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J. -M. Gerard

Publications and source records attributed to J. -M. Gerard.

27 records · Page 2Linked to original sources
arXiv1999

Phases and Amplitudes in Inclusive $Ψ$ and $Ψ'$ Decays

In inclusive decays of the $Ψ$ (3097), electromagnetic and gluonic annihilation amplitudes add incoherently, namely they are 90$^\circ$ out of phase. We argue that this incoherence must persist in each exclusive decay channel. For inclusive $Ψ'$ (3686) decays, we suggest the absence of a significant direct annihilation amplitude into three gluons and propose a new amplitude via QCD anomalies and the $h_c$ (3526) off shell. Phenomenological implications for exclusive decay channels are pointed out.

hep-ph↗
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↗
arXiv1998

Tests for the asymptotic behaviour of the gamma^* --> gamma pi^0 form factor

The gamma^* --> gamma pi^0 transition measured at different photon virtualities already provides us with a clean test for the behaviour of the pi^0 gamma^* gamma off-shell axial anomaly at large time-like squared momenta. It also allows reliable predictions for the branching ratio of heavy quarkonium decays into omega pi^0.

hep-ph↗
arXiv1997

Isospin amplitudes and CP violation in $(B \to Kπ)$ decays

We present a simple isospin invariant parametrization for $(B \to Kπ)$ decay amplitudes which consistently includes CP violation and (quasi-elastic) hadronic final states interactions. We find that the observed $(B \to Kπ)$ decays do not lead to a significant bound on the angle $γ$ of the unitarity triangle. On the other hand, we claim that a sizeable CP violation asymmetry in $(B^{\pm} \to Kπ^{\pm})$ rates is by no means excluded.

hep-ph↗
arXiv1997

A Dynamical Scheme for a Large CP-Violating Phase

A dynamical scheme where the third generation of quarks plays a distinctive role is implemented. New interactions with a $θ$ term induce the breaking of the electroweak symmetry and the top-bottom mass splitting. A large CP-violating phase naturally follows from the latter.

hep-ph↗
arXiv1996

A light stop and electroweak baryogenesis

The possibility of creating baryon asymmetry at the electroweak phase transition in the minimal supersymmetric standard model is considered for the case when right-handed squarks are much lighter than left-handed ones. It is shown that the usual requirement v(T_c)/T_c > 1 for baryogenesis can be satisfied in a range of the parameters of the model, consistent with present experimental bounds.

hep-ph↗
arXiv1995

Is the standard Higgs scalar elementary?

In the standard electroweak model, the measured top quark mass requires a sizeable Yukawa coupling to the fundamental scalar. This large coupling alone might induce a dynamical breaking of the electroweak symmetry as well as non-perturbative effects. If such is the case, even a standard Higgs scalar as light as 80 GeV should have a non-negligible $t \bar{t}$ component induced by the top condensate.

hep-ph↗