Ratio Of Branching Fractions Research Articles

Angular analysis of {B}^0to {D}^{ast -}{D}_s^{ast +} with {D}_s^{ast +}to {D}_s^{+}gamma decays

The first full angular analysis of the {B}^0to {D}^{ast -}{D}_s^{ast +} decay is performed using 6 fb−1 of pp collision data collected with the LHCb experiment at a centre-of-mass energy of 13 TeV. The {D}_s^{ast +}to {D}_s^{+}gamma and D*− → {overline{D}}^0{pi}^{-} vector meson decays are used with the subsequent {D}_s^{+} → K+K−π+ and {overline{D}}^0 → K+π− decays. All helicity amplitudes and phases are measured, and the longitudinal polarisation fraction is determined to be fL = 0.578 ± 0.010 ± 0.011 with world-best precision, where the first uncertainty is statistical and the second is systematic. The pattern of helicity amplitude magnitudes is found to align with expectations from quark-helicity conservation in B decays. The ratio of branching fractions [ℬ( {B}^0to {D}^{ast -}{D}_s^{ast +} ) × ℬ( {D}_s^{ast +}to {D}_s^{+}gamma )]/ℬ(B0 → D*− {D}_s^{+} ) is measured to be 2.045 ± 0.022 ± 0.071 with world-best precision. In addition, the first observation of the Cabibbo-suppressed Bs → D*− {D}_s^{+} decay is made with a significance of seven standard deviations. The branching fraction ratio ℬ(Bs → D*− {D}_s^{+} )/ℬ(B0 → D*− {D}_s^{+} ) is measured to be 0.049 ± 0.006 ± 0.003 ± 0.002, where the third uncertainty is due to limited knowledge of the ratio of fragmentation fractions.

Possible assignments of highly excited varLambda _c(2860)^+, varLambda _c(2880)^+ and varLambda _c(2940)^+

Possible assignments of highly excited varLambda _c(2860)^+, varLambda _c(2880)^+ and varLambda _c(2940)^+ are explored in a ^3P_0 strong decay model. Decay widths, branching fraction ratios R={varGamma (varSigma _c(2520)pi )over varGamma (varSigma _c(2455)pi )} and the branching fractions of DN channels of theses assignments are computed. D^0p channel is a very important channel to provide information on the inner excitation and structure of these highly excited varLambda _c. In our analysis, varLambda _c(2860)^+ may be a 1D-wave excited varLambda _c with J^P={3over 2}^+, which has dominant DN decay channels with a branching fraction {mathcal {B}}(varLambda _c(2860)^+rightarrow DN)=75% and a branching ratio R={varGamma (varSigma _c(2520)pi )over varGamma (varSigma _c(2455)pi )}=0.12. varLambda _c(2880)^+ is very possibly a 1F-wave excited varLambda _c with J^P=frac{5}{2}^-; In this assignment, the predicted total decay width (varGamma approx 4.49 MeV) is comparable to the measured varGamma =5.6^{+0.8}_{-0.6} MeV, and the predicted R={varGamma (varSigma _c(2520)pi )over varGamma (varSigma _c(2455)pi )}=0.12 is consistent with the measured R=0.225pm 0.062pm 0.025; The DN channels are its dominant strong decay channels with a branching fraction {mathcal {B}}(varLambda _c(2880)^+rightarrow DN)=94%. varLambda _c(2880)^+ seems impossibly a 1D-wave excited varLambda _c with J^P=frac{5}{2}^+ once the presently measured R={varGamma (varSigma _c(2520)pi )over varGamma (varSigma _c(2455)pi )} is confirmed. varLambda _c(2940)^+ may be a 2P-wave excited varLambda ^{1,0}_{c1,1}(frac{3}{2}^-,2P). In this case, varLambda _c(2940)^+ has a total decay width varGamma =17.56 MeV, a branching ratio R={varGamma (varSigma _c(2520)pi )over varGamma (varSigma _c(2455)pi )}=0.89 and the DN decay channels with a branching fraction {mathcal {B}}(varLambda _c(2940)^+rightarrow DN)=43%. In order to understand the inner excitation and structure of these highly excited varLambda _c, measurements of those predicted quantities are required in the future.

Test of Lepton-Flavor Universality in B→K^{*}ℓ^{+}ℓ^{-} Decays at Belle.

