Search

We use functional methods to match the Two-Higgs Doublet Model with heavy scalars in the nondecoupling regime to the appropriate nonlinear effective field theory, which takes the form of an electroweak chiral Lagrangian (HEFT). The effective Lagrangian is derived to leading order in the chiral counting. This includes the loop induced $h\to\gamma\gamma$ and $h\to Z\gamma$ local terms, which enter at the same chiral order as their counterparts in the Standard Model. An algorithm is presented that allows us to compute the coefficient functions to all orders in $h$. Some of the all-orders results are given in closed form. The parameter regimes for decoupling, nondecoupling and alignment scenarios in the effective field theory context and some phenomenological implications are briefly discussed., Comment: 20 pages, no figures; v2: paragraph on custodial symmetry breaking and further references added, matches published version

We show that, in addition to the counting of canonical dimensions, a counting of loop orders is necessary to fully specify the power counting of Standard Model Effective Field Theory (SMEFT). Using concrete examples, we demonstrate that considering the canonical dimensions of operators alone may lead to inconsistent results. The counting of both, canonical dimensions and loop orders, establishes a clear hierarchy of the terms in SMEFT. In practice, this serves to identify, and focus on, the potentially dominating effects in any given high-energy process in a meaningful way. Additionally, this will lead to a consistent limitation of free parameters in SMEFT applications., Comment: 27 pages, 2 figures; references and minor comments added, version published in SciPost

Starting from the one-loop divergences we obtained previously, we work out the renormalization of the Higgs-Electroweak Chiral Lagrangian explicitly and in detail. This includes the renormalization of the lowest-order Lagrangian, as well as the decomposition of the remaining divergences into a complete basis of next-to-leading-order counterterms. We provide the list of the corresponding beta functions. We show how our results match the one-loop renormalization of some of the dimension-6 operators in SMEFT. We further point out differences with related work in the literature and discuss them. As an application of the obtained results, we evaluate the divergences of the vacuum expectation value of the Higgs field at one loop and show that they can be appropriately removed by the corresponding renormalization. We also work out the finite renormalization required to keep the no-tadpole condition on the Higgs field at one loop., Comment: 37 pages, no figures

This document summarises the current theoretical and experimental status of the di-Higgs boson production searches, and of the direct and indirect constraints on the Higgs boson self-coupling, with the wish to serve as a useful guide for the next years. The document discusses the theoretical status, including state-of-the-art predictions for di-Higgs cross sections, developments on the effective field theory approach, and studies on specific new physics scenarios that can show up in the di-Higgs final state. The status of di-Higgs searches and the direct and indirect constraints on the Higgs self-coupling at the LHC are presented, with an overview of the relevant experimental techniques, and covering all the variety of relevant signatures. Finally, the capabilities of future colliders in determining the Higgs self-coupling are addressed, comparing the projected precision that can be obtained in such facilities. The work has started as the proceedings of the Di-Higgs workshop at Colliders, held at Fermilab from the 4th to the 9th of September 2018, but it went beyond the topics discussed at that workshop and included further developments., Comment: 279 pages, 136 figures, document produced partially as outcome of the conference Double Higgs Production at Colliders - Fermilab - Chicago (US) 4 - 9 September 2018. Submitted to Review in Physics. The editors can be contacted at the following address: hh-2018-paper-editors@cern.ch

The discovery of the Higgs boson in 2012, by the ATLAS and CMS experiments, was a success achieved with only a percent of the entire dataset foreseen for the LHC. It opened a landscape of possibilities in the study of Higgs boson properties, Electroweak Symmetry breaking and the Standard Model in general, as well as new avenues in probing new physics beyond the Standard Model. Six years after the discovery, with a conspicuously larger dataset collected during LHC Run 2 at a 13 TeV centre-of-mass energy, the theory and experimental particle physics communities have started a meticulous exploration of the potential for precision measurements of its properties. This includes studies of Higgs boson production and decays processes, the search for rare decays and production modes, high energy observables, and searches for an extended electroweak symmetry breaking sector. This report summarises the potential reach and opportunities in Higgs physics during the High Luminosity phase of the LHC, with an expected dataset of pp collisions at 14 TeV, corresponding to an integrated luminosity of 3 ab$^{-1}$. These studies are performed in light of the most recent analyses from LHC collaborations and the latest theoretical developments. The potential of an LHC upgrade, colliding protons at a centre-of-mass energy of 27 TeV and producing a dataset corresponding to an integrated luminosity of 15 ab$^{-1}$, is also discussed., Comment: Report from Working Group 2 on the Physics of the HL-LHC, and Perspectives at the HE-LHC, 364 pages

