arXiv subjects

Anna Cisek

Publications and source records attributed to Anna Cisek.

At least 19 recordsLinked to original sources

arXiv2025

Production of open and hidden charm in fixed-target experiments at the LHC

We discuss the production of $D$ mesons and $J/\psi$ quarkonia in proton-nucleus collisions in the fixed-target LHCb experiment. We consider gluon-gluon fusion within $k_t$-factorization, processes initiated by intrinsic charm in the nucleon and perturbative recombination mechanism. All the mechanisms seem to be necessary to describe the LHCb experimental data. We get an upper limit for the probability of the large-$x$ $c \bar c$ Fock component in the nucleon, which is slightly less than 1 \%. The recombination mechanism allows the description of $D^0$ and $\bar D^0$ asymmetry observed by the LHCb collaboration.\\ We also discuss the production of $J/\psi$ quarkonia, including color singlet mechanisms. We include $g^* g^* \to J/\psi g$ and $g^* g^* \to \chi_c(1^+,2^+)(\to J/\psi \gamma)$ within $k_t$-factorization approach. Different unintegrated gluon distributions from the literature are used. A reasonable agreement is achieved with some distributions from the literature.

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arXiv2025

Prompt inclusive production of $J/\psi$, $\psi'$ and $\chi_{c}$ mesons at $\sqrt{s}$ $=$ $68.5$ $GeV$ energy within NRQCD $k_t$-factorization approach

We discuss prompt production of $J/\psi$ mesons in proton-proton collisions at the $\sqrt{s}$ $=$ $68.5$ $GeV$ energy within NRQCD $k_t$-factorization approach using different unintegrated gluon distributions functions (UGDFs). We include both direct color-singlet production ($g g \to J/\psi g$) as well as a feed-down from $\chi_c \to J/\psi \gamma$ and $\psi' \to J/\psi X$ decays. The production of the decaying mesons $\chi_c$ or $\psi'$ is also calculated within NRQCD $k_t$-factorization approach. Differential distributions in rapidity and transverse momentum of $J/\psi$ are calculated and compared with experimental data of the LHCb collaborations. The LHCb fixed target data allow to test UGDFs in a new range of $x$.

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arXiv2022

Exclusive production of $ρ$ meson in gamma-proton collisions: $d σ/dt$ and the role of helicity flip processes

We calculate the differential cross section $dσ/dt$ for the diffractive photoproduction process $γp \to ρp$ and compare to recent data extracted by the CMS collaboration from ultraperipheral proton-lead collisions. Our model is based on two-gluon exchange in the nonperturbative domain. We take into account both helicity conserving and often neglected helicity-flip amplitudes in the $γ\to V$ transition. The letter can contribute at finite $t$. The shape of the differential cross section as well as the role of helicity flip processes is strongly related to the dependence of the unintegrated gluon distribution on transverse momenta in the nonperturbative region.

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arXiv2022

Structure and production mechanism of the enigmatic $X(3872)$ in high-energy hadronic reactions

We calculate the total cross section and transverse momentum distributions for the production of enigmatic $χ_{c,1}(3872)$ (or X(3872)) assuming different scenarios: $c \bar c$ state and $D^{0*} {\bar D}^0 + D^0 {\bar D}^{0*}$ molecule. The derivative of the $c \bar c$ wave function needed in the first scenario is taken from a potential model calculations. Compared to earlier calculation of molecular state we include not only single parton scattering (SPS) but also double parton scattering (DPS) contributions. The latter one seems to give smaller contribution than the SPS one. The upper limit for the DPS production of $χ_{c,1}(3872)$ is much below the CMS data. We compare results of our calculations with existing experimental data of CMS, ATLAS and LHCb collaborations. Reasonable cross sections can be obtained in either $c \bar c$ or molecular $D {\bar D}^*$ scenarios for $X(3872)$. Also a hybrid scenario is not excluded.

