Персона:
Алексеев, Игорь Геннадьевич

Научные группы

Научная группа

Организационные подразделения

Организационная единица

Цель ИЯФиТ и стратегия развития - создание и развитие научно-образовательного центра мирового уровня в области ядерной физики и технологий, радиационного материаловедения, физики элементарных частиц, астрофизики и космофизики.

Фамилия

Алексеев

Имя

Игорь Геннадьевич

Полная страница элемента

Результаты поиска

Теперь показываю 1 - 10 из 38

Только метаданные
Global and local polarization of A hyperons in Au plus Au collisions at 200 GeV from STAR
(2019) Niida, 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
New results on global polarization of A hyperons in Au+Au collisions at root s(NN) = 200 GeV reveal non-zero signal on the order of a few tenths of a percent. Compared with lower energy results, the current measurement shows that the polarization decreases at higher collision energy, the trend being well reproduced by theoretical calculations. The polarization is found to be larger in more peripheral collisions, as well as in the in-plane than in the out-of-plane direction. The signal seems to depend on the asymmetry between positive and negative charge in each event, which may indicate an influence of the axial current induced by the magnetic field. In addition, the first measurement of a local polarization along the beam direction was performed. The results show a quadrupole modulation relative to the second-order event plane, as expected from the elliptic flow.
Только метаданные
Upsilon measurements in Au plus Au collisions at root S-NN=200 GeV with the STAR experiment
(2019) Wang, P. F.; 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 the latest measurements of Upsilon production in Au+Au collisions at root S-NN = 200 GeV via both di-muon and di-electron decay channels by the STAR experiment at RHIC. With the addition of the 2016 data set to those taken in 2011 and 2014, the precision of Upsilon measurements is significantly improved compared to previous preliminary results, especially for the excited Upsilon states. The nuclear modification factors for the ground and excited Upsilon states are shown as a functions of transverse momentum or centrality, and are compared to results from the LHC as well as to theoretical calculations.
Только метаданные
Measurements of open charm production in Au plus Au collisions at root s(NN)=200 GeV with the STAR experiment at RHIC
(2019) Radhakrishnan, 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 in these proceedings on the measurements of collision centrality and transverse momentum (p(T)) dependences of the Lambda(+/-)(c) production in Au+Au collisions at root s(NN) = 200 GeV, using the STAR Heavy Flavor Tracker (HFT). The Lambda(+/-)(c) signal significance is greatly improved with the addition of the high-statistics data set collected in 2016 and the use of a supervised machine learning method for topological reconstruction of the decay vertices. The measured Lambda(+/-)(c)/D-0 ratio shows a significant enhancement compared to the PYTHIA prediction for p+p collisions, across the measured p(T) range. We also report on the updated measurements of D-0 nuclear modification factors R-AA and R-CP using the 2014 data with the HFT. The measured D-0 R-AA in central collisions is lower than unity across the p(T) interval of the measurement. The D-0 yields show strong suppression at high p(T) (> 6 GeV/c) in central collisions, consistent with that of light flavor hadrons. The c (c) over bar production cross section per binary nucleon collision at midrapidity in Au+Au collisions at 200 GeV is extracted based on the various charm hadron measurements by STAR. It is observed that while the charm hadrochemistry is significantly modified in Au+Au collisions compared to p+p collisions, the c (c) over bar production cross section at midrapidity remains consistent between Au+Au and p+p collisions.
Только метаданные
The STAR BES-II and Forward Rapidity Physics and Upgrades
(2019) Yang, Q.; 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 second phase of the Beam Energy Scan at RHIC, BES-II, is scheduled to start in 2019 and will explore the high baryon density region of the QCD phase diagram with precision measurements. The detector upgrades will enhance some of the key measurements by extending STAR's kinematic reach, like the kurtosis of net-protons distribution which could pinpoint the position of a critical point. The upgrades currently under way comprise: the replacement of the inner TPC sectors, the Event Plane Detector (EPD) and the end-cap TOR Building on these upgrades STAR is planning to further enhance its detector capabilities by installing a Forward Calorimeter System (FCS) integrating an electromagnetic and hadronic calorimeter and a Forward Tracking System (FTS) combining 3 Silicon mini-strip disks and 4 Small-Strip Thin Gap Chamber (sTGC) wheels. The forward upgrades are motivated by studying the initial state of nucleons and nuclei and the exploration of cold QCD physics in the very high and low x regions. This contribution will highlight these upgrades and some of the physics opportunities that they allow.
Только метаданные
Observation of Excess J /ψ Yield at Very Low Transverse Momenta in Au+Au Collisions at sNN =200 GeV and U+ U Collisions at sNN =193 GeV
(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.
Только метаданные
Collision-energy dependence of second-order off-diagonal and diagonal cumulants of net-charge, net-proton, and net-kaon multiplicity distributions in Au plus Au collisions
(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.
Только метаданные
Measurements of the transverse-momentum-dependent cross sections of J/psi production at mid-rapidity in proton plus proton collisions at root s=510 and 500 GeV with the STAR detector
(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.
Только метаданные
Polarization of Λ (Λ ) Hyperons along the Beam Direction in Au+Au Collisions at sNN =200 GeV
(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.
Только метаданные
Longitudinal double-spin asymmetry for inclusive jet and dijet production in pp collisions at root s=510 GeV
(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.
Только метаданные
Beam energy dependence of (anti-)deuteron production in Au plus Au collisions at the BNL Relativistic Heavy Ion Collider
(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.