| 41. |
- 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-
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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.
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| 42. |
- Ablikim, M., et al.
(författare)
-
Observation of psi(3686) -> eta ' e(+)e(-)
- 2018
-
Ingår i: Physics Letters B. - : ELSEVIER SCIENCE BV. - 0370-2693 .- 1873-2445. ; 783, s. 452-458
-
Tidskriftsartikel (refereegranskat)abstract
- Using a data sample of 448.1 x 10(6) psi(3686) events collected with the BESIII detector at the BEPCII collider, we report the first observation of the electromagnetic Dalitz decay psi(3686) -> eta'e(+)e(-), with significances of 7.0 sigma and 6.3 sigma when reconstructing the eta' meson via its decay modes eta' -> gamma pi(+)pi(-) and eta' -> pi(+)pi(-) eta (eta -> gamma gamma), respectively. The weighted average branching fraction is determined to be B(psi(3686) -> eta'e(+)e(-)) = (1.90 +/- 0.25 +/- 0.11) x 10(-6), where the first uncertainty is statistical and the second systematic.
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| 43. |
- 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.
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| 44. |
- 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).
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| 45. |
- Ablikim, M., et al.
(författare)
-
Observation of the helicity-selection-rule suppressed decay of the χc2 charmonium state
- 2017
-
Ingår i: Physical Review D. - : AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 96:11
-
Tidskriftsartikel (refereegranskat)abstract
- The decays of chi(c2) -> K+K- pi(0), KSK +/-pi(-/+), and pi(+)pi(-)pi(0) are studied with the psi(3686) data samples collected with the Beijing Spectrometer ( BESIII). For the first time, the branching fractions of chi(c2) -> K*(K) over bar,chi(c2) -> a(2)(+/-)(1320)pi(-/+)/a(2)(0)(1320)pi(0), and chi(c2) -> rho(770)(+/-)pi(-/+) are measured. Here, K*(K) over bar denotes both K*K-+/-(-/+) and its isospin-conjugated process K*(0)(K) over bar (0) + c: c:, and K* denotes the resonances K*(892), K*(2)(1430), and K*(3)(1780). The observations indicate a strong violation of the helicity selection rule in chi(c2) decays into vector and pseudoscalar meson pairs. The measured branching fractions of chi(c2) -> K*(892)(K) over bar are more than ten times larger than the upper limit of chi(c2) -> rho(770)(+/-)pi(-/+), which is so far the first direct observation of a significant U-spin symmetry breaking effect in charmonium decays.
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| 46. |
- Ablikim, M., et al.
(författare)
-
Observation of the isospin-violating decay J/psi -> phi pi(0)f(0) (980)
- 2015
-
Ingår i: Physical Review D. - 1550-7998 .- 1550-2368. ; 92:1
-
Tidskriftsartikel (refereegranskat)abstract
- Using a sample of 1.31 x 10(9) J/psi events collected with the BESIII detector at the BEPCII collider, the decays J/psi -> phi pi(+)pi(-)pi(0) and J/psi -> phi pi(0)pi(0)pi(0) are investigated. The isospin- violating decay J/psi -> phi pi(0)f(0)(980) with f(0)(980)-> pi pi is observed for the first time. The width of the f(0)(980) obtained from the dipion mass spectrum is found to be much smaller than the world average value. In the pi(0)f(0)(980) mass spectrum, there is evidence of f(1)(1285) production. By studying the decay J/psi ->eta', the branching fractions of eta' -> pi(+)pi(-)pi(0) and eta' -> pi(0)pi(0)pi(0), as well as their ratio, are also measured.
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| 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.
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| 48. |
- Ablikim, M., et al.
(författare)
-
Observation of χc2→η′η′ and χc0,2→ηη′
- 2017
-
Ingår i: Physical Review D. - 2470-0010 .- 2470-0029. ; 96:11
-
Tidskriftsartikel (refereegranskat)abstract
- Using a sample of 448.1×106 ψ(3686) events collected with the BESIII detector in 2009 and 2012, we study the decays χc0,2→η′η′ and ηη′. The decays χc2→η′η′, χc0→ηη′ and χc2→ηη′ are observed for the first time with statistical significances of 9.6σ, 13.4σ and 7.5σ, respectively. The branching fractions are determined to be B(χc0→η′η′)=(2.19±0.03±0.14)×10−3, B(χc2→η′η′)=(4.76±0.56±0.38)×10−5, B(χc0→ηη′)=(8.92±0.84±0.65)×10−5 and B(χc2→ηη′)=(2.27±0.43±0.25)×10−5, where the first uncertainties are statistical and the second are systematic. The precision for the measurement of B(χc0→η′η′) is significantly improved compared to previous measurements. Based on the measured branching fractions, the role played by the doubly and singly Okubo-Zweig-Iizuka disconnected transition amplitudes for χc0,2 decays into pseudoscalar meson pairs can be clarified.
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| 49. |
- 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.
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| 50. |
- Ablikim, M., et al.
(författare)
-
Observation of ψ(3686)→n¯n and improved measurement of ψ(3686)→p¯p
- 2018
-
Ingår i: Physical Review D. - : AMER PHYSICAL SOC. - 2470-0010 .- 2470-0029. ; 98:3
-
Tidskriftsartikel (refereegranskat)abstract
- We observe the decay psi (3686) -> n (n) over bar for the first time and measure psi (3686) -> p (p) over bar with improved accuracy by using 1.07 x 10(8) psi (3686) events collected with the BESIII detector. The measured branching fractions are B(psi(3686) -> n (n) over bar) = (3.06 +/- 0.06 +/- 0.14) x 10(-4) and B(psi(3686) -> p (p) over bar) = (3.05 +/- 0.02 +/- 0.12) x 10(-4). Here, the first uncertainties are statistical, and the second ones are systematic. With the hypothesis that the polar angular distributions of the neutron and proton in the center-of-mass system obey 1 + alpha cos(2) theta, we determine the a parameters to be alpha(n (n) over bar) = 0.68 +/- 0.12 +/- 0.11 and alpha(p (p) over bar) = 1.03 +/- 0.06 +/- 0.03 for psi(3686) -> n (n) over bar and psi(3686) -> p (p) over bar, respectively.
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