arXiv subjects

T. N. Pham

Publications and source records attributed to T. N. Pham.

54 records · Page 3Linked to original sources

arXiv2003

CP-violating asymmetry in $B^- \to π^+ π^- K^-$ and $B^- \rarr K^+ K^- K^-$ decays

The recent Belle and Babar measurements of the branching ratios $B^- \to π^+ π^- K^-$ and $B^- \to K^+ K^- K^-$ and $B^\pm \to χ_{c0} K^\pm$ have renewed interests in these decays as another mean to look for direct CP violation in B decays. In this talk, I would like to discuss a recent analysis of the CP violating asymmetry in the partial widths for the decays $B^- \to π^+ π^- K^-$ and $B^- \to K^+ K^- K^-$, which results from the interference of the non resonant amplitude with the resonant amplitude $B^\pm \to χ_{c0} K^\pm $ $ \rarrπ^+ π^- K^\pm $ and $B^\pm \to χ_{c0} K^\pm$ $ \to K^+ K^- K^\pm$. For $γ\simeq 58^o$ we predict that the partial width asymmetry could reach 10% for the $B^- \to π^+ π^- K^-$ decay and 16% for the $B^- \to K^+ K^- K^-$decay.

hep-ph↗

arXiv2002

Charming penguin and direct CP-violation in charmless B decays

In the study of two-body charmless B decays as a mean of looking for direct CP-violation and measuring the CKM mixing parameters in the Standard Model, the short-distance penguin contribution with its absorptive part generated by charm quark loop seems capable of producing sufficient $B \to Kπ$ decays rates, as obtained in factorization and QCD-improved factorization models. However there are also long-distance charming penguin contributions which could give rise to a strong phase due to the rescattering $D^{*}D^{*}_{s} \to Kπ$ etc. In this talk, I would like to discuss recent works on the charming penguin contribution as a different approach to the calculation of these contributions in two-body charmless B decays. We find that the charming penguin contribution is significant for $B\to Kπ$ decays and, together with the tree and penguin terms, produces large branching ratios in agreement with data, though the analysis is affected by large theoretical uncertainties. The absorptive part due to the charmed meson intermediate states is found to produce large CP asymmetries for $B \to Kπ, ππ$ decays.

hep-ph↗

arXiv2002

$B^- \to K^- χ_{c0}$ decay from charmed meson rescattering

We study the process $B^- \to K^- χ_{c0}$ considering intermediate charmed meson rescattering effects. For this decay mode the naive factorization ansatz would predict a vanishing amplitude. We estimate contributions from the $D^{(*)}_{s} D^{(*)}\to K^- χ_{c0}$ rescattering amplitudes, and compare the result with recent experimental measurements. We find that rescattering effects are able to produce a large branching ratio consistent with measurements by Belle Collaboration. We also consider rescattering effects in $B^- \to K^- J/ψ$, arguing that they play a similar role in producing a large branching fraction for this colour-suppressed decay mode.

hep-ph↗

arXiv2002

CP violating phase $γ$ and the partial widths asymmetry in $B^- \to π^+ π^- K^-$ and $B^- \to K^+ K^- K^-$ decays

Motivated by recent Belle measurement of the branching ratios $B^- \to π^+ π^- K^-$ and $B^- \to K^+ K^- K^-$ and $B^\pm \to χ_{c0} K^\pm$, we investigate the CP violating asymmetry in the partial widths for the decays $B^- \to π^+ π^- K^-$ and $B^- \to K^+ K^- K^-$, which results from the interference of the nonresonant decay amplitude with the resonant amplitude $B^\pm \to χ_{c0} K^\pm $ $ \toπ^+ π^- K^\pm $ and $B^\pm \to χ_{c0} K^\pm$ $ \to K^+ K^- K^-$. By taking $γ\simeq 58^o$ we predict that the partial widths asymmetry is reaching 10% for the $B^- \to π^+ π^- K^-$ decay and 16% for the $B^- \to K^+ K^- K^-$decay.

