Measurement of CP observables in B-+/- -> DK +/- and B-+/- -> D pi(+/-) with D -> KS0<mml:msup>K +/-</mml:msup><mml:msup>pi -/+</mml:msup> decays

Measurements of $CP$ observables in $B^\pm \to D K^\pm$ and $B^\pm \to D \pi^\pm$ decays are presented, where $D$ represents a superposition of $D^0$ and $\bar{D}^0$ states. The $D$ meson is reconstructed in the three-body final state $K_{\rm{S}}^0K^\pm \pi^\mp$. The analysis uses samples of $B$ mesons produced in proton-proton collisions, corresponding to an integrated luminosity of 1.0, 2.0, and 6.0 fb$^{-1}$ collected with the LHCb detector at centre-of-mass energies of $\sqrt{s} =$ 7, 8, and 13 TeV, respectively. These measurements are the most precise to date, and provide important input for the determination of the CKM angle $\gamma$

Measurement of the electron reconstruction efficiency at LHCb

The single electron track-reconstruction efficiency is calibrated using a sample corresponding to 1.3 fb−1 of pp collision data recorded with the LHCb detector in 2017. This measurement exploits B+→ J/ψ(e+e−)K+ decays, where one of the electrons is fully reconstructed and paired with the kaon, while the other electron is reconstructed using only the information of the vertex detector. Despite this partial reconstruction, kinematic and geometric constraints allow the B meson mass to be reconstructed and the signal to be well separated from backgrounds. This in turn allows the electron reconstruction efficiency to be measured by matching the partial track segment found in the vertex detector to tracks found by LHCb's regular reconstruction algorithms. The agreement between data and simulation is evaluated, and corrections are derived for simulated electrons in bins of kinematics. These correction factors allow LHCb to measure branching fractions involving single electrons with a systematic uncertainty below 1%

Search for the rare decay D-0 -> mu(+) mu(-)

A search for the rare decay D-0 -> mu(+) mu(-) is performed using a data sample, corresponding to an integrated luminosity of 0.9 fb(-1), of pp collisions collected at a centre-of-mass energy of 7 TeV by the LHCb experiment. The observed number of events is consistent with the background expectations and corresponds to an upper limit of B(D-0 -> mu(+) mu(-)) < 6.2 (7.6) x 10(-9) at 90% (95%) confidence level. This result represents an improvement of more than a factor twenty with respect to previous measurements. (C) 2013 CERN. Published by Elsevier B.V. All rights reserved

Measurement of CP-Averaged Observables in the B-0 -> K-star 0 mu(+)mu(-) Decay

An angular analysis of the B-0 -&gt; K-0 (-&gt; K+pi(-))mu(+)mu(-) decay is presented using a dataset corresponding to an integrated luminosity of 4.7 fb(-1) of pp collision data collected with the LHCb experiment. The full set of CP-averaged observables are determined in bins of the invariant mass squared of the dimuon system. Contamination from decays with the K+ pi(-) system in an S-wave configuration is taken into account. The tension seen between the previous LHCb results and the standard model predictions persists with the new data. The precise value of the significance of this tension depends on the choice of theory nuisance parameters

First Observation of the Radiative Decay Lambda(0 )(b)-> Lambda gamma

The radiative decay Λ0b→Λγ is observed for the first time using a data sample of proton-proton collisions corresponding to an integrated luminosity of 1.7  fb−1 collected by the LHCb experiment at a center-of-mass energy of 13 TeV. Its branching fraction is measured exploiting the B0→K*0γ decay as a normalization mode and is found to be B(Λ0b→Λγ)=(7.1±1.5±0.6±0.7)×10−6, where the quoted uncertainties are statistical, systematic, and systematic from external inputs, respectively. This is the first observation of a radiative decay of a beauty baryon

Observation of new resonances in th lambda(0)(b)pi(+)pi(-) system

We report the observation of a new structure in the Λ 0 b π + π − spectrum using the full LHCb data set of p p collisions, corresponding to an integrated luminosity of 9     fb − 1 , collected at √ s = 7 , 8, and 13 TeV. A study of the structure suggests its interpretation as a superposition of two almost degenerate narrow states. The masses and widths of these states are measured to be m Λ b ( 6146 ) 0 = 6146.17 ± 0.33 ± 0.22 ± 0.16     MeV , m Λ b ( 6152 ) 0 = 6152.51 ± 0.26 ± 0.22 ± 0.16     MeV , Γ Λ b ( 6146 ) 0 = 2.9 ± 1.3 ± 0.3     MeV , Γ Λ b ( 6152 ) 0 = 2.1 ± 0.8 ± 0.3     MeV , with a mass splitting of Δ m = 6.34 ± 0.32 ± 0.02     MeV , where the first uncertainty is statistical, the second systematic. The third uncertainty for the mass measurements derives from the knowledge of the mass of the Λ 0 b baryon. The measured masses and widths of these new excited states suggest their possible interpretation as a doublet of Λ b ( 1 D ) 0 states

Measurement of the electron reconstruction efficiency at LHCb

The single electron track-reconstruction efficiency is calibrated using a sample corresponding to 1.3 fb−1 of pp collision data recorded with the LHCb detector in 2017. This measurement exploits B+→ J/ψ(e+e−)K+ decays, where one of the electrons is fully reconstructed and paired with the kaon, while the other electron is reconstructed using only the information of the vertex detector. Despite this partial reconstruction, kinematic and geometric constraints allow the B meson mass to be reconstructed and the signal to be well separated from backgrounds. This in turn allows the electron reconstruction efficiency to be measured by matching the partial track segment found in the vertex detector to tracks found by LHCb's regular reconstruction algorithms. The agreement between data and simulation is evaluated, and corrections are derived for simulated electrons in bins of kinematics. These correction factors allow LHCb to measure branching fractions involving single electrons with a systematic uncertainty below 1%

Observation of new resonances in th lambda(0)(b)pi(+)pi(-) system

We report the observation of a new structure in the Λ 0 b π + π − spectrum using the full LHCb data set of p p collisions, corresponding to an integrated luminosity of 9     fb − 1 , collected at √ s = 7 , 8, and 13 TeV. A study of the structure suggests its interpretation as a superposition of two almost degenerate narrow states. The masses and widths of these states are measured to be m Λ b ( 6146 ) 0 = 6146.17 ± 0.33 ± 0.22 ± 0.16     MeV , m Λ b ( 6152 ) 0 = 6152.51 ± 0.26 ± 0.22 ± 0.16     MeV , Γ Λ b ( 6146 ) 0 = 2.9 ± 1.3 ± 0.3     MeV , Γ Λ b ( 6152 ) 0 = 2.1 ± 0.8 ± 0.3     MeV , with a mass splitting of Δ m = 6.34 ± 0.32 ± 0.02     MeV , where the first uncertainty is statistical, the second systematic. The third uncertainty for the mass measurements derives from the knowledge of the mass of the Λ 0 b baryon. The measured masses and widths of these new excited states suggest their possible interpretation as a doublet of Λ b ( 1 D ) 0 states