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Sökning: WFRF:(Albrecht D. S.)

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1.
  • Niemi, MEK, et al. (författare)
  • 2021
  • swepub:Mat__t
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2.
  • Kanai, M, et al. (författare)
  • 2023
  • swepub:Mat__t
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3.
  • Schael, S., et al. (författare)
  • Electroweak measurements in electron positron collisions at W-boson-pair energies at LEP
  • 2013
  • Ingår i: Physics Reports. - : Elsevier BV. - 0370-1573 .- 1873-6270. ; 532:4, s. 119-244
  • Forskningsöversikt (refereegranskat)abstract
    • Electroweak measurements performed with data taken at the electron positron collider LEP at CERN from 1995 to 2000 are reported. The combined data set considered in this report corresponds to a total luminosity of about 3 fb(-1) collected by the four LEP experiments ALEPH, DELPHI, 13 and OPAL, at centre-of-mass energies ranging from 130 GeV to 209 GeV. Combining the published results of the four LEP experiments, the measurements include total and differential cross-sections in photon-pair, fermion-pair and four-fermion production, the latter resulting from both double-resonant WW and ZZ production as well as singly resonant production. Total and differential cross-sections are measured precisely, providing a stringent test of the Standard Model at centre-of-mass energies never explored before in electron positron collisions. Final-state interaction effects in four-fermion production, such as those arising from colour reconnection and Bose Einstein correlations between the two W decay systems arising in WW production, are searched for and upper limits on the strength of possible effects are obtained. The data are used to determine fundamental properties of the W boson and the electroweak theory. Among others, the mass and width of the W boson, m(w) and Gamma(w), the branching fraction of W decays to hadrons, B(W -> had), and the trilinear gauge-boson self-couplings g(1)(Z), K-gamma and lambda(gamma), are determined to be: m(w) = 80.376 +/- 0.033 GeV Gamma(w) = 2.195 +/- 0.083 GeV B(W -> had) = 67.41 +/- 0.27% g(1)(Z) = 0.984(-0.020)(+0.018) K-gamma - 0.982 +/- 0.042 lambda(gamma) = 0.022 +/- 0.019. (C) 2013 Elsevier B.V. All rights reserved.
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4.
  • Schael, S, et al. (författare)
  • Precision electroweak measurements on the Z resonance
  • 2006
  • Ingår i: Physics Reports. - : Elsevier BV. - 0370-1573 .- 1873-6270. ; 427:5-6, s. 257-454
  • Forskningsöversikt (refereegranskat)abstract
    • We report on the final electroweak measurements performed with data taken at the Z resonance by the experiments operating at the electron-positron colliders SLC and LEP. The data consist of 17 million Z decays accumulated by the ALEPH, DELPHI, L3 and OPAL experiments at LEP, and 600 thousand Z decays by the SLID experiment using a polarised beam at SLC. The measurements include cross-sections, forward-backward asymmetries and polarised asymmetries. The mass and width of the Z boson, m(Z) and Gamma(Z), and its couplings to fermions, for example the p parameter and the effective electroweak mixing angle for leptons, are precisely measured: m(Z) = 91.1875 +/- 0.0021 GeV, Gamma(Z) = 2.4952 +/- 0.0023 GeV, rho(l) = 1.0050 +/- 0.0010, sin(2)theta(eff)(lept) = 0.23153 +/- 0.00016. The number of light neutrino species is determined to be 2.9840 +/- 0.0082, in agreement with the three observed generations of fundamental fermions. The results are compared to the predictions of the Standard Model (SM). At the Z-pole, electroweak radiative corrections beyond the running of the QED and QCD coupling constants are observed with a significance of five standard deviations, and in agreement with the Standard Model. Of the many Z-pole measurements, the forward-backward asymmetry in b-quark production shows the largest difference with respect to its SM expectation, at the level of 2.8 standard deviations. Through radiative corrections evaluated in the framework of the Standard Model, the Z-pole data are also used to predict the mass of the top quark, m(t) = 173(+10)(+13) GeV, and the mass of the W boson, m(W) = 80.363 +/- 0.032 GeV. These indirect constraints are compared to the direct measurements, providing a stringent test of the SM. Using in addition the direct measurements of m(t) and m(W), the mass of the as yet unobserved SM Higgs boson is predicted with a relative uncertainty of about 50% and found to be less than 285 GeV at 95% confidence level. (c) 2006 Elsevier B.V. All rights reserved.
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5.
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6.
  • Singh, B. P., et al. (författare)
  • Experimental access to Transition Distribution Amplitudes with the PANDA experiment at FAIR
  • 2015
  • Ingår i: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 51:8
  • Tidskriftsartikel (refereegranskat)abstract
    • Baryon-to-meson Transition Distribution Amplitudes (TDAs) encoding valuable new information on hadron structure appear as building blocks in the collinear factorized description for several types of hard exclusive reactions. In this paper, we address the possibility of accessing nucleon-to-pion (pi N) TDAs from (p) over barp -> e(+)e(-)pi(0) reaction with the future PANDA detector at the FAIR facility. At high center-of-mass energy and high invariant mass squared of the lepton pair q(2), the amplitude of the signal channel (p) over barp -> e(+)e(-)pi(0) admits a QCD factorized description in terms of pi N TDAs and nucleon Distribution Amplitudes (DAs) in the forward aid backward kinematic regimes. Assuming the validity of this factorized description, we perform feasibility studies for measuring (p) over barp -> e(+)e(-)pi(0) with the PANDA detector. Detailed simulations on signal reconstruction efficiency as well as on rejection of the most severe background channel, i.e. (p) over barp -> pi(+)pi(-)pi(0) were performed for the center-of-mass energy squared s = 5 GeV2 and s = 10 GeV2, in the kinematic regions 3.0 < q(2) < 4.3 GeV2 and 5 < q(2) < 9 GeV2, respectively, with a neutral pion scattered in the forward or backward cone vertical bar cos theta(pi 0)vertical bar > 0.5 in the proton-antiproton center-of-mass frame. Results of the simulation show that the particle identification capabilities of the PANDA detector will allow to achieve a background rejection factor of 5 . 10(7) (1 . 10(7)) at low (high) q(2) for s = 5 GeV2, and of 1 . 10(8) (6 . 10(6)) at low (high) q(2) for s = 10 GeV2, while keeping the signal reconstruction efficiency at around 40%. At both energies, a clean lepton signal can be reconstructed with the expected statistics corresponding to 2 of integrated luminosity. The cross sections obtained from the simulations are used to show that a test of QCD collinear factorization can be done at the lowest order by measuring scaling laws and angular distributions. The future measurement of the signal channel cross section with PANDA will provide a new test of the perturbative QCD description of a novel class of hard exclusive reactions and will open the possibility of experimentally accessing pi N TDAs.
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7.
  • Erni, W., et al. (författare)
  • Technical design report for the PANDA (AntiProton Annihilations at Darmstadt) Straw Tube Tracker
  • 2013
  • Ingår i: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001 .- 1434-601X. ; 49:2
  • Tidskriftsartikel (refereegranskat)abstract
    • This document describes the technical layout and the expected performance of the Straw Tube Tracker (STT), the main tracking detector of the PANDA target spectrometer. The STT encloses a Micro-Vertex-Detector (MVD) for the inner tracking and is followed in beam direction by a set of GEM stations. The tasks of the STT are the measurement of the particle momentum from the reconstructed trajectory and the measurement of the specific energy loss for a particle identification. Dedicated simulations with full analysis studies of certain proton-antiproton reactions, identified as being benchmark tests for the whole PANDA scientific program, have been performed to test the STT layout and performance. The results are presented, and the time lines to construct the STT are described.
