本文完成了重强子寿命重夸克展开中维度六算符的贡献计算，给出了 Darwin 项和自旋-轨道项 Wilson 系数在树图阶的表达式，补全了 $1/m_b^3$ 阶修正。
摘要：
我们完成了重强子总寿命的重夸克展开中维度六算符贡献的计算。我们给出了 Darwin 项 $ρ_D$ 和自旋-轨道项 $ρ_{\ m LS}$ 的 Wilson 系数在树图阶的表达式。
英文摘要：
We complete the calculation of the contributions from the dimension six operators in the heavy quark expansion for the total lifetime of heavy hadrons. We give the expressions for the Wilson coefficients of the Darwin term $ρ_D$ and the spin-orbit term $ρ_{\rm LS}$ at tree level.
We compute four-loop corrections to the hadronic decay of the Standard Model Higgs boson which are induced by effective couplings to bottom quarks and gluons, mediated by the top quark. Our numerical results are comparable in size to the purely massless contributions which have been known for a few years. The results presented in this paper complete the order $α_s^4$ corrections to the hadronic Higgs boson decay.
We compute the contributions of dimension six two-quark operators to the non-leptonic decay width of heavy hadrons due to the flavor changing bottom-to-up-quark transition in the heavy quark expansion. Analytical expressions for the Darwin term $ρ_D$ and the spin-orbit term $ρ_{\rm LS}$ are obtained with leading order accuracy.
We review recent experimental results on hadronic decays and lifetimes of hadrons containing b and c quarks. We discuss charm counting and the semileptonic branching fraction in B decays, the color suppressed amplitude in B and D decay, and the search for gluonic penguins in B decay.
The status of heavy quark expansions for charm and beauty lifetime ratios is reviewed. Taking note of the surprising semiquantitative success of this description for charm hadrons I interprete the new data on $τ(D_s)$ and re-iterate the call for more precise measurements of $τ(Ξ_c^{0,+})$ and $τ(Ω_c)$. A slightly larger $B^-$ than $B_d$ lifetime is starting to emerge as predicted; the largest lifetime difference in the beauty sector, namely in $τ(B_c)$ vs. $τ(B)$ has correctly been predicted; the problem posed by the short $Λ_b$ lifetime remains. The need for more accurate data also on $τ(B_s)…
The problem of the hierarchy of lifetimes of charmed hadrons is reviewed. The QCD-based theory of preasymptotic effects in inclusive weak decays dating back to the beginning of the eighties is now entering its mature phase. Combining recent and old results we argue that the observed hierarchy reflects most intimate features of the hadronic structure. The problem of a wide spread of lifetimes of charmed hadrons is addressed. We speculate on what is to be expected from QCD to provide the observed pattern. A number of predictions is given for the hierarchy of lifetimes in the family of the beauti…
Hadron elementary particle measurements have long revealed an alpha-dependence in the long-lived threshold-state lifetimes, together with an alpha-related mass structure, where alpha ~ 1/137 is the fine structure constant. A detailed lifetime analysis shows that of the 156 particles with well-determined lifetimes, the 120 shortest lifetimes have a continuum of values, but the 36 longer lifetimes occur in alpha-spaced groups which are sorted into s, c, b quark flavors. Guided by these lifetime results, we deduce an alpha-generated set of universal mass quanta, based on the electron ground state…
We review current status of theoretical predictions of lifetimes of heavy hadrons in heavy-quark expansion. We present a calculation of subleading 1/m_b corrections to spectator effects in the ratios of beauty hadron lifetimes. We find that these effects are sizable and should be taken into account in systematic analyses of heavy hadron lifetimes. In particular, the inclusion of 1/m_b corrections brings into agreement the theoretical predictions and experimental observations of the ratio of lifetimes of Lambda_b-baryon and B_d meson. We obtain τ(B_u)/τ(B_d) = 1.09 \pm 0.03, τ(B_s)/τ(B_d)= 1.00…
A theoretical treatment for the weak decays of heavy-flavour hadrons has been developed that is genuinely based on QCD. Its methodology as it applies to total lifetimes and the underlying theoretical issues are sketched. Predictions are compared with present data. One discrepancy emerges: the beauty baryon lifetime appears to be significantly shorter than expected. The ramifications of those findings are analyzed in detail.
