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

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

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

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  ×10 -5  ×10 -5  ×10 -4 small branching ratios high background

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) pp -> ppρ

HADRON 2009, FloridaAnar Rustamov, GSI Darmstadt, Germany 6 HADES spectrometer  Acceptance  φ ~ 2 π  15 o < θ < 85 o  pair ~ 30%  Momentum resolution  Magnet: 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

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

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

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

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, (1997) σ ω = 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) 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)

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:  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

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) K. Schmidt, et al. Phys. Rev. C 79, (2009)

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 )

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

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