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8.
  • Singh, B., et al. (författare)
  • Feasibility study for the measurement of pi N transition distribution amplitudes at (P)over-barANDA in (P)over-barp -> J/psi pi(0)
  • 2017
  • Ingår i: Physical Review D. - : AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 95:3
  • Tidskriftsartikel (refereegranskat)abstract
    • The exclusive charmonium production process in (P) over barp annihilation with an associated pi 0 meson (p) over barp -> J/psi pi(0) is studied in the framework of QCD collinear factorization. The feasibility of measuring this reaction through the J/psi -> e(+) e(-) decay channel with the AntiProton ANnihilation at DArmstadt ((P) over bar ANDA) experiment is investigated. Simulations on signal reconstruction efficiency as well as the background rejection from various sources including the (P) over barp -> pi(+)pi(-)pi(0) and (p) over barp -> J/psi pi(0)pi(0) reactions are performed with PANDAROOT, the simulation and analysis software framework of the (P) over bar ANDA experiment. It is shown that the measurement can be done at (P) over bar ANDA with significant constraining power under the assumption of an integrated luminosity attainable in four to five months of data taking at the maximum design luminosity.
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9.
  • Collaboration, The PANDA, et al. (författare)
  • Feasibility studies of time-like proton electromagnetic form factors at PANDA at FAIR
  • 2016
  • Ingår i: European Physical Journal A. - : Springer Publishing Company. - 1434-6001 .- 1434-601X. ; 52:10
  • Tidskriftsartikel (refereegranskat)abstract
    • Simulation results for future measurements of electromagnetic proton form factors at P ¯ ANDA (FAIR) within the PandaRoot software framework are reported. The statistical precision with which the proton form factors can be determined is estimated. The signal channel p¯ p→ e+e- is studied on the basis of two different but consistent procedures. The suppression of the main background channel, i.e.p¯ p→ π+π-, is studied. Furthermore, the background versus signal efficiency, statistical and systematical uncertainties on the extracted proton form factors are evaluated using two different procedures. The results are consistent with those of a previous simulation study using an older, simplified framework. However, a slightly better precision is achieved in the PandaRoot study in a large range of momentum transfer, assuming the nominal beam conditions and detector performance.
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10.
  • Singh, B., et al. (författare)
  • Study of doubly strange systems using stored antiprotons
  • 2016
  • Ingår i: Nuclear Physics A. - : Elsevier. - 0375-9474 .- 1873-1554. ; 954, s. 323-340
  • Tidskriftsartikel (refereegranskat)abstract
    • Bound nuclear systems with two units of strangeness are still poorly known despite their importance for many strong interaction phenomena. Stored antiprotons beams in the GeV range represent an unparalleled factory for various hyperon-antihyperon pairs. Their outstanding large production probability in antiproton collisions will open the floodgates for a series of new studies of systems which contain two or even more units of strangeness at the PANDA experiment at FAIR. For the first time, high resolution gamma-spectroscopy of doubly strange Lambda Lambda-hypernuclei will be performed, thus complementing measurements of ground state decays of Lambda Lambda-hypernuclei at J-PARC or possible decays of particle unstable hypernuclei in heavy ion reactions. High resolution spectroscopy of multistrange Xi(-) -atoms will be feasible and even the production of Omega(-) -atoms will be within reach. The latter might open the door to the vertical bar S vertical bar = 3 world in strangeness nuclear physics, by the study of the hadronic Omega(-) -nucleus interaction. For the first time it will be possible to study the behavior of Xi(+) in nuclear systems under well controlled conditions.
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11.
  • Ablikim, M., et al. (författare)
  • Measurement of e(+)e(-) -> D(D)over-bar cross sections at the psi(3770) resonance
  • 2018
  • Ingår i: Chinese Physics C. - : IOP PUBLISHING LTD. - 1674-1137 .- 2058-6132. ; 42:8
  • Tidskriftsartikel (refereegranskat)abstract
    • We report new measurements of the cross sections for the production of D (D) over bar final states at the psi(3770) resonance. Our data sample consists of an integrated luminosity of 2.93 fb(-1) of e(+)e(-) annihilation data produced by the BEPCII collider and collected and analyzed with the BESIII detector. We exclusively reconstruct three D-0 and six D+ hadronic decay modes and use the ratio of the yield of fully reconstructed D (D) over bar events ("double tags") to the yield of all reconstructed D or (D) over bar mesons ("single tags") to determine the number of D-0(D) over bar (0) and D+D- events, benefiting from the cancellation of many systematic uncertainties. Combining these yields with an independent determination of the integrated luminosity of the data sample, we find the cross sections to be sigma(e(+)e(-) -> D-0(D) over bar (0)(-) )=(3.615 +/- 0.010 +/- 0.038) nb and sigma(e(+)e(-) -> D+D-)=(2.830 +/- 0.011 +/- 0.026) nb, where the uncertainties are statistical and systematic, respectively.
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12.
  • Ablikim, M., et al. (författare)
  • Measurement of the integrated Luminosities of cross-section scan data samples around the psi(3770) mass region
  • 2018
  • Ingår i: Chinese Physics C. - : SCIENCE PRESS. - 1674-1137 .- 2058-6132. ; 42:6
  • Tidskriftsartikel (refereegranskat)abstract
    • To investigate the nature of the psi(3770) resonance and to measure the cross section for e(+)e(-) -> D (D) over bar, a cross-section scan data sample, distributed among 41 center-of-mass energy points from 3.73 to 3.89 GeV, was taken with the BESIII detector operated at the BEPCII collider in the year 2010. By analyzing the large angle Bhabha scattering events, we measure the integrated luminosity of the data sample at each center-of-mass energy point. The total integrated luminosity of the data sample is 76.16 +/- 0.04 +/- 0.61 pb(-1), where the first uncertainty is statistical and the second systematic.
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13.
  • Ablikim, M., et al. (författare)
  • Search for invisible decays of omega and phi with J/psi data at BESIII
  • 2018
  • Ingår i: Physical Review D. - : American Physical Society. - 2470-0010 .- 2470-0029. ; 98:3
  • Tidskriftsartikel (refereegranskat)abstract
    • Using a data sample of (1310.6 +/- 7.0) x 10(6) J/psi events collected with the BESIII detector operating at the BEPCII collider, we perform the first experimental search for invisible decays of a light vector meson (V = omega, phi) via J/psi -> V-eta decays. The decay of eta -> pi(+)pi(-)pi(0) is utilized to tag the V meson decaying into the invisible final state. No evidence for a significant invisible signal is observed, and the upper limits on the ratio of branching fractions at the 90% confidence level are determined to be B(omega -> invisible)/B(omega -> pi(+)pi(-)pi(0)) < 8.1 x 10(-5) and B(phi -> invisible)/B(phi -> K+K-) < 3.4 x 10(-4). By using the world average values of B(omega -> pi(+)pi(-)pi(0) and B(phi -> K+K-,) the upper limits on the decay branching fractions at the 90% confidence level are set as B(omega -> invisible) < 7.3 x 10(-5) and B(phi -> invisible) < 1.7 x 10(-4), respectively.
