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.     

Transverse spin effects in diffractive hadron leptoproduction

We consider double spin asymmetries for longitudinally polarized leptons and transversely polarized protons in diffractive vector meson and production at high energies within the two-gluon model. The connection of the two-gluon approach with skewed gluon distributions is discussed. The asymmetry predicted for meson production is quite small. The asymmetry for production contains two independent terms which are large and can be used to obtain information on the polarized skewed gluon distributions in the proton. Received: 19 February 2002 / Revised version: 19 March 2002 / Published online: 22 May 2002     

Spin dependence of deep inelastic diffraction

Using a perturbative model for diffractive interactions, we derive an expression for the polarized diffractive structure function in the high energy limit. This structure function is given by the interference of diffractive amplitudes with polarized and unpolarized exchanges. For the polarized exchange we consider both two-gluon and quark-antiquark amplitudes. The polarized diffractive amplitude receives sizable contributions from non-strongly ordered regions in phase space, resulting in a double logarithmic enhancement at small x. The resummation of these double logarithmic terms is outlined. We also discuss the transition from our perturbative expression to the nonperturbative region. A first numerical estimate indicates that the perturbative contribution to the spin asymmetry is substantially larger than the nonperturbative one. Received: 7 July 1999 / Published online: 14 October 1999     

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.     

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     

2-jet production in polarised\vec p\vec pcollisions

Following recent interest in the subject of polarisation phenomena, we discuss the cross-sections and polarisation asymmetry in 2-jet production in polarised proton-polarised proton ( ) scattering. We set up a complete set of parametrisations for the proton spin-dependent parton densities and use them to demonstrate that this cross-section is dominated by gluonic terms. Hence, a measurement of the asymmetry in such processes will provide information on the gluon spin-dependent density. We further show that a factorisation of the hadronic cross-section a la Combridge and Maxwell's work in unpolarised 2-jet production also applies to the spin-dependent case. Hence, the cross-section can be written in terms of a genericpolarised parton density, which can then be measured in the process.     

Double Pomeron Exchange and J/ψ,γ Production Processes in High Energy p＋p(p)Collisions

The double diffractive J/ψ, hard production processes is discussed. Assuming that Pomeron has parton distributions and dominated by gluons with behavior as 1/x when x is small, the energy dependance of the cross section, for above processes is calculated and compared with both the cross section of single diffractive hard scattering and of Drell-Yan processes . It is shown that the is similar with and increases as (lnS)2 at superhigh energies. It is emphasized that this character may provide a new method for detecting physical particles at energy ranges of SSC.     

高能p+p(p)碰撞中双重Pomeron交换和J/ψ、γ产生过程

讨论高能双衍射硬产生过程.假定Pomeron(P)中以胶子分布为主且小x处有的行为后,计算了截面随能量的变化,比较了它们与单衍射(单个P交换)硬过程和非衍射Drell-Yan相应过程的截面随的变化.得出双衍射硬过程与单衍射时相似,在超高能(TeV以上)区截面基本上都是以(lnS)2增加,指出了这在实验中可能具有的意义.     

Quasi-elastic pn scattering in ^6LiD and ^6LiH targets from 1.1 to 2.4 GeV

A polarized proton beam from SATURNE II, the Saclay polarized targets with Li compounds, and an unpolarized target were used to measure spin-dependent observables for protons scattered on bound nucleons. The beam and target polarizations were oriented vertically. The analyzing power and the depolarization were determined at seven energies between 1.1 and 2.4 GeV. The spin correlation parameter was measured at only 1.1 and 1.6 GeV. Measurements with the target at 1.1 GeV provided data for scattering of polarized protons on neutrons in carbon. The quasi-elastic observables are compared with previous elastic scattering measurements and at 1.1 GeV with predictions of phase shift analyses. Received: 19 April 1999 / Published online: 28 September 1999     

A diffractive model including spin for pp elastic scattering at very high energy

In this paper we present a theoretical diffractive model for spin-dependent proton-proton scattering at very high energies using an extended version of the Chou-Yang model. The model describes a wide t range, but in this paper we use it for small t values. We obtain estimates of the ratio of spin-dependent to spin-independent amplitudes, β, consistent with a previous phenomenological analysis. Next we estimate the asymmetry, Σ, expected in a certain polarized inclusive process at high energy. We then compute the size of polarization effects in pp total cross-section measurements, using polarized beam and target at very high energy. Our estimates of the latter two quantities indicate that their measurement would not provide a sensitive test of pomeron factorization.     

