Single Diffractive Cross Sections Research Articles

Production mechanisms of open heavy flavor mesons in high-multiplicity events

In this proceeding we discuss different mechanisms of open-heavy flavor meson production which contribute to inclusive and single diffractive cross-sections. For the case of inclusive production we demonstrate that the three-Pomeron fusion is significant for the DD-meson production in the kinematics of small transverse momenta p_{T}pT, as well as in large-multiplicity events. Its inclusion allows to improve significantly the description of experimental data. We also analyzed the diffractive production and found that due to gap survival factors it constitutes 0.5 percent of the inclusive production. The expected dependence on event multiplicity in this channel is significantly milder than for inclusive case.

Unitarisation dependence of diffractive scattering in light of high-energy collider data

We study the consequences of high-energy collider data on the best fits to total, elastic, inelastic, and single-diffractive cross sections for pp and poverline{p} scattering using different unitarisation schemes. We find that the data are well fitted both by eikonal and U-matrix schemes, but that diffractive data prefer the U-matrix. Both schemes may be generalised by means of an additional parameter; however, this yields only marginal improvements to the fits. We provide estimates for ρ, the ratio of the real part to the imaginary part of the elastic amplitude, for the different fits. We comment on the effect of the different schemes on present and future cosmic ray data.

Investigating the impact of the partonic structure on the description of hadronic collisions at high energies

The impact of the partonic structure on the description of the hadronic cross-sections is investigated considering a multichannel eikonal model based on the Good–Walker approach. The total, elastic and single diffractive cross-sections are estimated considering different parametrizations for the parton distribution functions and the predictions are compared with the experimental data for proton–proton [Formula: see text] and antiproton–proton [Formula: see text] collisions. We show that the description of the high-energy behavior of the hadronic cross-sections is sensitive to the partonic structure.

Model of diffractive excitation in pp collisions at high energies

A phenomenological model for the description of the single and double diffractive excitation in $pp$ collisions at high energies is presented. Considering the Good -- Walker approach, we propose a model for the eigenstates of the scattering operator and for the treatment of the interaction between them, with the high energy behavior of the cross section driven by perturbative QCD. The behavior of the total, elastic, single and double diffractive cross sections are analyzed and predictions for the energies of Run 3 of the LHC and those of the Cosmic Rays experiments are derived. We demonstrate that the model describes the current data for the energy dependence of the cross sections. A comparison with the recent data for the $\rho$ parameter and the differential elastic cross section are also presented and shortcomings of the current model are discussed.

Total, Elastic and Single Diffractive Cross Sections for LHC Energies

In this contribution we provide predictions for total, elastic and single diffractive cross sections calculated for the proton-proton collisions at the LHC in centre-of-mass energies of 0.9, 7, 8 and 14 TeV. We consider the framework of the Miettinen-Pumplin model which correctly describes the lower energy data available by Fermilab-Tevatron. Our predictions are based on the fitted parameters of the model for the Tevatron measurements and for TOTEM-LHC measurements at 7 TeV. We extrapolate the results for the higher energies runs of LHC and provide predictions for them. We verify that those prediction are in agreement with the recent CERN-ATLAS Collaboration result.

Diffractive Production of Quarkonium in p-A Collisions at LHC

In the present work, we investigated the exclusive diffractive production of charmonium in pronton-nucleus collisions at the Large Hadron Collider (LHC) energies. Such exclusive production reactions possess a cleaner experimental signal than inclusive production once it is characterized by low multiplicity of particles between final produced state and the incident protons of collider beam. The considered theoretical framework was the perturbative model of Quantum Cromodynamics (QCD) for the Pomeron exchange. In particular, we have used the resolved Pomeron model which depends on the Pomeron flux and Pomeron parton distribution functions. The main goal is to provide predictions for the single diffractive cross section for the J/Psi meson production at the energies of 5.02 TeV and 8.8 TeV. We have shown that a measurement is feasible as the order of magnitude is 400 microbarns even absorption corrections. Furthermore, we analyze the ratio of the diffractive to inclusive cross section which allows theoretical uncertainties to be canceled, mostly those associated to approximations performed in inclusive case.

Hard diffraction with dynamic gap survival

We present a new framework for the modelling of hard diffraction in pp and ppbar collisions. It starts from the the approach pioneered by Ingelman and Schlein, wherein the single diffractive cross section is factorized into a Pomeron flux and a Pomeron PDF. To this it adds a dynamically calculated rapidity gap survival factor, derived from the modelling of multiparton interactions. This factor is not relevant for diffraction in ep collisions, giving non-universality between HERA and Tevatron diffractive event rates. The model has been implemented in Pythia 8 and provides a complete description of the hadronic state associated with any hard single diffractive process. Comparisons with ppbar and pp data reveal improvement in the description of single diffractive events.

