The results of an amplitude analysis of the charmless three-body decay $B^+ rightarrow pi^+pi^+pi^-$, in which $C!P$-violation effects are taken into account, are reported. The analysis is based on a data sample corresponding to an integrated luminos
ity of $3 text{fb}^{-1}$ of $pp$ collisions recorded with the LHCb detector. The most challenging aspect of the analysis is the description of the behaviour of the $pi^+ pi^-$ S-wave contribution, which is achieved by using three complementary approaches based on the isobar model, the K-matrix formalism, and a quasi-model-independent procedure. Additional resonant contributions for all three methods are described using a common isobar model, and include the $rho(770)^0$, $omega(782)$ and $rho(1450)^0$ resonances in the $pi^+pi^-$ P-wave, the $f_2(1270)$ resonance in the $pi^+pi^-$ D-wave, and the $rho_3(1690)^0$ resonance in the $pi^+pi^-$ F-wave. Significant $C!P$-violation effects are observed in both S- and D-waves, as well as in the interference between the S- and P-waves. The results from all three approaches agree and provide new insight into the dynamics and the origin of $C!P$-violation effects in $B^+ rightarrow pi^+pi^+pi^-$ decays.
Observations are reported of different sources of $CP$ violation from an amplitude analysis of $B^+ to pi^+ pi^+ pi^-$ decays, based on a data sample corresponding to an integrated luminosity of $3 ; {rm fb}^{-1}$ of $pp$ collisions recorded with the
LHCb detector. A large $CP$ asymmetry is observed in the decay amplitude involving the tensor $f_2(1270)$ resonance, and in addition significant $CP$ violation is found in the $pi^+ pi^-$ S-wave at low invariant mass. The presence of $CP$ violation related to interference between the $pi^+ pi^-$ S-wave and the P-wave $B^+ to rho(770)^0 pi^+$ amplitude is also established; this causes large local asymmetries but cancels when integrated over the phase space of the decay. The results provide both qualitative and quantitative new insights into $CP$-violation effects in hadronic $B$ decays.
The cross-sections of $psi(2S)$ meson production in proton-proton collisions at $sqrt{s}=13~mathrm{TeV}$ are measured with a data sample collected by the LHCb detector corresponding to an integrated luminosity of $275~pmathrm{b}^{-1}$. The production
cross-sections for prompt $psi(2S)$ mesons and those for $psi(2S)$ mesons from $b$-hadron decays ($psi{(2S)}mathrm{-from-}b$) are determined as functions of the transverse momentum, $p_{mathrm{T}}$, and the rapidity, $y$, of the $psi(2S)$ meson in the kinematic range $2<p_{mathrm{T}}<20~mathrm{GeV}/c$ and $2.0<y<4.5$. The production cross-sections integrated over this kinematic region are begin{equation*} begin{split} sigma(mbox{prompt }psi(2S),13~mathrm{TeV}) &= {1.430 pm 0.005(mathrm{stat}) pm 0.099 (mathrm{syst})mumathrm{b}}, sigma(psi(2S)mathrm{-from-}b,13~mathrm{TeV})&={0.426 pm 0.002(mathrm{stat}) pm0.030 (mathrm{syst})mumathrm{b}}. end{split} end{equation*} A new measurement of $psi(2S)$ production cross-sections in $pp$ collisions at $sqrt{s}=7~mathrm{TeV}$ is also performed using data collected in 2011, corresponding to an integrated luminosity of $614~{pmathrm{b}^{-1}}$.The integrated production cross-sections in the kinematic range $3.5<p_{mathrm{T}}<14~mathrm{GeV}/c$ and $2.0<y<4.5$ are begin{equation*} begin{split} sigma(mbox{prompt }psi(2S),7~mathrm{TeV}) &={0.471 pm0.001 (mathrm{stat}) pm 0.025 (mathrm{syst})mumathrm{b}}, sigma(psi(2S)mathrm{-from-}b,7~mathrm{TeV}) &={0.126pm0.001 (mathrm{stat}) pm0.008 (mathrm{syst})mumathrm{b}}. end{split} end{equation*} All results show reasonable agreement with theoretical calculations.
