6,263 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.
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
Searching for Dark Matter Signals in the Left-Right Symmetric Gauge Model with CP Symmetry
We investigate singlet scalar dark matter (DM) candidate in a left-right
symmetric gauge model with two Higgs bidoublets (2HBDM) in which the
stabilization of the DM particle is induced by the discrete symmetries P and
CP. According to the observed DM abundance, we predict the DM direct and
indirect detection cross sections for the DM mass range from 10 GeV to 500 GeV.
We show that the DM indirect detection cross section is not sensitive to the
light Higgs mixing and Yukawa couplings except the resonance regions. The
predicted spin-independent DM-nucleon elastic scattering cross section is found
to be significantly dependent on the above two factors. Our results show that
the future DM direct search experiments can cover the most parts of the allowed
parameter space. The PAMELA antiproton data can only exclude two very narrow
regions in the 2HBDM. It is very difficult to detect the DM direct or indirect
signals in the resonance regions due to the Breit-Wigner resonance effect.Comment: 24 pages, 8 figures. minor changes and a reference added, published
in Phys. Rev.
Research Program towards Observation of Neutrino-Nucleus Coherent Scattering
The article describes the research program pursued by the TEXONO
Collaboration towards an experiment to observe coherent scattering between
neutrinos and the nucleus at the power reactor. The motivations of studying
this process are surveyed. In particular, a threshold of 100-200 eV has been
achieved with an ultra-low-energy germanium detector prototype. This detection
capability at low energy can also be adapted to conduct searches of Cold Dark
Matter in the low-mass region as well as to enhance the sensitivities in the
study of neutrino magnetic moments.Comment: 5 pages, 8 figures ; Proceedings of TAUP-2005 Workshop, Spain, 2005.
Updated on 2006/9/15 for Proceedings of Neutrino-2006 Conference, Santa Fe,
200
The swap operation in the two-qubit Heisenberg XXZ model-effects of anisotropy and magnetic field
In this paper we study the swap operation in a two-qubit anisotropic XXZ
model in the presence of an inhomogeneous magnetic field. We establish the
range of anisotropic parameter within which the swap operation is feasible. The
swap errors caused by the inhomogeneous field are evaluated
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