Elliptical flows in Reggeon theory

A new mechanism for the generation of an azimuthal anisotropy of particles produced in heavy-ion collisions is analyzed. An analysis is performed within Reggeon theory and is general. The resulting effect can be interpreted in terms of the partonic structure of a fast nucleus. This mechanismcan contribute significantly to the observed value of the elliptic flow υ ₂. The dynamics in question differs significantly from a standard mechanism of the collective motion of a hadron medium after a collision.

     

On helicity conservation in the reaction π−p → A1p at 4.45 GeV/c

Helicity conservation in the reaction π^? p → pA₁ at 4.45 GeV/c has been studied using 50 cm and 55 cm liquid hydrogen bubble chambers. In the Jackson and the helicity frames the dependence of the ? matrix elements on the four-momentum transfer squared to the proton (t) for A₁ maximum decay has been calculated. The obtained data are in a good agreement with t-channel helicity conservation. The t-channel dependence of the ? matrix elements in the mentioned frames is in good agreement with that calculated using the Regge π-pole exchange model (it is suggested that the A₁ maximum nature is explained by a kinematical effect of the Deck type).     

Glueball spectrum and Pomeron in the Wilson loop approach

Using a nonperturbative method based on the asymptotic behavior of Wilson loops, we calculate the masses of glueballs and the corresponding Regge trajectories. The only input is the string tension fixed by the meson Regge slope, while perturbative contributions to spin splittings are defined by standard α_s values. The masses of the lowest glueball states are in a perfect agreement with lattice results. The leading glueball trajectory, which is associated with the Pomeron is discussed in detail, and its mixing with f and f′ trajectories is taken into account.     

Extending the study of the Higgs sector at the LHC by proton tagging

We show that forward proton tagging may significantly enlarge the potential of studying the Higgs sector at the LHC. We concentrate on Higgs production via central exclusive diffractive processes (CEDP). Particular attention is paid to regions in the MSSM parameter space where the partial width of the Higgs boson decay into two gluons much exceeds the SM case; here the CEDP are found to have special advantages.Received: 10 November 2003, Published online: 4 February 2004     

Distribution of valence quarks in hadrons at small x in QCD

Valence u- and d-quark distributions in nucleons and pions at small x corresponding to ? and ω Regge pole exchanges have been obtained on the basis of the QCD sum rule method.     

Nuclear shadowing in Glauber–Gribov theory with Q 2-evolution

We consider deep inelastic scattering off nuclei in the Regge limit within the Glauber–Gribov model. Using unitarized parton distribution functions for the proton, we find sizeable shadowing effects on the nuclear total and longitudinal structure functions, $F_{2}^{A}$ and $F_{L}^{A}$ , in the low-x limit. Extending a fan-diagram analysis for the large-mass region of coherent diffraction off nuclei to high Q ², we also find significant shadowing effects in this kinematical regime. Finally, we discuss the shortcomings of our approach and possible extensions of the model to other kinematical regimes.