21,547 research outputs found
The study of light invisible particles in decays
In this paper, we study the light scalar and pseudoscalar invisible particles
in the flavor changing neutral current processes of the meson. Effective
operators are introduced to describe the couplings between quarks and light
invisible particles. The Wilson coefficients are extracted from the
experimental results of the and mesons, which are used to predict the
upper limits of the branching fractions of the similar decay processes for the
meson. The hadronic transition matrix element is calculated with the
instantaneously approximated Bethe-Salpeter method. The upper limits of the
branching fractions when taking different values are presented. It is
found that at some region of , the channel has the largest upper limit which is of the order of
, and for , the largest value of the
upper limits can achieve the order of . Other decay modes, such as
and ,
are also considered.Comment: 24 pages, 35 figure
Strong Decays of the Orbitally Excited Scalar Mesons
We calculate the two-body strong decays of the orbitally excited scalar
mesons and by using the relativistic Bethe-Salpeter
(BS) method. was observed recently by the LHCb Collaboration, the
quantum number of which has not been determined yet. In this paper, we assume
that it is the state and obtain the transition amplitude by using the
PCAC relation, low-energy theorem and effective Lagrangian method. For the
state, the total widths of and are 226 MeV
and 246 MeV, respectively. With the assumption of state, the widths
of and are both about 131 MeV, which is close
to the present experimental data. Therefore, is a strong
candidate for the state.Comment: 21 pages, 10 figure
A Fast Sensitivity-Based Preventive Control Selection Method for Online Voltage Stability Assessment
- β¦