arXiv subjects

Antoni Szczurek

Publications and source records attributed to Antoni Szczurek.

At least 37 records · Page 2Linked to original sources

arXiv2025

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

We discuss prompt production of $J/ψ$ 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 ($g g \to J/ψg$) 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. Differential distributions in rapidity and transverse momentum of $J/ψ$ 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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arXiv2025

Neutron emission from the photon-induced reactions in ultraperipheral ultrarelativistic heavy-ion collisions

The ultraperipheral collisions are the source of various interesting phenomena based on photon-induced reactions. We calculate cross sections for single and any number of n, p, $α$, $γ$-rays in ultraperipheral heavy-ion collision for LHC energies. We analyze the production of a given number of neutrons relevant for a recent ALICE experiment, for $\sqrt{s_{NN}}$ = 5.02~TeV. In our approach, we include both single and multiple photon exchanges as well as the fact that not all photon energies are used in the process of equilibration of the residual nucleus. We propose a simple two-component model in which only part of photon energy $E_γ$ is changed into the excitation energy of the nucleus ($E_{exc} \neq E_γ$) and compare its results with outcomes of HIPSE and EMPIRE codes. The role of high photon energies for small neutron multiplicities is discussed. Emission of a small number of neutrons at high photon energies seems to be crucial to understand the new ALICE data. All effects work in the desired direction, but the description of the cross section of four- and five-neutron emission cross sections from first principles is rather demanding. The estimated emission of charged particles such as protons, deuterons and $α$ is shortly discussed and confronted with very recent ALICE data, obtained with the proton Zero Degree Calorimeter.

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arXiv2024

Light-by-light scattering in ultraperipheral heavy ion collisions -- new possibilities

Light-by-light scattering is a relatively new area of experimental physics. Our recent, theoretical research shows that studying two photon measurements in regions with lower transverse momentum ($p_{t,γ}$) and invariant mass ($M_{γγ}$) allows us to observe not only the main contribution of photon scattering, known as fermionic loops but also mechanisms like the VDM-Regge (double-photon hadronic fluctuation). In addition, diphoton measurements at low diphoton masses are crucial for studies of light meson resonance contributions in $γγ\to γγ$ scattering. We also focus on the interference between different contributions. For future experiments with the ALICE FoCal and ALICE-3 detectors, we have calculated background contamination and have explored possibilities to minimize their impact.

hep-ph↗

arXiv2024

Exclusive diffractive dijets at HERA and EIC using GTMDs

We calculate differential distributions for diffractive production of dijets in $ep\rightarrow e^{'}p\,jet\,jet$ reaction using off diagonal unintegrated gluon distributions, often called GTMDs for brevity. Different models are used. We focus on the contribution to exclusive $q\bar{q}$ dijets. The results of our calculations are compared with the H1 and ZEUS data. Except of one GTMD, our results are below the HERA data points. This is in contrast with recent results where the normalization was adjusted to some selected distributions and no agreement with other observables was checked. We conclude that the calculated cross sections are only a small part of the measured ones which probably contain also processes with pomeron remnant, reggeon exchange, etc. We present also azimuthal correlations between the sum and the difference of dijet transverse momenta. The cuts on transverse momenta of jets generate azimuthal correlations (in this angle) which can be easily misinterpreted as due to so-called elliptic GTMD.

