12,647 research outputs found
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 quark model has difficulties in
understanding the light scalar mesons below 1 GeV, scalar and axial-vector
charmed mesons and charmonium-like state . 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, and , 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 and 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 and
mesons. The 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 effects, we
obtain the masses of and mesons, for example,
,
with being
corrections. We find that the predicted mass difference of 48 MeV
between and is larger than that of MeV
inferred from the relativistic quark models, whereas the difference of 15 MeV
between the central values of and is much smaller than
the quark model expectation of 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
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