P. Chiappetta

QCD Corrections to Parton-Parton Scattering Processes

We evaluate the full O(αs3) QCD corrections to one particle inclusive cross section and jet production within a small opening angle δ at large transverse momenta for all partonic subprocesses. Some phenomenological applications are given with particular emphasis on the magnitude of O(αs3) corrections and on the sensitivity to renormalization and factorization mass scales.

Higher-order corrections to QCD jets

Abstract Motivated by recent calculations of matrix elements for O(α s 3 ) parton-parton scattering processes, we evaluate the K -factors and the relative transverse-momentum distributions for jet production at high p T . We present results for a set of parton-parton subprocesses involving quarks of different flavours, in the framework of a general analysis of all one-loop QCD corrections.

Next to leading order bremsstrahlung contribution to prompt-photon production

Abstract We calculate, to the next to leading order, the bremsstrahlung contribution to the inclusive prompt-photon cross section in hadron-hadron collisions. We discuss the possible inputs for the parton-into-photon fragmentation functions, as well as the fragmentation scale depedence of the full inclusive next to leading order prediction. The effect of these corrections is shown to be quite significant in the small- x t range, x t ∼ O(10 −2 ) at collider energies, and the importance of the gluon into photon fragmentation process is stressed.

Next-to-leading order determination of pion fragmentation functions

We perform a complete next to leading order evaluation of inclusive neutral pion production from hadronic colliders which is based on the knowledge of the pion fragmentation functions at next to leading order. This problem has been tackled for the first time using different approaches. Predictions at LHC are given with the estimate of the theoretical uncertainty.Abstract We perform a complete next-to-leading order evaluation of inclusive neutral pion production from hadronic colliders which is based on the knowledge of the pion fragmentation functions at next to leading order. This problem has been tackled for the first time using different approaches. Predictions at LHC are given with the estimate of the theoretical uncertainty.

Light scattering by particles of arbitrary shape: a fractal approach

The intensity of light scattered by particles of dimensions that are large compared with the incident wavelength depends on the particles’ geometry. We propose to model the surface irregularities by a function of fractal type; then in the framework of an eikonal picture we derive an expression for the scattering amplitude that takes into account exactly the shape of the scattering surface. Our results show that the scattered intensity permits discrimination between smooth and rough surfaces and also between the sizes of the irregularities.

Jet production in hadronic collisions to0(α s 3 )

We present the full0(αs3) QCD corrections to jet production within a small opening angle δ at large transverse momenta for all partonic subprocesses. Results for CERN and Tevatron colliders are given with particular emphasis on the sensitivity to renormalization and factorization mass scales.

Higher order QCD corrections to the photoproduction of a direct photon at HERA

The contribution of resolved photons to the photoproduction cross section of direct photons is reexamined. Higher order,O(α2αs), QCD corrections to this contribution are calculated and turn out to be important at HERA energies. The observation of direct photons in the medium-p⊥ range (p⊥∼5 GeV/c) should provide the opportunity to measure the gluon content of the photon.

Higher order corrections to QCD jets: Gluon-gluon processes

Abstract We evaluate the full o(αs3) cross sections for the processes g+g→g+X and g+g→q+X, relevant for jet production at large pT at very high energies. Some phenomenological applications of our results at Sp p S and Tevatron energies are also presented.

Possible bounds on compositeness from inclusive one jet production in large hadron colliders

Abstract By analyzing deviations from QCD for inclusive jet production, we derive bounds that could be obtained at LHC and SSC on the compositeness scale Λ q (Λ g ) which governs a typical four-quark (two-quark-two-gluon) contact interaction. We also study similar bounds for a two-quark-two-lepton contact term from dilepton production.

Testing for a possible strong-interacting electroweak symmetry breaking sector at LHC and SSC

Abstract We study gauge boson pair production at future hadron colliders in the presence of a strong interacting electroweak symmetry breaking sector. The calculations are carried out within the BESS model, with parameters limited from presented experiments as well as in view of future attainable LEP precisions. The fusion production mechanism via longitudinal WW scattering is compared to the q q annihilation mechanism going through vector resonance that is typical of the BESS model. The q q mechanism is found to be in general largely dominant at LHC, making the calculated event rates observable at the projected LHC energy and luminosity, for reasonable ranges of the BESS parameters. Detailed studies of background and statistical significance of signals versus background are made both at LHC and SSC.