Perturbative QCD Pomeron Research Articles

Secondary hadron distributions in a two component model

Inclusive charged hadron cross sections, $d\ensuremath{\sigma}/d\ensuremath{\eta}$, and the mean transverse momenta, $⟨{p}_{T}⟩$, are considered within the two component model, which combines the powerlike and the exponential terms in ${p}_{T}$. The observed dependences of the spectra shape on energy and the event multiplicity qualitatively agree with that expected from the Regge theory with the perturbative QCD Pomeron. Finally, the dependences observed are used to make predictions on the mean transverse momenta, $⟨{p}_{T}⟩$, as function of multiplicity at LHC energies, which are tested on available experimental data.

Initial condition for evolution of the perturbative QCD Pomeron in a nucleus

We show that subdominant terms obtained using the reggeized gluon diagram technique, which should be added to Pomeron fan diagrams with the triple-Pomeron interaction, can be taken into account exactly if the initial condition for the evolution is chosen in the Glauber form. This demonstrates the complete equivalence of the dipole picture and the reggeized gluon technique in the high-energy limit not only in the leading order but also in the next order.

Vector meson production in ultraperipheral heavy ion collisions

Ultraperipheral heavy ion collisions (UPCs) are an important alternative for studying QCD dynamics until the next generation of e+e−/ep/eA colliders becomes a reality. Due to the coherent action of all the protons in the nucleus, the electromagnetic field is very strong and the resulting flux of equivalent photons is large, which allows us to study two-photon as well as photonuclear interactions at high energies. In this paper we present a brief review of the vector meson production in UPCs at high energies using the QCD colour dipole approach to describe their photonuclear production and the perturbative QCD Pomeron (BFKL dynamics) to describe the double meson production in photon–photon processes. Predictions for rates and integrated cross sections are presented for energies of RHIC and LHC.

Jet production in pA and AA collisions in the perturbative QCD pomeron model

Inclusive cross-sections for gluon jet production are studied numerically in the perturbative QCD pomeron model for pA and central AA collisions at high energies. Two forms for the inclusive cross-sections, with and without emission from the triple pomeron vertex, are compared. The difference was found to reduce to a numerical factor 0.7-0.8 for momenta below the saturation momentum Q_s. Above Q_s no difference was found at all. For pA collisions the jet spectrum was found to be \sim A^{0.7} at momenta below Q_s and \sim A^{0.9} above it. For central AA collisions it was found to be \sim A below Q_s and \sim A^{1.1} above it. At large momenta k the spectrum goes like 1/k^{2.7 - 3.3} flattenung with energy.

Inclusive cross-sections for jet production in nucleus–nucleus collisions in the perturbative QCD pomeron model

Inclusive cross-sections for gluon jet production are studied numerically in the perturbative QCD pomeron model for central collisions of identical nuclei at high energies. Two forms for the inclusive cross-sections, with and without emission from the triple pomeron vertex, are compared. The difference was found to reduce to a numerical factor 0.8–0.9 for momenta below the saturation momentum Qs. Above Qs no difference was found at all. The gluon spectrum was found to be ∼A at momenta k below Qs and ∼A1.1 above it. At large k the spectrum goes like 1/k2.7–3.3 flattening with energy. The multiplicities turned out to be proportional to A with a good precision. Their absolute values are high and grow rapidly with energy in accordance with the high value of the BFKL intercept.

The effect of higher order corrections to the BFKL equation on the perturbative pomeron

We discuss the significance of the next-to-leading order term in the BFKL equation on the energy dependence of diffractive processes controlled by the perturbative QCD pomeron. It is shown that whereas the large negative corrections do indeed reduce the rate of growth of diffractive amplitudes with increasing energy, this reduction is considerably less than previously expected.

Jet production from the perturbative QCD pomeron with a running coupling constant

An analysis of minijet production from the hard pomeron with a running coupling constant is performed. Two supercritical pomerons found in the numerical study are taken into account. The calculated inclusive jet production rate is finite at small k ⊥ and behaves like 1 k ⊥ −4 at high k ⊥ modulo factors coming from logarithmic terms. The average k ⊥ is found to be very large (∼ 10 – 13 GeV/c) and practically independent of energy. This is interpreted as an indication that at present energies we are still far from the asymptotics and that, apart from supercritical pomerons, other states contribute significantly.