We present a calculation of the NLO QCD corrections to Higgs boson pair production within the framework of a non-linearly realised Effective Field Theory in the Higgs sector, described by the electroweak chiral Lagrangian. We analyse how the NLO corrections affect distributions in the Higgs boson pair invariant mass and the transverse momentum of one of the Higgs bosons. We find that these corrections lead to significant and non-homogeneous K-factors in certain regions of the parameter space. We also provide an analytical parametrisation for the total cross-section and the $m_{hh}$ distribution as a function of the anomalous Higgs couplings that includes NLO corrections. Such a parametrisation can be useful for phenomenological studies., Comment: 40 pages, 26 figures, v2: published version; v3: ancillary files for 13, 14 and 27 TeV for LO and NLO differential cross sections and usage example added

Employing background-field method and super-heat-kernel expansion, we compute the complete one-loop renormalization of the electroweak chiral Lagrangian with a light Higgs boson. Earlier results from purely scalar fluctuations are confirmed as a special case. We also recover the one-loop renormalization of the conventional Standard Model in the appropriate limit., Comment: 15 pages, no figures; v2: reference and comments added, typos fixed, matches published version

This Report summarizes the results of the activities of the LHC Higgs Cross Section Working Group in the period 2014-2016. The main goal of the working group was to present the state-of-the-art of Higgs physics at the LHC, integrating all new results that have appeared in the last few years. The first part compiles the most up-to-date predictions of Higgs boson production cross sections and decay branching ratios, parton distribution functions, and off-shell Higgs boson production and interference effects. The second part discusses the recent progress in Higgs effective field theory predictions, followed by the third part on pseudo-observables, simplified template cross section and fiducial cross section measurements, which give the baseline framework for Higgs boson property measurements. The fourth part deals with the beyond the Standard Model predictions of various benchmark scenarios of Minimal Supersymmetric Standard Model, extended scalar sector, Next-to-Minimal Supersymmetric Standard Model and exotic Higgs boson decays. This report follows three previous working-group reports: Handbook of LHC Higgs Cross Sections: 1. Inclusive Observables (CERN-2011-002), Handbook of LHC Higgs Cross Sections: 2. Differential Distributions (CERN-2012-002), and Handbook of LHC Higgs Cross Sections: 3. Higgs properties (CERN-2013-004). The current report serves as the baseline reference for Higgs physics in LHC Run 2 and beyond., Comment: 869 pages, 295 figures, 248 tables and 1645 citations. Working Group web page: https://twiki.cern.ch/twiki/bin/view/LHCPhysics/LHCHXSWG

We consider the Standard Model extended by a heavy scalar singlet in different regions of parameter space and construct the appropriate low-energy effective field theories up to first nontrivial order. This top-down exercise in effective field theory is meant primarily to illustrate with a simple example the systematics of the linear and nonlinear electroweak effective Lagrangians and to clarify the relation between them. We discuss power-counting aspects and the transition between both effective theories on the basis of the model, confirming in all cases the rules and procedures derived in previous works from a bottom-up approach., Comment: 29 pages, 5 figures

In a recent paper [1] a master formula has been presented for the power counting of a general effective field theory. We first show that this master formula follows immediately from the concept of chiral dimensions (loop counting), together with standard dimensional analysis. Subsequently, [1] has disputed the relevance of chiral counting for chiral Lagrangians, and in particular for the electroweak chiral Lagrangian including a light Higgs boson. As an alternative, a power counting based on `primary dimensions' has been proposed. The difficulties encountered with this scheme led the authors to suggest that even the leading order of the electroweak chiral Lagrangian could not be clearly defined. Here we demonstrate that the concept of primary dimensions is irrelevant for the organization of chiral Lagrangians. We re-emphasize that the correct counting is based on chiral dimensions, or the counting of loop orders, and show how the problems encountered in [1] are resolved., Comment: 15 pages, 1 figure

