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Jet quenching by (pre--)hadronic final state interactions at RHIC

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 Added by Kai Gallmeister
 Publication date 2004
  fields
and research's language is English




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Within a hadron-string dynamical transport approach (HSD) we investigate the attenuation of high transverse momentum ($pT$) hadrons as well as the suppression of near-side and far-side jets in $Au+Au$ collisions at invariant energies $sqrt{s}$ = 200 GeV and $sqrt{s}$ = 62.4 GeV in comparison to the data available from the Relativistic Heavy-Ion Collider (RHIC). From our transport studies we find that a significant part of the high $pT$ hadron attenuation seen experimentally can be attributed to inelastic interactions of leading pre-hadrons with the dense hadronic environment. In addition, we also show results of near-side and far-side angular correlations of high $pT$ particles from Au+Au collisions at $sqrt{s}$ = 200 GeV and $sqrt{s}$ = 62.4 GeV within this (pre-)hadronic attenuation scenario. It turns out that the near-side correlations are unaltered -- in accordance with experiment -- whereas the far-side correlations are suppressed by up to $sim$ 60% in central collisions. Since a much larger suppression is observed experimentally for these reactions in central reactions we conclude that there should be strong additional (and earlier) partonic interactions in the dense and possibly colored medium created in Au+Au collisions at RHIC.



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203 - K.Gallmeister , C.Greiner , Z.Xu 2002
Typically the materialization of high energetic transverse partons to hadronic jets is assumed to occur outside the reaction zone in a relativistic heavy ion collision. In contrast, a quantum mechanical estimate yields a time on the order of only a few fm/c for building up the hadronic wavefunction for jets with typical transverse momenta of pT < 10 GeV as accessible at RHIC facilities. The role of possible elastic or inelastic collisions of these high pT particles with the bulk of hadrons inside the fireball is addressed by means of an opacity expansion in the number of collisions. This analysis shows that the hadronic final state interactions can in principle account for the modification of the (moderate) high pT spectrum observed for central collisions at RHIC.
138 - Jose A. Oller 2004
We show that the large corrections due to final state interactions (FSI) in the D^+to pi^-pi^+pi^+, D^+_sto pi^-pi^+pi^+, and D^+to K^-pi^+pi^+ decays can be accounted for by invoking scattering amplitudes in agreement with those derived from phase shifts studies. In this way, broad/overlapping resonances in S-waves are properly treated and the phase motions of the transition amplitudes are driven by the corresponding scattering matrix elements determined in many other experiments. This is an important step forward in resolving the puzzle of the FSI in these decays. We also discuss why the sigma and kappa resonances, hardly visible in scattering experiments, are much more prominent and clearly visible in these decays without destroying the agreement with the experimental pipi and Kpi low energy S-wave phase shifts.
Within five different approaches to parton propagation and energy loss in dense matter, a phenomenological study of experimental data on suppression of large $p_T$ single inclusive hadrons in heavy-ion collisions at both RHIC and LHC was carried out. The evolution of bulk medium used in the study for parton propagation was given by 2+1D or 3+1D hydrodynamic models which are also constrained by experimental data on bulk hadron spectra. Values for the jet transport parameter $hat q$ at the center of the most central heavy-ion collisions are extracted or calculated within each model, with parameters for the medium properties that are constrained by experimental data on the hadron suppression factor $R_{AA}$. For a quark with initial energy of 10 GeV we find that $hat qapprox 1.2 pm 0.3$ GeV$^2$/fm at an initial time $tau_0=0.6$ fm/$c$ in Au+Au collisions at $sqrt{s}=200$ GeV/n and $hat qapprox 1.9 pm 0.7 $ GeV$^2$/fm in Pb+Pb collisions at $sqrt{s}=2.76 $ TeV/n. Compared to earlier studies, these represent significant convergence on values of the extracted jet transport parameter, reflecting recent advances in theory and the availability of new experiment data from the LHC.
We evaluate the non-resonant decay amplitude of the process $B^pmto K^pmpi^+ pi^-$ using an approach based on final state hadronic interactions described in terms of meson exchanges. We conclude that this mechanism generates inhomogeneities in the Dalitz plot of the B decay.
55 - Stathes Paganis 2003
This presentation reports recent results from the hadronic final state in DIS at HERA. Forward jet and $pi^0$ production have been measured by the H1 experiment. The forward jet production cross section shows significant deviation from the predictions based on DGLAP evolution. The forward $pi^0$ data discriminate between different QCD models and are best described by models which take into account the partonic substructure of virtual photons. Inclusive $K_s^0K_s^0$ production in $ep$ has been studied with the ZEUS detector using an integrated luminosity of 120 pb$^{-1}$. Two states are observed at masses of 1537 MeV and 1726 MeV as well as an enhancement around 1300 MeV. The state at 1537 MeV is consistent with the well established $f_2^prime(1525)$. The state at 1726 MeV may be the glueball candidate $f_0(1710)$.
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