Measurement of $C!P$ asymmetries in two-body $B_{(s)}^{0}$-meson decays to charged pions and kaons

The time-dependent $C!P$ asymmetries in $B^0topi^+pi^-$ and $B_s^0to K^+!K^-$ decays are measured using a data sample of $pp$ collisions corresponding to an integrated luminosity of 3.0 fb$^{-1}$, collected with the LHCb detector at centre-of-mass energies of 7 and 8 TeV. The same data sample is used to measure the time-integrated $C!P$ asymmetries in $B^0to K^+pi^-$ and $B_s^0topi^+ K^-$ decays. The results are $C_{pi^+pi^-} = -0.34 pm 0.06 pm 0.01$, $S_{pi^+pi^-} = -0.63 pm 0.05 pm 0.01$, $C_{K^+!K^-} = 0.20 pm 0.06 pm 0.02$, $S_{K^+!K^-} = 0.18 pm 0.06 pm 0.02$, $C_{K^+!K^-}^{DeltaGamma} = -0.79 pm 0.07 pm 0.10$, $A_{C!P}^{B^0} = -0.084 pm 0.004 pm 0.003$, and $A_{C!P}^{B_s^0} = 0.213 pm 0.015 pm 0.007$, where the first uncertainties are statistical and the second systematic. Evidence for $C!P$ violation is found in the $B_s^0to K^+!K^-$ decay for the first time.

Measurement of the ratio of branching fractions $mathcal{B}(B_{c}^{+} to J/psi K^{+})/mathcal{B}(B_{c}^{+} to J/psipi^{+})$

The ratio of branching fractions $R_{K/pi} equiv mathcal{B}(B_{c}^{+} to J/psi K^{+})/mathcal{B}(B_{c}^{+} to J/psipi^{+})$ is measured with $pp$ collision data collected by the LHCb experiment at centre-of-mass energies of 7 TeV and 8 TeV, corresponding to an integrated luminosity of 3${mbox{fb}^{-1}}$. It is found to be $ R_{K/pi} = 0.079pm0.007pm0.003$, where the first uncertainty is statistical and the second is systematic. This measurement is consistent with the previous LHCb result, while the uncertainties are significantly reduced.

Precision Measurement of KS Meson Lifetime with the KLOE detector

Using a large sample of pure, slow, short lived K0 mesons collected with KLOE detector at DaFne, we have measured the KS lifetime. From a fit to the proper time distribution we find tau = (89.562 +- 0.029_stat +- 0.043_syst) ps. This is the most precise measurement today in good agreement with the world average derived from previous measurements. We observe no dependence of the lifetime on the direction of the Ks.

Precision measurement of the $Xi_{cc}^{++}$ mass

A measurement of the $Xi_{cc}^{++}$ mass is performed using data collected by the LHCb experiment between 2016 and 2018 in $pp$ collisions at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.6 $mathrm{fb}^{-1}$. The $Xi_{cc}^{++}$ candidates are reconstructed via the decay modes $Xi_{cc}^{++}toLambda_c^+K^-pi^+pi^+$ and $Xi_{cc}^{++}toXi_c^+pi^+$. The result, $3621.55 pm 0.23{rm,(stat),} pm 0.30 {rm,(syst),}{rm MeV}/c^2$, is the most precise measurement of the $Xi_{cc}^{++}$ mass to date.

Precision Measurement of the Mass of the $tau$ Lepton

An energy scan near the $tau$ pair production threshold has been performed using the BESIII detector. About $24$ pb$^{-1}$ of data, distributed over four scan points, was collected. This analysis is based on $tau$ pair decays to $ee$, $emu$, $eh$, $mumu$, $mu h$, $hh$, $erho$, $murho$ and $pirho$ final states, where $h$ denotes a charged $pi$ or $K$. The mass of the $tau$ lepton is measured from a maximum likelihood fit to the $tau$ pair production cross section data to be $m_{tau} = (1776.91pm0.12 ^{+0.10}_{-0.13}$) MeV/$c^2$, which is currently the most precise value in a single measurement.