The cross sections for D ⁰ D̄ ⁰ and D ⁺ D ^- production at 3.773 GeV have been measured with BES-II detector at BEPC. These measurements are made by analyzing a data sample of about 17.3 pb ^-1 collected at the center-of-mass energy of 3.773 GeV. Observed cross sections for the charm pair production are radiatively corrected to obtain the tree level cross section for DD̄ production. A measurement of the total tree level hadronic cross section is obtained from the tree level DD̄ cross section and an extrapolation of the R uds below the open charm threshold. © 2004 Elsevier B.V. All rights reserved.

Ablikim M.;Bai J. Z.;Bian J. G.;Cai X.;Chang J. F.;Chen H. S.;Chen H. X.;Chen J. C.;Jin C.;Chen M. L.;Chen Y. B.;Chu Y. P.

Physics Letters Section B Nuclear Elementary Particle and High Energy Physics

2004

New data are presented on J/ψ→ωK ⁺ K ^- from a sample of 58M J/ψ events in the upgraded BES II detector at the BEPC. There is a conspicuous signal for f 0 (1710)→K ⁺ K ^- and a peak at higher mass which may be fitted with f 2 (2150)→KK̄. From a combined analysis with ωπ ⁺ π ^- data, the branching ratio BR(f 0 (1710)→ππ)/BR(f 0 (1710)→KK̄) is <0.11 at the 95% confidence level. © 2004 Elsevier B.V. All rights reserved.

Ablikim M.;Bai J. Z.;Bian J. G.;Cai X.;Chang J. F.;Chen H. S.;Chen H. X.;Chen J. C.;Jin C.;Chen M. L.;Chen Y. B.;Chu Y. P.

Physics Letters Section B Nuclear Elementary Particle and High Energy Physics

2004

The observation of decay ψ(2S) → K S⁰ K L⁰ using ψ(2S) was discussed. It was found that the branching fraction was B(ψ(2S) → K S⁰ K L⁾ ). The effect of the requirement on the total energy of the photon candidates was checked with J/ψ → K S⁰ K L⁰ . It was observed that the results together with the branching fraction of ψ(2S) decays to other pseudosecular meson pairs (π ⁺ π ^- and K ⁺ K ^- were used to analyze the relative phase between three-gluon and the one photon annihilation amplitudes of ψ(2S) decays.

Bai J. Z.;Bian J. G.;Cai X.;Chang J. F.;Chen H. S.;Chen H. X.;Chen J.;Chen J. C.;Chen M. L.;Chen Y. B.;Chi S. P.;Chu Y. P.

Physical Review Letters

2004

The processes ψ(2S) → I π ⁺ π ⁻ , γK ⁺ K ⁻ , and γpp ^¯ have been studied using a sample of 3.79 × 10 ⁶ ψ(2S) decays. We determine the total width of the χ ^c0 to be γ ^tot χ c0 = 14.3 ± 2.0 ± 3.0 MeV. We present the first measurement of the branching fraction B(χ c0 → pp ¯ ) = (15.9 ± 4.3 ± 5.3) × 10 ⁻⁵ , where the first error is statistical and the second one is systematic. Branching fractions of χ c0, 2 → π ⁺ π − and K ⁺ K ⁻ are also reported. © 1998 American Physical Society.

Bai J. Z.;Bian J. G.;Chai Z. W.;Chen G. P.;Chen J. C.;Chen Y.;Chen Y. B.;Chen Y. Q.;Cheng B. S.;Cui X. Z.;Ding H. L.;Ding L. Y.

Physical Review Letters

1998

Using a sample of 3.8 M ψ(2S) events accumulated with the BES detector, the process ψ(2S) →π ⁺ π ^- J/ψ is studied. The angular distributions are compared with the general decay amplitude analysis of Cahn. We find that the dipion system requires some D wave amplitude, as well as S wave. On the other hand, the J/ψ-(π ⁺ π ^- ) relative angular momentum is consistent with being pure S wave. The decay distributions have been fit to heavy quarkonium models, including the Novikov-Shifman model. This model, which is written in terms of the parameter κ, predicts that D wave pions should be present. We determine κ=0.183 ±0.002±0.003 based on the joint m ππ -cos θ π * distribution. The fraction of D wave amplitude as a function of m ππ is found to decrease with increasing m ππ , in agreement with the model. We have also fit the Mannel-Yan model, which is another model that allows D wave pions. ©2000 The American Physical Society.

Bai J. Z.;Bian J. G.;Chen G. P.;Chen J. C.;Chen Y.;Chen Y. B.;Chen Y. Q.;Cheng B. S.;Cui X. Z.;Ding H. L.;Dong L. Y.;Du Z. Z.

Physical Review D Particles Fields Gravitation and Cosmology

2000

In a sample of 7.8 million J/ψ decays collected in the Beijing Spectrometer, the process J/ψ→γη c is observed for five different η c decay channels: K ⁺ K ^- π ⁺ π ^- , π ⁺ π ^- π ⁺ π ^- , K±K S⁰ π∓ (with K S⁰ →π ⁺ π ^- ), φφ (with φ→K ⁺ K ^- ) and K ⁺ K ^- π ⁰ . From these signals, we determine the mass of η c to be 2976.6±2.9 ±1.3 MeV. Combining this result with a previously reported result from a similar study using ψ(2S)→γη c detected in the same spectrometer gives m ηc =2976.3±2.3±1.2 MeV. For the combined samples, we obtain Γ ηc =11.0±8.1±4.1 MeV. ©2000 The American Physical Society.

