The B0→K∗0K¯∗0\ {B}^0\to {K}^{\ast 0}{\overline{K}}^{\ast 0} \ and Bs0→K∗0K¯∗0\ {B}_s^0\to {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 B0→K∗0K¯∗0\ {B}^0\to {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 Bs0→K∗0K¯∗0\ {B}_s^0\to {K}^{\ast 0}{\overline{K}}^{\ast 0} \ decay. The ratio of branching fractions of the two decays is measured and used to determine ℬB0→K∗0K¯∗0=8.0±0.9stat±0.4syst×10−7\ \mathrm{\mathcal{B}}\left({B}^0\to {K}^{\ast 0}{\overline{K}}^{\ast 0}\right)=\left(8.0\pm 0.9\left(\mathrm{stat}\right)\pm 0.4\left(\mathrm{syst}\right)\right)\times {10}^{-7} \.
The prompt production of Λc+ baryons is studied in proton-lead collisions collected with the LHCb detector at the LHC. The data sample corresponds to an integrated luminosity of 1.58 nb−1 recorded at ...a nucleon-nucleon centre-of-mass energy of sNN=5.02\ \sqrt{s_{\mathrm{NN}}}=5.02 \ TeV. Measurements of the differential cross-section and the forwardbackward production ratio are reported for Λc+ baryons with transverse momenta in the range 2 < pT < 10 GeV/c and rapidities in the ranges 1.5 < y∗ < 4.0 and −4.5 < y∗ < −2.5 in the nucleon-nucleon centre-of-mass system. The ratio of cross-sections of Λc+ baryons and D0 mesons is also reported. The results are compared with next-to-leading order calculations that use nuclear parton distribution functions.
The production of ϒ(nS) mesons (n = 1, 2, 3) in pPb and Pbp collisions at a centre-of-mass energy per nucleon pair sNN=8.16\ \sqrt{s_{\mathrm{NN}}}=8.16 \ TeV is measured by the LHCb experiment, ...using a data sample corresponding to an integrated luminosity of 31.8 nb−1. The ϒ(nS) mesons are reconstructed through their decays into two opposite-sign muons. The measurements comprise the differential production cross-sections of the ϒ(1S) and ϒ(2S) states, their forward-to-backward ratios and nuclear modification factors. The measurements are performed as a function of the transverse momentum pT and rapidity in the nucleon-nucleon centre-of-mass frame y* of the ϒ(nS) states, in the kinematic range pT < 25 GeV/c and 1.5 < y* < 4.0 (−5.0 < y* < −2.5) for pPb (Pbp) collisions. In addition, production cross-sections for ϒ(3S) are measured integrated over phase space and the production ratios between all three ϒ(nS) states are determined. Suppression for bottomonium in proton-lead collisions is observed, which is particularly visible in the ratios. The results are compared to theoretical models.
The inclusive Ds± production asymmetry is measured in pp collisions collected by the LHCb experiment at centre-of-mass energies of s=7 and 8 TeV. Promptly produced Ds± mesons are used, which decay as ...Ds± → ϕπ±, with ϕ → K+K−. The measurement is performed in bins of transverse momentum, pT, and rapidity, y, covering the range 2.5 < pT< 25.0 GeV/c and 2.0 < y < 4.5. No kinematic dependence is observed. Evidence of nonzero Ds± production asymmetry is found with a significance of 3.3 standard deviations.
Observation of the decay Λ b 0 → ψ(2S)pπ Adeva, B; P Alvarez Cartelle; Amato, S ...
The journal of high energy physics,
08/2018, Letnik:
2018, Številka:
8
Journal Article
Recenzirano
Odprti dostop
The Cabibbo-suppressed decay Λb0 → ψ(2S)pπ− is observed for the first time using a data sample collected by the LHCb experiment in proton-proton collisions corresponding to 1.0, 2.0 and 1.9 fb−1 of ...integrated luminosity at centre-of-mass energies of 7, 8 and 13 TeV, respectively. The ψ(2S) mesons are reconstructed in the μ+μ− final state. The branching fraction with respect to that of the Λb0 → ψ(2S)pK− decay mode is measured to beℬΛb0→ψ2Spπ−ℬΛb0→ψ2SpK−=11.4±1.3±0.2%,where the first uncertainty is statistical and the second is systematic. The ψ(2S)p and ψ(2S)π− mass spectra are investigated and no evidence for exotic resonances is found.
