We update the Standard-Model predictions for several quantities related to $B_s - \bar B_s$ and $B_d - \bar B_d$ mixing. The mass and width differences in the $B_s$ system read $ ΔM_s^{\rm SM} = (17.3 \pm 2.6) ps^{-1}$ and $ΔΓ_s^{\rm SM}= (0.087 \pm 0.021) ps^{-1}$, respectively. The CP asymmetries in flavour-specific decays are $a_{\rm fs}^{s,\rm SM} = (1.9 \pm 0.3) \cdot 10^{-5}$ and $a_{\rm fs}^{d,\rm SM} = - (4.1 \pm 0.6) \cdot 10^{-4}$. We further critically discuss the sensitivity of $ΔΓ_d$ to new physics and the uncertainties in the relation between $ΔΓ_s$ and the branching fraction of $B_s \to D_s^{(*)}{}^+ D_s^{(*)}{}^-$. Then we present a numerical update of the average width $Γ_s$ in the $B_s$ system and correlate $Γ_s$ with the $B^+$-$B_d$ lifetime ratio. Finally we summarise the key results of our recent global analysis with the CKMfitter collaboration addressing new physics in $B - \bar B$-mixing. In an appropriately defined scenario parametrising new physics in $B - \bar B$-mixing by two complex parameters $Δ_d$ and $Δ_s$ the Standard-Model point {$Δ_d=Δ_s=1$} is disfavoured by 3.6 standard deviations.
The Standard Model decay rate of the $B_c$ meson is discussed together with a novel approach that uses experimental data in combination with an operator product expansion. In the new method differences of $B,\,D$ and $B_c$ meson decay rates are considered for which the free-quark contributions drop out, leading to a reduction of the theory prediction.
We review the detection of the Delta L=2 semileptonic meson decays of the form M(+) -> M'(-) lepton(+) lepton(-) that we studied in a previous work, mediated by a Majorana neutrino with a mass in the range between the masses of the initial and final mesons. For such range of masses, the Majorana neutrino will go on its mass shell and the two charged leptons will appear at displaced vertices or, if the lifetime is long enough, most secondary vertices will fall outside the detector. We study the consequences of this effect on the experimental searches and limits that can be extracted.
Even if new data indicate that direct CP violation in D-meson decays is compatible with the standard model expectation, it has triggered a lot of interest, and charm phenomenology will remain an essential part of new physics searches due to its unique role as a probe for flavor-changing neutral currents among up-type quarks. Charm physics poses considerable theoretical challenges, because the charm mass is neither light nor truly heavy. The heavy quark expansion (HQE) provides a perturbative expansion in the inverse heavy quark mass for inclusive rates. It has proved to be very successful in t…
In the heavy quark expansion (HQE) of the total decay rates of $B_s$ and $D_s^+$ mesons non-perturbative matrix elements of four quark operators are arising as phase space enhanced contributions. We present the first determination of $m_s$ effects to the dimension six matrix elements of these four quark operators via a heavy quark effective theory (HQET) sum rule analysis. In addition we calculate for the first time eye contractions of the four quark operators as well as matrix elements of penguin operators. For the perturbative part we solve the 3-loop contribution to the sum rule and we eval…
We present a calculation of $1/m_b^2$ corrections to the lifetime differences of $B_s$ mesons in the heavy-quark expansion. We find that they are small to significantly affect $ΔΓ$ $(B_s)$ and present the result for lifetime difference including non-perturbative $1/m_b$ and $1/m_b^2$ corrections. We also analyze the generic $ΔB$ = 1 New Physics contributions to the lifetime difference of $B_s$ mesons and provide several examples
We present new results concerning the masses and the decay widths of the most interesting hybrid meson states taking as inputs the gluon mass mg and the non-perturbative QCD running coupling constant ?alpha_s(0) comming from both LQCD and SDE recent estimations.
It is argued that the results of recent precision measurements by LHCb of the lifetimes of charmed and bottom hyperons are very well consistent with the description within heavy quark expansion and allow to accurately determine matrix elements of light-flavor nonsinglet four-quark operators over the hyperons and to accurately reproduce the difference of lifemes of $Λ_b$ and $Ξ_b^-$. When combined with the recent LHCb results on the decay $Ξ_b^- \to Λ_b π^-$ this leads to prediction of a lower bound on the rate of the decays $Ξ_c \to Λ_c π$.
