393 research outputs found
The semileptonic and radiative decays within the light-cone sum rules
The measured branching ratio of the meson semileptonic decay , which is based on the CLEO data taken at the
peak of resonance, disagrees with the traditional SVZ sum rules
analysis by about three times. In the paper, we show that this discrepancy can
be eliminated by applying the QCD light-cone sum rules (LCSR) approach to
calculate the transition form factors and .
After extrapolating the LCSR predictions of these TFFs to whole -region,
we obtain . Using the CKM matrix
element and the lifetime from the Particle Data Group, we obtain
and , which agree with the CLEO measurements within errors. We
also calculate the branching ratios of the two meson radiative processes
and obtain and , which also agree with the Belle measurements within errors. Thus we
think the LCSR approach is applicable for dealing with the meson decays.Comment: 12 pages, 7 figures, version to be published in EPJ
Neutron Scattering off One-Neutron Halo Nuclei in Halo Effective Field Theory
Neutron scattering off neutron halos can provide important information about
the internal structure of nuclei close to the neutron drip line. In this work,
we use halo effective field theory to study the -wave scattering of a
neutron and the spin-parity one-neutron halo nuclei
, , and at leading order. In the
channel, the only inputs to the Faddeev equations are their one-neutron
separation energies. In the channel, the neutron-neutron scattering
length and the two-neutron separation energies of ,
and enter as well. The numerical results show that the total
-wave cross sections in the channel at threshold are of the order of a
few barns. In the channel, these cross sections are of the order of a few
barns for - and - scattering, and about 60 for the - scattering. The appearance of a pole in
close to zero in all three cases indicates the existence of a
virtual Efimov state close to threshold in each of the , , and systems. Observation of this pole would confirm the
presence of Efimov physics in halo nuclei. The dependence of the results on the
neutron-core scattering length is also studied
Investigating decay process within QCD sum rule approach
In this paper, the semileptonic decays with
are investigated by using the light-cone sum rule approach.
Firstly, the neutral meson mixing scheme between , ,
and pseudoscalar gluonium is discussed in a unified way, which leads to the
direct connection between two different channels for and by the
mixing angle. Then we calculated the transition form factors
(TFFs) within QCD light-cone sum rule approach up to next-to-leading order
correction. At the large recoil point, we have
and
. Furthermore, the TFFs are
extrapolated to the whole physical -region by using the simplified
-series expansion. The behaviors of TFFs and related three angular
coefficient functions , and
are given. The differential decay widths for with respect to and are
displayed, and also lead to the branching fractions and . These results show well
agreement with the recent BESIII measurements and theoretical predictions. Then
the differential distributions and integrated predictions for three angular
observables, {\it i.e.} forward-backward asymmetries, -differential flat
terms and lepton polarization asymmetry are given separately. Lastly, we
estimate the ratio for different decay channels .Comment: 10 pages, 5 figure
Minimal-time Deadbeat Consensus and Individual Disagreement Degree Prediction for High-order Linear Multi-agent Systems
In this paper, a Hankel matrix-based fully distributed algorithm is proposed
to address a minimal-time deadbeat consensus prediction problem for
discrete-time high-order multi-agent systems (MASs). Therein, each agent can
predict the consensus value with the minimum number of observable historical
outputs of its own. Accordingly, compared to most existing algorithms only
yielding asymptotic convergence, the present method can attain deadbeat
consensus instead. Moreover, based on the consensus value prediction, instant
individual disagreement degree value of MASs can be calculated in advance as
well. Sufficient conditions are derived to guarantee both the minimal-time
deadbeat consensus and the instant individual disagreement degree prediction.
Finally, both the effectiveness and superiority of the proposed deadbeat
consensus algorithm are substantiated by numerical simulations.Comment: 12 pages, 3 figure
helicity form factors and the decays
In this paper, we calculate the helicity form factors (HFFs)
up to twist-4 accuracy by using the light-cone sum rules (LCSR) approach. After
extrapolating those HFFs to the physically allowable region, we
investigate the -meson two-body decays and semi-leptonic decays with stands for light
pseudoscalar/vector meson, respectively. The branching fractions can be derived
by using the CKM matrix element and the lifetime from the Particle Data
Group, and we obtain , , , , and . We then obtain and , which agree with the LHCb measured value within
-error. We also obtain ,
which like other theoretical predictions, is consistent with the LHCb measured
value within -error. Those imply that the HFFs under the LCSR approach
are also applicable to the meson two-body decays and semi-leptonic
decays , and the HFFs obtained by
using LCSR in a new way implies that there may be new physics in the semi-leptonic decays.Comment: 10 pages, 4 figures, published versio
Update on strong and radiative decays of the and and their bottom cousins
The isospin breaking and radiative decay widths of the positive-parity
charm-strange mesons, and , and their predicted
bottom-strange counterparts, and , as hadronic molecules
are revisited. This is necessary, since the and masses
used in Eur. Phys. J. A 50 (2014) 149 were too small, in conflict with the
heavy quark flavour symmetry. Furthermore, not all isospin breaking
contributions were considered. We here present a method to restore heavy quark
flavour symmetry, correcting the masses of and , and
include the complete isospin breaking contributions up to next-to-leading
order. With this we provide updated hadronic decay widths for all of
, , and . Results for the partial
widths of the radiative deays of and are also
renewed in light of the much more precisely measured width. We find
that and are the preferred channels for searching for
and , respectively.Comment: 5 pages, 2 figure
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