85 research outputs found
Search for CP violation in D^0 -> pi^0 pi^0 decays
We search for CP violation in neutral charm meson decays using a data sample
with an integrated luminosity of 966 fb^-1 collected with the Belle detector at
the KEKB e+e- asymmetric-energy collider. The asymmetry obtained in the rate of
D^0 and D^0-bar decays to the pi^0 pi^0 final state,
[-0.03+-0.64(stat)+-0.10(syst)]%, is consistent with no CP violation. This
constitutes an order of magnitude improvement over the existing result. We also
present an updated measurement of the CP asymmetry in the D^0 -> K_S pi^0
decay: A_{CP}(D^0 -> K_S pi^0) = [-0.21+-0.16(stat)+-0.07(syst)]%
Search for and a measurement of the branching fraction for
We search for the decay and measure the
branching fraction for using
121.4~ of data collected at the
resonance with the Belle detector at the KEKB asymmetric-energy
collider. The branching fraction is measured
to be , where is the fraction of
in events. Our result is in good
agreement with the theoretical predictions as well as with a recent measurement
from LHCb. We observe no statistically significant signal for the decay
and set a confidence-level upper
limit on its branching fraction at . This constitutes a
significant improvement over the previous result.Comment: 6 pages, 3 figure
Measurements of the and resonances via
We report new measurements of the total cross sections for ( = 1, 2, 3) and from a
high-luminosity fine scan of the region - GeV with the
Belle detector. We observe that the spectra have
little or no non-resonant component and extract from them the masses and widths
of and and their relative phase. We find
MeV/ and
\Gamma_{10860}=(53.7^{+7.1}_{-5.6}\,^{+1.3}_{-5.4}) MeV and report first
measurements M_{11020}=(10987.5^{+6.4}_{-2.5}\,^{+9.0}_{-2.1}) MeV/,
\Gamma_{11020}=(61^{+9}_{-19}\,^{+2}_{-20}) MeV, and \phi_{\rm
11020}-\phi_{\rm 10860} = (-1.0\pm0.4\,^{+1.4}_{-0.1}) rad.Comment: University of Cincinnati preprint UCHEP-15-01, submitted to Physical
Review D - Rapid Communication
First observation of the hadronic transition and new measurement of the and parameters
Using a sample of decays collected by
the Belle experiment at the KEKB collider, we observe for the first
time the transition with the branching fraction
and we measure the mass MeV/, corresponding to the hyperfine splitting MeV/. Using the transition , we measure the mass MeV/, corresponding to MeV/, the width
MeV/ and the branching
fraction .Comment: 7 pages, 2 figures, submitted to Phys. Rev. Let
Observation of in decays
We report the first observation of and
evidence for . We measure the product of
branching fractions for the former to be {\cal B}(B^0 \to X(3872) (K^+ \pi^-))
\times {\cal B}(X(3872) \to J/\psi \pi^+ \pi^-) = (7.9 \pm 1.3(\mbox{stat.})\pm
0.4(\mbox{syst.})) \times 10^{-6} and find that does not dominate the decay
mode. We also measure {\cal B}(B^+ \to X(3872) (K^0 \pi^+)) \times {\cal
B}(X(3872) \to J/\psi \pi^+ \pi^-) = (10.6 \pm 3.0(\mbox{stat.}) \pm
0.9(\mbox{syst.})) \times 10^{-6}. This study is based on the full data sample
of 711~fb ( pairs) collected at the
resonance with the Belle detector at the KEKB collider.Comment: 7 pages, 3 figure
Study of pair production in single-tag two-photon collisions
We report a measurement of the differential cross section of pair
production in single-tag two-photon collisions, , in scattering. The cross section is measured for up to
30 GeV, where is the negative of the invariant mass squared of the
tagged photon, in the kinematic range 0.5 GeV < W < 2.1 GeV and < 1.0 for the total energy and pion scattering angle, respectively,
in the center-of-mass system. The results are based on a data
sample of 759 fb collected with the Belle detector at the KEKB
asymmetric-energy collider. The transition form factor of the
and that of the with the helicity-0, -1, and -2
components separately are measured for the first time and are compared with
theoretical calculations.Comment: 36 pages, 37 figures, 11 tables, Belle Preprint 2015-15, KEK Preprint
2015-2
Observation of a new charged charmoniumlike state in B -> J/psi K pi decays
We present the results of an amplitude analysis of anti-B0 -> J/psi K- pi+
decays. A new charged charmoniumlike state Zc(4200)+ decaying to J/psi pi+ is
observed with a significance of 6.2 sigma. The mass and width of the Zc(4200)+
are 4196 +31-29 +17-13 MeV/c^2 and 370 +70-70 +70-132 MeV, respectively; the
preferred assignment of the quantum numbers is J^P = 1^+. In addition, we find
evidence for Zc(4430)+ -> J/psi pi+. The analysis is based on a 711 fb^-1 data
sample collected by the Belle detector at the asymmetric-energy e+ e- collider
KEKB.Comment: 14 pages, 13 figure
Evidence for the decay B0->eta pi^0
We report a search for the charmless hadronic decay with a
data sample corresponding to an integrated luminosity of 694
containing pairs. The data were collected by the
Belle experiment running on the resonance at the KEKB
collider. We measure a branching fraction
, where
the first uncertainty is statistical and the second is systematic. Our
measurement gives an upper limit of at 90\% confidence level. The signal has a significance of
standard deviations and constitutes the first evidence for this decay mode.Comment: 11 pages, 3 figures, 2 tables, submitted to Physical Review D(R
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