B-hadron physics plays a fundamental role to test and improve our understanding of flavor dynamics within and beyond the Standard Model. Of particular phenomenological interest are beauty hadron lifetime ratios and, width differences and semileptonic CP-asymmetries in B_d and B_s systems. We discuss their theoretical predictions which, in the last years, have been improved thanks to accurate lattice calculations of operator matrix elements and perturbative computations of Wilson coefficients.
We review the status of mixing and lifetimes of $b$-hadrons. We will show that $ΔΓ/ ΔM$, $a_{sl}$ and $ϕ$ are better suited to search for new physics effects than $ΔM$ alone, because of our poor knowledge of the decay constants. The theoretical precision in the determination of $Γ_{12} / M_{12}$ - which contains all information on $ΔΓ/ ΔM$, $a_{sl}$ and $ϕ$ - can be tested directly by investigating the lifetimes of $b$-hadrons, because both quantities rely on the same theoretical footing. In particular we will also present a numerical estimate for the lifetime of the $Ξ_b$-baryon.
We develop perturbative QCD factorization theorems for inclusive b-hadron decays, in which radiative corrections characterized by the hadronic scale, the b-hadron mass, and the W boson mass are absorbed into a heavy hadron distribution function, a hard b quark decay amplitude, and a "harder" function, respectively. Double logarithmic corrections associated with a light energetic final-state quark, which appear at kinematic end points, are absorbed into a jet function. Various large logarithms contained in the above functions are summed to all orders, leading to the evolution factors among the …
I discuss the heavy quark expansion for the inclusive widths of heavy-light hadrons, which predicts quite well the experimental ratios of B_q meson lifetimes. As for $Λ_b$, current determinations of ${\cal O}(m_b^{-3})$ contribution to $τ(Λ_b)$ do not allow to explain the small measured value of $τ(Λ_b)/τ(B_d)$. As a final topic, I discuss the implications of the measurement of the B_c lifetime.
The lifetime splitting between the B^+ and B_d^0 mesons has recently been calculated in the next-to-leading order of QCD. These corrections are necessary for a reliable theoretical prediction, in particular for the meaningful use of hadronic matrix elements computed with lattice QCD. Using results from quenched lattice QCD we find tau(B^+)/tau(B^0_d)=1.053 +/- 0.016 +/- 0.017, where the uncertainties from unquenching and 1/m_b corrections are not included. The lifetime difference of heavy baryons Xi_b^0 and Ξ_b^- is also discussed.
Hadronic corrections to the muon lifetime are calculated in the Fermi theory in the presence of QED using dispersion relations. The result, after convolution of hadron data with the calculated perturbative kernel is Delta Gamma_had = -Gamma_0(alpha/pi)^2(0.042) where Gamma_0 is the tree-level width. The results are also used to obtain the corrections to the muon lifetime coming from virtual muon and tau loops Delta Gamma_muon = Gamma_0(alpha/pi)^2[(16987/576)-(85/36)zeta(2)-(64/3)zeta(3)] = -Gamma_0(alpha/pi)^2(0.0364333) Delta Gamma_tau = -Gamma_0(alpha/pi)^2)(0.00058)
We discuss (i) the evaluation of the expectation values of four-quark operators assuming that the heavy quark expansion for $b$ sector converges at the third order in $1/m_Q$, and (ii) the estimation of the duality breaking short distance nonperturbative corrections to the parton decay rate. We finally point out the implications of the result obtained for the assumption of quark-hadron duality in heavy quark expansion.
We show that in a confining hidden valley model where the lightest hidden particles are dark hadrons that have mass splittings larger than $\mathcal{O}(0.1)$ GeV, if the lightest dark hadron is either stable or decays into Standard Model (SM) hadrons/charged leptons during the big-bang nucleosynthesis (BBN), at least one of the heavier dark hadrons needs to decay into SM particles within $\mathcal{O}(10)$ nanosec. Once being produced at collider experiments, this heavier dark hadron is likely to decay within $\mathcal{O}(1)$ meter distance, which strengthens the motivation of searching for lon…
We give an updated summary of the topics covered in Working Group I of the 2nd Workshop on the CKM Unitarity Triangle, with emphasis on the results obtained since the 1st CKM Workshop. The topics covered include the measurement of |V_{ub}|, of |V_{cb}| and of non-perturbative Heavy Quark Expansion parameters, and the determination of b-hadron lifetimes and lifetime differences.