We present a measurement of R_{K^{*}}, the branching fraction ratio B(B→K^{*}μ^{+}μ^{-})/B(B→K^{*}e^{+}e^{-}), for both charged and neutral B mesons. The ratio for the charged case R_{K^{*+}} is the first measurement ever performed. In addition, we report absolute branching fractions for the individual modes in bins of the squared dilepton invariant mass q^{2}. The analysis is based on a data sample of 711 fb^{-1}, containing 772×10^{6} BB[over ¯] events, recorded at the ϒ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e^{+}e^{-} collider. The obtained results are consistent with standard model expectations.

Measurements of the branching fractions ofΛc+→pηandΛc+→pπ0decays at Belle

We report measurements of the branching fractions of singly Cabibbo-suppressed decays $\Lambda_c^+ \to p \eta$ and $\Lambda_c^+ \to p \pi^0$ using the full Belle data sample corresponding to an integrated luminosity of 980.6 $\rm fb^{-1}$. The data were collected by the Belle detector at the KEKB $e^{+}$$e^{-}$ asymmetric-energy collider. A clear $\Lambda_c^+$ signal is seen in the invariant mass distribution of $p \eta$. The signal yield of the $\Lambda_c^+ \to p \eta$ process is $7734 \pm 263$; from this, we measure the ratio of branching fractions ${\cal B}(\Lambda_c^+ \to p \eta)/{\cal B}(\Lambda_c^+ \to p K^- \pi^+) = (2.258 \pm 0. 077(\rm stat. ) \pm 0.136(\rm syst. ))\times 10^{-2}$, from which we infer the branching fraction ${\cal B}(\Lambda_c^+ \to p \eta) = (1.42 \pm 0.05(\rm stat.) \pm 0.11(\rm syst.)) \times 10^{-3}$. In addition, no significant signal for $\Lambda_c^+ \to p \pi^0$ is found so an upper limit on the branching fraction of ${\cal B}(\Lambda_c^+ \to p \pi^0)<8.0 \times 10^{-5}$ at 90\% credibility level is set, more than three times better than the best current upper limit.

Observation of the [formula omitted] decay

The Λb0→Λc+K+K−π− decay is observed for the first time using a data sample of proton-proton collisions at centre-of-mass energies of s=7 and 8TeV collected by the LHCb detector, corresponding to an integrated luminosity of 3fb−1. The ratio of branching fractions between the Λb0→Λc+K+K−π− and the Λb0→Λc+Ds− decays is measured to beB(Λb0→Λc+K+K−π−)B(Λb0→Λc+Ds−)=(9.26±0.29±0.46±0.26)×10−2, where the first uncertainty is statistical, the second systematic and the third is due to the knowledge of the Ds−→K+K−π− branching fraction. No structure on the invariant mass distribution of the Λc+K+ system is found, consistent with no open-charm pentaquark signature.

Study of {mathrm{B}}_{mathrm{s}}^0 \u2192 J/\u03c8\u03c0+\u03c0\u2212K+K\u2212 decays

The decays {mathrm{B}}_{mathrm{s}}^0 → J/ψπ+π−K+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 at centre-of-mass energies of 7, 8 and 13 TeV. The decays {mathrm{B}}_{mathrm{s}}^0 → mathrm{J}/{uppsi mathrm{K}}^{ast 0}{overline{mathrm{K}}}^{ast 0} and {mathrm{B}}_{mathrm{s}}^0 → χc1(3872)K+K−, where the K+K−pair does not originate from a ϕ meson, are observed for the first time. Precise measurements of the ratios of branching fractions between intermediate χc1(3872)ϕ, mathrm{J}/{uppsi mathrm{K}}^{ast 0}{overline{mathrm{K}}}^{ast 0} , ψ(2S)ϕ and χc1(3872)K+K− states are reported. A structure, denoted as X(4740), is observed in the J/ψϕ mass spectrum and, assuming a Breit-Wigner parameterisation, its mass and width are determined to bemX4740=4741±6±6MeV/c2,ΓX4740=53±15±11MeV,\\documentclass[12pt]{minimal}\t\t\t\t\\usepackage{amsmath}\t\t\t\t\\usepackage{wasysym}\t\t\t\t\\usepackage{amsfonts}\t\t\t\t\\usepackage{amssymb}\t\t\t\t\\usepackage{amsbsy}\t\t\t\t\\usepackage{mathrsfs}\t\t\t\t\\usepackage{upgreek}\t\t\t\t\\setlength{\\oddsidemargin}{-69pt}\t\t\t\t\\begin{document}$$ {\\displaystyle \\begin{array}{c}{m}_{\\mathrm{X}(4740)}=4741\\pm 6\\pm 6\\kern0.5em \\mathrm{MeV}/{c}^2,\\\\ {}{\\Gamma}_{\\mathrm{X}(4740)}=53\\pm 15\\pm 11\\kern0.5em \\mathrm{MeV},\\end{array}} $$\\end{document}where the first uncertainty is statistical and the second is systematic. In addition, the most precise single measurement of the mass of the {mathrm{B}}_{mathrm{s}}^0 meson is performed and gives a value of {m}_{{mathrm{B}}_{mathrm{s}}^0}=5366.98pm 0.07pm 0.13kern0.5em mathrm{MeV}/{c}^2.