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14.
  • Barucca, G., et al. (författare)
  • The potential of Λ and Ξ- studies with PANDA at FAIR
  • 2021
  • Ingår i: European Physical Journal A. - : Springer Nature. - 1434-6001 .- 1434-601X. ; 57:4
  • Tidskriftsartikel (refereegranskat)abstract
    • The antiproton experiment PANDA at FAIR is designed to bring hadron physics to a new level in terms of scope, precision and accuracy. In this work, its unique capability for studies of hyperons is outlined. We discuss ground-state hyperons as diagnostic tools to study non-perturbative aspects of the strong interaction, and fundamental symmetries. New simulation studies have been carried out for two benchmark hyperon-antihyperon production channels: p¯ p→ Λ¯ Λ and p¯ p→ Ξ¯ +Ξ-. The results, presented in detail in this paper, show that hyperon-antihyperon pairs from these reactions can be exclusively reconstructed with high efficiency and very low background contamination. In addition, the polarisation and spin correlations have been studied, exploiting the weak, self-analysing decay of hyperons and antihyperons. Two independent approaches to the finite efficiency have been applied and evaluated: one standard multidimensional efficiency correction approach, and one efficiency independent approach. The applicability of the latter was thoroughly evaluated for all channels, beam momenta and observables. The standard method yields good results in all cases, and shows that spin observables can be studied with high precision and accuracy already in the first phase of data taking with PANDA.
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15.
  • Ablikim, M., et al. (författare)
  • Amplitude analysis of D0 → K -π+π+π-
  • 2017
  • Ingår i: Physical Review D. - 2470-0010 .- 2470-0029. ; 95:7
  • Tidskriftsartikel (refereegranskat)abstract
    • We present an amplitude analysis of the decay D0 → K -π+π+π- based on a data sample of 2.93  fb−1 acquired by the BESIII detector at the ψ(3770) resonance. With a nearly background free sample of about 16000 events, we investigate the substructure of the decay and determine the relative fractions and the phases among the different intermediate processes. Our amplitude model includes the two-body decays D0 → ¯K*0ρ0, D0 → K−a+1(1260) and D0 → K−1(1270)π+, the three-body decays D0 →¯K*0π+π− and D0 → K−π+ρ0, as well as the four-body nonresonant decay D0 → K−π+π+π−. The dominant intermediate process is D0 → K−a+1(1260), accounting for a fit fraction of 54.6%.
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16.
  • Ablikim, M., et al. (författare)
  • First measurement of e(+)e(-) -> pK(S)(0)(n)over-barK(-) + c.c. above open charm threshold
  • 2018
  • Ingår i: Physical Review D. - 2470-0010 .- 2470-0029. ; 98:3
  • Tidskriftsartikel (refereegranskat)abstract
    • The process e(+)e(-) -> pK(S)(0)(n) over barK(-) + c.c. and its intermediate processes are studied for the first time, using data samples collected with the BESIII detector at BEPCII at center-of-mass energies of 3.773, 4.008, 4.226, 4.258, 4.358, 4.416, and 4.600 GeV, with a total integrated luminosity of 7.4 fb(-1). The Born cross section of e(+)e(-) -> pK(S)(0)(n) over barK(-) + c.c. is measured at each center-of-mass energy, but no significant resonant structure in the measured cross-section line shape between 3.773 and 4.600 GeV is observed. No evident structure is detected in the pK(-), nK(S)(0), pK(S)(0), nK(+), p (n) over bar, or (KSK-)-K-0 invariant mass distributions except for Lambda(1520). The Born cross sections of e(+)e(-) -> Lambda(1520)(n) over barK(S)(0) + c.c. and e(+)e(-) -> Lambda(1520)(p) over barK(+) + c.c. are measured, and the 90% confidence level upper limits on the Born cross sections of e(+)e(-) -> Lambda(1520)(Lambda) over bar (1520) are determined at the seven center-of-mass energies. There is an evident difference in line shape and magnitude of the measured cross sections between e(+)e(-) -> Lambda(1520)(-> pK(-))(n) over barK(S)(0) and e(+)e(-) -> pK-(Lambda) over bar (1520)(-> (n) over barK(S)(0)).
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17.
  • Ablikim, M., et al. (författare)
  • Measurement of Singly Cabibbo Suppressed Decays Lambda(+)(c) -> p pi(+)pi(-) and Lambda(+)(c) -> pK(+)K(-)
  • 2016
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 117:23
  • Tidskriftsartikel (refereegranskat)abstract
    • Using 567 pb(-1) of data collected with the BESIII detector at a center-of-mass energy of root s = 4.599 GeV, near the Lambda(+)(c)->(Lambda) over bar (-)(c) threshold, we study the singly Cabibbo-suppressed decays Lambda c(+) -> p pi(+) pi(-) and Lambda(+)(c) -> pK(+) K- By normalizing with respect to the Cabibbo-favored decay Lambda(+)(c)-> p pi(+)pi(-) we obtain ratios of branching fractions: [B(Lambda(+)(c) -> p pi(+)pi(-))/B(Lambda(+)(c) -> pK(-)pi(+))] = (6.70 +/- 0.48 +/- 0.25)% [B Lambda(+)(c) -> p phi)/B(Lambda(+)(c) -> pK(-)pi(+))] = (1.81 +/- 0.33 +/- 0.13)%,and [B(Lambda(+)(c) -> pK(+)K(non-phi)(-)/B(Lambda(+)(c) -> pK(-)pi(+))] (9.36 +/- 2.22 +/- 0.71)x10(-3), where the uncertainties are statistical and systematic, respectively. The absolute branching fractions are also presented. Among these measurements, the decay Lambda(+)(c) -> p pi(+)pi(-) is observed for the first time, and the precision of the branching fraction for Lambda(+)(c) -> pK(+)K(non-phi)(-) and Lambda(+)(c) -> p phi is significantly improved.
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18.
  • Ablikim, M., et al. (författare)
  • Measurements of cross section of e(+)e(-) -> p(p)over-bar pi(0) at center-of-mass energies between 4.008 and 4.600 GeV
  • 2017
  • Ingår i: Physics Letters B. - : ELSEVIER SCIENCE BV. - 0370-2693 .- 1873-2445. ; 771, s. 45-51
  • Tidskriftsartikel (refereegranskat)abstract
    • Based on e(+)e(-) annihilation data samples collected with the BESIII detector at the BEPCII collider at 13 center-of-mass energies from 4.008 to 4.600 GeV, measurements of the Born cross section of e(+)e(-) -> p (p) over bar pi(0) are performed. No significant resonant structure is observed in the measured energy dependence of the cross section. The upper limit on the Born cross section of e(+)e(-) -> Y (4260) -> p (p) over bar pi(0) at the 90% C. L. is determined to be 0.01 pb. The upper limit on the ratio of the branching fractions B(Y(4260) -> p (p) over bar pi(0))/B(Y(4260) -> pi(+)pi(-) j/Psi) at the 90% C. L. is determined to be 0.02%.
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19.
  • Ablikim, M., et al. (författare)
  • Measurements of psi(3686) -> K-Lambda(Xi)over-bar(+) + c.c. and psi(3686) -> gamma K-Lambda(Xi)over-bar(+) + c.c.
