4 pages, 1 figure, 1 table. Talk at Rencontres de Moriond QCD and High Energy Interactions, La Thuile, Italy, March 19-26, 2016. Misprints corrected in Table~1 and in text (pg 3 par 2 line 7)
Predictions of the elastic scattering, total-inetastic, and total proton-proton cross sections, based on a Regge theory inspired tensor-Pomeron implementation of the RENORM model for hadronic diffraction, are compared to the latest experimental measurements at the LHC. The measured cross sections are in good agreement within the experimental uncertainties of the data and the theoretical uncertainties of the model, reaching down to the ~1% level.
We present a study of associated jpsi + gamma production through double Pomeron exchange at energies reached at the Fermilab Tevatron and CERN LHC based on the Ingelman-Schlein model for hard diffractive scattering and the factorization formalism of nonrelativistic QCD for quarkonia production. We find that this process (p + pbar \to p + pbar + jpsi + gamma + X) can be used to probe the gluon content of the Pomeron and study the natrue of hard diffractive factorization breaking.
A phenomenological description of diffractive dijet hadroproduction via double Pomeron exchange is presented. This description is based on a modified version of the Ingelman-Schlein model which includes the evolution of the Pomeron structure function and corrections regarding rapidity gap suppression effects. The same quark-dominant Pomeron structure function employed in a previous report to describe diffractive dijet and W production via single Pomeron processes is shown here to yield results consistent with the available data for double Pomeron processes as well.
Recent experimental data on diffractive deep inelastic scattering collected by the H1 and ZEUS Collaborations at HERA are analysed in a model with a non-linear trajectory in the pomeron flux. The $t$ dependence of the diffractive structure function $F_2^{D(4)}$ is predicted. The normalization of the pomeron flux and the (weak) $Q^2$ dependence of the pomeron structure function are revised as well.
Diffractive meson production at HERA offers interesting possibilities to investigate diffractive processes and thus to learn something about the properties of the pomeron. The most succesful phenomenological description of the pomeron so far assumes it to couple like a $C = +1$ isoscalar photon to single quarks. This coupling leads, however, to problems for exclusive diffractive reactions. We propose a new phenomenological pomeron vertex, which leads to very good fits to the known data, but avoids the problems of the old vertex.
Transverse single spin asymmetry in polarized diffractive $Q \bar Q$ production is calculated. It is shown that this asymmetry depends strongly on the spin structure of the pomeron coupling, which permits one to study the pomeron couplings properties in future polarized experiments.
We calculate the cross section and the $A_{ll}$ asymmetry of the diffractive vector meson leptoproduction for a simple model of the pomeron coupling with the proton. It is found that the sensitivity of the spin--dependent cross section of the diffractive $J/Ψ$ production to the pomeron coupling structure is rather weak. The conclusion is made that it will be difficult to study the structure of the pomeron coupling with the proton in future polarized diffractive experiments on the $J/Ψ$ production.
The dependence of the fractal behaviors of the pomeron induced system in deep inelastic lepton-nucleon scattering upon the diffractive kinematic variables is found rather robust and not sensitive to the distinct parameterization of the pomeron flux factor and structure function. A feasible experimental test of the phenomenological pomeron-exchanged model based on the fractal measurement in DESY $ep$ collider HERA is proposed.
We test the hypothesis that diffractive scattering in the perturbative and non-perturbative domain is determined by the exchange of a single pomeron with a scale dependent trajectory. Present data on diffractive vector meson production are well compatible with this model and recent results for $J/ψ$ photoproduction at LHC strongly support it. The model is inspired by concepts of gauge/string duality applied to the pomeron.
Central diffractive production of heavy states (massive dijets, Higgs boson) is studied in the exclusive mode using a new Hybrid Pomeron Model (HPM). Built from Hybrid Pomerons defined by the combination of one hard and one soft color exchanges, the model describes well the centrally produced diffractive dijet data at the Tevatron. Predictions for the Higgs boson and dijet exclusive production at the LHC are presented.
