Browsing by Author "Ablikim, M."

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Amplitude Analysis of the Decays η′ → π⁺π⁻π⁰ and η′ → π⁰π⁰π⁰
(American Physical Society, 2017-01-06) Ablikim, M.; Achasov, M. N.; Ai, X. C.; Albayrak, O.; Albrecht, M.; Ambrose, D. J.; Amoroso, A.; Lou, Xinchou; BESIII Collaboration; 0000-0003-0867-2189 (Lou, X); Lou, Xinchou
Based on a sample of 1.31 x 10⁹ J/ψ events collected with the BESIII detector, an amplitude analysis of the isospin-violating decays η′ → π⁺π⁻π⁰ and η′ → π⁰π⁰π⁰ is performed. A significant P-wave contribution from η′ → ρ^{±} π^{∓} is observed for the first time in η′ → π⁺π⁻π⁰. The branching fraction is determined to be ℬ(η′ → ρ^{±} π^{∓}) = (7.44 ± 0.60 ± 1.26 ± 1.84) x 10⁻⁴, where the first uncertainty is statistical, the second systematic, and the third model dependent. In addition to the nonresonant S-wave component, there is a significant σ meson component. The branching fractions of the combined S-wave components are determined to be ℬ(η′ → π⁺π⁻π⁰)s = (37.63 ± 0.77 ± 2.22 ± 4.48) x 10⁻⁴ and ℬ(η′ → π⁰π⁰π⁰) = (35.22 ± 0.82 ± 2.54) x 10⁻⁴, respectively. The latter one is consistent with previous BESIII measurements.
Amplitude Analysis of the π⁰π⁰ System Produced in Radiative J/ψ Decays
(American Physical Society, 2015-09-14) Ablikim, M.; Achasov, M. N.; Ai, X. C.; Albayrak, O.; Albrecht, M.; Ambrose, D. J.; Amoroso, A.; Lou, Xinchou (UT Dallas); 56366505900 (Lou, X); 250674117 (Izen, JM)
An amplitude analysis of the π⁰π⁰ system produced in radiative J/ψ decays is presented. In particular, a piecewise function that describes the dynamics of the π⁰π⁰ system is determined as a function of M(π⁰π⁰) from an analysis of the (1.311 ± 0.011) x 10⁹ J/ψ decays collected by the BESIII detector. The goal of this analysis is to provide a description of the scalar and tensor components of the π⁰π⁰ system while making minimal assumptions about the properties or number of poles in the amplitude. Such a model-independent description allows one to integrate these results with other related results from complementary reactions in the development of phenomenological models, which can then be used to directly fit experimental data to obtain parameters of interest. The branching fraction of J/ψ → π⁰π⁰ is determined to be (1.15 ± 0.05) x 10⁻³, where the uncertainty is systematic only and the statistical uncertainty is negligible.
Amplitude Analysis of the χ_{c1} → ηπ⁺π⁻ Decays
(2018-05-24) Ablikim, M.; Achasov, M. N.; Ahmed, S.; Ai, X. C.; Albayrak, O.; Albrecht, M.; Ambrose, D. J.; Lou, Xinchou; BESIII Collaboration; 0000-0003-0867-2189 (Lou, X); Lou, Xinchou
Using 448.0 x 10⁶ ψ(3686) events collected with the BESIII detector, an amplitude analysis is performed for ψ(3686)→γχ_{c1}, χ_{c1} → ηπ⁺π⁻ decays. The most dominant two-body structure observed is α₀(980)^± π^∓; α₀(980)^±→ηπ^±. The α₀(980) line shape is modeled using a dispersion relation, and a significant nonzero α₀(980) coupling to the η′π channel is measured. We observe χ_{c1} → α₂(1700)π production for the first time, with a significance larger than 17σ. The production of mesons with exotic quantum numbers, J^{PC} = 1⁻⁺, is investigated, and upper limits for the branching fractions χ_{c1}→π₁(1400)^±π^∓, χ_{c1} → π₁(1600)^±π^∓, and χ_{c1} → π₁(2015)^±π^∓, with subsequent π₁(X)^± → ηπ^± decay, are determined.