A measurement of the time-dependent CP-violating asymmetry in $B_s^0rightarrowphiphi$ decays is presented. Using a sample of proton-proton collision data corresponding to an integrated luminosity of $5.0$fb$^{-1}$ collected by the $mbox{LHCb}$ experi
ment at centre-of-mass energies $sqrt{s} = 7$ TeV in 2011, 8 TeV in 2012 and 13 TeV in 2015 and 2016, a signal yield of around 9000 $B_s^0rightarrowphiphi$ decays is obtained. The CP-violating phase $phi_s^{sbar{s}s}$ is measured to be $-0.073 pm 0.115$(stat)$pm 0.027$(syst) rad, under the assumption it is independent on the helicity of the $phiphi$ decay. In addition, the CP-violating phases of the transverse polarisations under the assumption of CP conservation of the longitudinal phase are measured. The helicity-independent direct CP-violation parameter is also measured, and is found to be $|lambda|=0.99 pm 0.05 $(stat)$ pm 0.01 $(syst). In addition, $T$-odd triple-product asymmetries are measured. The results obtained are consistent with the hypothesis of CP conservation in $brightarrowbar{s}sbar{s}$ transitions. Finally, a limit on the branching fraction of the $B^0rightarrow phiphi$ decay is determined to be $mathcal{B}(B^0rightarrow phiphi)<2.7times 10^{-8}$ at 90% confidence level.
We report measurements of the lifetimes of the $Lambda_c^+$, $Xi_c^+$ and $Xi_c^0$ charm baryons using proton-proton collision data at center-of-mass energies of 7 and 8tev, corresponding to an integrated luminosity of 3.0 fb$^{-1}$, collected by the
LHCb experiment. The charm baryons are reconstructed through the decays $Lambda_c^+to pK^-pi^+$, $Xi_c^+to pK^-pi^+$ and $Xi_c^0to pK^-K^-pi^+$, and originate from semimuonic decays of beauty baryons. The lifetimes are measured relative to that of the $D^+$ meson, and are determined to be begin{align*} tau_{Lambda_c^+} &= 203.5pm1.0pm1.3pm1.4~{rm fs}, ewline tau_{Xi_c^+} &= 456.8pm3.5pm2.9pm3.1~{rm fs}, ewline tau_{Xi_c^0} &= 154.5pm1.7pm1.6pm1.0~{rm fs}, end{align*} where the uncertainties are statistical, systematic, and due to the uncertainty in the $D^+$ lifetime. The measurements are approximately 3--4 times more precise than the current world average values. The $Lambda_c^+$ and $Xi_c^+$ lifetimes are in agreement with previous measurements; however, the $Xi_c^0$ baryon lifetime is approximately 3.3 standard deviations larger than the world average value.
Measurements of $C!P$ observables in $B^0 to DK^{*0}$ decays are presented, where $D$ represents a superposition of $D^0$ and $bar{D}^0$ states. The $D$ meson is reconstructed in the two-body final states $K^+pi^-$, $pi^+ K^-$, $K^+K^-$ and $pi^+pi^-
$, and, for the first time, in the four-body final states $K^+pi^-pi^+pi^-$, $pi^+ K^-pi^+pi^-$ and $pi^+pi^-pi^+pi^-$. The analysis uses a sample of neutral $B$ mesons produced in proton-proton collisions, corresponding to an integrated luminosity of 1.0, 2.0 and 1.8 $rm fb^{-1}$ collected with the LHCb detector at centre-of-mass energies of $sqrt{s} = $ 7, 8 and 13 TeV, respectively. First observations of the decays $B^0 to D(pi^+ K^-)K^{*0}$ and $B^0 to D(pi^+pi^-pi^+pi^-)K^{*0}$ are obtained. The measured observables are interpreted in terms of the $C!P$-violating weak phase $gamma$.
