Rapidity distribution of particle multiplicity in DIS at small x

Analytical study of the rapidity distribution of the final state particles in deep inelastic scattering at small x is presented. We separate and analyse three sources of particle production: fragmentation of the quark-antiquark pair, accompanying coherent soft gluon radiation due to octet color exchange in the t-channel, and fragmentation of gluons that form parton distribution functions. Connection to Catani-Ciafaloni-Fiorani-Marchesini (CCFM) equations and the role of gluon reggezation are also discussed.Comment: 14 pages, 6 Figures. Abstract extended, minor misprints corrected, derivations improved and explanations are streamlined. Published in Physics Letters, B

Coulomb scattering of quantum dipoles in QED

We calculate the total scattering cross-section of a dynamical quantum electrically neutral dipole in QED of the infinitely heavy charge and of the infinitely heavy dipole in the leading order in electromagnetic coupling constant.Comment: 7 pages, no figure

The four jet production at LHC and Tevatron in QCD

We demonstrate that in the back-to-back kinematics the production of four jets in the collision of two partons is suppressed in the leading log approximation of pQCD, compared to the hard processes involving the collision of four partons. We derive the basic equation for four-jet production in QCD in terms of the convolution of generalized two-parton distributions of colliding hadrons in the momentum space representation. Our derivation leads to geometrical approach in the impact parameter space close to that suggested within the parton model and used before to describe the four-jet production. We develop the independent parton approximation to the light-cone wave function of the proton. Comparison with the CDF and D0 data shows that the independent parton approximation to the light-cone wave function of the proton is insufficient to explain the data. We argue that the data indicate the presence of significant multiparton correlations in the light-cone wave functions of colliding protons.Comment: 5 pages, 2 figures, final version published in Phys.Rev.D, rapid communication

Perturbative QCD correlations in multi-parton collisions

We examine the role played in double parton interactions (DPI) by the parton--parton correlations originating from perturbative QCD parton splittings. Also presented are the results of the numerical analysis of the integrated DPI cross sections at Tevatron and LHC energies. To obtain the numerical results the knowledge of the single-parton GPDs gained by the HERA experiments was used to construct the non-perturbative input for generalized double parton distributions. The perturbative two-parton correlations induced by three-parton interactions contribute significantly to resolution of the longstanding puzzle of an excess of multi-jet production events in the back-to-back kinematics observed at the Tevatron.Comment: 16 pages, 13 figure

Origins of parton correlations in nucleon and multi-parton collisions

We demonstrate that perturbative QCD leads to positive 3D parton--parton correlations inside nucleon explaining a factor two enhancement of the cross section of multi-parton interactions observed at Tevatron at $x_i\ge 0.01$ as compared to the predictions of the independent parton approximation. We also find that though perturbative correlations decrease with $x$ decreasing, the nonperturbative mechanism kicks in and should generate correlation which, at $x$ below $10^{-3}$, is comparable in magnitude with the perturbative one for $x\sim 0.01$.Comment: 4 pages, 5 figure

Testing the Hypothesis of Modified Dynamics with Low Surface Brightness Galaxies and Other Evidence

The rotation curves of low surface brightness galaxies provide a unique data set with which to test alternative theories of gravitation over a large dynamic range in size, mass, surface density, and acceleration. Many clearly fail, including any in which the mass discrepancy appears at a particular length-scale. One hypothesis, MOND [Milgrom 1983, ApJ, 270, 371], is consistent with the data. Indeed, it accurately predicts the observed behavior. We find no evidence on any scale which clearly contradicts MOND, and a good deal which supports it.Comment: Accepted for publication in the Astrophysical Journal. 35 pages AAStex + 9 figures. This result surprised the bejeepers out of us, to

Increase with energy of parton transverse momenta in the fragmentation region in DIS and related phenomena

The dipole and the DGLAP approximations are combined with the $k_t$ factorization theorem to demonstrate the fundamental property of pQCD: smaller is the size of the colorless quark-gluon configurations in the fragmentation region, more rapid is the increase of its interaction with the target as a function of energy. First, we show that the transverse momenta of the quark(antiquark) within the $q\bar{q}$ pair, produced in the fragmentation region by the strongly virtual photon, increase with the decrease of x for fixed $Q^2$. As practical consequence of these effects we show that the cross sections of DIS and DVCS. We predict that the ratio of DVCS to DIS amplitudes should very slowly approach one from above at very large collision energies. Second, we study a closely related phenomenon of the increase of the transverse momenta with the energy of the characteristic transverse momenta of the gluon/quark configurations responsible for the transition to the black disk regime. We discuss the impact of this phenomenona on the slowing of the dependence on the initial energy of the coherence length. We demonstrate that a rapid projectile has the biconcave shape, which is different from the expectations of the preQCD parton model where a fast hadron has a pancake shape. We show that the increase of the transverse momenta leads to a new expression for the total cross section of a DIS scattering at very large energies, relevant to LHeC and LHC. We discuss the impact of the discovered phenomena on the hard processes in pp collisions, and on the dominance ofdifferent phases of chiral and conformal symmetries in the central and peripheral pp, pA, and AA collisions.Comment: 37 pages, 6 figures, uses file pdfsync.sty some typos and misspellings are eliminate

The casuality and/or energy-momentum conservation constraints on QCD amplitudes in small x regime

The causality and/or the energy-momentum constraints on the amplitudes of high energy processes are generalized to QCD. The constraints imply that the energetic parton may experience at most one inelastic collision only and that the number of the constituents in the light cone wave function of the projectile is increasing with the collision energy and the atomic number.Comment: 24 pages,8 figures. The paper is streamlined, some references are changed and misprints are eliminate

Direct CP violation in b -> d J/\psi decays

We investigate the possibility of observing direct CP violation in self-tagging B-meson decays of the type b -> d J/\psi. The CP asymmetry can be generated due to strong or electromagnetic scattering in the final state, or due to long distance effects. The first two contributions give asymmetries of a few 10^(-3), in the standard model. The long distance effects are hard to estimate, but it cannot be excluded that they yield asymmetries of about 1%.Comment: 10 pages, Fermilab-pub-93/307-