407 research outputs found
Search for CP Violation in D Meson Decays to phi pi+
We search for CP violation in Cabibbo-suppressed charged D meson decays by
measuring the difference between the CP violating asymmetries for the
Cabibbo-suppressed decays D+ -> K+K-pi+ and the Cabibbo-favored decays Ds ->
K+K-pi+ in the K+K- mass region of the phi resonance. Using 955/fb of data
collected with the Belle detector we obtain A_CP(D+ -> phi pi+) = (+0.51 +-
0.28 +- 0.05)%. The measurement improves the sensitivity of previous searches
by more than a factor of five. We find no evidence for direct CP violation.Comment: submitted to PR
Search for double charmonium decays of the P-wave spin-triplet bottomonium states
Using a sample of 158 million events collected with the Belle
detector, we search for the first time for double charmonium decays of the
-wave spin-triplet bottomonium states (,
\chi_{bJ} \to \jpsi \jpsi, \jpsi \psp, \psp \psp for J=0, 1, and 2). No
significant signal is observed in the double charmonium mass
spectra, and we obtain the following upper limits, \BR(\chi_{bJ} \to \jpsi
\jpsi)<7.1\times 10^{-5}, , ,
\BR(\chi_{bJ} \to \jpsi \psp)<1.2\times 10^{-4}, ,
, \BR(\chi_{bJ} \to \psp \psp)<3.1\times 10^{-5},
, for J=0, 1, and 2, respectively, at
the 90% confidence level. These limits are significantly lower than the central
values (with uncertainties of 50% to 70%) predicted using the light cone
formalism but are consistent with calculations using the NRQCD factorization
approach.Comment: 7 pages, 4 figures, 1 tabl
Precision measurement of charged pion and kaon differential cross sections in electron-positron annihilation at Q = 10.52 GeV
Measurements of inclusive differential cross sections for charged pion and
kaon production in electron-positron annihilation have been carried out at a
center-of-mass energy of Q = 10.52 GeV. The measurements were performed with
the Belle detector at the KEKB electron-positron collider using a data sample
containing 113 million e+e- -> qqbar events, where q={u,d,s,c}. We present
charge-integrated differential cross sections d\sigma_h+-/dz for h+- = pi+-,
K+- as a function of the relative hadron energy z = 2*E_h / sqrt{s} from 0.2 to
0.98. The combined statistical and systematic uncertainties for pi+- (K+-) are
4% (4%) at z ~ 0.6 and 15% (24%) at z ~ 0.9. The cross sections are the first
measurements of the z-dependence of pion and kaon production for z > 0.7 as
well as the first precision cross section measurements at a center-of-mass
energy far below the Z^0 resonance used by the experiments at LEP and SLC.Comment: 7 pages, 3 figures. Ancillary file including all cross section and
uncertainty values with 10 pages, 5 figure
Search for a dark vector gauge boson decaying to using decays
We report a search for a dark vector gauge boson that couples to
quarks in the decay chain , . No signal is found and we set a
mass-dependent limit on the baryonic fine structure constant of in the mass range of 290 to 520 MeV/. This analysis is
based on a data sample of 976 fb collected by the Belle experiment at
the KEKB asymmetric-energy collider.Comment: 6 pages, 4 figure
Measurements of the masses and widths of the and baryons
We present measurements of the masses and decay widths of the baryonic states
and using a data sample
corresponding to an integrated luminosity of 711 fb collected with the
Belle detector at the KEKB asymmetric-energy collider operating at
the resonance. We report the mass differences with respect to
the baryon MeV/, MeV/,
MeV/, MeV/, and the decay widths
MeV/,
MeV/,
MeV/,
MeV/,
where the first uncertainties are statistical and the second are systematic.
The isospin mass splittings are measured to be
MeV/ and
MeV/. These results are the most precise to date.Comment: 13 pages, 4 figures, Submitted to PRD(RC
First Observation of Radiative B^0 -> \phi K^0 \gamma Decays and Measurements of Their Time-Dependent CP Violation
We report the first observation of the radiative decay B^0 -> \phi K^0 \gamma
using a data sample of 772 x 10^6 B B-bar pairs collected at the \Upsilon(4S)
resonance with the Belle detector at the KEKB asymmetric-energy e^+e^-
collider. We observe a signal of 37+/-8 events with a significance of 5.4
standard deviations including systematic uncertainties. The measured branching
fraction is , where the uncertainties are statistical and systematic, respectively.
We also report the first measurements of time-dependent CP violation
parameters: and . Furthermore, we measure , and find that the signal is concentrated in
the M_{\phi K} mass region near threshold.Comment: 6 pages, 3 figures, Modified version is to be published in PRD(RC
Evidence of and search for double-charmonium production in and decays
Using data samples of and
events collected with the Belle detector, a first experimental
search has been made for double-charmonium production in the exclusive decays
, where , , , , and . No significant signal is
observed in the spectra of the mass recoiling against the reconstructed
or except for the evidence of production with a
significance of for . The
measured branching fraction \BR(\Upsilon(1S)\rightarrow J/\psi+\chi_{c1}) is
. The
confidence level upper limits on the branching fractions of the other modes
having a significance of less than are determined. These results are
consistent with theoretical calculations using the nonrelativistic QCD
factorization approach.Comment: 12 pages, 4 figures, 1 table. The fit range was extended to include
X(4160) signal according to referee's suggestions. Other results unchanged.
Paper was accepted for publication as a regular article in Physical Review
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
Measurement of the CP-violation Parameter sin2 with a New Tagging Method at the Resonance
We report a measurement of the CP-violation parameter sin2 at the
resonance using a new tagging method, called "-
tagging." In decays containing a neutral meson, a charged
, and a charged pion, the neutral is reconstructed in the
CP-eigenstate decay channel. The initial flavor of the neutral meson at the
moment of the decay is opposite to that of the charged and
may thus be inferred from the charge of the pion without reconstructing the
charged . From the asymmetry between - and - tagged
yields, we determine sin2 = 0.57 0.58(stat)
0.06(syst). The results are based on 121 fb of data recorded by the
Belle detector at the KEKB collider.Comment: 6 pages, 3 figures (submitted to PRL
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