Search

A measurement of the time-integrated CP asymmetry in the Cabibbo-suppressed decay D 0 → K − K + is performed using pp collision data, corresponding to an integrated luminosity of 3 fb − 1 , collected with the LHCb detector at centre-of-mass energies of 7 and 8 TeV. The flavour of the charm meson at production is determined from the charge of the pion in D ⁎ + → D 0 π + and D ⁎ − → D ‾ 0 π − decays. The time-integrated CP asymmetry A CP ( K − K + ) is obtained assuming negligible CP violation in charm mixing and in Cabibbo-favoured D 0 → K − π + , D + → K − π + π + and D + → K ‾ 0 π + decays used as calibration channels. It is found to be A CP ( K − K + ) = ( 0.14 ± 0.15 (stat) ± 0.10 (syst) ) % . A combination of this result with previous LHCb measurements yields A CP ( K − K + ) = ( 0.04 ± 0.12 (stat) ± 0.10 (syst) ) % , A CP ( π − π + ) = ( 0.07 ± 0.14 (stat) ± 0.11 (syst) ) % . These are the most precise measurements from a single experiment. The result for A CP ( K − K + ) is the most precise determination of a time-integrated CP asymmetry in the charm sector to date, and neither measurement shows evidence of CP asymmetry. [ABSTRACT FROM AUTHOR]

Abstract: At large momentum transfers the photon interacts with the charges and spins of the constituent partons in a hadron. It is expected that the neutral kaon can acquire finite electromagnetic form factors because its wave function is affected by the order of magnitude difference between the mass of the strange quark and that of the down quark, or flavor breaking. We report on the first measurement of the form factor of neutral kaons at the large timelike momentum transfer of by measuring the cross section for at using CLEO-c data with an integrated luminosity of 586 pb−1. We obtain , with a 90% C.L. interval of . This is nearly an order of magnitude smaller than , and indicates that the effect of breaking is small. In turn, this makes it unlikely that the recently observed strong violation of the pQCD prediction, , which is based on the assumption of similar wave functions for the pions and kaons, can be attributed to breaking alone. [Copyright &y& Elsevier]

Abstract: The KLOE Collaboration recently reported bounds on the directional dependence of the lifetime of the short-lived neutral kaon with respect to the dipole anisotropy of the cosmic microwave background. We interpret their results in an effective field theory framework developed to probe the violation of Lorentz invariance in the weak interaction and previously applied to semileptonic processes, in particular β decay. In this approach a general Lorentz-violating tensor is added to the standard propagator of the W boson. We perform an exploratory study of the prospects to search for Lorentz violation in nonleptonic decays. For the kaon, we find that the sensitivity to Lorentz violation is limited by the velocity of the kaons and by the extent to which hadronic effects can be calculated. In a simple model we derive the decay rate and calculate the asymmetry for the lifetime. Using the KLOE data, limits on the values of are determined. [Copyright &y& Elsevier]

Abstract: The kaon photo-production process on 12C has been studied by measuring neutral kaons in the photon energy range of 0.8–1.1 GeV. Neutral kaons were identified by the invariant mass constructed from two charged pions emitted in the decay channel. The differential and integrated cross sections in the threshold photon energy region were obtained. The obtained momentum spectra were compared with a Spectator model calculation using elementary amplitudes of kaon photo-production given by recent isobar models. The present results provide the first information on the reaction, which is expected to play an important role in constructing models of strangeness production by electromagnetic interactions. The experimental results show that the cross section of is of the same order as that of and suggest that a slightly backward angular distribution is favored in the process. [Copyright &y& Elsevier]