In a recent paper we showed that the electroweak chiral Lagrangian at leading order is equivalent to the conventional $\kappa$ formalism used by ATLAS and CMS to test Higgs anomalous couplings. Here we apply this fact to fit the latest Higgs data. The new aspect of our analysis is a systematic interpretation of the fit parameters within an EFT. Concentrating on the processes of Higgs production and decay that have been measured so far, six parameters turn out to be relevant: $c_V$, $c_t$, $c_b$, $c_\tau$, $c_{\gamma\gamma}$, $c_{gg}$. A global Bayesian fit is then performed with the result: $c_{V} = 0.98 \pm 0.09$, $c_{t} = 1.34 \pm 0.19$, $c_{b} = 0.78 \pm 0.18$, $c_{\tau} = 0.92 \pm 0.14$, $c_{\gamma\gamma} = -0.24 \pm 0.37$, $c_{gg} = -0.30 \pm 0.17$. Additionally, we show how this leading-order parametrization can be generalized to next-to-leading order, thus improving the $\kappa$ formalism systematically. The differences with a linear EFT analysis including operators of dimension six are also discussed. One of the main conclusions of our analysis is that since the conventional $\kappa$ formalism can be properly justified within a QFT framework, it should continue to play a central role in analyzing and interpreting Higgs data., Comment: 23 pages, 22 figures; extended discussion of fitting procedure

We propose a parametrization of anomalous Higgs-boson couplings that is both systematic and practical. It is based on the electroweak chiral Lagrangian, including a light Higgs boson, as the effective field theory (EFT) at the electroweak scale $v$. This is the appropriate framework for the case of sizeable deviations in the Higgs couplings of order $10\%$ from the Standard Model, considered to be parametrically larger than new-physics effects in the sector of electroweak gauge interactions. The role of power counting in identifying the relevant parameters is emphasized. The three relevant scales, $v$, the scale of new Higgs dynamics $f$, and the cut-off $\Lambda=4\pi f$, admit expansions in $\xi=v^2/f^2$ and $f^2/\Lambda^2$. The former corresponds to an organization of operators by their canonical dimension, the latter by their loop order or chiral dimension. In full generality the EFT is thus organized as a double expansion. However, as long as $\xi\gg 1/16\pi^2$ the EFT systematics is closer to the chiral counting. The leading effects in the consistent approximation provided by the EFT, relevant for the presently most important processes of Higgs production and decay, are given by a few (typically six) couplings. These parameters allow us to describe the properties of the Higgs boson in a general and systematic way, and with a precision adequate for the measurements to be performed at the LHC. The framework can be systematically extended to include loop corrections and higher-order terms in the EFT., Comment: 7 pages, no figures; typos corrected; references added

We analyze new physics contributions to $e^+e^-\to W^+W^-$ at the TeV energy scale, employing an effective field theory framework. A complete basis of next-to-leading order operators in the standard model effective Lagrangian is used, both for the nonlinear and the linear realization of the electroweak sector. The elimination of redundant operators via equations-of-motion constraints is discussed in detail. Polarized cross sections for $e^+e^-\to W^+W^-$ (on-shell) are computed and the corrections to the standard model results are given in an expansion for large $s/M^2_W$. The dominant relative corrections grow with $s$ and can be fully expressed in terms of modified gauge-fermion couplings. These corrections are interpreted in the context of the Goldstone boson equivalence theorem. Explicit new physics models are considered to illustrate the generation and the potential size of the coefficients in the effective Lagrangian. Brief comments are made on the production of $W^+W^-$ pairs at the LHC., Comment: 32 pages, 5 figures

We develop a systematic framework for exclusive rare B decays of the type B -> K(*)l+l- at large dilepton invariant mass q^2. It is based on an operator product expansion (OPE) for the required matrix elements of the nonleptonic weak Hamiltonian in this kinematic regime. Our treatment differs from previous work by a simplified operator basis, the explicit calculation of matrix elements of subleading operators, and by a quantitative estimate of duality violation. The latter point is discussed in detail, including the connection with the existence of an OPE and an illustration within a simple toy model., Comment: 34 pages, 7 figures

We show that a combined analysis of $B\to K\nu\bar\nu$ and $B\to Kl^+l^-$ allows for new physics tests practically free of form factor uncertainties. Residual theory errors are at the level of several percent. Our study underlines the excellent motivation for measuring these modes at a Super Flavour Factory., Comment: 26 pages, 2 figures

