A simple chiral Lagrangian approach toK→πππ decays andε′+0−

We analyse theK→πππ decays in the framework of a chiral Lagrangian supplemented by the 1/N expansion (N being the number of colors). The measuredK _L →π⁺π⁰π⁺ Dalitz plot is very well reproduced. Contrary to a recent claim, the Li-Wolfenstein relation between the CP impurities associated with theK→πππ(ε′_+0?) and theK→ππ(ε′) decay amplitudes is rather stable against isospin-breaking effects and higher-order (in the chiral expansion) weak operator corrections. We also predict a branching ratio of 2.1 10^?7 for the CP-conservingK _S →π⁺π⁰π⁺ decay.     

Instanton interpolating current for σ-tetraquark

We perform a QCD sum rule analysis for the light scalar meson σ   (f₀(600)$f_0(600)$) with a tetraquark current related to the instanton picture for QCD vacuum. We demonstrate that instanton current, including equal weights of scalar and pseudoscalar diquark–antidiquarks, leads to a strong cancelation between the contributions of high dimension operators in the operator product expansion (OPE). Furthermore, in the case of this current direct instanton contributions do not spoil the sum rules. Our calculation, obtained from the OPE up to dimension 10 operators, gives the mass of σ-meson around 780 MeV.     

Instanton contribution toB→X s γ decay

We study instanton effects onBX _s decay using the heavy quark effective field theory and the operator product expansion. In the dilute gas approximation the effect is negligibly small. This is in contrast to the result of the instanton effect in inclusive semileptonicbu decay but similar to the inclusive hadronic decay. We discuss the similarities and differences of theBX _s decay compared to inclusive hadronic decay and semileptonicB decay.     

439-1439-1439-1transitions: model-independent bounds on invariant form factors

In this note we report on some model-independent bounds involving the transition form factors for Ω_b → Ω_c and Ω_b → Ω _c ^* transitions and the nonperturbative matrix elements of the Ω_b system. The bounds are derived by using operator product expansion (OPE) methods in heavy quark effective theory.     

Renormalization group estimate of the hadronic decay width of the Higgs boson

The total hadronic decay width of the Weinberg-Salam type Higgs boson is estimated in QCD for the Higgs boson mass much larger than the ordinary hadronic mass scale, by use of the operator product expansion and renormalization group equation. We give an explicit formula for the decay width in terms of quark masses including strong interaction corrections up to the next-to-leading order. A numerical analysis of the hadronic decay width of the Higgs boson is made in the six-quark model. The next-to-leading order correction is found to be significant, e.g., 30-20% of the leading term for m_H of oue interest, m_H ? 1 TeV. Application of our scheme to the decay rates of heavy Higgs bosons of other types is also discussed.     

Two-loop QCD corrections to the coefficient functions of the deep inelastic structure functionsF 2 andF L

We present the analytic two-loop perturbative QCD corrections in the leading twist approximation to the coefficient functions of the operator product expansion for the second to tenth moments of the nonsinglet and singlet deep inelastic structure functionsF ₂ andF _L .     

Mass corrections to the tau decay rate

In this note radiative corrections to the total hadronic decay rate of the τ-lepton are studied employing perturbative QCD and the operator product expansion. We calculate quadratic quark mass corrections to the decay rate rationR _τ to the order0(α _s ² m²) and find that they contribute appreciably to the Cabbibo supressed decay modes of the τ-lepton. We also discuss corrections of mass dimensionD=4, where we emphasize the need of a suitable choice of the renormalization scale of the quark and gluon condensates.     

Multiplicity distributions inb →s gluon decays

The final states for the processb→sy have been extensively discussed in the literature. Similarly-detailed analyses for the caseb→s gluon have not been performed. Generally this process is searched for in 2-body decays such as B⁰→K⁺ π ^?. We present simple arguments to suggest that most of the time the quark-level process will give rise to final states with rather high multiplicities. Comments are made about the applicability of these results tob→d gluon and hadronicb→u decays.     

Pentaquark decay is suppressed by chirality conservation

It is shown that, if the pentaquark \(\Theta ^ + = uudd\bar s\) baryon can be represented by the local quark current η_Θ, its decay Θ⁺→nK⁺(pK⁰) is forbidden in the limit of chirality conservation. The Θ⁺ decay width Γ is proportional to \(\alpha _s^2 \left\langle {0\left| {\bar qq} \right|0} \right\rangle ^2\), where \(\left\langle {0\left| {\bar qq} \right|0} \right\rangle ,q = u,d,s\), is quark condensate, and, therefore, is strongly suppressed. The polarization operator of the pentaquark current is calculated using the operator product expansion. The Θ⁺ mass found by the QCD sum rules method is in reasonable agreement with experiment.     

On the Standard Model prediction for \mathcal{B}(B_{s,d} \to \mu^{+} \mu^{-})

The decay B _s →μ ⁺ μ ^? is one of the milestones of the flavor program at the LHC. We reappraise its Standard Model prediction. First, by analyzing the theoretical rate in the light of its main parametric dependence, we highlight the importance of a complete evaluation of higher-order electroweak corrections, at present known only in the large-m _t limit, and leaving sizable dependence on the definition of electroweak parameters. Using insights from a complete calculation of such corrections for $K\to\pi\nu\bar{\nu}We present O(?? _s ) results on the decays of polarized W ^± and Z bosons into massive quark pairs. The NLO QCD corrections to the polarized decay functions are given up to the second order in the quark mass expansion. We find a surprisingly strong dependence of the NLO polarized decay functions on finite quark mass effects even at the relatively large mass scale of the W ^± and Z bosons. As a main application we consider the decay t??b+W ⁺ involving the helicity fractions ?? _mm of the W ⁺ boson followed by the polarized decay $W^{+}(\uparrow)\to q_{1}\bar{q}_{2}$ for which we determine the O(?? _s ) polar angle decay distribution. We also discuss NLO polarization effects in the production/decay process $e^{+}e^{-}\to Z(\uparrow)\to q\bar{q}$ .     

