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Register a new userObservation of new excited $B_s^0$ states
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A structure is observed in the $B^+K^-$ mass spectrum in 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 structure is interpreted as the result of overlapping excited $B_s^0$ states. With high significance, a two-peak hypothesis provides a better description of the data than a single resonance. Under this hypothesis the masses and widths of the two states, assuming they decay directly to $B^+K^-$, are determined to be $m_1 = 6063.5 pm 1.2 text{ (stat)} pm 0.8text{ (syst) MeV},$ $Gamma_1 = 26 pm 4 text{ (stat)} pm 4text{ (syst) MeV},$ $m_2 = 6114 pm 3 text{ (stat)} pm 5text{ (syst) MeV},$ $Gamma_2 = 66 pm 18 text{ (stat)} pm 21text{ (syst) MeV}.$ Alternative values assuming a decay through $B^{*+}K^-$, with a missing photon from the $B^{*+} rightarrow B^+gamma$ decay, which are shifted by approximately 45 MeV are also determined. The possibility of a single state decaying in both channels is also considered. The ratio of the total production cross-section times branching fraction of the new states relative to the previously observed $B_{s2}^{*0}$ state is determined to be $0.87 pm 0.15 text{ (stat)} pm 0.19 text{ (syst)}$.
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We report the first observation of a baryonic $B_s^0$ decay, $B_s^0 to p kern 0.1emoverline{kern -0.1emLambda} K^-$, using proton-proton collision data recorded by the LHCb experiment at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of $3.0,mathrm{fb}^{-1}$. The branching fraction is measured to be $ mathcal{B}(B_s^0 to p kern 0.1emoverline{kern -0.1emLambda} K^-) + mathcal{B}(B_s^0 to bar{p} Lambda K^+) = left[5.46 pm 0.61 pm 0.57 pm 0.50 (mathcal{B}) pm 0.32 (f_s/f_d)right]times 10^{-6}, $ where the first uncertainty is statistical and the second systematic, the third uncertainty accounts for the experimental uncertainty on the branching fraction of the $B^0 to p kern 0.1emoverline{kern -0.1emLambda} pi^-$ decay used for normalization, and the fourth uncertainty relates to the knowledge of the ratio of $b$-quark hadronization probabilities $f_s/f_d$.
Properties of the orbitally excited (L=1) $B_s$ states are studied using 1.0 fb$^{-1}$ of pp collisions at $sqrt{s} =7$ TeV collected with the LHCb detector. The first observation of the $B_{s2}^*(5840)^0$ meson decaying to $B^{*+} K^-$ is reported, and the corresponding branching fraction measured relative to the $B^+ K^-$ decay mode. The $B_{s1}(5830)^0 to B^{*+} K^-$ decay is observed as well. The width of the $B_{s2}^*(5840)^0$ state is measured for the first time and the masses of the two states are determined with the highest precision to date. The observation of the $B_{s2}^*(5840)^0 to B^{*+} K^-$ decay favours the spin-parity assignment $J^P = 2^+$ for the $B_{s2}^*(5840)^0$ meson. In addition, the most precise measurement of the mass difference $m(B^{*+})-m(B^+) = 45.01 pm 0.30 (stat) pm 0.23 (syst)$ MeV/$c^2$ is obtained.
The first observation of the decay $B_s^0 rightarrow phi bar{K}^{*0}$ is reported. The analysis is based on a data sample corresponding to an integrated luminosity of 1.0 fb$^{-1}$ of $pp$ collisions at $sqrt{s} = 7 TeV$, collected with the LHCb detector. A yield of $30 pm 6$ $B_s^0 rightarrow (K^+K^-)(K^-pi^+)$ decays is found in the mass windows $1012.5 < M(K^+K^-) < 1026.5 MeV/c^2$ and $746 < M(K^-pi^+)< 1046 MeV/c^2$. The signal yield is found to be dominated by $B_s^0 rightarrow phi bar{K}^{*0}$ decays, and the corresponding branching fraction is measured to be ${cal B}(B_s^0 rightarrow phi bar{K}^{*0}) = (1.10 pm 0.24 (stat) pm 0.14 (syst) pm 0.08 (f_d/f_s)) times 10^{-6}$, where the uncertainties are statistical, systematic and from the ratio of fragmentation fractions $f_d/f_s$ which accounts for the different production rate of $B^0$ and $B_s^0$ mesons. The significance of $B_s^0 rightarrow phi bar{K}^{*0}$ signal is 6.1 standard deviations. The fraction of longitudinal polarization in $B_s^0 rightarrow phi bar{K}^{*0}$ decays is found to be $f_0 = 0.51 pm 0.15 (stat) pm 0.07 (syst)$.
