Generalized parton distributions and rapidity gap survival in exclusive diffractive pp scattering (original) (raw)
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Physics Letters B - PHYS LETT B, 2010
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Diffractive dissociation of gluons into heavy quark–antiquark pairs in proton–proton collisions
Physics Letters B, 2014
We discuss diffractive dissociation of gluons into heavy quark pairs. The particular mechanism is similar to the diffractive dissociation of virtual photons into quarks, which drives diffractive deep inelastic production of charm in the low-mass diffraction, or large β-region. There, it can be understood, with some reservations, in terms of a valence heavy quark content of the Pomeron. The amplitude for the gp → QQp is derived in the impact parameter and momentum space. The cross section for single diffractive pp → QQpX is calculated as a convolution of the elementary cross section and gluon distribution in the proton. Integrated cross section and the differential distributions in e.g. transverse momentum and rapidity of the charm and bottom quark and antiquark, as well as the quark-antiquark invariant mass are calculated for the nominal LHC energy for different unintegrated gluon distributions from the literature. The ratio of the bottom-to-charm cross sections are shown and discussed as a function of several kinematical variables.
Transverse nucleon structure and diagnostics of hard parton-parton processes at LHC
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Soft processes at high energy without soft Pomeron: a QCD motivated model
2008
In this paper we develop a QCD motivated model for both hard and soft interactions at high energies. In this model the long distance behavior of the scattering amplitude is determined by the approximate solution to the non-linear evolution equation for parton system in the saturation domain. All phenomenological parameters for dipole-proton interaction were fitted from the deep inelastic scattering data and the soft processes are described with only one new parameter, related to the wave function of hadron. It turns out that we do not need to introduce the so called soft Pomeron that has been used in high energy phenomenology for four decades. The model described all data on soft interactions: the values of total, elastic and diffractive cross sections as well as their sss and ttt behavior. The value for the survival probability of the diffractive Higgs production is calculated being less 1% for the LHC energy range.
A QCD motivated model for soft interactions at high energies
The European Physical Journal C, 2008
In this paper we develop an approach to soft scattering processes at high energies, which is based on two mechanisms: Good-Walker mechanism for low mass diffraction and multi-Pomeron interactions for high mass diffraction. The pricipal idea, that allows us to specify the theory for Pomeron interactions, is that the so called soft processes occur at rather short distances (r 2 ∝ 1/ < p t > 2 ∝ α ′ IP ≈ 0.01 GeV −2 ), where perturbative QCD is valid. The value of the Pomeron slope α ′ IP was obtained from the fit to experimental data. Using this theoretical approach we suggest a model that fits all soft data in the ISR-Tevatron energy range, the total, elastic, single and double diffractive cross sections, including t dependence of the differential elastic cross section, and the mass dependence of single diffraction. In this model we calculate the survival probability of diffractive Higgs production, and obtained a value for this observable, which is smaller than 1% at the LHC energy range.
Physical Review D
We consider a novel class of hard branching hadronic processes a þ b ! c þ d þ e, where hadrons c and d have large and nearly opposite transverse momenta and large invariant energy, which is a finite fraction of the total invariant energy. We use color transparency logic to argue that these processes can be used to study quark generalized parton distributions (GPDs) for baryons and mesons in hadron collisions, hence complementing and adding to the studies of GPDs in the exclusive deep inelastic scattering processes. We propose that a number of GPDs can be investigated in hadron facilities such as Japan Proton Accelerator Research Complex facility and Gesellschaft für Schwerionenforschung-Facility for Antiproton and Ion Research project. In this work, the GPDs for the nucleon and for the N ! Á transition are studied in the reaction N þ N ! N þ þ B, where N, , and B are a nucleon, a pion, and a baryon (nucleon or Á), respectively, with a large momentum transfer between B (or) and the incident nucleon. In particular, the Efremov-Radyushkin-Brodsky-Lepage region of the GPDs can be measured in such exclusive reactions. We estimate the cross section of the processes N þ N ! N þ þ B by using current models for relevant GPDs and information about large angle N reactions. We find that it will be feasible to measure these cross sections at the high-energy hadron facilities and to get novel information about the nucleon structure, for example, contributions of quark orbital angular momenta to the nucleon spin. The studies of N ! Á transition GPDs could be valuable also for investigating electromagnetic properties of the transition.
Hard probes in heavy ion collisions at the LHC: heavy flavour physics
We present the results from the heavy quarks and quarkonia working group. This report gives benchmark heavy quark and quarkonium cross sections for pp and pA collisions at the LHC against which the AA rates can be compared in the study of the quark-gluon plasma. We also provide an assessment of the theoretical uncertainties in these benchmarks. We then discuss some of the cold matter effects on quarkonia production, including nuclear absorption, scattering by produced hadrons, and energy loss in the medium. Hot matter effects that could reduce the observed quarkonium rates such as colour screening and thermal activation are then discussed. Possible quarkonium enhancement through coalescence of uncorrelated heavy quarks and antiquarks is also described. Finally, we discuss the capabilities of the LHC detectors to measure heavy quarks and quarkonia as well as the Monte Carlo generators used in the data analysis. VII CTEQ6M 4.75 1 1 with ¥ defined as above but now replaces. 2.1. Coverage in Charm Production We first study the range of c values that contribute to charm production. This question is relevant for understanding whether the current parameterizations of nuclear densities allow safe extrapolations. We also want to establish whether the constraints set by charm measurements in pPb collisions cover c ranges which are relevant for PbPb. As a reference, we shall use parameter set 8 U here and limit ourselves to LO predictions. We shall consider the full pseudorapidity range as well as limited pseudorapidity regions defined by the acceptance coverage typical of ALICE. In particular, we consider the central region, 1 1 g 0.9, and the forward region, 2.5 g g 4. The left (right) plot in Fig. 3.1 shows the differential rate distribution for production over the full (central) pseudorapidity range as a function of c d , the momentum fraction of partons in the beam traveling in the positive direction. The c 7 distribution is identical for pp and PbPb collisions, while the c d and c 7 distributions are interchanged for pPb and Pbp collisions. The same distributions, obtained for charm pairs in the forward pseudorapidity regions are given in Fig. 3.2, where the two peak structures (right peak) variables. In the case of central production, we note that the bulk of the cross section comes from c values peaked at 10 # t. The gluon density of the proton in this region is well known, thanks to the HERA data. No data are, however, available for the nuclear densities in this c region, at least not in a range of 7 relevant for charm production. We see that the c distributions for Pbp and PbPb collisions are very similar in shape. This suggests that a determination of nuclear corrections to the nucleon PDFs extracted from a Pbp run would be sufficient to properly predict the PbPb behaviour. In the case of forward production, the c ranges probed inside the two beams are clearly asym
Multi-parton interactions at the LHC
2011
We review the recent progress in the theoretical description and experimental observation of multiple parton interactions. Subjects covered include experimental measurements of minimum bias interactions and of the underlying event, models of soft physics implemented in Monte Carlo generators, developments in the theoretical description of multiple parton interactions and phenomenological studies of double parton scattering. This article stems from contributions presented at the Helmholtz Alliance workshop on "Multi-Parton Interactions at the LHC", DESY Hamburg, 13-15 September 2010.