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arXiv2024

Soft-photon theorem for pion-proton elastic scattering revisited

We discuss the reactions $πp \to πp$ and $πp \to πp γ$ from a general quantum field theory (QFT) point of view, describing these reactions in QCD and lowest relevant order of electromagnetism. We consider the pion-proton elastic scattering both off shell and on shell. The on-shell amplitudes for $π^{\pm} p \to π^{\pm} p$ scattering are described by two invariant amplitudes, while the off-shell amplitudes contain eight invariant amplitudes. We study the photon emission amplitudes in the soft-photon limit where the c.m. photon energy $ω\to 0$. The Laurent expansion in $ω$ of the $π^{\pm} p \to π^{\pm} p γ$ amplitudes is considered and the terms of the orders $ω^{-1}$ and $ω^{0}$ are derived. These terms can be expressed by the on-shell invariant amplitudes and their partial derivatives with respect to $s$ and $t$. The pole term $\propto ω^{-1}$ in the amplitudes corresponds to Weinberg's soft-photon theorem and is well known from the literature. We derive the next-to-leading term $\propto ω^{0}$ using only rigorous methods of QFT. We give the relation of the Laurent series for $π^{0} p \to π^{0} p γ$ and Low's soft-photon theorem. Our formulas for the amplitudes in the limit $ω\to 0$ are valid for photon momentum $k$ satisfying $k^{2} \geqslant 0$, $k^{0} = ω\geqslant 0$, that is, for both real and virtual photons. Here we consider a limit where with $ω\to 0$ we have also $k^{2} \to 0$. We discuss the behavior of the corresponding cross-sections for $π^{-} p \to π^{-} p γ$ with respect to $ω$ for $ω\to 0$. We consider cross sections for unpolarized as well as polarized protons in the initial and final states.

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arXiv2024

Production asymmetry of $D$ and ${\bar D}$ mesons in the LHCb fixed target experiment and intrinsic charm in the nucleon

We discuss production of $D^0$ and ${\bar D}^0$ mesons in proton-nucleus collisions in fixed target experiments. We include gluon-gluon fusion, intrinsic charm and perturbative recombination. We compare rapidity and transverse momentum distributions obtained within our approach with recent fixed target LHCb experimental data. All the mechanisms seem important for inclusive production of $D^0 + {\bar D}^0$ mesons. The recombination mechanism seems crucial to understand asymmetry in production of $D^0$ and ${\bar D}^0$ mesons.

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arXiv2024

High-energy $ππ$ scattering without and with photon radiation

We discuss the processes $ππ\to ππ$ and $ππ\to ππγ$ from a general quantum field theory (QFT) point of view. We study the soft-photon limit where the photon energy $ω\to 0$ and where we have the theorems due to F.E. Low and S. Weinberg. We consider for the radiative amplitude the Laurent expansion in $ω$ and calculate the terms of order $ω^{-1}$ and $ω^{0}$. The pole term $\propto ω^{-1}$ is given by Weinberg's soft-photon theorem. Then we calculate the amplitudes for the above reactions for high center-of-mass energies and small momentum transfers, that is, in the soft-diffraction regime using the tensor-pomeron model. We identify places where "anomalous" soft photons could come from. Three soft-photon approximations (SPAs) are introduced. The corresponding SPA results are compared to those obtained from the full tensor-pomeron model for center-of-mass energies $\sqrt{s} = 10$ GeV and 100 GeV. The kinematic regions where the SPAs are a good representation of the full amplitude are determined. Finally we make some remarks on the type of fundamental information one could obtain from high-energy exclusive hadronic reactions without and with soft photon radiation.

hep-ph↗

arXiv2024

The asymmetric intrinsic charm in the nucleon and its implications for the $D^{0}$ production in the LHCb $p\!+\!\!^{20}\!N\!e$ fixed-target experiment

Recent results indicate that charm quarks are intrinsic components of the proton wave function, and that the charm and anticharm distributions for a given value of the Bjorken - $x$ variable can be different. In this paper, we will investigate the impact of this asymmetric intrinsic charm on the production of $D^0$ and ${\bar D}^0$ mesons for fixed target $p \!+ ^{20}\!\!Ne$ collisions at the LHCb. In our calculations, we include the contribution of the gluon-gluon fusion, gluon - charm and recombination processes and assume distinct models for the treatment of the intrinsic charm component. We demonstrate that the presence of an intrinsic charm improves the description of the current data for the rapidity and transverse momentum distributions of $D$ mesons. However, such models are not able to describe the LHCb data for the $D^0$-${\bar D}^0$ asymmetry at large transverse momentum, which point out that the description of the intrinsic charm needs to be improved and/or new effects should be taken into account in the production of heavy mesons at forward rapidities in fixed - target collisions.

hep-ph↗

arXiv2024

Different versions of soft-photon theorems exemplified at leading and next-to-leading terms for pion-pion and pion-proton scattering