Over the last few years a theoretical treatment for the weak decays of heavy-flavour hadrons has been developed that is genuinely based on QCD. Its methodology is described as it applies to total lifetimes, and the underlying theoretical issues are discussed. Theoretical expectations are compared with present data. One discrepancy emerges: the beauty baryon lifetime appears to be significantly shorter than predicted. The ramifications of those findings are analyzed in detail, and future refinements are described.
In this talk we review the theoretical status of the lifetime ratios of heavy hadrons and of the B-mixing quantities $ΔM_s$, $ΔΓ_s$ and $ϕ_s$. While $ΔM_s$ and $ΔΓ_s$ suffer from large uncertainties due to the badly known decay constants, the ratio $ΔΓ_s / ΔM_s$ can be determined with almost no non-perturbative uncertainties, therefore it can be used to look for possible new physics effects.
The preasymptotic effects originating from the four-quark operators are disentangled from the other contributions by considering appropriate combinations of inclusive decay rates. Under the assumption of the isospin and heavy-quark symmetry, a set of relations connecting charmed and beauty decays is obtained without invoking specific models. The results are compared with other approaches and confronted with experiment.
We review recent experimental results on lifetimes and hadronic decays of hadrons that contain $c$ and $b$ quarks. The theoretical implications of these results are also considered. An understanding of hadronic decays of heavy quarks is required to interpret the CP violating asymmetries in $B$ decays that will be observed in experiments planned for the near future.
The lifetime differences of bottom hadrons are known to be properly explained within the framework of heavy quark effective field theory(HQEFT) of QCD via the inverse expansion of the dressed heavy quark mass. In general, the spectrum around the endpoint region is not well behaved due to the invalidity of $1/m_Q$ expansion near the endpoint. The curve fitting method is adopted to treat the endpoint behavior. It turns out that the endpoint effects are truly small and the explanation on the lifetime differences in the HQEFT of QCD is then well justified. The inclusion of the endpoint effects mak…
Inclusive bottom hadron decays are analyzed based on the heavy quark effective field theory (HQEFT). Special attentions in this paper are paid to the b\to u transitions and nonspectator effects. As a consequence, the CKM quark mixing matrix elements |V_ub| and |V_cb| are reliably extracted from the inclusive semileptonic decays B\to X_u e νand B\to X_c e ν. Various observables, such as the semileptonic branch ratio B_SL, the lifetime differences among B^-, B^0, B_s and Λ_b hadrons, the charm counting n_c, are predicted and found to be consistent with the present experimental data.
We describe a theoretical approach to compute inclusive widths of heavy hadrons, based on a systematic expansion in the inverse powers of the heavy quark mass. The method reproduces quite well the experimental ratios of $B$ mesons lifetimes. As for $τ(Λ_b)/τ(B_d)$, we present a QCD sum rule calculation of the $O(m_b^{-3})$ contribution to $τ(Λ_b)$; we conclude that such correction is not responsible of the small experimental value of $τ(Λ_b)/τ(B_d)$.
A detailed, quantitative re-examination of the effect of hadron dynamics on baryon decay, modeled in terms of Skyrme-field tunneling, indicates that any hadronic suppression should be quite mild. This appears to be another illustration of the `Cheshire-cat' phenomenon, that variation of the apportionment between description of the nucleon as a bag of quarks and description as a Skyrme field configuration has little influence on many nucleon properties. Perhaps the largest remaining uncertainty in evaluating the decay rate has to do with the overlap between a specified quark-antiquark configura…
Inclusive heavy-flavour decays can be described through $1/m_Q$ expansions derived from QCD with the help of an operator product expansion. I sketch their methodology and apply them first to semileptonic B decays; $|V(cb)|$ can be extracted from $Γ_{SL}(B)$ and $\bar B \to l νD^*$ with the result: $|V(cb)|_{incl} = 0.0413 \pm 0.0016_{exp} \pm 0.002_{theor}$, $|V(cb)|_{excl} = 0.0377 \pm 0.0016_{exp} \pm 0.002_{theor}$. The lifetimes of charm and beauty hadrons are discussed. The charm lifetimes are predicted/reproduced as well as could be expected. Predictions on B meson lifetimes agree with a…