The integrated branching fraction of the process $B\to X_s l^+l^-$ is dominated by resonance background from narrow charmonium states, such as $B\to X_s\psi\to X_s l^+l^-$, which exceeds the non-resonant charm-loop contribution by two orders of magnitude. The origin of this fact is discussed in view of the general expectation of quark-hadron duality. The situation in $B\to X_s l^+l^-$ is contrasted with charm-penguin amplitudes in two-body hadronic B decays of the type $B\to\pi\pi$, for which it is demonstrated that resonance effects and the potentially non-perturbative $c\bar c$ threshold region do not invalidate the standard picture of QCD factorization. This holds irrespective of whether the charm quark is treated as a light or a heavy quark., Comment: 20 pages, 4 figures

A short overview of theoretical methods for B physics at hadron colliders is presented. The main emphasis is on the theory of two-body hadronic B decays, which provide a rich field of investigation in particular for the Tevatron and the LHC. The subject holds both interesting theoretical challenges as well as many opportunities for flavor studies and new physics tests. A brief review of the current status and recent developments is given. A few additional topics in B physics are also mentioned., Comment: Invited talk at the Hadron Collider Physics Symposium (HCP2008), Galena, Illinois, USA, May 27-31, 2008; 10 pages, LaTeX, 8 ps figures

With the advent of the LHC, we will be able to probe New Physics (NP) up to energy scales almost one order of magnitude larger than it has been possible with present accelerator facilities. While direct detection of new particles will be the main avenue to establish the presence of NP at the LHC, indirect searches will provide precious complementary information, since most probably it will not be possible to measure the full spectrum of new particles and their couplings through direct production. In particular, precision measurements and computations in the realm of flavour physics are expected to play a key role in constraining the unknown parameters of the Lagrangian of any NP model emerging from direct searches at the LHC. The aim of Working Group 2 was twofold: on one hand, to provide a coherent, up-to-date picture of the status of flavour physics before the start of the LHC; on the other hand, to initiate activities on the path towards integrating information on NP from high-pT and flavour data., Comment: Report of Working Group 2 of the CERN Workshop ``Flavour in the era of the LHC'', Geneva, Switzerland, November 2005 -- March 2007

We show that the factorization formula for non-leptonic B decays to two light flavor non-singlet mesons derived by Bauer et al. in the context of soft-collinear effective theory is equivalent to the corresponding formula in the QCD factorization approach. The apparent numerical differences in the analysis of B->pi+pi data performed by these authors, as compared to previous QCD factorization analyses, can largely be attributed to the neglect of known perturbative and power corrections., Comment: Comment on hep-ph/0401188 by Bauer, Pirjol, Rothstein and Stewart; 4 pages

We compute next-to-leading order QCD corrections to the CP asymmetry a_{fs} = Im(Gamma_{12}/M_{12}) in flavour-specific B_{d,s} decays such as B_d->X l nu or B_s->D^-_s pi^+. The corrections reduce the uncertainties associated with the choice of the renormalization scheme for the quark masses significantly. In the Standard Model we predict a^d_{fs} = -(5.0 +- 1.1)*10^{-4}. As a by-product we also obtain the width difference in the B_d system at next-to-leading order in QCD., Comment: 12 pages, 3 figures; error in NLO calculation corrected

This report contains the results of the Workshop on the CKM Unitarity Triangle, held at CERN on 13-16 February 2002 to study the determination of the CKM matrix from the available data of K, D, and B physics. This is a coherent document with chapters covering the determination of CKM elements from tree level decays and K and B meson mixing and the global fits of the unitarity triangle parameters. The impact of future measurements is also discussed., Comment: 284 pages, Proceedings of the First Workshop on the CKM Unitarity Triangle, CERN 13-16 February 2002, to appear as CERN Yellow Report. Editors - M. Battaglia, A.J. Buras, P. Gambino, A. Stocchi

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 literature with lattice QCD we obtain $\tau(B^+)/\tau(B^0_d)=1.053\pm 0.027\pm 0.017$, where the effects of unquenching and $1/m_b$ corrections are not yet included. The lifetime difference of heavy baryons $\Xi^0_b$ and $\Xi^-_b$ is also briefly discussed., Comment: 20 pages, LaTeX