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arXiv2021

Two-gluon production of $ϕ$ and $η'$ mesons in proton-proton collisions at high energies

We discuss gluon-gluon mechanisms for production of mesons with hidden strangeness, such as $η'$ and $ϕ$ meson, in proton-proton collisions at large energies. The $g^* g^* \to η'$ and $g^* g^* \to ϕg$ mechanisms are considered only and the corresponding cross sections are calculated in the $k_t$-factorization approach. The $F_{γ^* γ^* \to η'}$ and $F_{g^* g^* \to η'}$ form factors are calculated from quark-antiquark $η'$ light-cone wave function including quark/antiquark transverse momenta. The result for two-photon transition form factor demonstrates that higher twists may survive even to large photon virtualities. The result is compared with the result of a recent leading-twist NLO analysis which uses phenomenological distribution amplitudes fitted to exclusive production of $η'$ in $e^+ e^- \to e^+ e^- η'$ reaction. We calculate transverse momentum distributions of both $η'$ and $ϕ$ mesons in proton-proton collisions for RHIC and LHC energies. The results are compared to experimental data whenever available. The results of the Lund string model are shown for comparison for $η'$ production at LHC energies. It seems that the two-gluon fusion is not the dominant mechanism for both $ϕ$ and $η'$ production, although the situation for $η'$, especially at larger energies, is less clear due to lack of experimental data.

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arXiv2019

Semiexclusive production of vector mesons in proton-proton collisions with electromagnetic dissociation

We calculate distributions of different vector mesons in purely exclusive ($p p \to p p V$) and semi-exclusive ($p p \to p X V$) processes with electromagnetic dissociation of a proton. The cross section for the electromagnetic dissociation is expressed through electromagnetic structure functions of the proton. We include the transverse momentum distribution of initial photons in the associated flux. Contributions of the exclusive and semi-exclusive processes are compared for different vector mesons ($V = ϕ, J/ψ, Υ$). We discuss how the relative contribution of the semi-exclusive processes depends on the mass of the vector meson as well as on different kinematical variables of the vector meson ($y$, $p_t$). The ratio of semi-exclusive to exclusive contributions are shown and compared for different mesons in different variables.

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arXiv2018

$J/ψ$-meson production within improved color evaporation model with the $k_{T}$-factorization approach for $c\bar{c}$ production

We use a new approach to color evaporation model (CEM) for quarkonium production. The production of $c\bar c$ pairs is performed within $k_T$-factorization approach using different unintegrated gluon distribution functions (UGDF) from the literature. We include all recent improvements to color evaporation model. We cannot describe simultaneously mid and forward rapidity data measured at the LHC when using the KMR UGDF with the same normalization parameter. Furthermore we get somewhat too hard distribution in $J/ψ$ transverse momentum. Correcting the standard KMR distributions for saturation effects at small values of $x$ improves $J/ψ$ rapidity distributions, while taking correction for emissions hidden in the KMR UGDF in the evaluation of $x$ values improves a bit $J/ψ$ transverse momentum distributions. The modifications improve also description of the LHCb $D$-meson data.

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arXiv2017

Prompt inclusive production of $J/ψ$, $ψ'$ and $χ_{c}$ mesons at the LHC in forward directions within the NRQCD $k_t$-factorization approach - search for the onset of gluon saturation

We discuss prompt production of $J/ψ$ mesons in proton-proton collisions at the LHC within NRQCD $k_t$-factorization approach using Kimber-Martin-Ryskin (KMR) unintegrated gluon distributions (UGDF). We include both direct color-singlet production ($g g \to J/ψg$) as well as a feed-down from $χ_c \to J/ψγ$ and $ψ' \to J/ψX$ decays. The production of the decaying mesons ($χ_c$ or $ψ'$) is also calculated within NRQCD $k_t$-factorization approach. The corresponding matrix elements for $g g \to J/ψ$ g, $g g \to ψ'g$ and $g g \to χ_c$ include parameters of the nonrelativistic space wave functions of the quarkonia at $r = 0$, which are taken from potential models in the literature. We get the ratio of the corresponding cross section ratio for $χ_c(2)$-to-$χ_c(1)$ at midrapidities much closer to experimental data than obtained in a recent analysis. Differential distributions in rapidity and transverse momentum of $J/ψ$ and $ψ'$ are calculated and compared with experimental data of the ALICE and LHCb collaborations. We discuss a possible onset of gluon saturation effects in the production of $J/ψ$ and $χ_{c}$ mesons at forward/backward rapidities. We show that it is neccessary to modify the standard KMR UGDF to describe ALICE and LHCb data. A mixed UGDF scenario was proposed. Then we can describe the experimental data for $J/ψ$ production within model uncertainties with color-singlet component only. Therefore our theoretical results leave only a relatively small room for the color-octet contributions.