The heavy quark expansion implemented through an operator product expansion provides us with a treatment of inclusive decays of beauty and charm hadrons that is genuinely derived from QCD,though it requires one additional assumption, namely that of 'local' quark-hadron duality. Subtleties in the application of factorization to hadronic expectation values are pointed out. The observed pattern in the charm lifetime ratios is reproduced in a semi-quantitative manner. The ratio $τ(Λ_b)/τ(B_d)$ cannot be pushed significantly below 0.9 -- unless one invokes a new hitherto unknown paradigm for evalua…
A phenomenological analysis of lifetimes of bottom and charmed hadrons within the framework of the heavy quark expansion is performed. The baryon matrix element is evaluated using the bag model and the nonrelativistic quark model. We find that bottom-baryon lifetimes follow the pattern $τ(Ω_b)\simeqτ(Ξ_b^-)>τ(Λ_b)\simeqτ(Ξ_b^0)$. However, neither the lifetime ratio $τ(Λ_b)/τ( B_d)$ nor the absolute decay rates of the $Λ_b$ baryon and $B$ mesons can be explained. One way of solving both difficulties is to allow the presence of linear $1/m_Q$ corrections by scaling the inclusive nonleptonic widt…
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…
Top-quark physics plays an important role at hadron colliders such as the Tevatron collider at Fermilab or the upcoming Large Hadron Collider (LHC) at CERN. Given the planned experimental precision, detailed theoretical predictions are mandatory. In this article we present analytic results for the complete electroweak corrections to gluon induced top-quark pair production, completing our earlier results for the quark-induced reaction. As an application we discuss top-quark pair production at Tevatron and at LHC. In particular we show that, although small for inclusive quantities, weak correcti…
Combined results on b-hadron lifetimes, b-hadron production rates, B^0_d - \bar{B^0_d} and B^0_s -\bar{B^0_s} oscillations, the decay width difference between the mass eigenstates of the B^0_s -\bar{B^0_s} system, and the values of the CKM matrix elements | V_cb | and \Vert V_ub | are obtained from published and preliminary measurements available in Summer 99 from the ALEPH, CDF, DELPHI, L3, OPAL and SLD Collaborations.
Lifetime differences of heavy hadrons can be consistently computed in heavy-quark expansion. The leading effects appear through spectator interactions at order 1/m_b^3. We compute a well-defined subset of 1/m_b^4 corrections to the lifetime ratio of Lambda_b baryon and B_d meson. We find that these corrections are large and should be taken into account in the systematic analysis of heavy hadron lifetimes. We claim that they could shift the ratio τ_{Λ_b}/τ_{B_d} by as much as -4.5%, significantly reducing the discrepancy between the theoretical predictions and experimental observations.
We present the theoretical status of the lifetimes of weakly decaying heavy hadrons containing a bottom or a charm quark, and discuss the current predictions, based on the framework of the Heavy Quark Expansion (HQE), for both mesons and baryons. Potential improvements to reduce the theoretical uncertainties are also highlighted.
Recent measurements of lifetimes of some $b$-flavored hadrons are presented and interpreted in the context of theoretical models, especially the Heavy Quark Expansion. Decay widths and decay width differences in the $B_s^0-\overline{B}_s^0$ system are discussed from studies of decays into the final states $J/ψK^+K^-$, $J/ψπ^+π^-$, $D_s^+D_s^-$, $K^+K^-$, and $D_s^{\pm}π^{\mp}$. Lifetime measurements of the baryons $Λ_b^0$, $Ξ_b^-$, $Ξ_b^0$, and $Ω_b^-$ are also shown.
We present a calculation of subleading 1/m_b corrections to spectator effects in the ratios of beauty hadron lifetimes in heavy-quark expansion. We find that these effects are sizable and should be taken into account in systematic analyses of heavy hadron lifetimes. In particular, the inclusion of 1/m_b corrections brings into agreement the theoretical predictions and experimental observations of the ratio of lifetimes of Λ_b-baryon and B_d meson. We obtain τ(B_u)/τ(B_d) = 1.06 \pm 0.02, τ(B_s)/τ(B_d)= 1.00 \pm 0.01, τ(Λ_b)/τ(B_d)= 0.86 \pm 0.05.
Λ_b matrix element of four-quark operator relevant to its lifetime is reanalyzed by QCD sum rule. The new ingredients introduced are that (1) more vacuum condensates are considered; (2) different quark-hadron duality is adopted; and (3) the possible deviation from the vacuum saturation assumption for the four quark condensates is considered. With κ_1=4 the related hadronic parameter r is calculated to be 3.6 \pm 0.9, and the lifetime ratio τ(Λ_b)/τ(B^0) = 0.83 \pm 0.04, which is consistent with the experimental data.
