Cronin effect and energy conservation constraints in pA collisions at LHC and RHIC

We evaluate the Cronin effect in pA collisions at the CERN LHC and at RHIC in the framework of Glauber-Eikonal model of initial state multiparton interactions. Taking carefully into account all kinematical constraints of each multi-parton interaction process we obtain a softening of the spectrum of produced partons, improving in this way the agreement of the model with the recent measurements of pi0 production in d+Au collisions at sqrt{s}=200 AGeV.Comment: Proceeding of 34th International Symposium on Multiparticle dynamics (ISMD), Sonoma California, 26th-1st Aug 2004, to be published in Acta Phisica Polonica

The N - Jet Inclusive Cross-Section in the Hard Pomeron Model

The inclusive production of several jets is studied in the framework of the hard pomeron model. The average jet momenta are found to be strongly ordered and growing towards the central c.m. rapidity, as expected. Strong positive correlations are found for pairs of jets neighbouring in rapidity, both in the forward-backward and forward-forward directions.Comment: 20 pages, latex, one figure (fig.2), an hard copy of fig.1 can be obtained on reques

Incoherence and Multiple Parton Interactions

At the LHC Multiple Parton Interactions will represent an important feature of the minimum bias and of the underlying event and will give important contributions in many channels of interest for the search of new physics. Different numbers of multiple collision may contribute to the production of a given final state and one should expect important interference effects in the regime where different contributions have similar rates. We show, on the contrary, that, once multiple parton interactions are identified by their different topologies, terms with different numbers of multiple parton interactions do not interfere in the final cross section.Comment: 10 pages, 3 figure

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 multi-parton 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.Comment: 23 pages, 8 figure

The double parton distributions in the hard pomeron model

We study the double parton interaction process in collisions between highly virtual $q{\bar q}$ pairs in the BFKL regime. Explicit expressions for the double parton distributions are obtained both in the case of direct coupling of the BFKL pomerons to the $q{\bar q}$ pair and in the case of triple pomeron interaction.Comment: 29 pages, 6 figure

Stripping Cross Sections in Collisions of Light Nuclei

By evaluating all the contributions of the intermediate states of the multiple scattering theory diagrams, we compute the integrated stripping cross sections of collisions among light nuclei. The resulting expressions have the simple form of a combination of total inelastic cross sections of nuclear reactions with projectile nuclei differing in the atomic mass number. We also check the accuracy of some widely used relations in heavy ion collisions.Comment: 9 pages, 4 figures, Latex fil

Multiparton scattering at the LHC

The large parton flux at high energy gives rise to events where different pairs of partons interact contemporarily with large momentum exchange. A main effect of multiple parton interactions is to generate events with many jets at relatively large transverse momenta. The large value of the heavy quarks production cross section may however give also rise a sizable rate of events with several $b$-quarks produced. We summarize the main features of multiparton interactions and make some estimate of the inclusive cross section to produce two $b{\bar b}$ pairs within the acceptance of the ALICE detector.Comment: 10 pages, 4 figures, contribution to ALICE PP

Double Parton Scatterings in High-Energy Proton-Nucleus Collisions and Partonic Correlations

The joint study of Double Parton Scatterings, in high energy proton-proton and proton-nucleus collisions, can provide a lot of information on multi-parton correlations. The multi-parton structure is in fact probed in a different way by DPS, in $p$-$p$ and in $p$-$A$ collisions. In $p$-$A$ collisions the interpretation of the experimental results may be however complicated by the presence of interference terms, which are missing in $p$-$p$. A suitable reaction channel, where interference terms are absent, is $WJJ$ production. By studying $WJJ$ production in $p$-$Pb$ collisions, we estimate that the fraction of events due to DPS may be larger by a factor 3 or 4, as compared to $p$-$p$, while the amount of the increased fraction can give a direct indication on the importance of different correlation terms.Comment: 27 pages, 9 figure