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 first measurements of the forward-backward asymmetry of the dimuon pair (A_{FB}), the triple-product asymmetry (A_{2ϕ}), and the charge-parity-conjugation asymmetry (A_{CP}), in ...D^{0}→π^{+}π^{-}μ^{+}μ^{-} and D^{0}→K^{+}K^{-}μ^{+}μ^{-} decays are reported. They are performed using data from proton-proton collisions collected with the LHCb experiment from 2011 to 2016, corresponding to a total integrated luminosity of 5 fb^{-1}. The asymmetries are measured to be A_{FB}(D^{0}→π^{+}π^{-}μ^{+}μ^{-})=(3.3±3.7±0.6)%, A_{2ϕ}(D^{0}→π^{+}π^{-}μ^{+}μ^{-})=(-0.6±3.7±0.6)%, A_{CP}(D^{0}→π^{+}π^{-}μ^{+}μ^{-})=(4.9±3.8±0.7)%, A_{FB}(D^{0}→K^{+}K^{-}μ^{+}μ^{-})=(0±11±2)%, A_{2ϕ}(D^{0}→K^{+}K^{-}μ^{+}μ^{-})=(9±11±1)%, A_{CP}(D^{0}→K^{+}K^{-}μ^{+}μ^{-})=(0±11±2)%, where the first uncertainty is statistical and the second systematic. The asymmetries are also measured as a function of the dimuon invariant mass. The results are consistent with the standard model predictions.
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
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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 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.
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.
The time-integrated untagged Dalitz plot of the three-body hadronic charmless decay Bover ¯^{0}→K_{S}^{0}π^{+}π^{-} is studied using a pp collision data sample recorded with the LHCb detector, ...corresponding to an integrated luminosity of 3.0 fb^{-1}. The decay amplitude is described with an isobar model. Relative contributions of the isobar amplitudes to the Bover ¯^{0}→K_{S}^{0}π^{+}π^{-} decay branching fraction and CP asymmetries of the flavor-specific amplitudes are measured. The CP asymmetry between the conjugate Bover ¯^{0}→K^{*}(892)^{-}π^{+} and B^{0}→K^{*}(892)^{+}π^{-} decay rates is determined to be -0.308±0.062.
The ratio of branching fractions R(D^{*-})≡B(B^{0}→D^{*-}τ^{+}ν_{τ})/B(B^{0}→D^{*-}μ^{+}ν_{μ}) is measured using a data sample of proton-proton collisions collected with the LHCb detector at ...center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb^{-1}. For the first time, R(D^{*-}) is determined using the τ-lepton decays with three charged pions in the final state. The B^{0}→D^{*-}τ^{+}ν_{τ} yield is normalized to that of the B^{0}→D^{*-}π^{+}π^{-}π^{+} mode, providing a measurement of B(B^{0}→D^{*-}τ^{+}ν_{τ})/B(B^{0}→D^{*-}π^{+}π^{-}π^{+})=1.97±0.13±0.18, where the first uncertainty is statistical and the second systematic. The value of B(B^{0}→D^{*-}τ^{+}ν_{τ})=(1.42±0.094±0.129±0.054)% is obtained, where the third uncertainty is due to the limited knowledge of the branching fraction of the normalization mode. Using the well-measured branching fraction of the B^{0}→D^{*-}μ^{+}ν_{μ} decay, a value of R(D^{*-})=0.291±0.019±0.026±0.013 is established, where the third uncertainty is due to the limited knowledge of the branching fractions of the normalization and B^{0}→D^{*-}μ^{+}ν_{μ} modes. This measurement is in agreement with the standard model prediction and with previous results.
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 first observation of the decay of a B^{0} meson to a purely baryonic final state, B^{0}→ppover ¯, is reported. The proton-proton collision data sample used was collected with the LHCb experiment ...at center-of-mass energies of 7 and 8 TeV and corresponds to an integrated luminosity of 3.0 fb^{-1}. The branching fraction is determined to be B(B^{0}→ppover ¯)=(1.25±0.27±0.18)×10^{-8}, where the first uncertainty is statistical and the second systematic. The decay mode B^{0}→ppover ¯ is the rarest decay of the B^{0} meson observed to date. The decay B_{s}^{0}→ppover ¯ is also investigated. No signal is seen and the upper limit B(B_{s}^{0}→ppover ¯)<1.5×10^{-8} at 90% confidence level is set on the branching fraction.
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