arXiv subjects

Mariusz Sadzikowski

Publications and source records attributed to Mariusz Sadzikowski.

At least 19 recordsLinked to original sources

arXiv2026

Twist decomposition of exclusive heavy meson production cross sections

We study the twist decomposition of the total cross sections for exclusive heavy vector meson electroproduction and photoproduction in the $\gamma^\ast p$ processes, within the leading logarithmic $1/x$ BFKL formalism. The Mellin transforms of the impact factors of the vector meson are calculated. We show that the higher twist contributions are strongly suppressed in the low-$x$ kinematical regime. Possible enhancement of the higher twists effects for nuclei targets is discussed.

hep-ph↗

arXiv2026

Nonequilibrium Andreev transport at the QGP-2SC interface

We discuss a nonequilibrium Andreev reflection at an interface between quark-gluon plasma (QGP) and two-flavor color superconducting (2SC) quark matter. Based on the Schwinger-Keldysh framework and a relativistic tunneling model, we evaluate the momentum-resolved tunneling current generated by a chemical-potential bias between the QGP and 2SC phases. We find that the Andreev reflection appears as at the fourth order of the tunneling strength, in which an incident quark in QGP is converted into a reflected hole, while a Cooper pair is injected into the 2SC condensate. We show that the Andreev reflection is enhanced when the bias becomes comparable to the gap and is suppressed in the supergap region, which is similar to that in superconducting materials. The present formulation provides a field-theoretical pathway to strongly-correlated transport across dense-matter interfaces relevant to nonequilibrium dynamics in compact stars.

nucl-th↗

arXiv2023

Twist decomposition of non-linear effects in Balitsky-Kovchegov evolution of proton structure functions

Effects of non-linear small-x evolution of the gluon distribution given by the Balitsky-Kovchegov equation are analyzed within the collinear approximation framework. We perform a twist decomposition of the proton structure functions F2 and FL obtained from the Balitsky-Kovchegov equation using the Mellin representation of the scattering cross-sections at high energies. In both the structure functions we find strong corrections coming from the non-linear effects in the gluon evolution at twist 2, and strongly suppressed higher twist effects. This implies that unitarization effects of high energy scattering amplitudes are mostly the leading twist effect. Furthermore we consider the double logarithmic limit of the Balitsky--Kovchegov equation for the collinear gluon distribution, and compare the result to the Gribov-Levin-Ryskin equation. We find that these two equations differ by two powers of the hard scale logarithm for the large scales.

hep-ph↗

arXiv2019

BFKL Pomeron loop contribution in diffractive photoproduction and inclusive hadroproduction of $J/ψ$ and $Υ$

We analyze contributions to the heavy vector meson production with large transverse momentum in proton--proton and diffractive photon--proton scattering driven by an exchange of two Balitsky--Fadin--Kuraev--Lipatov Pomerons in the squared amplitudes. The Pomerons couple to a single parton and form a Pomeron loop closed by the vector meson impact factors. For the photon--proton case the diffractive cut of the Pomeron loop contributes, and for the inclusive hadroproduction one finds the loop with two cut Pomerons. We compute both of these Pomeron loop contributions and study in detail their properties. The results are then used to calculate the cross sections for diffractive $J/ψ$ photoproduction with large transverse momentum at HERA and the correlated two Pomeron contribution for inclusive $J/ψ$ and $Υ$ production cross sections at the LHC. Within a unified approach a good description of the photoproduction data is found, but correlated two Pomeron mechanism gives only a small contribution to hadroproduction of the vector mesons at the LHC.

hep-ph↗

arXiv2017

Evidence of quasi-partonic higher-twist effects in deep inelastic scattering at HERA at moderate $Q^2$

