The branching fraction of the rare decay $Λ_b^0 \rightarrow Λμ^+ μ^-$ is measured as a function of $q^2$, the square of the dimuon invariant mass. The analysis is performed using proton-proton collision data, corresponding to an integrated luminosity of 3.0 fb$^{-1}$, collected by the LHCb experiment. Evidence of signal is found for the first time in the $q^2$ region below the square of the J/$ψ$ mass. In the $q^2$ intervals where the signal is observed, angular distributions are studied and two forward-backward asymmetries, in the dimuon and hadronic systems, are measured for the first time.
The latest and improved measurements in $B^0_{(s)}\rightarrowμ^+ μ^-$ processes have been performed by LHCb using full Run 1 and Run 2 data. The measurement of the branching fraction of $B^0_{s}\rightarrowμ^+ μ^-$ is presented as the most precise single experiment measurement of such a rare process. While no significant excess is found for $B^0\rightarrowμ^+ μ^-$, an stringent upper limit is set for its braching fraction. Both results are in agreement with SM predictions and with previous results.
Recent measurements of mixing and $CP$ violation in charm decays at LHCb are presented. These include searches for direct $CP$ violation in $D^{0}\rightarrow K_{S}^{0}K_{S}^{0}$, $D_{(s)}^{+}\rightarrow h^{+} π^{0} $ and $D_{(s)}^{+}\rightarrow h^{+}η$ decays, and a search for time-dependent $CP$ violation in $D^{0}\rightarrow h^{+}h^{-}$ decays, where $h^{+}$ is either a $π^{+}$ or $K^{+}$ meson.
LHCb has productive studies of quarkonia and $b$-hadrons which provide essential inputs to study quantum chromodynamics (QCD). In this proceeding, seven recent results are reported: the observation of a new excited $Ξ_b^0$ resonance in $Ξ_b^- π^+$ final states, the new excited $B_s^0$ state is observed in $B^+ K^-$ mass spectrum, the first observation of suppressed semileptonic $B_s^0 \rightarrow K^- μ^+ ν_μ$ decay, the first observation of the decay $B^0 \rightarrow D^0 \bar{D}^0 K^+ π^-$, the first observation of the Cabibbo-suppressed decay $Λ_b^0 \rightarrow χ_{c1} p π^-$, the first observ…
One of the main goals of the LHCb experiment is to determine the mixing-induced $CP$ violating phase $ϕ_s$ in $b \rightarrow c\bar{c}s$ transitions. Assuming the Standard Model, $ϕ_s$ is precisely predicted, hence new physics could easily affect the measurement. The most precise single measurement using $B^0_s \rightarrow J/ψK^+K^-$ data collected in 2015 and 2016 is presented along with a total combined value including all LHCb $ϕ_s^{c\bar{c}s}$ analyses. The result is further combined with Tevatron and other LHC experimental results.
The $B_s^0-\bar{B}_s^0$ system can be used to look for new sources of CP violation. Time-dependent CP violation measurements of beauty mesons allow the determination of the mixing induced CP-violating phase, $ϕ_s$. The angular analysis of the $B_s^0\rightarrow ϕϕ$ decay is presented, along with two $B_s^0\rightarrow J/ψh^+h^-$ decays, where the two hadrons are either a pair of kaons or a pair of pions. The analyses are based on data collected with the LHCb detector between $2011$ and $2016$.
New results on the search for $B^0_s\rightarrow μ^+μ^-$ from LHCb
利用LHCb实验，使用在$\sqrt s=8$收集的1.1\，fb $^{-1}$数据，对稀有衰变$B^0_s\rightarrow μ^+μ^-$和$B^0\rightarrow μ^+μ^-$进行搜索，TeV $ and 1.0\,fb$ ^{-1} $ of data collected at $ \sqrt s=7 $\,TeV. An excess of $ B^0_s \rightarrow μ^+μ^- $ candidates with respect to the background expectations is observed with a statistical significance of 3.5 standard deviations. A branching fraction of $ { \cal BR}（B^0_s \rightarrow μ^+μ^-）=（3.2^{+1.5}_{-1.2}）\times 10^{-9} $ is measured with an unbinned maximum likelihood fit. The measured branching fraction is in agreement with the expectation from the Standard Model. The observed n…
Two measurements of mixing and $CP$ violation in charm decays performed at the LHCb experiment are presented. The former is a measurement of the mixing observable $y_{CP}-y_{CP}^{Kπ}$ in two-body $D^0$ decays, while the latter is a search for direct $CP$ violation in $D^+_{(s)}\rightarrowη^{(')}π^+$ decays.
This article discusses tests of lepton flavour universality that are carried out with the LHCb experiment. The experimental situation of \btosll and $b \to c \ell ν$ decays is summarised.
A search for $Σ^+ \to p μ^+ μ^-$ decays with LHCb Run 1 data is presented, yielding an evidence for this decay and a measurement of a branching fraction compatible with the Standard Model. The HyperCP anomaly in the dimuon invariant mass distribution is not confirmed, and its branching fraction central value is excluded at 95\% CL. Prospects for the future of this measurement in LHCb are also presented.
A review of the experimental status of purely leptonic ${B^0_{[s]}\to\ell^+\ell^-}$ decays is given and the new analysis of ${B^0_{[s]}\toμ^+μ^-}$ observables with the LHCb experiment is presented. The new results are the most precise single experiment measurements of the quantities to date and are consistent with the Standard Model. However, they also match the recent anomalies found in $b\to s\ell\ell$ transitions excellently.
Flavour-changing neutral-current processes, such as $b\to s \ell^+\ell^-$, are forbidden at tree level in the Standard Model and hence might receive comparatively large corrections from new particles. This document highlights recent measurements from LHCb on $b\to s \ell^+\ell^-$ and purely-leptonic decays, including tests of lepton flavour universality and searches for lepton flavour violation.