Branching Fraction Measurements of ψ(3686) → γχ_{cj}
(2018-05-24) Ablikim, M.; Achasov, M. N.; Albrecht, M.; Ahmed, S.; Amoroso, A.; An, F. F.; An, Q.; Lou, Xinchou; BESIII Collaboration; 0000-0003-0867-2189 (Lou, X); Lou, Xinchou
Using a sample of 106 million ψ(3686) decays, the branching fractions of ψ(3686) → γχ_{c0}, ψ(3686) → γχ_{c1}, and ψ(3686) → γχ_{c2} are measured with improved precision to be (9.389 ± 0.014 ± 0.332) %, (9.905 ± 0.011 ± 0.353) %, and (9.621 ± 0.013 ± 0.272) %, respectively, where the first uncertainties are statistical and the second ones are systematic. The product branching fractions of ψ(3686) → γχ_{c1}, χ_{c1} → γJ/ψ and ψ(3686) → γχ_{c2}, χ_{c2} → γJ/ψ and the branching fractions of χ_{c1} → γJ/ψ and χ_{c2} → γJ/ψ are also presented.
Dark Photon Search in the Mass Range between 1.5 and 3.4 GeV/c²
(Elsevier Science B.V., 2018-10-01) Ablikim, M.; Achasov, M. N.; Ai, X. C.; Albayrak, O.; Albrecht, M.; Ambrose, D. J.; Amoroso, A.; Lou, Xinchou; BESIII Collaboration; 0000-0003-0867-2189 (Lou, X); Lou, Xinchou
Using a data set of 2.93 fb⁻¹ taken at a center-of-mass energy √s = 3.773 GeV with the BESIII detector at the BEPCII collider, we perform a search for an extra U(1) gauge boson, also denoted as a dark photon. We examine the initial state radiation reactions e⁺e⁻ → e⁺e⁻γ(ISR) and e⁺e⁻ → μ⁺μ⁻γ(ISR) for this search, where the dark photon would appear as an enhancement in the invariant mass distribution of the leptonic pairs. We observe no obvious enhancement in the mass range between 1.5 and 3.4 GeV/c² and set a 90% confidence level upper limit on the mixing strength of the dark photon and the Standard Model photon. We obtain a competitive limit in the tested mass range.
Determination of the Number of ψ(3686) Events at BESIII
(Chinese Physical Soc) Ablikim, M.; Achasov, M. N.; Ai, X. C.; Ambrose, D. J.; Amoroso, A.; An, F. F.; An, Q.; Olsen, S. L.; BESIII Collaboration; Olsen, S. L.
The numbers of ψ(3686) events accumulated by the BESIII detector for the data taken during 2009 and 2012 are determined to be (107.0 ± 0.8) x10⁶ and (341.1 ± 2.1) x10⁶, respectively, by counting inclusive hadronic events, where the uncertainties are systematic and the statistical uncertainties are negligible. The number of events for the sample taken in 2009 is consistent with that of the previous measurement. The total number of ψ(3686) events for the two data taking periods is (448.1 ± 2.9) x 10⁶.
