Yazar "Alekseev, M." seçeneğine göre listele
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Öğe Measurement of proton electromagnetic form factors in the time-like region using initial state radiation at BESIII(Elsevier, 2021) Ablikim, M.; Achasov, M. N.; Adlarson, P.; Ahmed, S.; Albrecht, M.; Alekseev, M.; Çetin, Serkant AliThe electromagnetic process e(+)e(-) -> p (p) over bar over bar is studied with the initial-state-radiation technique using 7.5 fb(-1) of data collected by the BESIII experiment at seven energy points from 3.773 to 4.600 GeV. The Born cross section and the effective form factor of the proton are measured from the production threshold to 3.0 GeV/c(2) using the p (p) over bar over bar invariant-mass spectrum. The ratio of electric and magnetic form factors of the proton is determined from the analysis of the proton-helicity angular distribution. (C) 2021 The Author. Published by Elsevier B.V.Öğe Measurement of the absolute branching fraction of ?c+ ? pKS0? decays(Elsevier, 2021) Ablikim, M.; Achasov, M. N.; Adlarson, P.; Ahmed, S.; Albrecht, M.; Alekseev, M.; Çetin, Serkant AliBased on 586 pb(-1) of e(+) e(-) annihilation data collected at a center-of-mass energy of root s = 4.6 GeV with the BESIII detector at the BEPCII collider, the absolute branching fraction of Lambda(+)(c) -> pK(S)(0)eta decays is measured for the first time to be B(Lambda(+)(c) -> pK(S)(0)eta) = (0.414 +/- 0.084 +/- 0.028)%, where the first uncertainty is statistical and the second is systematic. The result is compatible with a previous CLEO result on the relative branching fraction B(Lambda(+)(c) -> pK(S)(eta)(0))/B(Lambda(+)(c) -> pK(-)pi(+)), and consistent with theoretical predictions of SU(3) flavor symmetry. (C) 2021 The Author. Published by Elsevier B.V.Öğe Measurement of the e+e- ? ?+?- cross section between 600 and 900 MeV using initial state radiation (vol 753, pg 629, 2016)(Elsevier, 2021) Ablikim, M.; Achasov, M. N.; Adlarson, P.; Ahmed, S.; Albrecht, M.; Alekseev, M.; Çetin, Serkant AliIn Ref.[1] the BESIII collaboration published a cross section measurement of the process e(+)e(-) -> pi(+)pi(-) in the energy range between 600 and 900 MeV. In this corrigendum, we report a corrected evaluation of the statistical errors in terms of a fully propagated covariance matrix. The correction also yields a reduced statistical uncertainty for the hadronic vacuum polarization contribution to the anomalous magnetic moment of the muon, which now reads as a(mu)(pi pi,LO) (600 - 900 MeV) = (368.2 +/- 1.5(stat) +/- 3.3(syst)) x 10(-10). The central values of the cross section measurement and of a(mu)(pi pi,LO) , as well as the systematic uncertainties remain unchanged. (C) 2015 The Author(s). Published by Elsevier B.V. All rights reserved.Öğe Polarization and entanglement in baryon-antibaryon pair production in electron-positron annihilation(Nature Portfolio, 2019) Ablikim, M.; Achasov, M. N.; Ahmed, S.; Albrecht, M.; Alekseev, M.; Amoroso, A.; Çetin, Serkant AliParticles directly produced at electron-positron colliders, such as the J/psi meson, decay with relatively high probability into a baryon-antibaryon pair(1). For spin-1/2 baryons, the pair can have the same or opposite helicites. A non-vanishing phase Delta Phi between the transition amplitudes to these helicity states results in a transverse polarization of the baryons(2-4). From the joint angular distribution of the decay products of the bary-ons, this phase as well as the parameters characterizing the baryon and the antibaryon decays can be determined. Here, we report the measurement of Delta Phi = 42.4 +/- 0.6 +/- 0.5 degrees using Lambda -> p pi(-) and (Lambda) over bar -> (p) over bar pi(+), (n ) over bar pi(0) decays at BESIII. We find a value for the Lambda -> p pi(-) decay parameter of alpha(-) = 0.750 +/- 0.009 +/- 0.004, 17 +/- 3% higher than the current world average, which has been used as input for all Lambda polarization measurements since 1978(5,6). For (Lambda) over bar -> (p) over bar pi(+) we find alpha(+) = -0.758 +/- 0.010 +/- 0.007, giving A(CP) = (alpha(-) + alpha(+))/(alpha(-) - alpha(+)) = -0.006 +/- 0.012 +/- 0.007, a precise direct test of charge-parity symmetry (CP) violation in Lambda decays.Öğe Search for the reaction channel e+e- ? ?c??+?- at center-of-mass energies from 4.23 to 4.60 GeV(Amer Physical Soc, 2021) Ablikim, M.; Achasov, M. N.; Adlarson, P.; Ahmed, S.; Albrecht, M.; Alekseev, M.; Çetin, Serkant AliUsing data collected with the BESIII detector operating at the Beijing Electron Positron Collider, we search for the process e(+)e(-) -> eta(c)eta pi(+)pi(-). The search is performed using five large datasets recorded at center-of-mass energies of 4.23, 4.26, 4.36, 4.42, and 4.60 GeV. The eta(c) meson is reconstructed in 16 exclusive decay modes. No signal is observed in the mass region at any center-of-mass energy. The upper limits on the reaction cross sections are determined to be 6.2, 10.8, 27.6, 22.6 and 23.7 pb at the 90% confidence level at the center-of-mass energies listed above.Öğe Study of BESIII trigger efficiencies with the 2018 J/? data(Iop Publishing Ltd, 2021) Ablikim, M.; Achasov, M. N.; Adlarson, P.; Ahmed, S.; Albrecht, M.; Alekseev, M.; Çetin, Serkant AliUsing a dedicated data sample taken in 2018 on the J/psi peak, we perform a detailed study of the trigger efficiencies of the BESIII detector. The efficiencies are determined from three representative physics processes, namely Bhabha scattering, dimuon production and generic hadronic events with charged particles. The combined efficiency of all active triggers approaches 100% in most cases, with uncertainties small enough not to affect most physics analyses.