This study focuses on hard diffractive events produced in proton-proton collision at LHC exhibiting one intact proton in the final state which can be tagged by forward detectors. We report prospective results on the W boson charge asymmetry measured for such events, which allow to constrain the quark diffractive density functions in the Pomeron.
We review the recent progress in the theory of diffractive DIS, focusing on predictions of strong breaking of the Ingelman-Schlein-Regge factorization and the related breaking of the GLDAP evolution for the diffractive structure function.
Pomeron non factorization for the diffractive scattering is considered and an analysis of experimental data is performed with different cuts in the momentum fraction $ξ$. The results of the analysis are compared with the breaking predicted in the Genovese-Nikolaev-Zakharov model.
By using Monte Carlo simulation of pomeron exchange model, the dependence of the fractal behavior of the pomeron induced system in deep inelastic lepton-nucleon scattering upon the diffractive kinematic variables is found rather robust and not sensitive to the distinct parameterization of the pomeron flux factor and structure function. Based on this characteristic fractal plot, a feasible experimental test of the phenomenological pomeron-exchange model in DESY $ep$ collider HERA is proposed.
We discuss the observed scaling of the small-x diffractive and total deep-inelastic structure functions at HERA. We argue that the parton interpretation of Buchmüller and Hebecker can be understood within QCD as the appearance of the Pomeron in a Super-Critical phase. In diffractive hard scattering, the Pomeron appears as reggeized gluon exchange in a color-compensating background field. The formalism can also be applied to diffractive $W$ production at the Tevatron. If the scaling is a true asymptotic property then it should anticipate the appearance of a further massive sector of QCD and ass…
Misprints and numerical coefficients corrected, a bit of phenomenology and one figure added. The case for the linear evolution of the unitarized structure functions made stronger.
We present a study of diffractive associated jpsi + gamma production at the Fermilab Tevatron and LHC based on the Ingelman-Schlein model for hard diffractive scattering and the factorization formalism of NRQCD for quarkonia production. We find that this process (p + pbar to p + jpsi + gamma + X) can be used to probe the gluon content of the Pomeron and test the assumption of diffractive hard scattering factorization. Using the renormalized Pomeron flux factor D simeq 0.11 (0.052), the single diffractive jpsi + gamma production cross section at 4<P_T< 10 GeV, -1<eta<1 region is found to be of …
We study the contribution of diffractive $Q \bar Q$ production to the $F_2^D$ proton structure function and the longitudinal double-spin asymmetry in polarized deep--inelastic $lp$ scattering. We show the strong dependence of the $F_2^D$ structure function and the $A_{ll}$ asymmetry on the quark--pomeron coupling structure.
Large-distance effects, which lead to the spin-flip part of the hadron -pomeron coupling in QCD -models, are discussed. We study spin asymmetries in exclusive reactions and in diffractive $Q \bar Q$ and vector meson production which are sensitive to the spin-dependent part of the pomeron coupling.
Presented here is a study of the large p_T J/psi production in hard diffractive process by the pomeron exchange at the Fermilab Tevatron. We find that this process (p\bar p \to p+J/psi+X) can be used to probe the gluon content of the pomeron and to measure the gluon fraction of the pomeron. And the diffractive direct J/psi production can also provide another crucial test for the color-octet fragmentation mechanism. Using the renormalised pomeron flux factor D\approx 1/9, the single diffractive J/psi production cross section at large p_T (\geq 8GeV) is found to be of order of 0.01 nb, and the r…
We analyze contributions to the heavy vector meson production with large transverse momentum in proton--proton and diffractive photon--proton scattering driven by an exchange of two Balitsky--Fadin--Kuraev--Lipatov Pomerons in the squared amplitudes. The Pomerons couple to a single parton and form a Pomeron loop closed by the vector meson impact factors. For the photon--proton case the diffractive cut of the Pomeron loop contributes, and for the inclusive hadroproduction one finds the loop with two cut Pomerons. We compute both of these Pomeron loop contributions and study in detail their prop…
We have recently studied the QCD pomeron loop evolution equations in zero transverse dimensions [Shoshi:2005pf]. Using the techniques developed in [Shoshi:2005pf] 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 asymptotic energies and that they are suppressed by powers of alpha_s. Our calculation is expected to expose …
It is shown that the longitudinal double spin asymmetry $A_{ll}$ in polarized diffractive $l p \to l p+Q \bar Q$ reaction depends strongly on the spin structure of quark-pomeron vertex. The SMC spin facilities may be one of the best place to perform such experiment.
