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A. Kurepin

Publications and source records attributed to A. Kurepin.

At least 55 records · Page 3Linked to original sources

Measurements of total production cross sections for $π^{+}$+C, $π^{+}$+Al, $K^{+}$+C, and $K^{+}$+Al at 60 GeV/c and $π^{+}$+C and $π^{+}$+Al at 31 GeV/c

This paper presents several measurements of total production cross sections and total inelastic cross sections for the following reactions: $π^{+}$+C, $π^{+}$+Al, $K^{+}$+C, $K^{+}$+Al at 60 GeV/c, $π^{+}$+C and $π^{+}$+Al at 31 GeV/c . The measurements were made using the NA61/SHINE spectrometer at the CERN SPS. Comparisons with previous measurements are given and good agreement is seen. These interaction cross sections measurements are a key ingredient for neutrino flux prediction from the reinteractions of secondary hadrons in current and future accelerator-based long-baseline neutrino experiments.

hep-ex↗

Measurements of production and inelastic cross sections for $\mbox{p}+\mbox{C}$, $\mbox{p}+\mbox{Be}$, and $\mbox{p}+\mbox{Al}$ at 60 GeV/$c$ and $\mbox{p}+\mbox{C}$ and $\mbox{p}+\mbox{Be}$ at 120 GeV/$c$

This paper presents measurements of production cross sections and inelastic cross sections for the following reactions: 60 GeV/$c$ protons with C, Be, Al targets and 120 GeV/$c$ protons with C and Be targets. The analysis was performed using the NA61/SHINE spectrometer at the CERN SPS. First measurements were obtained using protons at 120 GeV/$c$, while the results for protons at 60 GeV/$c$ were compared with previously published measurements. These interaction cross section measurements are critical inputs for neutrino flux prediction in current and future accelerator-based long-baseline neutrino experiments.

hep-ex↗

Measurement of $ϕ$ meson production in p+p interactions at 40, 80 and 158 GeV/c with the NA61/SHINE spectrometer at the CERN SPS

Results on $ϕ$ meson production in inelastic p+p collisions at CERN SPS energies are presented. They are derived from data collected by the NA61/SHINE fixed target experiment, by means of invariant mass spectra fits in the $ϕ\to K^+K^-$ decay channel. They include the first ever measured double differential spectra of $ϕ$ mesons as a function of rapidity $y$ and transverse momentum $p_T$ for proton beam momenta of 80 GeV/c and 158 GeV/c, as well as single differential spectra of $y$ or $p_T$ for beam momentum of 40 GeV/c. The corresponding total $ϕ$ yields per inelastic p+p event are obtained. These results are compared with existing data on $ϕ$ meson production in p+p collisions. The comparison shows consistency but superior accuracy of the present measurements. The emission of $ϕ$ mesons in p+p reactions is confronted with that occurring in Pb+Pb collisions, and the experimental results are compared with model predictions. It appears that none of the considered models can properly describe all the experimental observables.

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Identical pion intensity interferometry in central Au+Au collisions at 1.23A GeV

We investigate identical pion HBT intensity interferometry for central Au+Au collisions at 1.23A GeV. High-statistics $π^-π^-$ and $π^+π^+$ data are measured with HADES at SIS18/GSI. The radius parameters, derived from the correlation function depending on relative momenta in the longitudinal-comoving system and parametrized as three-dimensional Gaussian distribution, are studied as function of transverse momentum. A substantial charge-sign difference of the source radii is found, particularly pronounced at low transverse momentum. The extracted Coulomb-corrected source parameters agree well with a smooth extrapolation of the center-of-mass energy dependence established at higher energies, extending the corresponding excitation functions down towards a very low energy. Our data would thus rather disfavour any strong energy dependence of the radius parameters in the low energy region.

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Spin Physics with a fixed-target experiment at the LHC

The multi-TeV proton and ion beams of the LHC would allow for the most energetic fixed-target experiment ever. In particular, $pp$, $p$d and $p$A collisions could be performed at $\sqrt{s_{NN}}$ = 115~GeV, as well as Pb$p$ and PbA collisions at $\sqrt{s_{NN}}$ = 72~GeV, in a parasitic way by making use of the already existing LHCb and ALICE detectors in fixed-target mode. This would offer the possibility to carry out a ground-breaking physics program, to study the nucleon and nuclear structure at high $x$, the spin content of the nucleon and the phases of the nuclear matter from a new rapidity viewpoint. In this talk I focus on the spin physics axis of the full program developed so far by the AFTER@LHC study group.

hep-ph↗

Measurements of $π^{\pm}$, $K^{\pm}$ and proton yields from the surface of the T2K replica target for incoming 31 GeV/c protons with the NA61/SHINE spectrometer at the CERN SPS