The QCD sum rule for the delta (1232) in the instanton medium

The QCD sum rule for the Δ (1232) is considered in the instanton medium. It is found that the instanton effect improves the chirally odd sum rule significantly. This indicates that the operator product expansion does not converge rapidly in the delta state. The chirally even sum rule of Δ suggests that the “standard” value of the higher dimensional condensate m₀ is much smaller than that derived from the instanton model.     

Joint angular decay distributions in exclusive weak decays of heavy mesons and baryons

We present the results of a comprehensive analysis of the angular decay distributions occurring in the weak exclusive decays of the lowest lying charm and bottom mesons and baryons. We deal with both semileptonic and nonleptonic decays and discuss various decay channels and their subsequent cascade decay chains including lepton mass effects. In the case of baryons we include polarization effects for the parent charm or bottom baryon. We list in table form general formulae which allow one to write down the joint angular decay distributions for the cascade decaysA→B(→b ₁+...+b _n )+C(→c ₁+...+c _n ), for all spin casess _A ≤1/2 ands _B ,s _C ≤3/2 for the prominent decays ofB andC. Two examples involving meson and baryon decays are discussed in detail.     

Analysis of the Heavy Pseudoscalar Mesons with Thermal QCD Sum Rules

In this article, we calculate the contributions of the condensates up to dimension-6, including the one-loop corrections to the quark condensates, in the operator product expansion in a consistent way, and study the masses and decay constants of the heavy pseudoscalar mesons with the thermal QCD sum rules. We reproduce the experimental values of the masses of the D, D _s , B and B _s and obtain the decay constants at zero temperature. Then we study the thermal behaviors of the masses and decay constants, which are useful in explaining the heavy-ion collision experiments.     

J/ψ production at large transverse momentum at hadron colliders

We calculateJ/ψ hadroproduction and emphasize the importance of theJ/ψ signal as a measure ofb \(\bar b\) production via the decayB→ψX and of the gluon structure function at lowx via χ hadroproduction followed by χ→ψγ decay. We compare with UA1 data and data at ISR energies and make predictions for ψ production at TEVATRON energies.     

Geometry of the quantum complex projective spaceCP q (N)

We study the constraints from theb→sγ decay in the parameter space of effective supergravities from orbifold string theory and with minimal supesymmetric particle content. Both the general dilaton-dominated universal scenario as well as a non-universal scenario for the soft terms are investigated. It is found that the recently reported CLEO upper and lower bounds constrain the parameter space of the models under scrutiny. In particular we find constraints on the values of the parameter tanβ and the gluino masses. In this class of string scenarios the negative sign of the Higgs mixing parameterμ, is phenomenologically preferred.     

Phenomenology of Σ+→pℓ+ℓ− and the structure of the weak non-leptonic Hamiltonian

The problem of the radiative non-leptonic weak baryon decays is reviewed in light of the new experimental findings. With the aim of exploring the structure of the weak non-leptonic Hamiltonian, we present a detailed phenomenological analysis of Σ⁺→p?⁺?^? transitions. Lower and upper limits for rates derivable with standard physics are determined as Γ(Σ⁺→pe ⁺ e ^?)/Σ⁺→pγ)≧7.2×10^?3 and 1/1210? Γ(Σ⁺→pe ⁺ e ⁺)/Γ(Σ⁺→pe ⁺ e ^?)?1/120. From existing data on Σ⁺→pe ⁺ e ^? we obtain limits on the values of the charge radius form factors |c ₁/b ₁|?5;|c ₂/b ₁|? 10, where the magnetic form factor is given by the Σ⁺→dγ, decay asb ₁(0)= 6.9±0.9 MeV. The short distance contribution of the QCD corrected single quarks→dλ transition is shown not to play a dominant role in these decays.     

Improved limits on the mass of the tau neutrino

Several methods to determine (or set an upper bound on) the mass of the tau neutrino are described. The decay spectrum of \(\tau \to e\bar \nu _e \nu _\tau \) near the high center-of-mass electron-energy end is particularly sensitive to the tau-neutrino mass. It is shown that an upper bound of 20 MeV or lower may be feasible. In addition, improved limits on the mass and mixing angle of a heavy component of the tau-neutrino may be readily obtained. We also discuss the purely leptonic decays of theD andF mesons, and show how measurements of the ratiosB(D→τν_τ/B(D→μν_μ,B(F→τν_τ/B(D→μν_μ can be sensitive to tau-neutrino masses of 30 MeV or greater.     

Inclusive semileptonicB decays in QCD including lepton mass effects

Starting from an operator product expansion in the heavy quark effective theory up to order 1/m _b ² we calculate the inclusive semileptonic decays of unpolarized bottom hadrons including lepton mass effects. We calculate the differential decay spectra d/(dE ), and the total decay rate forB meson decays to final states containing a lepton.Supported by the Graduiertenkolleg Teilchenphysik, Universität Mainz