Precision predictions for hadroproduction processesbeyond the Standard Model

par Benjamin Fuks (CERN)

lundi 2 nov. 2009, 14:00 → 15:00 Europe/Paris

Amphithéâtre

When studying the transverse-momentum (pT) distribution of a produced colorless final state, it is convenient to separate the large- and small-pT regions. For the large values of pT the use of the fixed-order perturbation theory is fully justified, but in the small-pT region, the coefficients of the perturbative expansion are enhanced by powers of large logarithmic terms. Furthermore, at the production threshold, the mismatch between virtual corrections and phase-space suppressed real-gluon emission leads also to the appearance of large logarithmic terms. Accurate calculations of pT-spectrum and invariant mass distribution must then include soft-gluon resummation in order to obtain reliable perturbative predictions and properly take these logarithmic terms into account. We implement the transverse-momentum, threshold and joint resummation formalisms at the next-to-leading logarithmic accuracy and consistently match the obtained result with the pure perturbative result at the first order in the strong coupling constant. We present precision calculations for SUSY particle pair production at hadron colliders, give numerical predictions, and compare the various resummed cross sections with the perturbative results. We confront then the results obtained with the next-to-leading order Monte Carlo generator MC@NLO and with the leading-order Monte Carlo generator PYTHIA to joint resummation in the framework of Z' models. The impact of scale and parton densities dependences, as well as non-perturbative effects, are also studied.

Slides fuks.pdf