arXiv subjects

Y. L. Wu

Publications and source records attributed to Y. L. Wu.

29 records · Page 2Linked to original sources

arXiv2000

The interplay between Weak and Strong Phases and Direct CP Violation from the Charmless B-meson Decays

We present a general analysis on charmless B-meson decays $B\to ππ$ and $πK$. It is noticed that the final state interactions and inelastic rescattering effects must be significant in order to understand the consistency of the current data. By using general isospin decompositions, the isospin amplitudes and the corresponding strong phases could be extracted from a global $χ^2$ fit of the experimental data. We emphasize that in general there are two, rather than one, relative strong phases in the decomposition. In the assumption of two equalstrong phases as considered in the literature, the current data, especially the ones concerning $B\to π^0 K^{0(\pm)}$decays, will imply a large isospin amplitude $|a^c_{3/2}| > 40 $, which is larger by a factor of five than the one from the naive factorization estimation. When two different strong phases are considered, all the isospin amplitudes can become, within the $1σ$-level, comparable with the theoretical values. We also show that the difference between the two strong phases cannot be too large and will be restricted by the most recent upper bound of $B\to π^0π^0$ decay. In any case, the strong phases are found to be large and the branching ratio of $B\to π^0π^0$ is likely to be enhanced by an order of magnitude in comparison with the one obtained from the naive factorization approach. Direct CP violations in all decay modes are also calculated and found to be close to the sensitivity of the present experiments.

hep-ph↗

arXiv2000

A Consistent Calculation of Heavy Meson Decay Constants and Transition Wave Functions in the Complete HQEFT

Within the complete heavy quark effective field theory (HQEFT), the QCD sum rule approach is used to evaluate the decay constants including 1/m_Q corrections and the Isgur-Wise function and other additional important wave functions concerned at 1/m_Q for the heavy-light mesons. The 1/m_Q corrections to the scaling law f_M \sim F/\sqrt{m_M} are found to be small in HQEFT, which demonstrates again the validity of 1/m_Q expansion in HQEFT. It is also shown that the residual momentum v.k of heavy quark within hadrons does be around the binding energy \barΛ of the heavy hadrons. The calculations presented in this paper provide a consistent check on the HQEFT and shows that the HQEFT is more reliable than the usual HQET for describing a slightly off-mass shell heavy quark within hadron as the usual HQET seems to lead to the breakdown of 1/m_Q expansion in evaluating the meson decay constants. It is emphasized that the introduction of the `dressed heavy quark' mass is useful for the heavy-light mesons (Qq) with m_Q >> \barΛ >> m_q, while for heavy-heavy bound states (ψ_1ψ_2) with masses m_1, m_2 >> \barΛ, like bottom-charm hadrons or similarly for muonium in QED, one needs to treat both particles as heavy effective particles via 1/m_1 and 1/m_2 expansions and redefine the effective bound states and modified `dressed heavy quark' masses within the HQEFT.

hep-ph↗

arXiv2000

|V_ub| and |V_cb|, Charm Counting and Lifetime Differences in Inclusive Bottom Hadron Decays

Inclusive bottom hadron decays are analyzed based on the heavy quark effective field theory (HQEFT). Special attentions in this paper are paid to the b\to u transitions and nonspectator effects. As a consequence, the CKM quark mixing matrix elements |V_ub| and |V_cb| are reliably extracted from the inclusive semileptonic decays B\to X_u e νand B\to X_c e ν. Various observables, such as the semileptonic branch ratio B_SL, the lifetime differences among B^-, B^0, B_s and Λ_b hadrons, the charm counting n_c, are predicted and found to be consistent with the present experimental data.

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arXiv2000

Inclusive Decays of Bottom Hadrons in New Formulation of Heavy Quark Effective Field Theory

We apply the new formulation of heavy quark effective field theory (HQEFT) to the inclusive decays of bottom hadrons. The long-term ambiguity of using heavy quark mass or heavy hadron mass for inclusive decays is clarified within the framework of the new formulation of HQEFT. The $1/m_b$ order corrections are absent and contributions from $1/m_b^2$ terms are calculated in detail. This enables us to reliably extract the important CKM matrix element $|V_{cb}|$ from the inclusive semileptonic decay rates. The resulting lifetime ratios $τ(B^0_s)/τ(B^0)$ and $τ(Λ_b)/τ(B^0)$ are found to well agree with the experimental data. We also calculate in detail the inclusive semileptonic branching ratios and the ratios of the $τ$ and $β$ decay rates as well as the charm countings in the $B^0$, $B^0_s$ and $Λ_b$ systems. For $B^0$ decays, all the observables are found to be consistent with the experimental data. More precise data for the $B^0$ decays and further experimental measurements for the $B^0_s$ and $Λ_b$ systems will be very useful for testing the framework of new formulation of HQEFT at the level of higher order corrections.

hep-ph↗

arXiv2000

Searching for Rephase-Invariant CP- and CPT-violating Observables in Meson Decays

We present a general model-independent and rephase-invariant formalism that cleanly relates CP and CPT noninvariant observables to the fundamental parameters. Different types of CP and CPT violations in the K^0-, B^0-, B_s^0- and D^0-systems are explicitly defined. Their importance for interpreting experimental measurements of CP and CPT violations is emphasized. In particular, we show that the time-dependent measurements allow one to extract a clean signature of CPT violation.

hep-ph↗

arXiv2000

Weak Matrix Elements and |V_cb| in New Formulation of Heavy Quark Effective Field Theory

