1,721,121 research outputs found
LEADING NONLOGARITHMIC CONTRIBUTION TO THE ELECTROPENGUIN DIAGRAM AND PHENOMENOLOGY OF KAON DECAYS
No full textThe leading non-logarithmic contribution which arises in the real part of the Wilson coefficient for the electropenguing operator is re-analized within the four-flavor effective Hamiltonian. The ratio Gamma(K+--->pi+ e+ e-)/Gamma(K+--->pi0 e+ nu_e), the K_L--->pi0 e+ e- decay rate and the Delta I=1/2 rule in the non-leptonic kaon decays are reconsidered by taking into account both the leading non-logarithmic contribution and the strong corrections in log(M_W/mu)^2 up to the next-to-leading order. Their dependence on the QCD parameters is studied and we argue that the inclusion of the strong corrections of order log(m_g/mu)^2 cannot be neglected
Soft SUSY breaking grand unification: Leptons versus quarks on the flavor playground
No full textWe systematically analyze the correlations between the various leptonic and hadronic flavor
violating processes arising in SUSY Grand Unified Theories. Using the GUT-symmetric
relations between the soft SUSY breaking parameters, we assess the impact of hadronic and
leptonic flavor observables on the SUSY sources of flavor violation
Lifetime differences and CP violation parameters of neutral B mesons at the next-to-leading order in QCD
No full textWe compute the next-to-leading order QCD corrections to the off-diagonal elements of the decay-width matrix Gamma entering the neutral B-meson oscillations. From this calculation the width differences DeltaGamma and the CP violation parameters (q/p) of B-d and B-s mesons are estimated, including the complete O(alpha(s)) QCD corrections and the 1/m(b) contributions. For the width difference DeltaGamma(s) we agree with previous results. By using the lattice determinations of the relevant hadronic matrix elements we obtain the theoretical predictions DeltaGamma(d)/Gamma(d) = (2.42 +/- 0.59) x 10(-3) and DeltaGamma(s)/Gamma(s) = (7.4 +/- 2.4) x 10(-2). For the CP violation parameters, we find (q/p)(d)\ - 1 = (2.96 +/- 0.67) x 10(-4) and (q/p)(s) - 1 = - (1.28 +/- 0.27) x 10(-5). These predictions are compatible with the experimental measurements which, however, suffer at present from large uncertainties
Next-to-leading order QCD corrections to Delta F=2 effective Hamiltonians
No full textThe most general QCD next-to-leading anomalous-dimension matrix of all four-fermion dimension-six Delta F = 2 operators is computed. The results of this calculation can be used in many phenomenological applications, among which the most important are those related to theoretical predictions of K-0-(K) over bar(0) and B-0-(B) over bar(0) mixing in several extensions of the Standard Model (supersymmetry, left-right symmetric models, multi-Higgs models, etc.), to estimates the B-s(0)-(B) over bar(s)(0) width difference, and to the calculation of the O(1/m(b)(3)) corrections for inclusive b-hadron decay rates
The ΔS = 1 effective hamiltonian including next-to-leading order QCD and QED corrections
No full textIn this paper we present a calculation of the ΔS = 1 effective weak hamiltonian including next-to-leading order QCD and QED corrections. At a scale μ of the order of a few GeV, the Wilson coefficients of the operators are given in terms of the renormalization group evolution matrix and of the coefficients computed at a large scale ∼ MW. The expression of the evolution matrix is derived from the two-loop anomalous dimension matrix which governs the mixing of the relevant current-current and penguin operators, renormalized in some given regularization scheme. We have computed the anomalous dimension matrix up to and including order αs2 and αeαs in two different renormalization schemes, NDR and HV, with consistent results. We give many details on the calculation of the anomalous dimension matrix at two loops, on the determination of the Wilson coefficients at the scale MW and of their evolution from MW to μ. We also discuss the dependence of the Wilson coefficients/operators on the regularization scheme.SCOPUS: ar.jinfo:eu-repo/semantics/publishe
Next-to-leading order QCD corrections to spectator effects in lifetimes of beauty hadrons
No full textTheoretical predictions of beauty hadron lifetimes, based on the heavy quark expansion up to and including order 1/m(b)(2) do not to reproduce the experimental measurements of the lifetime ratios tau (B+) /tau (B-d) and tau (Lambda(b)) /tau (B-d). Large corrections to these predictions come from phasespace enhanced 1/m(b)(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/m(b)(3)). We find that these corrections improve the agreement with the experimental data. The O(1/m(b)(3)) lifetime ratio of charged to neutral B-mesons, tau (B+) /tau (B-d), turns out to be in very good agreement with the corresponding measurement, whereas for tau (B-s) /tau (B-d) and tau (Lambda(b)) /tau (B-d) there is a residual difference at the 1sigma level. We discuss, however, why the theoretical predictions are less accurate in the latter cases
Two-body non-leptonic decays on the lattice
No full textWe show that, under reasonable hypotheses, it is possible to study two-body non-leptonic weak decays in numerical simulations of lattice QCD. By assuming that final-state interactions are dominated by the nearby resonances and that the couplings of the resonances to the final particles are smooth functions of the external momenta, it is possible indeed to overcome the difficulties imposed by the Maiani-Testa no-go theorem and to extract the weak decay amplitudes, including their phases. Under the same assumptions, results can be obtained also for time-like form factors and quasi-elastic processes.We show that, under reasonable hypotheses, it is possible to study two-body non-leptonic weak decays in numerical simulations of lattice QCD. By assuming that final-state interactions are dominated by the nearby resonances and that the couplings of the resonances to the final particles are smooth functions of the external momenta, it is possible indeed to overcome the difficulties imposed by the Maiani-Testa no-go theorem and to extract the weak decay amplitudes, including their phases. Under the same assumptions, results can be obtained also for time-like form factors and quasi-elastic processes
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