The role of the QCD vacuum effects in high energy diffractive quark-quark and quark-antiquark scattering is studied with the Instanton Liquid Model. The special attention is given to the problem of formation of the soft Pomeron. We show that in the leading approximation in instanton density the $C-$odd instanton contribution to the diffractive amplitude is suppressed as $1/s$ compared to the $C-$even one.
Experimental rates of W and dijets diffractively produced at the Tevatron Collider have recently become available. We use parametrizations of the pomeron structure function obtained from HERA data by two different schemes to compare theoretical expectations with the measured rates.
We present microscopic QCD calculation of the cross section of diffractive DIS and of the partonic structure of the pomeron from the dipole approach to the generalized BFKL pomeron. We show that the pomeron can not be treated as a particle with uniquely defined structure function and flux in the proton. We find strong factorization breaking which can approximately be described by the two-component structure function of the pomeron, each component endowed with the different flux of pomerons in the proton. We predict very weak $Q^{2}$ dependence of the diffractive contribution to the proton stru…
We study Pomeron-Odderon interference effects giving rise to charge and single-spin asymmetries in diffractive electroproduction of a $π^+ π^-$ pair. The final state interactions and the role of $f_0$ meson are discussed. The absence of $f_0$ signal in the charge asymmetry observed by HERMES may be due to the smalness of its quark component.
The most important consequence of Pomeron being a pole is the factorization property. However, due to Pomeron intercept being greater than 1, the extrapolated single diffraction dissociation cross section based on a classical triple-Pomeron formula is too large leading to a potential unitarity violation at Tevatron energies. It is our desire here to point out that the "flavoring" of Pomeron plays the dominant role in resolving this apparent "paradox".
Diffractive scattering involves exchange of a Pomeron to make a rapidity gap. It is normally assumed that to get a hard scattering in diffraction, one may treat the Pomeron as an ordinary particle, which has distributions of gluons and quarks. We show that this is not so: When we use perturbative QCD, there is a breakdown of the factorization theorem. The whole Pomeron can initiate the hard scattering, even though it is not point-like. Qualitatively, but not quantitatively, this gives the same effect as a delta function term in the gluon density in a Pomeron.
In this paper we discuss the processes of diffractive production in the framework of the BFKL Pomeron calculus in zero transverse dimension. Considering the diffractive production of a bunch of particles with not very large masses, namely, $\ln\Lb M^2/m^2 \Rb \ll \frac{1}{\bas} \ln\Lb \frac{N^2_c}{\bas^2}\Rb$, we found explicit formulae for calculation of the cross sections for the single and double diffractive production as well as for the value of the survival probability for the diffractive central production. These formulae include the influence of the correlations due to so called Pomeron…
The diffractive 2-jet production reactions in the proton-proton and lepton-proton processes are discussed. It is shown that they may be very suitable for studying the properties of the pomeron couplings with quarks and hadrons in future polarized experiments at HERA, especially for HERA-$\vec N$ project.
We present predictions for the diffractive production of heavy quarks in deep-inelastic scattering and hadron-hadron collisions and for double diffractive dijet production in hadron-hadron collisions. With the assumption of hard scattering factorization, the predictions are made using diffractive parton densities that we have previously fitted to HERA data. Comparisons of our predictions with preliminary data from HERA and the Tevatron indicate that factorization is obeyed in diffractive DIS but fails in hadron-induced processes.