hep-ph↗

arXiv2002

Charming penguin contributions to charmless B decays into two pseudoscalar mesons

We present estimates of the charming penguin contribution to B => K pi, pi pi,K eta, K eta' decays due to intermediate charmed meson states. We find that this contribution is indeed significant for B => K pi decays, and its inclusion, together with the tree and penguin terms, produces large branching ratios in agreement with data, though the analysis is affected by large theoretical uncertainties. On the other hand, for B => pi pi, K eta, K eta' decays, the effect of the charming penguin contribution is more modest. We also compute CP asymmetries for B => K pi, pi pi decays and we obtain rather large results.

hep-ph↗

arXiv2001

Charming penguin in nonleptonic B decays

In the study of two-body charmless B decays as a mean of looking for direct CP-violation and measuring the CKM mixing parameters in the Standard Model, the short-distance penguin contribution with its absorptive part generated by charm quark loop seems capable of producing sufficient $B \to Kπ$ decays rates, as obtained in factorization and QCD-improved factorization models. However there are also long-distance charming penguin contributions which also give rise to a strong phase due to the rescattering $D^{*}D^{*} \to Kπ$ . In this talk, I would like to discuss \cite{Isola} a recent work on the long-distance charming penguin as a a different approach to the calculation of the penguin contributions in $B \to Kπ$ decays from charmed meson intermediate states. Using chiral effective Lagrangian for light and heavy mesons, corrected for hard pion and kaon momenta, we show that the charming-penguin contributions increase significantly the $B \to Kπ$ decays rates from its short-distance contributions, giving results in better agreement with experimental data.

hep-ph↗

arXiv2001

Charming penguin contributions to B => K π

We present calculations of the charming-penguin long-distance contributions to B => K πdecays due to intermediate charmed meson states. Our calculation is based on the Chiral Effective Lagrangean for light and heavy mesons, corrected for the hard pion and kaon momenta. We find that the charming-penguin contributions increase significantly the B => K πdecay rates in comparison with the short-distance contributions, giving results in better agreement with experimental data.

hep-ph↗

arXiv2000

Analysis of $B \to Kπ$ decays with small elastic final state interactions

An analysis of $B \to Kπ$ decays is given, assuming a small elastic $πK $ rescattering phase difference.Using factorization model only for the tree-level and electroweak penguin amplitudes, we show that the strong penguin amplitude, its absorptive part and the CP-violation weak phase $γ$ can be obtained from the measured $B \to Kπ$ branching ratios. The strength of the strong penguin and its absorptive part thus obtained from the CLEO data, are found to be very close to factorization model values and suggests a current $s$ quark mass around $m_{s} = 106 \rm MeV$. The central value of $γ$ is found to be around $76.10^{\circ}$, with a possible value in the range $50^{\circ}-100^{\circ}$.

hep-ph↗

arXiv2000

$B \to Kπ$ decays and the weak phase angle $γ$

The large branching ratios for $B \to Kπ$ decays as observed by the CLEO Collaboration indicate that penguin interactions contribute a major part to the decay rates and provide an interference between the Cabibbo-suppressed tree and penguin contributions resulting in a CP-asymmetry between the $B \to Kπ$ and its charge conjugate mode. The CP-averaged decay rates depend also on the weak phase $γ$ and give us a determination of this phase. In this talk, I would like to report on a recent analysis of $B \to Kπ$ decays using factorisation model with final state interaction phase shift included. We find that factorisation seems to describe qualitatively the latest CLEO data. We also obtain a relation for the branching ratios independent of the strength of the strong penguin interactions. This relation gives a central value of $0.60 \times 10^{-5}$ for ${\mathcal B}(\bar{B}^{0} \to \bar{K}^{0}π^{0})$, somewhat smaller than the latest CLEO measurement. We also find that a ratio obtained from the CP-averaged $B \to Kπ$ decay rates could be used to test the factorisation model and to determine the weak angle $γ$ with more precise data, though the latest CLEO data seem to favor $γ$ in the range $90^{\circ}-120^{\circ}$.

