Giancarlo Ferrera

Vector Boson Production at Hadron Colliders: A Fully Exclusive QCD Calculation at Next-to-Next-to-Leading Order

We consider QCD radiative corrections to the production of W and Z bosons in hadron collisions. We present a fully exclusive calculation up to next-to-next-to-leading order (NNLO) in QCD perturbation theory. To perform this NNLO computation, we use a recently proposed version of the subtraction formalism. The calculation includes the gamma-Z interference, finite-width effects, the leptonic decay of the vector bosons, and the corresponding spin correlations. Our calculation is implemented in a parton level Monte Carlo program. The program allows the user to apply arbitrary kinematical cuts on the final-state leptons and the associated jet activity and to compute the corresponding distributions in the form of bin histograms. We show selected numerical results at the Fermilab Tevatron and the LHC.

Diphoton production at hadron colliders: a fully-differential QCD calculation at NNLO

We consider direct diphoton production in hadron collisions, and we compute the next-to-next-to-leading order QCD radiative corrections at the fully differential level. Our calculation uses the q(T) subtraction formalism, and it is implemented in a parton-level Monte Carlo program. The program allows the user to apply arbitrary kinematical cuts on the final-state photons and the associated jet activity and to compute the corresponding distributions in the form of bin histograms. We present selected numerical results related to Higgs boson searches at the LHC and corresponding results at the Tevatron.

Transverse-momentum resummation: Higgs boson production at the Tevatron and the LHC

A bstractWe consider the transverse-momentum (qT ) distribution of Standard Model Higgs bosons produced by gluon fusion in hadron collisions. At small qT (qT ≪ mH , mH being the mass of the Higgs boson), we resum the logarithmically-enhanced contributions due to multiple soft-gluon emission to all order in QCD perturbation theory. At interme-diate and large values of qT (qT < mH), we consistently combine resummation with the known fixed-order results. We use the most advanced perturbative information that is available at present: next-to-next-to-leading logarithmic resummation combined with the next-to-leading fixed-order calculation. We extend previous results including exactly all the perturbative terms up to order αS in our computation and, after integration over qT, we recover the known next-to-next-to-leading order result for the total cross section. We present numerical results at the Tevatron and the LHC, together with an estimate of the corresponding uncertainties. Our calculation is implemented in an updated version of the numerical code HqT.

Associated Higgs-W-Boson Production at Hadron Colliders: A Fully Exclusive QCD Calculation at NNLO

We consider QCD radiative corrections to standard model Higgs-boson production in association with a W boson in hadron collisions. We present a fully exclusive calculation up to next-to-next-to-leading order (NNLO) in QCD perturbation theory. To perform this NNLO computation, we use a recently proposed version of the subtraction formalism. Our calculation includes finite-width effects, the leptonic decay of the W boson with its spin correlations, and the decay of the Higgs boson into a bb pair. We present selected numerical results at the Tevatron and the LHC.

Production of Drell–Yan lepton pairs in hadron collisions: Transverse-momentum resummation at next-to-next-to-leading logarithmic accuracy

Abstract We consider the transverse-momentum ( q T ) distribution of Drell–Yan lepton pairs produced in hadron collisions. At small values of q T , we resum the logarithmically-enhanced perturbative QCD contributions up to next-to-next-to-leading logarithmic accuracy. At intermediate and large values of q T , we consistently combine resummation with the known next-to-leading order perturbative result. All perturbative terms up to order α S 2 are included in our computation which, after integration over q T , reproduces the known next-to-next-to-leading order result for the Drell–Yan total cross section. We show and discuss the reduction in the scale dependence of the results with respect to lower-order calculations, estimating the corresponding perturbative uncertainty. We present a preliminary comparison with Tevatron Run II data.

W boson production at hadron colliders: the lepton charge asymmetry in NNLO QCD

We consider the production of W± bosons in hadron collisions, and the subsequent leptonic decay W → lνl. We study the asymmetry between the rapidity distributions of the charged leptons, and we present its computation up to the next-to-next-to-leading order (NNLO) in QCD perturbation theory. Our calculation includes the dependence on the lepton kinematical cuts that are necessarily applied to select W → lνl events in actual experimental analyses at hadron colliders. We illustrate the main differences between the W and lepton charge asymmetry, and we discuss their physical origin and the effect of the QCD radiative corrections. We show detailed numerical results on the charge asymmetry in

Transverse-momentum resummation: A perturbative study of Z production at the Tevatron

p\bar p

Modelling non-perturbative corrections to bottom-quark fragmentation

collisions at the Tevatron, and we discuss the comparison with some of the available data. Some illustrative results on the lepton charge asymmetry in pp collisions at LHC energies are presented.

Triple Higgs boson production at the ILC within a generic Two-Higgs-Doublet Model

Abstract We consider transverse-momentum ( q T ) resummation for Drell–Yan lepton pair production in hadron collisions. At small values of q T , the logarithmically-enhanced QCD contributions are resummed up to next-to-leading logarithmic accuracy. At intermediate and large values of q T , resummation is consistently combined with the fixed-order perturbative result. We present numerical results for e + e − pairs from the decay of Z bosons produced at Tevatron energies. We perform a detailed study of the scale dependence of the results to estimate the corresponding perturbative uncertainty. We comment on the comparison with the available Tevatron data.

Resummed mass distribution for jets initiated by massive quarks

Abstract We describe B-hadron production in e + e − annihilation at the Z 0 pole by means of a model including non-perturbative corrections to b-quark fragmentation as originating, via multiple soft emissions, from an effective QCD coupling constant, which does not exhibit the Landau pole any longer and includes absorptive effects due to parton branching. We work in the framework of perturbative fragmentation functions at NLO, with NLL DGLAP evolution and NNLL large-x resummation in both coefficient function and initial condition of the perturbative fragmentation function. We include hadronization corrections via the effective coupling constant in the NNLO approximation and do not add any further non-perturbative fragmentation function. As part of our model, we perform the Mellin transforms of our resummed expressions exactly. We present results on the energy distribution of b-flavored hadrons, which we compare with LEP and SLD data, in both x- and N-spaces. We find that, within the theoretical uncertainties on our calculation, our model is able to reasonably reproduce the data at x ≲ 0.92 and the first five moments of the B cross section.