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Алексеев, Игорь Геннадьевич

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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.

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Алексеев

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Игорь Геннадьевич

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Methods for a blind analysis of isobar data collected by the STAR collaboration
(2021) 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
© 2021, China Science Publishing & Media Ltd. (Science Press), Shanghai Institute of Applied Physics, the Chinese Academy of Sciences, Chinese Nuclear Society and Springer Nature Singapore Pte Ltd.In 2018, the STAR collaboration collected data from 4496Ru+4496Ru and 4096Zr+4096Zr at sNN=200 GeV to search for the presence of the chiral magnetic effect in collisions of nuclei. The isobar collision species alternated frequently between 4496Ru+4496Ru and 4096Zr+4096Zr. In order to conduct blind analyses of studies related to the chiral magnetic effect in these isobar data, STAR developed a three-step blind analysis procedure. Analysts are initially provided a “reference sample” of data, comprised of a mix of events from the two species, the order of which respects time-dependent changes in run conditions. After tuning analysis codes and performing time-dependent quality assurance on the reference sample, analysts are provided a species-blind sample suitable for calculating efficiencies and corrections for individual ≈ 30 -min data-taking runs. For this sample, species-specific information is disguised, but individual output files contain data from a single isobar species. Only run-by-run corrections and code alteration subsequent to these corrections are allowed at this stage. Following these modifications, the “frozen” code is passed over the fully un-blind data, completing the blind analysis. As a check of the feasibility of the blind analysis procedure, analysts completed a “mock data challenge,” analyzing data from Au + Au collisions at sNN=27 GeV, collected in 2018. The Au + Au data were prepared in the same manner intended for the isobar blind data. The details of the blind analysis procedure and results from the mock data challenge are presented.
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Results on total and elastic cross sections in proton–proton collisions at s=200 GeV
(2020) 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
© 2020 The AuthorWe report results on the total and elastic cross sections in proton-proton collisions at s=200 GeV obtained with the Roman Pot setup of the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). The elastic differential cross section was measured in the squared four-momentum transfer range 0.045≤−t≤0.135 GeV2. The value of the exponential slope parameter B of the elastic differential cross section dσ/dt∼e−Bt in the measured −t range was found to be B=14.32±0.09(stat.)−0.28+0.13(syst.) GeV−2. The total cross section σtot, obtained from extrapolation of the dσ/dt to the optical point at −t=0, is σtot=54.67±0.21(stat.)−1.38+1.28(syst.) mb. We also present the values of the elastic cross section σel=10.85±0.03(stat.)−0.41+0.49(syst.) mb, the elastic cross section integrated within the STAR t-range σeldet=4.05±0.01(stat.)−0.17+0.18(syst.) mb, and the inelastic cross section σinel=43.82±0.21(stat.)−1.44+1.37(syst.) mb. The results are compared with the world data.
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Upper limit on the chiral magnetic effect in isobar collisions at the Relativistic Heavy-Ion Collider
(2024) Abdulhamid, M. I.; Aboona, B. E.; Adam, J.; Adams, J. R.; Alekseev, I.; Alpatov, E.; Brandin, A. V.; Kochenda L.; Kraeva, A. Yu.; Kravtsov, P.; Okorokov, V. A.; Parfenov, P.; Povarov, A.; Strikhanov, M.; Taranenko, A.; Vasiliev, A. N.; Алексеев, Игорь Геннадьевич; Алпатов, Егор Вячеславович; Брандин, Андрей Владимирович; Краева, Анна Юрьевна; Окороков, Виталий Алексеевич; Парфенов, Петр Евгеньевич; Поваров, Алексей Сергеевич; Стриханов, Михаил Николаевич; Тараненко, Аркадий Владимирович; Васильев, Александр Николаевич
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Longitudinal double-spin asymmetry for inclusive jet and dijet production in polarized proton collisions at s =200 GeV
(2021) Abdallah, M. S.; Adam, J.; Adamczyk, L.; Adams, J. R.; Alekseev, I.; Brandin, A. V.; Khyzhniak, Y. V.; Kochenda, L.; Kravtsov, P.; Nigmatkulov, G.; Okorokov, V. A.; Parfenov, P.; Strikhanov, M.; Taranenko, A.; Алексеев, Игорь Геннадьевич; Брандин, Андрей Владимирович; Нигматкулов, Григорий Александрович; Окороков, Виталий Алексеевич; Парфенов, Петр Евгеньевич; Стриханов, Михаил Николаевич; Тараненко, Аркадий Владимирович
© 2021 authors. Published by the American Physical Society.We report high-precision measurements of the longitudinal double-spin asymmetry, ALL, for midrapidity inclusive jet and dijet production in polarized pp collisions at a center-of-mass energy of s=200 GeV. The new inclusive jet data are sensitive to the gluon helicity distribution, Δg(x,Q2), for gluon momentum fractions in the range from x≃0.05 to x≃0.5, while the new dijet data provide further constraints on the x dependence of Δg(x,Q2). The results are in good agreement with previous measurements at s=200 GeV and with recent theoretical evaluations of prior world data. Our new results have better precision and thus strengthen the evidence that Δg(x,Q2) is positive for x>0.05.
