arXiv subjects

Antoni Szczurek

Publications and source records attributed to Antoni Szczurek.

At least 145 records · Page 8Linked to original sources

arXiv2017

Rescattering effects in jet-gap-jet processes

We discuss the process of colour-singlet parton-parton scattering, which in hadron-hadron collision can lead to production of jet events, where a rapidity gap between the jets is present. The dynamics of the process is calculated within LL BFKL approximation. Using Pythia MC generator, hadronic shapes of jet-gap-jet events are studied, in particular the distributions of the rapidity gap size resulting from the jet formation processes. Using Pythia's modelling of multiple parton interactions, the rescattering effects are simulated. It is shown how these effects influence the gap size distributions. The kinematic dependence of the gap survival probability is discussed.

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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.

hep-ph↗

arXiv2017

New theoretical results in ultrarelativistic ultraperipheral lead-lead collisions

We study dilepton, proton-antiproton and diphoton production in ultraperipheral lead-lead collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 and 5.5 TeV. The nuclear calculations are based on equivalent photon approximation in the impact parameter space. For correct description of the $γγ\to p\bar{p} $ Belle data we include the proton-exchange, the $f_2(1270)$ and $f_2(1950)$ s-channel exchanges, as well as the handbag mechanism. For four muon production, we take into account electromagnetic (two-photon) double-scattering production and direct $γγ$ production of four muons in one scattering. The cross sections for elementary $γγ\to γγ$ subprocess are calculated including three different mechanisms: box diagrams with leptons and quarks in the loops, a VDM-Regge contribution with virtual intermediate hadronic excitations of the photons and the two-gluon exchange contribution. We find that the cross section for elastic $γγ$ scattering could be measured in the lead-lead collisions for the diphoton invariant mass up to $W_{γγ} \approx$ 15 - 20 GeV. Our Standard Model predictions are compared with a recent ATLAS experimental result. We discuss results for PbPb$\to$PbPb$μ^+μ^-μ^+μ^-$, PbPb$\to$PbPb$e^+e^-e^+e^-$, PbPb$\to$PbPb$p\bar{p}$ and PbPb$\to$PbPb$γγ$ reactions at LHC energy.

hep-ph↗

arXiv2017

Triple parton scattering effects in $D$-meson production at the LHC

We study triple-parton scattering effects in open charm production in proton-proton collisions at the LHC. Predictions for one, two and three $c\bar c$ pairs production are given for $\sqrt{s}= 7$ TeV and $\sqrt{s}= 13$ TeV. Quite large cross sections, of the order of milibarns, for the triple-parton scattering mechanism are obtained. We suggest a measurement of three $D^{0}$ or three $\bar{D^{0}}$ mesons by the LHCb collaboration. The predicted visible cross sections are of the order of a few nanobarns. The counting rates including $D^{0} \to K^{-}π^{+}$ branching fractions are also given. We predict that at $\sqrt{s}= 13$ TeV a few thousands of events of triple-$D^{0}$ production can be observed by the LHCb collaboration.

hep-ph↗

arXiv2017

Associated production of $D$-mesons with jets at the LHC

We present several differential distributions for the associated production of charm and dijets. Both single-parton scattering (SPS) and double-parton scattering (DPS) contributions are calculated in the $k_T$-factorization approach. We have found regions of the phase space where the SPS contribution is negligible compared to the DPS one. The distribution in transverse momentum of charmed mesons as well as azimuthal correlations ($D^0\mathrm{\textit{-jet}}$, $D^0 \overline{D^0}$) can be used for experimental identification of the DPS effects.

hep-ph↗

arXiv2017

Single-diffractive dijet production at high energies within the $k_t$ -factorization approach

We discuss single-diffractive production of dijets. The cross section is calculated for the first time in the $k_t$-factorization approach, neglecting transverse momentum of the pomeron. We use Kimber-Martin-Ryskin unintegrated parton (gluon, quark, antiquark) distributions (UPDF) both in the proton as well as in the pomeron or subleading reggeon. The UPDFs are calculated based on conventional MMHT2014nlo PDFs in the proton and H1 collaboration diffractive PDFs used previously in the analysis of diffractive structure function and dijets at HERA. We try to describe the existing data from Tevatron and make detailed predictions for possible LHC measurements.

hep-ph↗

arXiv2017

Exclusive diffractive production of hadrons in $pp$ collisions

We discuss central exclusive diffractive dihadron production in proton-proton collisions at high energies. The calculation is based on a tensor pomeron model and the amplitudes for the processes are formulated in an effective field-theoretic approach. We include a purely diffractive dipion continuum, and the scalar and tensor resonances decaying into the $π^{+} π^{-}$ pairs as well as the photoproduction contributions ($ρ^{0}$, Drell-Söding). We discuss how two pomerons couple to tensor meson $f_{2}(1270)$ and the interference effects of the scalar and tensor resonances and the dipion continuum. The theoretical results are compared with existing CDF and CMS experimental data. We discuss also the Drell-Hiida-Deck type mechanism with centrally produced $ρ^{0}$ meson associated with a very forward/backward $πN$ system. For the $pp \to pp π^{+} π^{-} π^{+} π^{-}$ reaction we consider both the $σσ$ and $ρρ$ contributions as well as the triple Regge exchange mechanism. Predictions for planned or being carried out experiments (STAR, ALICE, ATLAS, CMS) are presented. We show the influence of the experimental cuts on the integrated cross section and on various differential distributions for outgoing particles.

