A Roadmap to Control Penguin Effects in Bd0→J/ψKS0B^0_d\to J/\psi K_{\rm S}^0 and Bs0→J/ψϕB^0_s\to J/\psi \phi

Measurements of CP violation in $B^0_d\to J/\psi K_{\rm S}^0$ and $B^0_s\to J/\psi \phi$ decays play key roles in testing the quark-flavour sector of the Standard Model. The theoretical interpretation of the corresponding observables is limited by uncertainties from doubly Cabibbo-suppressed penguin topologies. With continuously increasing experimental precision, it is mandatory to get a handle on these contributions, which cannot be calculated reliably in QCD. In the case of the measurement of $\sin2\beta$ from $B^0_d\to J/\psi K_{\rm S}^0$, the $U$-spin-related decay $B^0_s\to J/\psi K_{\rm S}^0$ offers a tool to control the penguin effects. As the required measurements are not yet available, we use data for decays with similar dynamics and the $SU(3)$ flavour symmetry to constrain the size of the expected penguin corrections. We predict the CP asymmetries of $B^0_s\to J/\psi K_{\rm S}^0$ and present a scenario to fully exploit the physics potential of this decay, emphasising also the determination of hadronic parameters and their comparison with theory. In the case of the benchmark mode $B^0_s\to J/\psi \phi$ used to determine the $B^0_s$-$\bar B^0_s$ mixing phase $\phi_s$ the penguin effects can be controlled through $B^0_d\to J/\psi \rho^0$ and $B^0_s\to J/\psi \bar{K}^{*0}$ decays. The LHCb collaboration has recently presented pioneering results on this topic. We analyse their implications and present a roadmap for controlling the penguin effects.Comment: 34 pages, 16 figures, matching published versio

Search for the Rare Decays B 0 s → e + e − and B 0 → e + e −

A search for the decays Bs0→e+e- and B0→e+e- is performed using data collected with the LHCb experiment in proton-proton collisions at center-of-mass energies of 7, 8, and 13 TeV, corresponding to integrated luminosities of 1, 2, and 2 fb-1, respectively. No signal is observed. Assuming no contribution from B0→e+e- decays, an upper limit on the branching fraction B(Bs0→e+e-)&lt;9.4(11.2)×10-9 is obtained at 90(95)% confidence level. If no Bs0→e+e- contribution is assumed, a limit of B(B0→e+e-)&lt;2.5(3.0)×10-9 is determined at 90(95)% confidence level. These upper limits are more than one order of magnitude lower than the previous values.</p

Observation of New Ξ 0 c Baryons Decaying to Λ + c K −

The Λc+K- mass spectrum is studied with a data sample of pp collisions at a center-of-mass energy of 13 TeV corresponding to an integrated luminosity of 5.6 fb-1 collected by the LHCb experiment. Three Ξc0 states are observed with a large significance and their masses and natural widths are measured to be m[Ξc(2923)0]=2923.04±0.25±0.20±0.14 MeV, Γ[Ξc(2923)0]=7.1±0.8±1.8 MeV, m[Ξc(2939)0]=2938.55±0.21±0.17±0.14 MeV, Γ[Ξc(2939)0]=10.2±0.8±1.1 MeV, m[Ξc(2965)0]=2964.88±0.26±0.14±0.14 MeV, Γ[Ξc(2965)0]=14.1±0.9±1.3 MeV, where the uncertainties are statistical, systematic, and due to the limited knowledge of the Λc+ mass. The Ξc(2923)0 and Ξc(2939)0 baryons are new states. The Ξc(2965)0 state is in the vicinity of the known Ξc(2970)0 baryon; however, their masses and natural widths differ significantly

