arXiv subjects
Publications and source records attributed to A. Sandacz.
HEPGEN is a generator of Monte Carlo events, which is dedicated to studies of hard exclusive single photon or meson production processes at the COMPASS experiment kinematic domain. In addition HEPGEN allows to generate also single photon or meson production accompanied by the diffractive dissociation of the nucleon, which is one of the main sources of background in analyses of exclusive processes.
We present the first measurements of the double spin asymmetries A_NN and A_SS at sqrt{s}=200 GeV, obtained by the pp2pp experiment using polarized proton beams at the Relativistic Heavy Ion Collider (RHIC). The data were collected in the four momentum transfer t range 0.01<|t|<0.03 (GeV/c)^2. The measured asymmetries, which are consistent with zero, allow us to estimate upper limits on the double helicity-flip amplitudes phi_2 and phi_4 at small t as well as on the difference Delta(sigma_T) between the total cross sections for transversely polarized protons with antiparallel or parallel spin orientations.
This paper presents the reactions which can be performed at COMPASS to study the Generalized Parton Distributions (GPDs). The high energy muon beam at CERN allows to measure Hard Exclusive Meson Production or Deeply Virtual Compton Scattering (DVCS) in the Bjorken regime in a large range of Q^2 and x_Bj (1.5<Q^2<7.5 GeV^2 and 0.03<x_Bj<0.25). Exploratory measurements dedicated to rho_0 or pi_0 production can be investigated with the present setup. DVCS measurement require an upgrade of the COMPASS setup.
We examine the potential of the COMPASS experiment at CERN to study color transparency via exclusive coherent vector meson production in hard muon-nucleus scattering. It is demonstrated that COMPASS has high sensitivity to test this important prediction of perturbative QCD.
We present the structure function ratios F2(Li)/F2(D) and F2(C)/F2(D) measured in deep inelastic muon-nucleus scattering at a nominal incident muon energy of 200 GeV. The kinematic range 0.0001 < x < 0.7 and 0.01< Q^2 < 70 GeV^2 is covered. For values of $x$ less than $0.002$ both ratios indicate saturation of shadowing at values compatible with photoabsorption results.