We investigate the photon emission in pion-pion and pion-proton scattering in the soft-photon limit where the photon energy $ω\to 0$. The expansions of the $π^{-} π^{0} \to π^{-} π^{0} γ$ and the $π^{\pm} p \to π^{\pm} p γ$ amplitudes, satisfying the energy-momentum relations, to the orders $ω^{-1}$ and $ω^{0}$ are derived. We show that these terms can be expressed completely in terms of the on-shell amplitudes for $π^{-} π^{0} \to π^{-} π^{0}$ and $π^{\pm} p \to π^{\pm} p$, respectively, and their partial derivatives with respect to $s$ and $t$. The~structure term which is non singular for $ω\to 0$ is determined to the order $ω^{0}$ from the gauge-invariance constraint using the generalized Ward identities for pions and the proton. For the reaction $π^{-} π^{0} \to π^{-} π^{0} γ$ we discuss in detail the soft-photon theorems in the versions of both F.E. Low and S. Weinberg. We show that these two versions are different and must not be confounded. Weinberg's version gives the pole term of a Laurent expansion in $ω$ of the amplitude for $π^{-} π^{0} \to π^{-} π^{0} γ$ around the phase-space point of zero radiation. Low's version gives an approximate expression for the above amplitude at a fixed phase-space point, corresponding to non-zero radiation. Clearly, the leading and next-to-leading terms in theses two approaches must be, and are indeed, different. We show their relation. We also discuss the expansions of differential cross sections for $π^{-} π^{0} \to π^{-} π^{0} γ$ with respect to $ω$ for $ω\to 0$.

hep-ph↗

arXiv2024

Light-by-light scattering in ultraperipheral collisions of heavy ions with future FoCal and ALICE 3 detectors

I present possible future studies of light-by-light scattering using FoCal@ALICE and ALICE 3 detectors. Different mechanisms are discussed. The PbPb$\to$PbPb$γγ$ cross section is calculated within equivalent photon approximation in the impact parameter space. Several differential distributions are presented and discussed. We predict cross section in the (mb-b) range for typical ALICE 3 cuts, a few orders of magnitude larger than for the current ATLAS or CMS experiments. We also consider the two-$π^0$ background which can, in principle, be eliminated at the new kinematical range for the ALICE 3 measurements by imposing dedicated cuts on diphoton transverse momentum and$\slash$or so-called vector asymmetry.

hep-ph↗

arXiv2024

Exclusive Bremsstrahlung of One and Two Photons in Proton-Proton Collisions

We discuss the diffractive bremsstrahlung of a single photon in the $pp \to pp γ$ reaction at LHC energies and at forward photon rapidities. We compare the results for our standard approach, based on QFT and the tensor-Pomeron model, with two versions of soft-photon approximations, SPA1 and SPA2, where the radiative amplitudes contain only the leading terms proportional to $ω^{-1}$ (the inverse of the photon energy). SPA1, which does not have the correct energy-momentum relations, performs surprisingly well in the kinematic range considered, namely at very forward photon rapidities and $0.02 < ξ_{1,2} < 0.1$, the relative energy loss of the protons, corresponding to small values of the photon transverse momentum. Azimuthal correlations between outgoing particles are presented. We discuss also the role of the $p p \to p p π^0$ background for single photon production. We discuss also the possibility of a measurement of the $pp \to pp γγ$ reaction. Our predictions can be verified by ATLAS-LHCf combined experiments.

hep-ph↗

arXiv2024

Probing gluon GTMDs of the proton in deep inelastic diffractive dijet production at HERA

We calculate several differential distributions for diffractive dijets production in $e p \to e' {\rm jet \, jet} p$ in the pQCD dipole approach using off diagonal unintegrated gluon distributions (GTMDs). Different models from the literature are used. We concentrate on the contribution from exclusive $q \bar q$ dijets. Results of our calculations are compared to H1 and ZEUS data, including specific experimental cuts in our calculations. In general, except of one GTMD, our results are below the HERA data. The considered mechanism is expected to gives a sizeable contribution to the ZEUS data, while it is negligible in the kinematics of the H1 measurement. This is in contrast to recent results from the literature where the normalization was adjusted to some selected distributions of H1 collaboration and no agreement with other observables was checked. The ZEUS data provide stricter limitations on the GTMDs than the H1 data. We conclude, based on comparison to different observables, that the calculated cross sections are only a small fraction of the measured ones which contain probably also processes with pomeron remnant. Alternatively the experimental data could be explained by inclusion of $q \bar q g$ component. We present also azimuthal correlations between the sum and the difference of dijet transverse momenta. The cuts on transverse momenta of jets generate corresponding azimuthal correlations which can be misidentified as due to elliptic gluon distributions.

