arXiv subjects

J. Pestieau

Publications and source records attributed to J. Pestieau.

27 records · Page 2Linked to original sources

arXiv1998

Hadronic Phases and Isospin Amplitudes in $D(B) \to ππ$ and $D(B) \to K \bar K$ Decays

Hadronic phase in $ππ$ and $K \bar K$ channels are calculated a la Regge. At the D mass one finds $δ_{ππ} \approx π/3$ and $δ_{K \bar K} \approx -π/6$ in good agreement with the CLEO data while at the B mass these angles are predicted to be, respectively, $11^\circ$ and $-7^\circ$. With the hadronic phase $e^{i δ_{K \bar K}}$ taken into account, a quark diagram decomposition of the isospin invariant amplitudes in $D \to K \bar K$ decays fits the data provided the exchange diagram contribution is about 1/3 of the tree level one.

hep-ph↗

arXiv1998

Final State Interaction Phases in $ B \to K π$ Decay Amplitudes

A simple Regge pole model for $Kπ$ scattering explains the large $e^{i δ}$ between isospin amplitudes which is observed at the D meson mass ($δ\approx π/2$). It predicts $δ\approx 14^{\circ}- 20^{\circ}$ at the B mass. Implications for ($B \to K π$) decays and extensions of the model to other two-body decay channels are briefly discussed.

hep-ph↗

arXiv1997

Field theory approach to K0-K0bar and B0-B0bar systems

Quantum field theory provides a consistent framework to deal with unstable particles. We present here an approach based on field theory to describe the production and decay of unstable $K^0-\bar{K^0}$ and $B^0-\bar{B^0}$ mixed systems. The formalism is applied to compute the time evolution amplitudes of $K^0$ and $\bar{K^0}$ studied in DAPHNE and CPLEAR experiments. We also introduce a new set of parameters that describe CP violation in $ K \to ππ$ decays without recourse to isospin decomposition of the decay amplitudes.

hep-ph↗

arXiv1996

Effective SU(2)_L x U(1) theory and the Higgs boson mass

We assume the stability of vacuum under radiative corrections in the context of the standard electroweak theory. We find that this theory behaves as a good effective model already at cut off energy scales as low as 0.7 TeV. This stability criterion allows to predict m_H= 318 +- 13 GeV for the Higgs boson mass.

hep-ph↗

arXiv1996

Behaviour of the Absorptive Part of the W Electromagnetic Vertex

The absorptive part of the $WWγ$ vertex induced by massive fermion loops is considered for different kinematical configurations. We show that the axial part of this vertex is different from zero not only when massive fermions are involved but also for massless fermion loops, if one of the W bosons is space-like and the other is time-like. We also discuss in what sense Low's soft photon theorem is satisfied.

hep-ph↗

arXiv1995

S-matrix approach to two-pion production in e^+e^- annihilation and tau decay

Based on the S-matrix approach, we introduce a modified formula for the $π^{\pm}$ electromagnetic form factor which describes very well the experimental data in the energy region $2m_π \leq \sqrt{s} \leq 1.1$ GeV. Using the CVC hypothesis we predict $B(\tpp) = (24.75 \pm 0.38)\% $, in excellent agreement with recent experiments.

hep-ph↗

arXiv1995

Pion-proton scattering and isospin breaking in the $Δ^0-Δ^{++}$ system

We determine the mass and width of the $Δ^{++}\ (Δ^0)$ resonance from data on $π^+ p\ (π^- p)$ scattering both, in the pole of the $S$-matrix and conventional Breit-Wigner approaches to the scattering amplitude. We provide a simple formula that relates the two definitions for the parameters of the $Δ$. Isospin symmetry breaking in the $\d0-\dm$ system depends on the definition of the resonant properties: we find $M_0-M_{++} = 0.40 \pm 0.57\ {\rm MeV},\ Γ_0 -Γ_{++} = 6.89 \pm 0.95\ {\rm MeV}$ in the pole approach while $\wt{M}_0-\wt{M}_{++} = 2.25 \pm 0.68\ {\rm MeV},\ \wtΓ_0 - \wtΓ_{++} = 8.45 \pm 1.11\ {\rm MeV}$ in the conventional approach.

hep-ph↗

arXiv1995

Determination of the Higgs boson mass by the cancellation of ultraviolet divergencies in the $SU(2)_L\times U(1)_Y$ Theory

We assume the vanishing of the quadratic divergences in the $SU(2)_L \otimes U(1)$ electroweak theory. Using $\,$ the $\,$ top $\,$ mass $\,$ value reported recently by the CDF Collaboration $m_t = 176 \pm 8 \pm 10 GeV$, we predict the mass of the Higgs boson to be $m_H = 321 \pm 29 GeV$. If we assume the vanishing of both quadratic and logarithmic divergencies of the top self-mass, we predict $m_t = 170.5 \pm 0.3 GeV $ and $m_H = 308.6 \pm 0.7 GeV.$

hep-ph↗

arXiv1995

Remarks on the $W$ propagator at the resonance

We address the problem of properly defining the $W^{\pm}, Z^0$ propagator in the resonance region. Particular attention is paid to the longitudinal piece of this propagator. We also discuss the related renormalization procedures and the unitarity property.

hep-ph↗