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Cumulants and correlation functions of net-proton, proton, and antiproton multiplicity distributions in Au plus Au collisions at energies available at the BNL Relativistic Heavy Ion Collider
(2021) Abdallah, M. S.; Adam, J.; Adamczyk, L.; Adams, J. R.; Alekseev, I.; Brandin, A. V.; Khyzhniak, Y. V.; Kochenda, L.; Kravtsov, P.; Nigmatkulov, G.; Okorokov, V. A.; Parfenov, P.; Strikhanov, M.; Taranenko, A.; Алексеев, Игорь Геннадьевич; Брандин, Андрей Владимирович; Нигматкулов, Григорий Александрович; Окороков, Виталий Алексеевич; Парфенов, Петр Евгеньевич; Стриханов, Михаил Николаевич; Тараненко, Аркадий Владимирович
We report a systematic measurement of cumulants, C-n, for net-proton, proton, and antiproton multiplicity distributions, and correlation functions, kappa(n), for proton and antiproton multiplicity distributions up to the fourth order in Au+Au collisions at root s(NN) = 7.7, 11.5, 14.5, 19.6, 27, 39, 54.4, 62.4, and 200 GeV. The C-n and kappa(n) are presented as a function of collision energy, centrality and kinematic acceptance in rapidity, y, and transverse momentum, pT. The data were taken during the first phase of the Beam Energy Scan (BES) program (2010-2017) at the BNL Relativistic Heavy Ion Collider (RHIC) facility. The measurements are carried out at midrapidity (vertical bar y vertical bar < 0.5) and transverse momentum 0.4 < p(T) < 2.0 GeV/c, using the STAR detector at RHIC. We observe a nonmonotonic energy dependence (root s(NN) = 7.7-62.4 GeV) of the net-proton C-4/C-2 with the significance of 3.1 sigma for the 0-5% central Au+Au collisions. This is consistent with the expectations of critical fluctuations in a QCD-inspired model. Thermal and transport model calculations show a monotonic variation with root s(NN). For the multiparticle correlation functions, we observe significant negative values for a two-particle correlation function, kappa(2), of protons and antiprotons, which are mainly due to the effects of baryon number conservation. Furthermore, it is found that the four-particle correlation function, kappa(4), of protons plays a role in determining the energy dependence of proton C-4/C-1 below 19.6 GeV, which cannot be understood by the effect of baryon number conservation.
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Investigation of the linear and mode-coupled flow harmonics in Au+Au collisions at sNN = 200 GeV
(2020) 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
© 2020 The Author(s)Flow harmonics (vn) of the Fourier expansion for the azimuthal distributions of hadrons are commonly employed to quantify the azimuthal anisotropy of particle production relative to the collision symmetry planes. While lower order Fourier coefficients (v2 and v3) are more directly related to the corresponding eccentricities of the initial state, the higher-order flow harmonics (vn>3) can be induced by a mode-coupled response to the lower-order anisotropies, in addition to a linear response to the same-order anisotropies. These higher-order flow harmonics and their linear and mode-coupled contributions can be used to more precisely constrain the initial conditions and the transport properties of the medium in theoretical models. The multiparticle azimuthal cumulant method is used to measure the linear and mode-coupled contributions in the higher-order anisotropic flow, the mode-coupled response coefficients, and the correlations of the event plane angles for charged particles as functions of centrality and transverse momentum in Au+Au collisions at nucleon-nucleon center-of-mass energy sNN= 200 GeV. The results are compared to similar LHC measurements as well as to several viscous hydrodynamic calculations with varying initial conditions.