This work constitutes one part of an investigation of the low-temperature changes of the properties of the eta' meson. In turn these properties are strongly tied to the U(1)_A anomaly of Quantum Chromodynamics. The final aim is to explore the interplay of the chiral anomaly and in-medium effects. We determine the lifetime of an eta' meson being at rest in a strongly interacting medium as a function of the temperature. To have a formally well-defined low-energy limit we use in a first step Chiral Perturbation Theory for a large number of colors. We determine the pertinent scattering amplitudes …
Effective spectral functions of the $ρ$ meson are reconstructed by considering the lifetimes inside different media using the hadronic transport SMASH (Simulating Many Accelerated Strongly-interacting Hadrons). Due to inelastic scatterings, resonance lifetimes are dynamically shortened (collisional broadening), even though the employed approach assumes vacuum resonance properties. Analyzing the $ρ$ meson lifetimes allows to quantify an effective broadening of the decay width and spectral function, which is important in order to distinguish dynamical effects from additional genuine medium modif…
We present the summary of the Working Group on lifetimes, mixing and weak mixing phases in charm and beauty mesons at the CKM 2010 workshop. In the past year or so good progress was achieved on both experimental and theoretical sides. While this yields improvement in our understanding of neutral meson mixing, further work is necessary to achieve the highest possible precision in order to investigate current hints for deviations between experiment and standard model predictions. With the recent LHC startup we see bright prospects for the near term future for huge improvements.
We investigate a new constraint on new-physics interpretations of the anomalies observed in $B\to D^{(*)}τν$ decays making use of the lifetime of the $B_c^-$ meson. A constraint is obtained by demanding that the rate for $B_c^-\toτ^-\barν$ does not exceed the fraction of the total width that is allowed by the calculation of the lifetime in the standard model. This leads to a very strong bound on new-physics scenarios involving scalar operators since they lift the slight, but not negligible, chiral suppression of the $B_c^-\toτ^-\barν$ amplitude in the standard model. The new constraint renders…
In this work we discuss the theoretical status for the study of the lifetime of heavy hadrons. After presenting some introductory topics like the effective weak Hamiltonian and the heavy quark effective theory (HQET), we describe the construction of the heavy quark expansion (HQE), which constitutes the theoretical framework to systematically compute the total decay width of heavy hadrons, in terms of an expansion in inverse powers of the heavy quark mass. The structure of the HQE is discussed in detail, and the computation of the lowest dimensional contributions, explicitly outlined. Particul…
Non-Spectator Diquark Effects on Lifetimes of Λ_b, Ω_{b}^{(*)} and Weak Decay Rates of Σ_{b}^{(*)}, Ξ_{b}^{(*)}
The difference of τ_{_B} and τ_{_{Λ_b}} indicates the role of the light flavors. We calculate the lifetimes of B-meson and Λ_b based on the weak effective Hamiltonian while assuming the heavy baryon is constructed by a heavy b-quark and a diquark containing two light quarks. In this scenario, we use the information of the measured ratio τ_{_{Λ_b}}/τ_{_B} as input to predict rates of the inclusive weak decays of Σ_{b}^{(*)} and Ξ_{b}^{(*)} into non-bottom final states. We find that these rates of Σ_{b}^{(*)} and Ξ_{b}^{(*)} are much larger than that of B-mesons and Λ_b. We also give the predict…
It is simply anticipated that in a strong magnetic configuration, the Landau quantization ceases the neutral rho meson to decay to the charged pion pair, so the neutral rho meson will be long-lived. To closely access this naive observation, we explicitly compute the charged pion-loop in the magnetic field at the one-loop level, to evaluate the magnetic dependence of the lifetime for the neutral rho meson as well as its mass.Due to the dimensional reduction induced by the magnetic field (violation of the Lorentz invariance), the polarization (spin $s_z=-1,0,+1$) modes of the rho meson, as well …