An Explanation for the Violation of Lepton Universality in Beauty-Quark Decays: The Binary Isotope Mixture of Beauty-Quarks

This paper purposes an explanation for the recent evidence for the violation of lepton universality in beauty-quark decays at CERN’s Large Hadron Collider. A beauty meson (B+) transforms into a strange meson (K+) with the emission of either electron-positron (e+e-) or muon-antimuon (μ+μ-). The ratio (RK) of branching fractions for B+ → K+μ+μ- and B+→ K+e+e- decays is measured to be RK = 0.846 instead of 1 in the violation of lepton universality in the Standard Model. This paper proposes that the violation is derived from the binary isotope mixture of two beauty-quarks, b7 (4979 MeV mass) and b8 (143,258 MeV mass) whose masses are calculated from the periodic table of elementary particles. b7 is the observable B, while b8 is the hidden B to preserve the generation number symmetry between the three lepton family generations and the three quark family generations in the Standard Model. The preservation of the generation number symmetry forbids b8 to decay into K+μ+μ-. In the transition state involving the virtual particles (γ, W± and Z°) before the decay, b7 and b8 emerge to form the binary isotope mixture from B. The rates of emergence as the rates of diffuse in Graham’s law of diffusion are proportional to inverse square root of mass. The rate ratio between b8/b7 is (4979/143,258)1/2 = 0.1864. Since b7 decays into K+, e+e-, and μ+μ-, while b8 decays into K+, e+e-, and forbidden μ+μ-, the calculated ratio (RK) of branching fractions for B+→ K+μ+μ- and B+→ K+e+e- is 0.5/(0.1864 × 0.5+ 0.5) = 0.843 in excellent agreement with the observed 0.846. The agreement between the calculated RK and the observed RK confirms the validity of the periodic table of elementary particles which provides the answers for the dominance of matter over antimatter, dark-matter, and the mass hierarchy of elementary particles.

Observation of the $$\Lambda _{b}^{0} \to J{\text{/}}\psi \Lambda \phi $$ Decay in the CMS Experiment

This study is devoted to the observation of the $$\Lambda _{b}^{0} \to J{\text{/}}\psi \Lambda \phi $$ decay using proton-proton (pp) collision data collected at $$\sqrt s = 13$$ TeV by the CMS experiment at the Large Hadron Collider in 2018, which corresponds to the integrated luminosity of 60fb–1. The branching fraction ratio $$\mathcal{B}(\Lambda _{b}^{0} \to J{\text{/}}\psi \Lambda \phi ){\text{/}}\mathcal{B}(\Lambda _{b}^{0} \to \psi (2S)\Lambda )$$ = $$(8.26 \pm 0.90({\text{stat}}) \pm 0.68({\text{syst}}{\text{.}}) \pm 0.11(\mathcal{B})) \times {{10}^{{ - 2}}}$$ was measured; the first uncertainty is statistical, the second is systematic, and the third one reflects the uncertainties in the world-average branching fractions of ϕ and $$\psi (2S)$$ decays to reconstructed final states.

R(J/ψ) and B_{c}^{-}→J/ψℓ^{-}ν[over ¯]_{l} Lepton Flavor Universality Violating Observables from Lattice QCD.

