Персона: Сомов, Сергей Всеволодович
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Институт ядерной физики и технологий
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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Руководитель научной группы "Лаборатория фундаментальных взаимодействий"
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Сомов
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Сергей Всеволодович
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12 results
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Теперь показываю 1 - 10 из 12
- ПубликацияТолько метаданныеSearch for axion-like particles through nuclear Primakoff production using the GlueX detector(2024) Pybus, J. R.; Kolar, T.; Devkota, B.; Sharp, P.; Somov, S.; Сомов, Сергей Всеволодович
- ПубликацияТолько метаданныеMeasurement of the photon beam asymmetry in γ - p→K+ ς0 at Eγ=8.5 GeV(2020) Adhikari, S.; Ali, A.; Amaryan, M.; Austregesilo, A.; Berdnikov, V. V.; Romanov, D.; Somov, S.; Сомов, Сергей Всеволодович© 2020 American Physical Society. We report measurements of the photon beam asymmetry ς for the reaction γ - p→K+ς0(1193) using the GlueX spectrometer in Hall D at Jefferson Lab. Data were collected by using a linearly polarized photon beam in the energy range of 8.2-8.8 GeV incident on a liquid hydrogen target. The beam asymmetry ς was measured as a function of the Mandelstam variable t, and a single value of ς was extracted for events produced in the u channel. These are the first exclusive measurements of the photon beam asymmetry ς for the reaction in this energy range. For the t channel, the measured beam asymmetry is close to unity over the t range studied, -t=(0.1-1.4)(GeV/c)2, with an average value of ς=1.00±0.05. This agrees with theoretical models that describe the reaction via the natural-parity exchange of the K∗(892) Regge trajectory. A value of ς=0.41±0.09 is obtained for the u channel integrated up to -u=2.0 (GeV/c)2.
- ПубликацияТолько метаданныеFirst Measurement of Near-Threshold J/psi Exclusive Photoproduction off the Proton(2019) Ali, A.; Amaryan, M.; Anassontzis, E. G.; Austregesilo, A.; Berdnikov, V.; Romanov, D.; Somov, S.; Сомов, Сергей ВсеволодовичWe report on the measurement of the gamma p -> J/psi p cross section from E-gamma = 11.8 GeV down to the threshold at 8.2 GeV using a tagged photon beam with the GlueX experiment. We find that the total cross section falls toward the threshold less steeply than expected from two-gluon exchange models. The differential cross section d sigma/dt has an exponential slope of 1.67 +/- 0.39 GeV-2 at 10.7 GeV average energy. The LHCb pentaquark candidates P-c(+) can be produced in the s channel of this reaction. We see no evidence for them and set model-dependent upper limits on their branching fractions B(P-c(+) -> J/psi p) and cross sections sigma(gamma p -> P-c(+)) x B(P-c(+) -> J/psi p).
- ПубликацияТолько метаданныеBeam asymmetry Sigma for the photoproduction of eta and eta mesons at E-gamma=8.8 GeV(2019) Adhikari, S.; Ali, A.; Amaryan, M.; Austregesilo, A.; Berdnikov, V. V.; Romanov, D.; Somov, S.; Сомов, Сергей ВсеволодовичWe report on the measurement of the beam asymmetry Sigma for the reactions (gamma) over right arrowp -> p eta and (gamma) over right arrowp -> p eta' from the GlueX experiment using an 8.2-8.8-GeV linearly polarized tagged photon beam incident on a liquid hydrogen target in Hall D at Jefferson Laboratory. These measurements are made as a function of momentum transfer -t with significantly higher statistical precision than our earlier. measurements and are the first measurements of eta' in this energy range. We compare the results to theoretical predictions based on t-channel quasiparticle exchange. We also compare the ratio of Sigma(eta) to Sigma(eta)' to these models as this ratio is predicted to be sensitive to the amount of s (s) over bar exchange in the production. We find that photoproduction of both eta and eta' is dominated by natural parity exchange with little dependence on -t.
- ПубликацияТолько метаданныеMeasurement of beam asymmetry for π- Δ++ photoproduction on the proton at Eγ=8.5 GeV(2021) Adhikari, S.; Akondi, C. S.; Ali, A.; Amaryan, M.; Berdnikov, V. V.; Romanov, D.; Somov, S.; Williams, M.; Сомов, Сергей Всеволодович© 2021 American Physical Society.We report a measurement of the π- photoproduction beam asymmetry for the reaction γp→π-Δ++ using data from the GlueX experiment in the photon beam energy range 8.2-8.8 GeV. The asymmetry ς is measured as a function of four-momentum transfer t to the Δ++ and compared to phenomenological models. We find that ς varies as a function of t: negative at smaller values and positive at higher values of |t|. The reaction can be described theoretically by t-channel particle exchange requiring pseudoscalar, vector, and tensor intermediaries. In particular, this reaction requires charge exchange, allowing us to probe pion exchange and the significance of higher-order corrections to one-pion exchange at low momentum transfer. Constraining production mechanisms of conventional mesons may aid in the search for and study of unconventional mesons. This is the first measurement of the process at this energy.
