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Register a new userSearch for a massive invisible particle $X^0$ in $B^{+}to e^{+}X^{0}$ and $B^{+}to mu^{+}X^{0}$ decays
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We present a search for a non-Standard-Model invisible particle $X^0$ in the mass range $0.1textrm{-}1.8 ,{rm GeV}/{c^2}$ in $B^{+}to e^{+} X^{0}$ and $B^{+}to mu^{+} X^{0}$ decays. The results are obtained from a $711~{rm fb}^{-1}$ data sample that corresponds to $772 times 10^{6} Bbar{B}$ pairs, collected at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB $e^+ e^-$ collider. One $B$ meson is fully reconstructed in a hadronic mode to determine the momentum of the lepton of the signal decay in the rest frame of the recoiling partner $B$ meson. We find no evidence of a signal and set upper limits on the order of $10^{-6}$.
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We report the results of a search for the decay $B^0 to X(3872)(to J/psi pi^+ pi^-) gamma$. The analysis is performed on a data sample corresponding to an integrated luminosity of $711,{rm fb}^{-1}$ and containing $772 times 10^6 Bbar{B}$ pairs, collected with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider running at the $Upsilon(4S)$ resonance energy. We find no evidence for a signal and place an upper limit of $mathcal{B}(B^0 to X(3872)gamma)times mathcal{B}(X(3872) to J/psi pi^+ pi^-) < 5.1 times 10^{-7}$ at 90% confidence level.
A search is presented for hidden-sector bosons, $chi$, produced in the decay ${B^0!to K^*(892)^0chi}$, with $K^*(892)^0!to K^{+}pi^{-}$ and $chi!tomu^+mu^-$. The search is performed using $pp$-collision data corresponding to 3.0 fb$^{-1}$ collected with the LHCb detector. No significant signal is observed in the accessible mass range $214 leq m({chi}) leq 4350$ MeV, and upper limits are placed on the branching fraction product $mathcal{B}(B^0!to K^*(892)^0chi)timesmathcal{B}(chi!tomu^+mu^-)$ as a function of the mass and lifetime of the $chi$ boson. These limits are of the order of $10^{-9}$ for $chi$ lifetimes less than 100 ps over most of the $m(chi)$ range, and place the most stringent constraints to date on many theories that predict the existence of additional low-mass bosons.
We report a search for $B^{0}$ decays into invisible final states using a data sample of $657 times 10^{6}$ $Bbar{B}$ pairs collected at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB $e^{+}e^{-}$ collider. The signal is identified by fully reconstructing a hadronic decay of the accompanying $B$ meson and requiring no other particles in the event. No significant signal is observed, and we obtain an upper limit of $1.3 times 10^{-4}$ at the 90% confidence level for the branching fraction of invisible $B^{0}$ decay.
We present a search for seven lepton-flavor-violating neutral charm decays of the type $D^{0}rightarrow X^{0} e^{pm} mu^{mp}$, where $X^{0}$ represents a $pi^{0}$, $K^{0}_{rm S}$, $bar{K^{*0}}$, $rho^{0}$, $phi$, $omega$, or $eta$ meson. The analysis is based on $468$ fb$^{-1}$ of $e^+e^-$ annihilation data collected at or close to the $Upsilon(4S)$ resonance with the BaBar detector at the SLAC National Accelerator Laboratory. No significant signals are observed, and we establish 90% confidence level upper limits on the branching fractions in the range $(5.0 - 22.5)times 10^{-7}$. The limits are between one and two orders of magnitude more stringent than previous measurements.
We report searches for $B^0torm{invisible}$ and $B^0torm{invisible}+gamma$ decays, where the energy of the photon is required to be larger than 0.5 GeV. These results are obtained from a $711,{rm fb}^{-1}$ data sample that contains $772 times 10^6 Bbar{B}$ pairs and was collected near the $Upsilon,(4S)$ resonance with the Belle detector at the KEKB $e^+ e^-$ collider. We observe no significant signal for either decay and set upper limits on their branching fractions at $90%$ confidence level of $mathcal{B},(B^0torm{invisible}) < 7.8times10^{-5}$ and $mathcal{B},(B^0torm{invisible}+gamma) < 1.6times10^{-5}$.
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