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 $1.26\pm 0.15$ GeV, in good agreement with the $\pi_1(1400)$ data. This state should be expected in QCD. We find that the mass for the lowest-lying strange 1^{-+} meson is $1.31\pm 0.19$ 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 $\sim{\cal O}(80\, \text{GeV})$ 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

Branching Ratios and CP Asymmetries of B \to a_1(1260) \pi and a_1(1260) K Decays

We present the studies of the decays $B\to a_1(1260) \pi$ and $a_1(1260) K$ within the framework of QCD factorization. Due to the G-parity, unlike the vector meson, the chiral-odd two-parton light-cone distribution amplitudes of the $a_1$ are antisymmetric under the exchange of quark and anti-quark momentum fractions in the SU(2) limit. The branching ratios for $a_1 \pi$ modes are sensitive to tree--penguin interference. The resultant ${\cal B}(B^0 \to a_1^\pm \pi^\mp)$ are in good agreement with the data. However, using the current Cabibbo--Kobayashi--Maskawa angles, $\beta=22.0^\circ$ and $\gamma=59.0^\circ$, our results for the mixing-induced parameter $S$ and $\alpha_{\rm eff}$ differ from the measurements of the time-dependent CP asymmetries in the decay $B^0\to a_1^\pm \pi^\mp$ at about the $3.7\sigma$ level. This puzzle may be resolved by using a larger $\gamma \gtrsim 80^\circ$. For $a_1 K$ modes, the annihilation topologies give sizable contributions and are sensitive to the first Gegenbauer moment of the leading-twist tensor (chiral-odd) distribution amplitude of the $a_1$ meson. The $B\to a_1 K$ amplitudes resemble the corresponding $B\to \pi K$ ones very much. Taking the ratios of corresponding CP-averaged $a_1 K$ and $\pi K$ branching ratios, we can extract information relevant to the electroweak penguins and annihilations. The existence of new-physics in the electroweak penguin sector and final state interactions during decays can thus be explored.Comment: 20 pages, 1 figure, 4 tables, typos corrected, some discussions added, version to appear in PR