QCD resummation for Drell-Yan-like processes beyond the Standard Model
par
DrBenjamin Fuks(Universite de Freiburg)
→
Europe/Paris
Salle 9213
Salle 9213
Description
When studying the transverse-momentum (pT) distribution of
a produced colorless final state (e.g. slepton pair in
supersymmetric models or lepton pair in the Z' models), 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 selectron and stau 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.