  • 2015
  • Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 91:9
  • Tidskriftsartikel (refereegranskat)abstract
    • Using a sample of 1.06 x 10(8) psi(3686) events produced in e(+)e(-) collisions at root s = 3.686 GeV and collected with the BESIII detector at the BEPCII collider, we present studies of the decays psi(3686) -> K-Lambda(Xi) over bar (+) + c.c. and psi(3686) -> gamma K-Lambda(Xi) over bar (+) + c.c. We observe two hyperons, Xi(1690)(-) and Xi(1820)(-), in the K-Lambda invariant mass distribution in the decay psi(3686) -> K-Lambda(Xi) over bar (+) + c.c. with significances of 4.9 sigma and 6.2 sigma, respectively. The branching fractions of psi(3686) -> K-Lambda(Xi) over bar (+) + c.c., psi(3686) -> K-Sigma(0)(Xi) over bar (+) + c.c, psi(3686) -> gamma chi cJ -> gamma K-Lambda(Xi) over bar (+) + c.c (J = 0, 1, 2), and psi(3686) -> Xi(1690/1820)(-)(Xi) over bar (+) + c.c with sub-sequent decay Xi(1690/1820)(-) -> K-Lambda are measured for the first time.
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20.
  • Ablikim, M., et al. (författare)
  • Measurements of the branching fractions for D+ -> (KSKSK+)-K-0-K-0+, (KSKS0)-K-0 pi + and D-0 -> (KSKS0)-K-0, (KSKSKS0)-K-0-K-0
  • 2017
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 765, s. 231-237
  • Tidskriftsartikel (refereegranskat)abstract
    • By analyzing 2.93 fb(-1) of data taken at the psi(3770) resonance peak with the BESIII detector, we measure the branching fractions for the hadronic decays D+ -> (KSKSK+)-K-0-K-0, D+ -> (KSKS0)-K-0 pi(+), D-0 -> (KSKS0)-K-0 and D-0 -> (KSKSKS0)-K-0-K-0.They are determined to be B(D+ -> (KSKSK+)-K-0-K-0) = (2.54 +/- 0.05(stat.) +/- 0.12(sys.))x 10(-3), B(D+ -> (KSKS0)-K-0 pi(+)) = (2.70 +/- 0.05(stat,) +/- 0.12(sys.)) x 10(-3), B(D+ -> (KSKS0)-K-0) = (1.67 +/- 0.11(stat.) +/- 0.11(sys.)) x 10(-4) and B(D+ -> (KSKSKS0)-K-0-K-0) = (7.21 +/- 0.33(stat.) +/- 0.44(sys,)) x 10(-4), where the second one is measured for the first time and the others are measured with significantly improved precision over the previous measurements.
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21.
  • Ablikim, M., et al. (författare)
  • Observation of an Anomalous Line Shape of the eta 'pi(+)pi(-) Mass Spectrum near the p(p)over-bar Mass Threshold in J/psi -> gamma eta 'pi(+)pi(-)
  • 2016
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 117:4
  • Tidskriftsartikel (refereegranskat)abstract
    • Using 1.09 x 10(9) J/psi events collected by the BESIII experiment in 2012, we study the J / psi -> gamma eta'pi(+)pi(-) process and observe a significant abrupt change in the slope of the eta'pi(+)pi(-) invariant mass distribution at the proton-antiproton (p (p) over bar) mass threshold. We use two models to characterize the eta'pi(+)pi(-) line shape around 1.85 GeV/c(2): one that explicitly incorporates the opening of a decay threshold in the mass spectrum (Flatte formula), and another that is the coherent sum of two resonant amplitudes. Both fits show almost equally good agreement with data, and suggest the existence of either a broad state around 1.85 GeV/c(2) with strong couplings to the c final states or a narrow state just below the p (p) over bar mass threshold. Although we cannot distinguish between the fits, either one supports the existence of a p (p) over bar moleculelike state or bound state with greater than 7 sigma significance.
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22.
  • Ablikim, M., et al. (författare)
  • Observation of e(+)e(-) -> eta ' J/psi center-of-mass energies between 4.189 and 4.600 GeV
  • 2016
  • Ingår i: PHYSICAL REVIEW D. - 2470-0010. ; 94:3
  • Tidskriftsartikel (refereegranskat)abstract
    • The process e(+)e(-) -> eta' J/psi is observed for the first time with a statistical significance of 8.6 sigma at center-of-mass energy root s = 4.226 GeV and 7.3 sigma at root s = 4.258 GeV using data samples collected with the BESIII detector. The Born cross sections are measured to be (3.7 +/- 0.7 +/- 0.3) and (3.9 +/- 0.8 +/- 0.3) pb at root s = 4.226 and 4.258 GeV, respectively, where the first errors are statistical and the second systematic. Upper limits at the 90% confidence level of the Born cross sections are also reported at other 12 energy points.
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23.
  • Ablikim, M., et al. (författare)
  • Observation of J/psi -> p(p)over-bara(0)(980) at BESIII
  • 2014
  • Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 90:5, s. 052009-
  • Tidskriftsartikel (refereegranskat)abstract
    • Using 2.25 x 10(8) J/psi events collected with the BESIII detector at the BEPCII storage rings, we observe for the first time the process J/psi -> p (p) over bara(0)(980) -> pi(0)eta with a significance of 6.5 sigma (3.2 sigma including systematic uncertainties). The product branching fraction of J/psi -> p (p) over bara(0)(980) -> p (p) over bara(0)pi(0)eta is measured to be (6.8 +/- 1.2 +/- 1.3) x 10(-5), where the first error is statistical and the second is systematic. This measurement provides information on the a(0) production near threshold coupling to p (p) over bar and improves the understanding of the dynamics of J/psi decays to four-body processes.
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24.
  • Ablikim, M., et al. (författare)
  • Amplitude analysis of the chi(c1) -> eta pi(+)pi(-) decays
  • 2017
  • Ingår i: Physical Review D. - : AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 95:3
  • Tidskriftsartikel (refereegranskat)abstract
    • Using 448.0 x 10(6) psi(3686) events collected with the BESIII detector, an amplitude analysis is performed for psi(3686) -> gamma chi(c1), chi(c1) ->eta pi(+)pi(-) decays. The most dominant two- body structure observed is a(0)(980)(+/-) pi(-/+); a(0)(980)(+/-) -> eta pi(+/-.) line shape is modeled using a dispersion relation, and a significant nonzero a(0) (980) coupling to the eta'pi channel is measured. We observe chi(c1) -> a(2)(1700)pi production for the first time, with a significance larger than 17 sigma. The production of mesons with exotic quantum numbers, J(PC) = 1(-+), is investigated, and upper limits for the branching fractions chi(c1) -> pi(1)(1400)(+/-)pi(-/+) , chi(c1) -> pi(1)(1600)(+/-)pi(-/+) and chi(c1) -> pi 1(2015)(+/-)pi(-/+) with subsequent pi(1)(X)(+/-) -> eta pi(+/-) decay, are determined.
  •  
25.