hep-ph↗

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.

hep-ph↗

arXiv2017

Single- and double-scattering production of four muons in ultraperipheral PbPb collisions at the Large Hadron Collider

We discuss production of two $μ^+μ^-$ pairs in ultraperipheral ultrarelativistic heavy ion collisions at the LHC. We take into account electromagnetic (two-photon) double-scattering production and for a first time direct $γγ$ production of four muons in one scattering. We study the unexplored process $γγ\to μ^+μ^-μ^+μ^-$. We present predictions for total and differential cross sections. Measurable nuclear cross sections are obtained and corresponding differential distributions and counting rates are presented.

hep-ph↗

arXiv2017

Mapping the dominant regions of the phase space associated with $c \bar c$ production relevant for the Prompt Atmospheric Neutrino Flux

We present a detailed mapping of the dominant kinematical domains contributing to the prompt atmospheric neutrino flux at high neutrino energies by studying its sensitivity to the cuts on several kinematical variables crucial for charm production in cosmic ray scattering in the atmosphere. This includes the maximal center-of-mass energy for proton-proton scattering, the longitudinal momentum fractions of partons in the projectile (cosmic ray) and target (nucleus of the atmosphere), the Feynman $x_F$ variable and the transverse momentum of charm quark/antiquark. We find that the production of neutrinos with energies larger than $E_ν >$ 10$^7$ GeV is particularly sensitive to the center-of-mass energies larger than the ones at the LHC and to the longitudinal momentum fractions in the projectile 10$^{-8}$ $< x <$ 10$^{-5}$. Clearly, these are regions where we do not control the parton, in particular gluon, densities. We also analyse the characteristic theoretical uncertainties in the charm production cross section coming from its QCD modelling. The precision data on the prompt atmospheric neutrino flux can efficiently constrain the mechanism of heavy quark production and underlying QCD dynamics in kinematical ranges beyond the reach of the current collider measurements.

hep-ph↗

arXiv2017

Double-parton scattering effects in associated production of charm mesons and dijets at the LHC

We calculate several differential distributions for the production of charm and dijets. Both single-parton scattering (SPS) and double-parton scattering (DPS) contributions are calculated in the $k_T$-factorization approach. The Kimber-Martin-Ryskin unintegrated parton distributions are used in our calculations. Relatively low cuts on jet transverse momenta are imposed to enhance the double-parton scattering mechanism contribution. We find dominance of the DPS contribution over the SPS one. We have found regions of the phase space where the SPS contribution is negligible compared to the DPS contribution. The distribution in transverse momentum of charm quark/antiquark or charmed mesons can be used to observe transition from the dominance of DPS at low transvsverse momenta to the dominance of SPS at large transverse momenta. Very distinct azimuthal correlation patterns (for $c \bar{c}$, $c\mathrm{\textit{-jet}}$, $\mathrm{\textit{jet-jet}}$, $D^0\mathrm{\textit{-jet}}$, $D^0 D^0$) are predicted as a result of the competition of the SPS and DPS mechanisms.

hep-ph↗

arXiv2017

The role of meson exchanges in light-by-light scattering

We discuss the role of meson exchange mechanisms in $γγ\to γγ$ scattering. Several pseudoscalar ($π^0$, $η$, $η'(958)$, $η_c(1S)$, $η_c(2S)$), scalar ($f_{0}(500)$, $f_0(980)$, $a_0(980)$, $f_0(1370)$, $χ_{c0}(1P)$) and tensor ($f_2(1270)$, $a_2(1320)$, $f_2'(1525)$, $f_2(1565)$, $a_2(1700)$) mesons are taken into account. We consider not only $s$-channel but also for the first time $t$- and $u$-channel meson exchange amplitudes corrected for off-shell effects including vertex form factors. We find that, depending on not well known vertex form factors, the meson exchange amplitudes interfere among themselves and could interfere with fermion-box amplitudes and modify the resulting cross sections. The meson contributions are shown as a function of collision energy as well as angular distributions are presented. Interesting interference effects separately for light pseudoscalar, scalar and tensor meson groups are discussed. The meson exchange contributions may be potentially important in the context of a measurement performed recently in ultraperipheral collisions of heavy ions by the ATLAS collaboration. The light-by-light interactions could be studied in future in electron-positron collisions by the Belle II at SuperKEKB accelerator.