hep-ph↗

arXiv2024

$χ_{c2}$ tensor meson transition form factors in the light front approach

We continue our work on the light-front formulation of quarkonium $γ^* γ$ transition form factors, extending the formalism to $J^{PC} = 2^{++}$ tensor meson states. We present an analysis of $γ^* γ\to χ_{c2}$ transition amplitude and the pertinent helicity form factors. Our relativistic formalism is based on the light-front quark-antiquark wave function of the quarkonium. We calculate the two-photon decay width as well as three independent $γ^* γ$ transition form factors for $J_z = 0,1,2$ as a function of photon virtuality $Q^2$. We compare our results for the two-photon decay width to the recently measured ones by the Belle and BES III collaborations. Even when including relativistic corrections, a very small $Γ(λ= 0)/Γ(λ= 2)\sim10^{-3}$ ratio is found which is beyond present experimental precision. We also present the form factors as a function of photon virtuality and compare them to the sparse experimental data on the so-called off-shell width. The formalism presented here can be used for other $2^{++}$ mesons, excited charmonia or bottomonia or even light $q \bar q$-mesons.

hep-ph↗

arXiv2023

Probing proton structure with $c \bar c$ correlations in ultraperipheral $pA$ collisions

We study the exclusive diffractive $c \bar c$ photoproduction in ultraperipheral $pA$ collisions. The formalism makes use of off-diagonal generalizations of the unintegrated gluon distribution, the so-called generalized transverse momentum dependent distributions (GTMDs). We present two different formulations. The first one is based directly on gluon GTMD parametrizations in momentum space. Another option is the calculation of the GTMD as a Fourier transform of the dipole-nucleon scattering amplitude $N(Y,\vec{r}_{\perp},\vec{b}_{\perp})$. The latter approach requires some extra regularization discussed in the paper. Different dipole amplitudes from the literature are used. Compared to previous calculations in the literature, we integrate over the full phase space and therefore cross sections for realistic conditions are obtained. We present distributions in rapidity of $c$ or $\bar c$, transverse momentum of the $c \bar c$ pair, four-momentum transfer squared as well as the azimuthal correlation between a sum and a difference of the $c$ and $\bar c$ transverse momenta. The azimuthal correlations are partially due to the so-called elliptic gluon Wigner distribution. Different models lead to different modulations in the azimuthal angle. The modulations are generally smaller than 5%. They depend on the range of transverse momentum selected for the calculation.

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arXiv2023

Exclusive diffractive bremsstrahlung of one and two photons at forward rapidities: Possibilities for experimental studies in $pp$ collisions at the LHC

We evaluate the cross section for diffractive bremsstrahlung of a single photon in the $pp \to pp γ$ reaction at high energies and at forward photon rapidities. Several differential distributions, for instance, in $y$, $k_{\perp}$ and $ω$, the rapidity, the absolute value of the transverse momentum, and the energy of the photon, respectively, are presented. We compare the results for our standard approach, based on QFT and the tensor-pomeron model, with two versions of soft-photon-approximations, SPA1 and SPA2, where the radiative amplitudes contain only the leading terms proportional to $ω^{-1}$. The SPA1, which does not have the correct energy-momentum relations, performs surprisingly well in the kinematic range considered. We discuss also azimuthal correlations between outgoing particles. The azimuthal distributions are not isotropic and are different for our standard model and SPAs. We discuss also the possibility of a measurement of two-photon-bremsstrahlung in the $pp \to pp γγ$ reaction. In our calculations we impose a cut on the relative energy loss ($0.02 < ξ_{i} < 0.1$, $i = 1,2$) of the protons where measurements by the ATLAS Forward Proton (AFP) detectors are possible. The AFP requirement for both diffractively scattered protons and one forward photon (measured at LHCf) reduces the cross section for $p p \to p p γ$ almost to zero. On the other hand, much less cross-section reduction occurs for $pp \to pp γγ$ when photons are emitted in opposite sides of the ATLAS interaction point and can be measured by two different arms of LHCf. For the SPA1 ansatz we find $σ(pp \to pp γγ) \simeq 0.03$ nb at $\sqrt{s} = 13$ TeV and with the cuts $0.02 < ξ_{i} < 0.1$, $8.5 < y_{3} < 9$, $-9 < y_{4} < -8.5$. Our predictions can be verified by ATLAS and LHCf combined experiments.