  • Ablikim, M., et al. (författare)
  • Amplitude analysis of the KSKS system produced in radiative J /psi decays
  • 2018
  • Ingår i: Physical Review D. - : AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 98:7
  • Tidskriftsartikel (refereegranskat)abstract
    • An amplitude analysis of the KSKS system produced in radiative J/psi decays is performed using the (1310.6 +/- 7.0) x 10(6) nip decays collected by the BESIII detector. Two approaches are presented. A mass-dependent analysis is performed by parametrizing the KSKS invariant mass spectrum as a sum of Breit-aligner line shapes. Additionally, a mass-independent analysis is performed to extract a piecewise function that describes the dynamics of the KSKS system while making minimal assumptions about the properties and number of poles in the amplitude. The dominant amplitudes in the mass-dependent analysis include the f(0)(1710), f(0)(2200), and f(2)'(1525). The mass-independent results, which are made available as input for further studies, are consistent with those of the mass-dependent analysis and are useful for a systematic study of hadronic interactions. The branching fraction of radiative J/psi decays to KSKS is measured to be (8.1 +/- 0.4) x 10(-4), where the uncertainty is systematic and the statistical uncertainty is negligible.
  •  
26.
  • Ablikim, M., et al. (författare)
  • An improved limit for Gamma(ee) of X(3872) and Gamma(ee) measurement of psi(3686)
  • 2015
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 749, s. 414-420
  • Tidskriftsartikel (refereegranskat)abstract
    • Using the data sets taken at center-of-mass energies above 4 GeV by the BESIII detector at the BEPCII storage ring, we search for the reaction e(+)e(-) -> gamma(ISR) X(3872) -> gamma(ISR)pi(+)pi(-) J/psi via the Initial State Radiation technique. The production of a resonance with quantum numbers J(PC) = 1(++) such as the X(3872) via single photon e(+)e(-) annihilation is forbidden, but is allowed by a next-to-leading order box diagram. We do not observe a significant signal of X(3872), and therefore give an upper limit for the electronic width times the branching fraction Gamma B-X(3872)(ee)(X(3872) -> pi(+)pi(-) J/psi) < 0.13 eVat the 90% confidence level. This measurement improves upon existing limits by a factor of 46. Using the same final state, we also measure the electronic width of the psi(3686) to be Gamma(psi)(ee)(3686) ee = 2213 +/- 18(stat) +/- 99(sys) eV.
  •  
27.
  • Ablikim, M., et al. (författare)
  • Determination of the Spin and Parity of the Z(c)(3900)
  • 2017
  • Ingår i: Physical Review Letters. - : AMER PHYSICAL SOC. - 0031-9007 .- 1079-7114. ; 119:7
  • Tidskriftsartikel (refereegranskat)abstract
    • The spin and parity of the Z(c)(3900)(+/-) state are determined to be J(P) = 1(+) with a statistical significance larger than 7 sigma over other quantum numbers in a partial wave analysis of the process e(+)e(-) -> pi(+)pi(-) J/psi We use a data sample of 1.92 fb(-1) accumulated at root s = 4.23 and 4.26 GeV with the BESIII experiment. When parametrizing the Z(c)(3900)(+/-) with a Flatte-like formula, we determine its pole mass M-pole = (3881.2 +/- 4.2(stat) +/- 52.7(syst)) MeV/c(2) and pole width Gamma(pole) = (51.8 +/- 4.6(stat) +/- 36.0(syst)) MeV. We also measure cross sections for the process e(+)e(-) -> Z(c)(3900)(+)pi(-) + c.c. -> J/psi pi(+)pi(-) and determine an upper limit at the 90% confidence level for the process e(+)e(-) -> Z(c)(4020)(+)pi(-) + c.c. -> J/psi pi(+)pi(-).
  •  
28.
  • Ablikim, M., et al. (författare)
  • Evidence for e(+)e(-)->gamma chi c1,2 at center-of-mass energies from 4.009 to 4.360 GeV
  • 2015
  • Ingår i: Chinese Physics C. - : IOP Publishing. - 1674-1137 .- 2058-6132. ; 39:4
  • Tidskriftsartikel (refereegranskat)abstract
    • Using data samples collected at center-of-mass energies of root s=4.009, 4.230, 4.260, and 4.360 GeV with the BESIII detector operating at the BEPCII collider, we perform a search for the process e(+)e(-)->gamma chi(cJ) (J=0, 1, 2) and find evidence for e(+)e(-)->gamma chi(c1) and e(+)e(-)->gamma chi(c2) with statistical significances of 3.0 sigma and 3.4 sigma, respectively. The Born cross sections sigma(B)(e(+)e(-)->gamma chi(cJ)), as well as their upper limits at the 90% confidence level (C.L.) are determined at each center-of-mass energy.
  •  
29.
  • Ablikim, M., et al. (författare)
  • Measurement of B(psi(3770) -> gamma chi(c1)) and search for psi(3770) -> gamma chi(c2)
  • 2015
  • Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 91:9
  • Tidskriftsartikel (refereegranskat)abstract
    • We report a measurement of the branching fraction for psi(3770) -> gamma chi(c1) and search for the transition psi(3770) -> gamma chi(c2) based on 2.92 fb(-1) of e(+)e(-) data accumulated at root s = 3.773 GeV with the BESIII detector at the BEPCII collider. We measure B(psi(3770) -> gamma chi(c1)) = (2.48 +/- 0.15 +/- 0.23) x 10(-3), which is the most precise measurement to date. The upper limit on the branching fraction of psi(3770) -> gamma chi(c2) at a 90% confidence level is B(psi(3770) -> gamma chi(c2)) < 0.64 x 10(-3). The corresponding partial widths are Gamma(psi(3770) -> gamma chi(c1)) = (67.5 +/- 4.1 +/- 6.7)keV and Gamma(psi(3770) -> gamma chi(c2)) < 17.4 keV.
  •  
30.
  • Ablikim, M., et al. (författare)
  • Measurement of e(+)e(-) -> K(K)over-barJ/psi cross sections at center-of-mass energies from 4.189 to 4.600 GeV
  • 2018
  • Ingår i: Physical Review D. - : AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 97:7
  • Tidskriftsartikel (refereegranskat)abstract
    • We investigate the process e(+)e(-) -> K (K) over barJ/psi at center-of-mass energies from 4.189 to 4.600 GeV using 4.7 fb(-1) of data collected by the BESIII detector at the BEPCII collider. The Born cross sections for the reactions e(+)e(-) -> K(+)K(-)J/psi and K(S)(0)K(S)(0)J/psi are measured as a function of center-of-mass energy. The energy dependence of the cross section for e(+)e(-) -> K(+)K(-)J/psi is shown to differ from that for pi(+)pi(-)J/psi in the region around the Y(4260). In addition, there is evidence for a structure around 4.5 GeV in the e(+)e(-) -> K(+)K(-)J/psi cross section that is not present in pi(+)pi(-)J/psi.
  •  
31.
