1. HADRON 2009, FloridaAnar Rustamov, GSI Darmstadt, Germany 1 Inclusive meson production at 3.5 GeV pp collisions with the HADES spectrometer Anar Rustamov for the HADES Collaboration GSI Helmholtzzentrum für Schwerionenforschung

2. HADRON 2009, FloridaAnar Rustamov, GSI Darmstadt, Germany 2 Outline  physics motivation  experimental approach  pp data at 3.5 GeV kinetic energy  What is known?  HADES spectrometer  pair spectra  combinatorial background  absolute normalization  cross sections  comparison with models  PLUTO  HSD  UrQMD  pA data  summary

3. HADRON 2009, FloridaAnar Rustamov, GSI Darmstadt, Germany 3 Physics motivation Chiral symmetry: SU(2) L x SU(2) R Spontaneously broken in vacuum by Hadrons in medium Partial Restoration in medium (melting of ) QCD sum rules Investigation of spectral functions of hadrons in medium dispersion relation > > Δ,N* N -1 + … m m QCD part: W. Peters et al. NPA 632(1998)109 T. Hatsuda, S.H. Lee, Phys. Rev. C 46 (1992) R34

4. HADRON 2009, FloridaAnar Rustamov, GSI Darmstadt, Germany 4 Experimental approach Mass distribution of the hadrons inside medium: p1, p2: 4-momenta  Hadrons should be short lived (ρ, ω, Φ)  p1, p2 should be undistorted (leptons) ρ(m) - spectral function, Г - width Experimental challenge: Mass [MeV] c [fm] Г/Г tot ->ee  7701.34.7×10 -5  78223.47.07×10 -5  102044.42.97×10 -4 small branching ratios high background

5. HADRON 2009, FloridaAnar Rustamov, GSI Darmstadt, Germany 5 pp data at 3.5 GeV  Unknown inclusive cross sections  Meson production mechanisms  Reference to the pA and AA reactions pp -> ppω OBE HSD pp -> ρX HSD OBE W. Cassing, E. Bratkovskaya, Physics Reports 308 (1999) 65 -233 pp -> ppρ

6. HADRON 2009, FloridaAnar Rustamov, GSI Darmstadt, Germany 6 HADES spectrometer  Acceptance  φ ~ 2 π  15 o < θ < 85 o  pair ~ 30%  Momentum resolution  Magnet: 0.1-0.34 Tm  MDC: 24 drift chambers  σ m ~ 2% at ρ/ω region  Particle identification  RICH  Time of flight  Pre-Shower  MDC (for hadrons)  Trigger  LVL1- charged particle mult.  LVL2- single electron trigger

7. HADRON 2009, FloridaAnar Rustamov, GSI Darmstadt, Germany 7 Pair spectra θ pair > 9 0 All e+e- = S e+e- + CB Particle identification:  RICH-MDC matching  Time of flight cuts  Shower cuts Background rejection:  close track cut  opening angle cut  track fitting quality cut θ pair > 9 0 All e+e- = S e+e- + CB Combinatorial background (CB) CB = N ++ + N - - uncorrelated correlated

8. HADRON 2009, FloridaAnar Rustamov, GSI Darmstadt, Germany 8 Pair spectra high S/CB ratio Efficiency corrected. Inside HADES acceptance Number of pairs:  All : ~ 6.1*10 4  M <0.15 : ~ 5.5*10 4  0.6 < M < 0.82 : ~ 451 Signal CB σ ω ~ 16 MeV/c 2

9. HADRON 2009, FloridaAnar Rustamov, GSI Darmstadt, Germany 9 Absolute normalization Elastic scattering Kinematic constraints: Kammerud et al. Phys. Rev. D 4 (1971), 5

10. HADRON 2009, FloridaAnar Rustamov, GSI Darmstadt, Germany 10 Cross sections σ πo = 15 mb ± 4mb from Consistent with Resonance model S. Teis et al. Z. Phys. A 356, 421-435 (1997) σ ω = 0.285 mb ± 0.07mb from σ η = 1.04 mb ± 0.3 mb from Inclusive cross sections from pair spectra H. Weber et al., PRC 67 (2003) 014904 pp → π + X pp → π - X pp → π o X (HADES) lines are from HSD pp -> ωX pp -> ppω (HADES) HSD OBE W. Cassing, E. Bratkovskaya, Physics Reports 308 (1999) 65 -233

11. HADRON 2009, FloridaAnar Rustamov, GSI Darmstadt, Germany 11 Cocktail simulation with PLUTO  particle production  phase space ( but 1 π exchange for the Δ ) Fröhlich et al, arxiv:0708.2382  particle decays  form factors ( see talk by B. Ramstein)  rel. BW  mass dep. Width  cross sections [mb]  π o : 15  Δ : from isospin coeff.  η : 1.04  ω : 0.28  ρ : 0.36

12. HADRON 2009, FloridaAnar Rustamov, GSI Darmstadt, Germany 12 Cocktail subtracted data Particle production  HSD  Lund String Model  UrQMD  Through Resonances N *, Δ N N N N m π o, η and ω contributions are subtracted  Missing yield in PLUTO  Overestimation of ρ in UrQMD  HSD from new calculations W. Cassing, E. Bratkovskaya, Physics Reports 308 (1999) 65 -233 K. Schmidt, et al. Phys. Rev. C 79, 064908 (2009)

13. HADRON 2009, FloridaAnar Rustamov, GSI Darmstadt, Germany 13 pNb data, online spectra Signal Online spectra:  preliminary calibrations  preliminary alignment pNb data pair momenta in ρ/ω region shape of ρ/ω as a function of their momenta can be studied At the same kinetic energy of protons ( 3.5 GeV )

14. HADRON 2009, FloridaAnar Rustamov, GSI Darmstadt, Germany 14 Summary Meson production was investigated in pp reactions at T kin = 3.5 GeV For the first time inclusive cross sections for the π 0, η and ω mesons were reconstructed The investigation of production mechanisms of the vector mesons are ongoing Reference spectra for the pNb run at the same beam kinetic energy is obtained

15. HADRON 2009, FloridaAnar Rustamov, GSI Darmstadt, Germany 15 More Slides