Soft diffraction and the elastic slope at Tevatron and LHC energies: a multi-Pomeron approach

We present a formalism for high energy soft processes, mediated by Pomerons, which embodies pion-loop insertions in the Pomeron trajectory, rescattering effects via a two-channel eikonal and high-mass diffractive dissociation. It describes all the main features of the data throughout the ISR to Tevatron energy interval. We give predictions for soft diffractive phenomena at the LHC energy, and we calculate the different survival probabilities of rapidity gaps which occur in various diffractive processes. Received: 1 August 2000 / Published online: 27 October 2000     

Diffractive Scattering Factorization from J/ψ and γ Associated Production in HERA ep Collisions

Using three sets of Pomeron structure functions, the cross sections of J/ψ and γ associated productionvia resolved photon and proton diffractive scatting in ep collision are investigated. It is found that the cross sectionscalculated with various gluon distribution functions of Pomeron are different. The discrepancy is about 1.8 times fordifferential cross sections and 1.7 times for total cross sections. The experimental studies of the process could give valuableinsight in the diffractive production mechanism and test the color-octet mechanism for heavy quarkonium production ina new environment.     

Spin effects in diffractive J/\Psi leptoproduction and the structure of Pomeron coupling

We calculate the cross section and asymmetry of the diffractive J/ leptoproduction for a simple model of a Pomeron coupling with a proton, which contains the term and a spin-dependent part. It is shown that the asymmetry caused by the Pomeron coupling does not vanish for nonzero . The sensitivity of the polarized diffractive J/ production to the spin-dependent part of the Pomeron coupling is found to be rather weak. As a result, it is difficult to study the structure of the Pomeron coupling with the proton in future polarized diffractive experiments on the J/ production. Received: 27 April 1999 / Revised version: 29 June 1999 / Published online: 14 October 1999     

Physics with tagged forward protons at the LHC

We emphasize the importance of tagging the outgoing forward protons to sharpen the predictions for New Physics at the LHC (such as the diffractive production of a light Higgs boson). The rescattering effects lead to a rich distinctive structure of the cross section as a function of the transverse momenta of the protons. We show that a study of the correlations between the proton transverse momenta for double-diffractive production of central dijets will provide a detailed check of the whole diffractive formalism. Adopting a perturbative two-gluon structure of the Pomeron, we emphasize that quarkonium production, via Pomeron-Pomeron fusion, is strongly suppressed. This offers a favourable production mechanism for non- states, such as glueballs. Received: 15 March 2002 / Published online: 21 June 2002     

Regge field theory in zero transverse dimensions: loops versus “net” diagrams

Toy models of interacting Pomerons with triple and quaternary Pomeron vertices in zero transverse dimension are investigated. Numerical solutions for eigenvalues and eigenfunctions of the corresponding Hamiltonians are obtained, providing the quantum solution for the scattering amplitude in both models. The equations of motion of the theories are also considered and the classical solutions of the equations are found. Full two-point Green functions (“effective” Pomeron propagator) and amplitude of diffractive dissociation process are calculated in the framework of RFT-0 approach. The importance of the loops contribution in the amplitude at different values of the model parameters is discussed as well as the difference between the models with and without quaternary Pomeron vertex.     

Double Diffractive Process Factorization from ηc and γ Associated Production at Tevatron and LHC

We present a study of associated ηc and γ double diffractive production in pp^- collision based on Ingelman-Schlein model, and the framework of non-relativistic QOD factorization formalism for quarkonia production. The prediction of ηc and γ is more reliable than J/ψ production, because the associated ηc and γ production is a pure color-octet process, and the dominant contribution comes from color octet ^1S0^(8) subprocess, which is related to the color octet matrix element of ^1S0(8) of J/ψ by the heavy quark spin symmetry and the large PT J/ψ production data. We find that the ratio of diffractive to inclusive cross sections is independent of the values of color octet matrix elements, but is sensitive to the gluon factor of the Pomeron and renormalized Pomeron flux factors. So experimental measurement of this ratio can give us more information of the nature of Pomeron and test the assumption of hard diffractive factorization in hadron-hadron collisions.     

