Masses of Scalar and Axial-Vector B Mesons Revisited

The SU(3) quark model encounters a great challenge in describing even-parity mesons. Specifically, the $q\bar q$ quark model has difficulties in understanding the light scalar mesons below 1 GeV, scalar and axial-vector charmed mesons and $1^+$ charmonium-like state $X(3872)$. A common wisdom for the resolution of these difficulties lies on the coupled channel effects which will distort the quark model calculations. In this work, we focus on the near mass degeneracy of scalar charmed mesons, $D_{s0}^*$ and $D_0^{*0}$, and its implications. Within the framework of heavy meson chiral perturbation theory, we show that near degeneracy can be qualitatively understood as a consequence of self-energy effects due to strong coupled channels. Quantitatively, the closeness of $D_{s0}^*$ and $D_0^{*0}$ masses can be implemented by adjusting two relevant strong couplings and the renormalization scale appearing in the loop diagram. Then this in turn implies the mass similarity of $B_{s0}^*$ and $B_0^{*0}$ mesons. The $P_0^* P'_1$ interaction with the Goldstone boson is crucial for understanding the phenomenon of near degeneracy. Based on heavy quark symmetry in conjunction with corrections from QCD and $1/m_Q$ effects, we obtain the masses of $B^*_{(s)0}$ and $B'_{(s)1}$ mesons, for example, $M_{B_{s0}^*}= (5715\pm1)\,{\rm MeV}+\delta\Delta_S$, $M_{B'_{s1}}=(5763\pm1)\,{\rm MeV}+\delta\Delta_S$ with $\delta\Delta_S$ being $1/m_Q$ corrections. We find that the predicted mass difference of 48 MeV between $B'_{s1}$ and $B_{s0}^*$ is larger than that of $20\sim 30$ MeV inferred from the relativistic quark models, whereas the difference of 15 MeV between the central values of $M_{B'_{s1}}$ and $M_{B'_1}$ is much smaller than the quark model expectation of $60-100$ MeV.Comment: 21 pages, 1 figure, to appear in Eur. Phys. J. (2017). arXiv admin note: text overlap with arXiv:1404.377

Self-interacting Dark Matter Benchmarks

Dark matter self-interactions have important implications for the distributions of dark matter in the Universe, from dwarf galaxies to galaxy clusters. We present benchmark models that illustrate characteristic features of dark matter that is self-interacting through a new light mediator. These models have self-interactions large enough to change dark matter densities in the centers of galaxies in accord with observations, while remaining compatible with large-scale structure data and all astrophysical observations such as halo shapes and the Bullet Cluster. These observations favor a mediator mass in the 10 - 100 MeV range and large regions of this parameter space are accessible to direct detection experiments like LUX, SuperCDMS, and XENON1T.Comment: 4 pages, white paper for Snowmass 2013; v2: finalized version, figures correcte

Dark Matter Halos as Particle Colliders: A Unified Solution to Small-Scale Structure Puzzles from Dwarfs to Clusters

Astrophysical observations spanning dwarf galaxies to galaxy clusters indicate that dark matter (DM) halos are less dense in their central regions compared to expectations from collisionless DM N-body simulations. Using detailed fits to DM halos of galaxies and clusters, we show that self-interacting DM (SIDM) may provide a consistent solution to the DM deficit problem across all scales, even though individual systems exhibit a wide diversity in halo properties. Since the characteristic velocity of DM particles varies across these systems, we are able to measure the self-interaction cross section as a function of kinetic energy and thereby deduce the SIDM particle physics model parameters. Our results prefer a mildly velocity-dependent cross section, from $\sigma/m \simeq 2\; {\rm cm^2/g}$ on galaxy scales to $\sigma/m \simeq 0.1\; {\rm cm^2/g}$ on cluster scales, consistent with the upper limits from merging clusters. Our results dramatically improve the constraints on SIDM models and may allow the masses of both DM and dark mediator particles to be measured even if the dark sector is completely hidden from the Standard Model, which we illustrate for the dark photon model.Comment: 5 pages, 3 figure