Photon diffractive dissociation and the QCD pomeron

The space - time picture for high energy photon dissociation and the properties of the perturbative QCD (BFKL) pomeron are discussed as well as the and behaviour of and (i.e. into two- or three-jet) cross sections.

Pomeron and multiparticle production.

A new model for high energy hadron-hadron interactions based on the Pomeron containing both ``soft`` and perturbative contributions is presented. Its intercept is expressed through the intercept of the Reggeized gluon. The multigluon intermediate state of hadronic interactions is obtained from the equation of the perturbative QCD Pomeron. Implementing the model in a Monte Carlo event generator, a systematic study of a broad range of data in a wide energy range is performed. The energy dependence of rapidity and transverse momentum spectra, the violation of the Koba-Nielsen-Olesen scaling of multiplicity distribution, and the increase of the correlations among final state particles are shown to be simultaneously well described. Predictions of the model up to the energies of the future supercolliders are given.

Multiparticle production at TeV energies and the QCD Pomeron.

A model for multiparticle production at TeV energies is proposed in which a semihard production mechanism based on the perturbative QCD Pomeron plays an essential role. The implementation of the model as a simulation program is described. A resonable description of available data is achieved.

Properties of the perturbative QCD pomeron and structure functions at low X

Properties of the perturbative QCD pomeron and structure functions at low X

Deep-inelastic events containing a measured jet as a probe of QCD behavior at small x.

We examine the proposal that deep-inelastic ({ital x},{ital Q}{sup 2}) scattering events which contain an identified jet, with transverse momentum squared {ital k}{sup 2}{congruent}{ital Q}{sup 2}, allow an ideal determination of the QCD behavior at very small {ital x}. We solve the Lipatov equation to predict the shape of the jet spectrum in such events and show that measurements at the DESY {ital ep} collider HERA should be able to verify, inter alia, whether the gluon indeed has the theoretically anticipated {ital g}{similar to}{ital x}{sup {minus}{alpha}}{sub {ital P}} small-{ital x} behavior with the intercept {alpha}{sub {ital P}} of the bare perturbative QCD Pomeron possible as large as 1.5.

Pomeron physics in diffractive deep inelastic scattering at large 1/x

I review recent progress in the perturbative QCD approach to pomeron physics in deep inelastic scattering (DIS) at large1/x.(refs.1–4). I discuss the crucial role the color transparency plays in a diffractioe DIS, and how it can be quantified in terms of the wave function (WF) of (partonic) hadronic fluctuations of photons and universal, flavour independent, qqpair interaction cross section. Different DIS processes probe this universal cross section at different sizes. The emerging WF formalism greatly simplifies the involved calculations. I present quantitative predictions for the nuclear shadowing and the diffraction dissociation (DD) rate in DIS, and the valence and sea quark distributions in a QCD Pomeron. I point out a dramatic difference of sea densities in a nucleon as probed by muons and neutrinos and flavour dependence of the pomeron couplings in DD and conclude that perturbative QCD pomeron does not factorize. I emphasize a numerical importance of shadowing in deuterium for tests of the Gottfried sum rule.

Pomeron physics in diffractive deep inelastic scattering at large

I review recent progress in the perturbative QCD approach to pomeron physics in deep inelastic scattering (DIS) at large 1 x .(refs.1–4). I discuss the crucial role the color transparency plays in a diffractive DIS, and how it can be quantified in terms of the wave function (WF) of (partonic) hadronic fluctuations of photons and universal, flavour independent, q q pair interaction cross section. Different DIS processes probe this universal cross section at different sizes. The emerging WF formalism greatly simplifies the involved calculations. I present quantitative predictions for the nuclear shadowing and the diffraction dissociation (DD) rate in DIS, and the valence and sea quark distributions in a QCD Pomeron. I point out a dramatic difference of sea densities in a nucleon as probed by muons and neutrinos and flavour dependence of the pomeron couplings in DD and conclude that perturbative QCD pomeron does not factorize. I emphasize a numerical importance of shadowing in deuterium for tests of the Gottfried sum rule.