3,587 research outputs found
Measurement of decay rate and parameters at KEDR
Using the inclusive photon spectrum based on a data sample collected at the
peak with the KEDR detector at the VEPP-4M collider, we
measured the rate of the radiative decay as well
as mass and width. Taking into account an asymmetric photon
lineshape we obtained keV, MeV/, MeV.Comment: 6 pages, 3 figure
Precise measurement of and between 1.84 and 3.72 GeV at the KEDR detector
The present work continues a series of the KEDR measurements of the value
that started in 2010 at the VEPP-4M collider. By combining new data
with our previous results in this energy range we measured the values of
and at nine center-of-mass energies between 3.08 and 3.72
GeV. The total accuracy is about or better than at most of energy
points with a systematic uncertainty of about . Together with the
previous precise measurement at KEDR in the energy range 1.84-3.05 GeV, it
constitutes the most detailed high-precision measurement near the
charmonium production threshold.Comment: arXiv admin note: text overlap with arXiv:1610.02827 and substantial
text overlap with arXiv:1510.0266
Measurement of J/psi to eta_c gamma at KEDR
We present a study of the inclusive photon spectra from 5.9 million J/psi
decays collected with the KEDR detector at the VEPP-4M e+e- collider. We
measure the branching fraction of radiative decay J/psi to eta_c gamma, eta_c
width and mass. Our preliminary results are: M(eta_c) = 2979.4+-1.5+-1.9 MeV,
G(eta_c) = 27.8+-5.1+-3.3 MeV, B(J/psi to eta_c gamma) = (2.34+-0.15+-0.40)%.Comment: To be published in Proceedings of the PhiPsi09, Oct. 13-16, 2009,
Beijing, Chin
Measurement of B(J/psi->eta_c gamma) at KEDR
We present a study of the inclusive photon spectrum from 6.3 million J/psi
decays collected with the KEDR detector at the VEPP-4M e+e- collider. We
measure the branching fraction of the radiative decay J/psi -> eta_c gamma,
eta_c width and mass. Taking into account an asymmetric photon line shape we
obtain: M(eta_c) = (2978.1 +- 1.4 +- 2.0) MeV/c^2, Gamma(eta_c) = (43.5 +- 5.4
+- 15.8) MeV, B(J/psi->eta_c gamma) = (2.59 +- 0.16 +- 0.31)%$.Comment: 6 pages, 1 figure. To be published in the proceedings of the 4th
International Workshop on Charm Physics (Charm2010), October 21-24, 2010,
IHEP, Beijin
Recommended from our members
Measurement of B(B-->X_s {\gamma}), the B-->X_s {\gamma} photon energy spectrum, and the direct CP asymmetry in B-->X_{s+d} {\gamma} decays
The photon spectrum in B --> X_s {\gamma} decay, where X_s is any strange
hadronic state, is studied using a data sample of (382.8\pm 4.2) \times 10^6
e^+ e^- --> \Upsilon(4S) --> BBbar events collected by the BABAR experiment at
the PEP-II collider. The spectrum is used to measure the branching fraction B(B
--> X_s \gamma) = (3.21 \pm 0.15 \pm 0.29 \pm 0.08)\times 10^{-4} and the
first, second, and third moments = 2.267 \pm 0.019 \pm 0.032 \pm
0.003 GeV,, )^2> = 0.0484 \pm 0.0053 \pm 0.0077 \pm
0.0005 GeV^2, and )^3> = -0.0048 \pm 0.0011 \pm 0.0011
\pm 0.0004 GeV^3, for the range E_\gamma > 1.8 GeV, where E_{\gamma} is the
photon energy in the B-meson rest frame. Results are also presented for
narrower E_{\gamma} ranges. In addition, the direct CP asymmetry A_{CP}(B -->
X_{s+d} \gamma) is measured to be 0.057 \pm 0.063. The spectrum itself is also
unfolded to the B-meson rest frame; that is the frame in which theoretical
predictions for its shape are made.Comment: 37 pages, 19 postscript figures, submitted to Phys. Rev. D. No
analysis or results have changed from previous version. Some changes to
improve clarity based on interactions with Phys. Rev. D referees, including
one new Figure (Fig. 13), and some minor wording/punctuation/spelling
mistakes fixe
