Monte Carlo simulations using infrared improved DGLAP-CS theory.
Joseph, Samuel J.
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A large number of Z and W bosons will be produced at the LHC. A careful study of their properties in the presence of QCD background processes, will be important in studying the Standard Model more rigorously and to uncover new physics which may appear through radiative corrections or through new tree level processes with suppressed couplings. In order to reach the 1% attendant theoretical precision tag on processes such as single Z and W production, more precise Monte Carlos need to be developed. As a step towards this goal a new set of infrared (ir) improved DGLAP-CS kernels was developed by Ward. For this work we implemented these infrared improved kernels in HERWIG6.5 to create a new program HERWIRI1.0. We discuss the phenomological implications of our new Monte Carlo HERWIRI1.0. Specifically we compared pp → 2-jets + X and pp → Z/γ* + X → ℓ⁺ℓ⁻ + X´, with ℓ=e,μ, results obtained by HERWIG6.5 and HERWIRI1.0. The three main quantities that we compared were the pt, energy fraction and rapidity distributions. We made these comparisons at √s=14 TeV, the highest LHC energies. Comparisons were also made for π⁺ production in pp → 2-jets + X at this energy. As expected, the IR-improved spectra were generally softer. As a test of HERWIRI1.0 a comparison of the pt and rapidity distribution data from FNAL at √s=1 96 TeV for the process pp̅ → Z/γ* → e⁺e⁻ + X was made. We found that the softer part of these observed spectra were better described by HERWIRI1.0. This represents a new chapter in precision Monte Carlo simulations for hadron-hadron high energy collisions because the IR-improved kernels do not require an explicit cut-off.