A measurement of the phase difference between the short- and long-distance contributions to the
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\begin{document}$${{B} ^+} \!\rightarrow {{{K}} ^+} {\mu ^+\mu ^-} $$\end{document}
B
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μ
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μ
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decay is performed by analysing the dimuon mass distribution. The analysis is based on
pp
collision data corresponding to an integrated luminosity of 3
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\begin{document}$$\mathrm{\,fb}^{-1}$$\end{document}
fb
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collected by the LHCb experiment in 2011 and 2012. The long-distance contribution to the
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\begin{document}$${{B} ^+} \!\rightarrow {{{K}} ^+} {\mu ^+\mu ^-} $$\end{document}
B
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μ
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decay is modelled as a sum of relativistic Breit–Wigner amplitudes representing different vector meson resonances decaying to muon pairs, each with their own magnitude and phase. The measured phases of the
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\begin{document}$${{J}/\psi }$$\end{document}
J
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and
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\begin{document}$$\psi {(2S)}$$\end{document}
ψ
(
2
S
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resonances are such that the interference with the short-distance component in dimuon mass regions far from their pole masses is small. In addition, constraints are placed on the Wilson coefficients,
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\begin{document}$$\mathcal {C}_{9}$$\end{document}
C
9
and
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\begin{document}$$\mathcal {C}_{10}$$\end{document}
C
10
, and the branching fraction of the short-distance component is measured.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
A search for charge-parity (CP) violation in Cabibbo-suppressed D_{s}^{+}→K_{S}^{0}π^{+}, D^{+}→K_{S}^{0}K^{+}, and D^{+}→ϕπ^{+} decays is reported using proton-proton collision data, corresponding ...to an integrated luminosity of 3.8 fb^{-1}, collected at a center-of-mass energy of 13 TeV with the LHCb detector. High-yield samples of kinematically and topologically similar Cabibbo-favored D_{(s)}^{+} decays are analyzed to subtract nuisance asymmetries due to production and detection effects, including those induced by CP violation in the neutral kaon system. The results areA_{CP}(D_{s}^{+}→K_{S}^{0}π^{+})=(1.3±1.9±0.5)×10^{-3},A_{CP}(D^{+}→K_{S}^{0}K^{+})=(-0.09±0.65±0.48)×10^{-3},A_{CP}(D^{+}→ϕπ^{+})=(0.05±0.42±0.29)×10^{-3},where the first uncertainties are statistical and the second systematic. They are the most precise measurements of these quantities to date, and are consistent with CP symmetry. A combination with previous LHCb measurements, based on data collected at 7 and 8 TeV, is also reported.
The first observation of the decays B_{(s)}^{0}→J/ψppover ¯ is reported, using proton-proton collision data corresponding to an integrated luminosity of 5.2 fb^{-1}, collected with the LHCb ...detector. These decays are suppressed due to limited available phase space, as well as due to Okubo-Zweig-Iizuka or Cabibbo suppression. The measured branching fractions are B(B^{0}→J/ψppover ¯)=4.51±0.40(stat)±0.44(syst)×10^{-7}, B(B_{s}^{0}→J/ψppover ¯)=3.58±0.19(stat)±0.39(syst)×10^{-6}. For the B_{s}^{0} meson, the result is much higher than the expected value of O(10^{-9}). The small available phase space in these decays also allows for the most precise single measurement of both the B^{0} mass as 5279.74±0.30(stat)±0.10(syst) MeV and the B_{s}^{0} mass as 5366.85±0.19(stat)±0.13(syst) MeV.
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 cross section for prompt antiproton production in collisions of protons with an energy of 6.5 TeV incident on helium nuclei at rest is measured with the LHCb experiment from a data set ...corresponding to an integrated luminosity of 0.5 nb^{-1}. The target is provided by injecting helium gas into the LHC beam line at the LHCb interaction point. The reported results, covering antiproton momenta between 12 and 110 GeV/c, represent the first direct determination of the antiproton production cross section in p-He collisions, and impact the interpretation of recent results on antiproton cosmic rays from space-borne experiments.
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.
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.
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.
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