Measurement of ISR-FSR interference in the processes e+ e- --> mu+ mu- gamma and e+ e- --> pi+ pi- gamma
Charge asymmetry in processes e+ e- --> mu+ mu- gamma and e+ e- --> pi+ pi-
gamma is measured using 232 fb-1 of data collected with the BABAR detector at
center-of-mass energies near 10.58 GeV. An observable is introduced and shown
to be very robust against detector asymmetries while keeping a large
sensitivity to the physical charge asymmetry that results from the interference
between initial and final state radiation. The asymmetry is determined as
afunction of the invariant mass of the final-state tracks from production
threshold to a few GeV/c2. It is compared to the expectation from QED for e+ e-
--> mu+ mu- gamma and from theoretical models for e+ e- --> pi+ pi- gamma. A
clear interference pattern is observed in e+ e- --> pi+ pi- gamma, particularly
in the vicinity of the f_2(1270) resonance. The inferred rate of lowest order
FSR production is consistent with the QED expectation for e+ e- --> mu+ mu-
gamma, and is negligibly small for e+ e- --> pi+ pi- gamma.Comment: 32 pages,29 figures, to be submitted to Phys. Rev.
Observation of time-reversal violation in the B0 meson system
The individually named authors work collectively as The BABAR Collaboration. Copyright @ 2012 American Physical Society.Although CP violation in the B meson system has been well established by the B factories, there has been no direct observation of time-reversal violation. The decays of entangled neutral B mesons into definite flavor states (B0 or BÂŻÂŻÂŻ0), and J/ÏK0L or ccÂŻK0S final states (referred to as B+ or Bâ), allow comparisons between the probabilities of four pairs of T-conjugated transitions, for example, BÂŻÂŻÂŻ0âBâ and BââBÂŻÂŻÂŻ0, as a function of the time difference between the two B decays. Using 468Ă106 BBÂŻÂŻÂŻ pairs produced in ΄(4S) decays collected by the BABAR detector at SLAC, we measure T-violating parameters in the time evolution of neutral B mesons, yielding ÎS+T=â1.37±0.14(stat)±0.06(syst) and ÎSâT=1.17±0.18(stat)±0.11(syst). These nonzero results represent the first direct observation of T violation through the exchange of initial and final states in transitions that can only be connected by a T-symmetry transformation.DOE and NSF (USA), NSERC (Canada), CEA and CNRS-IN2P3 (France), BMBF and
DFG(Germany), INFN (Italy), FOM (The Netherlands),
NFR (Norway), MES (Russia), MINECO (Spain), STFC
(United Kingdom). Individuals have received support from
the Marie Curie EIF (European Union), the A. P. Sloan
Foundation (USA) and the Binational Science Foundation
(USA-Israel)
Recommended from our members
Measurement of the Time-Dependent CP Asymmetry of Partially Reconstructed B0->D*+D*- Decays
We present a new measurement of the time-dependent CP asymmetry of B0->D*+D*-
decays using (471+-5) million BBbar pairs collected with the BaBar detector at
the PEP-II B Factory at the SLAC National Accelerator Laboratory. Using the
technique of partial reconstruction, we measure the time-dependent CP asymmetry
parameters S=-0.34+-0.12+-0.05$ and C=+0.15+-0.09+-0.04. Using the value for
the CP-odd fraction R_perp=0.158+-0.028+-0.006, previously measured by BaBar
with fully reconstructed B0->D*+D*- events, we extract the CP-even components
S+=-0.49+-0.18+-0.07+-0.04 and C+=+0.15+-0.09+-0.04. In each case, the first
uncertainty is statistical and the second is systematic; the third uncertainty
on S+ is the contribution from the uncertainty on R_perp. The measured value of
the CP-even component S+ is consistent with the value of sin(2Beta) measured in
b->(ccbar)s transitions, and with the Standard Model expectation of small
penguin contributions.Comment: 17 pages, 7 figures, submitted to Physical Review
- âŠ