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arXiv2017

Production of $χ_c$ pairs in $k_T$-factorization

We calculate the production of pairs of $χ_c(J)$ mesons with all possible combinations of $J=0,1,2$. The leading order production mechanism is the crossed-channel gluon exchange in the gluon-gluon fusion reaction. The building blocks are the vertices $g^* g^* \to χ_c(J)$ for off shell gluons. We stick to the color-singlet model and calculate the gluon fusion vertices in the limit of heavy quarks with nonrelativistic motion in the bound state. These vertices are used to construct the $g^* g^* \to χ_c(J_1) χ_c(J_2)$ amplitudes. We then calculate hadron-level cross sections using the $k_T$-factorization approach. In our numerical predictions, we use the KMR-type unintegrated gluon distributions. Several differential distributions at the $pp$ center of mass energy $\sqrt{s} = 8 \, {\rm TeV}$ are shown. The salient feature of the $t$ and $u$-channel gluon exchange are the broad distributions in rapidity difference $Δy$ between $χ_c$ mesons.

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arXiv2017

Photoproduction of $J/ψ$ with dissociation of protons

We present the cross sections for both electromagnetic and diffractive dissociation of protons for semiexclusive production of $J/ψ$ mesons in proton-proton collisions at the LHC. Differential distributions in missing mass ($M_X$), as well as distributions in rapidity and transverse momentum of the $J/ψ$ are calculated for $\sqrt{s} = 7$ TeV and 13 TeV proton proton collisions. We compare the distributions for purely electromagnetic and purely diffractive proton excitations/dissociation. We predict cross sections for electromagnetic and diffractive excitations of similar order of magnitude.

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arXiv2017

Production of two $J/ψ$ mesons in proton-proton collisions at the LHC

We discuss inclusive production of pairs of $J/ψ$ quarkonia. Both leading-order single parton (box) contribution and double-parton contributions are included. In addition we discuss a contribution of higher-order two-gluon exchange and a feed down from double $χ_c$ production. The second two contributions are important for large rapidity distance between the two $J/ψ$ mesons and for relatively large cut-offs on quarkonia transverse momenta. A relation to current experiments is discussed.

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arXiv2017

Inclusive production of vector quarkonia at the LHC

We discuss prompt production of $J/ψ$ mesons in proton-proton collisions at the LHC within NRQCD k$t$-factorization approach using Kimber-Martin-Ryskin (KMR) and Kutak-Stasto (KS) unintegrated gluon distribution (UGDF). We include both direct color-singlet production $gg \to J/ψg$ as well as a feed-down from $χ_{c} \to J/ψγ$ and $ψ' \to J/ψX$. The corresponding matrix elements for $gg \to J/ψ$, $gg \to ψ'$ and $gg \to χ_{c}$ include parameters of the nonrelativistic space wave functions of the quarkonia at $r=0$, which are taken from potential models from the literature. We calculate the ratio of the corresponding cross sections for $χ_{c2}/χ_{c1}$. We compare our results with ATLAS experimental data. Differential distributions in rapidity and transverse momentum of $J/ψ$ and $ψ'$ are calculated and compared to experimental data of the ALICE and LHCb collaborations. We present results for three different values of energy 2.76 TeV, 7 TeV and 13 TeV.

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arXiv2017

Some new aspects of quarkonia production at the LHC

We discuss some different new aspects of $J/ψ$ meson production in exclusive, semi-exclusive and inclusive processes. We finish with a short discussion of double $J/ψ$ production. We point out some new results obtained recently by our group and discuss some open issues.

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arXiv2016

Semiexclusive production of $J/ψ$ mesons in proton-proton collisions with electromagnetic and diffractive dissociation of one of the protons

We calculate the cross sections for both electromagnetic and diffractive dissociation of protons for semiexclusive production of $J/ψ$ mesons in proton-proton collisions at the LHC. Several differential distributions in missing mass ($M_X$), or single-particle variables related exclusively to the $J/ψ$ meson are calculated for $\sqrt{s}$ = 7 TeV as an example. The cross sections and distributions are compared to the cross section of the purely exclusive reaction $p p \to p p J/ψ$. We show the corresponding ratio as a function of $J/ψ$ meson rapidity. We compare the distributions for purely electromagnetic and purely diffractive proton excitations/dissociation. We predict cross sections for electromagnetic and diffractive excitations of similar order of magnitude.

