The Cabibbo-allowed weak radiative decay $\Lambda_{c}^+\to \Sigma^+\gamma$
has been searched for in a sample of $\Lambda_{c}^+\bar{\Lambda}_{c}^-$ pairs
produced in $e^+e^-$ annihilations, ...corresponding to an integrated luminosity
of $4.5 \mathrm{fb}^{-1}$ collected with the BESIII detector at center-of-mass
energies between 4.60 and 4.70 GeV. No excess of signal above background is
observed, and we set an upper limit on the branching fraction of this decay to
be ${\mathcal B}(\Lambda_{c}^+\to \Sigma^+\gamma)<4.4\times10^{-4}$ at a
confidence level of 90\%, which is in agreement with Standard Model
expectations.
We present measurements of branching fractions and \CP-violating asymmetries in decays of $B$ mesons to two-body final states containing a \Kz. The results are based on a data sample of approximately ...88 million \upsbb decays collected with the \babar detector at the \pep2 asymmetric-energy $B$ Factory at SLAC. We measure $\BR(\Bp\to\Kz\pip) = (22.3 \pm 1.7 \pm 1.1)\times 10^{-6}$, $\BR(\Bz\to\Kz\piz) = (11.4\pm 1.7\pm 0.8)\times 10^{-6}$, $\BR(\Bp\to\Kzb\Kp) < 2.5\times 10^{-6}$, and $\BR(\Bz\to\KzKzb) < 1.8\times 10^{-6}$, where the first uncertainty is statistical and the second is systematic, and the upper limits are at the 90% confidence level. In addition, the following \CP-violating asymmetries have been measured: ${\cal A}_{CP}(\Bp\to\Kz\pip) = -0.05 \pm 0.08 \pm 0.01$ and ${\cal A}_{CP}(\Bz\to\Kz\piz) = 0.03 \pm 0.36\pm 0.11$.
We report two novel determinations of /|Vub/ with reduced model dependence, based on measurements of the mass distribution of the hadronic system in semileptonic B decays. Events are selected by ...fully reconstructing the decay of one B meson and identifying a charged lepton from the decay of the other B meson from Upsilon(4S)-->BB events. In one approach, we combine the inclusive B-->Xulambdav rate, integrated up to a maximum hadronic mass mX<1.67 GeV/c2, with a measurement of the inclusive B-->Xsgamma photon energy spectrum. We obtain /Vub/=(4.43+/-0.38stat+/-0.25syst+/-0.29theo) x 10-3. In another approach we measure the total B-->Xulambdav rate over the full phase space and find /Vub/=(3.84+/-0.70stat+/-0.30syst+/-0.10theo) x 10-3.
PHYS. REV. D 107, 092001 (2023) A new mechanism has been proposed to simultaneously explain the presence of
dark matter and the matter-antimatter asymmetry in the universe. This scenario
predicts ...exotic $B$ meson decays into a baryon and a dark sector anti-baryon
($\psi_D$) with branching fractions accessible at $B$ factories. We present a
search for $B \rightarrow \Lambda \psi_D$ decays using data collected by the
$BABAR$ experiment at SLAC. This reaction is identified by fully reconstructing
the accompanying $B$ meson and requiring the presence of a single $\Lambda$
baryon in the remaining particles. No significant signal is observed, and
bounds on the $B \rightarrow \Lambda \psi_D$ branching fraction are derived in
the range $0.13 - 5.2\times 10^{-5}$ for $1.0 < m_{\psi_D} < 4.2$ GeV/$c^{2}$.
These results set strong constraints on the parameter space allowed by the
theory.
We present the results of a search for the decay B0-->tau+tau- in a data sample of (232+/-3)x10(6) Upsilon(4S)-->BB decays using the BABAR detector. Certain extensions of the standard model predict ...measurable levels of this otherwise rare decay. We reconstruct fully one neutral B meson and seek evidence for the signal decay in the rest of the event. We find no evidence for signal events and obtain Beta(B0->tau+tau-)<4.1x10(-3) at the 90% confidence level.