The first observation of the $B_s^0 to overline{D}^0 K^+ K^-$ decay is reported, together with the most precise branching fraction measurement of the mode $B^0 to overline{D}^0 K^+ K^-$. The results are obtained from an analysis of $pp$ collision data corresponding to an integrated luminosity of $3.0~textrm{fb}^{-1}$. The data were collected with the LHCb detector at centre-of-mass energies of $7$ and $8$ TeV. The branching fraction of the $B^0 to overline{D}^0 K^+ K^-$ decay is measured relative to that of the decay $B^0 to overline{D}^0 pi^+ pi^-$ to be $$frac{mathcal{B}(B^0 to overline{D}^0 K^+ K^-)}{mathcal{B}(B^0 to overline{D}^0 pi^+ pi^-)} = (6.9 pm 0.4 pm 0.3)%,$$ where the first uncertainty is statistical and the second is systematic. The measured branching fraction of the $B_s^0 to overline{D}^0 K^+ K^-$ decay mode relative to that of the corresponding $B^0$ decay is $$frac{mathcal{B}(B_s^0 to overline{D}^0 K^+ K^-)}{mathcal{B}(B^0 to overline{D}^0 K^+ K^-)} = (93.0 pm 8.9 pm 6.9)%.$$ Using the known branching fraction of ${B^0 to overline{D}^0 pi^+ pi^-}$, the values of ${{mathcal B}(B^0 to overline{D}^0 K^+ K^- )=(6.1 pm 0.4 pm 0.3 pm 0.3) times 10^{-5}}$, and ${{cal B}(B_s^0 to overline{D}^0 K^+ K^-)=}$ $(5.7 pm 0.5 pm 0.4 pm 0.5) times 10^{-5}$ are obtained, where the third uncertainties arise from the branching fraction of the decay modes ${B^0 to overline{D}^0 pi^+ pi^-}$ and $B^0 to overline{D}^0 K^+ K^-$, respectively.
We report four narrow peaks in the $Xi_b^0K^-$ 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 begin{align*} m(Omega_b(6316)^-) &= 6315.64pm0.31pm0.07pm0.50 {rm MeV}, m(Omega_b(6330)^-) &= 6330.30pm0.28pm0.07pm0.50 {rm MeV}, m(Omega_b(6340)^-) &= 6339.71pm0.26pm0.05pm0.50 {rm MeV}, m(Omega_b(6350)^-) &= 6349.88pm0.35pm0.05pm0.50 {rm MeV}, end{align*}where the uncertainties are statistical, systematic and the last is due to the knowledge of the $Xi_b^0$ 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 ${Gamma(Omega_b(6316)^-)<2.8}$ MeV, ${Gamma(Omega_b(6330)^-)<3.1}$ MeV and ${Gamma(Omega_b(6340)^-)<1.5}$ MeV. The natural width of the $Omega_b(6350)^-$ peak is $1.4^{+1.0}_{-0.8}pm0.1$ MeV, which is 2.5$sigma$ from zero and corresponds to an upper limit of 2.8 MeV. The peaks have local significances ranging from 3.6$sigma$ to 7.2$sigma$. After accounting for the look-elsewhere effect, the significances of the $Omega_b(6316)^-$ and $Omega_b(6330)^-$ peaks are reduced to 2.1$sigma$ and 2.6$sigma$ respectively, while the two higher mass peaks exceed 5$sigma$. The observed peaks are consistent with expectations for excited $Omega_b^-$ resonances.
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