Spectroscopy at B-factories Using Hard Photon Emission

The process of hard photon emission by initial electrons (positrons) at B-factories is discussed. It is shown that studies of the bottomonium spectroscopy will be feasible for the planned integrated luminosity of the B-factory experiments.Comment: 9 pages, Latex, 1 fugure, Submitted to Int.Jour.Mod.Phys.

Q^2 dependence of diffractive vector meson electroproduction

We give a general formula for the cross section for diffractive vector meson electroproduction, gamma^* p -> Vp. We first calculate diffractive qqbar production, and then use parton-hadron duality by projecting out the J^P = 1^- state in the appropriate mass interval. We compare the Q^2 dependence of the cross section for the diffractive production of rho and J/psi mesons with recent HERA data. We include the characteristic Q^2 dependence associated with the use of the skewed gluon distribution. We give predictions for sigma_L/sigma_T for both rho and J/psi production.Comment: 15 pages, LaTeX, including five PostScript figure

The Wave Function of 2S Radially Excited Vector Mesons from Data for Diffraction Slope

In the color dipole gBFKL dynamics we predict a strikingly different Q^2 and energy dependence of the diffraction slope for the elastic production of ground state V(1S) and radially excited V'(2S) light vector mesons. The color dipole model predictions for the diffraction slope for \rho^0 and \phi^0 production are in a good agreement with the data from the fixed target and collider HERA experiments. We present how a different form of anomalous energy and Q^2 dependence of the diffraction slope for V'(2S) production leads to a different position of the node in radial wave function and discuss a possibility how to determine this position from the fixed target and HERA data.Comment: 20 pages and 6 figures. Title change

The BFKL Pomeron in 2+1 Dimensional QCD

We investigate the high-energy scattering in the spontaneously broken Yang - Mills gauge theory in 2+1 space--time dimensions and present the exact solution of the leading $\ln s$ BFKL equation. The solution is constructed in terms of special functions using the earlier results of two of us (L.N.L. and L.S.). The analytic properties of the $t$-channel partial wave as functions of the angular momentum and momentum transfer have been studied. We find in the angular momentum plane: (i) a Regge pole whose trajectory has an intercept larger than 1 and (ii) a fixed cut with the rightmost singularity located at $j=1$. The massive Yang - Mills theory can be considered as a theoretical model for the (non-perturbative) Pomeron. We study the main structure and property of the solution including the Pomeron trajectory at momentum transfer different from zero. The relation to the results of M. Li and C-I. Tan for the massless case is discussed.Comment: 28 pages LATEX, 3 EPS figures include

Color Transparency versus Quantum Coherence in Electroproduction of Vector Mesons off Nuclei

So far no theoretical tool for the comprehensive description of exclusive electroproduction of vector mesons off nuclei at medium energies has been developed. We suggest a light-cone QCD formalism which is valid at any energy and incorporates formation effects (color transparency), the coherence length and the gluon shadowing. At medium energies color transparency (CT) and the onset of coherence length (CL) effects are not easily separated. Indeed, although nuclear transparency measured by the HERMES experiment rises with Q^2, it agrees with predictions of the vector dominance model (VDM) without any CT effects. Our new results and observations are: (i) the good agreement with the VDM found earlier is accidental and related to the specific correlation between Q^2 and CL for HERMES kinematics; (ii) CT effects are much larger than have been estimated earlier within the two channel approximation. They are even stronger at low than at high energies and can be easily identified by HERMES or at JLab; (iii) gluon shadowing which is important at high energies is calculated and included; (iv) our parameter-free calculations explain well available data for variation of nuclear transparency with virtuality and energy of the photon; (v) predictions for electroproduction of \rho and \phi are provided for future measurements at HERMES and JLab.Comment: Latex 57 pages and 17 figure

Signal and Backgrounds for Leptoquarks at the LHC

We study the potentiality of the CERN Large Hadron Collider (LHC) to unravel the existence of first generation scalar leptoquarks. Working with the most general $SU(2)_L \otimes U(1)_Y$ invariant leptoquark interactions, we analyze in detail the signals and backgrounds that lead to a final state containing a pair $e^+e^-$ and jets. Our results indicate that a machine like the LHC will be able to discover leptoquarks with masses up to 2--3 TeV depending on their couplings.Comment: 37 pages, revtex, uses epsfig.sty (included), 15 figures (included

The spin dependence of high energy proton scattering

Motivated by the need for an absolute polarimeter to determine the beam polarization for the forthcoming RHIC spin program, we study the spin dependence of the proton-proton elastic scattering amplitudes at high energy and small momentum transfer.We examine experimental evidence for the existence of an asymptotic part of the helicity-flip amplitude phi_5 which is not negligible relative to the largely imaginary average non-flip amplitude phi_+. We discuss theoretical estimates of r_5, essentially the ratio of phi_5 to phi_+, based upon extrapolation of low and medium energy Regge phenomenological results to high energies, models based on a hybrid of perturbative QCD and non-relativistic quark models, and models based on eikonalization techniques. We also apply the model-independent methods of analyticity and unitarity.The preponderence of evidence at available energy indicates that r_5 is small, probably less than 10%. The best available experimental limit comes from Fermilab E704:those data indicate that |r_5|<15%. These bounds are important because rigorous methods allow much larger values. In contradiction to a widely-held prejudice that r_5 decreases with energy, general principles allow it to grow as fast as ln(s) asymptotically, and some models show an even faster growth in the RHIC range. One needs a more precise measurement of r_5 or to bound it to be smaller than 5% in order to use the classical Coulomb-nuclear interference technique for RHIC polarimetry. As part of this study, we demonstrate the surprising result that proton-proton elastic scattering is self-analysing, in the sense that all the helicity amplitudes can, in principle, be determined experimentally at small momentum transfer without a knowledge of the magnitude of the beam and target polarization

Signal and Backgrounds for Leptoquarks at the LHC II: Vector Leptoquarks

We perform a detailed analyses of the CERN Large Hadron Collider (LHC) capability to discover first generation vector leptoquarks through their pair production. We study the leptoquark signals and backgrounds that give rise to final states containing a pair e+e- and jets. Our results show that the LHC will be able to discover vector leptoquarks with masses up to 1.3-2.1 TeV depending on their couplings to fermions and gluons.Comment: 18 pages, 3 figures, REVTe

Quarkonium momentum distributions in photoproduction and B decay

According to our present understanding many $J/\psi$ production processes proceed through a coloured $c\bar{c}$ state followed by the emission of soft particles in the quarkonium rest frame. The kinematic effect of soft particle emission is usually a higher-order effect in the non-relativistic expansion, but becomes important near the kinematic endpoint of quarkonium energy (momentum) distributions. In an intermediate region a systematic resummation of the non-relativistic expansion leads to the introduction of so-called `shape functions'. In this paper we provide an implementation of the kinematic effect of soft gluon emission which is consistent with the non-relativistic shape function formalism in the region where it is applicable and which models the extreme endpoint region. We then apply the model to photoproduction of $J/\psi$ and $J/\psi$ production in $B$ meson decay. A satisfactory description of $B$ decay data is obtained. For inelastic charmonium photoproduction we conclude that a sensible comparison of theory with data requires a transverse momentum cut larger than the currently used 1 GeV.Comment: latex, 45 pages; (v2) some typos corrected, version to appear in PR