  • Ablikim, M., et al. (författare)
  • Measurement of higher-order multipole amplitudes in psi(3686) -> gamma chi(c1,2) with chi(c1,2) -> gamma J/psi and search for the transition eta(c)(2S) -> gamma J/psi
  • 2017
  • Ingår i: Physical Review D. - : AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 95:7
  • Tidskriftsartikel (refereegranskat)abstract
    • Using 106 x 10(6) psi(3686) events collected with the BESIII detector, we measure multipole amplitudes for the decay psi(3686) ->; gamma chi(c1,2) -> gamma gamma J/psi beyond the dominant electric-dipole amplitudes. The normalized magnetic-quadrupole (M2) amplitude for psi(3686) -> gamma chi(c1,2) -> gamma gamma J/psi and the normalized electric-dipole amplitudes for psi(3686) -> gamma chi(c2) -> gamma J/psi and determined. The M2 amplitudes for psi(3686) -> gamma chi(c1) and ; chi(c1,2) -> gamma J/psi are found to differ significantly from zero and are consistent with theoretical predictions. We also obtain the ratios of M2 contributions of psi(3686) and J/psi decays to;2,chi(c1,2,) b(2)(1/)b(2)(2) = 1.35 +/- 0.72 and a(2)(1/)a(2)(2) = 0.617 +/- 0.083,,which agree well with theoretical expectations. By considering the multipole contributions of chi(c1,2), we measure the product branching fractions for the cascade decays psi(3686) -> gamma chi(c 0,1,2) -> gamma gamma J/psi and search for the process eta(c)(2s) -> gamma J/psi through psi(3686) -> gamma eta(c)(2s).The product branching fraction for psi(3686) -> gamma chi(c0) -> gamma gamma J/psi is 3 sigma larger than published measurements, while those of psi(3686) -> gamma chi(c1,2) -> gamma gamma J/psi are consistent. No significant signal for the decay psi(3686) -> gamma eta(c) (2s) -> gamma gamma J/psi is observed, and the upper limit of the product branching fraction at the 90% confidence level is determined.
  •  
32.
  • Ablikim, M., et al. (författare)
  • Measurement of integrated luminosity and center-of-mass energy of data taken by BESIII at √s=2.125 GeV
  • 2017
  • Ingår i: Chinese Physics C. - : IOP Publishing. - 1674-1137 .- 2058-6132. ; 41:11
  • Tidskriftsartikel (refereegranskat)abstract
    • To study the nature of the state Y (2175), a dedicated data set of e(+)e(-) collision data was collected at the center-of-mass energy of 2.125 GeV with the BESIII detector at the BEPCII collider. By analyzing large-angle Bhabha scattering events, the integrated luminosity of this data set is determined to be 108.49 +/- 0.02 +/- 0.85 pb(-1), where the first uncertainty is statistical and the second one is systematic. In addition, the center-of-mass energy of the data set is determined with radiative dimuon events to be 2126.55 +/- 0.03 +/- 0.85 MeV, where the first uncertainty is statistical and the second one is systematic.
  •  
33.
  • Ablikim, M., et al. (författare)
  • Measurement of the absolute branching fraction of D*(s0) (2317)(+/-) -> pi D-0(s)+/-
  • 2018
  • Ingår i: Physical Review D. - : American Physical Society. - 2470-0010 .- 2470-0029. ; 97:5
  • Tidskriftsartikel (refereegranskat)abstract
    • The process e(+)e(-) -> D*D-+(s)*(s0) (2317)(-) + c.c. is observed for the first time with the data sample of 567 pb(-1) collected with the BESIII detector operating at the BEPCII collider at a center-of-mass energy root s = 4.6 GeV. The statistical significance of the D*(s0) (2317)(+/-) signal is 5.8 sigma and the mass is measured to be (2318.3 +/- 1.2 +/- 1.2) MeV/c(2). The absolute branching fraction B(D*(s0) (2317)(+/-) -> pi D-0(s)+/-) is measured as 1.00(-0.14)(+0.00) (stat)(-0.14)(+0.00) (syst) for the first time. The uncertainties are statistical and systematic, respectively.
  •  
34.
  • Ablikim, M., et al. (författare)
  • Measurement of the Absolute Branching Fraction of the Inclusive Decay Lambda(+)(c) -> Lambda plus X
  • 2018
  • Ingår i: Physical Review Letters. - : AMER PHYSICAL SOC. - 0031-9007 .- 1079-7114. ; 121:6
  • Tidskriftsartikel (refereegranskat)abstract
    • Based on an e(+)e(-) collision data sample corresponding to an integrated luminosity of 567 pb(-1) taken at the center-of-mass energy of root s = 4.6 GeV with the BESIII detector, we measure the absolute branching fraction of the inclusive decay Lambda(+)(c) -> Lambda + X to be B(Lambda(+)(c) -> Lambda + X) = (38.2(-2.2)(+2.8) +/- 0.9)% using the double-tag method, where X refers to any possible final state particles. In addition, we search for direct CP violation in the charge asymmetry of this inclusive decay for the first time, and obtain A(CP) [B(Lambda(+)(c) -> Lambda + X) - B((Lambda) over bar (-)(c) -> (Lambda) over bar + X)]/[B(Lambda(+)(c) -> Lambda + X) + B((Lambda) over bar (-)(c) -> (Lambda) over bar + X)] = (2.1(-6.6)(+7.0) +/- 1.6)%, a statistically limited result with no evidence of CP violation.
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35.
  •  
36.
  • Ablikim, M., et al. (författare)
  • Measurement of the matrix elements for the decays eta' -> eta pi(+) pi(-) and eta' -> eta pi(0)pi(0)
  • 2018
  • Ingår i: Physical Review D. - : AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 97:1
  • Tidskriftsartikel (refereegranskat)abstract
    • Based on a sample of 1.31 x 10(9) J/psi events collected with the BESIII detector, the matrix elements for the decays eta' -> eta pi(+) pi(-) and eta' -> eta pi(0)pi(0) are determined using 351,016 eta' -> (eta -> gamma gamma)pi' pi(-) and 56,249 eta' -> (eta -> gamma gamma)pi(0) pi(0) events with background levels less than 1%. Two commonly used representations are used to describe the Dalitz plot density. We find that an assumption of a linear amplitude does not describe the data well. A small deviation of the obtained matrix elements between eta' -> eta pi(+) pi(-) and eta' -> eta pi(0)pi(0) is probably caused by the mass difference between charged and neutral pions or radiative corrections. No cusp structure in eta' -> eta pi(0)pi(0) is observed.
  •  
37.
  • Ablikim, M., et al. (författare)
  • Measurement of the proton form factor by studying e(+)e(-) -> p(p)over-tilde
  • 2015
  • Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 91:11
  • Tidskriftsartikel (refereegranskat)abstract
    • Using data samples collected with the BESIII detector at the BEPCII collider, we measure the Born cross section of e(+)e(-) -> p (p) over tilde at 12 center-of-mass energies from 2232.4 to 3671.0 MeV. The corresponding effective electromagnetic form factor of the proton is deduced under the assumption that the electric and magnetic form factors are equal (vertical bar G(E)vertical bar = vertical bar G(M)vertical bar). In addition, the ratio of electric to magnetic form factors, vertical bar G(E)/G(M)vertical bar, and vertical bar G(M)vertical bar are extracted by fitting the polar angle distribution of the proton for the data samples with larger statistics, namely at root s = 2232.4 and 2400.0 MeV and a combined sample at root s = 3050.0, 3060.0 and 3080.0 MeV, respectively. The measured cross sections are in agreement with recent results from BABAR, improving the overall uncertainty by about 30%. The vertical bar G(E)/G(M)vertical bar ratios are close to unity and consistent with BABAR results in the same q(2) region, which indicates the data are consistent with the assumption that vertical bar G(E)vertical bar = vertical bar G(M)vertical bar within uncertainties.
  •  
38.
