163 research outputs found
Gluon penguin enhancements to inclusive charmless decays of b quark in the 2HDM with flavor changing couplings
We calculate the enhancements to the inclusive charmless decays of b quark,
, from gluon penguin diagrams induced by the
charged and neutral Higgs bosons , and A^0) in the
Two-Higgs-Doublet Model with flavor-changing couplings. Within the considered
parameter space, the new contributions from charged Higgs boson are dominant.
After including the new contributions, the branching ratio (q^2
=0) can be increased form in the standard model to 4.4% and 2.6% in
the two-Higgs-doublet model for and 200 GeV, respectively. The
new contribution to the decay mode with q=(u,d,s) is,
however, numerically small and peaked at the lower q^2 region. The new
contribution to can also be neglected.Comment: Latex file, 14 pages with 6 PS or EPS figures. corrected some typos,
added new reference
Exclusive decays in the general two-Higgs-doublet models
By employing the QCD factorization approach, we calculated the
next-to-leading order new physics contributions to the branching ratios, CP
asymmetries, isospin and U-spin symmetry breaking of the exclusive decays (), induced by the charged Higgs penguins in the
general two-Higgs-doublet models. Within the considered parameter space, we
found that (a) the new physics corrections to the observables are generally
small in the model I and model III-A, moderate in model II, but large in model
III-B; (b) from the well measured branching ratios and upper limits, a lower
bound of \mhp > 200 GeV in model II was obtained, while the allowed range of
\mhp in model III-B is 226 \leq \mhp \leq 293 GeV; these bounds are
comparable with those from the inclusive decay; (c)the NLO
Wilson coefficient in model III-B is positive and disfavered by the
measured value of isospin symmetry breaking , but still can not be excluded if we take the large errors into
account; (d) the CP asymmetry \acp(B \to \rho \gamma) in model III-B has an
opposite sign with the one in the standard model (SM), which may be used as a
good observable to distinguish the SM from model III-B; (e) the isospin
symmetry breaking is less than 10% in the region of
preferred by the global fit result, but can be
as large as 20 to 40% in the regions of and . The SM and model III-B predictions for are
opposite in sign for small or large values of the CKM angles; (f) the U-spin
symmetry breaking in the SM and the general
two-Higgs-doublet models is generally small in size: .Comment: Revtex, 38 pages with 14 eps figures, minor correction
Charmless decays and the new physics effects in the minimal supergravity model
By employing the QCD factorization approach, we calculate the new physics
contributions to the branching radios of the two-body charmless
decays in the framework of the minimal supergravity (mSUGRA) model. Within the
considered parameter space, we find that (a) the supersymmetric (SUSY)
corrections to the Wilson coefficients () are very small and can
be neglected safely, but the leading order SUSY contributions to
and can be rather large and even change the
sign of the corresponding coefficients in the standard model; (b) the possible
SUSY contributions to those penguin-dominated decays in mSUGRA model can be as
large as ; (c) for the well measured decays, the
significant SUSY contributions play an important rule to improve the
consistency of the theoretical predictions with the data; (d) for decays, the theoretical predictions of the corresponding branching
ratios become consistent with the data within one standard deviation after the
inclusion of the large SUSY contributions in the mSUGRA model.Comment: 31 pages, Latex file, 4 ps and eps figures, minor corrections, final
version to appear in Physical Review
Optimal generalization of power filters for gravitational wave bursts, from single to multiple detectors
Searches for gravitational wave signals which do not have a precise model
describing the shape of their waveforms are often performed using power
detectors based on a quadratic form of the data. A new, optimal method of
generalizing these power detectors so that they operate coherently over a
network of interferometers is presented. Such a mode of operation is useful in
obtaining better detection efficiencies, and better estimates of the position
of the source of the gravitational wave signal. Numerical simulations based on
a realistic, computationally efficient hierarchical implementation of the
method are used to characterize its efficiency, for detection and for position
estimation. The method is shown to be more efficient at detecting signals than
an incoherent approach based on coincidences between lists of events. It is
also shown to be capable of locating the position of the source.Comment: 16 pages, 5 figure
An analysis on the convergence of equal-time commutators and the closure of the BRST algebra in Yang-Mills theories
In renormalizable theories, we define equal-time commutators (ETC'S) in terms
of the equal-time limit and investigate its convergence in perturbation theory.
We find that the equal-time limit vanishes for amplitudes with the effective
dimension d_{\em eff} \leq -2 and is finite for those with d_{\em eff} =-1
but without nontrivial discontinuity. Otherwise we expect divergent equal-time
limits. We also find that, if the ETC's involved in verifying an Jacobi
identity exist, the identity is satisfied.