Diffractive photoproduction of charm at the HERA ep collider

For various kinematical domains, the cross section for the diffractive photoproduction of D* mesons at the HERA ep collider is calculated within a model based on perturbation theory. The results obtained by using different models of the Pomeron are compared.     

Regge Models of Proton Diffractive Dissociation Based on Factorisation and Structure Functions

Recent results by the authors on proton diffractive dissociation (single, double and central) in the low-mass resonance region with emphasis on the LHC kinematics are reviewed and updated. Based on the previous ideas that the contribution of the inelastic proton–Pomeron vertex can be described by the proton structure function, the contribution of the inelastic Pomeron–Pomeron vertex appearing in central diffraction is now described by a Pomeron structure function.     

Reggeon field theory: Formulation and use

We formulate and discuss Reggeon field theory, which enables one to systematically analyze the exchange of Regge poles and associated branch points in high energy hardron scattering. The field theory is first motivated by a consideration of hybrid Feynman graphs, and then a more general derivation from crossed-channel multiparticle unitarity relations is given. Rules for Reggeon interaction and propagation are formulated. We treat in some detail the problem of the Pomeron or vacuum pole which has α(0) = 1 and is responsible for diffractive processes. In particular the renormalization group analysis of Reggeon field theory is presented and the structure of Pomeron partial wave amplitudes is elucidated. Also the question of Pomeron or absorptive corrections to secondary trajectories (both fermion and boson) is considered. We make some comments on important problems yet remaining in Reggeon field theory; in particular, we stress the study of its s-channel content.     

The space-time picture of the Wee partons and the AGK cutting rules in perturbative QCD

We discuss the space-time picture of scattering amplitudes with single and double ladder exchange in perturbative QCD. Particular emphasis is given to the Abramovsky Gribov Kanchelli (AGK) rules which describe the relative contributions of the diffractive dissociation and processes with other multiplicities to the elastic scattering amplitude. Inside the Pomeron Pomeron interaction vertices we find a new matrix which describes the transition from one s-cut to another and which goes beyond the original AGK rules.     

Hard diffractive quarkonium hadroproduction at high energies

We present a study of heavy quarkonium production in hard diffractive processes by pomeron exchange for Tevatron and LHC energies. The numerical results are computed using a recent experimental determination of the diffractive parton density functions in the pomeron and these are corrected by unitarity corrections through the gap survival probability factor. We give predictions for single as well as central diffractive ratios. These processes are sensitive to the gluon content of the pomeron at small Bjorken variable x and may be particularly useful in studying small-xphysics. They may also be a good place to test the different available mechanisms for quarkonium production at hadron colliders. PACS 13.60.Hb; 12.38.Bx; 12.40.Nn; 13.85.Ni; 14.40.Gx     

Pomeron structure in processes of diffractive open-charm production

On the basis of the Capella-Kaidalov-Merino-Tran Thanh Van (CKMT) model, the parametrization of the gluon density in the Pomeron is determined from data of the ZEUS experiment devoted to studying diffractive D*-meson production. Experimental data on the open-charm contribution to the diffractive structure function are successfully reproduced within this conceptual framework.     

Gluon shadowing and unitarity effects

New data from HERA experiment on deep inelastic scattering have been used to parametrize nucleon and Pomeron structure functions. Within the Gribov theory, the parameterizations were employed to calculate gluon shadowing for various heavy ions. The latter was compared with predictions from other models. Calculations of multiplicity reduction due to gluon shadowing for d+Au collisions at forward rapidities at √s _NN =200 GeV are in good agreement with BRAHMS data on the nuclear modification factor.     

Reggeon, Pomeron and Glueball, Odderon-Hadron-Hadron Interaction at High Energies - From Regge Theory to Quantum Chromodynamics