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Measurement of groomed jet substructure observables in p+p collisions at s=200 GeV with STAR
(2020) 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
© 2020 The Author(s)In this letter, measurements of the shared momentum fraction (zg) and the groomed jet radius (Rg), as defined in the SoftDrop algorithm, are reported in p+p collisions at s=200 GeV collected by the STAR experiment. These substructure observables are differentially measured for jets of varying resolution parameters from R=0.2−0.6 in the transverse momentum range 15
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Measurements of the reactor antineutrinos with the DANSS experiment
(2020) Alekseev, I.; Алексеев, Игорь Геннадьевич
The detector of the reactor antineutrino DANSS is placed on a movable platform below a 3.1 GW industrial reactor of Kalininskaya Nuclear Power Plant. The sensitive volume of the detector is a cubic meter of plastic scintillator assembled from 2500 strips with dual readout by Silicon Photo Multipliers (SiPM) and conventional PMTs (in groups of 50 strips). The detector position provides simultaneously a high neutrino flux and an overburden of about 50 m.w.e., resulting in a high counting rate of inverse beta-decay events and cosmic muons induced background as low as 1.9%. The distance between the reactor core and the detector is changed in a week cycle through three positions 10.7, 11.7 and 12.7 m. This allows systematic-free comparison of the antineutrino spectra measured at different distances by the same detector. This article presents results of the 2.5 year of data collection with more than 2 million of neutrino events collected.
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Measurement of the mass difference and the binding energy of the hypertriton and antihypertriton
(2020) 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
© 2020, The Author(s), under exclusive licence to Springer Nature Limited.According to the CPT theorem, which states that the combined operation of charge conjugation, parity transformation and time reversal must be conserved, particles and their antiparticles should have the same mass and lifetime but opposite charge and magnetic moment. Here, we test CPT symmetry in a nucleus containing a strange quark, more specifically in the hypertriton. This hypernucleus is the lightest one yet discovered and consists of a proton, a neutron and a Λ hyperon. With data recorded by the STAR detector1–3 at the Relativistic Heavy Ion Collider, we measure the Λ hyperon binding energy BΛ for the hypertriton, and find that it differs from the widely used value4 and from predictions5–8, where the hypertriton is treated as a weakly bound system. Our results place stringent constraints on the hyperon–nucleon interaction9,10 and have implications for understanding neutron star interiors, where strange matter may be present11. A precise comparison of the masses of the hypertriton and the antihypertriton allows us to test CPT symmetry in a nucleus with strangeness, and we observe no deviation from the expected exact symmetry.
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Bulk properties of the system formed in Au plus Au collisions at root S-NN=14.5 GeV at the BNL STAR detector
(2020) 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.; Strikhanov, M.; Taranenko, A.; Алексеев, Игорь Геннадьевич; Брандин, Андрей Владимирович; Нигматкулов, Григорий Александрович; Окороков, Виталий Алексеевич; Стриханов, Михаил Николаевич; Тараненко, Аркадий Владимирович
We report systematic measurements of bulk properties of the system created in Au + Au collisions at root S-NN = 14.5 GeV recorded by the STAR detector at the Relativistic Heavy Ion Collider (RHIC). The transverse momentum spectra of pi(+/-), K-+/-, and p((p) over bar) are studied at midrapidity (vertical bar y vertical bar < 0.1) for nine centrality intervals. The centrality, transverse momentum (p(T)), and pseudorapidity (eta) dependence of inclusive charged particle elliptic flow (v(2)), and rapidity-odd charged particles directed flow (v(1)) results near midrapidity are also presented. These measurements are compared with the published results from Au + Au collisions at other energies, and from Pb Pb collisions at root S-NN = 2.76 TeV. The results at root S-NN = 14.5 GeV show similar behavior as established at other energies and fit well in the energy dependence trend. These results are important as the 14.5-GeV energy fills the gap in mu(B), which is of the order of 100 MeV, between root S-NN = 11.5 and 19.6 GeV. Comparisons of the data with UrQMD and AMPT models show poor agreement in general.