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Research Activity





My research interests concern mainly the phenomenology of the Standard Model, and in particular QCD, at hadron and lepton colliders. I am involved in several collaborations working on the study of radiative corrections at the level of next-to-leading (NLO) and next-to-next-to-leading order (NNLO) in perturbative quantum field theory for observables that are important for the physics at colliders (in particular at a future international linear collider, ILC, and at the Large Hadron proton-proton Collider, LHC, of CERN).



Some specific topics:


Top-quark pair production at hadronic (and leptonic) colliders.

Heavy-quark (and in particular top) physics will play a twofold role on the LHC programme. From one side, it represents an active discovery channel for new physics. The top quark, so far the heaviest particle in the SM, will be a unique probe of the dynamics that breaks the electroweak gauge symmetry. If this mechanism differs from the Higgs mechanism of the SM, observable effects could be found first in top-quark production and decay, manifesting themselves as deviations of the top-quark gauge-boson couplings from the values predicted by the SM. From the other side, heavy-quark production (in particular the production of b quarks) will be an omnipresent background for other discovery channels. With the large number of top quarks expected to be produced at the LHC (a pair of top anti-top will be produced approximately every second), the study of its properties will become precision physics, demanding from the theoretical counterpart, the control of the higher order corrections in perturbative QCD. Together with my collaborators, we studied the NNLO QCD corrections to the production cross section of heavy quarks at leptonic colliders, important for observables like the forward-backward asymmetry that enters the evaluation of the weak mixing angle. For hadron colliders, we studied the NLL resummation of soft gluons for the total cross section of production of heavy quarks and, very recently, we started the evaluation of the NNLO QCD corrections to the production cross section of a heavy-quark pair, in particular of a pair of t-tbar at LHC. [Some References]


Higgs production and decay.

One of the most important tasks of the discovery programme of LHC is the possibility to detect the Higgs boson, the still missing particle of the Standard Model, responsible for the electroweak symmetry breaking. This goal will be achieved only if we can predict with high accuracy all the production cross sections of this particle and if we understand in detail the different decay channels and the relative backgrounds. This understanding means a total control on the radiative corrections in perturbative quantum field theory. Together with my collaborators, we provided analytic expressions for the electroweak (EW) and QCD two-loop corrections to the cross section of production of a Higgs boson at LHC. In particular, for what concerns the EW corrections we found a result surprisingly sizable: the cross section in the so-called intermediate Higgs mass range (m_H ~ 120 GeV) is enhanced of an amount which is comparable to the QCD uncertainty, i.e. of about 6%. It was possible to check the very well known result about the NLO QCD corrections for the Higgs production cross section of Spira-Djouadi-Graudenz-Zervas. Moreover, we provided exact analytic formulas for the NLO contributions to the gluon fusion production cross section of a scalar Higgs in models in which fermion and scalar massive colored particles are present. [Some References]


Semileptonic B meson decays.

The measurements of inclusive semileptonic B meson decays allow a precise determination of the CKM matrix elements V_ub and V_cb, relevant for the study of flavor and CP violation in the quark sector. This requires, from the theoretical counterpart, the calculation of NNLO corrections to differential decay distributions, from which it is possible to derive predictions for partial decay rates with arbitrary experimental cuts. In collaboration with A. Ferroglia, we provided an analytic expression for the two-loop QCD corrections to the decay process b → u W*, where b and u are a massive and massless quark, respectively, and W* is an off-shell charged weak boson, that subsequently decays in a lepton anti-neutrino pair. These results are a first step towards a fully analytic computation of differential distributions for the semileptonic charmless decays of B mesons. [Some References]


Bhabha scattering.

One of the characteristics of ILC, i.e. of a linear e+ e- collider working at a center of mass energy of about 500 GeV, is the “Precision”. All the input parameters of the Standard Model will be determined with an extremely high accuracy. In order to reach this accuracy, the luminosity of the machine has to be determined and controlled with a comparable accuracy. The luminosity depends strongly on the theoretical determination of the cross section for the Bhabha scattering, e+ e- → e+ e-. In the last years, together with my collaborators, we contributed to the evaluation of the full set of NNLO QED corrections to the Bhabha scattering cross section. In particular, recently we provided analytic formulas for the two-loop corrections due to a heavy fermion loop. These corrections could be large (of the order of the expected error for the determination of the luminosity) in the cases of top-quark corrections at ILC energies (500 GeV), or a tau lepton corrections at low energy factories as, for instance, DAPHNE (energies of the order of 1 GeV). [Some References]


Master Integrals.

Together with my collaborators, we evaluated many Master Integrals at the two-loop level. [Some References]