Phys. Rev. D 107, 112001(2023) Using data samples with a total integrated luminosity of approximately 18
fb$^{-1}$ collected by the BESIII detector operating at the BEPCII, the process
...$e^+e^-\rightarrow\Lambda\bar{\Lambda} \eta$ is studied at center-of-mass
energies between 3.5106 and 4.6988 GeV. The Born cross section for the process
$e^+e^-\rightarrow\Lambda\bar{\Lambda}\eta$ is measured. No significant
structure is observed in the Born cross section line shape. An enhancement near
the $\Lambda\bar{\Lambda}$ mass threshold is observed for the first time in the
process. The structure can be described by an $S$-wave Breit-Wigner function.
Neglecting contribution of excited $\Lambda$ states and potential
interferences, the mass and width are determined to be ($2356\pm 7\pm17$)
MeV/$c^2$ and ($304\pm28\pm54$) MeV, respectively, where the first
uncertainties are statistical and the second are systematic.
We report the results of a search for T, CP, CPT, and violation in B0-B0 mixing using an inclusive dilepton sample collected by the BABAR experiment at the PEP-II factory. Using a sample of 232 x ...10(6) BB pairs, we measure the T and CP violation parameter |q/p| - 1 = (-0.8 +/- 2.7(stat) +/- 1.9(syst) x 10(-3), and the CPT and CP parameters Imz = (13.9 +/- 7.3(stat) +/- 3.2(syst)) x 10(-3) and Delta Gamma x Rez = (7.1 +/- 3.9(stat) +/- 2.0(stat)) x 10(-3) ps(-1). The statistical correlation between the measurements of Imz and Delta Gamma x Rez is 76%.
The B(0) and B(+) meson lifetimes have been measured in e(+)e(-) annihilation data collected in 1999 and 2000 with the BABAR detector at center-of-mass energies near the Upsilon(4S) resonance. Events ...are selected in which one B meson is fully reconstructed in a hadronic final state while the second B meson is reconstructed inclusively. A combined fit to the B(0) and the B(+) decay time difference distributions yields tau(B(0)) = 1.546+/-0.032(stat)+/-0.022(syst) ps, tau(B(+)) = 1.673+/-0.032(stat)+/-0.023(syst) ps, and tau(B(+))/tau(B(0)) = 1.082+/-0.026(stat)+/-0.012(syst).
Chin.Phys.C 47 (2023) 2, 023001 Using electron-positron annihilation data samples corresponding to an
integrated luminosity of 4.5 $\rm{{fb}^{-1}}$, collected by the BESIII detector
in the energy ...region between $4600$ MeV and $4699$ MeV, we report the first
observations of the Cabibbo-suppressed decays $\Lambda_c^+\to n\pi^+\pi^0$,
$\Lambda_c^+\to n\pi^+\pi^-\pi^+$, and the Cabibbo-favored decay
$\Lambda_c^+\to nK^-\pi^+\pi^+$ with statistical significances of $7.9\sigma$,
$7.8\sigma$, and $>10\sigma$, respectively. The branching fractions of these
decays are measured to be $\mathcal{B}(\Lambda_{c}^{+}\rightarrow
n\pi^{+}\pi^{0})=(0.64\pm0.09\pm0.02)\%$,
$\mathcal{B}(\Lambda_{c}^{+}\rightarrow
n\pi^{+}\pi^{-}\pi^{+})=(0.45\pm0.07\pm0.03)\%$, and
$\mathcal{B}(\Lambda_{c}^{+}\rightarrow
nK^{-}\pi^{+}\pi^{+})=(1.90\pm0.08\pm0.09)\%$, where the first uncertainties
are statistical and the second are systematic. We find that the branching
fraction of the decay $\Lambda_{c}^{+}\rightarrow n\pi^{+}\pi^{0}$ is about one
order of magnitude higher than that of $\Lambda_{c}^{+}\rightarrow n\pi^{+}$.
The B0 and B+ meson lifetimes have been measured in e+e- annihilation data collected in 1999 and 2000 with the BABAR detector at center-of-mass energies near the Upsilon(4S) resonance. Events are ...selected in which one B meson is fully reconstructed in a hadronic final state while the second B meson is reconstructed inclusively. A combined fit to the B0 and the B+ decay time difference distributions yields tau_{B0} = 1.546 +/- 0.032 (stat) +/- 0.022(syst) ps, tau_{B+} = 1.673 +/- 0.032 (stat) +/- 0.023 (syst) ps and tau_{B+} / tau_{B0} = 1.082 +/- 0.026 (stat) +/- 0.012 (syst)
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