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M. A. Braun

Publications and source records attributed to M. A. Braun.

At least 55 records · Page 3Linked to original sources
arXiv2013

Inclusive cross-sections for gluon production in collision of two projectiles on two targets in the BFKL approach

Inclusive cross-sections for gluon production in collision of two mucleons with two nucleons are studied in the BFKL approach. Various contributions include emission from the pomerons attached to the participants, from the BFKL interactions in between these pomerons and from the intermediate BKP state. The last contribution may be observable provided the growth with energy of the pomeron contribution is tamed in accordance with unitarity.

hep-ph↗
arXiv2013

On the collision of two projectiles on two targets in the BFKL approach

High-energy collisions of two nucleons on two nucleons are studied in the BFKL approach in the leading approximation in $α_sN_c$. Diagrams with redistribution of colour are considered. It is found that intermediate BKP states consisting of 4 reggeized gluons give a contribution which may be leading in deuteron-deuteron scattering and thus experimentally observable.

hep-ph↗
arXiv2012

Production of a gluon with the exchange of three reggeized gluons in the Lipatov effective action approach

In the Regge kinematics the amplitude for gluon production off three scattering centers is found in the Lipatov effective action technique. The vertex for gluon emission with the reggeon splitting in three reggeons is calculated and its transversality is demonstrated. It is shown that in the sum of all contributions terms containing principal value singularities are cancelled and substituted by the standard Feynman poles. These results may be used for calculation of the inclusive cross-section for gluon production on two nucleons in the nucleus.

hep-ph↗
arXiv2012

Anisotropic flows from colour strings: Monte-Carlo simulations

By direct Monte-Carlo simulations it is shown that the anisotropic flows can be successfully described in the colour string picture with fusion and percolation provided anisotropy of particle emission from the fused string is taken into account. Quenching of produced particles in the strong colour field of the string is the basic mechanism for this anisotropy. The concrete realization of this mechanism is borrowed from the QED. Due to dependence of this mechanism on the external field strength the found flows grow with energy, with values for $v_2$ at LHC energies greater by ~15% than at RHIC energies.

hep-ph↗
arXiv2012

BFKL pomeron in the external field of the nucleus in (2+1)-dimensional QCD

The behaviour of the pomeron propagator in the external nuclear field is studied in the (2+1)-dimensional QCD. It is shown that in the physically interesting case when the field does not vanish at large rapidities the propagator in the field vanishes much faster than in the vacuum, in agreement with the results found in the local Regge-Gribov model. However if the nuclear field vanishes at high rapidities the field does not change the behaviour of the pomeron propagator.

hep-ph↗
arXiv2012

On the inclusive gluon production in the Lipatov effective action formalism

The process of gluon production in quark-nucleus collisions is studied in the framework of Lipatov's effective action formalism. The relevant simplifications and rules for longitudinal integrations are discussed in detail. The results obtained with the help of these rules correspond to the purely transversal formalism based on effective vertices in the transversal space.

hep-ph↗
arXiv2011

Gluon production on two centers and the effective action approach

Application of the effective action formalism is studied for processes in which the reggeons may split. It is shown that the gluon production on two centers is described by the contribution of the Reggeon-to-two-Reggeons-plus-Particle vertex supplemented by certain singular contributions from the double gluon exchange. The rules for longitudinal integrations are established from the comparison to perturbative QCD amplitude. Convenient expressions for application to the inclusive gluon production are derived.

hep-ph↗
arXiv2011

BFKL pomeron propagator in the external field of the nucleus

It is shown by numerical calculations that the convoluted QCD pomeron propagator in the external field created by a solution of the Balitsky-Kovchegov equation in the nuclear matter vanishes at high rapidities. This may open a possibility to apply the perturbative approach for the calculation of pomeron loops.

hep-ph↗
arXiv2010

Forward pomeron propagator in the external field of the nucleus

It is shown by numerical calculations that the convoluted forward pomeron propagator in the external field created by a solution of the Balitski-Kovchegov equation in the nuclear matter vanishes at high rapidities. This may open a possibility to apply the perturbative approach for the calculation of pomeron loops.

hep-ph↗
arXiv2010

Elliptic flow from color strings

It is shown that the elliptic flow can be successfully described in the color string picture with fusion and percolation provided anisotropy of particle emission from the fused string is taken into account. Two possible sources of this anisotropy are considered, propagation of the string in the transverse plane and quenching of produced particles in the strong color field of the string. Calculations show that the second source gives an overwhelming contribution to the flow at accessible energies.

hep-ph↗
arXiv2010

A study of nucleon-deuteron elastic scattering in configuration space

A new computational method for solving the nucleon-deuteron breakup scattering problem has been applied to study the elastic neutron- and proton-deuteron scattering on the basis of the configuration-space Faddeev-Noyes-Noble-Merkuriev equations. This method is based on the spline-decomposition in the angular variable and on a generalization of the Numerov method for the hyperradius. The Merkuriev-Gignoux-Laverne approach has been generalized for arbitrary nucleon-nucleon potentials and with an arbitrary number of partial waves. The nucleon-deuteron observables at the incident nucleon energy 3 MeV have been calculated using the charge-independent AV14 nucleon-nucleon potential including the Coulomb force for the proton-deuteron scattering. Results have been compared with those of other authors and with experimental proton-deuteron scattering data.

nucl-th↗
arXiv2010

BKP states in the inclusive gluon production

Inclusive cross-section for gluon production is calculated by the dispersion technique in the NLO in the perturbative QCD with a large number of colours. The found cross-section coincides with the one derived in the dipole picture. No trace of the BKP states is found.

hep-ph↗
arXiv2010

Hadron-nucleus scattering in the local reggeon model with pomeron loops for realistic nuclei

Contribution of simplest loops for hadron-nucleus scattering cross-sections is studied in the Local Reggeon Field Theory with a supercritical pomeron. It is shown that inside the nucleus the supercritical pomeron transforms into a subcritical one, so that perturbative treatment becomes possible. The pomeron intercept becomes complex, which leads to oscillations in the cross-sections.

hep-ph↗
arXiv2010

Production of two gluons in the Lipatov effective action formalism

The one-loop diffractive amplitude for emission of two real gluons with widely different rapidities is studied in the Lipatov effective action formalism. It is shown that after integration over longitudinal momenta in the loop the resulting expression coincides with the one obtained by the Lipatov-Bartels formalism in transversal space provided the same prescription is used to exclude divergent contributions as previously proposed for emission of a single real gluon.

hep-ph↗
arXiv2009

Jet energy loss due to multiple scattering in the nucleus

Energy loss of a jet due to multiple collisions in the nuclear target is studied in the framework of the perturbative QCD with an infrared cutoff. An iterational procedure for its calculation is developed, which allows to reliably find up to 16 successive collisions in rescattering. The calculated shift of the scaling variable reaches values of the order 0.1 at medium $x$ and transverse momentum $p$ in the interval 5-10 GeV/c. The shift is found to be independent of the atomic number of the target and energy.

hep-ph↗
arXiv2009

Pomeron loops in the perturbative QCD with Large N_c

The lowest order pomeron loop is calculated for the leading conformal weight with full dependence of the triple pomeron vertex on intermediate conformal weights. The loop is found to be convergent. Its contribution to the pomeron Green function begins to dominate already at rapidities 10$÷$15. The pomeron pole renormalization is found to be quite small due to a rapid fall of the triple pomeron vertex with rising conformal weights.

hep-ph↗