The combined HERA data for the inclusive deep inelastic scattering (DIS) cross sections for the momentum transfer $Q^2 > 1$ GeV$^2$ are fitted within the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) framework at next-to-leading order (NLO) and next-to-next-to-leading order (NNLO) accuracy, complemented by a QCD-inspired parameterisation of twist 4 corrections. A modified form of the input parton density functions is also included, motivated by parton saturation mechanism at small Bjorken $x$ and at a low scale. These modifications lead to a significant improvement of the data description in the region of low $Q^2$. For the whole data sample, the new benchmark NNLO DGLAP fit yields $χ^2$ / d.o.f. $\simeq 1.2$ to be compared to 1.5 resulting from the standard NNLO DGLAP fit. We discuss the results in the context of the parton saturation picture and describe the impact of the higher-twist corrections on the derived parton density functions. The resulting description of the longitudinal proton structure function $F_L$ is consistent with the HERA data. Our estimates of higher-twist contributions to the proton structure functions are comparable to the leading-twist contributions at low $Q^2 \simeq 2$ GeV$^2$ and $x \simeq 10^{-5}$. The $x$-dependence of the twist 4 corrections obtained from the best fit is consistent with the leading twist 4 quasi-partonic operators, corresponding to an exchange of four interacting gluons in the $t$-channel.

hep-ph↗

arXiv2017

Lam-Tung relation breaking in $Z^0$ hadroproduction as a probe of parton transverse momentum

The Lam-Tung relation breaking coefficient $A_{\mathrm{LT}} = A_0 - A_2$ in the Drell-Yan dilepton angular distributions in the $Z^0$ boson mass region at the LHC is analyzed in the $k_T$-factorization approach. This observable was recently measured with high precision by ATLAS collaboration. Within the $k_T$-factorization approach we perform an approximate ${\cal O}(α_{\mathrm{em}}α_s^2)$ calculation of the off-shell parton hard matrix elements in which we include the leading tree level contributions of valence quarks and off-shell gluons: the $q_{\mathrm{val}} g^* \to qZ^0$ channel and the $g^*g^* \to q\bar q Z^0$ channel. The resulting $A_{\mathrm{LT}}$ exhibits high sensitivity to the gluon transverse momentum distribution (TMD). Several gluon TMDs are probed derived from the CCFM and BFKL evolution equations, and given by QCD-inspired phenomenological parameterizations. The ATLAS data favor a simple "Weizsäcker-Williams" (WW) hard gluon TMD with the asymptotic behavior of one-gluon exchange at large gluon transverse momenta and moderate $x$. It is verified that the proposed approach with the WW gluon TMD describes well also the $A_0$ and $A_2$ angular coefficients at the $Z^0$ peak, as well as the Drell-Yan dilepton mass distribution at lower masses. We conclude that inclusion of gluon transverse momentum effects improves description of the angular distributions of Drell-Yan dileptons and that the Drell-Yan scattering provides an excellent probe of the parton TMDs.

hep-ph↗

arXiv2017

Twist decomposition of Drell-Yan structure functions: phenomenological implications

The forward Drell--Yan process in $pp$ scattering at the LHC at $\sqrt{S}=14$ TeV is considered. We analyze the Drell--Yan structure functions assuming the dominance of a Compton-like emission of a virtual photon from a fast quark scattering off the small $x$ gluons. The color dipole framework is applied to perform quantitatively the twist decomposition of all the Drell--Yan structure functions. Two models of the color dipole scattering are applied: the Golec-Biernat--Wüsthoff model and the dipole cross section obtained from the Balitsky--Fadin--Kuraev--Lipatov evolution equation. The two models have essentially different higher twist content and the gluon transverse momentum distribution and lead to different significant effects beyond the collinear leading twist description. It is found that the gluon transverse momentum effects are significant in the Drell--Yan structure functions for all Drell--Yan pair masses $M$, and the higher twist effects become important for $M \lesssim 10$ GeV. It is found that the structure function $W_{TT}$ related to the $A_2$ angular coefficient and the Lam--Tung observable $A_0 -A_2$ are particularly sensitive to the gluon $k_T$ effects and to the higher twist effects. A procedure is suggested how to disentangle the higher twist effects from the gluon transverse momentum effects.

hep-ph↗

arXiv2016

Twist expansion of forward Drell-Yan process

We present a twist expansion of differential cross-sections of the forward Drell-Yan process at the high energies. The expansion of all invariant form-factors is performed assuming GBW saturation model and the saturation scale plays the role of the hadronic scale of OPE. Some expilicit predictions for LHC experiments are given. It is shown also how the Lam-Tung relation is broken at twist 4 what provides a sensitive probe for searching of higher twists.

