4,653 research outputs found
The NLO contributions to the scalar pion form factors and the annihilation corrections to the decays
In this paper, by employing the factorization theorem, we made the
first calculation for the space-like scalar pion form factor at
the leading order (LO) and the next-to-leading order (NLO) level, and then
found the time-like scalar pion form factor by analytic
continuation from the space-like one. From the analytical evaluations and the
numerical results, we found the following points: (a) the NLO correction to the
space-like scalar pion form factor has an opposite sign with the LO one but is
very small in magnitude, can produce at most decrease to LO result in
the considered region; (b) the NLO time-like scalar pion form factor
describes the contribution to the
factorizable annihilation diagrams of the considered decays,
i.e. the NLO annihilation correction; (c) the NLO part of the form factor
is very small in size, and is almost independent with the
variation of cutoff scale , but this form factor has a large strong
phase around and may play an important role in producing large CP
violation for decays; and (d) for and decays, the newly known NLO annihilation correction can produce
only a very small enhancement to their branching ratios, less than in
magnitude, and therefore we could not interpret the well-known -puzzle
by the inclusion of this NLO correction to the factorizable annihilation
diagrams.Comment: 26 pages, 12 figures, 1 Table; Minor correction
Systematic study of proton radioactivity of spherical proton emitters within various versions of proximity potential formalisms
In this work we present a systematic study of the proton radioactivity
half-lives of spherical proton emitters within the Coulomb and proximity
potential model. We investigate 28 different versions of the proximity
potential formalisms developed for the description of proton radioactivity,
decay and heavy particle radioactivity. It is found that 21
of them are not suitable to deal with the proton radioactivity, because the
classical turning points cannot be obtained due to the fact
that the depth of the total interaction potential between the emitted proton
and the daughter nucleus is above the proton radioactivity energy. Among the
other 7 versions of the proximity potential formalisms, it is Guo2013 which
gives the lowest rms deviation in the description of the experimental
half-lives of the known spherical proton emitters. We use this proximity
potential formalism to predict the proton radioactivity half-lives of 13
spherical proton emitters, whose proton radioactivity is energetically allowed
or observed but not yet quantified, within a factor of 3.71.Comment: 10 pages, 5 figures. This paper has been accepted by The European
Physical Journal A (in press 2019
Anatomy of decays and effects of next-to-leading order contributions in the perturbative QCD factorization approach
In this paper, we will make systematic calculations for the branching ratios
and the CP-violating asymmetries of the twenty one decays
by employing the perturbative QCD (PQCD) factorization approach. Besides the
full leading-order (LO) contributions, all currently known next-to-leading
order (NLO) contributions are taken into account. We found numerically that:
(a) the NLO contributions can provide enhancement to the LO PQCD
predictions for and , or a reduction to
\calb(\bar{B}_s^0 \to \pi^{-} K^{*+}), and we confirmed that the inclusion of
the known NLO contributions can improve significantly the agreement between the
theory and those currently available experimental measurements, (b) the total
effects on the PQCD predictions for the relevant transition form
factors after the inclusion of the NLO twist-2 and twist-3 contributions is
generally small in magnitude: less than enhancement respect to the
leading order result, (c) for the "tree" dominated decay and the "color-suppressed-tree" decay ,
the big difference between the PQCD predictions for their branching ratios are
induced by different topological structure and by interference effects among
the decay amplitude and : constructive for the
first decay but destructive for the second one, and (d) for \bar{B}_s^0 \to
V(\eta, \etar) decays, the complex pattern of the PQCD predictions for their
branching ratios can be understood by rather different topological structures
and the interference effects between the decay amplitude \cala(V\eta_q) and
\cala(V\eta_s) due to the \eta-\etar mixing.Comment: 18 pages, 2 figures, 3 tables. Some modifications of the text.
Several new references are adde
Time-like pion electromagnetic form factors in kT factorization with the next-to-leading-order twist-3 contribution
AbstractWe calculate the time-like pion electromagnetic form factor in the kT factorization formalism with the inclusion of the next-to-leading-order (NLO) corrections of the leading-twist and sub-leading-twist contributions. It's found that the total NLO correction can enhance (reduce) the magnitude (strong phase) of the leading order form factor by 20%–30% (<15°) in the considered invariant mass squared q2>5 GeV2, and the NLO twist-3 correction plays the key role to narrow the gap between the pQCD predictions and the measured values for the time-like pion electromagnetic form factor
Titanium Trisulfide Monolayer: Theoretical Prediction of a New Direct-Gap Semiconductor with High and Anisotropic Carrier Mobility
A new two-dimensional (2D) layered material, namely, titanium trisulfide (TiS3) monolayer, is predicted to possess novel electronic properties. Ab initio calculations show that the perfect TiS3 monolayer is a direct-gap semiconductor with a bandgap of 1.02 eV, close to that of bulk silicon, and with high carrier mobility. More remarkably, the in-plane electron mobility of the 2D TiS3 is highly anisotropic, amounting to about 10,000 cm2 V−1 s−1 in the b direction, which is higher than that of the MoS2 monolayer, whereas the hole mobility is about two orders of magnitude lower. Furthermore, TiS3 possesses lower cleavage energy than graphite, suggesting easy exfoliation for TiS3. Both dynamical and thermal stability of the TiS3 monolayer is examined by phonon-spectrum calculation and Born–Oppenheimer molecular dynamics simulation. The desired electronic properties render the TiS3 monolayer a promising 2D atomic-layer material for applications in future nanoelectronics.
Includes Supplemental Materials (Fig. S1
- …