We compute the real part of the 2-loop vertex corrections for charmless hadronic B decays, completing the NNLO calculation of the topological tree amplitudes in QCD factorization. Among the technical aspects we show that the hard-scattering kernels are free of soft and collinear infrared divergences at the 2-loop level, which follows after an intricate subtraction procedure involving evanescent four quark operators. The numerical impact of the considered corrections is found to be moderate, whereas the factorization scale dependence of the topological tree amplitudes is significantly reduced a…
We discuss neutral B_{s,d} meson mixing and b-hadron lifetimes from the perspective of recent lattice calculations. In particular, we consider matrix elements which can be combined with measured ΔM_{s,d} to constrain |V_{td}|, the lifetime ratios τ(Λ_b)/τ(B_d) and τ(B^-)/τ(B_d) and the lifetime difference, ΔΓ_s/Γ_s, in the neutral B_s meson system.
Hadronic resonances, having very short lifetime, like $\rm{K}^{*0}$, can act as useful probes to understand and estimate lifetime of hadronic phase in ultra-relativistic proton-proton, p--Pb and heavy-ion collisions. Resonances with relatively longer lifetime, like $ϕ$ meson, can serve as a tool to locate the QGP phase boundary. We estimate a lower limit of hadronic phase lifetime in Cu--Cu and Au--Au collisions at RHIC, and in pp, p--Pb and Pb--Pb collisions at different LHC collision energies. Also, we obtain the effective temperature of $ϕ$ meson using Boltzmann-Gibbs Blast-Wave function, w…
We provide an extensive study of the lifetimes of singly charmed baryons and mesons, within the heavy quark expansion with all known corrections included. A special attention is devoted to the choice of the charm mass and wavefunctions of heavy baryons. We give our predictions for lifetimes, lifetime ratios, and semileptonic branching ratios of singly charmed baryons. Our results accommodate the experimentally-favoured hierarchy of singly charmed baryon lifetimes \begin{eqnarray*} τ\left(Ξ_c^{0}\right) < τ\left(Λ_c^{+}\right)< τ\left(Ω_c^{0}\right) < τ\left(Ξ_c^{+}\right)\, \end{eqnarray*} in …
We examine Higgs boson production and decay in heavy-ion collisions at the LHC and future colliders. Owing to the long lifetime of the Higgs boson, its hadronic decays may experience little or no screening from the hot and dense quark-gluon plasma whereas jets from hard scattering processes and from decays of the electro-weak gauge bosons and the top-quark suffer significant energy loss. This distinction can lead to enhanced signal to background ratios in hadronic decay channels and thus, for example, provide alternative ways to probe the Yukawa coupling of the Higgs boson to the bottom quark …
We compute the next-to-leading order QCD corrections to spectator effects in the lifetime ratios of beauty hadrons. With respect to previous calculations, we take into account the non vanishing value of the charm quark mass. We obtain the predictions tau(B+)/tau(Bd) = 1.06 +- 0.02, tau(Bs)/tau(Bd)= 1.00 +- 0.01 and tau(Lambdab)/tau(Bd) = 0.90 +- 0.05, in good agreement with the experimental results. In the case of tau(Bs)/tau(Bd) and tau(Lambdab)/tau(Bd), however, some contributions, which either vanish in the vacuum insertion approximation or represent a pure NLO corrections, have not been de…
We review recent measurements of heavy B hadron states including masses and lifetimes of the Bc meson as well as excited B states (B**, Bs**). We discuss properties of the Bs meson such as lifetime, lifetime difference delta_Gamma/Gamma and CP violation in Bs -> J/Psi Phi decays. We also summarize new measurements of the masses and lifetimes of bottom baryons including the Lambda_b baryon, the Sigma_b baryon states as well as the Xi_b and Omega_b baryons.