We study opportunities for future high-precision experiments in kaon physics using a high-intensity proton driver, which could be part of the front-end of a muon storage ring complex. We discuss in particular the rare decays $K_L\to\pi^0\nu\bar\nu$, $K^+\to\pi^+\nu\bar\nu$, $K_L\to\pi^0e^+e^-$, and lepton-flavour violating modes such as $K_L\to\mu e$ and $K\to\pi\mu e$. The outstanding physics potential and long-term interest of these modes is emphasized. We review status and prospects of current and planned experiments for the processes under consideration, and indicate possible improvements and strategies towards achieving the necessary higher sensitivity. Finally, we outline the machine requirements needed to perform these high-precision kaon experiments in the context of a muon storage ring facility., Comment: 26 pages, 12 figures; report of the kaon physics working group for the ECFA studies on neutrino factory and muon storage rings at CERN, G. Buchalla (convener); references updated

In the heavy-quark limit, the hadronic matrix elements entering nonleptonic $B$-meson decays into two light mesons can be calculated from first principles including ``nonfactorizable'' strong-interaction corrections. The $B\to\pi K,\pi\pi$ decay amplitudes are computed including electroweak penguin contributions, SU(3) violation in the light-cone distribution amplitudes, and an estimate of power corrections from chirally-enhanced terms and annihilation graphs. The results are then used to reduce the theoretical uncertainties in determinations of the weak phases $\gamma$ and $\alpha$. In that way, new constraints in the $(\bar\rho,\bar\eta)$ plane are derived. Predictions for the $B\to\pi K, \pi\pi$ branching ratios and CP asymmetries are also presented. A good global fit to the (in part preliminary) experimental data on the branching fractions is obtained without taking recourse to phenomenological models., Comment: 81 pages, LaTeX

We examine some consequences of the QCD factorization approach to non-leptonic B decays into $\pi K$ and $\pi \pi$ final states, including a set of enhanced power corrections. Among the robust predictions of the approach we find small strong-interaction phases (with one notable exception) and a pattern of CP-averaged branching fractions, which in some cases differ significantly from the current central values reported by the CLEO Collaboration., Comment: 4 pages, LaTeX, Contribution to ICHEP2000, July 27 - August 2, Osaka, Japan, to appear in the Proceedings

The rare decays $B\to K^{(*)}\ell^+\ell^-$, $B\to K^{(*)}\nu\bar\nu$ and $B_s\to\mu^+\mu^-$ are analyzed in a generic scenario where New Physics effects enter predominantly via $Z$ penguin contributions. We show that this possibility is well motivated on theoretical grounds, as the $\bar sbZ$ vertex is particularly susceptible to non-standard dynamics. In addition, such a framework is also interesting phenomenologically since the $\bar sbZ$ coupling is rather poorly constrained by present data. The characteristic features of this scenario for the relevant decay rates and distributions are investigated. We emphasize that both sign and magnitude of the forward-backward asymmetry of the decay leptons in $\bar B\to \bar K^*\ell^+\ell^-$, ${\cal A}^{(\bar B)}_{FB}$, carry sensitive information on New Physics. The observable ${\cal A}^{(\bar B)}_{FB}+{\cal A}^{(B)}_{FB}$ is proposed as a useful probe of non-standard CP violation in $\bar sbZ$ couplings., Comment: Minor modifications; version to appear in Phys. Rev. D

We provide a rigorous basis for factorization for a large class of non-leptonic two-body $B$-meson decays in the heavy-quark limit. The factorization formula incorporates elements of the naive factorization approach and the hard-scattering approach, but allows us to compute systematically radiative (``non-factorizable'') corrections to naive factorization for decays such as $B\to D\pi$ and $B\to \pi \pi$. We discuss the factorization formula for a general final state from a general point of view. We then consider factorization for decays into heavy-light final states (such as $B\to D\pi$) in more detail, including a proof of the factorization formula at two-loop order. Explicit results for the leading QCD corrections to factorization are presented and compared to existing measurements of branching fractions and final-state interaction phases., Comment: 112 pages, LaTeX, 30 figures

We review the prospects for B decay studies at the LHC., Comment: 112 pages, ca.90 partially bitmapped PS figures, PS with high resolution figures available from http://home.cern.ch/~pball/master.ps.gz, P. Ball, R. Fleischer, G.F. Tartarelli, P. Vikas, G. Wilkinson (convenors)

