Production of Z^0 bosons with rapidity gaps: exclusive photoproduction in gamma p and p p collisions and inclusive double diffractive Z^0's

We extend the k_\perp-factorization formalism for exclusive photoproduction of vector mesons to the production of electroweak Z^0 bosons. Predictions for the gamma p \to Z^0 p and p p \to p p Z^0 reactions are given using an unintegrated gluon distribution tested against deep inelastic data. We present distributions in the Z^0 rapidity, transverse momentum of Z^0 as well as in relative azimuthal angle between outgoing protons. The contributions of different flavours are discussed. Absorption effects lower the cross section by a factor of 1.5-2, depending on the Z-boson rapidity. We also discuss the production of Z^0 bosons in central inclusive production. Here rapidity and (x_{\Pom,1}, x_{\Pom,2}) distributions of Z^0 are calculated. The corresponding cross section is about three orders of magnitude larger than that for the purely exclusive process.Comment: 19 pages, 14 figs, A. Cisek is married name of A. Rybarsk

Particle spectrum in modified NMSSM

The restrictions on the lightest Higgs boson mass in the minimal supersymmetric models are briefly reviewed. The particle spectrum is considered in the framework of the simplest modification of NMSSM that allows to avoid the domain wall problem and to get the self--consistent solution in the strong Yukawa coupling limit. The lightest Higgs boson mass in the investigated model can reach $125 GeV$ at values of $\tan\beta\ge 1.9$ and does not exceed $130.5\pm 3.5 GeV$.Comment: 4 pages, LaTeX2e. Talk given at the SUSY 2001 Conference in JINR, Dubna, Russi

Exclusive photoproduction of J/ψJ/\psi in proton-proton and proton-antiproton scattering

Protons and antiprotons at collider energies are a source of high energy Weizs\"acker--Williams photons. This may open a possibility to study exclusive photoproduction of heavy vector mesons at energies much larger than possible at the HERA accelerator. Here we present a detailed investigation of the exclusive $J/\psi$ photoproduction in proton-proton (RHIC, LHC) and proton-antiproton (Tevatron) collisions. We calculate several differential distributions in $t_1, t_2, y, \phi$, as well as transverse momentum distributions of $J/\Psi$'s. We discuss correlations in the azimuthal angle between outgoing protons or proton and antiproton as well as in the ($t_1, t_2$) space. Differently from electroproduction experiments, here both colliding beam particles can be a source of photons, and we find large interference terms in azimuthal angle distributions in a broad range of rapidities of the produced meson. We also include the spin--flip parts in the electromagnetic vertices. We discuss the effect of absorptive corrections on various distributions. Interestingly, absorption corrections induce a charge asymmetry in rapidity distributions, and are larger for $p p$ reactions than for the $p \bar p$ case. The reaction considered here constitutes an important nonreduceable background in recently proposed searches for odderon exchange.Comment: 22 pages, 20 figures; dedicated to Kolya Nikolaev on the occasion of his 60th birthday; 4 figures and discussion adde

Elastic pp Scattering at LHC Energies

We consider the first LHC data for elastic pp scattering in the framework of Regge theory with multiple Pomeron exchanges. The simplest eikonal approach allows one to describe differential elastic cross sections at LHC, as well as pp and $\bar{p}p$ scattering at lower collider energies, on a reasonable level.Comment: 11 pages, 5 figures, and 1 tabl

Elastic pppp and pˉp\bar pp scattering in the models of unitarized pomeron

Elastic scattering amplitudes dominated by the Pomeron singularity which obey the principal unitarity bounds at high energies are constructed and analyzed. Confronting the models of double and triple (at $t=0$) Pomeron pole (supplemented by some terms responsible for the low energy behaviour) with existing experimental data on $pp$ and $\bar pp$ total and differential cross sections at $\sqrt{s}\geq 5$ GeV and $|t|\leq 6$ GeV$^{2}$ we are able to tune the form of the Pomeron singularity. Actually the good agreement with those data is received for both models though the behaviour given by the dipole model is more preferable in some aspects. The predictions made for the LHC energy values display, however, the quite noticeable difference between the predictions of models at $t\approx -0.4$ GeV$^{2}$. Apparently the future results of TOTEM will be more conclusive to make a true choice.Comment: Revtex4, 8 pages, 5 figures. Text is improved, no changes in figures and conclusions. Version to be published in Phys. Rev.

Neutrino Mixing and Leptonic CP Phase in Neutrino Oscillations

Oscillations of the Dirac neutrinos of three generations in vacuum are considered with allowance made for the effect of the CP-violating leptonic phase (analogue of the quark CP phase) in the lepton mixing matrix. The general formulas for the probabilities of neutrino transition from one sort to another in oscillations are obtained as functions of three mixing angles and the CP phase. It is found that the leptonic CP phase can, in principle, be reconstructed by measuring the oscillation-averaged probabilities of neutrino transition from one sort to another. The manifestation of the CP phase as a deviation of the probabilities of direct processes from those of inverse processes is an effect that is practically unobservable as yet