- ПубликацияОткрытый доступThe GLUEX beamline and detector(2021) Adhikari, S.; Akondi, C. S.; Al, Ghoul, H.; Ali, A.; Berdnikov, V. V.; Romanov, D.; Somov, S.; Tolstukhin, I.; Сомов, Сергей Всеволодович© 2020The GLUEX experiment at Jefferson Lab has been designed to study photoproduction reactions with a 9-GeV linearly polarized photon beam. The energy and arrival time of beam photons are tagged using a scintillator hodoscope and a scintillating fiber array. The photon flux is determined using a pair spectrometer, while the linear polarization of the photon beam is determined using a polarimeter based on triplet photoproduction. Charged-particle tracks from interactions in the central target are analyzed in a solenoidal field using a central straw-tube drift chamber and six packages of planar chambers with cathode strips and drift wires. Electromagnetic showers are reconstructed in a cylindrical scintillating fiber calorimeter inside the magnet and a lead-glass array downstream. Charged particle identification is achieved by measuring energy loss in the wire chambers and using the flight time of particles between the target and detectors outside the magnet. The signals from all detectors are recorded with flash ADCs and/or pipeline TDCs into memories allowing trigger decisions with a latency of 3.3 μs. The detector operates routinely at trigger rates of 40 kHz and data rates of 600 megabytes per second. We describe the photon beam, the GLUEX detector components, electronics, data-acquisition and monitoring systems, and the performance of the experiment during the first three years of operation.
- ПубликацияОткрытый доступElectromagnetic calorimeters based on scintillating lead tungstate crystals for experiments at Jefferson Lab(2021) Asaturyan, A.; Barbosa, F.; Berdnikov, V.; Chudakov, E.; Somov, S.; Сомов, Сергей Всеволодович© 2021 Elsevier B.V.A new electromagnetic calorimeter consisting of 140 lead tungstate (PbWO4) scintillating crystals was constructed for the PrimEx-η experiment at Jefferson lab. The calorimeter was integrated into the data acquisition and trigger systems of the GlueX detector and used in the experiment to reconstruct Compton scattering events. The experiment started collecting data in the spring of 2019 and acquired about 30% of the required statistics. The calorimeter is a prototype for two PbWO4-based detectors: the Neutral Particle Spectrometer (NPS) and the lead tungstate insert of the Forward CALorimeter (FCAL) of the GlueX detector. The article presents the design and performance of the Compton calorimeter and gives a brief overview of the FCAL and NPS projects.
- ПубликацияОткрытый доступСтримерная камера в экспериментах на ускорителях (конспекты лекций) /Всесоюзная школа по теоретической ядерной физике (6-я сессия: Современное состояние методики эксперимента)(МИФИ, 1975) Сомов, Сергей ВсеволодовичМетодические работы с широкозазорными искровыми камерами, проводимые в 60-х годах в ряде лабораторий, привели к открытию нового способа регистрации следов частиц, состоящего в создании незавершенного (стримерного) разряда на следе. Преимущество нового метода, первоначально состоящее в возможности регистрировать следы частиц независимо от угла их пролета к направлению электрического поля в камере, привлекло внимание многих исследователей и послужило основой создания нового трекового прибора - стримерной камеры. Последующее развитие методики стримерных камер выявило целый ряд свойств этого прибора, делающих его не заменимым во многих физических экспериментах. В настоящее время практически в каждой крупной лаборатории, имеющей ускоритель, работают стримерные камеры.
- ПубликацияТолько метаданныеSearch for photoproduction of axionlike particles at GlueX(2022) Adhikari, S.; Akondi, C. S.; Albrecht, M.; Ali, A.; Romanov, D.; Somov, S.; Сомов, Сергей Всеволодович© 2022 authors. Published by the American Physical Society.We present a search for axionlike particles, a, produced in photon-proton collisions at a center-of-mass energy of approximately 4 GeV, focusing on the scenario where the a-gluon coupling is dominant. The search uses a→γγ and a→π+π-π0 decays, and a data sample corresponding to an integrated luminosity of 168 pb-1 collected with the GlueX detector. The search for a→γγ decays is performed in the mass range of 180
- ПубликацияТолько метаданныеMeasurement of spin density matrix elements in Λ(1520) photoproduction at 8.2-8.8 GeV(2022) Adhikari, S.; Akondi, C. S.; Albrecht, M.; Ali, A.; Romanov, D.; Somov, S.; Сомов, Сергей Всеволодович© 2022 American Physical Society.We report on the measurement of spin density matrix elements of the Λ(1520) in the photoproduction reaction γp→Λ(1520)K+, via its subsequent decay to K-p. The measurement was performed as part of the GlueX experimental program in Hall D at Jefferson Laboratory using a linearly polarized photon beam with Eγ=8.2GeV-8.8GeV. These are the first such measurements in this photon energy range. Results are presented in bins of momentum transfer squared, -(t-t0). We compare the results with a Reggeon exchange model and determine that natural exchange amplitudes are dominant in Λ(1520) photoproduction.