555 research outputs found

### Pure Leptonic Radiative Decays $B^\pm, D_s\to\ell\nu\gamma$ and the Annihilation Graph

Pure leptonic radiative decays of heavy-light mesons are calculated using a
very simple non-relativistic model. Dominant contribution originates from
photon emission from light initial quark. We find
$BR(B^\pm\to\ell\nu\gamma)\sim3.5\times10^{-6}$ and $BR(D_s\to
\ell\nu\gamma)\sim1.7 \times10^{-4}$. The importance of these reactions to
clarify the dynamics of the annihilation graph is emphasized.Comment: 7 pages, LaTeX, 3 figure

### Studying the scale and q^2 dependence of K^+-->pi^+e^+e^- decay

We extract the K^+-->pi^+e^+e^- amplitude scale at q^2=0 from the recent
Brookhaven E865 high-statistics data. We find that the q^2=0 scale is fitted in
excellent agreement with the theoretical long-distance amplitude. Lastly, we
find that the observed q^2 shape is explained by the combined effect of the
pion and kaon form-factor vector-meson-dominance rho, omega and phi poles, and
a charged pion loop coupled to a virtual photon-->e^+e^- transition.Comment: 8 pages, 3 figure

### Transverse Tau Polarization in Decays of the Top and Bottom Quarks in the Weinberg Model of CP Non-conservation

We show that the transverse polarization asymmetry of the $\tau$-lepton in
the decay $t\rightarrow b \tau \nu$ is extremely sensitive to CP violating
phases arising from the charged Higgs exchange in the Weinberg model of CP
non-conservation. Qualitatively, the polarization asymmetries are enhanced over
rate or energy asymmetries by a factor of $\approx {m_t\over m_\tau}\approx
O(100)$. Thus for optimal values of the parameters the method requires $\approx
10^4$ top pairs to be observable rather than $10^7$ needed for rate or energy
asymmetries. We also examine $\tau$ polarization in b decays via $b \rightarrow
c \nu \tau$ and find that it can also be very effective in constraining the CP
violation parameters of the extended Higgs sector.Comment: 11,1 figure, SLAC-PUB-608

### On the Possibility of a New Boson X^0 (214 MeV) in Sigma^+ -> p mu^+ mu^-

We consider the existence of the state X^0 (214 MeV) in Sigma^+ -> p mu^+
mu^- decay found by the HyperCP collaboration. We assume that a fundamental
spin zero boson X^0 coupled to quarks leads to flavor changing s -> d X^0
process. We estimate the scalar and pseudoscalar coupling constants by
considering Sigma^+ -> p X^0 and K^+ -> pi^+ X^0 processes, and find that
pseudoscalar coupling dominates. We then evaluate the branching ratios for K_L
-> pi^0 pi^0 X^0, pi^+ pi^- X^0 and Omega^- -> Xi^- X^0 decays. All these rates
are found to be in the measurable ranges. We also comment on X^0 coupling to
muons and constraints from muon g-2.Comment: 6 pages; typos corrected, references added, 7 page

### Asymmetry in the decay $\Omega^-\to\Xi^-\gamma$

We consider the asymmetry in the decay $\Omega^-\rightarrow\Xi^-\gamma$
assuming that a Vector Meson Dominance approach for the $s\rightarrow d\gamma$
transition gives the dominant contribution. Since in this long-distance
approximation the decay is due to a single quark transition $s\rightarrow
d\gamma$, the angular distribution asymmetry is given by the single positive
asymmetry parameter $\alpha_h = \frac{M^2_s-M^2_d}{M^2_s+M^2_d} = 0.4\pm0.1$.
We also discuss the asymmetry in $\Xi \rightarrow \Sigma^-\gamma$, which is
expected to be between -0.2 and 0.3.Comment: 16 pages,no figures,Late

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