BFKL pomeron in the external field of the nucleus in (2+1)-dimensional QCD

The behaviour of the pomeron propagator in the external nuclear field is studied in the (2+1)-dimensional QCD. It is shown that in the physically interesting case when the field does not vanish at large rapidities the propagator in the field vanishes much faster than in the vacuum, in agreement with the results found in the local Regge-Gribov model. However if the nuclear field vanishes at high rapidities the field does not change the behaviour of the pomeron propagator.Comment: 14 pages, 10 figure

On the inclusive gluon jet production off the nucleus in the perturbative QCD

In the perturbative QCD approach single and double inclusive cross-sections for gluon production off the nucleus are studied from 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 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 naive AGK rules is found, in which one gluon is emitted from the vertex and the other from one of the Pomerons below the vertex. But then this contribution is subdominant at high energies and taking it into account seems to be questionable.Comment: 22 pages in LaTex, inclusing 7 figure

Conformal invariant pomeron interaction in the perurbative QCD with large N_c

An effective non-local quantum field theory is constructed, which describes interaction of pomerons in the high-coloured 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 to reduce the theory to the old-fashioned Gribov pomeron theory with an infinite number of pomerons, one of which is supercritical.Comment: 20 pages in LaTe

Centrality dependence of the multiplicity and transverse momentum distributions at RHIC and LHC and the percolation of strings

The dependence of the multiplicity and the transverse momentum distribution on the number of collisions are studied for central and peripheral Au-Au collisions at SPS, RHIC and LHC energies in the framework of percolation of strings. A scaling law relating the multiplicity to the mean transverse momentum is obtained. Our results are in overall agreement with the SPS and RHIC data, obtaining a suppression on $p_T$ distribution even for $p_T$ larger than 1 GeV/c.Comment: Contribution to QM2002, espcrc1.st

Loops in the gluon emission amplitude: reggeization from the Glauber scattering

It is shown that in the Glauber scattering of a fast quark in the external field loop corrections to the gluon emission amplitude due to virtual softer gluon after renormalization coincide with a correction due to reggeization of the exchanged gluon in the BFKL picture.Comment: 26 pages, 10 figure

An SU(5) Heterotic Standard Model

We introduce a new heterotic Standard Model which has precisely the spectrum of the Minimal Supersymmetric Standard Model (MSSM), with no exotic matter. The observable sector has gauge group SU(3) x SU(2) x U(1). Our model is obtained from a compactification of heterotic strings on a Calabi-Yau threefold with Z_2 fundamental group, coupled with an invariant SU(5) bundle. Depending on the region of moduli space in which the model lies, we obtain a spectrum consisting of the three generations of the Standard Model, augmented by 0, 1 or 2 Higgs doublet conjugate pairs. In particular, we get the first compactification involving a heterotic string vacuum (i.e. a {\it stable} bundle) yielding precisely the MSSM with a single pair of Higgs.Comment: 15 page

On the initial condition for evolution of the perturbative QCD Pomeron in the nucleus

It is shown that subdominant terms found in the reggeized gluon diagram technique, to be added to Pomeron fan diagrams with the 3P interaction, can be exactly taken into account by taking the initial condition for evolution in the Glauber form. This demonstrates complete equivalence of the dipole picture and the reggeized gluon approach not only on the leading level but also on the subleading level.Comment: 5 pages in LaTe

Odderon with a running coupling constant

The running coupling is introduced into the equation for the odderon via the bootstrap relation. It is shown that the previously found odderon state with a maximal intercept, which is constructed from antisymmetric pomeron wave function, continues to exist in the running coupling case. Its intercept is found to remain equal to unity independent of the behaviour assumed for the running coupling at low momenta.Comment: 9 pages, LaTe

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.Comment: 17 pages, 15 figure

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. 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 into the expression obtained by Yu.Kovchegov and K.Tuchin in the colour dipole picture. The found double inclusive cross-sections satisfy the AGK rules.Comment: 17 pages in LaTex, 6 figures, revised version with partially changed rsult