Amplitude analysis of B0→D‾0Ds+π−B^0 \rightarrow \overline{D}^0 D_s^+ \pi^- and B+→D−Ds+π+B^+ \rightarrow D^- D_s^+ \pi^+ decays

Resonant contributions in $B^0 \rightarrow \overline{D}^0 D^+_s\pi^-$ and $B^+\rightarrow D^- D^+_s\pi^+$ decays are determined with an amplitude analysis, which is performed both separately and simultaneously, where in the latter case isospin symmetry between the decays is assumed. The analysis is based on data collected by the LHCb detector in proton-proton collisions at center-of-mass energies of 7, 8 and 13 $\rm{TeV}$. The full data sample corresponds to an integrated luminosity of 9 $\rm fb^{-1}$. A doubly charged spin-0 open-charm tetraquark candidate together with a neutral partner, both with masses near $2.9\,\rm{GeV}$, are observed in the $D_s\pi$ decay channel.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-027.html (LHCb public pages

Direct photon production at LHCb

At small Bjorken-x, the large gluon number density in the nucleon leads to gluon recombination competing with gluon splitting, which could result in saturation of the gluon PDF. This gluon saturation has yet to be conclusively observed. Direct photon production provides sensitivity to gluon densities in protons and nuclei, and the forward acceptance of LHCb detector allows for measurements of this process at low Bjorken-x, providing an ideal probe of saturation effects. Progress towards the measurement of forward direct photon production using the LHCb detector is presented

Highlights from the LHCb experiment

We report recent results by the LHCb collaboration in heavy-ion collisions in collider and fixed-target mode at the LHC. A large variety of measurements show the potential of LHCb in nuclear collisions

Measurement of the mass and production rate of Ξ−b baryons

The first measurement of the production rate of Xi(-)(b) baryons in pp collisions relative to that of Lambda(0 )(b)baryons is reported, using data samples collected by the LHCb experiment, and corresponding to integrated luminosities of 1, 2 and 1.6 fb(-1) at root s = 7, 8 and 13 TeV, respectively. In the kinematic region 2 < eta < 6 and p(T) < 20 GeV/c, we measure f(Xi b-)/f(Lambda b0) B(Xi(-)(b)-> J/psi Xi(-))/B(Lambda(0)(b)-> J/psi Lambda)= (10.8 +/- 0.9 +/- 0.8) x 10(-2) [root s = 7,8 TeV], f(Xi b-)/f(Lambda b0) B(Xi(-)(b)-> J/psi Xi(-))/B(Lambda(0)(b)-> J/psi Lambda) =(13.1 +/- 1.1 +/- 1.0) x 10(-2) [root s = 13 TeV], where and f(Xi b-) and f(Lambda)(b0) the fragmentation fractions of b quarks into Xi(-)(b) and Lambda(0)(b) baryons, respectively; B represents branching fractions; and the uncertainties are due to statistical and experimental systematic sources. The values of f(Xi b-)/f(Lambda b0) are obtained by invoking SU(3) symmetry in the Xi(-)(b)-> J/psi Xi(-) and Lambda(0)(b)-> J/psi Lambda decays. Production asymmetries between Xi(-)(b) and (Xi) over bar (+)(b) baryons are also reported. The mass of the Xi(-)(b) baryon is also measured relative to that of the Lambda(0)(b) baryon, from which it is found that m(Xi(-)(b)) = 5796.70 +/- 0.39 +/- 0.15 +/- 0.17 MeV/c(2), where the last uncertainty is due to the precision on the known Lambda(0)(b) mass. This result represents the most precise determination of the Xi(-)(b) mass

Search for CP violation using triple product asymmetries in Λ _b⁰ → pK⁻π⁺π⁻, Λ _b⁰ → pK−K+K− and Ξ _b⁰ → pK⁻K⁻π⁺decays

A search for $C$P and $P$ violation using triple-product asymmetries is performed with $\Lambda^{0}_{b}\to pK^{-}\pi^{+}\pi^{-}$, $\Lambda^{0}_{b}\to pK^{-}K^{+}K^{-}$ and $\Xi^{0}_{b}\to pK^{-}K^{-}\pi^{+}$ decays. The data sample corresponds to integrated luminosities of 1.0fb$^{-1}$ and 2.0fb$^{-1}$, recorded with the LHCb detector at centre-of-mass energies of 7TeV and 8TeV, respectively. The $CP$- and $P$-violating asymmetries are measured both integrating over all phase space and in specific phase-space regions. No significant deviation from $CP$ or $P$ symmetry is found. The first observation of $\Lambda^{0}_{b}\to pK^{-}\chi_{c0}(1P)(\to\pi^{+}\pi^{-}, K^{+}K^{-})$ decay is also reported.Comment: 26 pages including author list, 10 figure

