121 research outputs found
Direct Measurements of the Branching Fractions for and and Determinations of the Form Factors and
The absolute branching fractions for the decays and
are determined using singly
tagged sample from the data collected around 3.773 GeV with the
BES-II detector at the BEPC. In the system recoiling against the singly tagged
meson, events for and events for decays are observed. Those yield
the absolute branching fractions to be and . The
vector form factors are determined to be
and . The ratio of the two form
factors is measured to be .Comment: 6 pages, 5 figure
The pole in
Using a sample of 58 million events recorded in the BESII detector,
the decay is studied. There are conspicuous
and signals. At low mass, a large
broad peak due to the is observed, and its pole position is determined
to be - MeV from the mean of six analyses.
The errors are dominated by the systematic errors.Comment: 15 pages, 6 figures, submitted to PL
Search for the Lepton Flavor Violation Processes and
The lepton flavor violation processes and are
searched for using a sample of 5.8 events collected with
the BESII detector. Zero and one candidate events, consistent with the
estimated background, are observed in and
decays, respectively. Upper limits on the branching ratios are determined to be
and at the 90% confidence level (C.L.).Comment: 9 pages, 2 figure
Observation of the decay \psip\rar\kstark
Using 14 million events collected with the BESII detector,
branching fractions of \psip\rar\kstarkpm and \kstarknn are determined to
be: \calB(\psip\rar\kstarkpm)=(2.9^{+1.3}_{-1.7}\pm0.4)\times 10^{-5} and
\calB(\psip\rar\kstarknn)=(13.3^{+2.4}_{-2.7}\pm1.9)\times 10^{-5}. The
results confirm the violation of the "12%" rule for these two decay channels
with higher precision. A large isospin violation between the charged and
neutral modes is observed.Comment: 5 pages, 3 figure
Measurements of decays into Vector- Tensor final states
Decays of the into vector plus tensor meson final states have been
studied with 14 million events collected with the BESII detector.
Branching fractions of \psi(2S) \rt \omega f_{2}(1270), ,
and are
determined. They improve upon previous BESI results and confirm the violation
of the "12%" rule for decays to VT channels with higher precision.Comment: 7 pages, 7 figures and 2 table
Heavy quarkonium: progress, puzzles, and opportunities
A golden age for heavy quarkonium physics dawned a decade ago, initiated by
the confluence of exciting advances in quantum chromodynamics (QCD) and an
explosion of related experimental activity. The early years of this period were
chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in
2004, which presented a comprehensive review of the status of the field at that
time and provided specific recommendations for further progress. However, the
broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles
could only be partially anticipated. Since the release of the YR, the BESII
program concluded only to give birth to BESIII; the -factories and CLEO-c
flourished; quarkonium production and polarization measurements at HERA and the
Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the
deconfinement regime. All these experiments leave legacies of quality,
precision, and unsolved mysteries for quarkonium physics, and therefore beg for
continuing investigations. The plethora of newly-found quarkonium-like states
unleashed a flood of theoretical investigations into new forms of matter such
as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the
spectroscopy, decays, production, and in-medium behavior of c\bar{c}, b\bar{b},
and b\bar{c} bound states have been shown to validate some theoretical
approaches to QCD and highlight lack of quantitative success for others. The
intriguing details of quarkonium suppression in heavy-ion collisions that have
emerged from RHIC have elevated the importance of separating hot- and
cold-nuclear-matter effects in quark-gluon plasma studies. This review
systematically addresses all these matters and concludes by prioritizing
directions for ongoing and future efforts.Comment: 182 pages, 112 figures. Editors: N. Brambilla, S. Eidelman, B. K.
Heltsley, R. Vogt. Section Coordinators: G. T. Bodwin, E. Eichten, A. D.
Frawley, A. B. Meyer, R. E. Mitchell, V. Papadimitriou, P. Petreczky, A. A.
Petrov, P. Robbe, A. Vair
Measurement of Branching Ratios for Hadronic Decays
In a sample of 58 million events collected with the BES II detector,
the process J/ is observed in five decay channels: , , (with
), (with ) and . From
these signals, we determine ,
, ,
and .Comment: 8 pages, 1 figures and 4 table. Submitted to Phys. Lett.
Measurements of J/psi --> p \bar{p}
The process J/\psi --> p \bar{p} is studied using 57.7 X 10^6 J/\psi events
collected with the BESII detector at the Beijing Electron Positron Collider.
The branching ratio is determined to be Br(J/\psi --> p \bar{p})=(2.26 +- 0.01
+- 0.14) X 10^{-3}, and the angular distribution is well described by
\frac{dN}{d cos\theta_p}=1+\alpha\cos^2\theta_p with \alpha = 0.676 +- 0.036 +-
0.042, where \theta_p is the angle between the proton and beam directions. The
value of \alpha obtained is in good agreement with the predictions of
first-order QCD.Comment: 6 pages, 2 figures, RevTex4, Submitted to Phys.Lett.
Search for K_S K_S in J/psi and psi(2S) decays
The CP violating processes J/psi-->K_S K_S and psi(2S)-->K_S K_S are searched
for using samples of 58 million J/psi and 14 million psi(2S) events collected
with the Beijing Spectrometer at the Beijing Electron Positron Collider. No
signal is observed, and upper limits on the decay branching ratios are
determined to be BR(J/psi-->K_S K_S) K_S K_S) <
4.6x10^{-6} at the 95% confidence level.Comment: 6 pages, 4 figures, submitted to Phys. Lett.
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