Double Diffractive Cross Sections Research Articles

A multi-channel U-Matrix model of hadron interaction at high energy

The present phenomenological study investigates a multi-channel model of high-energy hadron interactions by considering a full parton configurations space and the U-matrix unitarisation scheme of the elastic amplitude, comparing it to the two-channel model, and examining the consequences of up-to-date high-energy collider data on the best fits to various hadronic observables in pp and poverline{p} collisions. The findings of this study reveal that the data are well-fitted with the multi-channel model and that the difference compared to the two-channel one is negligible. Of particular significance is the observation that the U-matrix unitarisation is likely incompatible with uncorrelated pomeron exchange, as suggested by the equivalence between the U-matrix multi-channel and eikonal two-channel descriptions. Based on our best fit, predictions for the ρ parameter, the double diffractive cross-section, and the elastic differential cross-section are provided. We shed light on the effect of taking into account a multi-channel model on present and future cosmic ray data.

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.

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

Double Diffractive Cross-Section Measurement in the Forward Region at the LHC

The first double diffractive cross-section measurement in the very forward region has been carried out by the TOTEM experiment at the LHC with a center-of-mass energy of sqrt[s]=7 TeV. By utilizing the very forward TOTEM tracking detectors T1 and T2, which extend up to |η|=6.5, a clean sample of double diffractive pp events was extracted. From these events, we determined the cross section σDD=(116±25) μb for events where both diffractive systems have 4.7<|η|min<6.5.

Measurement of inelastic, single- and double-diffraction cross sections in proton-proton collisions at the LHC with ALICE.

Measurements of cross sections of inelastic and diffractive processes in proton–proton collisions at LHC energies were carried out with the ALICE detector. The fractions of diffractive processes in inelastic collisions were determined from a study of gaps in charged particle pseudorapidity distributions: for single diffraction (diffractive mass M X<200 GeV/c 2) sigma_{mathrm{SD}}/sigma_{mathrm {INEL}} = 0.21 pm 0.03, 0.20^{+0.07}_{-0.08}, and 0.20^{+0.04}_{-0.07}, respectively at centre-of-mass energies sqrt{s} = 0.9, 2.76mbox{, and }7~mbox{TeV}; for double diffraction (for a pseudorapidity gap Δη>3) σ DD/σ INEL=0.11±0.03,0.12±0.05, and 0.12^{+0.05}_{-0.04}, respectively at sqrt{s} = 0.9, 2.76mbox{, and }7~mbox{TeV}. To measure the inelastic cross section, beam properties were determined with van der Meer scans, and, using a simulation of diffraction adjusted to data, the following values were obtained: sigma_{mathrm{INEL}} = 62.8^{+2.4}_{-4.0} (mathrm{model}) pm1.2 (mathrm{lumi}) mb at sqrt{s} = 2.76 mbox{TeV} and 73.2^{+2.0}_{-4.6} (mathrm{model}) pm2.6 (mathrm{lumi})~mbox{mb} at sqrt{s} = 7 mbox{TeV}. The single- and double-diffractive cross sections were calculated combining relative rates of diffraction with inelastic cross sections. The results are compared to previous measurements at proton–antiproton and proton–proton colliders at lower energies, to measurements by other experiments at the LHC, and to theoretical models.

Diffraction studies with ALICE

The measurement of Single and Double Diffraction cross-sections in pp collisions by the ALICE Collaboration at √ s = 0.9, 2.76 and 7 TeV will be presented. The relevance of diffraction to the understanding of inelastic pp interactions will be discussed and the measurement of the inelastic pp cross-section will be presented. A brief status of ALICE’s studies of centrally produced systems, selected with a two-pseudorapidity gap topology, will also be given.

Results from ALICE

ALICE, the dedicated heavy-ion experiment at the LHC, has also a rich pp program benefiting from its low material budget, low magnetic field, and its extensive particle identification capabilities. The talk presents recent measurements of relevance for cosmic-ray physics. In particular, ALICE measured the inelastic, single- and doublediffractive cross-sections in pp collisions at √ s = 0.9, 2.76, and 7 TeV [1]. Further, the charged-particle pseudorapidity distribution ( dN ch / dη ) in Pb-Pb collisions at √ s NN = 2.76 TeV was measured over a large pseudorapidity range (-5.0 < η < 5.5) using collisions from displaced vertices [2]. Potential direct contributions of ALICE to cosmic-ray physics are also reviewed [3].

A Study of Diffractive Production in ALICE

The ALICE collaboration is investigating single, double and central diffractive processes in pp interactions. The single and double diffractive cross-sections are presented at 900 GeV 2.76 TeV and 7 TeV using an analysis method based on the classification of diffractive gaps. Promising early results on central diffractive processes have motivated the use of additional diffractive counters, which are currently being installed.

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.

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.

Diffractive heavy flavour production at the Tevatron and the LHC

We give predictions for diffractive heavy flavour production at the Tevatron and the LHC in leading-order approximation. In the framework of these studies we use three different models for the partonic structure of the Pomeron recently proposed by Stirling and Kunszt. These Pomeron models are, despite being fitted to the same diffractive deep inelastic HERA data, very different in their parton content and taken together provide a powerful tool to probe the structure of the Pomeron. All models satisfy GLAP evolution and show a significant Q2 dependence. We give numerical predictions for single as well as double diffractive cross sections assuming a Donnachie-Landshoff-type Pomeron flux factor.

