108,993 research outputs found
Lepton flavor-changing Scalar Interactions and Muon
A systematic investigation on muon anomalous magnetic moment and related
lepton flavor-violating process such as \m\to e\g, \t\to e\g and \t\to
\m\g is made at two loop level in the models with flavor-changing scalar
interactions. The two loop diagrams with double scalar exchanges are studied
and their contributions are found to be compatible with the ones from Barr-Zee
diagram. By comparing with the latest data, the allowed ranges for the relevant
Yukawa couplings in lepton sector are obtained. The results show a
hierarchical structure of Y_{\m e, \t e} \ll Y_{\m \t} \simeq Y_{\m\m} in the
physical basis if is found to be . It
deviates from the widely used ansatz in which the off diagonal elements are
proportional to the square root of the products of related fermion masses. An
alternative Yukawa coupling matrix in the lepton sector is suggested to
understand the current data. With such a reasonable Yukawa coupling ansatz, the
decay rate of \t\to \m\g is found to be near the current experiment upper
bound.Comment: 15 pages, Revtex, 9 figures, published version in EPJ
A Time Evolution Study of the Superhumps of the Dwarf Nova 1RXS J232953.9+062814 by Wavelet Transform
The time evolution behaviour of the superhumps of the dwarf nova 1RXS
J232953.9+062814 is investigated with the wavelet analysis method. On the basis
of two nights CCD photometry performed during its first superoutburst as well
as other published brightness data, we reveal the superhump's time-dependence
as a function of periods and time. Our light curves, which phased in the rapid
decay ending portion of the superoutburst and in the dawn of a following normal
outburst, are important to help trace the superhump evolution for the star.
Evident amplitude variations of the superhumps, reflecting the fading of
outbursts, are detected. The general profile of brightness fading over the
outbursts roughly followed an exponential decay law or a form of a five-order
polynomial. Both the superhump period and the orbital period of the binary
system are detected in the present data. We obtain P_sh=0.04575(5) d and
P_orb=0.04496(5) d. They agree with the existing values based on additional
data. The two periods exchanged their roles during the superhump evolution.Comment: 7 pages, 9 figures, submitted to Astronomy & Astrophysic
Is the meson a dynamically generated resonance? -- a lesson learned from the O(N) model and beyond
O(N) linear model is solvable in the large limit and hence
provides a useful theoretical laboratory to test various unitarization
approximations. We find that the large limit and the
limit do not commute. In order to get the correct large spectrum one has
to firstly take the large limit. We argue that the meson may
not be described as generated dynamically. On the contrary, it is most
appropriately described at the same level as the pions, i.e, both appear
explicitly in the effective lagrangian. Actually it is very likely the
meson responsible for the spontaneous chiral symmetry breaking in a lagrangian
with linearly realized chiral symmetry.Comment: 15 pages, 3 figurs; references added; discussions slightly modified;
revised version accepted by IJMP
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Enhanced forward stimulated Brillouin scattering in silicon photonic slot waveguide Bragg grating
We study the forward stimulated Brillouin scattering process in a suspended silicon slot waveguide Bragg grating. Full-vectorial formalism is applied to analyze the interplay of electrostriction and radiation pressure. We show that radiation pressure is the dominant factor in the proposed waveguide. The Brillouin gain strongly depends on the structural parameters and the maximum value in the order of 106 W−1 m−1 is obtained in the slow light regime, which is more than two orders larger than that of the stand-alone strip and slot waveguides
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.
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