The B¯s0→χc2K+K−\ {\overline{B}}_s^0\to {\chi}_{c2}{K}^{+}{K}^{-} \ decay mode is observed and its branching fraction relative to the corresponding χc1 decay mode, in a ±15 MeV/c2 window around the ϕ ...mass, is found to beℬB¯s0→χc2K+K−ℬB¯s0→χc1K+K−=17.1±3.1±0.4±0.9%,\ \frac{\mathrm{\mathcal{B}}\left({\overline{B}}_s^0\to {\chi}_{c2}{K}^{+}{K}^{-}\right)}{\mathrm{\mathcal{B}}\left({\overline{B}}_s^0\to {\chi}_{c1}{K}^{+}{K}^{-}\right)}=\left(17.1 \pm 3.1\pm 0.4\pm 0.9\right)\%, \where the first uncertainty is statistical, the second systematic and the third due to the knowledge of the branching fractions of radiative χc decays. The decay mode B¯s0→χc1K+K−\ {\overline{B}}_s^0\to {\chi}_{c1}{K}^{+}{K}^{-} \ allows the Bs0 mass to be measured asmBs0=5366.83±0.25±0.27MeV/c2,\ m\left({B}_s^0\right)=5366.83\pm 0.25\pm 0.27\ \mathrm{M}\mathrm{e}\mathrm{V}/{c}^2, \where the first uncertainty is statistical and the second systematic. A combination of this result with other LHCb determinations of the Bs0 mass is made.
A search for the decay BS0→K¯∗0μ+μ− is presented using data sets corresponding to 1.0, 2.0 and 1.6 fb−1 of integrated luminosity collected during pp collisions with the LHCb experiment at ...centre-of-mass energies of 7, 8 and 13 TeV, respectively. An excess is found over the background-only hypothesis with a significance of 3.4 standard deviations. The branching fraction of the BS0→K¯∗0μ+μ− decay is determined to be ℬBs0→K¯∗0μ+μ−=2.9±1.0stat±0.2syst±0.3norm×10−8, where the first and second uncertainties are statistical and systematic, respectively. The third uncertainty is due to limited knowledge of external parameters used to normalise the branching fraction measurement.
A flavour-tagged decay-time-dependent amplitude analysis of Bs0 → (K+π−)(K−π+) decays is presented in the K±π∓ mass range from 750 to 1600MeV/c2. The analysis uses pp collision data collected with ...the LHCb detector at centre-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3.0 fb−1. Several quasi-two-body decay modes are considered, corresponding to K±π∓ combinations with spin 0, 1 and 2, which are dominated by the K0*(800)0 and K0*(1430)0, the K*(892)0 and the K2*(1430)0 resonances, respectively. The longitudinal polarisation fraction for the Bs0→K∗892°K¯∗8920 decay is measured as fL = 0.208 ± 0.032 ± 0.046, where the first uncertainty is statistical and the second is systematic. The first measurement of the mixing-induced CP-violating phase, ϕsdd¯, in b→dd¯s transitions is performed, yielding a value of ϕsdd¯=−0.10±0.13stat±0.14 (syst) rad.
The charmless three-body decays B(s)0 → KS0h+h′ − (where h(′) = π, K) are analysed using a sample of pp collision data recorded by the LHCb experiment, corresponding to an integrated luminosity of 3 ...fb−1. The branching fractions are measured relative to that of the B0 → KS0π+π− decay, and are determined to be:ℬB0→KS0K±π∓ℬB0→KS0K+π−=0.123±0.009stat±0.015syst,ℬB0→KS0K+K−ℬB0→KS0π+π−=0.549±0.018stat±0.033syst,ℬBs0→KS0π+π−ℬB0→KS0π+π−=0.191±0.027stat±0.031syst±0.011fs/fd,ℬBs0→KS0K±π∓ℬB0→KS0π+π−=1.70±0.07stat±0.11syst±0.10fs/fd,ℬBs0→KS0K+K−ℬB0→KS0π+π−∈0.008−0.051at90%confidencelevel,where fs/fd represents the ratio of hadronisation fractions of the Bs0 and B0 mesons.
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