hep-ph↗

arXiv2017

Single-diffractive production of dijets within the $k_t$-factorization approach

We discuss single-diffractive production of dijets. The cross section is calculated within the resolved pomeron picture, for the first time in the $k_t$-factorization approach, neglecting transverse momentum of the pomeron. We use Kimber-Martin-Ryskin unintegrated parton (gluon, quark, antiquark) distributions (UPDF) both in the proton as well as in the pomeron or subleading reggeon. The UPDFs are calculated based on conventional MMHT2014nlo PDFs in the proton and H1 collaboration diffractive PDFs used previously in the analysis of diffractive structure function and dijets at HERA. For comparison we present results of calculations performed within collinear-factorization approach. Our results remaind those obtained in the NLO approach. The calculation is (must be) supplemented by the so-called gap survival factor which may, in general, depend on kinematical variables. We try to describe the existing data from Tevatron and make detailed predictions for possible LHC measurements. Several differential distributions are calculated. The $\overline{E}_T$, $\overlineη$ and $x_{\bar p}$ distributions are compared with the Tevatron data. A reasonable agreement is obtained for the first two distributions. The last one requires to introduce a gap survival factor which depends on kinematical variables. We discuss how the phenomenological dependence on one kinematical variable may influence dependence on other variables such as ${\overline E}_T$ and ${\overline η}$. Several distributions for the LHC are shown.

hep-ph↗

arXiv2017

Multi-parton interactions and rapidity gap survival probability in jet-gap-jet processes

We discuss an application of dynamical multi-parton interaction model, tuned to measurements of underlying event topology, for a description of destroying rapidity gaps in the jet-gap-jet processes at the LHC. We concentrate on the dynamical origin of the mechanism of destroying the rapidity gap. The cross section for jet-gap-jet is calculated within LL BFKL approximation. We discuss the topology of final states without and with the MPI effects. We discuss some examples of selected kinematical situations (fixed jet rapidities and transverse momenta) as distributions averaged over the dynamics of the jet-gap-jet scattering. The color-singlet ladder exchange amplitude for the partonic subprocess is implemented into the \textsc{Pythia 8} generator, which is then used for hadronisation and for the simulation of the MPI effects. Several differential distributions are shown and discussed. We present the ratio of cross section calculated with and without MPI effects as a function of rapidity gap in between the jets.

hep-ph↗

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.

hep-ph↗

arXiv2017

Can the triple-parton scattering be observed in open charm meson production at the LHC?

We investigate whether the triple-parton scattering effects can be observed in open charm production in proton-proton collisions at the LHC. We use so-called factorized Ansatz for calculations of hard multiple-parton interactions. The numerical results for each parton interaction are obtained within the $k_{T}$-factorization approach. Predictions for one, two and three $c\bar c$ pairs production are given for $\sqrt{s}= 7$ TeV and $\sqrt{s}= 13$ TeV. Quite large cross sections, of the order of milibarns, for the triple-parton scattering mechanism are obtained. We suggest a measurement of three $D^{0}$ mesons or three $\bar{D^{0}}$ antimesons by the LHCb collaboration. Confronting our results with recent LHCb experimental data for single and double $D^{0}$ (or $\bar{D^{0}}$) meson production we present our predictions for triple meson final state: $D^{0}D^{0}D^{0}$ or $\bar{D^{0}}\bar{D^{0}}\bar{D^{0}}$. We present cross sections for the LHCb fiducial volume as well as distributions for $D^{0}$ meson transverse momentum and three-$D^{0}$ meson invariant mass. The predicted visible cross sections, including the detector acceptance, hadronization effects and $c \to D^{0}$ branching fraction, is of the order of a few nanobarns. The counting rates including $D^{0} \to K^{-}π^{+}$ branching fractions are given for known or expected integrated luminosities.

hep-ph↗

arXiv2017

Triple Regge exchange mechanisms of four-pion continuum production in the $pp \to pp π^{+}π^{-}π^{+}π^{-}$ reaction

We consider exclusive multi-peripheral production of four charged pions in proton-proton collisions at high energies with simultaneous exchange of three pomerons/reggeons. The amplitude(s) for the genuine $2 \to 6$ process are written in the Regge approach. The calculation is performed with the help of the GenEx Monte Carlo code. Some corrections at low invariant masses in the two-body subsystems are necessary for application of the Regge formalism. We estimate the corresponding cross section and present differential distributions in rapidity, transverse momenta and two- and four-pion invariant masses. The cross section and the distributions depend on the value of the cut-off parameter of a form factor correcting amplitudes for off-shellness of $t$-channel pions. Rather large cross section is found for the whole phase space ($σ\sim$ 1-5 $μ$b, including absorption corrections). Relatively large four-pion invariant masses are populated in the considered diffractive mechanism compared to other mechanisms discussed so far in the context of four-pion production. We investigate whether the triple Regge exchange processes could be identified with the existing LHC detectors. We consider the case of ATLAS and ALICE cuts. The ATLAS (or CMS) has better chances to identify the process in the region of large invariant masses $M_{4 π} > 10$ GeV. In the case of the ALICE experiment the considered mechanism competes with other mechanisms (production of $σσ$, $ρρ$ pairs or single resonances) and cannot be unambiguously identified.

hep-ph↗