Historical and futuristic perturbative and non-perturbative aspects of QCD jet physics

A brief review of jet physics is presented with an emphasis upon open theoretical problems (non-perturbative domain; hadronization and confinement) and new phenomena (hadroproduction in heavy ion collisions).Comment: Invited talk at the XXXIV International Symposium on Multiparticle Dynamics, Sonoma State University, California, USA, July 26 - August 1, 200

Gribov program of understanding confinement

Invited talk at 9th International Workshop on Deep Inelastic Scattering (DIS 2001), Bologna, Italy, 27 Apr -1 May 200

QCD and Hadron Dynamics

Perturbative QCD predicts and describes various features of multihadron production. An amazing similarity between observable hadron systems and calculable underlying parton ensembles justifies the attempts to use the language of quarks and gluons down to small momentum scales, to approach the profound problems that are commonly viewed as being entirely non-perturbative.Comment: Talk at the Royal Society meeting "Structure of Matter", London, May 200

On large angle multiple gluon radiation

Jet shape observables which involve measurements restricted to a part of phase space are sensitive to multiplication of soft gluon with large relative angles and give rise to specific single logarithmically enhanced (SL) terms (non-global logs). We consider associated distributions in two variables which combine measurement of a jet shape V in the whole phase space (global) and that of the transverse energy flow away from the jet direction, Eout (non-global). We show that associated distributions factorize into the global distribution in V and a factor that takes into account SL contributions from multi-gluon ``hedgehog'' configurations in all orders. The latter is the same that describes the single-variable Eout distribution, but evaluated at a rescaled energy VQ.Comment: 16 page

The internal structure of jets at colliders: light and heavy quark inclusive hadronic distributions

In this paper, we report our results on charged hadron multiplicities of heavy quark initiated jets produced in high energy collisions. After implementing the so-called dead cone effect in QCD evolution equations, we find that the average multiplicity decreases significantly as compared to the massless case. Finally, we discuss on the transverse momentum distribution of light quark initiated jets and emphasize on the comparison between our predictions and CDF data.Comment: 6 pages, 3 figures-Talk presented by Redamy Perez-Ramos at Jets in Proton-Proton and Heavy-Ion Collisions, August 12-14, 2010, Prague, Czech Republi

Hard QCD. Plenary talk at the Quark Matter -97 Conference, December 1997, Tsukuba, Japan

Status of hard/perturbative QCD phenomena is briefly reviewed. Landau-Pomeranchuk-Migdal effect is discussed as a means for establishing links between particle and nuclear high-energy physics.Comment: 13 pages, 4 Postscript figures, uses espcrc1.st

Diffractive Processes at the LHC

We consider diffractive processes which can be measured at the LHC. Analysis of diffractive events will give unique information about the high energy asymptotics of hadron scattering. In semihard diffraction one may study the partonic structure of the Pomeron. Central Exclusive Diffractive production provides a possibility to investigate the new particles (Higgs bosons, SUSY particles,...) in an exceptionally clean environment.Comment: 12 pages, To be published in the Proc. of the Gribov-75 Memorial Workshop, Budapest, May 200

R-Current DIS on a Shock Wave: Beyond the Eikonal Approximation

We find the DIS structure functions at strong coupling by calculating R-current correlators on a finite-size shock wave using AdS/CFT correspondence. We improve on the existing results in the literature by going beyond the eikonal approximation for the two lowest orders in graviton exchanges. We argue that since the eikonal approximation at strong coupling resums integer powers of 1/x (with x the Bjorken-x variable), the non-eikonal corrections bringing in positive integer powers of x can not be neglected in the small-x limit, as the non-eikonal order-x correction to the (n+1)st term in the eikonal series is of the same order in x as the nth eikonal term in that series. We demonstrate that, in qualitative agreement with the earlier DIS analysis based on calculation of the expectation value of the Wilson loop in the shock wave background using AdS/CFT, after inclusion of non-eikonal corrections DIS structure functions are described by two momentum scales: Q_1^2 ~ \Lambda^2 \, A^{1/3}/x and Q_2^2 ~ \Lambda^2 \, A^{2/3}, where \Lambda is the typical transverse momentum in the shock wave and A is the atomic number if the shock wave represents a nucleus. We discuss possible physical meanings of the scales Q_1 and Q_2.Comment: 44 pages, 3 figures; v2: typos corrected, refs added, discussion extende

Ioffe Time in Double Logarithmic Approximation

We analyze the light cone (Ioffe) time structure of the gluon distribution function in the double logarithmic approximation. We show that due to QCD evolution Ioffe equation is modified. The characteristic light cone time of the gluons does not increase as fast with increasing energy (decreasing Bjorken x) as predicted by the parton distributions exhibiting Bjorken scaling due to the increase of the transverse momenta of the gluons in the DGLAP ladder.Comment: 13 pages, 1 figur