arXiv subjects
Publications and source records attributed to A. Kaidalov.
Proceedings of the 13th International Conference on Elastic and Diffractive Scattering (Blois Workshop) - Moving Forward into the LHC Era
Proceedings of the 12th International Conference on Elastic and Diffractive Scattering (Blois Workshop) - Forward Physics and QCD
We calculate shadowing using new data on the gluon density of the Pomeron recently measured with high precision at HERA. The calculations are made in a Glauber-Gribov framework and Pomeron tree-diagrams are summed up within a unitarity-conserving procedure. The total cross section of $\vphot A$ interaction is then found in a parameter-free description, employing gluon diffractive and inclusive distribution functions as input. A strong shadowing effect is obtained, in good agreement with several other models. Impact parameter dependence of gluon shadowing is also presented.
Using a final state interaction model which describes the data on these two observables, at RHIC, we make predictions at the LHC -- using the same cross-section and pT-shift. The increase in the medium density between these two energies (by a factor close to three) produces an increase of the fixed pT pi0 suppression by a factor 2 at large pT and of v2 by a factor 1.5.
The NA50 collaboration data on the $J/ψ$ suppression are compared with the results obtained in a comovers approach based on the Dual Parton Model (DPM). Predictions for the $J/ψ$ suppression versus the charged multiplicity - measured in the rapidity region of the dimuon trigger - are given for SPS and RHIC energies.
A short summary of main results of theoretical talks presented at XXIX International Symposium on Multiparticle Dynamics is given.
Gribov approach to high-energy interactions of hadrons and nuclei is reviewed and applied to calculation of particle production in heavy-ions collisions. It is pointed out that the AGK (Abramovsky, Gribov, Kancheli) cutting rules is a powerful tool to investigate particle spectra in these processes. It leads, in the Glauber approximation, to a simple formula for the density of hadrons produced in the central rapidity region in nucleus-nucleus interactions. An estimate of this density for RHIC and LHC is presented and compared with results of Monte-Carlo calculations. It is shown that the Glauber approximation substantially overestimate particle densities compared to the results of the complete Gribov theory. This is due to extra shadowing in the system, related to large mass diffraction which leads to a strong decrease of particle densities at mid rapidities. Our method of calculation of these effects has been applied to the problem of shadowing of nuclear structure functions and a good agreement with experimental data has been obtained.
Properties of multiparticle final states produced in the central rapidity region of small-x deep inelastic scattering (DIS) are discussed. It is pointed out that these properties contain important information on the nature of the Pomeron - used for the description of total cross section and diffractive production in DIS. It is shown that models based on universality of the Pomeron predict charged particle multiplicities in small-x DIS which are in good agreement with recent HERA results.
Gribov theory is applied to investigate the shadowing effects in the structure functions of nuclei. In this approach these effects are related to the process of diffractive dissociation of a virtual photon. A model for this diffractive process, which describes well the HERA data, is used to calculate the shadowing in nuclear structure functions. A reasonable description of the $x$, $Q^2$ and A-dependence of nuclear shadowing is achieved.
Gribov theory is applied to investigate the shadowing effects in the structure functions of nuclei. In this approach these effects are related to the process of diffractive dissociation of a virtual photon. A model for this diffractive process, which describes well the HERA data, is used to calculate the shadowing in nuclear structure functions. A reasonable description of the x, Q^2 and A-dependence of nuclear shadowing is achieved.
We study the combined effect of nuclear absorption and final state interaction with co-moving hadrons on the $J/Ψ$ and $Ψ'$ suppression in proton-nucleus and nucleus-nucleus collisions. We show that reasonable description of the experimental data can be achieved with theoretically meaningful values of the cross-sections involved and without introducing any dicontinuity in the $J/Ψ$ or $Ψ'$ survival probabilities.
The rapidity distribution of $Λ$ and $\barΛ$ produced in nucleus-nucleus collisions at CERN energies is studied in the framework of an independent string model - with quark-antiquark as well as diquark-antidiquark pairs in the nucleon sea. It is shown that, besides the $Λ$-$\barΛ$ pair production resulting from the fragmentation of sea diquarks, final state interactions of co-moving secondaries $π+ N \to K + Λ$ and $π+ \bar{N} \to K + \barΛ$ are needed in order to reproduce the data. Predictions for $Pb$-$Pb$ collisions are presented.
We show that the previously introduced CKMT model, based on conventional Regge theory, gives a good description of the HERA data on the structure function F_2^D for large rapidity gap (diffractive) events. These data allow, not only to determine the valence and sea quark content of the Pomeron, but also, through their Q^2 dependence, give information on its gluonic content. Using DGLAP evolution, we find that the gluon distribution in the Pomeron is very hard and the gluons carry more momentum than the quarks. This indicates that the Pomeron, unlike ordinary hadrons, is a mostly gluonic object. With our definition of the Pomeron flux factor the total momentum carried by quarks and gluons turns out to be 0.3-0.4 - strongly violating the momentum sum rule.
The diffraction dissociation of virtual photons is considered in the framework of conventional Regge theory. It is shown that the recent HERA data on large rapidity gap events can be successfully described in terms of the Pomeron structure function. Using Regge factorization, the latter can be related to the deuteron structure function. The parameters which relate these two structure functions are determined from soft hadronic diffraction data. The size of the shadowing corrections at low x and large Q**2 is also obtained.
In the framework of conventional Regge theory we present a common description of total photon-proton cross-section and proton structure functions in the region $0 \leq Q^2 \leq 5 \ {\rm GeV}^2$. Using it as an initial condition in the perturbative QCD evolution equation, we describe structure functions at any $Q^2$ and $x$ - including the small $x$ region explored at HERA.