The double diffractive Higgs production at central rapidity is formulated in terms of the fusion of two AdS gravitons/Pomerons first introduced by Brower, Polchinski, Strassler and Tan in elastic scattering. Here we propose a simple self-consistent holographic framework capable of providing phenomenologically compelling estimates of diffractive cross sections at the LHC. As in the traditional weak coupling approach, we anticipate that several phenomenological parameters must be tested and calibrated through factorization for a self-consistent description of other diffractive process such as to…
Theoretical predictions for the behavior of $A_{LL}$ asymmetry determined by the pomeron-hadron vertex are done. Strong dependence of the asymmetry on the mass creating quarks and transfer momenta is shown.
In this paper, the inclusive Pomeron-Pomeron, Reggeon-Reggeon, Pomeron-Reggeon as well as gluon-Pomeron(-Reggeon) and photon-Pomeron(-Reggeon) interactions for the $\rm η_{c}$ at the LHC energies have been examined in proton-proton, proton-nucleus and nucleus-nucleus collision modes. The cross section has been computed based on the NRQCD factorization and Regge theory formalism. The cross exchange of Pomeron-Reggeon contribution is important in $\rm pp$ and $\rm pA$ modes. The Pomeron-Pomeron contribution is significant in $\rm AA$ mode. The Pomeron contribution is considerable for $\rm AA$ an…
We discuss consequences of the models of "tensorial pomeron" and "vectorial pomeron" for exclusive diffractive production of scalar and pseudoscalar mesons in proton-proton collisions. Diffractive production of $f_{0}(980)$, $f_{0}(1370)$, $f_{0}(1500)$, $η$, and $η'(958)$ mesons is discussed. Different pomeron-pomeron-meson tensorial coupling structures are possible in general. In most cases two lowest orbital angular momentum - spin couplings are necessary to describe experimental differential distributions. For $f_{0}(980)$ and $η$ production reggeon-pomeron, pomeron-reggeon, and reggeon-re…
We investigate in detail the effect of a direct pomeron coupling to quarks on the production of jets in $ep$ scattering with almost real photons. Jet production via a direct pomeron coupling is compared with the resolved--pomeron mechanism. We consider both direct and resolved photoproduction. Rapidity and transverse momentum distributions are calculated and compared with preliminary H1 and ZEUS data.
The production of the $W$ and $Z$ bosons in single diffractive processes at the LHC is investigated taking into account the ATLAS, CMS and LHCb acceptances and considering different assumptions for the flavour content of the Pomeron. The total cross sections and pseudorapidity distributions are estimated for $pp$ collisions at $\sqrt{s} = 13$ TeV. Our results indicate that a future experimental analysis of the ratio between the $W$ and $Z$ cross sections can be used to probe the flavour content of the Pomeron.
A phenomenological renormalization scheme for hadronic diffraction is proposed, which achieves unitarization without the need for "screening corrections". Predictions for diffractive photoproduction cross sections at HERA are presented and compared with experimental results. A new interpretation of hard and deep inelastic diffractive data emerges, in which the momentum sum rule is obeyed by the constituents of a pomeron described as a mixture of quark and gluon color singlets in a ratio dictated by asymptopia.
Measurements of the diffractive structure function, $F_2^D$, of the proton at HERA are used to extract the partonic structure of the Pomeron. Regge Factorization is tested and is found to describe well the existing data within the selected kinematic range. The analysis is based on the next to leading order QCD evolution equations. The results obtained from various data sets are compared. An analysis of the uncertainties in determining the parton distributions is provided. The probability of diffraction is calculated using the obtained results.
