T. N. Pham

CP-violating dipole form factors in e+e− → t̄t

Abstract If the neutral Higgs sector in extensions of the standard electroweak theory (SM) is CP-noninvariant, then sizeable CP-violating effects can be induced in flavour-diagonal reactions involving heavy flavours, especially the t quark. We show this by calculating the dominant CP-violating contributions to e + e − → t t in two-Higgs doublet extensions of the SM. These effects can be searched for at future e+e− supercolliders by measuring appropriate CP-odd momentum correlations for t t events.

{CP} Violation Induced by Penguin Diagrams and the Neutron Electric Dipole Moment

Abstract In the Kobayashi-Maskawa model, penguin diagrams can induce CP violating phases in matrix elements of the type n→Λ. This produce a neutron electric dipole moment through subsequent parity violating radiative weak decay Λ→nγ. We can expect ( D n e )≅10 −30 cm , three to four orders of magnitude bigger than the mechanism based on the transition quark electric dipole moment. The reason is essentially that the GIM cancellation comes in the Penguin case from ( α s π ) log m 2 t m 2 c abd not from π −2 (m 2 t −m 2 c ) M 2 W as for the transition quark electric dipole moment.

FCNC

We study the flavor changing neutral current B{sub s}{yields}{phi}{gamma}, {phi}{nu}{nu} and {lambda}{sub b}{yields}{lambda}{gamma}, {lambda}{nu}{nu} transitions in the standard model and in a scenario with a single universal extra dimension. In particular, we focus on the present knowledge of the hadronic uncertainties and on possible improvements. We discuss how the measurements of these modes can be used to constrain the new parameter involved in the extra-dimensional scenario, the radius R of the extra dimension, completing the information available from B-factories. The rates of these b{yields}s induced decays are within the reach of new experiments, such as LHCb.

B_s

Using the non-linear effective lagrangian technique, we show explicitly that only derivative coupling is allowed for the K - π, K → 2π and K → 3π transitions induced by the ΔS = 1 Penguin operator of SVZ in agreement with chiral symmetry requirements. From a derivative coupling (3, 3) mass term and the SU(3) breaking effect for ƒK/ƒπ, we estimate the strength of the Penguin interactions and find it too small to account for the ΔI = 12 amplitude.

and

Abstract Decay rate of τ into 3π and 5π is calculated using current algebra and PCAC. Assuming universality for ordinary leptons and τ, satisfactory agreement with experimental data is obtained with Г tot ( A 1 ) ≈ 300−400 MeV . The branching ratio for π → 5π + ν is found to be 1%.

Lambda_b

Abstract In the Kobayashi-Maskawa model, the neutron electric dipole moment is a high-order effect in the electroweak interactions. We need a perturbative calculation in two steps: (1) generation of CP -violatingcouplings at the quark level through heavy quark loops, and (2) a perturbative expansion by nearest intermediate states at the bound state level. We examine both aspects for a mechanism proposed by Morel and by Cox et al. where CP violation comes from transition quark electric dipole moments. We retain the lowest lying baryon intermediate states1/2 + (56,0 + )and 1/2 − (70,1 − ). For this mechanism we get at most D n/ e ≈10 −34 cm.

transitions: Standard model versus a single universal extra dimension scenario

Abstract We re-analyse the ΔI = 1 2 rule in K nonleptonic decays. By considering the πK transition, keeping the constraints of chiral SU(3) × SU(3) symmetry and using a Cottingham type of analysis, we find that heavy meson states can account for the ΔI = 1 2 rule. Strong bounds on mixing angles ensue as well as interesting implications for CP violation in K O decay and for decay modes of B mesons.

Non-linear effective lagrangian treatment of “Penguin” interaction

Abstract We estimate the branching ratio for K + → π + H for a light Higgs. We find a very small branching ratio so that a light Higgs is not excluded by this process. Differences with previous estimations and several sources of uncertainty are explained.

Decay rate of τ into odd number of pions

Abstract Phenomenological analysis of the two-pion spectrum and the angular distribution in ψ ′ → ψ + 2 π decays is given. The absence of a sizeable cos 2 θ term in the angular distribution and the large enhancement of 2π events at the high end of the spectrum can only be explained by a zero in the matrix element (Adler zero).

Intermediate States in the Calculation of the Neutron Electric Dipole Moment

Abstract We compute the high-energy e + e − → π 0 γ , Z 0 → π 0 γ and similar processes using the modified PCAC equation due to Adler- Bell-Jackiw anomaly. Unlike the case with real photons, e.g. π 0 → 2 γ decay, we find that, for large gauge boson or virtual photon masses, the quark-parton contribution to the axial vector current divergence as given by the triangle graphs does not vanish and cancels the anomaly terms, leaving the amplitudes strongly suppressed.