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Mariola Klusek-Gawenda

Publications and source records attributed to Mariola Klusek-Gawenda.

35 records · Page 2Linked to original sources
arXiv2016

Electromagnetic effects on meson production: a new tool for studying the space-time evolution of heavy ion collisions

We review our studies of spectator-induced electromagnetic (EM) effects on the emission of charged mesons in the final state of ultrarelativistic heavy ion collisions. We argue that these effects offer sensitivity to the distance $d_E$ between the charged meson formation zone at freeze-out and the spectator system. As such, they can serve as an independent, new tool to probe the space-time and longitudinal evolution of the system created in the collision. As a phenomenological application for this tool in the context of resonance production and decay, we obtain a first estimate of the time of pion emission from EM effects. This we compare to existing HBT data.

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arXiv2016

Light-by-light scattering in UPC at the LHC

We discuss diphoton semi(exclusive) production in ultraperipheral $PbPb$ collisions at energy of $\sqrt{s_{NN}}=$ 5.5 TeV (LHC). The nuclear calculations are based on equivalent photon approximation in the impact parameter space. The cross sections for elementary $γγ\to γγ$ subprocess are calculated including two different mechanisms: box diagrams with leptons and quarks in the loops and a VDM-Regge contribution with virtual intermediate hadronic excitations of the photons. We got relatively high cross sections in $PbPb$ collisions ($306$ nb). This opens a possibility to study the $γγ\to γγ$ (quasi)elastic scattering at the LHC. We find that the cross section for elastic $γγ$ scattering could be measured in the lead-lead collisions for the diphoton invariant mass $W_{γγ} \approx 15-20$ GeV.

hep-ph↗
arXiv2016

Two-gluon exchange contribution to elastic $γγ\to γγ$ scattering and production of two-photons in ultraperipheral ultrarelativistic heavy ion and proton-proton collisions

We discuss the two-gluon exchange contribution (formally three-loops) to elastic photon-photon scattering in the high-energy approximation. The elastic $γγ\to γγ$ amplitude is given in the impact-factor representation for all helicity configurations and finite quark masses. We discuss the importance of including the charm quark, which contribution, due to interference, can enhance the cross section considerably. We investigate the contribution to the $γγ\to γγ$ amplitude from the soft region, by studying its dependence on nonperturbative gluon mass. Helicity-flip contributions are shown to be much smaller than helicity-conserving ones. We identify region(s) of phase space where the two-gluon exchange contribution becomes important ingredient compared to box and nonperturbative VDM-Regge mechanisms considered in the literature. Consequences for the $A A \to A A γγ$ reaction are discussed. Several differential distributions are shown. A feasibility study to observe the effect of two-gluon exchange is presented. We perform a similar analysis for the $p p \to p p γγ$ reaction. Only by imposing severe cuts on $M_{γγ}$ and a narrow window on photon transverse momenta the two gluon contribution becomes comparable to the box contribution but the corresponding cross section is rather small.

hep-ph↗
arXiv2016

Light-by-light scattering in ultraperipheral heavy-ion collisions at the LHC

We present cross sections for diphoton production in (semi)exclusive $PbPb$ collisions, relevant for the LHC. The calculation is based on equivalent photon approximation in the impact parameter space. The cross sections for elementary elastic scattering $γγ\to γγ$ subprocess are calculated including two mechanisms: box diagrams with leptons and quarks in the loops and a mechanism based on vector-meson dominance (VDM-Regge) model with virtual intermediate vector-like excitations of the photons. We get measureable cross sections in $PbPb$ collisions. We present many interesting differential distributions which could be measured by the ALICE, CMS or ATLAS Collaborations at the LHC. We study whether a separation of box and VDM-Regge contributions is possible. We find that the cross section for elastic $γγ$ scattering could be measured in the heavy-ion collisions for subprocess energies smaller than $W_{γγ} \approx 15-20$~GeV.

hep-ph↗
arXiv2016

Light-by-light scattering in ultraperipheral PbPb collisions at the Large Hadron Collider

We calculate cross sections for diphoton production in (semi)exclusive $PbPb$ collisions, relevant for the LHC. The calculation is based on equivalent photon approximation in the impact parameter space. The cross sections for elementary $γγ\to γγ$ subprocess are calculated including two different mechanisms. We take into account box diagrams with leptons and quarks in the loops. In addition, we consider a vector-meson dominance (VDM-Regge) contribution with virtual intermediate hadronic (vector-like) excitations of the photons. We get much higher cross sections in $PbPb$ collisions than in earlier calculation from the literature. This opens a possibility to study the $γγ\to γγ$ (quasi)elastic scattering at the LHC. We present many interesting differential distributions which could be measured by the ALICE, CMS or ATLAS Collaborations at the LHC. We study whether a separation or identification of different components (boxes, VDM-Regge) is possible. We find that the cross section for elastic $γγ$ scattering could be measured in the heavy-ion collisions for subprocess energies smaller than $W_{γγ} \approx 15-20$ GeV.