Large - distance effects in the hadron wave function for the hadron-Pomeron vertex in the QCD -model are discussed. It is shown that they lead to the spin-flip part of the Pomeron coupling which can reach $10 ÷20 %$ with respect to the non-flip part. The obtained structure of the Pomeron coupling modifies spin asymmetries in high--energy diffractive reactions where the Pomeron structure becomes determinative. We study spin asymmetries in exclusive reactions and in the diffractive $Q \bar Q$ and $J/Ψ$ production. We have found that spin effects in these diffractive processes are sensitive to th…
Soft diffractive cross sections in $pp$ (or $\bar pp$), $πp$ and $γp$ collisions are calculated using QCD-motivated pomeron. The $s$-channel unitarization of the amplitude is performed by the eikonal approach, and in the framework of the quark structure of hadrons the colour screening is taken into account. The performed description of the diffractive processes has led to the parameters of the bare pomeron $P$ which occurred to be close to the corresponding parameters of the Lipatov's pomeron. Parameters of the bare pomeron and those of the three-reggeon block $PGG$ ($G$ is a reggeized gluon) …
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.
We analyse the momentum space triple Pomeron vertex in perturbative QCD. In addition to the standard form of this vertex which is used in the context of total cross-sections at high energies and in the QCD reggeon field theory, there exists an alternative form which has to be used in the study of high-mass diffraction. We review and analyse the relation between these two versions. We discuss some implications for the BK-equation. In the second part of our paper we extend this analysis to the Pomeron-Odderon-Odderon vertex.
The interference of Pomeron and Odderon amplitudes gives rise to a charge asymmetry in the diffractive electroproduction of a pi+pi- -pair. We calculate this charge asymmetry in perturbative QCD in the Born approximation and on the leading Q^2-level. The numerical evaluation shows a sizeable asymmetry in an experimentally accessible kinematical region. We find a characteristic m_{pi+pi} -dependence mainly dictated by the relevant Breit-Wigner-amplitudes and the corresponding phase-shifts.
In this Letter we study the double diffractive vector meson production in $e^+e^-$ collisions assuming the dominance of the BFKL pomeron exchange. We consider the non-forward solution of the BFKL equation at high energy and large momentum transfer and estimate the total cross section for the process $e^+e^- \to e^+e^- V_1 V_2$ with antitagged $e^+$ and $e^-$, where $V_1$ and $V_2$ can be any two vector mesons ($V_i = ρ, ω, ϕ, J/Ψ, Υ$). The event rates for the future linear colliders are given.
The analysis of some effects caused by the spin--dependent pomeron couplings is presented. It is shown that the structure of pomeron--proton and quark--pomeron couplings can be tested in future polarized experiments on elastic $pp$ reactions and diffractive $Q \bar Q$ production.
Diffractive deep inelastic events with a large rapidity gap are analyzed by using a Regge model for the pomeron flux and a gluonic content for the pomeron. Contrary to the expectations, the simplest assumption for the pomeron trajectory gives the best agreement with the data on the ratio of diffractive to the total number of events. In this case the main properties of the model are described by an analytic expression.
A model for exclusive diffractive resonance production in proton-proton collisions at high energies is presented. This model is able to predict double differential distributions with respect to the mass and the transverse momentum of the produced resonance in the mass region $\sqrt{M^2}\le$5 GeV. The model is based on convoluting the Pomeron distribution in the proton with the Pomeron-Pomeron-meson total cross section. The Pomeron-Pomeron-meson cross section is saturated by direct-channel contributions from the Pomeron as well as from two different $f$ trajectories, accompanied by the isolated…
It is shown that in a supercritical pomeron model the contribution of the tirple-pomeron diagrams violates the unitarity bound for cross-section even with account of the multiple pomeron exchanges between the initial hadrons. Asymptotic behaviour of the single diffractive dissoci\-ation cross-section is calculated in the approximation where every pomeron in the $3P$-diagram is eikonalized as well as an elastic interaction of initial hadrons is taken into account. In this approximation $σ^{SD}/σ_{tot}\rightarrow 0$ at $s\rightarrow \infty.$