We use our lattice QCD computation of the B_{c}→J/ψ form factors to determine the differential decay rate for the semitauonic decay channel and construct the ratio of branching fractions R(J/ψ)=B(B_{c}^{-}→J/ψτ^{-}ν[over ¯]_{τ})/B(B_{c}^{-}→J/ψμ^{-}ν[over ¯]_{μ}). We find R(J/ψ)=0.2582(38) and give an error budget. We also extend the relevant angular observables, which were recently suggested for the study of lepton flavor universality violating effects in B→D^{*}ℓν, to B_{c}→J/ψℓν and make predictions for their values under different new physics scenarios.

Theoretical interpretation of Ξc(2970)

The open charm strong decay widths and certain ratio of branching fractions of a charmed strange baryon ${\mathrm{\ensuremath{\Xi}}}_{c}(2970)$ are calculated in a $^{3}{P}_{0}$ model. The results are compatible with the latest experimental data. The theoretical ratio of decay branching fractions $R=\mathcal{B}[{\mathrm{\ensuremath{\Xi}}}_{c}(2970{)}^{+}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Xi}}}_{c}(2645{)}^{0}{\ensuremath{\pi}}^{+}]/\mathcal{B}[{\mathrm{\ensuremath{\Xi}}}_{c}(2970{)}^{+}\ensuremath{\rightarrow}\phantom{\rule{0ex}{0ex}}{\mathrm{\ensuremath{\Xi}}}_{c}^{\ensuremath{'}0}{\ensuremath{\pi}}^{+}]\ensuremath{\approx}1.0$. The spin parity ${J}^{P}=1/{2}^{+}$ and $3/{2}^{+}$ for different assignments are analyzed. From the results of our calculation, ${\mathrm{\ensuremath{\Xi}}}_{c}(2970)$ can be interpreted as a $2S$-wave state with ${J}^{P}({s}_{l})=1/{2}^{+}(0)$. The distinctions between the $2S$-wave ${n}_{\ensuremath{\rho}}$- and ${n}_{\ensuremath{\lambda}}$-excitation states and between states with ${s}_{l}=0$ and ${s}_{l}=1$ and between states with total spin $1/2$ and $3/2({s}_{l}=1)$ are also discussed.

Observation of the Doubly Cabibbo-Suppressed Decay D^{+}→K^{+}π^{+}π^{-}π^{0} and Evidence for D^{+}→K^{+}ω.

Using 2.93 fb^{-1} of e^{+}e^{-} collision data collected at a center-of-mass energy of 3.773GeV with the BESIII detector, the first observation of the doubly Cabibbo-suppressed decay D^{+}→K^{+}π^{+}π^{-}π^{0} is reported. After removing decays that contain narrow intermediate resonances, including D^{+}→K^{+}η, D^{+}→K^{+}ω, and D^{+}→K^{+}ϕ, the branching fraction of the decay D^{+}→K^{+}π^{+}π^{-}π^{0} is measured to be (1.13±0.08_{stat}±0.03_{syst})×10^{-3}. The ratio of branching fractions of D^{+}→K^{+}π^{+}π^{-}π^{0} over D^{+}→K^{-}π^{+}π^{+}π^{0} is found to be (1.81±0.15)%, which corresponds to (6.28±0.52)tan^{4}θ_{C}, where θ_{C} is the Cabibbo mixing angle. This ratio is significantly larger than the corresponding ratios for other doubly Cabibbo-suppressed decays. The asymmetry of the branching fractions of charge-conjugated decays D^{±}→K^{±}π^{±}π^{∓}π^{0} is also determined, and no evidence for CP violation is found. In addition, the first evidence for the D^{+}→K^{+}ω decay, with a statistical significance of 3.3σ, is presented and the branching fraction is measured to be B(D^{+}→K^{+}ω)=(5.7_{-2.1}^{+2.5}_{stat}±0.2_{syst})×10^{-5}.

