arXiv subjects

Martin Hentschinski

Publications and source records attributed to Martin Hentschinski.

At least 37 records · Page 2Linked to original sources

arXiv2019

Signs for the onset of gluon saturation in exclusive photo-production of vector mesons

We investigate the energy dependence of the photo-production cross-section of vector mesons $J/Ψ$ and $Υ$, measured by both HERA experiments H1 and ZEUS in electron-proton collisions and by LHC experiments ALICE, CMS and LHCb in ultra-peripheral proton-proton and ultra-peripheral proton-lead collisions. Our study uses 2 particular fits of inclusive unintegrated gluon distribution, based on non-linear Balitsky-Kovchegov evolution (Kutak-Sapeta gluon; KS) and next-to-leading order Balitsky-Fadin-Kuraev-Lipatov evolution (Hentschinski-Sabio Vera-Salas gluon; HSS). We find that linear next-to-leading order BFKL evolution can only describe production at highest energies, if perturbative corrections are increased to unnaturally large values; rendering this corrections small, the growth with energy is too strong in the LHC region and the description of $J/Ψ$ data fails. For the KS gluon we find that an accurate description of $J/Ψ$ data is possible if non-linear corrections to low x QCD evolution are taken into account; without such correction a description of data fails. We interpret this observation as a clear signal for the presence of high gluon densities in low x the proton, characteristic for the onset of gluon saturation.

hep-ph↗

arXiv2018

Superstatistics and the effective QCD phase diagram

We study the effect of a partially thermalized scenario for chiral symmetry restoration at finite temperature and quark chemical potential, and in particular for the position of the critical end point in an effective description of the QCD phase diagram. We show that these effects produce the critical end point to be displaced towards larger values of temperature and lower values of the quark chemical potential as compared to the case when the system can be regarded as completely thermalized. We conclude that these effects may be important for relativistic heavy ion collisions where the number of subsystems making the whole interaction volume can be linked to the finite number of participants in the reaction.

hep-ph↗

arXiv2018

The Color Glass Condensate formalism, Balitsky-JIMWLK evolution and Lipatov's high energy effective action

We investigate the question whether Lipatov's high energy effective action is capable to reproduce quark and gluon propagators which resum interaction with a strong background field within high energy factorization. Such propagators are frequently employed in calculations within the Color Glass Condensate formalism, in particular when considering scattering of a dilute projectile on a dense target nucleus or nucleon. We find that such propagators can be obtained from the high energy effective action, if a special parametrization of the gluonic field is used, first proposed by Lipatov in the original publication on the high energy effective action. The obtained propagators are used to rederive from the high energy effective action the leading order Balitsky-JIMWLK evolution equation in covariant gauge. As an aside, our result confirms the definition of the reggeized gluon as the logarithm of an adjoint Wilson lines, proposed in the literature.

hep-ph↗

arXiv2016

The growth with energy of exclusive $J/Ψ$ and $Υ$ photo-production cross-sections and BFKL evolution

We investigate whether NLO BFKL evolution is capable to describe the energy dependence of the exclusive photo-production cross-section of vector mesons $J/Ψ$ and $Υ$ on protons. Our description is based on available NLO BFKL fits of the proton impact factor in inclusive DIS, which allow us to construct the necessary scattering amplitude at zero momentum transfer $t=0$. Assuming an exponential drop-off with $t$, this result allows us to calculate the exclusive photoproduction cross-section. Comparing our results with both HERA data (measured by H1 and ZEUS collaborations in $ep$ collision) and LHC data (measured by ALICE, CMS and LHCb collaborations in ultra-peripheral $pp$ and $pPb$ collision) we find that our framework provides a very good description of the energy dependence of the $J/Ψ$ and $Υ$ photoproduction cross-section, providing therefore further evidence for BFKL evolution at the LHC. The available fits of the proton impact factor require on the other hand an adjustment in the overall normalization.

hep-ph↗

arXiv2015

Transverse-momentum-dependent quark splitting functions in $k_T$-factorization: real contributions

We calculate transverse momentum dependent quark splitting kernels $P_{gq}$ and $P_{qq}$ within $k_T$-factorization, completing earlier results which concentrated on gluon splitting functions $P_{gg}$ and $P_{qg}$. The complete set of splitting kernels is an essential requirement for the formulation of a complete set of evolution equations for transverse momentum dependent parton distribution functions and the development of corresponding parton shower algorithms.

hep-ph↗

arXiv2015

Single bottom quark production in kT-factorisation

We present a study within the kT-factorisation scheme on single bottom quark production at the LHC. In particular, we calculate the rapidity and transverse momentum differential distributions for single bottom quark/anti-quark production. In our setup, the unintegrated gluon density is obtained from the NLx BFKL Green function whereas we included mass effects to the Lx heavy quark jet vertex. We compare our results to the corresponding distributions predicted by the usual collinear factorisation scheme. The latter were produced with Pythia 8.1.

hep-ph↗

arXiv2014

NLO Vertex for a Forward Jet plus a Rapidity Gap at High Energies

We present the calculation of the forward jet vertex associated to a rapidity gap (coupling of a hard pomeron to the jet) in the BFKL formalism at next-to-leading order (NLO). Real emission contributions are computed via Lipatov's effective action. The NLO jet vertex turns out to be finite within collinear factorization and allows, together with the NLO non-forward gluon Green's function, to perform NLO studies of jet production in diffractive events (e.g. Mueller-Tang dijets).