We derive an evolution equation describing the high energy behavior of the cross section for the single diffractive dissociation in deep inelastic scattering on a hadron or a nucleus. The evolution equation resums multiple BFKL pomeron exchanges contributing to the cross section of the events with large rapidity gaps. Analyzing the properties of an approximate solution of the proposed equation we point out that at very high energies there is a possibility that for a fixed center of mass energy the cross section will reach a local maximum at a certain intermediate size of the rapidity gap, or, …
We discuss diffractive production of open charm and bottom mesons at the LHC. The differential cross sections for single- and central-diffractive mechanisms for $c\bar c$ and $b\bar b$ pair production are calculated in the framework of the Ingelman-Schlein model corrected for absorption effects. In this approach one assumes that the pomeron has a well defined partonic structure, and that the hard process takes place in a pomeron-proton or proton-pomeron (single diffraction) or pomeron-pomeron (central diffraction) processes. Here, leading-order gluon-gluon fusion and quark-antiquark anihilatio…
In a consistent QCD approach to diffractive DIS gluons in the pomeron have soft $z_{g}$ distribution and very broad intrinsic $k_{\perp}$ distribution. The latter has not yet been incorporated into diffractive Monte-Carlo generators (RAPGAP,....). I argue that the so-introduced bias in the diffractive jet analysis may be the reason why H1 Collaboration finds the very large and hard gluon content of the pomeron. I discuss possible direct experimental determinations of intrinsic $k_{\perp}$ in the pomeron.
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 $Q^2$ dependence. We give numerical predictions for sin…
We calculate for the first time cross sections for single and central diffractive as well as exclusive diffractive production of dilepton pairs in proton-proton collisions. Several differential distributions are shown. The inclusive diffractive processes are calculated using diffractive parton distributions extracted from the analysis of diffractive structure function and dijet production at HERA. We find that the inclusive single-diffractive Drell-Yan process is by about 2 orders of magnitude smaller than ordinary Drell-Yan process. The central-diffractive processes are smaller by one order o…
The small-$t$ behaviour of the deep inelastic diffractive dissociation cross section in the triple Regge region is investigated, using the BFKL approximation in perturbative QCD. We show that the cross section is finite at $t=0$, but the diffusion in $\ln{k_t^2}$ leads to a large contribution of small momenta at the triple Pomeron vertex. We study the dependence upon the total energy and the invariant mass. At $t=0$, there is a decoupling of the three BFKL singularities which is a consequence of the conservation of the conformal dimension. For large invariant masses, the four gluon state in th…
We present a `global' description of the wide variety of high energy elastic and diffractive data that are presently available, particularly from the LHC experiments. The model is based on only one pomeron pole, but includes multi-pomeron interactions and, significantly, includes the transverse momentum dependence of intermediate partons as a function of their rapidity, which provides the rapidity dependence of the multi-pomeron vertices. We give predictions for diffractive observables at LHC energies.
In this paper, the contribution of hard processes described by the BFKL pomeron exchange, is taken into account by calculating the first enhanced diagram. The survival probability is estimated, using the ratio of the first enhanced diagram and the single pomeron amplitude, taking into account all essential pomeron loop diagrams in the toy model of Mueller. The triple pomeron vertex is calculated explicitly in the momentum representation. This calculation is used for estimating the survival probability, It turns out that the survival probability is small, at $0.4%{}$. Hard pomeron re-scattering…
We present the microscopic QCD evaluation of the secondary reggeon contribution to diffractive DIS. It is shown that the interference between Pomeron and Reggeon enters in the maximal possible way. In the region of large $β\simeq 1$ it is shown, that the structure functions of the Reggeon and Pomeron as well as the Reggeon-Pomeron interference SF have a universal $\sim (1-β)^2$ behaviour.
We review some selected results of the tensor-pomeron and vector-odderon model of soft high-energy proton-proton scattering and central exclusive production of meson and baryon pairs in proton-proton collisions. We discuss the theoretical aspects of this approach and consider the phenomenological implications in a variety of processes at high energies, comparing to existing experimental data. We consider the diffractive dipion and dikaon production including the continuum and the dominant scalar and tensor resonance contributions as well as the photoproduction processes. The theoretical result…
