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The first search for the rare radiative decay $Xi_b^- to Xi^- gamma$ is performed using data collected by the LHCb experiment in proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fb$^{-1}$. The $Xi_b- to Xi^- J/psi$ channel is used as normalization. No $Xi_b^- to Xi^- gamma$ signal is found and an upper limit of $mathcal{B}(Xi_b^- to Xi^- gamma) < 1.3 times 10^{-4}$ at 95% confidence level is obtained.
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We have searched for the baryon-containing radiative penguin decays B^- -> Lambda p-bar gamma and B^- -> Sigma^0 p-bar gamma, using a sample of 9.7 million BBbar events collected at the Upsilon(4S) with the CLEO detector. We find no evidence for either, and set 90% confidence level upper limits for photons with B rest frame energy greater than 2.0 GeV of [Br(B^- -> Lambda p-bar gamma) + 0.3 Br(B^- -> Sigma^0 p-bar gamma)] < 3.3 x 10^-6, [Br(B^- -> Sigma^0 p-bar gamma) + 0.4 Br(B^- -> Lambda p-bar gamma)] < 6.4 x 10^-6. From the latter, we estimate (for photons with B rest frame energy greater than 2.0 GeV) Br(B -> X_s gamma, X_s containing baryons) < 3.8 x 10^-5. This limit implies upper limits on corrections to CLEOs recent measurement of branching fraction, mean photon energy, and variance in photon energy from b -> s gamma that are less than half the combined statistical and systematic errors quoted on these quantities.
Using an electron-positron collision data sample of 2.93 fb$^{-1}$ collected at a center-of-mass energy of $sqrt{s}=3.773$ GeV with the BESIII detector, we present the first search for the radiative leptonic decay $D^{+} rightarrow gamma e^{+}{ u}_{e}$. The analysis is performed with a double tag method. We do not observe a significant $D^{+} rightarrow gamma e^{+}{ u}_{e}$ signal, and obtain an upper limit on the branching fraction of $D^{+} rightarrow gamma e^{+}{ u}_{e}$ decay with the energy of radiative photon larger than 10 MeV of $3.0times10^{-5}$ at the 90% confidence level.
The $eta to pi^0 gamma gamma$ decay was investigated by the SND detector at VEPP-2M $e^+e^-$ collider in the reaction $e^+e^-tophito etagamma$. Here we present the results and some details of this study. We report an upper limit (90% c.l.) $Br(eta to pi^0 gamma gamma)<8.4times 10^{-4}$ as our final result. Our upper limit does not contradict the earlier measurement by GAMS spectrometer. To facilitate future studies a rather detailed review of the problem is also given.
We search for hadronic decays of a light Higgs boson (A0) produced in radiative decays of an Upsilon(2S) or Upsilon(3S) meson, Upsilon --> gamma A0. The data have been recorded by the BABAR experiment at the Upsilon(3S) and Upsilon(2S) center of mass energies, and include (121.3 pm 1.2) x 10^6 Upsilon(3S) and (98.3 pm 0.9) x 10^6 Upsilon(2S) mesons. No significant signal is observed. We set 90% confidence level upper limits on the product branching fractions B(Upsilon(nS)-->gamma A0) x B(A0-->hadrons) (n=2 or 3) that range from 1 x 10^{-6} for an A0 mass of 0.3 GeV/c^2 to 8 x 10^{-5} at 7 GeV/c^2.
Using a $pp$ collision data sample corresponding to an integrated luminosity of 3.0~fb$^{-1}$, collected by the LHCb detector, we present the first search for the strangeness-changing weak decay $Xi_b^-toLambda_b^0pi^-$. No $b$ hadron decay of this type has been seen before. A signal for this decay, corresponding to a significance of 3.2 standard deviations, is reported. The relative rate is measured to be ${{f_{Xi_b^-}}over{f_{Lambda_b^0}}}{cal{B}}(Xi_b^-toLambda_b^0pi^-) = (5.7pm1.8^{+0.8}_{-0.9})times10^{-4}$, where $f_{Xi_b^-}$ and $f_{Lambda_b^0}$ are the $btoXi_b^-$ and $btoLambda_b^0$ fragmentation fractions, and ${cal{B}}(Xi_b^-toLambda_b^0pi^-)$ is the branching fraction. Assuming $f_{Xi_b^-}/f_{Lambda_b^0}$ is bounded between 0.1 and 0.3, the branching fraction ${cal{B}}(Xi_b^-toLambda_b^0pi^-)$ would lie in the range from $(0.57pm0.21)%$ to $(0.19pm0.07)%$.
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