Triple pomeron vertex in the limit N_c\rightarrow\infty

In the hard pomeron theory with the number of colours the diffractive amplitude obtained in [3] is compared with the results found for in [1] and in the dipole approach in [5]. It is shown that the double pomeron exchange contribution can be substituted by an equivalent triple pomeron interaction term. After such a substitution the triple pomeron vertices in [1,3,5] essentially coincide. It is demonstrated that, in any form, the triple pomeron vertex is conformal invariant. It is also shown that higher order densities in the dipole approach do not involve 1 to k pomeron verteces with but are rather given by a set of pomeron fan diagrams with only a triple pomeron coupling. Received: 11 December 1997 / Revised version: 6 February 1998 / Published online: 7 August 1998     

The triple pomeron interaction in the perturbative QCD

The triple pomeron interaction is studied in the perturbative approach of BFKL-Bartels. At finite momentum transfers √?t the contribution factorizes in the standard manner with a triple-pomeron vertex proportional to 1/√?t, Att=0 the contribution is finite, although it grows faster with energy than for finitet and does not factorize.     

Conformally invariant pomeron interaction in perturbative QCD with large Nc

An effective non-local quantum field theory is constructed, which describes the interaction of pomerons in high-colored QCD. The theory includes both splitting and merging triple pomeron vertexes and diagrams with pomeronic loops. The Schwinger–Dyson equations for the ‘physical’ pomeron are written. Conformal invariance allows one to reduce the theory to the old-fashioned Gribov pomeron theory with an infinite number of pomerons, one of which is supercritical.     

BFKL pomeron propagator in the external field of the nucleus

It is shown by numerical calculations that the convoluted QCD pomeron propagator in the external field created by a solution of the Balitsky-Kovchegov equation in the nuclear matter vanishes at high rapidities. This may open a possibility to apply the perturbative approach for the calculation of pomeron loops.     

Diffractive \eta_c photo-and electroproduction with the perturbative QCD Odderon

Using a set of new odderon states, we calculate their contribution to the diffractive photo- and electroproduction process. Compared to previous simple 3-gluon exchange calculations we find an enhancement of about one order of magnitude in the cross section. The t-dependence of the cross section exhibits a dip structure in the small t region. Received: 18 March 2001 / Published online: 11 May 2001     

Double scattering on the nucleus in the perturbative QCD

In the hard pomeron model consequences are studied which follow from the recently obtained form of the diffractive amplitude for the double scattering on the nucleus and the related EMC effect at small x. It is shown that at large Q²Q^2 to the double scattering contribution to the latter falls as Q^-0.6338Q^{-0.6338} and in all probability dominates the total effect.     

On the inclusive gluon jet production from the triple pomeron vertex in the perturbative QCD

Single and double inclusive cross-sections for gluon jet production from within the triple pomeron vertex are studied in the reggeized gluon technique in the QCD with N_c→∞. It is shown that to satisfy the AGK rules the vertex has to be fully symmetric in all four reggeized gluons which form the two final pomerons. The single inclusive cross-sections are found for different cuttings of the triple pomeron vertex. They sum to the expression obtained by Kovchegov and Tuchin in the color dipole picture. The found double inclusive cross-sections satisfy the AGK rules.     

On inclusive gluon jet production off the nucleus in perturbative QCD

In the perturbative QCD approach single and double inclusive cross-sections for gluon production off the nucleus are studied by the relevant reggeized gluon diagrams. Various terms corresponding to emission of gluons from the triple pomeron vertex are found. Among them the term derived by Kovchegov and Tuchin emerges as a result of the transition from the diffractive to effective high-energy vertex. However it does not exhaust all the vertex contributions to the inclusive cross-section. In the double inclusive cross-section a contribution violating the naive AGK rules is found in which one gluon is emitted from the vertex and the other from one of the two pomerons below the vertex. But then this contribution is subdominant at high energies and taking it into account seems to be questionable.Received: 6 March 2005, Revised: 5 May 2005, Published online: 8 June 2005     

The QCD pomeron in ultraperipheral heavy ion collisions: V. Double vector meson production in the BFKL approach

In this work the double vector meson production in ultraperipheral heavy ion collisions is investigated within the BFKL approach. The integrated cross sections and event rates for the processes ( ) are computed and theoretical estimates for scattering on both light and heavy nuclei are given for energies of RHIC and LHC.     