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arXiv2015

Double-scattering mechanism of production of two $ρ^0$ mesons in ultraperipheral, ultrarelativistic heavy ion collisions

We study, for the first time, differential distributions for two $ρ^0$ meson production in exclusive ultraperipheral, ultrarelativistic heavy ion collisions via a double-scattering mechanism. The calculations are done in the impact parameter space. The cross section for $γA \to ρ^0 A$ is parametrized based on an existing model. Smearing of $ρ^0$ masses is taken into account. The results of calculations for single and double-$ρ^0$ production are compared to experimental data at the RHIC and LHC energies. The mechanism considered gives a significant contribution to the $AA \to AA π^+π^-π^+π^-$ reaction. Some observables related to charged pions are presented too. We compare results of our calculations with the STAR collaboration results for four charged pion production.

hep-ph↗
arXiv2013

Electromagnetic excitation of nuclei and neutron evaporation in ultrarelativistic ultraperipheral heavy ion collisions

We present a new approach for calculating electromagnetic excitation of nuclei as well as probabilities of emission and distributions of neutrons from decays of excited nuclear systems for ultrarelativistic, ultraperipheral heavy ion collisions. Excitation functions for $γ$ + Pb $\to$ Pb$^*$ are parametrized using physics-motivated components: excitation of giant resonances, quasi-deuteron absorption mechanism, excitation of nucleon resonances as well as high-energy dissociation of protons and neutrons. Neutron emission (up to 10 neutrons) from low-energy excitations of $^{208}$Pb is modelled in terms of the Hauser-Feshbach formalism. The probabilities of a given number of neutrons are calculated as a function of excitation energy in a Monte-Carlo code GEMINI. These functions are parametrized by smooth analytical functions. The results are compared to appropriate data for the $γ$ Pb $\to$ Pb$^*$ $\to$ k n reaction. As an example the approach is used for calculating electromagnetic excitation in UPC processes. Both single photon and double photon excitations are included and discussed. Topological cross sections with a given number of neutrons in forward and backward directions are calculated in the calculation at the LHC energies. Excitation functions are presented. The results of calculation are compared with SPS and more recent ALICE experimental data and good agreement is achieved.

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arXiv2013

Double-scattering mechanism in exclusive $A A \to A A ρ^0 ρ^0$ reaction at ultrarelativistic collisions

We calculate, for the first time, differential distributions for double $ρ^0$ meson production in exclusive ultraperipheral, ultrarelativistic collisions via a double scattering mechanism. The calculations are done in impact parameter space. The cross section for $γA \to ρ^0 A$ is parametrized based on an existing calculation. Smearing of $ρ^0$ masses is taken into account. The results of our calculations are compared at the RHIC energy to the contribution of the two-photon mechanism discussed previously in the literature. The cross section for the double scattering mechanism is found to be an order of magnitude larger at $M_{ρρ} <$ 2 GeV and more than two orders of magnitude at $M_{ρρ} >$ 3 GeV, than that for the photon-photon mechanism. Compared to the two-photon mechanism the double scattering mechanism populates somewhat larger $ρ^0 ρ^0$ invariant masses and larger rapidity distances between the two $ρ^0$ mesons and gives a significant contribution to the $A A \to A A π^+ π^- π^+ π^-$ reaction. Some observables related to charged pions are presented too. We compare the results of our calculation with the STAR collaboration results on four charged pion production. While the shape in invariant mass of the four-pion system is very similar to the measured one, the predicted cross section constitutes only 20% of the measured one. We discuss a possibility of identifying the double scattering mechanism at the LHC.

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arXiv2013

Strong and Electromagnetic Forces in Heavy Ion Collisions

The interplay between the strong and electromagnetic force in high energy nucleus-nucleus collisions was studied experimentally and theoretically in our earlier works. This effect appeared to result in very large distortions in spectra of charged pions produced in the collision. It was also found to bring new, independent information on the space-time evolution of the non-perturbative process of particle production. In this paper, we present our new results on the influence of the spectator-induced electromagnetic force on spectra of charged particles produced in two different Pb-induced reactions. For the first time, we also address the topic of p+A collisions in view of obtaining information about their centrality and nuclear break-up, both subjects being of importance in the context of the new p+A data collected at the LHC.

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arXiv2013

Studying the Interplay of Strong and Electromagnetic Forces in Heavy Ion Collisions with NICA

In the following we stress the advantages of the NICA research programme in the context of studying the spectator-induced electromagnetic phenomena present in proton-nucleus and heavy ion collisions. We point at the specific interest of using these phenomena as a new, independent source of information on the space-time evolution of the reaction and of the non-perturbative process of particle production. We propose an extended series of measurements of well-defined observables to be performed in different types of nuclear reactions and in the whole range of collision energies available to NICA. We expect these measurements to bring very valuable new insight into the mechanism of non-perturbative strong interactions, complementary to the studies made at the SPS at CERN, RHIC at BNL, and the LHC.

