1,155 research outputs found
Measurement of D0– mixing and search for CP violation in D0 → K+K−,π+π− decays with the full Belle data set
We report an improved measurement of D0–D0 mixing and a search for CP violation in D0 decays to CP-even final states K+K− and π+π−. The measurement is based on the final Belle data sample of 976 fb−1
New Experiments with Antiprotons
Fermilab operates the world's most intense antiproton source. Newly proposed
experiments can use those antiprotons either parasitically during Tevatron
Collider running or after the Tevatron Collider finishes in about 2011. For
example, the annihilation of 8 GeV antiprotons might make the world's most
intense source of tagged D^0 mesons, and thus the best near-term opportunity to
study charm mixing and, via CP violation, to search for new physics. Other
potential measurements include sensitive studies of hyperons and of the
mysterious X, Y, and Z states. Production of antihydrogen in flight can be used
for first searches for antihydrogen CPT violation. With antiproton deceleration
to low energy, an experiment using a Penning trap and an atom interferometer
could make the world's first measurement of the gravitational force on
antimatter.Comment: Prepared for the Proceedings of the 4th International Symposium on
Symmetries in Subatomic Physics (SSP2009), June 2-5, 2009, Department of
Physics, National Taiwan University, Taipei, Taiwa
The HERA-B Ring Imaging Cherenkov Counter
The HERA-B RICH uses a radiation path length of 2.8 m in C_4F_10 gas and a
large 24 square meters spherical mirror for imaging Cherenkov rings. The photon
detector consists of 2240 Hamamatsu multi-anode photomultipliers with about
27000 channels. A 2:1 reducing two-lens telescope in front of each PMT
increases the sensitive area at the expense of increased pixel size, resulting
in a contribution to the resolution which roughly matches that of dispersion.
The counter was completed in January of 1999, and its performance has been
steady and reliable over the years it has been in operation. The design
performance of the RICH was fully reached: the average number of detected
photons in the RICH for a beta=1 particle was found to be 33 with a single hit
resolution of 0.7 mrad and 1 mrad in the fine and coarse granularity regions,
respectively.Comment: 29 pages, 23 figure
The Outer Tracker Detector of the HERA-B Experiment. Part II: Front-End Electronics
The HERA-B Outer Tracker is a large detector with 112674 drift chamber
channels. It is exposed to a particle flux of up to 2x10^5/cm^2/s thus coping
with conditions similar to those expected for the LHC experiments. The
front-end readout system, based on the ASD-8 chip and a customized TDC chip, is
designed to fulfil the requirements on low noise, high sensitivity, rate
tolerance, and high integration density. The TDC system is based on an ASIC
which digitizes the time in bins of about 0.5 ns within a total of 256 bins.
The chip also comprises a pipeline to store data from 128 events which is
required for a deadtime-free trigger and data acquisition system. We report on
the development, installation, and commissioning of the front-end electronics,
including the grounding and noise suppression schemes, and discuss its
performance in the HERA-B experiment
First study of \eta_c, \eta(1760) and X(1835) production via \eta'\pi^+\pi^- final states in two-photon collisions
The invariant mass spectrum of the \eta' \pi^+ \pi^- final state produced in
two-photon collisions is obtained using a 673 fb^{-1} data sample collected in
the vicinity of the \Upsilon(4S) resonance with the Belle detector at the KEKB
asymmetric-energy e^+e^- collider. We observe a clear signal of the \eta_c and
measure its mass and width to be M(\eta_c)=(2982.7 +- 1.8(stat) +- 2.2(syst) +-
0.3(model)) MeV/c^2 and \Gamma(\eta_c) = (37.8^{+5.8}_{-5.3}(stat) +- 2.8(syst)
+- 1.4(model)) MeV/c^2. The third error is an uncertainty due to possible
interference between the \eta_c and a non-resonant component. We also report
the first evidence for \eta(1760) decay to \eta' \pi^+ \pi^-; we find two
solutions for its parameters, depending on the inclusion or not of the X(1835),
whose existence is of marginal significance in our data. From a fit to the mass
spectrum using coherent X(1835) and \eta(1760) resonant amplitudes, we set a
90% confidence level upper limit on the product \Gamma_{\gamma\gamma} \BR
(\eta' \pi^+ \pi^-) for the X(1835).Comment: 13 pages, 7 figures, submitted to PR
Measurement of the ratio B(D0->pi+pi-pi0)/B(D0->K-pi+pi0) and the time-integrated CP asymmetry in D0->pi+pi-pi0
We report a high-statistics measurement of the relative branching fraction
B(D0->pi+pi-pi0)/B(D0->K-pi+pi0) using a 532 fb^{-1} data sample collected with
the Belle detector at the KEKB asymmetric-energy e+e- collider. The measured
value of the relative branching fraction is B(D0->pi+pi-pi0)/B(D0->K-pi+pi0) =
(10.12 +/- 0.04(stat) +/- 0.18(syst))x10^{-2} which has an accuracy comparable
to the world average. We also present a measurement of the time-integrated CP
asymmetry in D0->pi+pi-pi0 decay. The result, A_{CP} = (0.43 +/- 1.30)%, shows
no significant CP violation.Comment: 15 pages, 11 figures, submitted to Physics Letters
Search for CP violation in the decays and
We have searched for CP violation in the charmed meson decays and using 673 fb of data
collected with the Belle detector at the KEKB asymmetric-energy
collider. No evidence for CP violation is observed. We report the most
sensitive CP asymmetry measurements to date for these decays: , , , and , where the first uncertainties are statistical and
the second are systematic
Search for CP Violation in the Decays
We have searched for CP violation in the decays
where denotes a neutral pseudo-scalar meson which is either a ,
, or using KEKB asymmetric-energy collision data
corresponding to an integrated luminosity of 791 fb collected with the
Belle detector. No evidence of significant CP violation is observed. We report
the most precise CP asymmetry measurement in the decay to date: . We also report the first measurements of
CP asymmetries in the decays and : and , respectively
Measurement of CP asymmetry in Cabibbo suppressed D0 decays
We measure the CP-violating asymmetries in decays to the D0 -> K+K- and D0 ->
pi+pi- CP eigenstates using 540 fb^{-1} of data collected with the Belle
detector at or near the Upsilon(4S) resonance. Cabibbo-favored D0 -> K-pi+
decays are used to correct for systematic detector effects. The results,
A_{CP}^{KK} = (-0.43 +- 0.30 +- 0.11)% and A_{CP}^{pipi} = (+0.43 +- 0.52 +-
0.12)%, are consistent with no CP violation.Comment: Submitted to Phys. Lett.
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