Based on analysis of scattering matrix S, and its properties such as analyticity, unitarity, Lorentz invariance, and crossing symmetry relation, the Regge theory was proposed to describe hadron-hadron scattering at high energies before the advent of QCD, and correspondingly a Reggeon concept was born as a mediator of strongly interaction. This theory serves as a successful approach and has explained a great number of experimental data successfully, which proves that the Regge theory can be regarded as a basic theory of hadron interaction at high energies and its validity in many applications. However, as new experimental data come out, we have some difficulties in explaining the data. The new experimental total cross section violates the predictions of Regge theory, which shows that Regge formalism is limited in its applications to high energy data. To understand new experimental measurements, a new exchange theory was consequently born and its mediator is called Pomeron, which has vacuum quantum numbers. The new theory named as Pomeron exchange theory which reproduces the new experimental data of diffractive processes successfully. There are two exchange mediators： Reggeon and Pomeron. Reggeon exchange theory can only produce data at the relatively lower energy region, while Pomeron exchange theory fits the data only at higher-energy region, separately. In order to explain the data in the whole energy region, we propose a Reggeon-Pomeron model to describe high-energy hadron- hadron scattering and other diffractive processes. Although the Reggeon-Pomeron model is successful in describing high-energy hadron-hadron interaction in the whole energy region, it is a phenomenological model. After the advent of QCD, people try to reveal the mystery of the phenomenological theory from QCD since hadron-hadron processes is a strong interaction, which is believed to be described by QCD. According to this point of view, we study the QCD nature of Reggeon and Pomeron. We claim that the Reggeon exchange is an exchange of mult     

The triple regge limit of diffractive dissociation in deep inelastic scattering

We derive, within perturbative QCD, a formula for the inclusive cross section of the diffractive dissociation of the deep inelastic photon γ^*+q→X+q in the triple Regge limits?M ²?Q ²?Λ ². We use the leading ln(s/M ², ln(M ²/Q ²) approximation and derive an, expression for the triple Pomeron vertex. The Pomeron above this vertex is found to be of higher order than the BFKL Pomeron. The resulting formula for the cross section is infrared finite. We show that the Abramovsky-Gribov-Kanchelli cutting rules are satisfied, and we discuss implications for the Pomeron structure function.     

Rapidity gap survival in enhanced Pomeron scheme

We apply the phenomenological Reggeon field theory framework to investigate rapidity gap survival (RGS) probability for diffractive dijet production in proton–proton collisions. In particular, we study in some detail rapidity gap suppression due to elastic rescatterings of intermediate partons in the underlying parton cascades, described by enhanced (Pomeron–Pomeron interaction) diagrams. We demonstrate that such contributions play a subdominant role, compared to the usual, so-called “eikonal”, rapidity gap suppression due to elastic rescatterings of constituent partons of the colliding protons. On the other hand, the overall RGS factor proves to be sensitive to color fluctuations in the proton. Hence, experimental data on diffractive dijet production can be used to constrain the respective model approaches.     

Diffractive dijet production at sqrt[s] = 630 and 1800 GeV at the Fermilab Tevatron

We report a measurement of the diffractive structure function F(D)(jj) of the antiproton obtained from a study of dijet events produced in association with a leading antiproton in pp collisions at sqrt[s] = 630 GeV at the Fermilab Tevatron. The ratio of F(D)(jj) at sqrt[s] = 630 GeV to F(D)(jj) obtained from a similar measurement at sqrt[s] = 1800 GeV is compared with expectations from QCD factorization and other theoretical predictions. We also report a measurement of the xi ( x-Pomeron) and beta ( x of parton in Pomeron) dependence of F(D)(jj) at sqrt[s] = 1800 GeV. In the region 0.035相似文献   

Multiple-Pomeron splitting in QCD—A novel antishadowing effect in coherent dijet production on nuclei

We discuss the salient features of the Pomeron splitting mechanism for coherent diffraction of pions into hard dijets on nuclei. Our findings include antishadowing multiple-Pomeron splitting expansion for diffractive amplitudes, exact cancellation of nuclear attenuation, and broadening/antishadowing effects to leading twist and parameter-free perturbative calculation of nuclear-rescattering-driven higher twist correction. We comment on the pQCD interpretation of the E791 results on diffractive dijets.     

Can a pomeron be really “supersoft”?

The low energy J/gf photoproduction cross-section has been studied on the basis of the Pomeron model. To incorporate the discrepancy between experimental data and predictions by conventional models, i.e. the sum of the soft Pomeron with intercept 1.08 and the hard Pomeron with intercept 1.418, a Regge trajectory associated with a scalar meson (f,a) exchange which we call “supersoft” Pomeron, is introduced additionally. To distinguish between the conventional model and this new additional Pomeron, observations related to other polarization observables in upcoming polarized experiments are discussed.