The heavy quark effective field theory (HQEFT) containing both effective `quark fields' and `antiquark fields' is investigated in detail. By integrating out (but not neglecting) the effective antiquark fields, we present a new formulation of effective theory which differs from the usual heavy quark effective theory (HQET) and exhibits valuable features because of the inclusion of the contributions from the antiquark fields. Matrix elements of vector and axial vector heavy quark currents between pseudoscalar and vector mesons containing a heavy quark (b or c) are then evaluated systematically up to the order of $1/m^2_Q$ and parameterized by a set of universal form factors. With a consistent normalization condition between the effective heavy hadron states, the form factors at zero recoil are related to the ground state meson masses, which enables us to estimate the values of form factors at zero recoil. In particular, the Luke's theorem comes out automatically in the new formulation of HQEFT without the need of imposing the equation of motion $iv\cdot D Q^{+}_{v} =0$. Consequently, the differential decay rates of both $B\to D^{\ast}lν$ and $B\to D lν$ do not receive $1/m_{Q}$ order corrections at zero recoil, which is not the case in the usual HQET. Thus we quote that the Cabibbo-Kobayashi-Maskawa matrix element $| V_{cb}|$ can nicely be extracted from either of these two exclusive semileptonic decays at the order of $1/m^2_Q$. Our estimates for $|V_{cb}|$ are presented.

hep-ph↗

arXiv2000

Separating Different Models from Measuring $α, β, γ$

New physics effects on the $B^0-\bar{B}^0$ mixing and B-decay amplitudes are discussed. By a combined analysis, the model of new physics can be partially distinguished.It is emphasized that the extraction of unitarity angles $β$ and $γ$ through rare decay $K\to πν\tildeν$ and charged B decay $B^{\pm}\to DK^{\pm}$ respectively is not likely to be affected by new physics. Such an observation could be used to distinguish the new physics effects from different mode ls. For instance, the top quark two-Higgs doublet model can be easily separated from those models without new phase in B-decay amplitudes, and can be further distinguished from the most general two Higgs doublet model by its absence of new phase in the $B^0-\bar{B}^0$ mixing.

hep-ph↗

arXiv1999

$F^0-\bar{F}^0 $ Mixing and CP Violation in the General Two Higgs Doublet Model

A phenomenological analysis of the general two Higgs doublet model is presented. Possible constraints of the Yukawa couplings are obtained from the $K^0-\bar{K}^0, B^0-\bar{B}^0$ and $D^0-\bar{D}^0$ mixings. A much larger $D^0-\bar{D}^0$ mixing than the standard model prediction is possible. It is shown that the emerging of various new sources of CP violation in the model could strongly affect the determination of the unitarity triangle. It can be helpful to look for a signal of new physics by comparing the extracted angle $β$ from two different ways, such as from the process $B\to J/ψK_{S}$ and from fitting the quantities $|V_{ub}|, Δm_{B}$ and $ε$.

hep-ph↗

arXiv1995

Extraction of $α$ From the CP Asymmetry in B^0/\bar B^0 --> pi+ pi- Decays

The influence of strong and electroweak penguin amplitudes in $B/ \bar B \rightarrow π^+π^-$ is investigated in connection with the determination of the unitarity triangle angle $α$ of the CKM matrix. A relation between the observable asymmetry, the angle $α$, and the penguin amplitude is established. A model calculation of the penguin amplitude shows that the CP asymmetry in $B^{0}\rightarrow π^{+}π^{-}$ decays is only mildly influenced by the penguin amplitudes. Experimental limits on pure penguin and penguin dominated processes are consistent with the model. This information also suggests in a rather model independent way that penguin amplitudes will not be a serious complicating factor in the determination of $α$ from the $π^{+}π^{-}$ time dependent asymmetry.

hep-ph↗

arXiv1995

Low Energy Phenomena in a Model With Symmetry Group SUSY SO(10) X Delta (48) X U(1)

Fermion masses and mixing angles including that of neutrinos are studied in a model with symmetry group SUSY $SO(10)\times Δ(48) \times U(1)$. Universality of Yukawa coupling of superfields is assumed. The resulting texture of mass matrices in the low energy region depends only on a single coupling constant and VEVs caused by necessary symmetry breaking. 13 parameters involving masses and mixing angles in the quark and charged lepton sector are successfully described by only five parameters with two of them determined by the scales of U(1), SO(10) and SU(5) symmetry breaking compatible with the requirement of grand unification and proton decay. The neutrino masses and mixing angles in the leptonic sector are also determined with the addition of a Majorana coupling term. It is found that LSND $\barν_μ\rightarrow \barν_{e}$ events, atmospheric neutrino deficit and the mass limit put by hot dark matter can be naturally explained. Solar neutrino puzzle can be solved only by introducing sterile neutrino with one additional parameter. More precise measurements of $α_{s}(M_{Z})$, $V_{cb}$, $V_{ub}/V_{cb}$, $m_{b}$, $m_{t}$, as well as various CP violation and neutrino oscillation experiments will provide crucial tests of the present model.

hep-ph↗

arXiv1995

Rephase-Invariant CP-Violating Observables and Mixings in the $B^0$, $D^0$, $K^0$ Systems.

We present a general model-independent and rephase-invariant formalism that cleanly relates observables to the fundamental parameters and explicitly separates different types of CP violation in the $B^0$-, $D^0$- and $K^0$- systems. We emphasize its importance when interpreting experimental measurement of CP violation, the unitarity triangle, and probes of new physics.

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