Searcharxiv⌕ Search

arXiv subjects

Xuan-Yem Pham

Publications and source records attributed to Xuan-Yem Pham.

3 recordsLinked to original sources
arXiv2002

On the B $ +AFw-to J/+AFw-Psi K^* $ Decay

We calculate the process- and polarization-dependent nonfactorizable terms $+AFw-widetilde{a}_{+AFw-lambda}$ of the B$+AFw-to$ J$/+AFw-Psi {+AFw-rm K^*}$ decay within the QCD-improved factorization approach. The longitudinal part $+AFw-widetilde{a}_{0}$ is infrared convergent and large enough to agree with recent experimental data, provided that the B-K$^*$ form factors $A_1(m^2_{+AFw-Psi})$ and $A_2(m^2_{+AFw-Psi})$ satisfy some constraints met by many (but not all) models. The transverse parts $+AFw-widetilde{a}_{+AFw-pm}$ on the other hand are infrared divergent, the procedure used to handle such divergence is discussed in relation with the B$+AFw-to$ J$/+AFw-Psi {+AFw-rm K}$ case in which the same problem arises. Our nonzero phases of the helicity amplitudes are consistent with experimental data recently measured for the first time by the BaBar collaboration.

hep-ph↗
arXiv2001

Gluon-Photon mixing in dense QCD

At high baryonic density with the formation of a diquark condensate $Δ\neq 0$, the QCD color symmetry is spontaneously broken. Being massive by the Anderson-Higgs mechanism, gluon and photon should mix together within two linear combinations due to the color non-conservation. Consequently a gluon $\widetilde{G}$ could decay into an $e^- e^+$ pair via its photon component. With a low invariant mass (about a few ten MeV) and an extremely narrow width peaking above the continuum background, the purely leptonic decay of a strongly-interacting gluon $\widetilde{G} \to e^- + e^+$ constitutes a very distinctive signature of the color superconductivity phase. By a similar scenario of gluon-$Z$ mixing, another "missing-energy" decay into invisible neutrinos $\widetilde{G} \to ν+\barν$ could arise, its amplitude is however $(Δ/M_Z)^2$ power-suppressed.

hep-ph↗
arXiv1999

CP Asymmetries in B_d \to D^{*+}D^{*-} and B_s \to D^{*+}_s D^{*-}_s Decays: P-wave Dilution, Penguin and Rescattering Effects

Determination of the CP-violating parameters \sin 2βand \sin 2β' is shown to be possible from B^0_d vs \bar{B}^0_d \to D^{*+}D^{*-} and B^0_s vs \bar{B}^0_s \to D^{*+}_sD^{*-}_s decays {\it without} doing the angular analysis. The P-wave dilution factors of these two asymmetries are found to be 0.89 and 0.90, respectively, using the factorization approximation and heavy quark symmetry. The penguin-induced corrections amount to about 2% and 3% in the corresponding B_d and B_s channels. Final-state rescattering effects could be handled by detecting the neutral modes B^0_d and \bar{B}^0_d \to D^{*0}\bar{D}^{*0}.

hep-ph↗