We show that, in the heavy quark limit, the hadronic matrix elements that enter $B$ meson decays into two light mesons can be computed from first principles, including `non-factorizable' strong interaction corrections, and expressed in terms of form factors and meson light-cone distribution amplitudes. The conventional factorization result follows in the limit when both power corrections in $1/m_b$ and radiative corrections in $\alpha_s$ are neglected. We compute the order-$\alpha_s$ corrections to the decays $B_d\to\pi^+\pi^-$, $B_d\to\pi^0\pi^0$ and $B^+\to\pi^+\pi^0$ in the heavy quark limit and briefly discuss the phenomenological implications for the branching ratios, strong phases and CP violation., Comment: 6 pages, 1 figure

We compute the QCD corrections to the decay rate difference in the $B_s-\bar B_s$ system, $\Delta\Gamma_{B_s}$, in the next-to-leading logarithmic approximation using the heavy quark expansion approach. Going beyond leading order in QCD is essential to obtain a proper matching of the Wilson coefficients to the matrix elements of local operators from lattice gauge theory. The lifetime difference is reduced considerably at next-to-leading order. We find $(\Delta\Gamma/\Gamma)_{B_s}=(f_{B_s}/210 MeV)^2 [0.006 B(m_b)+0.150 B_S(m_b)-0.063]$ in terms of the bag parameters $B, B_S$ in the NDR scheme. As a further application of our analysis we also derive the next-to-leading order result for the mixing-induced CP asymmetry in inclusive $b\to u\bar ud$ decays, which measures $\sin 2\alpha$., Comment: 14 pages, LaTeX, 1 figure; minor modifications of the text, improved discussion of eq. (35), all results unchanged

A brief review of the theoretical status of CP violation in decays of neutral kaons is presented. We focus on three important topics: $\varepsilon$, $\varepsilon'/\varepsilon$ and $K_L\to\pi^0\nu\bar\nu$., Comment: 5 pages, Latex; Invited Talk presented at the Symposium on Flavor-Changing Neutral Currents, Santa Monica, California, February 19-21, 1997; to appear in the proceedings

We calculate nonperturbative ${\cal O}(\Lambda^2_{QCD}/m^2_c)$ corrections to the dilepton invariant mass spectrum and the forward-backward charge asymmetry in $B\to X_se^+e^-$ decay using a heavy quark expansion approach. The method has recently been used to estimate long-distance effects in $B\to X_s\gamma$. We generalize this analysis to the case of nonvanishing photon invariant mass, $q^2\not= 0$, relevant for the rare decay mode $B\to X_se^+e^-$. In the phenomenologically interesting $q^2$ region away from the $c\bar c$ resonances, the heavy quark expansion approach should provide a reasonable description of possible nonperturbative corrections. In particular this picture is preferable to the model-dependent approach relying on the tails of Breit-Wigner resonances, which has been employed so far in the literature to account for these effects. We find that the ${\cal O}(\Lambda^2_{QCD}/m^2_c)$ corrections to the dilepton invariant mass spectrum and to the forward-backward asymmetry in $B\to X_se^+e^-$ amount to several percent at most for $q^2/m^2_b < 0.3$ and $q^2/m^2_b > 0.6$. The ${\cal O}(\Lambda^2_{QCD}/m^2_c)$ correction to the $B\to X_s\gamma$ decay rate is also computed and found to be +3%, which agrees in magnitude with previous calculations. Finally, we comment on long-distance effects in $B\to X_s\nu\bar\nu$, which in this case are extremely suppressed due to the absence of virtual photon contributions., Comment: Latex, 15 pages, 3 figures (included)

