2019, Abgrall, N., Aduszkiewicz, A., Andronov, E. V., Anticic, T., Brandin, A., Golosov, O., Kargin, N., Kashirin, E., Morozov, S., Selyuzhenkov, I., Strikhanov, M., Taranenko, A., Брандин, Андрей Владимирович, Голосов, Олег Владимирович, Каргин, Николай Иванович, Стриханов, Михаил Николаевич, Тараненко, Аркадий Владимирович

Measurements of the +/-, K +/-, and proton double differential yields emitted from the surface of the 90-cm-long carbon target (T2K replica) were performed for the incoming 31c protons with the NA61/SHINE spectrometer at the CERN SPS using data collected during 2010 run. The double differential +/- yields were measured with increased precision compared to the previously published NA61/SHINE results, while the K +/- 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.

2019, Adam, J., Adamczyk, L., Adams, J. R., Adkins, J. K., Alekseev, I., Brandin, A, V., Khyzhniak, Y, V., Kochenda, L., Kravtsov, P., Nigmatkulov, G., Okorokov, V. A., Strikhanov, M., Taranenko, A., Алексеев, Игорь Геннадьевич, Брандин, Андрей Владимирович, Нигматкулов, Григорий Александрович, Окороков, Виталий Алексеевич, Стриханов, Михаил Николаевич, Тараненко, Аркадий Владимирович

We report the first measurements of a complete second-order cumulant matrix of net-charge, net-proton, and net-kaon multiplicity distributions for the first phase of the beam energy scan program at the Relativistic Heavy Ion Collider. This includes the centrality and, for the first time, the pseudorapidity window dependence of both diagonal and off-diagonal cumulants in Au+Au collisions at root s(NN) = 7.7-200 GeV. Within the available acceptance of vertical bar eta vertical bar < 0.5, the cumulants grow linearly with the pseudorapidity window. Relative to the corresponding measurements in peripheral collisions, the ratio of off-diagonal over diagonal cumulants in central collisions indicates an excess correlation between net-charge and net-kaon, as well as between net-charge and net-proton. The strength of such excess correlation increases with the collision energy. The correlation between net-proton and net-kaon multiplicity distributions is observed to be negative at root s(NN) = 200 GeV and change to positive at the lowest collision energy. Model calculations based on nonthermal (UrQMD) and thermal (HRG) production of hadrons cannot explain the data. These measurements will help map the quantum chromodynamics phase diagram, constrain hadron resonance gas model calculations and provide new insights on the energy dependence of baryon-strangeness correlations.

2019, Adam, J., Adamczyk, L., Adams, J. R., Adkins, J. K., Alekseev, I., Brandin, A. V., Khyzhniak, Y. V., Kochenda, L., Kravtsov, P., Nigmatkulov, G., Okorokov, V. A., Strikhanov, M., Taranenko, A., Алексеев, Игорь Геннадьевич, Брандин, Андрей Владимирович, Нигматкулов, Григорий Александрович, Окороков, Виталий Алексеевич, Стриханов, Михаил Николаевич, Тараненко, Аркадий Владимирович

We report the first measurement of the inclusive jet and the dijet longitudinal double-spin asymmetries, A(LL) , at midrapidity in polarized pp collisions at a center-of-mass energy root s = 510 GeV. The inclusive jet A(LL) measurement is sensitive to the gluon helicity distribution down to a gluon momentum fraction of x approximate to 0.015, while the dijet measurements, separated into four jet-pair topologies, provide constraints on the x dependence of the gluon polarization. Both results are consistent with previous measurements made at root s = 200 GeV in the overlapping kinematic region, x > 0.05, and show good agreement with predictions from recent next-to-leading order global analyses.

2019, Adam, J., Adamczyk, L., Adams, J. R., Adkins, J. K., Alekseev, I., Brandin, A, V., Kochenda, L., Kravtsov, P., Nigmatkulov, G., Okorokov, V. A., Strikhanov, M., Taranenko, A., Алексеев, Игорь Геннадьевич, Брандин, Андрей Владимирович, Нигматкулов, Григорий Александрович, Окороков, Виталий Алексеевич, Стриханов, Михаил Николаевич, Тараненко, Аркадий Владимирович

We present two-particle P t correlations as a function of event centrality for Au+Au collisions at root s(NN) = 7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV at the Relativistic Heavy Ion Collider using the STAR detector. These results are compared to previous measurements from CERES at the Super Proton Synchrotron and from ALICE at the Large Hadron Collider. The data are compared with UrQMD model calculations and with a model based on a Boltzmann-Langevin approach incorporating effects from thermalization. The relative dynamical correlations for Au+Au collisions at root s(NN) = 200 GeV show a power-law dependence on the number of participant nucleons and agree with the results for Pb+Pb collisions at root s(NN) = 2.76 TeV from ALICE. As the collision energy is lowered from root s(NN )= 200 to 7.7 GeV, the centrality dependence of the relative dynamical correlations departs from the power-law behavior observed at the higher collision energies. In central collisions, the relative dynamical correlations increase with collision energy up to root s(NN) = 200 GeV in contrast to previous measurements that showed little dependence on the collision energy.