hep-ph↗

arXiv2014

The Gluon-Induced Mueller-Tang Jet Impact Factor at Next-to-Leading Order

We complete the computation of the Mueller-Tang jet impact factor at next-to-leading order (NLO) initiated in arXiv:1406.5625 and presented in arXiv:1404.2937 by computing the real corrections associated to gluons in the initial state making use of Lipatov's effective action. NLO corrections for this effective vertex are an important ingredient for a reliable description of large rapidity gap phenomenology within the BFKL approach.

hep-ph↗

arXiv2013

On the Practical Application of Physical Anomalous Dimensions

We revive the idea of using physical anomalous dimensions in the QCD scale evolution of deep-inelastic structure functions and their scaling violations and present a detailed phenomenological study of its applicability. Differences with results obtained in the conventional framework of scale-dependent quark and gluon densities are discussed and traced back to the truncation of the perturbative series at a given order in the strong coupling.

hep-ph↗

arXiv2013

Description of F2 and FL at small x using a collinearly-improved BFKL resummation

We present a detailed description of the Q^2 and x dependence of the structure functions F2 and FL as extracted from the Deep Inelastic Scattering data at HERA in the small Bjorken x region. Making use of a collinearly-improved BFKL equation at next-to-leading order and a treatment of the running of the coupling using non-Abelian physical renormalization together with the BLM scale choice allows us to reach low values of Q^2. We also provide some predictions for future lepton-hadron colliders.

hep-ph↗

arXiv2012

NLO corrections to the gluon induced forward jet vertex from the high energy effective action

We determine both real and virtual next-to-leading order corrections to the gluon induced forward jet vertex, from the high energy effective action proposed by Lipatov. For these calculations we employ the same regularization and subtraction formalism developed in our previous work on the quark-initiated vertex. We find agreement with previous results in the literature.

hep-ph↗

arXiv2012

The hard to soft Pomeron transition in small x DIS data using optimal renormalization

We show that it is possible to describe the effective Pomeron intercept, determined from the HERA Deep Inelastic Scattering data at small values of Bjorken x, using next-to-leading order BFKL evolution together with collinear improvements. To obtain a good description over the whole range of Q^2 we use a non-Abelian physical renormalization scheme with BLM optimal scale, combined with a parametrization of the running coupling in the infrared region.

hep-ph↗

arXiv2012

Two-Loop Gluon Regge Trajectory from Lipatov's Effective Action

Lipatov's high-energy effective action is a useful tool for computations in the Regge limit beyond leading order. Recently, a regularisation/subtraction prescription has been proposed that allows to apply this formalism to calculate next-to-leading order corrections in a consistent way. We illustrate this procedure with the computation of the gluon Regge trajectory at two loops.

hep-ph↗

arXiv2012

NLO jet vertex from Lipatov's QCD effective action

Real and virtual contributions to the quark-initiated forward jet vertex in QCD are calculated at next-to-leading logarithmic accuracy using Lipatov's effective action, valid in the high energy multi-Regge limit. A regularization of longitudinal divergencies is proposed which allows for the determination of jet observables. Agreement with previous results in the literature is found.

hep-ph↗

arXiv2011

Unintegrated parton densities at small x

We present recent results on transverse momentum dependent parton densities in the limit of small Bjorken x. A definition of an unintegrated seaquark density is proposed which can be used within the CCFM Monte-Carlo event generator CASCADE. We further discuss aspects of the determination of a NLO BFKL unintegrated gluon density.

hep-ph↗

arXiv2011

Pole prescription of higher order induced vertices in Lipatov's QCD effective action

We investigate Lipatov's QCD effective action for the QCD high energy limit and propose a pole prescription for higher order induced vertices. The latter can be used in the evaluation of loop corrections to high energy factorized matrix elements within the effective action approach. The proposed prescription respects the symmetry properties of the unregulated vertices. Explicit results are presented up to third order in the gauge coupling, while an iterative procedure for higher orders is proposed.

hep-ph↗

arXiv2009

High Energy Behavior of a Six-Point R-Current Correlator in N=4 Supersymmetric Yang-Mills Theory

We study the high energy limit of a six-point R-current correlator in N=4 supersymmetric Yang-Mills theory for finite N_c. We make use of the framework of perturbative resummation of large logarithms of the energy. More specifically, we apply the (extended) generalized leading logarithmic approximation. We find that the same conformally invariant two-to-four gluon vertex occurs as in non-supersymmetric Yang-Mills theory. As a new feature we find a direct coupling of the four-gluon t-channel state to the R-current impact factor.

hep-th↗

arXiv2009

The topology of the triple Pomeron vertex in N=4 SYM

We investigate, within N=4 SYM, the high energy behavior in the triple Regge limit of a six point correlator of R-currents. Using the leading logarithmic approximation, we sum all diagrams whose color lines fit onto the surface of a sphere. We find three distinct classes of graphs, and one of them contains the triple Pomeron vertex known from QCD. We present results which, within the AdS/CFT correspondence, can be compared with scattering amplitudes in the dual string theory.

hep-ph↗