hep-ph↗

arXiv2015

Twist expansion of Drell-Yan structure functions in color dipole approach

Forward Drell-Yan process at the LHC probes the proton structure at very small Bjorken-$x$ and moderate hard scales. In this kinematical domain higher twist effects may be significant and introduce sizeable corrections to the standard leading twist description. We study the forward Drell-Yan process beyond the leading twist approximation within the color dipole model framework that incorporates multiple scattering effects. We derive the Mellin representation of the forward Drell-Yan impact factors for fully differential cross-sections. These results combined with the color dipole cross-section of the saturation model are used to perform twist expansion of the Drell-Yan structure functions at arbitrary transverse momentum $q_T$ of the Drell-Yan pair and also of the structure functions integrated over $q_T$. We also investigate the Lam-Tung relation, find that it is broken at twist 4 and provide explicit estimates for the breaking term.

hep-ph↗

arXiv2015

On relevance of triple gluon fusion in $J/ψ$ hadroproduction

A contribution to $J/ψ$ hadroproduction is analyzed in which the meson production is mediated by three-gluon partonic state, with two gluons coming from the target and one gluon from the projectile. This mechanism involves double gluon density in one of the protons, hence this contribution enters at a non-leading twist. It is, however, relevant due to an enhancement factor coming from large double gluon density at small~$x$. We calculate the three-gluon contribution to $J/ψ$ hadroproduction within perturbative QCD in the $k_T$-factorization framework. Results are obtained for differential $p_T$-dependent cross-sections for all $J/ψ$ polarizations and for the sum over the polarization components. The rescattering contribution is found to provide a significant correction to the standard leading twist cross-section at the energies of the Tevatron or the LHC at moderate $p_T$. We suggest $J/ψ$ production in proton-nucleus collision as a possible probe of the triple gluon mechanism.

hep-ph↗

arXiv2014

Twist expansion of differential cross-sections of forward Drell-Yan process

Forward Drell-Yan process at the LHC is a sensitive tool for investigating higher twist effects in QCD. The expansion of all Drell-Yan structure functions is performed assuming GBW saturation model and the saturation scale plays the role of the hadronic scale of OPE. We show that the Lam-Tung relation is broken at twist 4. The results open the way for a forthcoming analysis of multiple scattering and higher twist effects.

hep-ph↗

arXiv2014

On effects of multiple gluons in $J/ψ$ hadroproduction

The three-gluon contribution to $J/ψ$ hadroproduction is calculated within perturbative QCD in the $k_T$ factorization framework. This mechanism involves double gluon density and enters at a non-leading twist, but it is enhanced at large energies due to large double gluon density at small $x$. We obtain results for differential $p_T$-dependent cross-sections for all $J/ψ$ polarisations. The rescattering contribution is found to provide a significant correction to the standard leading twist cross-section at the energies of the Tevatron or the LHC at moderate $p_T$. We also discuss a possible contribution of the rescattering correction to the anti-shadowing effect for $J/ψ$ production in proton - nucleus collisions.

hep-ph↗

arXiv2014

Twist decomposition of proton structure from BFKL and BK amplitudes

An analysis of twist composition of Balitsky-Kovchegov (BK) amplitude is performed in the double logarithmic limit. In this limit the BK evolution of color dipole -- proton scattering is equivalent to BFKL evolution which follows from vanishing of the Bartels vertex in the collinear limit. We perform twist decomposition of the BFKL/BK amplitude for proton structure functions and find compact analytic expressions that provide accurate approximations for higher twist amplitudes. The BFKL/BK higher twist amplitudes are much smaller than those following from eikonal saturation models.