The first amplitude analysis of the $B^pm to pi^pm K^+ K^-$ decay is reported based on a data sample corresponding to an integrated luminosity of 3.0 fb$^{-1}$ of $pp$ collisions recorded in 2011 and 2012 with the LHCb detector. The data is found to
be best described by a coherent sum of five resonant structures plus a nonresonant component and a contribution from $pipi leftrightarrow KK$ $S$-wave rescattering. The dominant contributions in the $pi^pm K^mp$ and $K^{+}K^{-}$ systems are the nonresonant and the $B^pm to rho(1450)^{0}pi^{pm}$ amplitudes, respectively, with fit fractions around $30%$. For the rescattering contribution, a sizeable fit fraction is observed. This component has the largest $CP$ asymmetry reported to date for a single amplitude of $(-66 pm 4 pm 2)%$, where the first uncertainty is statistical and the second systematic. No significant $CP$ violation is observed in the other contributions.
The $B^0 to K^{*0} overline{K}^{*0}$ and $B^0_s to K^{*0} overline{K}^{*0}$ decays are studied using proton-proton collision data corresponding to an integrated luminosity of 3fb$^{-1}$. An untagged and time-integrated amplitude analysis of $B^0_{(s)
} to (K^+pi^-)(K^-pi^+) $ decays in two-body invariant mass regions of 150 MeV$/c^2$ around the $K^{*0}$ mass is performed. A stronger longitudinal polarisation fraction in the ${B^0 to K^{*0} overline{K}^{*0}}$ decay, ${f_L = 0.724 pm 0.051 ,({rm stat}) pm 0.016 ,({rm syst})}$, is observed as compared to ${f_L = 0.240 pm 0.031 ,({rm stat}) pm 0.025 ,({rm syst})}$ in the ${B^0_sto K^{*0} overline{K}^{*0}}$ decay. The ratio of branching fractions of the two decays is measured and used to determine $mathcal{B}(B^0 to K^{*0} overline{K}^{*0}) = (8.0 pm 0.9 ,({rm stat}) pm 0.4 ,({rm syst})) times 10^{-7}$.
A search for $B^{0}_{s}totau^{pm}mu^{mp}$ and $B^{0}totau^{pm}mu^{mp}$ decays is performed using data corresponding to an integrated luminosity of 3 fb$^{-1}$ of proton-proton collisions, recorded with the LHCb detector in 2011 and 2012. For this sea
rch, the $tau$ lepton is reconstructed in the $tau^{-}topi^{-}pi^{+}pi^{-} u_{tau}$ channel. No significant signal is observed. Assuming no contribution from $B^{0}totau^{pm}mu^{mp}$ decays, an upper limit is set on the $B^{0}_{s}totau^{pm}mu^{mp}$ branching fraction of $mathcal{B}left( B^{0}_{s}totau^{pm}mu^{mp}right) < 4.2times 10^{-5}$ at $95%$ confidence level. If instead no contribution from $B^{0}_{s}totau^{pm}mu^{mp}$ decays is assumed, a limit of $mathcal{B}left( B^{0}totau^{pm}mu^{mp}right) < 1.4times 10^{-5}$ is obtained at $95%$ confidence level. These are the first limit on $mathcal{B}left( B^{0}_{s}totau^{pm}mu^{mp}right)$ and the worlds best limit on $mathcal{B}left( B^{0}totau^{pm}mu^{mp}right)$.
A time-dependent analysis of the $B_s^0 to phigamma$ decay rate is performed to determine the $CP$-violating observables $S_{phigamma}$ and $C_{phigamma}$, and the mixing-induced observable $mathcal{A}^{Delta}_{phigamma}$. The measurement is based on
a sample of $pp$ collision data recorded with the LHCb detector, corresponding to an integrated luminosity of 3 fb$^{-1}$ at center-of-mass energies of 7 and 8 TeV. The measured values are begin{align*} S_{phigamma} &= 0.43 pm 0.30 pm 0.11, C_{phigamma} &= 0.11 pm 0.29 pm 0.11, mathcal{A}^{Delta}_{phigamma} &= -0.67 , ^{+0.37}_{-0.41} pm 0.17, end{align*} where the first uncertainty is statistical and the second systematic. This is the first measurement of the observables $S$ and $C$ in radiative $B_s^0$ decays. The results are consistent with the Standard Model predictions.