The QCD-based operator-product-expansion technique is systematically applied to the study of charmed meson lifetimes. We stress that it is crucial to take into account the momentum of the spectator light quark of charmed mesons, otherwise the destructive Pauli-interference effect in $D^+$ decays will lead to a negative decay width for the $D^+$. We have applied the QCD sum rule approach to estimate the hadronic matrix elements of color-singlet and color-octet 4-quark operators relevant to nonleptonic inclusive $D$ decays. The lifetime of $D_s^+$ is found to be longer than that of $D^0$ because…
We compute perturbative QCD corrections to the lifetime splitting between the charged and neutral $B$ meson in the framework of the heavy quark expansion. These next-to-leading logarithmic corrections are necessary for a meaningful use of hadronic matrix elements of local operators from lattice gauge theory. We find the uncertainties associated with the choices of renormalization scale and scheme significantly reduced compared to the leading-order result. We include the full dependence on the charm-quark mass $m_c$ without any approximations. Using hadronic matrix elements estimated in the lit…
We address a discrepancy between different computations of $η/s$ (shear viscosity over entropy density) of hadronic matter. Substantial deviations of this coefficient are found between transport approaches mainly based on resonance propagation with finite lifetime and other (semi-analytical) approaches with energy-dependent cross-sections, where interactions do not introduce a timescale. We provide an independent extraction of this coefficient by using the newly-developed SMASH (Simulating Many Accelerated Strongly interacting Hadrons) transport code, which is an example of a mainly resonance-…
At the order of 1/m_b^3, the B meson lifetimes are controlled by the hadronic matrix elements of some four-quark operators. The nonfactorizable magnitudes of these four-quark operator matrix elements are analyzed by QCD sum rules in the framework of heavy quark effective theory. The vacuum saturation for color-singlet four-quark operators is justified at hadronic scale, and the nonfactorizable effect is at a few percent level. However for color-octet four-quark operators, the vacuum saturation is violated sizably that the nonfactorizable effect cannot be neglected for the B meson lifetimes. Th…
The lifetimes of bottom and charmed hadrons are analyzed within the framework of the heavy quark expansion (HQE). Lifetime differences arise from the spectator effects such as weak $W$-annihilation and Pauli interference. Spectator effects originating from dimension-7 four-quark operators are derived. Hadronic matrix elements of four-quark operators are parameterized in a model-independent way. Using the dimension-6 bag parameters recently determined from HQET sum rules and the vacuum insertion approximation for meson matrix elements of dimension-7 operators, the calculated $B$ meson lifetime …
The present status of the theoretical estimates of beauty hadron lifetime ratios and of width differences and CP-violation parameters in $B_d$ and $B_s$ systems is reviewed. In the last two years accurate lattice calculations and next-to-leading order perturbative computations have improved these theoretical predictions, leading to the following updated results: τ(B^+)/τ(B_d)=1.06 +- 0.02, τ(B_s)/τ(B_d)=1.00 +- 0.01, τ(Λ_b)/τ(B_d)=0.88 +- 0.05, ΔΓ_{d}/Γ_{d} = (2.42 +- 0.59)10^{-3}, ΔΓ_{s}/Γ_{s} = (7.4 +- 2.4)10^{-2}, |(q/p)_d|-1=(2.96 +- 0.67) 10^{-4}$ and |(q/p)_s|-1=-(1.28 +- 0.28) 10^{-5}
Theoretical predictions of beauty hadron lifetimes, based on the heavy quark expansion up to and including order 1/mb^2, do not to reproduce the experimental measurements of the lifetime ratios tau(B+)/tau(Bd) and tau(Lambdab)/tau(Bd). Large corrections to these predictions come from phase-space enhanced 1/mb^3 contributions, i.e. hard spectator effects. In this paper we calculate the next-to-leading order QCD corrections to the Wilson coefficients of the local operators appearing at O(1/mb^3). We find that these corrections improve the agreement with the experimental data. The lifetime ratio …
We discuss two problems in the theory of heavy-quark decays: an understanding of the semileptonic branching ratio of $B$ mesons, and of the lifetime ratio $τ(Λ_b)/τ(B^0)$. We also present a model-independent study of spectator contributions to the lifetimes of beauty hadrons.
When SUSY breaking produces only dimension-2 operators, gluino and photino masses are of order 1 GeV or less. The gluon-gluino bound state has mass 1.3-2.2 GeV and lifetime > 10^{-5} - 10^{-10} s. This range of mass and lifetime is largely unconstrained because missing energy and beam dump techniques are ineffective. With only small modifications, upcoming K^0 decay experiments can study most of the interesting range. The lightest gluino-containing baryon (uds-gluino) is long-lived or stable; experiments to find it and the uud-gluino are also discussed.
The motion of spectator quarks in decay of a beauty hadron is a nonperturbative effect which can usually be neglected. We find that the motion in some decay channels, which contribute total decay widths of beauty hadrons, can not be neglected.The contributions from these decay channels to decay widths are proportional to certain averages of the squared inverse of the momentum carried by a spectator quark. This fact results in that these contributions, suppressed by $1/m_b^3$ formally, are effectively suppressed by $1/m_b$. We find these contributions can be factorized into products of perturba…
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…