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

Measurement of the ratio of branching fractions of the decays Λ0 → ψ(2S)Λ and Λ0 → J/ψΛ

Using pp collisions corresponding to 3 fb integrated luminosity, recorded by the LHCb experiment at centre- of- mass energies of 7 and 8TeV, the ratio of branching fractions B (0b ! (2 S) ) =B (0b ! J= ) = 0 : 513 0 : 023 (stat) 0 : 016 (syst) 0 : 011 (B) is determined. The fi rst uncertainty is statistical, the second is systematic and the third is due to the external branching fractions used

Measurement of the mass and production rate of Ξb− baryons

The first measurement of the production rate of Ξ − b baryons in p p collisions relative to that of Λ 0 b baryons is reported, using data samples collected by the LHCb experiment, and corresponding to integrated luminosities of 1, 2 and 1.6     fb − 1 at √ s = 7 , 8 and 13 TeV, respectively. In the kinematic region 2 < η < 6 and p T < 20     GeV / c , we measure f Ξ − b f Λ 0 b B ( Ξ − b → J / ψ Ξ − ) B ( Λ 0 b → J / ψ Λ ) = ( 10.8 ± 0.9 ± 0.8 ) × 10 − 2 [ √ s = 7 , 8     TeV ], f Ξ − b f Λ 0 b B ( Ξ − b → J / ψ Ξ − ) B ( Λ 0 b → J / ψ Λ ) = ( 13.1 ± 1.1 ± 1.0 ) × 10 − 2 [ √ s = 13     TeV ], where f Ξ − b and f Λ 0 b are the fragmentation fractions of b quarks into Ξ − b and Λ 0 b baryons, respectively; B represents branching fractions; and the uncertainties are due to statistical and experimental systematic sources. The values of f Ξ − b / f Λ 0 b are obtained by invoking SU(3) symmetry in the Ξ − b → J / ψ Ξ − and Λ 0 b → J / ψ Λ decays. Production asymmetries between Ξ − b and ¯ Ξ + b baryons are also reported. The mass of the Ξ − b baryon is also measured relative to that of the Λ 0 b baryon, from which it is found that m ( Ξ − b ) = 5796.70 ± 0.39 ± 0.15 ± 0.17     MeV / c 2 , where the last uncertainty is due to the precision on the known Λ 0 b mass. This result represents the most precise determination of the Ξ − b mass

Measurement of B+, B0 and Λb0 production in pPb collisions at √sNN=8.16 TeV

The production of B + , B 0 and Λ 0 b hadrons is studied in proton-lead collisions at a center-of-mass energy per nucleon pair of √ s NN = 8.16     TeV recorded with the LHCb detector at the LHC. The measurement uses a dataset corresponding to an integrated luminosity of 12.2 ± 0.3     nb − 1 for the case where the proton beam is projected into the LHCb detector (corresponding to measuring hadron production at positive rapidity) and 18.6 ± 0.5     nb − 1 for the lead beam projected into the LHCb detector (corresponding to measuring hadron production at negative rapidity). Double-differential cross sections are measured and used to determine forward-backward ratios and nuclear modification factors, which directly probe nuclear effects in the production of beauty hadrons. The double-differential cross sections are measured as a function of the beauty-hadron transverse momentum and rapidity in the nucleon-nucleon center-of-mass frame. Forward-to-backward cross section ratios and nuclear modification factors indicate a significant nuclear suppression at positive rapidity. The ratio of Λ 0 b over B 0 production cross sections is reported and is consistent with the corresponding measurement in p p collisions

Observation of an Excited Bc⁺ state

Using p p 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 B + c state in the B + c π + π − invariant-mass spectrum is reported. The observed peak has a mass of 6841.2 ± 0.6 ( stat ) ± 0.1 ( syst ) ± 0.8 ( B + c )     MeV / c 2 , where the last uncertainty is due to the limited knowledge of the B + c mass. It is consistent with expectations of the B ∗ c ( 2 3 S 1 ) + state reconstructed without the low-energy photon from the B ∗ c ( 1 3 S 1 ) + → B + c γ decay following B ∗ c ( 2 3 S 1 ) + → B ∗ c ( 1 3 S 1 ) + π + π − . A second state is seen with a global (local) statistical significance of 2.2 σ ( 3.2 σ ) and a mass of 6872.1 ± 1.3 ( stat ) ± 0.1 ( syst ) ± 0.8 ( B + c )     MeV / c 2 , and is consistent with the B c ( 2 1 S 0 ) + state. These mass measurements are the most precise to date