666 research outputs found

    Measurement of lepton universality parameters in B+ →k+l+l- and B0 →k∗0l+l- decays

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    A simultaneous analysis of the B+→K+l+l- and B0→K∗0l+l- decays is performed to test muon-electron universality in two ranges of the square of the dilepton invariant mass, q2. The measurement uses a sample of beauty meson decays produced in proton-proton collisions collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9 fb-1. A sequence of multivariate selections and strict particle identification requirements produce a higher signal purity and a better statistical sensitivity per unit luminosity than previous LHCb lepton universality tests using the same decay modes. Residual backgrounds due to misidentified hadronic decays are studied using data and included in the fit model. Each of the four lepton universality measurements reported is either the first in the given q2 interval or supersedes previous LHCb measurements. The results are compatible with the predictions of the Standard Mode

    Measurement of lepton universality parameters in B plus ? K plus l + l - and B0? K?0l+l- decays

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    A simultaneous analysis of the B+→K+l+l- and B0→K∗0l+l- decays is performed to test muon-electron universality in two ranges of the square of the dilepton invariant mass, q2. The measurement uses a sample of beauty meson decays produced in proton-proton collisions collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9 fb-1. A sequence of multivariate selections and strict particle identification requirements produce a higher signal purity and a better statistical sensitivity per unit luminosity than previous LHCb lepton universality tests using the same decay modes. Residual backgrounds due to misidentified hadronic decays are studied using data and included in the fit model. Each of the four lepton universality measurements reported is either the first in the given q2 interval or supersedes previous LHCb measurements. The results are compatible with the predictions of the Standard Model

    Test of Lepton Flavor Universality with B+ →k+π+π-l+l- Decays

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    The first test of lepton flavor universality between muons and electrons using B+→K+π+π-l+l- (l=e, μ) decays is presented. The measurement is performed with data from proton-proton collisions collected by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9 fb-1. The ratio of branching fractions between B+→K+π+π-e+e- and B+→K+π+π-μ+μ- decays is measured in the dilepton invariant-mass-squared range 1.1<7.0 GeV2/c4 and is found to be RKππ-1=1.31-0.17+0.18(stat) -0.09+0.12(syst), in agreement with the standard model prediction. The first observation of the B+→K+π+π-e+e- decay is also reported

    Test of Lepton Universality in b → sl+ l- Decays

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    The first simultaneous test of muon-electron universality using B+→K+l+l- and B0→K∗0l+l- decays is performed, in two ranges of the dilepton invariant-mass squared, q2. The analysis uses beauty mesons produced in proton-proton collisions collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9 fb-1. Each of the four lepton universality measurements reported is either the first in the given q2 interval or supersedes previous LHCb measurements. The results are compatible with the predictions of the Standard Model

    Search for K S (L)0 →μ+μ-μ+μ- decays at LHCb

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    A search for KS(L)0→μ+μ-μ+μ- decays is performed using proton-proton collision data collected by the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.1 fb-1. No evidence for signal is found. The 90% confidence level upper limits are the first set for both decays and are B(KS0→μ+μ-μ+μ-)<5.1×10-12 and B(KL0→μ+μ-μ+μ-

    Test of Lepton Flavor Universality with B+→K+π+π−l+l− Decays

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    The first test of lepton flavor universality between muons and electrons using Bþ → Kþπþπ−lþl− (l 1⁄4 e, μ) decays is presented. The measurement is performed with data from proton-proton collisions collected by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV, corresponding to an integrated luminosity of 9 fb−1. The ratio of branching fractions between Bþ → Kþπþπ−eþe− and Bþ → Kþπþπ−μþμ− decays is measured in the dilepton invariant-mass-squared range 1.1 < q2 < 7.0 GeV2=c4 and is found to be R−1 Kππ 1⁄4 1.31þ0.18 −0.17 ðstatÞ þ0.12 −0.09 ðsystÞ, in agreement with the standard model prediction. The first observation of the Bþ → Kþπþπ−eþe− decay is also reporte

    Measurement of τL\tau _\text {L} using the Bs0J/ψη{B} _s^0 \rightarrow J/\psi \eta decay mode

