128 research outputs found
Measurement of hard double-parton interactions in W(→ℓν) + 2-jet events at √<span style="text-decoration:overline">s</span>=7 TeV with the ATLAS detector
No full textThe production of W bosons in association with two jets in proton–proton collisions at a centre-of-mass energy of √<span style="text-decoration:overline">s</span>=7 TeV has been analysed for the presence of double-parton interactions using data corresponding to an integrated luminosity of 36 pb−1, collected with the ATLAS detector at the Large Hadron Collider. The fraction of events arising from double-parton interactions, f(D)DP, has been measured through the pT balance between the two jets and amounts to f(D)DP = 0.08 ± 0.01 (stat.) ± 0.02 (sys.) for jets with transverse momentum pT > 20 GeV and rapidity |y| < 2.8. This corresponds to a measurement of the effective area parameter for hard double-parton interactions of σeff = 15 ± 3 (stat.) +5−3 (sys.) mb
A double parton scattering background to Higgs boson production at the LHC
No full textThe 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
PRODUCTION AND DETECTION OF DOUBLY CHARMED TETRAQUARKS.
No full textAbstract: The feasibility of tetraquark detection is studied. For the cc (u) over bar(d) over bar tetraquark we show that in present (SELEX, Tevatron, RHIC) and future facilities (LHCb, ALICE) the production rate is promising and we propose some detectable decay channels
Hard Parton Rescatterings and Minijets in Nuclear Collisions at LHC
No full textThe average number of minijets and the corresponding transverse energy in heavy ion collisions are evaluated by including explicitly semi-hard parton rescatterings in the dynamics of the interaction. At the LHC semi-hard rescatterings have a sizable effect on global characteristics of the typical inelastic event. An interesting feature is that the dependence on the cutoff which separates soft and hard parton interactions becomes less critical after taking rescatterings into account
CRONIN EFFECT AND ENERGY CONSERVATION CONSTRAINTS IN HIGH-ENERGY PROTON NUCLEUS COLLISIONS
No full textAbstract: We estimate the Cronin effect in pA collisions at the CERN LHC and at the BNL 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 multiparton 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 pi(0) production in d+Au collisions at roots=200A GeV
Disentangling correlations in multiple parton interactions.
No full textMultiple 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
Inclusive and 'exclusive' cross sections in the regime of multiple parton collisions
No full textThe large luminosity and the increased kinematical domain accessible at the LHC will allow one to isolate large numbers of events with multiple parton collisions. Interestingly, the hadron is probed in different points simultaneously in the process, which allows one 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 pt 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 detail 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
Double parton scattering, diffraction and effective cross section.
No full textThe 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
Collisions of protons with light nuclei shed new light on nucleon structure
No full textThe high rates of multiparton interactions at the LHC can provide a unique opportunity to study the multiparton structure of the hadron. To this purpose high-energy collisions of protons with nuclei are particularly suitable. The rates of multiparton 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 multiparton interactions in pp collisions, the possibility of changing the atomic mass number thus provides 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 multiparton structure can be disentangled, by comparing the rates of multiple parton interactions in collisions of protons with D, 3H, and 3He
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