Probing new physics in semileptonic Σb and Ωb decays

Recently, several hints of lepton non-universality have been observed in the semileptonic B meson decays in terms of both in the neutral current ($b\to s l \bar{l}$) and charged current ($b\to c l \bar{\nu_{l}}$) transitions. Motivated by these inspiring results, we perform the analysis of the baryon decays ${\Sigma_b}\to \Sigma_c l \bar{\nu_{l}}$ and $\Omega_b\to \Omega_c l \bar{\nu_{l}} (l=e,\mu,\tau)$ which are mediated by $ b \to c l \bar{\nu_{l}}$ transitions at the quark level, to scrutinize the nature of new physics (NP) in the model independent method. We first use the experimental measurements of $\mathcal{B}( B\to D^{(*)} l\bar{\nu_{l}})$, ${\rm R}_{D^{(*)}}$ and ${\rm R}_{J/\psi}$ to constrain the NP coupling parameters in a variety of scenarios. Using the constrained NP coupling parameters, we report numerical results on various observables related to the processes ${\Sigma_b}\to \Sigma_c l \bar{\nu_{l}}$ and $\Omega_b\to \Omega_c l \bar{\nu_{l}}$, such as the branching ratios, the ratio of branching fractions, the lepton side forward-backward asymmetries, the hadron and lepton longitudinal polarization asymmetries and the convexity parameter. We also provide the $q^2$ dependency of these observables and we hope that the corresponding numerical results in this work will be testified by future experiments.

