003 ± 0.005 ± 0.004 0.059 C+C 2A GeV 8.4 -0 +1.2 0.147 ± 0.007 ± 0.013 -0 +0.021 0.137 Ar+KCl 1.75A GeV 39±3 0.088 ± 0.004 ± 0.008 ± 0.006 0.100

20. XLVII Int. Winter Meeting, Bormio, Jan. 26-30, 2009 dN/d cos(  cm ) ~ 1. + A 2 ∙ cos 2 (  cm ) Center of mass polar distributions – C+C p cm > 200 MeV/c

21. XLVII Int. Winter Meeting, Bormio, Jan. 26-30, 2009 h h Center of mass polar distributions - C+C H

22. XLVII Int. Winter Meeting, Bormio, Jan. 26-30, 2009 dN/d cos(  cm ) ~ 1. + A 2 ∙ cos 2 (  cm ) Center of mass polar distributions - ArKCl 200 < p cms < 800 MeV/c A 2 = 0.70±0.10A 2 = 0.80±0.11 UrQMD A 2 = 0.99

23. XLVII Int. Winter Meeting, Bormio, Jan. 26-30, 2009 Brockmann et al. Ar+KCl 1.8 AGeV central collisions: R. Brockmann et al., Phys. Rev. Lett. 53 (1984) 2012 : A 2 = 0.52, peak in the A2 dependence on momentum FOPI NPA 781 (2007) shows the same anisotropy for Ca+Ca 1.93 A GeV Center of mass polar distributions - ArKCl

24. XLVII Int. Winter Meeting, Bormio, Jan. 26-30, 2009 Centrality study - ArKCl

25. XLVII Int. Winter Meeting, Bormio, Jan. 26-30, 2009 Summary charged  meson production from C+C at 1 A GeV and 2 A GeV, and Ar+KCl at 1.75 A GeV studied results: multiplicities - in large acceptance, small systematic errors polar anisotropies - momentum dependence m T distributions – different shapes of charged vs neutral pion spectra

26. XLVII Int. Winter Meeting, Bormio, Jan. 26-30, 2009 The collaboration  Bratislava (SAS, PI), Slovakia  Catania (INFN - LNS), Italy  Cracow (Univ.), Poland  Darmstadt (GSI), Germany  Dresden (FZR), Germany  Dubna (JINR), Russia  Frankfurt (Univ.), Germany  Giessen (Univ.), Germany  Milano (INFN, Univ.), Italy  Munich (TUM), Germany  Moscow (ITEP,MEPhI,RAS), Russia  Nicosia (Univ.), Cyprus  Orsay (IPN), France  Rez (CAS, NPI), Czech Rep.  Sant. de Compostela (Univ.), Spain  Valencia (Univ.), Spain  Coimbra (Univ.), Portugal SIS

27. XLVII Int. Winter Meeting, Bormio, Jan. 26-30, 2009 Backup slides

28. XLVII Int. Winter Meeting, Bormio, Jan. 26-30, 2009 Principle: for each track a probability that it is of a particle type h is calculated, for all possible particle types Bayes theorem implemented cut on the resulted probability set to decide on PID Input: for each track (track candidate) with a given momentum we have a set of independent measured variables in HADES: velocity, energy loss, RICH response, MDC hit, SHOWER response Output: - a probability, that a given track corresponds to the particle type h - efficiency and purity for a selected cut Particle Identification Method

29. XLVII Int. Winter Meeting, Bormio, Jan. 26-30, 2009 PID efficiency and purity - performance checked using UrQMD - pions identified for momenta 150 < p < 1000 MeV/c

30. XLVII Int. Winter Meeting, Bormio, Jan. 26-30, 2009 “Selfconsistency check” - UrQMD UrQMD input (emitted) and its reconstruction by analysis

31. XLVII Int. Winter Meeting, Bormio, Jan. 26-30, 2009 References: P. Senger, H. Strobele, J. Nucl. Part., Phys. 25 (1999) R59 J.W Harris et al., Phys. Lett. 153B, 377 (1985) J.W Harris et al., Phys. Rev. Lett. 58(1987) 463 W. Reisdorf et al., Nucl. Phys. A 781 (2007) 459-508 R. Stock et al., Phys. Rep. 135, No. 5 (1986) 259-315 R. Brockmann et al., Phys. Rev. Lett. 53 (1984) 2012 Sandoval et al., Phys. Rev. Lett. 45 (1980) 874 S. Nagamiya et al., Pysc. Rev. C 24 (1981) 971 References

32. XLVII Int. Winter Meeting, Bormio, Jan. 26-30, 2009 Fits of p t by 1 or 2 slopes

33. XLVII Int. Winter Meeting, Bormio, Jan. 26-30, 2009 Cms polar distributions – central collisions