Study of the ψ2(3823) and χc1(3872) states in B+ → (J/ψπ+π−)K+ decays

The decays B+→ J/ψπ+π−K+ are studied using a data set corresponding to an integrated luminosity of 9 fb−1 collected with the LHCb detector in proton-proton collisions between 2011 and 2018. Precise measurements of the ratios of branching fractions with the intermediate ψ2(3823), χc1(3872) and ψ(2S) states are reported. The values areBB+→ψ2(3823)K+×Bψ2(3823)→J/ψπ+π−BB+→χc1(3872)K+×Bχc1(3872)→J/ψπ+π−=(3.56±0.67±0.11)×10−2,BB+→ψ2(3823)K+×Bψ2(3823)→J/ψπ+π−BB+→ψ(2S)K+×Bψ(2S)→J/ψπ+π−=(1.31±0.25±0.04)×10−3,BB+→χc1(3872)K+×Bχc1(3872)→J/ψπ+π−BB+→ψ(2S)K+×Bψ(2S)→J/ψπ+π−=(3.69±0.07±0.06)×10−2, where the first uncertainty is statistical and the second is systematic. The decay of B+→ ψ2(3823)K+ with ψ2(3823) → J/ψπ+π− is observed for the first time with a significance of 5.1 standard deviations. The mass differences between the ψ2(3823), χc1(3872) and ψ(2S) states are measured to be mχc1(3872)−mψ2(3823)=47.50±0.53±0.13MeV/c2,mψ2(3823)−mψ2(2S)=137.98±0.53±0.14MeV/c2,mχc1(3872)−mψ2(2S)=185.49±0.06±0.03MeV/c2, resulting in the most precise determination of the χc1(3872) mass. The width of the ψ2(3823) state is found to be below 5.2 MeV at 90% confidence level. The Breit-Wigner width of the χc1(3872) state is measured to be Γχc1(3872)BW=0.96−0.18+0.19±0.21MeV which is inconsistent with zero by 5.5 standard deviations. [Figure not available: see fulltext.

Observation of a new baryon state in the Λ0bπ+π− mass spectrum

A new baryon state is observed in the Λb0π+π− mass spectrum with high significance using a data sample of pp collisions, collected with the LHCb detector at centre-of-mass energies s = 7, 8 and 13 TeV, corresponding to an integrated luminosity of 9 fb−1. The mass and natural width of the new state are measured to be m=6072.3±2.9±0.6±0.2MeV,Γ=72±11±2MeV, where the first uncertainty is statistical and the second systematic. The third uncertainty for the mass is due to imprecise knowledge of the Λb0 baryon mass. The new state is consistent with the first radial excitation of the Λb0 baryon, the Λb(2S)0 resonance. Updated measurements of the masses and the upper limits on the natural widths of the previously observed Λb(5912)0 and Λb(5920)0 states are also reported. [Figure not available: see fulltext.

First Observation of Excited Ω − b States

We report four narrow peaks in the Ξb0K- mass spectrum obtained using pp collisions at center-of-mass energies of 7, 8, and 13 TeV, corresponding to a total integrated luminosity of 9 fb-1 recorded by the LHCb experiment. Referring to these states by their mass, the mass values are m[ωb(6316)-]=6315.64±0.31±0.07±0.50 MeV, m[ωb(6330)-]=6330.30±0.28±0.07±0.50 MeV, m[ωb(6340)-]=6339.71±0.26±0.05±0.50 MeV, m[ωb(6350)-]=6349.88±0.35±0.05±0.50 MeV, where the uncertainties are statistical, systematic, and the last is due to the knowledge of the Ξb0 mass. The natural widths of the three lower mass states are consistent with zero, and the 90% confidence-level upper limits are determined to be Γ[ωb(6316)-]<2.8 MeV, Γ[ωb(6330)-]<3.1 MeV and Γ[ωb(6340)-]<1.5 MeV. The natural width of the ωb(6350)- peak is 1.4-0.8+1.0±0.1 MeV, which is 2.5σ from zero and corresponds to an upper limit of 2.8 MeV. The peaks have local significances ranging from 3.6σ to 7.2σ. After accounting for the look-elsewhere effect, the significances of the ωb(6316)- and ωb(6330)- peaks are reduced to 2.1σ and 2.6σ, respectively, while the two higher mass peaks exceed 5σ. The observed peaks are consistent with expectations for excited ωb- resonances

Measurement of C P -Averaged Observables in the B 0 → K * 0 μ + μ − Decay

An angular analysis of the B0→K*0(→K+π−)μ+μ− 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+π− 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

Measurement of CP observables in B± → DK± and B± → Dπ± with D → K0SK±π∓ decays

Measurements of CP observables in B± → DK± and B± → Dπ± decays are presented, where D represents a superposition of D0 and D¯ states. The D meson is reconstructed in the three-body final states KS0K±π∓ and KS0K∓π±. 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 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 γ. [Figure not available: see fulltext.

Search for the lepton flavour violating decay B+ → K+μ−τ+ using B∗0s2 decays

A search is presented for the lepton flavour violating decay B+ → K+μ−τ+ using a sample of proton-proton collisions at centre-of-mass energies of 7, 8, and 13 TeV, collected with the LHCb detector and corresponding to a total integrated luminosity of 9 fb−1. The τ leptons are selected inclusively, primarily via decays with a single charged particle. The four-momentum of the τ lepton is determined by using B+ mesons from Bs2∗0→B+K− decays. No significant excess is observed, and an upper limit is set on the branching fraction ℬ(B+ → K+μ−τ+) < 3.9 × 10−5 at 90 % confidence level. The obtained limit is comparable to the world-best limit. [Figure not available: see fulltext.]