Particle production in a hadron collider rapidity gap: the Higgs case

Production of rare particles within rapidity gaps has been proposed as a background-free signal for the detection of new physics at hadron colliders. No complete formalism accounts for such processes yet. We study a simple lowest-order QCD model for their description. Concentrating on Higgs production, we show that the calculation of the cross section pp → ppH can be embedded into existing models which successfully account for diffractive data. We extend those models to take into account single- and double-diffractive cross sections pp → HX 1 X 2 with a gap between the fragments X 1 and X 2. Using conservative scenarios, we evaluate the uncertainties in our calculation, and study the dependence of the cross section on the gap width. We predict that Higgs production within a gap of 4 units of rapidity is about 0.3 pb for a 100 GeV Higgs at the Tevatron, and almost 2 pb for a 400 GeV Higgs within a gap of 6 units at the LHC with √ s = 14 TeV.

Hadronic diffractive cross sections and the rise of the total cross section.

A model for high-energy hadronic cross sections is proposed. It is based on Regge theory and perturbative QCD, and includes soft and hard mechanisms as well as diffractive processes. The validity range of Regge-pole theory in the description of total, elastic, single-, and double-diffractive cross sections is investigated and inconsistencies found already at CERN LHC and/or SSC energies. Examining unitarity constraints, modifications of the cross section formulas are proposed which allow a continued use of formulas in the Regge spirit to describe elastic and diffractive events. The nondiffractive cross section is allowed to rise at a rate consistent with unitarization of multiple parton-parton scatterings. However, in our picture, the rise of the total cross section with increasing energy is only partly due to the minijet cross sections; the diffractive topologies rise as well. Fully differential distributions are given and convenient parametrizations derived for the integrated rates of elastic and diffractive events. Predictions for the various partial cross sections at Fermilab Tevatron, LHC, and SSC energies are given and compared to other estimates.

New Bound for Single and Double Diffraction Cross Sections in Identical Particle Collisions

New Bound for Single and Double Diffraction Cross Sections in Identical Particle Collisions

Analysis of double diffraction dissociation in nucleon-nucleon collisions at the CERN ISR

Final results from combined measurements of single and double diffraction of protons neutrons into (N π) and (N ππ) final states are presented. The experiments were performed at the CERN Intersecting Storage Rings with the Split Field Magnet detector using proton and deuteron colliding beams. The general properties of the dissociating vertex in single and double diffractive reactions are essentially identical. Mass spectra and decay angular distributions are compared with the predictions of a dual resonant Deck model. Decay angular correlations and a strong slope-mass correlation are observed also in double diffraction. Detailed tests of factorization indicate its validity over the full range of all kinematical variables and in their correlations. A model-independent analysis gives strong support to the peripheral nature of diffraction dissociation, with double diffraction being concentrated in a narrow gaussian ring at the edge of the proton. Both the exclusive and the inclusive double diffractive cross sections display a marked increase over the ISR energy range. Both mechanisms yield comparable contributions to the peripheral increase of the total pp cross section, with an approximate saturation of the Pumplin bound.

Inclusive single and double diffractive dissociations inK + p interactions at 32 GeV/c

We study single and double inclusive diffractive production in a 32 GeV/c K+p experiment in MIRABELLE at the Serpukhov accelerator. From reactionsK+p→K++X+ andK+p→X++p we determine the total proton and kaon single diffractive dissociation cross sections\(\sigma (p\xrightarrow{{K^ + }}p_D ) = 0.90 \pm 0.12 mb\) and\(\sigma (K^ + \xrightarrow{p}K_D^ + ) = 0\). 90±0.17 mb, respectively. In either case the only notable contributions come from dissociations into 1 and 3 charged particles. Kaon dissociation exhibits a pronounced slope-mass correlation. The search for double diffractive production in reactionsK+p→(K+π−π+)+X+ andK+p→(pπ+π−)+X+ leads in either case to an estimated total double diffractive cross section σ(K+p→K D + pD) of ≅220 μb. The double dissociation differential cross section exhibits a large slope of ≅10GeV−2 in the nearthreshold mass region, rapidly decreasing to ≅4 GeV−2 with increasing excitation mass. At our c.m. energy\((\sqrt s \simeq 8 GeV)\) the ratio σinel dif/σel is 0.85±0.10, the total diffractive cross section σdif≡σel+σinel dif=4.41±0.24 mb and the fraction σdif(K+p)/σtot(K+p) is 25±2%. TheK+ andK− diffractive excitation mass spectra, differential cross sections and total diffractive cross sections are very similar for both single and double dissociations.

New results on nucleon double diffraction at the CERN ISR

Results on exclusive double diffraction dissociation in (N π) and (N ππ) final states are reported for neutron-neutron interactions at √ s= 26.4 GeV and for the proton-neutron interactions at √ s= 37.2 GeV. The data have been obtained at the CERN intersecting storage rings using split field magnet detector with proton-deuteron and deuteron-deuteron colliding beams. Factorization is shown to be verified to a very high degree in both mass- and t-differential cross-sections. The data confirm the previously observed rise in the proton-proton double diffractive cross-section as a function of c.m. energy.