Measurements of the $π^{\pm}$, $K^{\pm}$, and proton double differential yields emitted from the surface of the 90-cm-long carbon target (T2K replica) were performed for the incoming 31 GeV/c protons with the NA61/SHINE spectrometer at the CERN SPS using data collected during 2010 run. The double differential $π^{\pm}$ yields were measured with increased precision compared to the previously published NA61/SHINE results, while the $K^{\pm}$ and proton yields were obtained for the first time. A strategy for dealing with the dependence of the results on the incoming proton beam profile is proposed. The purpose of these measurements is to reduce significantly the (anti)neutrino flux uncertainty in the T2K long-baseline neutrino experiment by constraining the production of (anti)neutrino ancestors coming from the T2K target.

hep-ex↗

High luminosity fixed-target experiment at the LHC

By extracting the beam with a bent crystal or by using an internal gas target, the multi-TeV proton and lead LHC beams allow one to perform the most energetic fixed-target experiments ever and to study $pp$, $p$d and $p$A collisions at $\sqrt{s_{NN}}=115$ GeV and Pb$p$ and PbA collisions at $\sqrt{s_{NN}}=72$ GeV with high precision and modern detection techniques. Such studies would address open questions in the domain of the nucleon and nucleus partonic structure at high-$x$, quark-gluon plasma and, by using longitudinally or transversally polarised targets, spin physics. In this paper, we will review the technical solutions to obtain a high-luminosity fixed-target experiment at the LHC and will discuss their possible implementations with the ALICE and LHCb detectors.

hep-ex↗

Probing the high-x content of the nuclei in the fixed-target mode at the LHC

Using the LHCb and ALICE detectors in the fixed-target mode at the LHC offers unprecedented possibilities to study the quark, gluon and heavy-quark content of the proton and nuclei in the poorly known region of the high-momentum fractions. We review our projections for studies of Drell-Yan, charm, beauty and quarkonium production with both detector set-ups used with various nuclear targets and the LHC proton beams. Based on this, we show the expected improvement in the determination of the quark, charm and gluon proton and nuclear PDFs as well as discuss the implication for a better understanding of the cold-nuclear-matter effects in hard-probe production in proton-nucleus collisions.

hep-ex↗

Determination of centrality in nucleus-nucleus collisions on the MPD/NICA installation

Measurement of the number of spectators in nucleus-nucleus collisions could be used to determine the number of participant nucleons involved in the interaction, i.e. get information about collision centrality. However, at energies of the NICA collider, energy resolution of the forward hadron calorimeter is insufficient for separation amplitude corresponding to different number of spectators. Uncertainty in the number of spectators leads to a large error in determining centrality. For central events inaccuracy in determining the collision parameter is about 40%, for peripheral ones, no better than 30% at a beam energy of 2.5 AGeV. The multiplicity scintillator detector will allow to obtain more accurate data. A method is proposed for determining the centrality, taking into account the real MPD installation geometry.

hep-ex↗

Sub-threshold production of K^{0}_{s} mesons and Λ hyperons in Au(1.23A GeV)+Au

We present first data on sub-threshold production of K0 s mesons and Λ hyperons in Au+Au collisions at $\sqrt{s_{NN}}$ = 2.4 GeV. We observe an universal scaling of hadrons containing strangeness, independent of their corresponding production thresholds. Comparing the yields, their scaling, and the shapes of the rapidity and the pt spectra to state-of-the-art transport model (UrQMD, HSD, IQMD) predictions, we find that none of the latter can simultaneously describe all observables with reasonable \c{hi}2 values.

nucl-ex↗

Strong absorption of hadrons with hidden and open strangeness in nuclear matter

We present the first observation of K- and ϕabsorption within nuclear matter by means of π- -induced reactions on C and W targets at an incident beam momentum of 1.7 GeV/c studied with HADES at SIS18/GSI. The double ratio (K-/K+)W / (K-/K+)C is found to be 0.319 \pm 0.009(stat)+0.014-0.012 (syst) indicating a larger absorption of K- in heavier targets as compared to lighter ones. The measured ϕ/K- ratios in π-+C and π^- +W reactions within the HADES acceptance are found to be equal to $0.55 \pm 0.03(stat)+0.06-0.07$ (syst) and to $0.63 \pm 0.05(stat)-0.11+0.11$ (syst), respectively. The similar ratios measured in the two different reactions demonstrate for the first time experimentally that the dynamics of the ϕmeson in nuclear medium is strongly coupled to the K- dynamics. The large difference in the ϕproduction off C and W nuclei is discussed in terms of a strong \phiN in-medium coupling.

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A fixed-target programme at the LHC for heavy-ion, hadron, spin and astroparticle physics: AFTER@LHC

Thanks to its multi-TeV LHC proton and lead beams, the LHC complex allows one to perform the most energetic fixed-target experiments ever and to study with high precision pp, pd and pA collisions at sqrt(s_NN) = 115 GeV and Pbp and PbA collisions at sqrt(s_NN) = 72 GeV. We present a selection of feasibility studies for the production of quarkonia, open heavy-flavor mesons as well as light-flavor hadrons in pA and PbA collisions using the LHCb and ALICE detectors in a fixed-target mode.