Study of the \u03c82(3823) and \u03c7c1(3872) states in B+\u2192 (J/\u03c8\u03c0+\u03c0\u2212)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+→ψ23823K+×Bψ23823→J/ψπ+π−BB+→χc13872K+×Bχc13872→J/ψπ+π−=3.56±0.67±0.11×10−2,BB+→ψ23823K+×Bψ23823→J/ψπ+π−BB+→ψ2SK+×Bψ2S→J/ψπ+π−=1.31±0.25±0.04×10−3,BB+→χc13872K+×Bχc13872→J/ψπ+π−BB+→ψ2SK+×Bψ2S→J/ψπ+π−=3.69±0.07±0.06×10−2,\\documentclass[12pt]{minimal}\t\t\t\t\\usepackage{amsmath}\t\t\t\t\\usepackage{wasysym}\t\t\t\t\\usepackage{amsfonts}\t\t\t\t\\usepackage{amssymb}\t\t\t\t\\usepackage{amsbsy}\t\t\t\t\\usepackage{mathrsfs}\t\t\t\t\\usepackage{upgreek}\t\t\t\t\\setlength{\\oddsidemargin}{-69pt}\t\t\t\t\\begin{document}$$ {\\displaystyle \\begin{array}{c}\\frac{{\\mathcal{B}}_{{\\mathrm{B}}^{+}\\to {\\uppsi}_2(3823){\\mathrm{K}}^{+}}\\times {\\mathcal{B}}_{\\uppsi_2(3823)\\to \\mathrm{J}/{\\uppsi \\uppi}^{+}{\\uppi}^{-}}}{{\\mathcal{B}}_{{\\mathrm{B}}^{+}\\to {\\upchi}_{\\mathrm{c}1}(3872){\\mathrm{K}}^{+}}\\times {\\mathcal{B}}_{\\upchi_{\\mathrm{c}1}(3872)\\to \\mathrm{J}/{\\uppsi \\uppi}^{+}{\\uppi}^{-}}}=\\left(3.56\\pm 0.67\\pm 0.11\\right)\\times {10}^{-2},\\\\ {}\\frac{{\\mathcal{B}}_{{\\mathrm{B}}^{+}\\to {\\uppsi}_2(3823){\\mathrm{K}}^{+}}\\times {\\mathcal{B}}_{\\uppsi_2(3823)\\to \\mathrm{J}/{\\uppsi \\uppi}^{+}{\\uppi}^{-}}}{{\\mathcal{B}}_{{\\mathrm{B}}^{+}\\to \\uppsi \\left(2\\mathrm{S}\\right){\\mathrm{K}}^{+}}\\times {\\mathcal{B}}_{\\uppsi \\left(2\\mathrm{S}\\right)\\to \\mathrm{J}/{\\uppsi \\uppi}^{+}{\\uppi}^{-}}}=\\left(1.31\\pm 0.25\\pm 0.04\\right)\\times {10}^{-3},\\\\ {}\\frac{{\\mathcal{B}}_{\\mathrm{B}+\\to {\\upchi}_{\\mathrm{c}1}(3872){\\mathrm{K}}^{+}}\\times {\\mathcal{B}}_{\\upchi_{\\mathrm{c}1}(3872)\\to \\mathrm{J}/{\\uppsi \\uppi}^{+}{\\uppi}^{-}}}{{\\mathcal{B}}_{{\\mathrm{B}}^{+}\\to \\uppsi \\left(2\\mathrm{S}\\right){\\mathrm{K}}^{+}}\\times {\\mathcal{B}}_{\\uppsi \\left(2\\mathrm{S}\\right)\\to \\mathrm{J}/{\\uppsi \\uppi}^{+}{\\uppi}^{-}}}=\\left(3.69\\pm 0.07\\pm 0.06\\right)\\times {10}^{-2},\\end{array}} $$\\end{document}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 bemχc13872−mψ23823=47.50±0.53±0.13MeV/c2,mψ23823−mψ22S=137.98±0.53±0.14MeV/c2,mχc13872−mψ22S=185.49±0.06±0.03MeV/c2,\\documentclass[12pt]{minimal}\t\t\t\t\\usepackage{amsmath}\t\t\t\t\\usepackage{wasysym}\t\t\t\t\\usepackage{amsfonts}\t\t\t\t\\usepackage{amssymb}\t\t\t\t\\usepackage{amsbsy}\t\t\t\t\\usepackage{mathrsfs}\t\t\t\t\\usepackage{upgreek}\t\t\t\t\\setlength{\\oddsidemargin}{-69pt}\t\t\t\t\\begin{document}$$ {\\displaystyle \\begin{array}{c}{m}_{\\upchi_{\\mathrm{c}1}(3872)}-{m}_{\\uppsi_2(3823)}=47.50\\pm 0.53\\pm 0.13\\;\\mathrm{MeV}/{c}^2,\\\\ {}{m}_{\\uppsi_2(3823)}-{m}_{\\uppsi_2\\left(2\\mathrm{S}\\right)}=137.98\\pm 0.53\\pm 0.14\\;\\mathrm{MeV}/{c}^2,\\\\ {}{m}_{\\upchi_{\\mathrm{c}1}(3872)}-{m}_{\\uppsi_2\\left(2\\mathrm{S}\\right)}=185.49\\pm 0.06\\pm 0.03\\;\\mathrm{MeV}/{c}^2,\\end{array}} $$\\end{document}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 beΓχc13872BW=0.96−0.18+0.19±0.21MeV\\documentclass[12pt]{minimal}\t\t\t\t\\usepackage{amsmath}\t\t\t\t\\usepackage{wasysym}\t\t\t\t\\usepackage{amsfonts}\t\t\t\t\\usepackage{amssymb}\t\t\t\t\\usepackage{amsbsy}\t\t\t\t\\usepackage{mathrsfs}\t\t\t\t\\usepackage{upgreek}\t\t\t\t\\setlength{\\oddsidemargin}{-69pt}\t\t\t\t\\begin{document}$$ {\\Gamma}_{\\upchi_{\\mathrm{c}1}(3872)}^{\\mathrm{BW}}={0.96}_{-0.18}^{+0.19}\\pm 0.21\\;\\mathrm{MeV} $$\\end{document}which is inconsistent with zero by 5.5 standard deviations.

Test of lepton universality with {Lambda}_b^0to {pK}^{-}{mathrm{ell}}^{+}{mathrm{ell}}^{-} decays

The ratio of branching fractions of the decays {Lambda}_b^0 → pK−e+e− and {Lambda}_b^0 → pK−μ+μ−, {R}_{pK}^{-1} , is measured for the first time using proton-proton collision data corresponding to an integrated luminosity of 4.7 fb−1 recorded with the LHCb experiment at center-of-mass energies of 7, 8 and 13 TeV. In the dilepton mass-squared range 0.1 < q2< 6.0 GeV2/c4 and the pK− mass range m(pK−) < 2600 MeV/c2, the ratio of branching fractions is measured to be {R}_{pK}^{-1}={1.17}_{-0.16}^{+0.18}pm 0.07 , where the first uncertainty is statistical and the second systematic. This is the first test of lepton universality with b baryons and the first observation of the decay {Lambda}_b^0 → pK−e+e−.