Determination of the Spin and Parity of the Z_c (3900)
(American Physical Society, 2017) Ablikim, M.; Achasov, M. N.; Ai, X. C.; Albayrak, O.; Albrecht, M.; Ambrose, D. J.; Amoroso, A.; Lou, Xinchou; 0000-0003-0867-2189 (Lou, X); Lou, Xinchou
The spin and parity of the Z_{c}(3900)^{±} state are determined to be J^{P} =1⁺ with a statistical significance larger than 7σ over other quantum numbers in a partial wave analysis of the process e⁺e⁻ → π⁺π⁻J/ψ. We use a data sample of 1.92 fb⁻¹ accumulated at √s̅=4.23 and 4.26 GeV with the BESIII experiment. When parametrizing the Z_{c}(3900)^{±} with a Flatté-like formula, we determine its pole mass M_{pole} = (3881.2 ± 4.2_{stat} ± 52.7_{syst}) MeV/c² and pole width Γ_{pole} = (51.8 ± 4.6_{stat} ± 36.0_{syst}) MeV. We also measure cross sections for the process e⁺e⁻→ Z_{c}(3900)^{±}π⁻ + c.c.→ J/ψπ⁺π⁻ and determine an upper limit at the 90% confidence level for the process e⁺e⁻→ Z_{c}(4020)^{±}π⁻ + c.c.→J/ψπ⁺π⁻
Evidence for the Singly Cabibbo Suppressed Decay Λ_c⁺ → pη and Search for Λc+ →pπ⁰
(2018-05-24) Ablikim, M.; Achasov, M. N.; Ahmed, S.; Ai, X. C.; Albayrak, O.; Albrecht, M.; Ambrose, D. J.; Lou, Xinchou; BESIII Collaboration; 0000-0003-0867-2189 (Lou, X); Lou, Xinchou
We study the singly Cabibbo suppressed decays Λ_c⁺ → pη and Λ_c⁺ → pπ⁰ using Λ_c⁺Λ̅_c⁻ pairs produced by e⁺e⁻ collisions at a center-of-mass energy of √s̅ = 4.6 GeV. The data sample was collected by the BESIII detector at the BEPCII collider and corresponds to an integrated luminosity of 567 pb⁻¹. We find the first evidence for the decay Λ_c⁺ → pη with a statistical significance of 4.2σ and measure its branching fraction to be ℬ(Λ_c⁺ → pη) = (1.24 ± 0.28(stat) ± 0.10(syst)) x 10⁻³. No significant Λ_c⁺ → pπ⁰ signal is observed. We set an upper limit on its branching fraction ℬ(Λ_c⁺ → pπ⁰) < 2.7 x 10⁻⁴ at the 90% confidence level.
Evidence of Two Resonant Structures in e⁺e⁻ → π⁺π⁻h_c
(American Physical Society, 2017-03-01) Ablikim, M.; Achasov, M. N.; Ahmed, S.; Ai, X. C.; Albayrak, O.; Albrecht, M.; Ambrose, D. J.; Lou, Xinchou; BESIII Collaboration; 0000-0003-0867-2189 (Lou, X); Lou, Xinchou
The cross sections of e⁺e⁻ → π⁺π⁻h_c at center-of-mass energies from 3.896 to 4.600 GeV are measured using data samples collected with the BESIII detector operating at the Beijing Electron Positron Collider. The cross sections are found to be of the same order of magnitude as those of e⁺e⁻→ π⁺π⁻J/ψ and e⁺e⁻ → π⁺π⁻ψ(2S), but the line shape is inconsistent with the Y states observed in the latter two modes. Two structures are observed in the e⁺e⁻ → π⁺π⁻h_c cross sections around 4.22 and 4.39 GeV/c², which we call Y(4220) and Y(4390), respectively. A fit with a coherent sum of two Breit-Wigner functions results in a mass of (4218.4_{-4.5}^{+5.5} ± 0.9) MeV/c² and a width of (66.0_{-8.3}^{+12.3} ± 0.4) MeV for the Y(4220), and a mass of (4391.5_{-6.8}^{+6.3} ± 1.0) MeV/c² and a width of (139.5_{-20.6}^{+16.2} ± 0.6) MeV for the Y(4390), where the first uncertainties are statistical and the second ones systematic. The statistical significance of Y(4220) and Y(4390) is 10σ over one structure assumption. .
An Improved Limit for Γ_{ee} of X(3872) and Γ_{ee} Measurement of ψ(3686)
(Elsevier, 2015-08-07) Ablikim, M.; Achasov, M. N.; Ai, X. C.; Albayrak, O.; Albrecht, M.; Ambrose, D. J.; Amoroso, A.; Lou, Xinchou; BESIII Collaboration; 0000-0003-0867-2189 (Lou, X); Lou, Xinchou
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⁻→ γ(ISR}X(3872) → γ{ISR}π⁺π⁻J/ψ via the Initial State Radiation technique. The production of a resonance with quantum numbers JPC=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 Γ{ee} ^{X(3872)} ℬ(X(3872) → π⁺π⁻J/ψ) < 0.13 eV at 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 ψ(3686) to be Γ {ee} ^{ψ(3686)} = 2213 ± 18{stat} ± 99{sys} eV. © 2015 The Authors.
