35,587 research outputs found
Implications of Charmless B Decays with Large Direct CP Violation
Based on the most recent data in charmless B decays including the very
recently reported large direct CP violations, it is shown that the weak phase
gamma can well be extracted without two-fold ambiguity even only from two decay
modes pi^+pi^- and pi^+K^-, and its value is remarkably consistent with the
global standard model fit at a compatible accuracy. A fit to all the pi pi, pi
K data favor both large electroweak penguin and color-suppressed tree amplitude
with large strong phases. It is demonstrated that the inclusion of small
SU(3)symmetry breaking effects of strong phases and the inelastic rescattering
effects can well improve the consistency of the data, while both effects may
not be sufficient to arrive at a small electroweak penguin amplitude in the
standard model. It is of interest to notice that large or small electroweak
penguin amplitude becomes a testable prediction as they lead to significantly
different predictions for the direct CP violations for pi^0 pi^0, pi^0 K^0
modes. Clearly, precise measurements on charmless B decays will provide a
window for probing new physics.Comment: 4 pages, 1 figure, 1 table, results updated with the latest data.
conclusions unchanged. Refence added. published versio
Charmless decays B->pipi, piK and KK in broken SU(3)symmetry
Charmless B decay modes and aresystematically
investigated with and without flavor SU(3) symmetry. Independent analyses on
and modes both favor a large ratio between color-suppressed
tree () and tree ( diagram, which suggests that they are more likely to
originate from long distance effects. The sizes of QCD penguin diagrams
extracted individually from , and modes are found to
follow a pattern of SU(3) breaking in agreement with the naive factorization
estimates. Global fits to these modes are done under various scenarios of
SU(3)relations. The results show good determinations of weak phase in
consistency with the Standard Model (SM), but a large electro-weak penguin
(P_{\tmop{EW}}) relative to with a large relative strong phase are
favored, which requires an big enhancement of color suppressed electro-weak
penguin (P_{\tmop{EW}}^C) compatible in size but destructively interfering
with P_{\tmop{EW}} within the SM, or implies new physics. Possibility of
sizable contributions from nonfactorizable diagrams such as -exchange (),
annihilation() and penguin-annihilation diagrams() are investigated.
The implications to the branching ratios and CP violations in modes are
discussed.Comment: 27 pages, 9 figures, reference added, to appear in Phy.Rev.
Efficient single-photon-assisted entanglement concentration for partially entangled photon pairs
We present two realistic entanglement concentration protocols (ECPs) for pure
partially entangled photons. A partially entangled photon pair can be
concentrated to a maximally entangled pair with only an ancillary single photon
in a certain probability, while the conventional ones require two copies of
partially entangled pairs at least. Our first protocol is implemented with
linear optics and the second one is implemented with cross-Kerr nonlinearities.
Compared with other ECPs, they do not need to know the accurate coefficients of
the initial state. With linear optics, it is feasible with current experiment.
With cross-Kerr nonlinearities, it does not require the sophisticated
single-photon detectors and can be repeated to get a higher success
probability. Moreover, the second protocol can get the higher entanglement
transformation efficiency and it maybe the most economical one by far.
Meanwhile, both of protocols are more suitable for multi-photon system
concentration, because they need less operations and classical communications.
All these advantages make two protocols be useful in current long-distance
quantum communications
Implications of new data in charmless B decays
Based on the latest experimental data of and modes, a
model-independent analytical analysis is presented. The CP-averaged branching
ratio difference in decays with and
is reduced though it remains larger than the prediction from the standard
model(SM) as both measured and are enhanced, which indicates that a
room for new physics becomes smaller. The present data of decay reduce
the ratio from the previous value of to , which is still larger than the theoretical estimations based on
QCD factorization and pQCD. Within SM and flavor SU(3) symmetry, the current
data also diminish the ratio from the previous value to with a large strong phase , while its value remains much larger than the one extracted from
the modes. The direct CP violation is
predicted to be , which is consistent
with the present data. Two kinds of new effects in both strong and weak phases
of the electroweak penguin diagram are considered. It is found that both cases
can reduce the ratio to and lead to roughly the same
predictions for CP violation in .Comment: 13 pages, 4 figure
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