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    Using a proton–proton collision data sample collected by the LHCb detector and corresponding to an integrated luminosity of 5.7 fb15.7~\text {fb}^{-1}, the lifetime of the light Bs0{{B} ^0_{s}} mass eigenstate, τL\tau _{L}, is measured using the Bs0J/ψηB^0_s \rightarrow J/\psi \eta decay mode to be τL=1.445±0.016(stat)±0.008(syst)ps.\begin{aligned} \tau _{\text {L}} = 1.445 \pm 0.016 \text {(stat)} \pm 0.008 \text {(syst)} \,\text {ps}. \end{aligned}A combination of this result with a previous LHCb analysis using an independent dataset corresponding to 3 fb1^{-1} of integrated luminosity gives τL=1.452±0.014±0.007±0.002ps,\begin{aligned} \tau _{\text {L}} = 1.452 \pm 0.014 \pm 0.007 \pm 0.002 \,\text {ps}, \end{aligned}where the first uncertainty is statistical, the second due to the uncorrelated part of the systematic uncertainty and the third due to the correlated part of the systematic uncertainty.Using a proton-proton collision data sample collected by the LHCb detector and corresponding to an integrated luminosity of 5.7 fb1\text{fb}^{-1}, the lifetime of the Bs0B_{s}^{0} mass eigenstate, τL\tau_{L}, is measured using Bs0J/ψηB_{s}^{0} \to J/\psi \eta decay mode to be τL\tau_{L} = 1.445 ±\pm 0.016(stat) ±\pm 0.008(syst) ps. A combination of this result with a previous LHCb analysis using an independent dataset corresponding to 3 fb1\text{fb}^{-1} of integrated luminosity gives τL\tau_{L} = 1.452 ±\pm 0.014 ±\pm 0.007 ±\pm 0.002 ps, where the first uncertainty is statistical, the second due to the uncorrelated part of the systematic uncertainty and the third due to the correlated part of the systematic uncertainty

    Search for KS(L)0μ+μμ+μK^0_{\mathrm{S(L)}}\to\mu^+\mu^-\mu^+\mu^- decays at LHCb

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    A search for KS(L)0μ+μμ+μK_{\textrm{S(L)}}^0\rightarrow\mu^{+}\mu^{-}\mu^{+}\mu^{-} decays is performed using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.1 fb1\text{fb}^{-1}. No evidence for signal is found. The 90 % confidence level upper limits are the first set for both decays and are B(KS0μ+μμ+μ)KS(L)0μ+μμ+μdecaysisperformedusingprotonprotoncollisiondatacollectedbytheLHCbexperimentatacenterofmassenergyof13 TeV,correspondingtoanintegratedluminosityof5.1  fb1.Noevidenceforsignalisfound.The90\mathcal{B}(K_{\textrm{S}}^0\rightarrow\mu^{+}\mu^{-}\mu^{+}\mu^{-}) KS(L)0→μ+μ-μ+μ- decays is performed using proton-proton collision data collected by the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.1  fb-1. No evidence for signal is found. The 90% confidence level upper limits are the first set for both decays and are B(KS0→μ+μ-μ+μ-)&lt;5.1×10-12 and B(KL0→μ+μ-μ+μ-)&lt;2.3×10-9.A search for K_{\textrm{S(L)}}^0\rightarrow\mu^{+}\mu^{-}\mu^{+}\mu^{-}decaysisperformedusingprotonprotoncollisiondatacollectedbytheLHCbexperimentatacentreofmassenergyof13TeV,correspondingtoanintegratedluminosityof5.1 decays is performed using proton-proton collision data collected by the LHCb experiment at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.1 fb^{-1}.Noevidenceforsignalisfound.The90. No evidence for signal is found. The 90% confidence level upper limits are the first set for both decays and are B(K_{\textrm{S}}^0\rightarrow\mu^{+}\mu^{-}\mu^{+}\mu^{-}) < 5.1\times 10^{-12}and and B(K_{\textrm{L}}^0\rightarrow\mu^{+}\mu^{-}\mu^{+}\mu^{-}) < 2.3\times 10^{-9}$

    Measurement of the branching fraction ratio RK at large dilepton invariant mass

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    A test of lepton universality between muons and electrons is performed using B+ → K+l+l− decays (where l = e, μ), in the dilepton invariant-mass-squared region above 14.3 GeV2/c4. The data used for the measurement consists of beauty meson decays produced in proton-proton collisions, corresponding to an integrated luminosity of 9 fb−1, collected by the LHCb experiment between 2011 and 2018. The ratio of branching fractions for B+→ K+μ+μ− and B+→ K+e+e− decays is measured to be RK=1.08−0.09+0.11stat−0.04+0.04syst, which is consistent with the Standard Model prediction of unity. This constitutes the most precise test of lepton flavour universality using B+ → K+l+l− decays with dilepton invariant-mass-squared above the ψ(2S) mass, whilst being the first of its kind at a hadron collider

    Search for Ks(L)0 →μ+μ−μ+μ− decays at LHCb

    No full text
    A search for KS(L)0→μ+μ-μ+μ- decays is performed using proton-proton collision data collected by the LHCb experiment at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.1 fb-1. No evidence for signal is found. The 90% confidence level upper limits are the first set for both decays and are B(KS0→μ+μ-μ+μ-)&lt;5.1×10-12 and B(KL0→μ+μ-μ+μ-)&lt;2.3×10-9
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