Improved Measurements of Branching Fractions for η_c → φφ and ωφ
(Amer Physical Soc, 2017-05-11) Ablikim, M.; Achasov, M. N.; Ai, X. C.; Albayrak, O.; Albrecht, M.; Ambrose, D. J.; Amoroso, A.; Lou, Xinchou; BESIII Collaboration; 0000-0003-0867-2189 (Lou, X); Lou, Xinchou
Using (223.7 ± 1.4) x 10⁶ J/ψ events accumulated with the BESIII detector, we study η_c decays to φφ and ωφ final states. The branching fraction of η_c → φφ is measured to be Br(η_c → φφ) = (2.5 ± 0.3_{-0.7}^{+0.3} ± 0.6) X 10⁻³, where the first uncertainty is statistical, the second is systematic, and the third is from the uncertainty of Br(J/ψ → γη_c). No significant signal for the double Okubo-Zweig-Iizuka suppressed decay of η_c → ωϕ is observed, and the upper limit on the branching fraction is determined to be Br(η_c → ωϕ) < 2.5 × 10⁻⁴ at the 90% confidence level.
Improved Measurements of Two-Photon Widths of The χ(cJ) States and Helicity Analysis For χ(c2) → γγ
(Amer Physical Soc, 2018-10-01) Ablikim, M.; Achasov, M. N.; Ahmed, S.; Albrecht, M.; Amoroso, A.; An, F. F.; An, Q.; Lou, Xinchou; BESIII Collaboration; 0000-0003-0867-2189 (Lou, X); Lou, Xinchou
Based on 448.1 x 10⁶ ψ(3686) events collected with the BESIII detector, the decays ψ(3686) → γ χ(cJ), χ(cJ) → γγ(J = 0, 1, 2) are studied. The decay branching fractions of χ(c0,2) → γγ are measured to be ℬ(χ(c0) → γγ) = (1.93 ± 0.08 ± 0.05 ± 0.05) x 10⁻⁴ and ℬ(χ(c2) → γγ) = (3.10 ± 0.09 ± 0.07 ± 0.11) x 10⁻⁴ which correspond to two-photon decay widths of Γ(γγ)(χ(c0)) = 2.03 ± 0.08 ± 0.06 ± 0.13 keV and Γ(γγ)(χ(c2)) = 0.60 ± 0.02 ± 0.01 ± 0.04 keV with a ratio of R = Γ(γγ)(χ(c2))/Γ(γγ)(χ(c0)) = 0.295 ± 0.014 ± 0.007 ± 0.027, where the uncertainties are statistical, systematic and associated with the uncertainties of ℬ(ψ(3686) → γχ(c2)) and the total widths Γχ(c0,2), respectively. For the forbidden decay of χ(c1) → γγ, no signal is observed, and an upper limit on the two-photon width is obtained to be Γ(γγ)(χ(c1)) < 5.3 eV at the 90% confidence level. The ratio of the two-photon widths between helicity-zero and helicity-two components in the decay χ(c2) → γγ is also measured to be f(0/2) = Γ(γγ)(λ=0) (χ(c2)) / Γ(γγ)(λ=2) (χ(c2) = (0.0 ± 0.6 ± 1.2) x 10(-2), where the uncertainties are statistical and systematic, respectively.
Luminosity Measurements for the R Scan Experiment at BESIII
(Chinese Physical Soc, 2017-06) Ablikim, M.; Achasov, M. N.; Ahmed, S.; Ai, X. C.; Albayrak, O.; Albrecht, M.; Ambrose, D. J.; Lou, Xinchou; BESIII Collaboration; 0000-0003-0867-2189 (Lou, X); Lou, Xinchou
By analyzing the large-angle Bhabha scattering events e⁺e⁻ → (γ)e⁺e⁻ and diphoton events e⁺e⁻ → (γ)γγ for the data sets collected at center-of-mass (c.m.) energies between 2.2324 and 4.5900 GeV (131 energy points in total) with the upgraded Beijing Spectrometer (BESIII) at the Beijing Electron-Positron Collider (BEPCII), the integrated luminosities have been measured at the different c.m. energies, individually. The results are important inputs for the R value and J/ψ resonance parameter measurements.
