Observation of an Excited Bc+ State

Using pp collision data corresponding to an integrated luminosity of 8.5 fb-1 recorded by the LHCb experiment at center-of-mass energies of s=7, 8, and 13 TeV, the observation of an excited Bc+ state in the Bc+π+π- invariant-mass spectrum is reported. The observed peak has a mass of 6841.2±0.6(stat)±0.1(syst)±0.8(Bc+) MeV/c2, where the last uncertainty is due to the limited knowledge of the Bc+ mass. It is consistent with expectations of the Bc∗(2S31)+ state reconstructed without the low-energy photon from the Bc∗(1S31)+→Bc+γ decay following Bc∗(2S31)+→Bc∗(1S31)+π+π-. A second state is seen with a global (local) statistical significance of 2.2σ (3.2σ) and a mass of 6872.1±1.3(stat)±0.1(syst)±0.8(Bc+) MeV/c2, and is consistent with the Bc(2S10)+ state. These mass measurements are the most precise to date

Updated Determination of D⁰–D¯⁰Mixing and CP Violation Parameters with D⁰→K⁺π⁻ Decays

We report measurements of charm-mixing parameters based on the decay-time-dependent ratio of D⁰→K⁺π⁻ to D⁰→K⁻π⁺ rates. The analysis uses a data sample of proton-proton collisions corresponding to an integrated luminosity of 5.0  fb⁻¹ recorded by the LHCb experiment from 2011 through 2016. Assuming charge-parity (CP) symmetry, the mixing parameters are determined to be x′²=(3.9±2.7)×10⁻⁵, y′=(5.28±0.52)×10⁻³, and R[subscript D]=(3.454±0.031)×10⁻³. Without this assumption, the measurement is performed separately for D⁰ and D[over ¯]⁰ mesons, yielding a direct CP-violating asymmetry A[subscript D]=(-0.1±9.1)×10⁻³, and magnitude of the ratio of mixing parameters 1.00<|q/p|<1.35 at the 68.3% confidence level. All results include statistical and systematic uncertainties and improve significantly upon previous single-measurement determinations. No evidence for CP violation in charm mixing is observed

Updated determination of D 0 - D 0 mixing and C P violation parameters with D 0 → K + π -

We report measurements of charm-mixing parameters based on the decay-time-dependent ratio of D0→K+π- to D0→K-π+ rates. The analysis uses a data sample of proton-proton collisions corresponding to an integrated luminosity of 5.0 fb-1 recorded by the LHCb experiment from 2011 through 2016. Assuming charge-parity (CP) symmetry, the mixing parameters are determined to be x′2=(3.9±2.7)×10-5, y′=(5.28±0.52)×10-3, and RD=(3.454±0.031)×10-3. Without this assumption, the measurement is performed separately for D0 and D0 mesons, yielding a direct CP-violating asymmetry AD=(-0.1±9.1)×10-3, and magnitude of the ratio of mixing parameters 1.00<|q/p|<1.35 at the 68.3% confidence level. All results include statistical and systematic uncertainties and improve significantly upon previous single-measurement determinations. No evidence for CP violation in charm mixing is observed

Measurement of the branching fraction and CP asymmetry in B plus . J/.. plus decays

The branching fraction and direct $C\!P$ asymmetry of the decay $B^{+}\rightarrow J/\psi \rho^{+}$ are measured using proton-proton collision data collected with the LHCb detector at centre-of-mass energies of 7 and 8 TeV, corresponding to a total integrated luminosity of 3\mbox{fb}^{-1}. The following results are obtained: \begin{align} \mathcal{B}(B^{+}\rightarrow J/\psi \rho^{+}) &= (3.81 ^{+0.25}_{-0.24} \pm 0.35) \times 10^{-5}, \nonumber \\ \mathcal{A}^{C\!P} (B^{+}\rightarrow J/\psi \rho^{+}) &= -0.045^{+0.056}_{-0.057} \pm 0.008, \nonumber \end{align} where the first uncertainties are statistical and the second systematic. Both measurements are the most precise to date.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2018-036.htm

Search for CPCP violation through an amplitude analysis of D0→K+K−π+π−D^0 \to K^+ K^- \pi^+ \pi^- decays