hep-ph↗

arXiv2023

Exclusive $η_c$ production by $γ^{*} γ$ interactions in electron-ion collisions

One of the main goals of future electron-ion colliders is to improve our understanding of the structure of hadrons. In this letter, we study the exclusive $η_c$ production by $γ^{*} γ$ interactions in $eA$ collisions and demonstrate that future experimental analysis of this process can be used to improve the description of the $η_c$ transition form factor. The rapidity, transverse momentum and photon virtuality distributions are estimated considering the energy and target configurations expected to be present at the EIC, EicC and LHeC and assuming different predictions for the light-front wave function of the $η_c$ meson. Our results indicate that the electron-ion colliders can be considered an alternative to providing supplementary data to those obtained in $e^- e^+$ colliders.

hep-ph↗

arXiv2023

Central exclusive diffractive production of a single photon in high-energy proton-proton collisions within the tensor-Pomeron approach

We discuss central-exclusive production (CEP) of photons via different fusion processes in the reaction $pp \to pp γ$ at high energies, available at RHIC and LHC, within the tensor-pomeron model. We consider two types of processes, the photoproduction contribution via the photon-pomeron and photon-reggeon fusion reactions, and the purely diffractive contribution via the reggeon-pomeron and odderon-pomeron fusion reactions. We present predictions for the measurements of photons at midrapidity, $|{\rm y}| < 2.5$, and at relatively low transverse momentum, $0.1~{\rm GeV} < k_{\perp} < 1~{\rm GeV}$. To check the main results of our study the measurement of the outgoing protons is not necessary. This is of relevance, e.g., for the present version of the ALICE detector at the LHC. Several differential distributions, for instance, in ${\rm y}$, $k_{\perp}$ and $ω$, the rapidity, the absolute value of the transverse momentum, and the energy of the photon, respectively, are presented. We show that the photoproduction is an important process in the kinematic region specified above. There it gives a much larger cross section than diffractive bremsstrahlung. This is remarkable as the CEP cross section is of order $α_{\rm em}^{3}$ whereas the bremsstrahlung one is only of order $α_{\rm em}$. On the other hand, the soft-photon bremsstrahlung where the basic $pp \to pp$ reaction is due to strong interaction diffraction is more important than CEP in the forward rapidity range, $|{\rm y}| > 4$, and/or at very low $k_{\perp}$. We leave it as a challenge for the planned ALICE 3 experiment at the LHC to study these two contributions to soft photon production in $pp$ collisions. This could shed new light on the so called ``soft photon puzzle'' in hadron-hadron collisions.

hep-ph↗

arXiv2023

The Tensor Pomeron and Low-x Deeply Virtual Compton Scattering

The two-tensor-pomeron model is applied to deeply virtual Compton scattering (DVCS) on a proton. A good description of the DVCS HERA data at small Bjorken-$x$ is achieved due to a sizeable interference of soft and hard pomeron contributions. We present two fits which differ somewhat in the strength of the hard pomeron contribution. We describe, in the same framework, both the low $Q^{2}$ and high $Q^{2}$ regimes and the transition between them. We find that the soft-pomeron contribution is considerable up to $Q^{2} \sim 20$ GeV$^{2}$. The reggeon exchange term is particularly relevant for describing the scattering of a real photon on a proton measured at lower $γp$ energies at FNAL. We find that the ratio of $γ^{*} p \to γp$ cross-sections for longitudinally and transversely polarized virtual photons strongly increases with $t$. Our findings may be checked in future lepton-nucleon scattering experiments in the low-$x$ regime, for instance, at a future Electron-Ion Collider (EIC) at the BNL and LHeC at the LHC.

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