2019, Liu, P., Adam, J., Adamczyk, L., Adams, J. R., 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 transverse momentum spectra of triton with STAR Beam Energy Scan data from Au+Au collisions at root N-SS = 7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, 200 GeV in the centrality classes 0 - 10%, 10 - 20%, 20 - 40% and 40 - 80% are reported. The centrality dependence of the coalescence parameter B-3 of triton and the collision energy dependence of the relative neutron density fluctuation are then calculated. The results indicate that the B-3 decreases from peripheral to central collisions and the neutron density fluctuation shows a non-monotonic collision energy dependence with a peak around collision energy of 20-30 GeV. In addition, we report details about the reconstruction method of H-3(Lambda) via H-3(Lambda) -> 4 He-3 + pi(-) and H-3(Lambda) -> + p + pi(-) using high statistics data in Au+Au collisions at root S-NN = 200 GeV collected in 2014 and 2016 with the Heavy Flavor Tracker.

2019, Aduszkiewicz, A., Andronov, E. V., Anticic, T., Babkin, V., Brandin, A., Golosov, O., Kargin, N. I., 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

© 2019 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/" Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Precise knowledge of hadron production rates in the generation of neutrino beams is necessary for accelerator-based neutrino experiments to achieve their physics goals. NA61/SHINE, a large-acceptance hadron spectrometer, has recorded hadron+nucleus interactions relevant to ongoing and future long-baseline neutrino experiments at Fermi National Accelerator Laboratory. This paper presents three analyses of interactions of 60 GeV/c π+ with thin, fixed carbon and beryllium targets. Integrated production and inelastic cross sections were measured for both of these reactions. In an analysis of strange, neutral hadron production, differential production multiplicities of KS0, Λ and Λ were measured. Lastly, in an analysis of charged hadron production, differential production multiplicities of π+, π-, K+, K- A nd protons were measured. These measurements will enable long-baseline neutrino experiments to better constrain predictions of their neutrino flux in order to achieve better precision on their neutrino cross section and oscillation measurements.

2019, Nonaka, T., Adam, J., Adamczyk, L., Adams, J. R., 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 recent results on the cumulants of net-particle distributions in Au+Au collisions at the STAR experiment. Beam energy dependence of net-Lambda cumulants and off-diagonal cumulants are measured. These measurements provide additional constraints on the chemical freeze-out conditions. The sixth-order cumulant of net-charge and net-proton distributions is measured at root s(NN) = 200 GeV to search for the signal of the crossover phase transition. Finally, an unfolding technique is developed and applied to the net-proton distributions at 19.6 GeV to account for the non-binomial effects of the detector.

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, Magdy, N., Adam, J., Adamczyk, L., Adams, J. R., 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

New measurements of elliptic flow from two- and four-particle correlations are used to investigate flow fluctuations in collisions of U+U at root s(NN) = 193 GeV, Cu+Au at root s(NN) = 200 GeV and Au+Au at several beam energies. These measurements highlight the dependence of these fluctuations on the event shape, system size and beam energy and indicate a dominant role for initial-state-driven fluctuations. These measurements could provide further constraints for initial-state models, as well as for precision extraction of the temperature-dependent specific shear viscosity eta/s(T).

2019, Huang, S. L., Adam, J., Adamczyk, L., Adams, J. R., 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

New STAR measurements of two- and four-particle (c(2){4}) azimuthal angle correlations are reported for p+Au collisions at 200 GeV and d+Au collisions from 19.6 to 200 GeV. A negative c(2){4), consistent with collective anisotropic flow, is observed in high multiplicity d+Au events at 62.4 and 200 GeV where the statistical significance of the data allows an analysis. A template fitting method, employed to subtract non-flow contributions to the two-particle correlations, allows the extraction of the anisotropy coefficients (v(2)) for these systems at their respective energies. The v(2) results for different energies show a common dependence on the charged particle multiplicity density << dN(ch)/d eta >>, which provide important insight on the nature of collective behavior in small collision systems.

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, Singha, S., Adam, J., Adamczyk, L., Adams, J. R., 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 report on the first evidence for a non-zero rapidity-odd directed flow (nu(1)) for D-0 and (D-0) over bar mesons in 10-80% centrality Au+Au collisions at root S-NN = 200 GeV measured with the STAR detector at RHIC. The slope of the v1 rapidity dependence (d nu(1)/dy) averaged over D-0 and (D-0) over bar mesons is -0.081 +/- 0.021 +/- 0.017, while that of charged kaons is -0.0030 +/- 0.0001 +/- 0.0002, suggesting significantly larger slope for the D-0 mesons. Models indicate that the large d nu(1)/dy of D-0 mesons is sensitive to the initially tilted source. We also present a new measurement of the D-0 meson elliptic flow (v(2)) as a function of transverse momentum (P-T) in Au+Au collisions at root S-NN = 200 GeV with an improved precision with respect to the previously published results. The D-0 nu(2) results are compared to those of light-flavor hadrons to test the number-of-constituent-quark (NCQ) scaling. Both the nu(1) and nu(2) results are compared to recent hydrodynamic and transport model calculations.

2019, Shou, Q. Y., Adam, J., Adamczyk, L., Adams, J. R., 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 chiral magnetic wave (CMW) has been theorized to propagate in the Quark-Gluon Plasma formed in high-energy heavy-ion collisions. It could cause a finite electric quadrupole moment of the collision system, and may be observed as a dependence of elliptic flow, v(2), on the asymmetry between positively and negatively charged hadrons, A(ch). However, non-CMW mechanisms, such as local charge conservation (LCC) and hydrodynamics with isospin effect, could also contribute to the experimental observations. Here we present the STAR measurements of elliptic flow v(2) and triangular flow v(3) of charged pions, along with v(2) of charged kaons and protons, as functions of A(ch) in Au+Au collisions root S-NN = 200 GeV. The slope parameters of Delta v(2)(A(ch)) and Delta v(3)(Ach) are reported and compared to investigate the LCC background. The similarity between pion and kaon slopes suggests that the hydrodynamics is not the dominant mechanism. The difference between the normalized Delta v(2) and Delta v(3) slopes, together with the small slopes in p+Au and d+Au collisions at root S-NN = 200 GeV, suggest that the CMW picture remains a viable interpretation at RHIC.

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.