Abstract: A search for the rare decays B-S(0) -> tau(+) tau(-) and B-0 -> tau(+) tau(-) is performed using proton-proton collision data collected with the LHCb detector. The data sample corresponds to an integrated luminosity of 3 fb(-1) collected in 2011 and 2012. The tau leptons are reconstructed through the decay tau(-) -> pi(-) pi(+)pi(-) nu(tau). Assuming no contribution from B-S(0) -> tau(+) tau(-) decays, an upper limit is set on the branching fraction B(B-S(0) -> tau(+) tau(-)) < 6.8 x 10(-3) at the 95% confidence level. If instead no contribution from B-S(0) -> tau(+) tau(-) decays is assumed, the limit is B(B-s(0) -> tau(+) tau(-)) < 2.1 x 10(-3) at the 95% confidence level. These results correspond to the first direct limit on B(B-S(0) -> tau(+) tau(-)) and the world's best limit on B(B-S(0) -> tau(+) tau(-))

Abstract: We search for single-photon events in 53 fb(-1) of e(+)e(-) collision data collected with the BABAR detector at the PEP-II B-Factory. We look for events with a single high-energy photon and a large missing momentum and energy, consistent with production of a spin-1 particle A' through the process e(+)e(-) -> gamma A'; A' -> invisible. Such particles, referred to as “dark photons,” are motivated by theories applying a U(1) gauge symmetry to dark matter. We find no evidence for such processes and set 90% confidence level upper limits on the coupling strength of A' to e(+)e(-) in the mass range m(A') <= 8 GeV. In particular, our limits exclude the values of the A' coupling suggested by the dark-photon interpretation of the muon (g – 2)(mu) anomaly, as well as a broad range of parameters for the dark-sector models.

Abstract: Using proton-proton collision data corresponding to an integrated luminosity of 3.0 fb(-1), recorded by the LHCb detector at center-of-mass energies of 7 and 8 TeV, the B-c(+) -> (DK+)-K-0 decay is observed with a statistical significance of 5.1 standard deviations. By normalizing to B-c(+) -> (D) over bar (0)pi(+) decays, a measurement of the branching fraction multiplied by the production rates for B-c(+) relative to B+ mesons in the LHCb acceptance is obtained, R-D0K = (f(c)/f(u)) x B(B-c(+) -> (DK+)-K-0) = (9.3(-2.5)(+2.8) +/- 0.6) x 10(-7), where the first uncertainty is statistical and the second is systematic. This decay is expected to proceed predominantly through weak annihilation and penguin amplitudes, and is the first B-c(+) decay of this nature to be observed.

Abstract: Measurements of the cross section for producing b quarks in the reaction pp -> b (b) over barX are reported in 7 and 13 TeV collisions at the LHC as a function of the pseudorapidity. in the range 2 < eta < 5 covered by the acceptance of the LHCb experiment. The measurements are done using semileptonic decays of b-flavored hadrons decaying into a ground-state charmed hadron in association with a muon. The cross sections in the covered. range are 72.0 +/- 0.3 +/- 6.8 and 154.3 +/- 1.5 +/- 14.3 +/- μb for 7 and 13 TeV. The ratio is 2.14 +/- 0.02 +/- 0.13, where the quoted uncertainties are statistical and systematic, respectively. The agreement with theoretical expectation is good at 7 TeV, but differs somewhat at 13 TeV. The measured ratio of cross sections is larger at lower eta than the model prediction.

Abstract: MoEDAL is designed to identify new physics in the form of long-lived highly ionizing particles produced in high-energy LHC collisions. Its arrays of plastic nuclear-track detectors and aluminium trapping volumes provide two independent passive detection techniques. We present here the results of a first search for magnetic monopole production in 13 TeV proton-proton collisions using the trapping technique, extending a previous publication with 8 TeV data during LHC Run 1. A total of 222 kg of MoEDAL trapping detector samples was exposed in the forward region and analyzed by searching for induced persistent currents after passage through a superconducting magnetometer. Magnetic charges exceeding half the Dirac charge are excluded in all samples and limits are placed for the first time on the production of magnetic monopoles in 13 TeV pp collisions. The search probes mass ranges previously inaccessible to collider experiments for up to five times the Dirac charge.