Measurement of Azimuthal Asymmetries in Inclusive Charged Dipion Production in e⁺e⁻ Annihilations at √s̅ = 3.65 GeV
(Amer Physical Soc, 2016-01-27) Ablikim, M.; Achasov, M. N.; Ai, X. C.; Albayrak, O.; Albrecht, M.; Ambrose, D. J.; Amoroso, A.; Lou, Xinchou; BESIII Collaboration; 0000-0003-0867-2189 (Lou, X); Lou, Xinchou
We present a measurement of the azimuthal asymmetries of two charged pions in the inclusive process e⁺e⁻ → ππΧ based on a data set of 62 pb⁻¹ at the center-of-mass energy of 3.65 GeV collected with the SESIII detector. These asymmetries can be attributed to the Collins fragmentation function. We observe a nonzero asymmetry, which increases with increasing pion momentum. As our energy scale is close to that of the existing semi-inclusive deep inelastic scattering experimental data, the measured asymmetries are important inputs for the global analysis of extracting the quark transversity distribution inside the nucleon and are valuable to explore the energy evolution of the spin-dependent fragmentation function.
Measurement of Cross Sections of the Interactions e⁺e⁻ → φφω and e⁺e⁻ → φφφ at Center-Of-Mass Energies from 4.008 to 4.600 GeV
(Elsevier Science B.V., 2018-10-01) Ablikim, M.; Achasov, M. N.; Ahmed, S.; Ai, X. C.; Albayrak, O.; Albrecht, M.; Ambrose, D. J.; Lou, Xinchou; BESIII Collaboration; 0000-0003-0867-2189 (Lou, X); Lou, Xinchou
Using data samples collected with the BESIII detector at the BEPCII collider at six center-of-mass energies between 4.008 and 4.600 GeV, we observe the processes e⁺e⁻ → φφω and e⁺e⁻ → φφφ. The Born cross sections are measured and the ratio of the cross sections σ(e⁺e⁻ → φφω)/σ(e⁺e⁻ → φφφ) is estimated to be 1.75 ± 0.22 ± 0.19 averaged over six energy points, where the first uncertainty is statistical and the second is systematic. The results represent first measurements of these interactions.
Measurement of the Absolute Branching Fraction for Λ_c⁺ → Λe⁺ν_e
(Amer Physical Soc, 2015-11-25) Ablikim, M.; Achasov, M. N.; Ai, X. C.; Albayrak, O.; Albrecht, M.; Ambrose, D. J.; Amoroso, A.; Lou, Xinchou; BESIII Collaboration; 56366505900 (Lou, X); Lou, Xinchou
We report the first measurement of the absolute branching fraction for Λ_c⁺. This measurement is based on 567 pb⁻¹ of e⁺e⁻ annihilation data produced at √s = 4.599 GeV, which is just above the Λ_c⁺ Λ̅_c̅ threshold. The data were collected with the BESIII detector at the BEPCII storage rings. The branching fraction is determined to be ℬ(Λ_c⁺ → Λe⁺ν_e) = [3.63 ± 0.38(stat) ± 0.20(syst)]%, representing a significant improvement in precision over the current indirect determination. As the branching fraction for Λ_c⁺ → Λe⁺ν_e is the benchmark for those of other Λ_c⁺ semileptonic channels, our result provides a unique test of different theoretical models, which is the most stringent to date.
