Search

We propose that three recent anomalies in B meson decays, R D ( ⁎ ) , R K , and P 5 ′ , might be explained by only one vector leptoquark weak triplet state. The constraints on the parameter space are obtained by considering t → b τ + ν data, lepton flavor universality tests in the kaon sector, bounds on the lepton flavor violating decay B → K μ τ , and b → c μ − ν ¯ decays. The presence of such vector leptoquark could be exposed in precise measurements of top semitauonic decays to b quark. The model predicts enhanced decay rate of B → K ν ¯ ν , approximate equality of lepton flavor universality ratios R K ⁎ , R K , and suppressed branching fraction of B s → μ + μ − . [ABSTRACT FROM AUTHOR]

Abstract: The NA62 experiment at CERN, aiming at a precision measurement of the ultra-rare decay K + → π+νν, relies on kinematical rejection up to 105 (≈ 1012 is needed in total). One of the limiting factors to achieve this goal is the multiple scattering in the magnetic spectrometer for kaon decay products; therefore an almost massless (≈1.5% X0) straw tracker has been designed to operate in vacuum, to be able to install it inside the decay volume. A vacuum tight prototype was built and tested in 2010: efficiency (≈99%), rate capability and single straw resolution (≈200μm) were verified. The construction of the first chamber started in 2011. [Copyright &y& Elsevier]

We report a study of B -~ (J/qiy)K and B -~ (ifi'y)K decay modes using 772)< 10~ B~ events collected at the Y(4S) resonance with the Belle detector at the KEKB energy-asymmetric e~e collider. We observe X(3872) -~ J/~/iy and report the first evidence for Xc2 -* J/i/iy in B -. (X~~y)K decays, while in a search for X(3872) -~ no significant signal is found. We measure the branching fractions, B(B~ -. X(3872)K~)B(X(3872) -. J/ ~ti y) = (1.78ig~ ± 0.12) X 106, B(B~ - x~2K~) = (1.11~:~ ± 0.09) x i0~, B(B~ -~ X(3872)K~)T(X(3872) -~ ~f"y) <3.45 X 10~ (upper limit at 90% CL.), and also provide upper limits for other searches. [ABSTRACT FROM AUTHOR]

We discuss an experimental technique aimed at tagging electron neutrinos in multi-GeV artificial sources on an event-by-event basis. It exploits in a novel manner calorimetric and tracking technologies developed in the framework of the LHC experiments and of rare kaon decay searches. The setup is suited for slow-extraction, moderate power beams and it is based on an instrumented decay tunnel equipped with tagging units that intercept secondary and tertiary leptons from the bulk of undecayed π and protons. We show that the taggers are able to reduce the ν contamination originating from K decays by about one order of magnitude. Only a limited suppression (∼60%) is achieved for ν produced by the decay-in-flight of muons; for low beam powers, similar performance as for K can be reached supplementing the tagging system with an instrumented beam dump. [ABSTRACT FROM AUTHOR]

The latest results from the NA48/2 collaboration on charged kaon decays will be reviewed in this paper. The high statistics available, collected during 2003 and 2004 runs, allows the study of charged kaon decays up to branching ratios (BR) of ~ 10-8. The status of the analyses of several radiative decays (K± → π±π0γ, K± → π±γγ, K± → π±e+e-γ and K± → π±e+e-) will be discussed, including BR measurements and possible ChPT tests. [ABSTRACT FROM AUTHOR]

The KLOE experiment has finished its data taking at the e+e- collider DAΦNE in Frascati. KLOE has collected 2.5 fb-1 at the peak of the ϕ resonance, and 250 pb-1 at $\sqrt{s}=1~{\rm GeV}$. The latest experimental results based on a sample of 450 pb-1 are presented in this paper: they mainly concern the neutral and charged kaon decays, and the radiative ϕ decays into scalar and pseudoscalar mesons. [ABSTRACT FROM AUTHOR]

For high precision measurements of K decays, the presence of radiated photons cannot be neglected. The Monte Carlo simulations must include the radiative corrections in order to compute the correct event counting and for efficiency calculations. In this paper, a method for simulating such decays is briefly described. [ABSTRACT FROM AUTHOR]

We review different definitions of the &epsiv;¹ parameter describing direct CP-violation in neutral kaon decays, which was precisely measured in recent experiments, and point out the inconsistency of some of them due to a CPT-constraint. The proper comparison of the experimental results to the theoretical computations is discussed. [ABSTRACT FROM AUTHOR]

We point out that, given the current experimental status of radiative kaon decays, a subclass of the O(p4) counterterms of the weak chiral lagrangian can be determined in closed form. This involves in a decisive way the decay K±→π±π0l+l-, currently being measured at CERN by the NA48/2 and NA62 collaborations. We show that consistency with other radiative kaon decay measurements leads to a rather clean prediction for the O(p4) weak couplings entering this decay mode. This results in a characteristic pattern for the interference Dalitz plot, susceptible to be tested already with the limited statistics available at NA48/2. We also provide the first analysis of KS→π+π-γ∗, which will be measured by LHCb and will help reduce (together with the related KL decay) the experimental uncertainty on the radiative weak chiral couplings. A precise experimental determination of the O(p4) weak couplings is important in order to assess the validity of the existing theoretical models in a conclusive way. We briefly comment on the current theoretical situation and discuss the merits of the different theoretical approaches. [ABSTRACT FROM AUTHOR]