2019, Adam, J., Adamczyk, L., Adams, J. R., Adkins, J. K., Alekseev, I., Brandin, A. V., Kochenda, L., Kravtsov, P., Nigmatkulov, G., Okorokov, V. A., Strikhanov, M., Taranenko, A., Алексеев, Игорь Геннадьевич, Брандин, Андрей Владимирович, Нигматкулов, Григорий Александрович, Окороков, Виталий Алексеевич, Стриханов, Михаил Николаевич, Тараненко, Аркадий Владимирович

© 2019 We present the first measurement of the proton–Ω correlation function in heavy-ion collisions for the central (0–40%) and peripheral (40–80%) Au + Au collisions at s NN =200 GeV by the STAR experiment at the Relativistic Heavy-Ion Collider (RHIC). Predictions for the ratio of peripheral collisions to central collisions for the proton–Ω correlation function are sensitive to the presence of a nucleon–Ω bound state. These predictions are based on the proton–Ω interaction extracted from (2+1)-flavor lattice QCD calculations at the physical point. The measured ratio of the proton–Ω correlation function between the peripheral (small system) and central (large system) collisions is less than unity for relative momentum smaller than 40 MeV/c. Comparison of our measured correlation ratio with theoretical calculation slightly favors a proton–Ω bound system with a binding energy of ∼ 27 MeV.

2019, Adam, J., Adamczyk, L., Adams, J. R., Adkins, J. K., Alekseev, I., Brandin, A. V., Khyzhniak, Y. V., Kochenda, L., Kravtsov, P., Nigmatkulov, G., Okorokov, V. A., Strikhanov, M., Taranenko, A., Алексеев, Игорь Геннадьевич, Брандин, Андрей Владимирович, Нигматкулов, Григорий Александрович, Окороков, Виталий Алексеевич, Стриханов, Михаил Николаевич, Тараненко, Аркадий Владимирович

We present measurements of the differential cross sections of inclusive J/psi meson production as a function of transverse momentum (p(T)(J/psi) ) using the mu(+)mu(-) and e(+)e(-) decay channels in proton + proton collisions at center-of-mass energies of 510 and 500 GeV, respectively, recorded by the STAR detector at the Relativistic Heavy Ion Collider. The measurement from the mu(+)mu(-) channel is for 0 < p(T)(J/psi) < 9 GeV/c and rapidity range vertical bar y(J/psi)vertical bar < 0.4, and that from the e(+)e(-) channel is for 4 < p(T)(J/psi) < 20 GeV/c and vertical bar y(J/psi)vertical bar < 1.0. The psi(2S) to J/psi ratio is also measured for 4 < p(T)(meson) < 12 GeV/c through the e(+)e(-) decay channel. Model calculations, which incorporate different approaches toward the J/psi production mechanism, are compared with experimental results and show reasonable agreement within uncertainties.

2019, Adam, J., Adamczyk, L., Adams, J. R., Adkins, J. K., Alekseev, I., Brandin, A, V., Khyzhniak, Y, V., Kochenda, L., Kravtsov, P., Nigmatkulov, G., Okorokov, V. A., Strikhanov, M., Taranenko, A., Алексеев, Игорь Геннадьевич, Брандин, Андрей Владимирович, Нигматкулов, Григорий Александрович, Окороков, Виталий Алексеевич, Стриханов, Михаил Николаевич, Тараненко, Аркадий Владимирович

We report the energy dependence of mid-rapidity (anti-)deuteron production in Au+Au collisions at root s(NN) = 7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV, measured by the STAR experiment at the BNL Relativistic Heavy Ion Collider. The yield of deuterons is found to be well described by the thermal model. The collision energy, centrality, and transverse momentum dependence of the coalescence parameter B-2 are discussed. We find that the values of B-2 for antideuterons are systematically lower than those for deuterons, indicating that the correlation volume of antibaryons is larger than that of baryons at root s(NN) from 19.6 to 39 GeV. In addition, values of B-2 are found to vary with collision energy and show a broad minimum around root s(NN) = 20-40 GeV, which might imply a change of the equation of state of the medium in these collisions.