We use the heavy quark expansion to investigate the width difference $\Delta\Gamma_{B_s}$ between the $B_s$ mass eigenstates. The corrections of ${\cal O}(\Lambda_{QCD}/m_b)$ and ${\cal O}(m_s/m_b)$ to the leading order expression in the operator product expansion are derived and estimated to yield a sizable reduction of the leading result for $\Delta\Gamma_{B_s}$ by typically $30\%$. For completeness we also quantify small effects due to penguin operators and CKM suppressed contributions. Based on our results we discuss the prediction for $(\Delta\Gamma/\Gamma)_{B_s}$ with particular emphasis on theoretical uncertainties. We find $(\Delta\Gamma/\Gamma)_{B_s}=0.16^{+0.11}_{-0.09}$, where the large error is dominated by the uncertainty in hadronic matrix elements. An accuracy of about $10\%$ in $(\Delta\Gamma/\Gamma)_{B_s}$ should be within reach, assuming continuing progress in lattice calculations. In addition we address phenomenological issues and implications of a $\Delta\Gamma_{B_s}$ measurement for constraints on $\Delta M_{B_s}$ and CKM parameters. We further consider in some detail the lifetime ratio $\tau(B_s)/\tau(B_d)$ and estimate that, most likely, $|\tau(B_s)/\tau(B_d)-1|<1\%$., Comment: 24 pages, LaTeX, 1 figure as uudecoded file

We investigate the total inclusive decay rate of the (ground state) $B_c$ meson within the framework of an operator product expansion in inverse powers of the heavy quark masses and subsequent matching onto nonrelativistic QCD. The expansion is organized as a series in the strong coupling and in powers of the heavy quark velocities in the $B_c$, reflecting the nonrelativistic nature of a heavy-heavy bound state. In this aspect the character of the expansion differs from the more familiar case of heavy-light mesons. The framework incorporates systematically corrections to the leading $b$- and $c$-quark decays due to binding effects, as well as contributions from weak annihilation and Pauli interference. Based on this approach we find for the $B_c$ meson lifetime $\tau_{B_c}=(0.4 - 0.7)\,$ps, the dominant mechanism being the decay of the charm constituent., Comment: 18 pages, revtex, 2 figures as uudecoded file

In strong dynamical schemes for electroweak symmetry breaking the third generation must be treated in a special manner, owing to the heavy top quark. This potentially leads to new flavor physics involving the members of the third generation in concert with the adjoining generations, with potential novel effects in beauty and charm physics. We give a general discussion and formulation of this kind of physics, abstracted largely from Topcolor models which we elaborate in detail. We identify sensitive channels for such new physics accessible to current and future experiments., Comment: LaTeX, 38 pages, 4 figures. References added; figures were fixed

We generalize the existing analyses of the parity violating muon polarization asymmetry $\Delta_{LR}$ in $K^+\to\pi^+\mu^+\mu^-$ beyond the leading logarithmic approximation. The inclusion of next--to--leading QCD corrections reduces the residual dependence on the renormalization scales, which is quite pronounced in the leading order. This leads to a considerably improved accuracy in the perturbative calculation of the short distance dominated quantity $\Delta_{LR}$. Accordingly this will also allow to obtain better constraints on the Wolfenstein parameter $\varrho$ from future measurements of $\Delta_{LR}$. For $-0.25\leq \varrho \leq 0.25$, $V_{cb}=0.040\pm 0.004$ and $m_t=(170\pm 20)GeV$ we find $3.0\cdot 10^{-3}\leq |\Delta_{LR}|\leq 9.6\cdot 10^{-3}$., Comment: 9 pages, MPI-PhT/94-43, TUM-T31-65/94

We analyze the branching ratio for the FCNC mode $K^+\to\pi^+\nu\bar\nu$\ in the standard model with QCD effects taken into account consistently to next-to-leading order. This involves a two-loop renormalization group analysis for the charm contribution, presented in this paper, and the calculation of $O(\alpha_s)$ corrections to all orders in $m_t/M_W$ for the top-quark case that we have described elsewhere. The inclusion of next-to-leading corrections reduces considerably the theoretical uncertainty due to the choice of the renormalization scales, inherent in any calculation to finite order in perturbation theory. For $K^+\to\pi^+\nu\bar\nu$\ this point has not been discussed previously. In particular, the related uncertainty in the determination of $|V_{td}|$ from $B(K^+\to\pi^+\nu\bar\nu)$ is reduced from $\sim 30\%$ to $\sim 7\%$ for typical values of the parameters. Simultaneously also the dependence of $B(K^+\to\pi^+\nu\bar\nu)$ on the choice of $m_c$ is considerably reduced. We also give the next-to-leading order expression for the short-distance part of $K_L\to\mu^+\mu^-$. Impacts of our calculations on the determination of the unitarity triangle are presented., Comment: 40, MPI-Ph/93-44