hep-ph↗

arXiv2000

Test of factorisation in $B \to Kπ$ decays

We analyse the $B \to Kπ$ decays using the factorisation model with final state interaction phase shift included. We find that factorisation seems to describe qualitatively the latest CLEO data. For a test of the factorisation model, we derive a relation for the branching ratios independent of the strength of the strong penguin interactions. This relation gives a central value of $(0.60 \times 10^{-5})$ for ${\mathcal B}(\bar{B}^{0} \to \bar{K}^{0}π^{0})$, somewhat smaller than the latest CLEO measurement, but the experimental errors are yet too big to take it as a real prediction of the factorisation model. We also find that a ratio obtained from the CP-averaged $B \to Kπ$ decay rates could be used to test the factorisation model and to determine the weak angle $γ$ with more precise data, though the l atest CLEO data seem to favor $γ$ in the range of $(90^{\circ}-120^{\circ})$.

hep-ph↗

arXiv1999

B => ππ\ell νdecays in a QCD relativistic potential model

In the framework of a QCD relativistic potential model we evaluate the form factors describing the exclusive decay B => ππ\ell ν. The calculation is performed in a phase space region far away from the resonances and therefore is complementary to other decay mechanisms where the pions are produced by intermediate particles, e.g. in the chiral approach. We give an estimate of the contribution of the non resonant channel of the order of BR(B- => π+ π- \ell ν) \approx 2.2 x 10^(-4).

hep-ph↗

arXiv1999

CP-violating asymmetry in B decays to 3 pseudoscalar mesons

The measurement of CP asymmetries in charged B meson decays might provide the first demonstration of CP violation outside the K system. Among the usual three CP-odd phases $α$, $β$ and $γ$, the phase $γ$ seems to be the most difficult to explore experimentally. In this talk I would like to report on a recent analysis of the CP asymmetry in the partial widths for the non-leptonic decays $B^{\pm} \to M {\bar M} π^{\pm}$ ($ M = π^+, K ^+, π^0, η$), which results from the interference of the non-resonant decay amplitude with the resonant amplitude for $B^{\pm} \to χ_{c0} π^{\pm} $ followed by the decay $χ_{c0} \to M {\bar M} $. The CP violating phase $γ$ can be extracted from the measured asymmetry. We find that the partial width asymmetry for $B^\pm \to π^+ π^- π^\pm$ is about $0.33~\sin γ$, and about $0.45~ \sin γ$ for $B^\pm \to K^+ K^-π^\pm$, while it is somewhat smaller for $B^\pm \to π^0 π^0 π^\pm$ and $B^\pm \to ηηπ^\pm$.

hep-ph↗

arXiv1998

The penguin operators in nonresonant $B^- \to M \bar M π^-$ $(M =π^-, K^-, K^0)$ decays

We investigate the contributions coming from the penguin operators in the nonresonant $B^- \to M \bar M π^-$ ($M =π^-, K^-, K^0$) decays. The effective Wilson coefficients of the the strong penguin operators $O_{4,6}$ are found to be relatively larger. We calculate the contributions arising from the $O_4$ and $O_6$ operators in the nonresonant decays $B^- \to M \bar Mπ^-$ ($M = π^-, K^-, \bar K^0$) using a model combining heavy quark symmetry and the chiral symmetry, developed previously. We find that the forbidden nonresonant $B^- \to K^0 \bar K^0 π^-$ decay occurs through the strong penguin operators. These penguin contributions affect the branching ratios for $B^- \to M \bar Mπ^-$ ($M = π^-, K^-$) by only a few percent. The branching ratio for $B^- \to K^0 \bar K^0 π^-$ is estimated to be of the order $ 10^{-6}$.

