The simplest version of a class of toy models for QCD is presented. It is a Lipkin-type model, for the quark-antiquark sector, and, for the gluon sector, gluon pairs with spin zero are treated as elementary bosons. The model restricts to mesons with spin zero and to few baryonic states. The corresponding energy spectrum is discussed. We show that ground state correlations are essential to descr...

It is by now well understood that spin asymmetry in deep inelastic scattering (DIS) can appear if two things are both present: (i) a chirality flip of the struck quark; (ii) a nonzero T-odd phase due to its final state interaction. So far (i) was attributed to a new structure/wave function of the nucleon and (ii) to some gluon exchanges. We propose a new mechanism utilizing strong vacuum fluctu...

The QCD factorization theorem for diffractive processes in DIS is used to derive the leading twist contribution to the nuclear shadowing of partons due to the coherent projectile (photon) interactions with two nucleons (the low thickness limit). We calculate nuclear structure functions in the limit of large thickness (the black interaction limit). Based on the current analyzes of diffraction at...

The medium induced energy loss spectrum of a high energy quark or gluon traversing a hot QCD medium of finite volume is studied. We model the interaction by a simple picture of static scattering centres. The total induced energy loss is found to grow as L, where L is the extent of the medium. The solution of the energy loss problem is reduced to the solution of a Schrödingerlike equation whose ...

QCD critical point is a landmark region in the phase diagram outlined by temperature as function of baryon chemical potential. To right this second-order transition point, one expects first order quark-hadron boundary, towards left crossover region, top it lies quark gluon plasma and below hadronic phase. Hence locating through relativistic heavy-ion collision experiments an active area researc...

We study the coherent final state interaction of an energetic parton produced in AA collisions caused by the change in the cutoff scale and running coupling constant from the vacuum to QGP. We demonstrate that the contribution of this new mechanism to the energy loss may be of the order of magnitude of the induced gluon radiation. However, an accurate evaluation of this medium effect is a diffi...

It is pointed out that the diagonal amplitude of the E1 − E1 chromo-electric interaction with soft gluon fields (chromo-polarizability) can be measured directly for the J/ψ and Υ resonances in the decays J/ψ → ππℓ + ℓ − and Υ → ππℓ + ℓ − with soft pions. For the J/ψ this amplitude is often discussed in connection with the J/ψ interaction with nuclear matter, while for the Υ the chromo-polarizab...

Following our recent paper on the calculations of diffractive quark jet production at hadron colliders, we present here the calculations of gluon jet production at hadron colliders in the two-gluon exchange parameterization of the Pomeron model. We use the helicity amplitude method to calculate the cross section formula. We find that for the gluon jet production the diffractive process is relat...