Bs→Dsℓν form factors for the full q2 range from lattice QCD with nonperturbatively normalized currents

We present a lattice QCD determination of the $B_s \to D_s \ell\nu$ scalar and vector form factors over the full physical range of momentum transfer. The result is derived from correlation functions computed using the Highly Improved Staggered Quark (HISQ) formalism, on the second generation MILC gluon ensembles accounting for up, down, strange and charm contributions from the sea. We calculate correlation functions for three lattice spacing values and an array of unphysically light $b$-quark masses, and extrapolate to the physical value. Using the HISQ formalism for all quarks means that the lattice current coupling to the $W$ can be renormalized non-perturbatively, giving a result free from perturbative matching errors for the first time. Our results are in agreement with, and more accurate than, previous determinations of these form factors. From the form factors we also determine the ratio of branching fractions that is sensitive to violation of lepton universality: $R(D_s) = \mathcal{B}(B_s\to D_s \tau \nu_{\tau})/\mathcal{B}(B_s\to D_s \ell \nu_{l})$, where $\ell$ is an electron or a muon. We find $R(D_s) = 0.2987(46)$, which is also more accurate than previous lattice QCD results. Combined with a future measurement of $R(D_s)$, this could supply a new test of the Standard Model. We also compare the dependence on heavy quark mass of our form factors to expectations from Heavy Quark Effective Theory.

Hidden-charm strong decays of the Zc states

Inspired by BESIII's measurement of the decay $Z_c(3900)^{\pm}\rightarrow \rho^{\pm}\eta_c$, we calculate the branching fraction ratio between the $\rho\eta_c$ and $\pi J/\psi$ decay modes for the charged states $Z_c(3900)$, $Z_c(4020)$ and $Z_c(4430)$ using a quark interchange model. Our results show that (i) the ratio $R_{Z_c(3900)}=\frac{\mathcal{B}(Z_c(3900)^{\pm}\rightarrow \rho^{\pm}\eta_c)}{\mathcal{B}(Z_c(3900)^{\pm}\rightarrow \pi^{\pm}J/\psi)}$ is 1.3 and 1.6 in the molecular and tetraquark scenarios respectively, which is roughly consistent with the experimental data $R^{\mathrm{exp}}=2.2\pm0.9$. (ii) The ratios $\frac{\Gamma[Z_c(3900)\rightarrow \rho\eta_c]}{\Gamma[Z_c(4020)\rightarrow \rho\eta_c]}$ and $\frac{\Gamma[Z_c(3900)\rightarrow \pi J/\psi]}{\Gamma[Z_c(4020)\rightarrow \pi J/\psi]}$ are about 12.5 and 24.2, respectively in the molecular scenario. In contrast, these ratios are about 1.2 in the tetraquark scenario. The non-observation of the $Z_c(4020)$ signal in the $\pi J/\psi$ decay mode strongly indicates that $Z_c(3900)$ and $Z_c(4020)$ are molecule-like signals which arise from the $D^{(*)}{\bar D}^{(*)}$ hadronic interactions.

Probing new physics in semileptonic Xi _{b}rightarrow Lambda (Xi _{c})tau ^{-}bar{nu }_{tau } decays

Recently, several observed anomalies in semileptonic B meson decays have implied hints of lepton flavor universal violation. Motivated by these inspiring results, we study the baryon decays Xi _{b}rightarrow Lambda (Xi _{c})tau ^{-}bar{nu }_{tau } which are mediated by brightarrow u(c)tau ^{-}bar{nu }_{tau } transitions at quark level in the Standard Model and different New Physics scenarios. In the framework of the extended Standard Model on assuming a general effective theory, we constrain the Wilson coefficients of the NP operators using the experimental measurement results for the Br(B_{c}^+rightarrow tau ^+ nu _{tau }), R^{l}_{pi }, R_{D^{(*)}}, R_{J/psi } and F_{L}^{D^{*}} anomalies and investigate their New Physics effects on several observables relative to the Xi _{b}rightarrow Lambda (Xi _{c})tau ^{-}bar{nu }_{tau } decays. We mention the differential branching fraction {text {d}}Br/{text {d}}q^2, the ratio of branching fractions R(q^2), the lepton-side forward–backward asymmetry A_{FB}(q^2), the longitudinal polarization P_{L}^{Lambda (Xi _{c})}(q^2) of the daughter baryons Lambda (Xi _{c}) and P_{L}^{tau }(q^2) of the tau lepton, and the convexity parameter C_{F}(q^2).