International audienceA search for CP violation in the Cabibbo-suppressed D$^{0}$ → K$^{+}$K$^{−}$π$^{+}$π$^{−}$ decay mode is performed using an amplitude analysis. The measurement uses a sample of pp collisions recorded by the LHCb experiment during 2011 and 2012, corresponding to an integrated luminosity of 3.0 fb$^{−1}$. The D$^{0}$ mesons are reconstructed from semileptonic b-hadron decays into D$^{0}$μ$^{−}$X final states. The selected sample contains more than 160 000 signal decays, allowing the most precise amplitude modelling of this D$^{0}$ decay to date. The obtained amplitude model is used to perform the search for CP violation. The result is compatible with CP symmetry, with a sensitivity ranging from 1% to 15% depending on the amplitude considered

Observation of CP Violation in Charm Decays

A search for charge-parity (CP) violation in D-0 -&gt; K-K+ and D-0 -&gt; pi(-)pi(+) decays is reported, using pp collision data corresponding to an integrated luminosity of 5.9 fb(-1) collected at a center-of-mass energy of 13 TeV with the LHCb detector. The flavor of the charm meson is inferred from the charge of the pion in D* (2010)(+) -&gt; D-0 pi(+) decays or from the charge of the muon in (B) over bar -&gt; D-0 mu(-)(nu) over bar X-mu decays. The difference between the CP asymmetries in D-0 -&gt; K-K+ and D-0 -&gt; pi(-)pi(+) decays is measured to be Delta A(CP) = [-18.2 +/- 3.2(stat) +/- 0.9(syst)] x 10(-4) for pi-tagged and Delta A(CP) = [-9 +/- 8(stat) +/- 5(syst)] x 10(-4) for mu-tagged D-0 mesons. Combining these with previous LHCb results leads to Delta A(CP) = (-15.4 +/- 2.9) x 10(-4), where the uncertainty includes both statistical and systematic contributions. The measured value differs from zero by more than 5 standard deviations. This is the first observation of CP violation in the decay of charm hadrons

Search for beautiful tetraquarks in the <i>ϒ</i>(1<i>S</i>)μ⁺μ⁻ invariant-mass spectrum

International audienceThe ϒ(1S)μ$^{+}$μ$^{−}$ invariant-mass distribution is investigated for a possible exotic meson state composed of two b quarks and two $\overline{b}$ quarks, ${X}_{b\overline{b}b\overline{b}}$ . The analysis is based on a data sample of pp collisions recorded with the LHCb detector at centre-of-mass energies $\sqrt{s}=7$ , 8 and 13 TeV, corresponding to an integrated luminosity of 6.3 fb$^{−1}$. No significant excess is found, and upper limits are set on the product of the production cross-section and the branching fraction as functions of the mass of the ${X}_{b\overline{b}b\overline{b}}$ state. The limits are set in the fiducial volume where all muons have pseudorapidity in the range [2.0, 5.0], and the ${X}_{b\overline{b}b\overline{b}}$ state has rapidity in the range [2.0, 4.5] and transverse momentum less than 15 GeV/c

Evidence for an ηc(1 S) π- resonance in B0→ ηc(1 S) K+π- decays

A Dalitz plot analysis of B0→ηc(1S)K+π- decays is performed using data samples of pp collisions collected with the LHCb detector at centre-of-mass energies of s=7,8 and 13TeV, corresponding to a total integrated luminosity of 4.7fb-1. A satisfactory description of the data is obtained when including a contribution representing an exotic ηc(1 S) π- resonant state. The significance of this exotic resonance is more than three standard deviations, while its mass and width are 4096±20-22+18MeV and 152±58-35+60MeV, respectively. The spin-parity assignments JP= 0 + and JP= 1 - are both consistent with the data. In addition, the first measurement of the B0→ηc(1S)K+π- branching fraction is performed and gives B(B0→ηc(1S)K+π-)=(5.73±0.24±0.13±0.66)×10-4,where the first uncertainty is statistical, the second systematic, and the third is due to limited knowledge of external branching fractions

Measurement of CP -violating and mixing-induced observables in Bs0→ϕγ decays

A time-dependent analysis of the B 0 s → ϕ γ decay rate is performed to determine the C P -violating observables S ϕ γ and C ϕ γ and the mixing-induced observable A Δ ϕ γ . The measurement is based on a sample of p p 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 S ϕ γ = 0.43 ± 0.30 ± 0.11 , C ϕ γ = 0.11 ± 0.29 ± 0.11 , and A Δ ϕ γ = − 0.67 + 0.37 − 0.41 ± 0.17 , where the first uncertainty is statistical and the second systematic. This is the first measurement of the observables S and C in radiative B 0 s decays. The results are consistent with the standard model predictions