Article

Effective lifetimes of Bs decays and their constraints on the B0s-Bs0 mixing parameters

European Physical Journal C (Impact Factor: 5.08). 09/2011; 71(11). DOI: 10.1140/epjc/s10052-011-1789-9

ABSTRACT

Measurements of the effective lifetimes of B s -meson decays, which only require untagged rate analyses, allow us to probe the width difference Delta Gamma s and the CP-violating phase varphi s of B0s-bar{B}0s mixing. We point out that the dependence of the effective lifetime on non-linear terms in Delta Gamma s allows for a determination of varphi s and Delta Gamma s given a pair of B s decays into CP-even and CP-odd final states. Using recent lifetime measurements of B0sto K+K- and B0sto J/psi f0(980) decays, we illustrate this method and show how it complements the constraints in the varphi s -Delta Gamma s plane from other observables.

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    • "Compared to the situation for B 0 decays, the decay-time distribution receives additional terms that do not vanish when integrated over the initial flavour of the B meson. This implies that information about CP violation parameters can be obtained from analyses that do not tag the initial flavour, through so-called effective lifetime measurements [34] [35]. Although analyses that include flavour tagging information will always be more sensitive, this method may still be of interest for analyses based on small event samples, since it is difficult to achieve high effective tagging efficiency at hadron collider experiments such as LHCb. "
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    ABSTRACT: The three-body charmless hadronic decay $B^0_s \rightarrow K^{0}_{\rm S} \pi^{+}\pi^{-}$ provides a number of novel possibilities to search for CP violation effects and test the Standard Model of particle physics. These include fits to the Dalitz-plot distributions of the decay-time-integrated final state, decay-time-dependent (but without initial state flavour tagging) fits to the Dalitz-plot distribution, as well as full decay-time-dependent and flavour tagged fits. The relative sensitivities of these different approaches are investigated.
    Preview · Article · Nov 2014
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    • "Therefore, for non-zero ∆Γ q the decay time distribution of neutral B 0 q decays is not purely exponential. In the case of an equal admixture of B 0 q and B 0 q at t = 0, the observed average decay time is given by [11] "
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    ABSTRACT: Measurements of b-hadron lifetimes are reported using pp collision data, corresponding to an integrated luminosity of 1.0 fb[superscript −1], collected by the LHCb detector at a centre-of-mass energy of 7 TeV. Using the exclusive decays B [superscript +] → J/ψK [superscript +], B [superscript 0] → J/ψK [superscript ∗](892)[superscript 0], B[superscript 0] → J/ψK[0 over s], J/ψΛ and B[0 over s] the average decay times in these modes are measured to be [superscript T] B[superscript +] → J/ψK[superscript +] = 1.637 ± 0.004 ± 0.003ps, [superscript T] B[superscript 0] → J/ψK[superscript +0] = 1.524 ± 0.006 ± 0.004ps, [superscript T] B[superscript 0] → J/ψK[0 over s] = 1.499 ± 0.013 ± 0.005ps, [superscript T] Λ[0 over b] → J/ψΛ = 1.415 ± 0.027 ± 0.006ps, [superscript T] B[0 over b] → J/ψφ = 1.480 ± 0.011 ± 0.005ps, where the first uncertainty is statistical and the second is systematic. These represent the most precise lifetime measurements in these decay modes. In addition, ratios of these lifetimes, and the ratio of the decay-width difference, ΔΓ [subscript d], to the average width, Γ [subscript d], in the B [superscript 0] system, ΔΓ [subscript d]/Γ [subscript d] = −0.044 ± 0.025 ± 0.011, are reported. All quantities are found to be consistent with Standard Model expectations.
    Preview · Article · Aug 2014
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    • "Therefore, for non-zero ∆Γ q the decay time distribution of neutral B 0 q decays is not purely exponential. In the case of an equal admixture of B 0 q and B 0 q at t = 0, the observed average decay time is given by [11] "
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    ABSTRACT: Measurements of $b$-hadron lifetimes are reported using $pp$ collision data, corresponding to an integrated luminosity of 1.0fb$^{-1}$, collected by the LHCb detector at a centre-of-mass energy of $7$Tev. Using the exclusive decays $B^+\to J/\psi K^+$, $B^0\to J/\psi K^*(892)^0$, $B^0\to J/\psi K^0_{\rm S}$, $\Lambda_b^0\to J/\psi \Lambda$ and $B^0_s\to J/\psi \phi$ the average decay times in these modes are measured to be $\tau_{B^+\to J/\psi K^+}$ = $1.637 \pm$ 0.004 $\pm$ 0.003 ps, $\tau_{B^0\to J/\psi K^*(892)^0}$ = $1.524 \pm$ 0.006 $\pm$ 0.004 ps, $\tau_{B^0\to J/\psi K^0_{\rm S}}$ = $1.499 \pm$ 0.013 $\pm$ 0.005 ps, $\tau_{\Lambda_b^0\to J/\psi \Lambda}$ = $1.415 \pm$ 0.027 $\pm$ 0.006 ps and $\tau_{B^0_s\to J/\psi \phi}$ = $1.480 \pm$ 0.011 $\pm$ 0.005 ps, where the first uncertainty is statistical and the second is systematic. These represent the most precise lifetime measurements in these decay modes. In addition, ratios of these lifetimes, and the ratio of the decay-width difference, $\Delta\Gamma_d$, to the average width, $\Gamma_d$, in the $B^0$ system, $\Delta \Gamma_d/\Gamma_d = -0.044 \pm 0.025 \pm 0.011$, are reported. All quantities are found to be consistent with Standard Model expectations.
    Preview · Article · Jan 2014
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