  • Ablikim, M., et al. (författare)
  • Measurement of y(CP) in D-0-(D)over-bar(0) oscillation using quantum correlations in e(+)e(-) -> D-0(D)over-bar(0) at root s=3.773 GeV
  • 2015
  • Ingår i: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 744, s. 339-346
  • Tidskriftsartikel (refereegranskat)abstract
    • We report a measurement of the parameter y(CP) in D-0-(D) over bar (0) oscillations performed by taking advantage of quantum coherence between pairs of D-0(D) over bar (0) mesons produced in e(+)e(-) annihilations near threshold. In this work, doubly-tagged D-0(D) over bar (0) events, where one D decays to a CP eigenstate and the other D decays in a semileptonic mode, are reconstructed using a data sample of 2.92 fb(-1) collected with the BESIII detector at the center-of-mass energy of root s = 3.773 GeV. We obtain y(CP) = (-2.0 +/- 1.3 +/- 0.7)%, where the first uncertainty is statistical and the second is systematic. This result is compatible with the current world average.
  •  
39.
  • Ablikim, M., et al. (författare)
  • Measurements of the absolute branching fractions for D-s(+) -> eta e(+)nu(e) and D-s(+) -> eta ' e(+)nu(e)
  • 2016
  • Ingår i: PHYSICAL REVIEW D. - 2470-0010. ; 94:11
  • Tidskriftsartikel (refereegranskat)abstract
    • By analyzing 482 pb(-1) of e(+)e(-) collision data collected at root s = 4.009 GeV with the BESIII detector at the BEPCII collider, we measure the absolute branching fractions for the semileptonic decays D-s(+) -> eta e(+)nu(e) and D-s(+) -> eta ' e(+)nu(e) to be B(D-s(+) -> eta e(+)nu(e)) = (2.30 +/- 0.31 +/- 0.08)% and B(D-s(+) -> eta ' e(+)nu(e)) = (0.93 +/- 0.30 +/- 0.05)%, respectively, and their ratio B(D-s(+) -> eta ' e(+)nu(e)) / B(D-s(+) -> eta ' e(+)nu(e)) = 0.40 +/- 0.14 +/- 0.02, where the first uncertainties are statistical and the second ones are systematic. The results are in good agreement with previous measurements within uncertainties; they can be used to determine the eta-eta' mixing angle and improve upon the D-s(+) semileptonic branching ratio precision.
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40.
  • Ablikim, M., et al. (författare)
  • Measurements of the branching fractions for the semileptonic decays D-s(+) -> phi e(+)v(e), phi mu(+)v(mu), eta mu(+)v(mu) and eta 'mu(+)v(mu)
  • 2018
  • Ingår i: Physical Review D. - : American Physical Society. - 2470-0010 .- 2470-0029. ; 97:1
  • Tidskriftsartikel (refereegranskat)abstract
    • By analyzing 482 pb(-1) of e(+) e(-) collision data collected at the center-of-mass energy root s = 4.009 GeV with the BESIII detector, we measure the branching fractions for the semi-leptonic decays D-s(+) -> phi e(+)v(e), phi mu(+)v(mu), eta mu(+)v(mu) and eta'mu(+)v(mu) to be B(D-s(+) -> phi e(+)v(e)) = (2.26 +/- 0.45 +/- 0.09)%, B(D-s(+) -> phi mu+v(mu)) = (1.94 +/- 0.53 +/- 0.09)%, B(D-s(+) -> eta mu(+)v(mu)) = (2.42 +/- 0.46 +/- 011)% and B(D-s(+) -> eta'mu(+)v(mu)) = (1.06 +/- 0.54 +/- 0.07)%, where the first and second uncertainties are statistical and systematic, respectively. The branching fractions for the three semi-muonic decays D-s(+) -> phi mu(+)v(mu), eta mu(+)v(mu) and eta'mu(+)v(mu) are determined for the first time and that of D-s(+) -> phi e(+)v(e) is consistent with the world average value within uncertainties.
  •  
41.
  • Ablikim, M., et al. (författare)
  • Observation of a cross-section enhancement near mass threshold in e(+)e(-) -> Lambda(Lambda)over-bar
  • 2018
  • Ingår i: Physical Review D. - : AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 97:3
  • Tidskriftsartikel (refereegranskat)abstract
    • The process e(+)e(-) -> Lambda(Lambda) over bar is studied using data samples at root s = 2.2324, 2.400, 2.800 and 3.080 GeV collected with the BESIII detector operating at the BEPCII collider. The Born cross section is measured at root s = 2.2324 GeV, which is 1.0 MeVabove the Lambda(Lambda) over bar mass threshold, to be 305 +/- 45(-36)(+66) pb, where the first uncertainty is statistical and the second systematic. The cross section near threshold is larger than that expected from theory, which predicts the cross section to vanish at threshold. The Born cross sections at root s = 2.400, 2.800 and 3.080 GeV are measured and found to be consistent with previous experimental results, but with improved precision. Finally, the corresponding effective electromagnetic form factors of Lambda are deduced.
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42.
  • Ablikim, M., et al. (författare)
  • Observation of e(+)e(-) -> pi(0)pi(0)h(c) and a Neutral Charmoniumlike Structure Z(c)(4020)(0)
  • 2014
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 113:21, s. 212002-
  • Tidskriftsartikel (refereegranskat)abstract
    • Using data collected with the BESIII detector operating at the Beijing Electron Positron Collider at center-of-mass energies of root s = 4.23, 4.26, and 4.36 GeV, we observe e(+)e(-) -> pi(0)pi(0)h(c) for the first time. The Born cross sections are measured and found to be about half of those of e(+)e(-) -> pi(+)pi(-)h(c) within less than 2 sigma. In the pi(0)h(c) mass spectrum, a structure at 4.02 GeV/c(2) is found. It is most likely to be the neutral isospin partner of the Z(c)(4020)(+/-) observed in the process of e(+)e(-) -> pi(+)pi(-)h(c) being found. A fit to the pi(0)h(c) invariant mass spectrum, with the width of the Z(c)(4020)(0) fixed to that of its charged isospin partner and possible interferences with non-Z(c)(4020)(0) amplitudes neglected, gives a mass of (4023.9 +/- 2.2 +/- 3.8) MeV/c(2) for the Z(c)(4020)(0), where the first error is statistical and the second systematic.
  •  
43.
  • Ablikim, M., et al. (författare)
  • Observation of h(c) Radiative Decay h(c) -> gamma eta ' and Evidence for h(c) -> gamma eta
  • 2016
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 116:25
  • Tidskriftsartikel (refereegranskat)abstract
    • A search for radiative decays of the P-wave spin singlet charmonium resonance h(c) is performed based on 4.48 x 10(8) psi' events collected with the BESIII detector operating at the BEPCII storage ring. Events of the reaction channels h(c) -> gamma eta' and gamma eta are observed with a statistical significance of 8.4 sigma and 4.0 sigma, respectively, for the first time. The branching fractions of h(c) -> gamma eta' and h(c) -> gamma eta' are measured to be B(h(c) -> gamma eta') = (1.52 +/- 0.27 +/- 0.29) x 10(-3) and B(h(c) -> gamma eta) = (4.7 +/- 1.5 +/- 1.4) x 10(-4), respectively, where the first errors are statistical and the second are systematic uncertainties.
  •  
44.
