Effective field theory analysis of new physics in e + e −→W + W − at a linear collider

The effective Lagrangian with scalar and vector resonances that might result from new strong physics beyond the SM is formulated and studied. In particular, the scalar resonance representing the recently discovered 125-GeV boson is complemented with the SU(2) _L+R triplet of hypothetical vector resonances. Motivated by experimental and theoretical considerations, the vector resonance is allowed to couple directly to the third quark generation only. The coupling is chiral-dependent and the interaction of the right top quark can differ from that of the right bottom quark. To estimate the applicability range of the effective Lagrangian the unitarity of the gauge boson scattering amplitudes is analyzed. The experimental fits and limits on the free parameters of the vector resonance triplet are investigated.     

Theory of B→K(?)l+l? decays at high q2: OPE and quark–hadron duality

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.     

CP-violation in B → π+π- and the unitarity triangle

We analyze the extraction of weak phases from CP-violation in B → π⁺π^- decays. We propose to determine the unitarity triangle by combining the information on mixing-induced CP-violation in B → π⁺π^-, S, with the precision observable sin2β obtained from the CP-asymmetry in B → ψK_S. It is then possible to write down exact analytical expressions for and as simple functions of the observables S and sin2β and of the penguin parameters r and ϕ. As an application clean lower bounds on and can be derived as functions of S and sin2β, essentially without hadronic uncertainty. Computing r and ϕ within QCD factorization yields precise determinations of and since the dependence on r and ϕ is rather weak. It is emphasized that the sensitivity to the phase ϕ enters only at second order and is extremely small for moderate values of this phase, predicted in the heavy-quark limit. Transparent analytical formulas are further given and discussed for the parameter C of direct CP-violation in B → π⁺π^-. Predictions and uncertainties for r and ϕ in QCD factorization are examined in detail. It is pointed out that a simultaneous expansion in 1/m_b and 1/N leads to interesting simplifications. At first order infrared divergences are absent, while the most important effects are retained. Independent experimental tests of the factorization framework are briefly discussed. Received: 16 April 2005, Revised: 6 August 2005, Published online: 21 November 2005 PACS: 11.30.Er, 12.15.Hh, 13.25.Hw     

Model independent bound on the unitarity triangle from CP violation in B-->pi(+)pi(-) and B-->psiK(S)

We derive model-independent lower bounds on the CKM parameters (1-rho) and eta as functions of the mixing-induced CP asymmetry S in B-->pi(+)pi(-) and sin(2 beta from B-->psiK(S). The bounds do not depend on specific results of theoretical calculations for the penguin contribution to B-->pi(+)pi(-). They require only the very conservative condition that a hadronic phase, which vanishes in the heavy-quark limit, does not exceed 90 degrees in magnitude. The bounds are effective if -sin(2 beta相似文献   

Penguins with charm and quark–hadron duality

The integrated branching fraction of the process B→X _s l ⁺ l ⁻ is dominated by resonance background from narrow charmonium states, such as B→X _s ψ→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→X _s l ⁺ l ⁻ is contrasted with charm-penguin amplitudes in two-body hadronic B decays of the type B→π π, for which it is demonstrated that resonance effects and the potentially non-perturbative 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.