The phase and pole structure of the N*(1535) in \piN \rightarrow \piN and \gammaN \rightarrow \piN

The nature of some baryonic resonances is still an unresolved issue. The case of the N ^*(1535) is particularly interesting in this respect due to the nearby $ \eta$ N threshold and interference with the N ^*(1650) . The N ^*(1535) has been described as a threshold effect, as a genuine 3-quark resonance, or as dynamically generated from the interaction of the octet of baryons with the octet of mesons. In the scheme of dynamical generation, predictions for the interaction of the N ^*(1535) with the photon can be made. In this study, we simultaneously analyze the role of the N ^*(1535) in the $ \pi$ N $ \rightarrow$ $ \pi$ N and $ \gamma$ N $ \rightarrow$ $ \pi$ N reactions and compare to the respective amplitudes from partial-wave analyses. This test is very sensitive to the meson-baryon components of the N ^*(1535) .     

Single and double inclusive cross sections for nucleus–nucleus collisions in the perturbative QCD

Single and double inclusive cross sections in nucleus–nucleus collisions are derived in perturbative QCD with interacting BFKL pomerons in the quasi-classical approximation.     

The process $\gamma(^*) + p \to \eta_c + X$: a test for the perturbative QCD odderon

The rates of inclusive photo- and electroproduction of the meson: are calculated in the triple Regge region, integrated over the diffractive mass X. For the Regge exchanges we use the hard pomeron and odderon, both being calculated in the framework of perturbative QCD. The integrated cross section depends upon the coupling of the BFKL pomeron to two C = -1 odderons, and it is found to be of the order of 60 pb for photoproduction and 1.5 pb at Q² = 25 GeV².Received: 16 April 2003, Published online: 25 February 2004     

Final-state rescattering and SU(3) symmetry breaking in B\rightarrow DK and B\rightarrow DK^* decays

The first observation of the and transitions by the Belle Collaboration allows us to do a complete isospin analysis of the decay modes. We find that their respective isospin phase shifts are very likely to lie in the ranges (or around ) and (or around ), although the possibility cannot be ruled out at present. Thus significant final-state rescattering effects possibly exist in such exclusive processes. We determine the spectator and color-suppressed spectator quark-diagram amplitudes of the and decays, and compare them with the corresponding quark-diagram amplitudes of the and decays. The effects of SU(3) flavor symmetry breaking are in most cases understandable in the factorization approximation, which works for the individual isospin amplitudes. Very instructive predictions are also obtained for the branching fractions of rare , and transitions. Received: 26 January 2003 / Revised version: 31 January 2003 / Published online: 7 March 2003 RID="a" ID="a" e-mail: xingzz@mail.ihep.ac.cn     

Four-loop moments of the heavy quark vacuum polarization function in perturbative QCD

New results at four-loop order in perturbative QCD for the first two Taylor coefficients of the heavy quark vacuum polarization function are presented. They can be used to perform a precise determination of the charm- and bottom-quark mass. Implications for the value of the quark masses are briefly discussed. PACS 12.38.Bx, 12.38.-t, 11.55.Fv, 14.65.Dw, 14.65.Fy     

QCD sum rules analysis of the rare B_{c}\rightarrow X\nu\bar{\nu} decays

Taking into account the gluon correction contributions to the correlation function, the form factors relevant to the rare decays are calculated in the framework of the three-point QCD sum rules, where X stands for axial vector particle, AV(D _s1), and vector particles, V(D ^*,D _s ^*). The total decay width as well as the branching ratio of these decays are evaluated using the q ² dependent expressions of the form factors. A comparison of our results with the predictions of the relativistic constituent quark model is presented.     

Pomeron structure function and diffraction dissociation of virtual photons in perturbative QCD

We study scaling properties of the diffraction dissociation of virtual photons in a deep inelastic scattering. We concentrate on the total diffraction dissociation rate, diffraction excitation mass spectrum and the pomeron structure function to the lowest order in perturbative QCD. We calculate the valence structure function and the strangeness and charm content of the pomeron and estimate the ocean structure function using the pomeron factorization property. We find that quarks carry ≈ 10% of pomeron's momentum. Differential cross section of the (virtual) photon-pomeron scattering is found to exhibit features typical of the hadronic two-body reactions, supporting a treatment of the Pomeron as a particle, whereas the flavor dependence of structure functions does not support the particle treatment of the pomeron. Diffraction dissociation of photons is predicted to make ≈ 15% of the total deep inelastic scattering rate at smallx and largeQ ². Detailed predictions for the mass spectrum and angular distribution of jets produced on the valence component of the pomeron are presented.     

Resolution of the renormalisation-scheme ambiguity in perturbative QCD

Next-to-leading-order QCD predictions depend on the arbitrary choice of renormalisation scheme. I resolve this ambiguity and show how to find the unique, optimum prediction, given the result in some arbitrary, initial scheme.