hep-ph↗

arXiv2014

On multiple gluon exchange in J/psi hadroproduction

We consider a contribution to J/psi hadroproduction in which the meson production is mediated by three-gluon partonic state, with two gluons coming from the target and one gluon from the projectile. This mechanism involves double gluon density and thus it enters at a non-leading twist, but it is enhanced at large energies due to large double gluon density at small x. The three-gluon contribution to J/psi hadroproduction is calculated within perturbative QCD in the k_T factorization framework, and it is found to provide a significant correction to the standard leading twist cross-section at the energies of the Tevatron or the LHC. The results are given as differential p_T-dependent cross-sections for J/psi polarization components.

hep-ph↗

arXiv2013

New results on possible higher twist contributions in proton diffractive structure functions at low x

The data on the diffractive deep inelastic scattering (DDIS) at HERA exhibit a strong excess, up to about 100%, above the twist-two NLO DGLAP description at low $Q^2$ and at large energy. I show, that complementing the DGLAP fit by twist 4 and 6 components of the saturation model leads to a good description of data at low $Q^2$ and conclude that the DDIS at HERA provides the first evidence of higher twist effects in DIS.

hep-ph↗

arXiv2013

Chiral Disorder and Random Matrix Theory with Magnetism

We revisit the concept of chiral disorder in QCD in the presence of a QED magnetic field |eH|. Weak magnetism corresponds to |eH| < 1/rho^2 with rho\approx (1/3) fm the vacuum instanton size, while strong magnetism the reverse. Asymptotics (ultra-strong magnetism) is in the realm of perturbative QCD. We analyze weak magnetism using the concept of the quark return probability in the diffusive regime of chiral disorder. The result is in agreement with expectations from chiral perturbation theory. We analyze strong and ultra-strong magnetism in the ergodic regime using random matrix theory including the effects of finite temperature. The strong magnetism results are in agreement with the currently reported lattice data in the presence of a small shift of the Polyakov line. The ultra-strong magnetism results are consistent with expectations from perturbative QCD. We suggest a chiral random matrix effective action with matter and magnetism to analyze the QCD phase diagram near the critical points under the influence of magnetism.

hep-ph↗

arXiv2012

Remark on in-medium masses of hadrons with one heavy quark

In this short note we derive a formula which describes the dependence of the mass of a hadron which contains a single heavy quark on the temperature of the heat bath. It takes a simple scaling form with the exponent which is different than in the case of the light hadrons. The derivation is based on dimensional arguments within the framework of the bag model paradigm. The simple realization of this scenario is presented for the MIT bag model. The mass splitting between pseudoscalar and vector mesons ($D, D^\ast$ or $B, B^\ast$) as a function of temeperature is presented.

hep-ph↗

arXiv2011

Conductance spectroscopy of a correlated superconductor in a magnetic field in the Pauli limit: Evidence for strong correlations

We study conductance spectroscopy of a two-dimensional junction between a normal metal and a strongly-correlated superconductor in an applied magnetic field in the Pauli limit. Depending on the field strength the superconductor is either in the Bardeen-Cooper-Schrieffer (BCS), or in the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) state of the Fulde-Ferrell (FF) type. The strong correlations are accounted for by means of the Gutzwiller method what leads naturally to the emergence of the spin-dependent masses (SDM) of quasiparticles when the system is spin-polarized. The case without strong correlations (with the spin-independent masses, SIM) is analyzed for comparison. We consider both the s-wave and the d-wave symmetries of the superconducting gap and concentrate on the parallel orientation of the Cooper pair momentum Q with respect to the junction interface. The junction conductance is presented for selected barrier strengths (i.e., in the contact, intermediate, and tunneling limits). The conductance spectra in the cases with and without strong correlations differ essentially. Our analysis provides thus an experimentally accessible test for the presence of strong-correlations in the superconducting state. Namely, correlations alter the distance between the conductance peaks (or related conductance features) for carriers with spin-up and spin-down. In the uncorrelated case, this distance is twice the Zeeman energy. In the correlated case, the corresponding distance is about 30-50% smaller, but other models may provide even stronger difference, depending on details of the system electronic structure. It turns out that the strong correlations manifest themselves most clearly in the case of the junction with the BCS, rather than the FFLO superconductor, what should make the experimental verification of the present results simpler.

cond-mat.str-el↗