103,719 research outputs found
Ο± β 4Ο in chirally symmetric models
The decays rho0 β 2Ο+2Οβ and rho0 β 2Ο0Ο+Οβ are studied using various effective Lagrangians for Ο and rho (and in some case a1) mesons, all of which respect the approximate chiral symmetry of the strong interaction. Partial widths of the order of 1 keV or less are found in all cases. These are an order of magnitude smaller than recent predictions based on non-chiral models
Volume Dependence of Spectral Weights for Unstable Particles in a Solvable Model
Volume dependence of the spectral weight is usually used as a simple criteria
to distinguish single-particle states from multi-particle states in lattice QCD
calculations. Within a solvable model, the Lee model, we show that this
criteria is in principle only valid for a stable particle or a narrow
resonance. If the resonance being studied is broad, then the volume dependence
of the corresponding spectral weight resembles that of a multi-particle state
instead of a single-particle one. For an unstable -particle in the Lee
model, the transition from single-particle to multi-particle volume dependence
is governed by the ratio of its physical width to the typical level spacing in
the finite volume. We estimate this ratio for practical lattice QCD simulations
and find that, for most cases, the resonance studied in lattice QCD simulations
still resembles the single particle behavior.Comment: 15 pages, no figures. Title modified. Version to appear on Phys. Rev.
The Local Group: The Ultimate Deep Field
Near-field cosmology -- using detailed observations of the Local Group and
its environs to study wide-ranging questions in galaxy formation and dark
matter physics -- has become a mature and rich field over the past decade.
There are lingering concerns, however, that the relatively small size of the
present-day Local Group ( Mpc diameter) imposes insurmountable
sample-variance uncertainties, limiting its broader utility. We consider the
region spanned by the Local Group's progenitors at earlier times and show that
it reaches co-moving Mpc in linear size (a volume of ) at . This size at early cosmic epochs is large enough
to be representative in terms of the matter density and counts of dark matter
halos with . The Local
Group's stellar fossil record traces the cosmic evolution of galaxies with
(reaching
at ) over a region that is comparable to or larger than
the Hubble Ultra-Deep Field (HUDF) for the entire history of the Universe. It
is highly complementary to the HUDF, as it probes much fainter galaxies but
does not contain the intrinsically rarer, brighter sources that are detectable
in the HUDF. Archaeological studies in the Local Group also provide the ability
to trace the evolution of individual galaxies across time as opposed to
evaluating statistical connections between temporally distinct populations. In
the JWST era, resolved stellar populations will probe regions larger than the
HUDF and any deep JWST fields, further enhancing the value of near-field
cosmology.Comment: 6 pages, 5 figures; MNRAS Letters, in pres
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