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Centrality determination of Au+Au collisions at 1.23A GeV with HADES

The centrality determination for Au+Au collisions at 1.23A GeV, as measured with HADES at the GSI-SIS18, is described. In order to extract collision geometry related quantities, such as the average impact parameter or number of participating nucleons, a Glauber Monte Carlo approach is employed. For the application of this model to collisions at this relatively low centre-of-mass energy of $\sqrt{s_{\mathrm{NN}}} = 2.42$ GeV special investigations were performed. As a result a well defined procedure to determine centrality classes for ongoing analyses of heavy-ion data is established.

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Physics perspectives with AFTER@LHC (A Fixed Target ExpeRiment at LHC)

AFTER@LHC is an ambitious fixed-target project in order to address open questions in the domain of proton and neutron spins, Quark Gluon Plasma and high-$x$ physics, at the highest energy ever reached in the fixed-target mode. Indeed, thanks to the highly energetic 7 TeV proton and 2.76 A.TeV lead LHC beams, center-of-mass energies as large as $\sqrt{s_{NN}}$ = 115 GeV in pp/pA and $\sqrt{s_{NN}}$ = 72 GeV in AA can be reached, corresponding to an uncharted energy domain between SPS and RHIC. We report two main ways of performing fixed-target collisions at the LHC, both allowing for the usage of one of the existing LHC experiments. In these proceedings, after discussing the projected luminosities considered for one year of data taking at the LHC, we will present a selection of projections for light and heavy-flavour production.

hep-ex↗

LHC Forward Physics

The goal of this report is to give a comprehensive overview of the rich field of forward physics, with a special attention to the topics that can be studied at the LHC. The report starts presenting a selection of the Monte Carlo simulation tools currently available, chapter 2, then enters the rich phenomenology of QCD at low, chapter 3, and high, chapter 4, momentum transfer, while the unique scattering conditions of central exclusive production are analyzed in chapter 5. The last two experimental topics, Cosmic Ray and Heavy Ion physics are presented in the chapter 6 and 7 respectively. Chapter 8 is dedicated to the BFKL dynamics, multiparton interactions, and saturation. The report ends with an overview of the forward detectors at LHC. Each chapter is correlated with a comprehensive bibliography, attempting to provide to the interested reader with a wide opportunity for further studies.

hep-ph↗

Deep sub-threshold ϕ production and implications for the K+/K- freeze-out in Au+Au collisions

We present data on charged kaons (K+-) and ϕ mesons in Au(1.23A GeV)+Au collisions. It is the first simultaneous measurement of K and ϕ mesons in central heavy-ion collisions below a kinetic beam energy of 10A GeV. The ϕ/K- multiplicity ratio is found to be surprisingly high with a value of 0.52 +- 0.16 and shows no dependence on the centrality of the collision. Consequently, the different slopes of the K+ and K- transverse-mass spectra can be explained solely by feed- down, which substantially softens the spectra of K- mesons. Hence, in contrast to the commonly adapted argumentation in literature, the different slopes do not necessarily imply diverging freeze- out temperatures of K+ and K- mesons caused by different couplings to baryons.

nucl-ex↗

$Σ^0$ production in proton nucleus collisions near threshold

The production of $Σ^{0}$ baryons in the nuclear reaction p (3.5 GeV) + Nb (corresponding to $\sqrt{s_{NN}}=3.18$ GeV) is studied with the detector set-up HADES at GSI, Darmstadt. $Σ^{0}$s were identified via the decay $Σ^{0} \rightarrow Λγ$ with subsequent decays $Λ\rightarrow p π^{-}$ in coincidence with a $e^{+}e^{-}$ pair from either external ($γ\rightarrow e^{+} e^{-}$) or internal (Dalitz decay $γ^{*}\rightarrow e^{+} e^{-}$) gamma conversions. The differential $Σ^0$ cross section integrated over the detector acceptance, i.e. the rapidity interval $0.5 < y < 1.1$, has been extracted as $Δσ_{Σ^{0}} = 2.3 \pm (0.2)^{stat} \pm \left(^{+0.6}_{-0.6}\right)^{sys} \pm (0.2)^{norm}$ mb, yielding the inclusive production cross section in full phase space $σ^{total}_{Σ^{0}} = 5.8 \pm (0.5)^{stat} \pm \left(^{+1.4}_{-1.4}\right)^{sys} \pm (0.6)^{norm} \pm (1.7)^{extrapol}$ mb by averaging over different extrapolation methods. The $Λ_{all}$/$Σ^{0}$ ratio within the HADES acceptance is equal to 2.3 $\pm$ $(0.2)^{stat}$ $\pm$ $(^{+0.6}_{-0.6})^{sys}$. The obtained rapidity and momentum distributions are compared to transport model calculations. The $Σ^{0}$ yield agrees with the statistical model of particle production in nuclear reactions.

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