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arXiv2012

Exclusive production of $π^+π^-$ and $π^0π^0$ pairs in photon-photon and in ultrarelativistic heavy ion collisions

The $γγ\toππ$ reactions are discussed. To describe those processes, we include dipion continuum, resonances, high-energy pion-pion rescatterings, $ρ$ meson exchange and pQCD Brodsky-Lepage mechanisms. The cross section for the production of pion pairs in photon-photon collisions in peripheral heavy ion collisions is calculated with the help of Equivalent Photon Approximaption (EPA) in the impact parameter space. We show predictions at $\sqrt{s_{NN}}=3.5$ TeV which could be measured e.g. by the ALICE collaboration at the LHC.

hep-ph↗
arXiv2011

Exclusive production of pion pairs with large invariant mass in nucleus-nucleus collisions

The cross section for exclusive $π^+π^-$ and $π^0π^0$ meson pairs production in peripheral ultrarelativistic heavy-ion collisions is calculated at the energy available at the CERN Large Hadron Collider, i.e., $\sqrt{s_{NN}}=3.5$ TeV. The cross section for elementary $γγ\toππ$ process is calculated with the help of the pQCD Brodsky-Lepage approach with the distribution amplitude used recently to describe the pion transition form factor measured by the BaBar Collaboration.

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arXiv2011

Exclusive production of large invariant mass pion pairs in ultraperipheral ultrarelativistic heavy ion collisions

The cross section for exclusive production of $π^+ π^-$ and $π^0 π^0$ meson pairs in ultrarelativistic heavy ion collisions is calculated for LHC energy $\sqrt{s_{NN}} =$ 3.5 TeV taking into account photon-photon mechanism. We concentrate on the production of large two-pion invariant masses where the mechanism of the elementary $γγ\to ππ$ process is not fully understood. In order to include a size of nuclei we perform calculation in the impact-parameter equivalent photon approximation (EPA). Realistic charge densities are used to calculate charged form factor of $^{208}$Pb nucleus and to generate photon fluxes associated with ultrarelativistic heavy ions. Sizeable cross sections are obtained that can be measured at LHC. The cross section for elementary $γγ\to ππ$ is calculated in the framework of pQCD Brodsky-Lepage (BL) mechanism with the distribution amplitude used to descibe recent data of the BABAR collaboration on pion transition form factor, using hand-bag mechanism advocated to describe recent Belle data as well as $t$ and $u$-channel meson/reggeon exchanges. We present distributions in two-pion invariant mass as well as the pion pair rapidity for the nuclear process.

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arXiv2011

Exclusive muon-pair productions in ultrarelativistic heavy-ion collisions: Realistic nucleus charge form factor and differential distributions

The cross sections for exclusive muon pair production in nucleus - nucleus collisions are calculated and several differential distributions are shown. Realistic (Fourier transform of charge density) charge form factors of nuclei are used and the corresponding results are compared with the cross sections calculated with monopole form factor often used in the literature and discussed recently in the context of higher-order QED corrections. Absorption effects are discussed and quantified. The cross sections obtained with realistic form factors are significantly smaller than those obtained with the monopole form factor. The effect is bigger for large muon rapidities and/or large muon transverse momenta. The predictions for the STAR and PHENIX collaboration measurements at RHIC as well as the ALICE and CMS collaborations at LHC are presented.

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arXiv2010

Double -- photon exclusive processes with heavy quark -- heavy antiquark pairs in high-energy Pb-Pb collisions at LHC

The cross section for exclusive heavy quark and heavy antiquark pair ($Q \bar Q$) production in peripheral ultrarelativistic heavy ion collisions is calculated for the LHC energy $\sqrt{s_{NN}}$ = 5.5 TeV. Here we consider only processes with photon--photon interactions and omit diffractive contributions. We present results in the impact parameter equivalent photon approximation (EPA) and compare some of them with results obtained by exact calculations of the Feynman diagrams in the momentum space. We include both $Q \bar Q$, $Q \bar Q g$ and $Q \bar Q q \bar q$ final states as well as photon single-resolved components. Realistic charge densities in nuclei were taken in the calculation. The different components give contributions of the same order of magnitude to the nuclear cross section. The cross sections found here are smaller than those for the diffractive photon-pomeron mechanism and larger than diffractive pomeron-pomeron discussed in the literature.

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arXiv2010

Exclusive production of $ρ^0 ρ^0$ pairs in ultrarelativistic heavy ion collisions

We disuss exclusive electromagnetic production of two neutral $ρ^0$~mesons and show the predictions for the $AA \to AA ρ^0 ρ^0$ reactions for gold-gold collisions at the energy of $\sqrt{s}$ = 200 GeV (RHIC) and for lead-lead collisions at the energy of $\sqrt{s}$ = 5.5 TeV (LHC). The elementary cross section is calculated with the help of the vector-dominance-model (VDM)-Regge approach which usually very well describes the experimental data at large $γγ$ energy. The low-energy $γγ\to ρ^0 ρ^0$ cross section is parametrized. The cross section for nuclear process is calculated by means of the equivalent photon approximation (EPA). We compare the results with realistic charge density with the results for monopole form factor.

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