Measurement of the Absolute Branching Fraction for Λ_c⁺ → Λμ⁺ν_μ
(2018-06-01) Ablikim, M.; Achasov, M. N.; Ahmed, S.; Ai, X. C.; Albayrak, O.; Albrecht, M.; Ambrose, D. J.; Lou, Xinchou; BESIII Collaboration; 0000-0003-0867-2189 (Lou, X); Lou, Xinchou
We report the first measurement of the absolute branching fraction for Λ_c⁺ → Λμ⁺ν_μ. This measurement is based on a sample of e⁺e⁻ annihilation data produced at a center-of-mass energy √s̅ = 4.6 GeV, collected with the BESIII detector at the BEPCII storage rings. The sample corresponds to an integrated luminosity of 567 pb⁻¹. The branching fraction is determined to be ℬ(Λ_c⁺ → Λμ⁺ν_μ) = (3.49 ± 0.46(stat) ± 0.27(syst))%. In addition, we calculate the ratio ℬ(Λ_c⁺ → Λμ⁺ν_μ) / ℬ(Λ_c⁺ → Λe⁺ν_e) to be 0.96 ± 0.16(stat) ± 0.04(syst).
Measurement of the Branching Fraction for ψ(3770) → γχ_{c0}
(Elsevier Science BV, 2016-02-10) Ablikim, M.; Achasov, M. N.; Ai, X. C.; Albayrak, O.; Albrecht, M.; Ambrose, D. J.; Amoroso, A.; Lou, Xinchou; BESIII Collaboration; 0000-0003-0867-2189 (Lou, X); Lou, Xinchou
By analyzing a data set of 2.92 fb⁻¹ of e⁺e⁻ collision data taken at √s̅ = 3.773 GeV and 106.41 x 10⁻⁶ ψ3686) decays taken at √s̅ = 3.686 GeV with the BESIII detector at the BEPCII collider, we measure the branching fraction and the partial decay width for ψ3770) → γχ(c0) to be B(ψ(3770) → γχ(c0)) = (6.88 ± 0.28 ± 0.67) x 10⁻³ and Γ[ψ(3770) → γχ(c0)] = (187 ± 8 ± 19) keV, respectively. These are the most precise measurements to date.
Measurement of the Branching Fractions D_s⁺ → η′Χ and D_s^+ → η′ρ⁺ in e⁺e⁻ → D_s^+D_s^-
(Elsevier B.V., 2015-11-27) Ablikim, M.; Achasov, M. N.; Ai, X. C.; Albayrak, O.; Albrecht, M.; Ambrose, D. J.; Amoroso, A.; Lou, Xinchou; BESII Collaboration; 56366505900 (Lou, X); Lou, Xinchou
We study D_s⁺ decays to final states involving the η' with a 482 pb⁻¹ data sample collected at √s = 4.009 GeV with the BESIII detector at the BEPCII collider. We measure the branching fractions ℬ(D_s⁺ → η'Χ) = (8.8 ± 1.8 ± 0.5)% and ℬ(D_s⁺ → η'ρ⁺) = (5.8 ± 1.4 ± 0.4)% where the first uncertainty is statistical and the second is systematic. In addition, we estimate an upper limit on the non-resonant branching ratio ℬ(D_s⁺ → η'π⁺π⁰) < 5.1% at the 90% confidence level. Our results are consistent with CLEO's recent measurements and help to resolve the disagreement between the theoretical prediction and CLEO's previous measurement of ℬ(D_s⁺ → η'ρ⁺).
Measurement of the e⁺e⁻ → ηJ/ψ Cross Section and Search for e⁺e⁻ → π⁰J/ψ at Center-Of-Mass Energies Between 3.810 and 4.600 GeV
(Amer Physical Soc, 2015-06-09) Ablikim, M.; Achasov, M. N.; Ai, X. C.; Albayrak, O.; Albrecht, M.; Ambrose, D. J.; Amoroso, A.; Lou, Xinchou; BESIII Collaboration; 0000-0003-0867-2189 (Lou, X); Lou, Xinchou
Using data samples collected with the BESIII detector operating at the BEPCII collider at 17 center-of-mass energies from 3.810 to 4.600 GeV, we perform a study of e⁺e⁻ → ηJ/ψ and π⁰J/ψ The Born cross sections of these two processes are measured at each center-of-mass energy. The measured energy-dependent Born cross section for e⁺e⁻ → ηJ/ψ shows an enhancement around 4.2 GeV. The measurement is compatible with an earlier measurement by Belle.