2019, Adam, J., Adamczyk, L., Adams, J. R., Adkins, J. K., Alekseev, I., Brandin, A. V., Kochenda, L., Kravtsov, P., Nigmatkulov, G., Okorokov, V. A., Strikhanov, M., Taranenko, A., Алексеев, Игорь Геннадьевич, Брандин, Андрей Владимирович, Нигматкулов, Григорий Александрович, Окороков, Виталий Алексеевич, Стриханов, Михаил Николаевич, Тараненко, Аркадий Владимирович

© 2019 authors. Published by the American Physical Society.We report on the first measurements of J/ψ production at very low transverse momentum (pT<0.2 GeV/c) in hadronic Au+Au collisions at sNN=200 GeV and U+U collisions at sNN=193 GeV. Remarkably, the inferred nuclear modification factor of J/ψ at midrapidity in Au+Au (U+U) collisions reaches about 24 (52) for pT<0.05 GeV/c in the 60%-80% collision centrality class. This noteworthy enhancement cannot be explained by hadronic production accompanied by cold and hot medium effects. In addition, the dN/dt distribution of J/ψ for the very low pT range is presented for the first time. The distribution is consistent with that expected from the Au nucleus and shows a hint of interference. Comparison of the measurements to theoretical calculations of coherent production shows that the excess yield can be described reasonably well and reveals a partial disruption of coherent production in semicentral collisions, perhaps due to the violent hadronic interactions. Incorporating theoretical calculations, the results strongly suggest that the dramatic enhancement of J/ψ yield observed at extremely low pT originates from coherent photon-nucleus interactions. In particular, coherently produced J/ψ's in violent hadronic collisions may provide a novel probe of the quark-gluon plasma.

2019, Adam, J., Adamczyk, L., Adams, J. R., Adkins, J. K., Alekseev, I., Brandin, A. V., Khyzhniak, Y. V., Kochenda, L., Kravtsov, P., Nigmatkulov, G., Okorokov, V. A., Strikhanov, M., Taranenko, A., Алексеев, Игорь Геннадьевич, Брандин, Андрей Владимирович, Нигматкулов, Григорий Александрович, Окороков, Виталий Алексеевич, Стриханов, Михаил Николаевич, Тараненко, Аркадий Владимирович

© 2019 American Physical Society.The Λ (Λ̄) hyperon polarization along the beam direction has been measured in Au+Au collisions at sNN=200 GeV, for the first time in heavy-ion collisions. The polarization dependence on the hyperons' emission angle relative to the elliptic flow plane exhibits a second harmonic sine modulation, indicating a quadrupole pattern of the vorticity component along the beam direction, expected due to elliptic flow. The polarization is found to increase in more peripheral collisions, and shows no strong transverse momentum (pT) dependence at pT greater than 1 GeV/c. The magnitude of the signal is about 5 times smaller than those predicted by hydrodynamic and multiphase transport models; the observed phase of the emission angle dependence is also opposite to these model predictions. In contrast, the kinematic vorticity calculations in the blast-wave model tuned to reproduce particle spectra, elliptic flow, and the azimuthal dependence of the Gaussian source radii measured with the Hanbury Brown-Twiss intensity interferometry technique reproduce well the modulation phase measured in the data and capture the centrality and transverse momentum dependence of the polarization signal.

2019, Adam, J., Adamczyk, L., Adams, J. R., Adkins, J. K., Alekseev, I., Brandin, A. V., Kochenda, L., Kravtsov, P., Nigmatkulov, G., Okorokov, V. A., Strikhanov, M., Taranenko, A., Алексеев, Игорь Геннадьевич, Брандин, Андрей Владимирович, Нигматкулов, Григорий Александрович, Окороков, Виталий Алексеевич, Стриханов, Михаил Николаевич, Тараненко, Аркадий Владимирович

The first (v(1)(fluc)), second (v(2)), and third (v(3)) harmonic coefficients of the azimuthal particle distribution at midrapidity are extracted for charged hadrons and studied as a function of transverse momentum (P-T) and mean charged particle multiplicity density < N-ch > in U + U (root s(NN) = 193 GeV), Au + Au, Cu + Au, Cu + Cu, d + Au, and p + Au collisions at, root s(NN) = 200 GeV with the STAR detector. For the same < N-ch >, the v(1)(fluc) and v(3) coefficients are observed to be independent of the collision system, while v(2) exhibits such a scaling only when normalized by the initial-state eccentricity (epsilon(2)). The data also show that ln(v(2)/epsilon(2)) scales linearly with < N-ch >(-1/3). These measurements provide insight into initial-geometry fluctuations and the role of viscous hydrodynamic attenuation on v(n) from small to large collision systems.