Simulation of diffraction dissociation in quark-diquark representation

A low mass single diffraction dissociation model based on the quark-diquark representation of hadron-nucleon interaction is proposed. The mass spectra of nucleon-pion system are compared with experimental data and predictions of other models. The hadron-nucleus single diffraction cross-sections are calculated in the framework of the Glauber-Gribov model for integral cross-sections. The model predictions are compared with experimental data for the various distributions of secondary particles produced in the hadron-nucleus interactions in the momentum range 31-320GeV/c.

CGC/saturation approach for soft interactions at high energy: a two channel model

In this paper we continue the development of a model for strong interactions at high energy, based on two ingredients: the CGC/saturation approach and the BFKL Pomeron. In our approach, the unknown mechanism of confinement of quarks and gluons is characterized by several numerical parameters, which are extracted from the experimental data. We demonstrate that the two channel model successfully describes the experimental data, including both the value of the elastic slope and the energy behavior of the single diffraction cross section. We show that the disagreement with the experimental data of our previous single channel eikonal model (Gotsman et al., Eur Phys J C 75:1–18, 2015) stems from the simplified approach used for the hadron structure and is not related to our principal theoretical input, based on the CGC/saturation approach.

A model for strong interactions at high energy based on the CGC/saturation approach

We present our first attempt to develop a model for soft interactions at high energy, based on the BFKL Pomeron and the CGC/saturation approach. We construct an eikonal-type model, whose opacity is determined by the exchange of the dressed BFKL Pomeron. The Green's function of the Pomeron is calculated in the framework of the CGC/saturation approach. Using five parameters we achieve a good description of the experimental data at high energies ( $W\,\geq\,0.546\,TeV$). The model results in different behaviour for the single and double diffraction cross sections at high energies. The single diffraction cross section reaches a saturated value (about 10 mb) at high energies, while the double diffraction cross section continues growing slowly

Hard Diffraction in \textsf {PYTHIA8}

We present an overview of the options for diffraction implemented in the general-purpose event generator PYTHIA8. We review the existing model for low- and high-mass soft diffraction and present a new model for hard diffraction in pp and pp¯ collisions. Both models use the Pomeron approach pioneered by Ingelman and Schlein, factorising the single diffractive cross section into a Pomeron flux and a Pomeron PDF. The model for hard diffraction is implemented as a part of the multiparton interactions framework, thereby introducing a dynamical rapidity gap survival probability that explicitly breaks factorisation.

Exclusivepp→ppπ0reaction at high energies

The amplitudes for the $pp\ensuremath{\rightarrow}pp{\ensuremath{\pi}}^{0}$ process applicable at high energy are discussed in detail. Both diffractive bremsstrahlung (Drell-Hiida-Deck-type model), photon-photon and photon-omega exchange mechanisms are included in the calculation. Large cross sections of the order of mb are predicted. The corresponding differential cross sections in rapidities and transverse momenta of outgoing protons and pions as well as relative azimuthal angle between outgoing protons are calculated for RHIC and LHC energies. The hadronic bremsstrahlung contributions dominate at large (forward, backward) pion rapidities. The diffractive nonresonant background contributes at small ${\ensuremath{\pi}}^{0}p$ invariant mass and could be therefore misinterpreted as the Roper resonance. We predict strong dependence of the slope in $t$ (squared four-momentum transfer between ingoing and outgoing proton) on the mass of the supplementary excited ${\ensuremath{\pi}}^{0}p$ system. At high energies and midrapidities, the photon-photon contribution dominates over the diffractive components, however, the corresponding cross section is rather small. The photon-odderon and odderon-photon contributions are included in addition and first estimates (upper limits) of their contributions to rapidity and transverse momentum distribution of neutral pions are presented. We suggest a search for the odderon contribution at midrapidity and at ${p}_{\ensuremath{\perp},{\ensuremath{\pi}}^{0}}\ensuremath{\sim}0.5\text{ }\text{ }\mathrm{GeV}$. Our predictions are ready for verification at RHIC and LHC. The bremsstrahlung mechanisms discussed here contribute also to the $pp\ensuremath{\rightarrow}p(n{\ensuremath{\pi}}^{+})$ reaction. Both channels give a sizable contribution to the low-mass single diffractive cross section and must be included in extrapolating the measured experimental single diffractive cross section.

Estimate of the single diffractive heavy quark production in heavy ion collisions at the CERN LHC

The single diffractive cross section for heavy quarks production is calculated at next-to-leading order (for nucleus-nucleus collisions. Such processes are expected to occur at the LHC, where the nuclei involved are lead at $\sqrt{s}=5.5\text{ }\text{ }\mathrm{TeV}$ and calcium at $\sqrt{s}=6.3\text{ }\text{ }\mathrm{TeV}$. We start using the hard diffractive factorization formalism, taking into account a recent experimental parametrization for the Pomeron structure function (DPDF). Absorptive corrections are accounted for by the multiple Pomeron contributions considering a gap survival probability, where its theoretical uncertainty for nuclear collisions is discussed. We estimate the diffractive ratios for the single diffraction process in nuclear coherent/incoherent collisions at the LHC.