Under these circumstances, we show in the Yang-Mills theory that the ETC of
the component of the BRST current with each other vanishes to all orders in
perturbation theory if the theory is free from the chiral anomaly, from which
we conclude that , where is the BRST charge. For the case
that the chiral anomaly is not canceled, we use various broken Ward identities
to show that is finite and vanishes
at the one-loop level and that they start to diverge at the two-loop level
unless there is some unexpected cancellation mechanism that improves the degree
of convergence.Comment: 35 page
Branching ratios and CP-violating asymmetries of decays in the general two-Higgs doublet models
Based on the low-energy effective Hamiltonian with the generalized
factorization, we calculate the new physics contributions to branching ratios
and CP-violating asymmetries of the charmless hadronic decays
in the standard model and the general two-Higgs doublet models (models I, II,
and III). Within the considered paramter space, we find the following. (a) In
models I and II, the new physics corrections are always small in size and will
be masked by other larger known theoretical uncertainties. (b) In model III,
the new physics corrections to the branching ratios of those QCD
penguin-dominated decays \ov B_s \to K^0\etapp, K^+ K^{-*}, etc., are large
in size and insensitive to the variations of \mhp and \nceff. For tree- or
electroweak penguin-dominated decay modes, however, the new physics corrections
are very small in size. (c) For \ov B_s \to K^+ K^{-*} and other seven decay
modes, the branching ratios are at the level of and will
be measurable at the future hadron colliders with large production. (d)
Among the studied thirty nine meson decay modes, seven of them can have a
CP-violating asymmetry larger than 20% in magnitude. The new
physics corrections are small or moderate in magnitude. (e) Because of its
large and \nceff stable branching ratio and CP violating asymmetry, the decay
\ov B_s \to K^+ K^{-*} seems to be the "best" channel to find CP violation of
system through studies of two-body charmless decays of meson.Comment: 39 pages, Revtex, 9 eps figures, final version accepted for
publication in Phys.Rev.
Charm multiplicity and the branching ratios of inclusive charmless b quark decays in the general two-Higgs-doublet models
In the framework of general two-Higgs-doublet models, we calculate the
branching ratios of various inclusive charmless b decays by using the low
energy effective Hamiltonian including next-to-leading order QCD corrections,
and examine the current status and the new physics effects on the determination
of the charm multiplicity and semileptonic branching ratio .
Within the considered parameter space, the enhancement to the ratio due to the charged-Higgs penguins can be as large as a factor of 8 (3) in
the model III (II), while the ratio can be increased from
the standard model prediction of 2.49% to 4.91% (2.99%) in the model III (II).
Consequently, the value of and can be decreased simultaneously
in the model III. The central value of will be lowered slightly by
about 0.003, but the ratio can be reduced significantly from the
theoretical prediction of in the SM to , for GeV, respectively. We find that
the predicted and the measured now agree within roughly one
standard deviation after taking into account the effects of gluonic charged
Higgs penguins in the model III with a relatively light charged Higgs boson.Comment: 25 pages, Latex file, axodraw.sty, 6 figures. Final version to be
published in Phys.Rev.
Giant superconducting fluctuations in the compensated semimetal FeSe at the BCS-BEC crossover
The physics of the crossover between weak-coupling BardeenâCooperâSchrieffer (BCS) and strong-coupling BoseâEinstein condensate (BEC) limits gives a unified framework of quantum-bound (superfluid) states of interacting fermions. This crossover has been studied in the ultracold atomic systems, but is extremely difficult to be realized for electrons in solids. Recently, the superconducting semimetal FeSe with a transition temperature Tc=8.5âK has been found to be deep inside the BCSâBEC crossover regime. Here we report experimental signatures of preformed Cooper pairing in FeSe, whose energy scale is comparable to the Fermi energies. In stark contrast to usual superconductors, large non-linear diamagnetism by far exceeding the standard Gaussian superconducting fluctuations is observed below T*âŒ20âK, providing thermodynamic evidence for prevailing phase fluctuations of superconductivity. Nuclear magnetic resonance and transport data give evidence of pseudogap formation at âŒT*. The multiband superconductivity along with electronâhole compensation in FeSe may highlight a novel aspect of the BCSâBEC crossover physics
Inelastic Rescattering and CP Asymmetries in D -> pi+ pi-, pi0 pi0
We study the direct CP violation induced by inelastic final state interaction
(FSI) rescattering in modes, and find that the resultant CP
asymmetry is about which is larger than in the K-system.
Our estimation is based on well-established theories and experiment measured
data, so there are almost no free parameters except the weak phase
in the CKM matrix.Comment: 9 page
B^0-\bar{B}^0 mixing and B \to X_s \gamma decay in the third type 2HDM: effects of NLO QCD contributions
In this paper, we calculated the next-to-leading order (NLO) new physics
contributions to the mass splitting \dmd and the branching ratio \brbxsga
induced by the charged Higgs loop diagrams in the third type of
two-Higgs-doublet models (model III) and draw the constraints on the free
parameters of model III. For the model III under consideration, we found that
(a) an upper limit |\ltt|\leq 1.7 is obtained from the precision data of
\dmd=0.502 \pm 0.007 ps^{-1}, while |\ltt| \approx 0.5 is favored
phenomenologicaly; (b) for decay, the NLO QCD contributions
tend to cancel the LO new physics contributions; (c) a light charged Higgs
boson with a mass around or even less than 200 GeV is still allowed at NLO
level by the measured branching ratio \brbxsga: numerically, 188 \leq \mh
\leq 215 GeV for (|\ltt|,|\lbb|)=(0.5,18); (d) the NLO QCD contributions
tend to cancel the LO contributions effectively, the lower limit on \mh is
consequently decreased by about 200 GeV; (e) the allowed region of \mh will
be shifted toward heavy mass end for a non-zero relative phase between
the Yukawa couplings \ltt and \lbb. The numerical results for the
conventional model II are also presented for the sake of a comparison.Comment: 42 pages, 18 eps figures, Revtex, new references adde
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