D. Treleani

Double parton scattering background to Higgs boson production at the CERN LHC

The experimental capability of recognizing the presence of b quarks in complex hadronic final states has addressed the attention towards final states with b\bar{b} pairs for observing the production of the Higgs boson at the LHC, in the intermediate Higgs mass range.We point out that double parton scattering processes are going to represent a sizeable background to the process.

Disentangling correlations in multiple parton interactions

Multiple Parton Interactions are the tool to obtain information on the correlations between partons in the hadron structure. Partons may be correlated in all degrees of freedom and all different correlation terms contribute to the cross section. The contributions due to the different parton flavors can be isolated, at least to some extent, by selecting properly the final state. In the case of high energy proton-proton collisions, the effects of correlations in the transverse coordinates and in fractional momenta are, on the contrary, unavoidably mixed in the final observables. The standard way to quantify the strength of double parton interactions is by the value of the effective cross section and a small value of the effective cross section may be originated both by the relatively short transverse distance between the pairs of partons undergoing the double interaction and by a large dispersion of the distribution in multiplicity of the multiparton distributions. The aim of the present paper is to show how the effects of longitudinal and transverse correlations may be disentangled by taking into account the additional information provided by double parton interactions in high energy proton-deuteron collisions.

Measuring double-parton distributions in nucleons at proton-nucleus colliders.

We predict a strong enhancement of multijet production in proton-nucleus collisions at collider energies, as compared to a naive expectation of a cross section similar to A. The study of the process would allow one to measure, for the first time, the double-parton distribution functions in a nucleon in a model-independent way and hence to study both the longitudinal and the transverse correlations of partons.

Double parton scatterings in b quark pairs production at the CERN LHC

A sizable rate of events where two pairs of b quarks are produced contemporarily is foreseen at the CERN LHC, as a consequence of the large parton luminosity. At very high energies both single and double parton scatterings contribute to the process, the latter mechanisms, although power suppressed, giving the dominant contribution to the integrated cross section.

Color Fluctuations in the Nucleon in High-Energy Scattering

We study quantum fluctuations of the nucleons parton densities by combining QCD factorization for hard processes with the notion of cross section fluctuations in soft diffraction. The fluctuations of the small-x gluon density are related to the ratio of inelastic and elastic vector meson production in ep scattering. A simple dynamical model explains the HERA data and predicts the x and Q2 dependence of the ratio. In pp/p[over ]p scattering, fluctuations enhance multiple hard processes (but cannot explain the Tevatron CDF data), and reduce gap survival in central exclusive diffraction.

Double parton scattering, diffraction and effective cross section

The rates of multiparton collisions in high energy hadronic interactions provide information on the typical transverse distances between partons in the hadron structure. The different configurations of the hadron in transverse space are, on the other hand, at the origin of hadron diffraction. The relation between the two phenomena is explored in an eikonal model of hadronic interactions.

Scale factor in double parton collisions and parton densities in transverse space

The scale factor

Fractional momentum correlations in multiple production of W bosons and of b b ¯ pairs in high energy p p collisions

{\ensuremath{\sigma}}_{\mathrm{eff}},

Minijets and the two-body parton correlation

which characterizes double parton collisions in high energy hadron interactions, is a direct manifestation of the distribution of the interacting partons in transverse space, in such a way that different distributions give rise to different values of

Hard parton rescatterings and minijets in nuclear collisions at the CERN LHC

{\ensuremath{\sigma}}_{\mathrm{eff}}