Extraction of form Factors from a Four-Dimensional Angular Analysis of B[over ¯]→D^{*}ℓ^{-}ν[over ¯]_{ℓ}.

An angular analysis of the decay B[over ¯]→D^{*}ℓ^{-}ν[over ¯]_{ℓ}, ℓ∈{e,μ}, is reported using the full e^{+}e^{-} collision data set collected by the BABAR experiment at the ϒ(4S) resonance. One B meson from the ϒ(4S)→BB[over ¯] decay is fully reconstructed in a hadronic decay mode, which constrains the kinematics and provides a determination of the neutrino momentum vector. The kinematics of the semileptonic decay is described by the dilepton mass squared, q^{2}, and three angles. The first unbinned fit to the full four-dimensional decay rate in the standard model is performed in the so-called Boyd-Grinstein-Lebed approach, which employs a generic q^{2} parametrization of the underlying form factors based on crossing symmetry, analyticity, and QCD dispersion relations for the amplitudes. A fit using the more model-dependent Caprini-Lellouch-Neubert (CLN) approach is performed as well. Our form factor shapes show deviations from previous fits based on the CLN parametrization. The latest form factors also provide an updated prediction for the branching fraction ratio R(D^{*})≡B(B[over ¯]→D^{*}τ^{-}ν[over ¯]_{τ})/B(B[over ¯]→D^{*}ℓ^{-}ν[over ¯]_{ℓ})=0.253±0.005. Finally, using the well-measured branching fraction for the B[over ¯]→D^{*}ℓ^{-}ν[over ¯]_{ℓ} decay, a value of |V_{cb}|=(38.36±0.90)×10^{-3} is obtained that is consistent with the current world average for exclusive B[over ¯]→D^{(*)}ℓ^{-}ν[over ¯]_{ℓ} decays and remains in tension with the determination from inclusive semileptonic B decays to final states with charm.

Amplitude analysis of the {B}_{(s)}^0to {K}^{ast 0}{overline{K}}^{ast 0} decays and measurement of the branching fraction of the {B}^0to {K}^{ast 0}{overline{K}}^{ast 0} decay

The {B}^0to {K}^{ast 0}{overline{K}}^{ast 0} and {B}_s^0to {K}^{ast 0}{overline{K}}^{ast 0} decays are studied using proton-proton collision data corresponding to an integrated luminosity of 3 fb−1. An untagged and timeintegrated amplitude analysis of B(s)0 → (K+π−)(K−π+) decays in two-body invariant mass regions of 150 MeV/c2 around the K∗0 mass is performed. A stronger longitudinal polarisation fraction in the {B}^0to {K}^{ast 0}{overline{K}}^{ast 0} decay, fL = 0.724 ± 0.051 (stat) ± 0.016 (syst), is observed as compared to fL = 0.240 ± 0.031 (stat) ± 0.025 (syst) in the {B}_s^0to {K}^{ast 0}{overline{K}}^{ast 0} decay. The ratio of branching fractions of the two decays is measured and used to determine mathrm{mathcal{B}}left({B}^0to {K}^{ast 0}{overline{K}}^{ast 0}right)=left(8.0pm 0.9left(mathrm{stat}right)pm 0.4left(mathrm{syst}right)right)times {10}^{-7} .

Search for Lepton-Universality Violation in B^{+}→K^{+}ℓ^{+}ℓ^{-} Decays.

A measurement of the ratio of branching fractions of the decays B^{+}→K^{+}μ^{+}μ^{-} and B^{+}→K^{+}e^{+}e^{-} is presented. The proton-proton collision data used correspond to an integrated luminosity of 5.0 fb^{-1} recorded with the LHCb experiment at center-of-mass energies of 7, 8, and 13TeV. For the dilepton mass-squared range 1.1<q^{2}<6.0 GeV^{2}/c^{4} the ratio of branching fractions is measured to be R_{K}=0.846_{-0.054}^{+0.060}_{-0.014}^{+0.016}, where the first uncertainty is statistical and the second systematic. This is the most precise measurement of R_{K} to date and is compatible with the standard model at the level of 2.5 standard deviations.