Photoproduction of heavy vector mesons at HERA – a test field for diffraction

Exclusive diffractive photoproduction of heavy vector mesons (V=, and ) at HERA is studied in a model employing a dipole Pomeron exchange (P) with an inelastic vertex. The model is fitted to the data on , B, and for and beyond the threshold region. The elastic cross sections for both and photoproduction show a moderate increase within the HERA energy region. The flattening of the slope B(s) (indicating little or no shrinkage) for is not correlated with the slope of the Pomeron trajectory. Estimates for photoproduction at HERA are given. Received: 11 January 1999 / Published online: 8 September 1999     

Gluonic Origin and Glueball Nature of Pomeron

The Pomeron-nucleon coupling vertex is theoretically derived from the fundamental theory of strong interaction QCD. The empirical vertex βγ^μF1 （t） used commonly in diffractive processes with a coupling strength β = 6.0 GeV^-1 is initially obtained from QCD theoretically. Our study not only reproduces the Pomeron-nucleon coupling from QCD but also clearly shows the gluonlc origin and glueball nature of Pomeron, which is a longstanding puzzle. From this investigation, we claim that Pomeron can be regarded as a Reggeized tensor glueball ζ（2230） with quantum numbers of I^GJ^PC = 0＋2＋＋. Since the tensor glueball ζ（2230） lies on the Pomeron trajectory αp（t = Mζ^2） = 2, the longstanding puzzle that no physical particle lies on the Pomeron trajectory, αp（t） = 1.08 ＋ 0.20 GeV^-2 .t, seems to be solved.     

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.     

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.     

Elastic and quasi-elastic pp scattering in ^6LiH and ^6LiD targets between 1.1 and 2.4 GeV

A polarized proton beam extracted from SATURNE II, the Saclay polarized target with Li compounds, and a target were used to measure elastic and quasi-elastic pp spin-dependent observables in the angular region . The beam and/or target polarizations were oriented vertically. Accurate pp data for the analyzing power , spin-correlation parameter , and the polarization transfer were measured at 1.1 GeV. The observables and were determined at six other energies between 1.6 and 2.4 GeV. At 1.6 GeV, was also obtained. The individual contributions from H, Li, and LiD were deduced. The target provided results on free hydrogen and on protons in carbon. The elastic and quasi-elastic observables are compared with existing data and with phase-shift analysis predictions. Received: 19 April 1999 / Published online: 14 October 1999     

Dijet production by double pomeron exchange at the fermilab tevatron

We report the first observation of dijet events with a double Pomeron exchange topology produced in &pmacr;p collisions at sqrt[s] = 1800 GeV. The events are characterized by a leading antiproton, two jets in the central pseudorapidity region, and a large rapidity gap on the outgoing proton side. We present results on jet kinematics and production rates, compare them with corresponding results from single diffractive and inclusive dijet production, and test factorization.     

Survival probability of large rapidity gaps in the QCD and <Emphasis Type="Italic">N</Emphasis>=4 SYM motivated model

In this paper we present a self-consistent theoretical approach for the calculation of the Survival Probability for central dijet production. These calculations are performed in a model of high energy soft interactions based on two ingredients: (i) compatibility with the results of N=4 SYM, which at the moment is the only theory that is able to deal with a large coupling constant; and (ii) the required matching with high energy QCD. Assuming, in accordance with these prerequisites, that the soft Pomeron intercept is rather large and the slope of the Pomeron trajectory is equal to zero, we derive analytical formulae that sum both enhanced and semi-enhanced diagrams for elastic and diffractive amplitudes. Using parameters obtained from a fit to the available experimental data, we calculate the Survival Probability for exclusive central dijet production at energies accessible at the LHC. The results presented here, which include the contribution of semi-enhanced and net diagrams, are considerably larger than our previous estimates.     

Self-consistent Pomeron dynamics without decoupling

More conservative conditions on the independently uniform convergence of multi-Regge asymptotic expansions lead to a consistent Pomeron pole dynamics, without requiring the coupling Λ (0,0,0) of three such poles to vanish. The onset of large mass diffractive processes at high energies in an asymptotically constant renormalization. of the pole residue. This threshold mechanism may be responsible for the rise in σ_total and σ_el at ISR and for building the forward quasi-elastic peak in the leading proton x-distribution.