Bai J. Z.;Bian J. G.;Chen A. D.;Chen G. P.;Chen H. S.;Chen J. C.;Chen X. D.;Chen Y.;Chen Y. B.;Cheng B. S.;Cui X. Z.;Ding H. L.

Physical Review D Particles Fields Gravitation and Cosmology

2000

Hadronic decays of the P-wave spin-triplet charmonium states χ cJ (J=0,1,2) are studied using a sample of ψ(2S) decays collected by the BES detector operating at the BEPC storage ring. Branching fractions for the decays χ c1 →K s⁰ K ⁺ π ^- +c.c., χ c0 →K s⁰ K s⁰ , χ c2 →K s⁰ K s⁰ , χ c0 →φφ, χ c2 →φφ and χ cJ →K ⁺ K ^- K ⁺ K ^- are measured for the first time, and those for χ cJ →π ⁺ π ^- π ⁺ π ^- , χ cJ →π ⁺ π ^- K ⁺ K ^- , χ cJ →π ⁺ π ^- pp̄ and χ cJ →3(π ⁺ π ^- ) are measured with improved precision. In addition, we determine the masses of the χ c0 and η c to be M χc0 =3414.1±0.6(stat)±0.8(syst) MeV and M ηc =2975.8±3.9(stat)±1.2(syst) MeV. ©1999 The American Physical Society.

Bai J. Z.;Bian J. G.;Chen G. P.;Chen J. C.;Chen Y.;Chen Y. B.;Chen Y. Q.;Cheng B. S.;Cui X. Z.;Ding H. L.;Dong L. Y.;Du Z. Z.

Physical Review D Particles Fields Gravitation and Cosmology

1999

The first measurement of B(D ⁰ →φX ⁰ ) and an upper limit for B(D ⁺ →φX ⁺ ) are determined from 22.3 pb ^-1 of e ⁺ e ^- annihilation data at a c.m. energy of 4.03 GeV. The data were recorded by the Beijing Spectrometer (BES) at BEPC. A recoil charge method is applied to charm threshold data to determine the charge of the D meson in the recoil from 9054±309±416 reconstructed D ⁰ , D ⁺ mesons. The branching fractions B(D ⁰ →φX ⁰ )=(1.71 -0.71^+0.76 ±0.17)%, and B(D ⁺ →φX ⁺ )<1.8% are determined from 10 events with a reconstructed D and a recoiling φ. In addition, a 90% C.L. upper limit of B(D ⁺ →φe ⁺ X ⁰ )<1.6% is determined from a search for semileptonic decays of the D ⁺ . ©2000 The American Physical Society.

Bai J. Z.;Bian J. G.;Chen G. P.;Chen J. C.;Chen Y.;Chen Y. B.;Chen Y. Q.;Cheng B. S.;Cui X. Z.;Ding H. L.;Dong L. Y.;Du Z. Z.

Physical Review D Particles Fields Gravitation and Cosmology

2000

The absolute branching fraction for the decay D ⁺ →K̄ ⁰ e ⁺ ν e is determined using 5321±149±160 singly tagged D ^- event sample from the data collected around 3.773 GeV with the BES-II detector at the BEPC collider. In the system recoiling against the singly tagged D ^- mesons, 34.4±6.1 events for D ⁺ →K̄ ⁰ e ⁺ ν e are observed. Those yield the absolute branching fraction to be BF(D ⁺ →K̄ ⁰ e ⁺ ν e )=(8.95±1.59±0.67)%. The ratio of the two partial widths for the decays of D ⁰ →K ^- e ⁺ ν e and D ⁺ →K̄ ⁰ e ⁺ ν e is determined to be Γ(D ⁰ →K ^- e ⁺ ν e ) /Γ(D ⁺ →K̄ ⁰ e ⁺ ν e )=1. 08±0.22±0.07. © 2004 Elsevier B.V. All rights reserved.

Ablikim M.;Bai J. Z.;Bian J. G.;Cai X.;Chang J. F.;Chen H. S.;Chen H. X.;Chen J. C.;Chen Jin;Chen M. L.;Chen Y. B.;Chu Y. P.

Physics Letters Section B Nuclear Elementary Particle and High Energy Physics

2005

A partial wave analysis is presented of J/ψ→φπ ⁺ π ^- and φK ⁺ K ^- from a sample of 58M J/ψ events in the BES II detector. The f 0 (980) is observed clearly in both sets of data, and parameters of the Flatté formula are determined accurately: M=965±8(stat)±6(syst)MeV/c ² , g 1 =165±10±15MeV/c ² , g 2 /g 1 =4.21±0.25±0.21. The φππ data also exhibit a strong ππ peak centred at M=1335MeV/c ² . It may be fitted with f 2 (1270) and a dominant 0 ⁺ signal made from f 0 (1370) interfering with a smaller f 0 (1500) component. There is evidence that the f 0 (1370) signal is resonant, from interference with f 2 (1270). There is also a state in ππ with M=1790 -30⁺⁴⁰ MeV/c ² and Γ=270 -30⁺⁶⁰ MeV/c ² ; spin 0 is preferred over spin 2. This state, f 0 (1790), is distinct from f 0 (1710). The φKK̄ data contain a strong peak due to f 2 ′(1525). A shoulder on its upper side may be fitted by interference between f 0 (1500) and f 0 (1710). © 2004 Elsevier B.V. All rights reserved.

Ablikim M.;Bai J. Z.;Bian J. G.;Cai X.;Chang J. F.;Chen H. S.;Chen H. X.;Chen J. C.;Chen Jin;Chen M. L.;Chen Y. B.;Chu Y. P.

Physics Letters Section B Nuclear Elementary Particle and High Energy Physics

2005