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arXiv2016

Inclusive production of J/$ψ$ and $ψ'$ mesons at the LHC

We discuss the prompt production of $J/ψ$ mesons in proton-proton collisions at the LHC within a NRQCD $k_{t}$-factorization approach using Kimber-Martin-Ryskin (KMR) unintegrated gluon distributions (UGDF). We include both direct color-singlet production ($gg \to J/ψ$g) as well as a feed-down from $χ_{c} \to J/ψγ$ and $ψ' \to J/ψX$. The production of the decaying mesons ($χ_{c}$ or $ψ'$)is also calculated within NRQCD $k_{t}$-factorization. The corresponding matrix elements for $gg \to J/ψ$, $gg \to ψ'$ and $gg \to χ_{c}$ include parameters of the nonrelativistic spatial wave functions of quarkonia at $r=0$, which are taken from potential models from the literature. We get the ratio of the corresponding of the cross sections for $χ_{c}(2)$-to-$χ_{c}(1)$ much closer to experimental data than obtained in recent analyses. Differential distributions in rapidity of $J/ψ$ and $ψ'$ are calculated and compared to experimental data of the ALICE and LHCb collaborations. We discuss possible onset of gluon saturation effects at forward/backward rapidities. One can describe the experimental data for $J/ψ$ production within model uncertainties with color-singlet component only. Therefore our theoretical results leave only a relatively small room for the color-octet contributions.

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arXiv2016

Photoproduction of $J/ψ$ and $Υ$ states in exclusive and proton-dissociative diffractive events

The amplitude for $γp \to V p$, where $V$ is a $J/ψ$ or $Υ$ ground state or excited vector meson, is calculated in a pQCD $k_{T}$-factorization approach. We use this amplitude to predict the cross section for exclusive photoproduction of $J/ψ, ψ', Υ$ mesons in proton-proton collisions. Calculations are performed for a variety of unintegrated gluon distributions, and we compare our results to LHCb data. Here we especially focus on the possibilty of constraining saturation effects. Compared to earlier calculations we include both Dirac and Pauli electromagnetic form factors. We discuss the role of the $Q\bar Q$ light-cone wave functions for differential distributions for ratios such as $σ(ψ')/σ(J/ψ)$. Absorption effects are always taken into account. We also discuss the related diffractive production in proton dissociative events. Here we concentrate on electromagnetic dissociation , which is calculable without additional free parameters. Besides being of interest in their own right, dissociative events constitute an important experimental background to exclusive production.

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arXiv2015

Recent progress in some exclusive and semi-exclusive processes in proton-proton collisions

We present the main results of our recent analyses of exclusive production of vector charmonia ($J/ψ$ and $ψ'$) in $k_t$-factorization approach and for $γγ$ production of charged dilepton pairs in exclusive and semiinclusive processes in a new approach, similar in spirit to $k_t$-factorization. The results for charmonia are compared with recent results of the LHCb collaboration. We include some helicity flip contributions and quantify the effect of absorption correction. The effect of $c \bar c$ wave function is illustrated. We present uncertainties related to $F_2$ structure function which are the main ingredient of the approach. Our results are compared with recent CMS data for dilepton production with lepton isolation cuts imposed.

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arXiv2014

Double parton effects for jets with large rapidity separation

We discuss production of four jets $pp \rightarrow j j j j X$ with at least two jets with large rapidity separation in proton-proton collisions at the LHC through the mechanism of double-parton scattering (DPS). The cross section is calculated in a factorizaed approximation. Each hard subprocess is calculated in LO collinear approximation. The LO pQCD calculations are shown to give a reasonably good descritption of CMS and ATLAS data on inclusive jet production. It is shown that relative contribution of DPS is growing with increasing rapidity distance between the most remote jets, center-of-mass energy and with decreasing (mini)jet transverse momenta. We show also result for angular azimuthal dijet correlations calculated in the framework of $k_t$-factorization approaximation.

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