arXiv subjects

Daniele Treleani

Publications and source records attributed to Daniele Treleani.

17 recordsLinked to original sources

arXiv2018

About Double Parton Scattering at Short Relative Transverse Distances

By working out the kinematics of double parton scattering at short relative transverse distances, we obtain an explicit link between the transverse centres of mass, of the two hard partonic interactions, and the contributions to the process, due to pairs of interacting partons generated by perturbative splitting. One my thus foresee the interesting possibility of discriminating experimentally between contributions to the double parton scattering cross section, due to interacting parton pairs originated by independent evolution, and contributions, due to interacting parton pairs generated by splitting.

hep-ph↗

arXiv2016

A Brief Comment on Multi-Gluon Amplitudes and Double Parton Interactions

A typical contribution to a color ordered multi-gluon amplitude, which can split into two weakly correlated two-body gluon scattering amplitudes and may thus contribute to a Double Parton Interaction, is briefly discussed. We find that the color ordered amplitude is not enhanced in the typical configuration generated by a DPI, where the transverse momenta of final state gluons are compensated pairwise, while a dominant contribution to the multi-gluon amplitude is due to terms proportional to the fusion amplitude of two initial state gluons. Which corresponds to an amplitude effectively describing a two rather than a three-body partonic interaction.

hep-ph↗

arXiv2016

A Brief Comment on Multi-Gluon Amplitudes and Double Parton Interactions

A simplest case, where a contribution to a color ordered multi-gluon amplitude, describing a three body partonic interaction, can split into two weakly correlated two-body gluon scattering amplitudes and may thus contribute to a Double Parton Interaction, is briefly discussed. We find that the color ordered amplitude is not enhanced in the typical configuration generated by a DPI, where the transverse momenta of final state gluons are compensated pairwise, while a dominant contribution to the multi-gluon amplitude is due to terms proportional to the fusion amplitude of two initial state gluons. Which corresponds to an amplitude effectively describing a two rather than a three-body partonic interaction.

hep-ph↗

arXiv2014

Progress in Double Parton Scattering Studies

An overview of theoretical and experimental progress in double parton scattering (DPS) is presented. The theoretical topics cover factorization in DPS, models for double parton distributions and DPS in charm production and nuclear collisions. On the experimental side, CMS results for dijet and double J/ψ production, in light of DPS, as well as first results for the 4-jet channel are presented. ALICE reports on a study of open charm and J/ψ multiplicity dependence.

hep-ph↗

arXiv2013

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.

hep-ph↗

arXiv2012

Collisions of protons with light nuclei shed new light on nucleon structure

The high rates of multi-parton interactions at the LHC can provide a unique opportunity to study the multi-parton structure of the hadron. To this purpose high energy collisions of protons with nuclei are particularly suitable. The rates of multi-parton interactions depend in fact both on the partonic multiplicities and on the distributions of partons in transverse space, which produce different effects on the cross section in pA collisions, as a function of the atomic mass number A. Differently with respect to the case of multi-parton interactions in pp collisions, the possibility of changing the atomic mass number provides thus an additional handle to distinguish the diverse contributions. Some relevant features of double parton interactions in pD collisions have been discussed in a previous paper. In the present paper we show how the effects of double and triple correlation terms of the multi-parton structure can be disentangled, by comparing the rates of multiple parton interactions in collisions of protons with D, Tritium and 3He.

hep-ph↗

arXiv2011

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.

hep-ph↗

arXiv2009

Inclusive and "exclusive" cross sections in the regime of multiple parton collisions

The large luminosity and the increased kinematical domain accessible at the LHC will allow to isolate large numbers of events with multiple parton collisions. Interestingly, the hadron is probed in different points contemporarily in the process, which allows to obtain information on the correlations between partons in the hadron structure. The whole experimentally accessible information on multiple parton collisions consists in the probability distribution of the elementary interactions, while the inclusive cross sections, usually considered in large p_t processes, acquire a precise statistical meaning as moments of the multiplicity distribution. Conversely different and more "exclusive" cross sections become experimentally viable, providing complementary information on the interaction dynamics. The matter is discussed in details in the case of hadron-hadron collisions and the role of parton correlations is outlined both in the inclusive and in the "exclusive" cross sections.

hep-ph↗

arXiv2008

A multi-channel Poissonian model for multi-parton scatterings

Multiple parton interactions are typically implemented in Montecarlo codes by assuming a Poissonian distribution of collisions with average number depending on the impact parameter. A possible generalization, which links the process to hadronic diffraction, is shortly discussed.

hep-ph↗

arXiv2007

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 exploted in an eikonal model of hadronic interactions.

hep-ph↗

arXiv2004

Cronin effect and energy conservation constraints in high energy proton-nucleus collisions

We estimate the Cronin effect in pA collisions at the CERN LHC and at RHIC, using a Glauber-Eikonal model of initial state multiparton interactions. For a correct determination of the initial parton flux, we upgrade the model cross section, taking carefully into account all kinematical constraints of each multi-parton interaction process. As compared with previous results, derived with approximate kinematics, we obtain a softer spectrum of produced partons, while improving the agreement of the model with the recent measurements of neutral pions production in d+Au collisions at sqrt(s)=200 AGeV.

hep-ph↗

arXiv2000

Finite formation time effects in quasi-elastic $(e,e')$ scattering on nuclear targets

The problem of the final state interaction in quasi-elastic $(e,e')$ scattering at large $Q^2$, is investigated by exploiting the idea that the ejected nucleon needs a finite amount of time to assume its asymptotic form. It is shown that when the dependence of the scattering amplitude of the ejected nucleon on its virtuality is taken into account, the final state interaction is decreased. The developed approach is simpler to implement than the one based on the color transparency description of the damping of the final state interaction, and is essentially equivalent to the latter in the case of the single rescattering term. The $(e,e')$ process on the deuteron is numerically investigated and it is shown that, at $x=1$, appreciable finite formation time effects at $Q^2$ of the order of 10 (GeV/c)$^2$ are expected.

nucl-th↗

arXiv2000

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.

hep-ph↗

arXiv2000

A Hamiltonian model for multiple production in hadron-hadron collisions

A Hamiltonian eikonal model for the multiple production in high energy hadron hadron collisions is presented and worked out in the aim of providing a simple frame for many different observables of these processes. The Hamiltonian formulation ensures that it has the unitarity built in by construction and the eikonal approximation makes easier the discussion of the possible spacial inhomogeneities of the hadrons. The experimental data which are examined are the inelastic cross section and the single and double inclusive cross sections.

hep-ph↗

arXiv1997

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.

hep-ph↗

arXiv1997

Self-Similarity of the Negative Binomial Multiplicity Distributions

The negative binomial distribution is self similar: If the spectrum over the whole rapidity range gives rise to a negative binomial, in absence of correlation and if the source is unique, also a partial range in rapidity gives rise to the same distribution. The property is not seen in experimental data, which are rather consistent with the presence of a number of independent sources. When multiplicities are very large self similarity might be used to isolate individual sources is a complex production process.

hep-ph↗

arXiv1997

Minijets and the Two-Body Parton Correlation

A large number of double parton scatterings have been recently measured by CDF. The double parton scattering process measures $σ_{eff}$, a non perturbative quantity related to the hadronic transverse size and with the dimensions of a cross section. The actual value measured by CDF is considerably smaller as compared with the naive expectation, namely the value of the inelastic non diffractive cross section. The small value of $σ_{eff}$ may be an effect of the hadron structure in transverse plane. We discuss the problem by taking into account, at all orders, the two-body parton correlations in the many-body parton distributions.

hep-ph↗