hep-ph↗

arXiv1998

The CP violating asymmetry in $B^{\pm} \to M {\bar M} π^{\pm}$ decays

We analyze the asymmetry in the partial widths for the decays $B^{\pm} \to M {\bar M} π^{\pm}$ ($ M = π^+, K ^+, π^0, η$), which results from the interference of the nonresonant decay amplitude with the resonant amplitude for $B^{\pm} \to χ_{c0} π^{\pm} $ followed by the decay $χ_{c0} \to M {\bar M} $. The CP violating phase $γ$ can be extracted from the measured asymmetry. We find that the partial width asymmetry for $B^\pm \to π^+ π^- π^\pm$ is about $0.33~sin γ$, and about $0.45~ sin γ$ for $B^\pm \to K^+ K^-π^\pm$, while it is somewhat smaller for $B^\pm \to π^0 π^0 π^\pm$ and $B^\pm \to ηηπ^\pm$. Potential sources of uncertainties in these results, primarily coming from poorly known input parameters, are discussed.

hep-ph↗

arXiv1998

Signal for CP violation in $B^{\pm} \to P {\bar P} π^{\pm}$ decays

We analyze the partial rate asymmetry in $B^{\pm} \to P {\bar P} π^{\pm}$ decays ($ P = π^+, K ^+, π^0, η$) which results from the interference of the nonresonant decay amplitude and the resonant amplitude for $B^{\pm} \to χ_{c0} π^{\pm} $ followed by the decay $χ_{c0} \to P {\bar P} $. The CP violating phase $γ$ can be extracted from the measured asymmetry. We find that the partial rate asymmetry for $B^\pm \to π^+ π^- π^\pm$ is $0.33~sin γ$, while for $B^\pm \to K^+ K^-π^\pm$ it amounts $0.45~ sin γ$.

hep-ph↗

arXiv1998

Resonant and nonresonant D+ -> K- pi+ l+ nu(l) semileptonic decays

We analyse the semileptonic decay D+ -> K- pi+ l+ nu(l) using an effective Lagrangian developed previously to describe the decays D -> P l nu(l) and D -> V l nu(l). Light vector mesons are included in the model which combines the heavy quark effective Lagrangian and chiral perturbation theory approach. The nonresonant and resonant contributions are compared. With no new parameters the model correctly reproduces the measured ratio Gamma(nres)/Gamma(nres + res). We also present useful nonresonant decay distributions. Finally, a similar model, but with a modified current which satisfies the soft pion theorems at the expense of introducing another parameter, is analyzed and the results of the models are compared.

hep-ph↗

arXiv1997

Electromagnetic Mass Difference of Heavy Mesons

Using the Cottingham formula, we give an estimate of the electromagnetic mass splitting of pseudoscalar heavy mesons in the beauty and charm sector. We include in the dispersion relation the Born term, the $1^-$ resonance and the positive parity $1^+$ resonance. We also evaluate the contribution to the mass difference from the isospin breaking quark mass differences. Our results: $m_{B^+}-m_{B^0} = - 0.83\pm 0.34 MeV$ and $m_{D^+}-m_{D^0} = + 4.33\pm 0.37 MeV$, are in agreement with the experimental measurements: $m_{B^+}-m_{B^0} = - 0.35\pm 0.29 MeV$ and $m_{D^+}-m_{D^0} = + 4.78\pm 0.10 MeV$. We also compute the mass differences in the infinite heavy quark mass limit, which show small deviations from the finite mass results for the B case and 30% effects in the charm case.

hep-ph↗

arXiv1996

Final State Interactions in $B -> D ρ$ and $B -> D^{*}π$ Decays

We analyze final state strong interaction effects in $B -> D ρ$ and $B -> D^{*}π$ decays using the Regge model. We find that, due to the smallness of the contributions from the non-leading Regge trajectories ($ρ$, $f$, $π$ etc.), final state interaction phases are small if the Pomeron coupling to the charm quark is suppressed in comparison to lighter quarks. Our conclusion is that for $B$ decays into states containing charm, final state interaction effects should play a minor role.

hep-ph↗