  • Ablikim, M., et al. (författare)
  • Observation of J/psi -> gamma eta pi(0)
  • 2016
  • Ingår i: PHYSICAL REVIEW D. - 2470-0010. ; 94:7
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the first study of the process J/psi -> gamma eta pi(0) using (223.7 +/- 1.4) x 10(6) J/psi events accumulated with the BESIII detector at the BEPCII facility. The branching fraction for J/psi -> gamma eta pi(0) is measured to be B(J/psi -> gamma eta pi(0)) = (2.14 +/- 0.18(stat) +/- 0.25(syst)) x 10(-5). With a Bayesian approach, the upper limits of the branching fractions B(J/psi -> gamma a(0)(980), a(0)(980) -> eta pi(0)) and B(J/psi -> gamma a(2)(1320), a(2)(1320) -> eta pi(0)) are determined to be 2.5 x 10(-6) and 6.6 x 10(-6) at the 95% confidence level, respectively. All of these measurements are given for the first time.
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45.
  • Ablikim, M., et al. (författare)
  • Observation of the Dalitz decay eta ' -> gamma e(+)e(-)
  • 2015
  • Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 92:1
  • Tidskriftsartikel (refereegranskat)abstract
    • We report the first observation of the Dalitz decay eta' -> gamma e(+)e(-), based on a data sample of 1.31 billion J/psi events collected with the BESIII detector. The eta' mesons are produced via the J/psi -> gamma eta' decay process. The ratio (eta' -> gamma e(+)e(-))/Gamma (eta' -> gamma gamma) is measured to be (2.13 +/- 0.09(stat) +/- 0.07(sys)) x 10(-2). This corresponds to a branching fraction B(eta' -> gamma e(+)e(-)) = (4.69 +/- 0.20(stat) +/- 0.23(sys)) x 10(-4). The transition form factor is extracted and different expressions are compared to the measured dependence on the e(+)e(-) invariant mass. The results are consistent with the prediction of the vector meson dominance model.
  •  
46.
  • Ablikim, M., et al. (författare)
  • Observation of the electromagnetic doubly OZI-suppressed decay J/psi -> phi pi(0)
  • 2015
  • Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 91:11
  • Tidskriftsartikel (refereegranskat)abstract
    • Using a sample of 1.31 billion J/psi events accumulated with the BESIII detector at the BEPCII collider, we report the observation of the decay J/psi -> phi pi(0), which is the first evidence for a doubly Okubo-Zweig-Iizuka suppressed electromagnetic J/psi decay. A clear structure is observed in the K+K- mass spectrum around 1.02 GeV/c(2), which can be attributed to interference between J/psi -> phi pi(0) and J/psi -> K+K- pi(0) decays. Due to this interference, two possible solutions are found. The corresponding measured values of the branching fraction of J/psi -> phi pi(0) are [2.94 +/- 0.16(stat) +/- 0.16(syst)] x 10(-6) and [1.24 +/- 0.33(stat) +/- 0.30(syst)] x 10(-7).
  •  
47.
  • Ablikim, M., et al. (författare)
  • Observation of the Psi(1(3)D(2)) State in e(+)e(-) -> pi(+)pi(-)gamma chi(c1) at BESIII
  • 2015
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 115:1
  • Tidskriftsartikel (refereegranskat)abstract
    • We report the observation of the X(3823) state in the process e(+)e(-) -> pi(+)pi(-) X(3823) pi(+)pi(-)gamma chi(c1) with a statistical significance of 6.2 sigma, in data samples at center-of-mass energies root s = 4.230, 4.260, 4.360, 4.420, and 4.600 GeV collected with the BESIII detector at the BEPCII electron positron collider. The measured mass of the X(3823) state is (3821.7 +/- 1.3 +/- 0.7) MeV/c(2), where the first error is statistical and the second systematic, and the width is less than 16 MeV at the 90% confidence level. The products of the Born cross sections for e(+)e(-) -> pi(+)pi(-) X(3823) and the branching ratio B [X(3823) -> gamma X-c1c2] are also measured. These measurements are in good agreement with the assignment of the X(3823) state as the Psi(1(3)D(2)) charmonium state.
  •  
48.
  • Ablikim, M., et al. (författare)
  • Observation of Ψ(3686) → e+e-ΧcJ and ΧcJ → e+e-J/Ψ
  • 2017
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 118:22
  • Tidskriftsartikel (refereegranskat)abstract
    • Using 4.479 x 10(8) psi(3686) events collected with the BESIII detector, we search for the decays psi(3686) -> e(+)e(-)chi(cJ) and chi(cJ) -> e(+)e(-)J/psi, where J = 0, 1, 2. The decays psi(3686) -> e(+)e(-)chi(cJ) and chi(cJ) -> e(+)e(-)J/psi are observed for the first time. The measured branching fractions are B(psi(3686) -> e(+)e(-)chi(cJ)) = (11.7 +/- 2.5 +/- 1.0) x 10(-4), (8.6 +/- 0.3 +/- 0.6) x 10(-4), (6.9 +/- 0.5 +/- 0.6) x 10(-4) for J = 0, 1, 2, and B(chi(cJ) -> e(+)e(-)J/psi) = (1.51 +/- 0.30 +/- 0.13)x10(-4), (3.73 +/- 0.09 +/- 0.25)x10(-3), (2.48 +/- 0.08 +/- 0.16)x10(-3) for J = 0, 1, 2, respectively. The ratios of the branching fractions B(psi(3686) -> e(+)e(-)chi(cJ))/B(psi(3686) -> gamma chi(cJ)) and B(chi(cJ) -> e(+)e(-)J/psi)/B(chi(cJ) -> gamma J/psi) are also reported. Also, the alpha values of helicity angular distributions of the e(+)e(-) pair are determined for psi(3686) -> e(+)e(-)chi(c1,2) and chi(c1,2) -> e(+)e(-)J/psi.
  •  
49.
  • Ablikim, M., et al. (författare)
  • Precision measurement of the D*(0) decay branching fractions
  • 2015
  • Ingår i: Physical Review D. - 1550-7998 .- 1550-2368 .- 2470-0010. ; 91:3
  • Tidskriftsartikel (refereegranskat)abstract
    • Using 482 pb(-1) of data taken at root s = 4.009 GeV, we measure the branching fractions of the decays of D*(0) into D-0 pi(0) and D-0 gamma to be B(D*(0) -> D-0 pi(0)) = (65.5 +/- 0.8 +/- 0.5)% and B(D*(0) -> D0 gamma) = (34.5 +/- 0.8 +/- 0.5)%, respectively, by assuming that the D*(0) decays only into these two modes. The ratio of the two branching fractions is B(D*(0) -> D-0 pi(0))/B(D*(0) -> D-0 gamma) = 1.90 +/- 0.07 +/- 0.05, which is independent of the assumption made above. The first uncertainties are statistical and the second ones systematic. The precision is improved by a factor of 3 compared to the present world average values.
  •  
50.
  • Ablikim, M., et al. (författare)
  • Search for C-parity violation in J/psi -> gamma gamma and gamma phi
  • 2014
  • Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 90:9, s. 092002-
  • Tidskriftsartikel (refereegranskat)abstract
    • Using 1.06 x 10(8) psi(3686) events recorded in e(+)e(-) collisions at root s = 3.686 GeV with the BESIII at the BEPCII collider, we present searches for C-parity violation in J/psi -> gamma gamma and gamma phi decays via psi(3686) -> J/psi pi(+)pi(-). No significant signals are observed in either channel. Upper limits on the branching fractions are set to be B(J/psi -> gamma gamma) < 2.7 x 10(-7) and B(J/psi -> gamma phi) < 1.4 x 10(-6) at the 90% confidence level. The former is one order of magnitude more stringent than the previous upper limit, and the latter represents the first limit on this decay channel.
  •  
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