24,071 research outputs found
Indications of the possible observation of the lowest-lying 1^{-+} QCD state
We discuss properties of 1^{-+} exotic mesons within the framework of the QCD
field-theoretic approach. We estimate the mass of the lowest-lying 1^{-+}
exotic meson using renormalization-improved QCD sum rules, and find that the
mass lies around GeV, in good agreement with the
data. This state should be expected in QCD. We find that the mass for the
lowest-lying strange 1^{-+} meson is GeV. Our result hints that
the K^*(1410) may be the lowest-lying 1^{-+} nonet state.Comment: 6 pages, 3 figures; some typos corrected, Published versio
Thermodynamic Evolution of Secluded Vector Dark Matter: Conventional WIMPs and Nonconventional WIMPs
The secluded dark matter resides within a hidden sector and self-annihilates
into lighter mediators which subsequently decay to the Standard Model (SM)
particles. Depending on the coupling strength of the mediator to the SM, the
hidden sector can be kinetically decoupled from the SM bath when the
temperature drops below the mediator's mass, and the dark matter annihilation
cross section at freeze-out is thus possible to be boosted above the
conventional value of weak interacting massive particles. We present a
comprehensive study on thermodynamic evolution of the hidden sector from the
first principle, using the simplest secluded vector dark matter model.
Motivated by the observation of Galactic center gamma-ray excess, we take two
mass sets for the dark matter and mediator as
examples to illustrate the thermodynamics. The coupled Boltzmann moment
equations for number densities and temperature evolutions of the hidden sector
are numerically solved. The formalism can be easily extended to a general
secluded dark matter model. We show that a long-lived mediator can result in a
boosted dark matter annihilation cross section to account for the relic
abundance. We further show the parameter space which provides a good fit to the
Galactic center excess data and is compatible with the current bounds and
LUX-ZEPLIN projected sensitivity. We find that the future observations of dwarf
spheroidal galaxies offer promising reach to probe the most relic allowed
parameter space relevant to the boosted dark matter annihilation cross section.Comment: 51 pages, 15 figures; typos corrected in (42), (45) and (46); in the
text and caption of Fig. 6, variations of the local density and inner slope
of the halo corrected to be consistent with the plot
Pseudoscalar and Scalar Operators of Higgs-Penguins in the MSSM and B to phi K^*, K eta(') Decays
We study the effect of b to s sbar s scalar/pseudoscalar operators in B to K
eta('), phi K^* decays. In the minimal supersymmetric standard model (MSSM),
such scalar/pseudoscalar operators can be induced by the penguin diagrams of
neutral Higgs bosons. These operators can be Fierz-transformed into tensor
operators, and the resultant tensor operators could affect the transverse
polarization amplitudes in B to phi K^* decays. A combined analysis of the
decays B to phi K^* and B to K eta('), including b to s sbar s
scalar/pseudoscalar operators and their Fierz-transformed tensor operators
originated from the MSSM, is performed. Our study is based on the followings:
(1) Assuming that weak annihilations in B to phi K^* is negligible and the
polarization puzzle is resolved by Fierz-transformed tensor operators, it
results in too large coefficients of scalar/pseudoscalar operators, such that
the resulting B to K eta(') branching fractions are much larger than
observations. (2) When we take the weak annihilations in B to phi K^* into
account, the polarization puzzle can be resolved. In this case, new physics
effects are strongly suppressed and no more relevant to the enhancement of the
transverse modes in B to phi K^* decays.Comment: 27 pages, 3 figures; (v2) data and results updated, typos correcte
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