Diffractive quarkonium production in association with a photon at the LHC

The rates for diffractive quarkonium plus prompt-photon associated production at the LHC are estimated. The theoretical framework considered in the J/Ψ (or ϒ) production associated with a direct photon at the hadron collider is the non-relativistic QCD (NRQCD) factorization formalism. The corresponding single diffractive cross section is computed based on the hard diffractive scattering factorization supplemented by absorptive corrections. Such processes are sensitive to the gluon content of the Pomeron at small Bjorken-x and they may also be a good place to test the different available mechanisms for quarkonium production at hadron colliders.

A QCD motivated model for soft interactions at high energies

In this paper we develop an approach to soft scattering processes at high energies which is based on two elements: the Good–Walker mechanism for low mass diffraction and multi-pomeron interactions for high mass diffraction. The principal idea, which 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′ℙ≈0.01 GeV−2), where perturbative QCD is valid. The value of the pomeron slope α′ℙ is obtained from a fit to the experimental data. Using this theoretical approach, we suggest a model that fits all soft data in the ISR-Tevatron energy range: total, elastic, single and double diffractive cross sections, as well as the 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 we obtain a value for this observable that is smaller than 1% at the LHC energy range.

Diffractive dissociation including Pomeron loops in zero transverse dimensions

We have recently studied the QCD pomeron loop evolution equations in zero transverse dimensions [Phys. Rev. D 73, 094014 (2006)]. Using the techniques developed in [Phys. Rev. D 73, 094014 (2006)] together with the AGK cutting rules, we present a calculation of single, double and central diffractive cross sections (for large diffractive masses and large rapidity gaps) in zero transverse dimensions in which all dominant pomeron loop graphs are consistently summed. We find that the diffractive cross sections unitarise at large energies and that they are suppressed by powers of ${\ensuremath{\alpha}}_{s}$. Our calculation is expected to expose some of the diffractive physics in hadron-hadron collisions at high energy.

Total, elastic and diffractive cross sections at LHC in the Miettinen–Pumplin model

Predictions for the total, elastic and single diffractive cross sections calculated for the LHC in the framework of the Miettinen–Pumplin model are presented. The total cross section is expected to be 15% smaller than that determined by Donnachie and Landshoff in the model with soft pomeron. The diffractive cross section is almost constant in the Tevatron-LHC energy range.

Soft diffraction at the LHC and properties of the Pomeron

We briefly describe a model for soft diffraction. The model description of ISR, Sp p S and Tevatron data, and the predictions of the total, elastic, single and double diffractive cross sections at the LHC can be found in the original paper. Here we address issues raised at Diffraction 2000, in particular concerning the nature of the resulting Pomeron trajectory.

Inelastic Diffraction and Color-Singlet Gluon Clusters in High-Energy Hadron-Hadron and Lepton-Hadron Collisions

It is proposed that the ``colorless'' objects which manifest themselves in large-rapidity-gap events are color-singlet gluon clusters due to self-organized criticality (SOC), and that optical-geometrical concepts and methods are useful in examining the space-time properties of such objects. A simple analytical expression for the $t$ dependence of the inelastic single diffractive cross section $d\ensuremath{\sigma}/dt$ ( $t$ is the four-momentum transfer squared) is derived. Comparison with existing data and predictions for future experiments are presented. The main differences and similarities between the SOC approach and the ``partons in the Pomeron (Pomeron and Reggeon)'' approach are discussed.

Evidence for ξ- and t-dependent damping of the flux in the proton

We show that a triple-Regge parametrization of inclusive single diffraction agrees with the data in the following two domains: (a) xi > 0.03 at all t, (b) |t| > 1 GeV^2 at all xi. Since the triple-Regge parametrization fails when applied to the full xi-t range of the total single-diffractive cross section, we conclude that damping occurs only at low-xi and low-|t|. We give a (``toy'') parametrization of the damping factor, D(xi), valid at low-|t|, which describes the diffractive differential cross-section (dsig/dt) data at the ISR and roughly accounts for the observed s-dependence of diffractive total cross-section up to Tevatron energies. However, an effective damping factor calculated for the CDF fitted function for dsig/dxidt at sqrt(s} = 1800 GeV and |t| = 0.05 GeV^2, suggests that, at fixed-xi, damping increases as s increases. We conjecture that, in the regions where the triple-Regge formalism describes the data and there is no evidence of damping, factorization is valid and the Pomeron-flux-factor may be universal. With the assumption that the observed damping is due to multi-Pomeron exchange, our results imply that the recent UA8 demonstration that the effective Pomeron trajectory flattens for |t| > 1 GeV$^2 is evidence for the onset of the perturbative 2-gluon pomeron. Our damping results may also shed some light on the self-consistency of recent measurements of hard-diffractive jet production cross sections in the UA8, CDF and ZEUS experiments.