1,205 research outputs found
The Scalar Sector in 331 Models
We calculate the exact tree-level scalar mass matrices resulting from
symmetry breaking using the most general gauge-invariant scalar potential of
the 331 model, both with and without the condition that lepton number is
conserved. Physical masses are also obtained in some cases, as well as
couplings to standard and exotic gauge bosons.Comment: LaTex, 15 page
Derived Subgroups of Fixed Points in Profinite Groups
The main result of this paper is the following theorem. Let q be a prime, A
an elementary abelian group of order q^3. Suppose that A acts as a coprime
group of automorphisms on a profinite group G in such a manner that C_G(a)' is
periodic for each nontrivial element a in A. Then G' is locally finite.Comment: To appear in Glasgow Mathematical Journal (2011). 11 page
B Mixing
The neutral mesons, and , can oscillate between their particle
and antiparticle states owing to flavor-changing weak interactions. In recent
years, techniques to detect these oscillations as a function of the meson's
decay time have been developed. In this article the physics of flavor
oscillations is reviewed and theoretical predictions are summarized. The many
observations that demonstrate the time-dependence of B^0-\B0bar oscillations
are presented along with a combined measurement of its frequency, .
The attempts to measure the oscillation frequency, both directly and
indirectly, are then summarized. Finally, values for the CKM elements
and are extracted
Demonstration of a Lightguide Detector for Liquid Argon TPCs
We report demonstration of light detection in liquid argon using an acrylic
lightguide detector system. This opens the opportunity for development of an
inexpensive, large-area light collection system for large liquid argon time
projection chambers. The guides are constructed of acrylic, with TPB embedded
in a surface coating with a matching index of refraction. We study the response
to early scintillation light produced by a 5.3 MeV alpha. We measure coating
responses from 7 to 8 PE on average, compared to an ideal expectation of 10 PE
on average. We estimate the attenuation length of light along the lightguide
bar to be greater than 0.5 m. The coating response and the attenuation length
can be improved; we show, however, that these results are already sufficient
for triggering in a large detector
Composite Scalars at LEP: Constraining Technicolor Theories
LEPI and LEPII data can be used to constrain technicolor models with light,
neutral pseudo-Nambu-Goldstone bosons, Pa. We use published limits on branching
ratios and cross sections for final states with photons, large missing energy,
jet pairs, and b bbar pairs to constrain the anomalous Pa Z0 Z0, Pa Z0 photon,
and Pa photon photon couplings. From these results, we derive bounds on the
size of the technicolor gauge group and the number of technifermion doublets in
models such as Low-scale Technicolor.Comment: 27 pages (including title page), 15 figures, 6 tables. version 2: In
addressing PRD referee comments, we have significantly expanded our
manuscript, to include detailed discussion of limits from LEP II data, as
well as expanding the number or specific models to which we apply our
results. As a result, we have changed the title from "Z0 decays to composite
scalars: constraining technicolor theories
Consequences of t-channel unitarity for the interaction of real and virtual photons at high energies
We analyze the consequences of t-channel unitarity for photon cross sections
and show what assumptions are necessary to allow for the existence of new
singularities at for the and total
cross sections. For virtual photons, such singularities can in general be
present, but we show that, apart from the perturbative singularity associated
with , no new ingredient is needed to
reproduce the data from LEP and HERA, in the Regge region.Comment: 10 pages, LaTeX2e with kluwer.sty, 7 figures. Talk presented at the
Second International "Cetraro" Workshop & NATO Advanced Research Workshop
"Diffraction 2002", Alushta, Crimea, Ukraine, August 31 - September 6, 200
When should PIC simulations be applied to atmospheric pressure plasmas? Impact of correlation heating
Molecular dynamics simulations are used to test when the particle-in-cell
(PIC) method applies to atmospheric pressure plasmas. It is found that PIC
applies only when the plasma density and macroparticle weight are sufficiently
small because of two effects associated with correlation heating. The first is
the physical effect of disorder-induced heating (DIH). This occurs if the
plasma density is large enough that a species (typically ions) is strongly
correlated in the sense that the Coulomb coupling parameter exceeds one. In
this situation, DIH causes ions to rapidly heat following ionization. PIC is
not well suited to capture DIH because doing so requires using a macroparticle
weight of one and a grid that well resolves the physical interparticle spacing.
These criteria render PIC intractable for macroscale domains. The second effect
is a numerical error due to Artificial Correlation Heating (ACH). ACH is like
DIH in that it is caused by the Coulomb repulsion between particles, but
differs in that it is a numerical effect caused by a macroparticle weight
larger than one. Like DIH, it is associated with strong correlations. However,
here the macroparticle coupling strength is found to scale as ,
where is the physical coupling strength and is the macroparticle
weight. So even if the physical coupling strength of a species is small, as is
expected for electrons in atmospheric pressure plasmas, a sufficiently large
macroparticle weight can cause the macroparticles to be strongly coupled and
therefore heat due to ACH. Furthermore, it is shown that simulations in reduced
dimensions exacerbate these issues
Early phylogenetic estimate of the effective reproduction number of SARS-CoV-2
To reconstruct the evolutionary dynamics of the 2019 novel-coronavirus recently causing an outbreak in Wuhan, China, 52 SARS-CoV-2 genomes available on 4 February 2020 at Global Initiative on Sharing All Influenza Data were analyzed. The two models used to estimate the reproduction number (coalescent-based exponential growth and a birth-death skyline method) indicated an estimated mean evolutionary rate of 7.8
7 10 124 subs/site/year (range, 1.1
7 10 124-15
7 10 124) and a mean tMRCA of the tree root of 73 days. The estimated R value was 2.6 (range, 2.1-5.1), and increased from 0.8 to 2.4 in December 2019. The estimated mean doubling time of the epidemic was between 3.6 and 4.1 days. This study proves the usefulness of phylogeny in supporting the surveillance of emerging new infections even as the epidemic is growing
On verbal subgroups in finite and profinite groups
Let w be a multilinear commutator word. In the present paper we describe recent results that show that if G is a profinite group in which all w-values are contained in a union of finitely (or in some cases countably) many subgroups with a prescribed property, then the verbal subgroup w(G) has the same property as well. In particular, we show this in the case where the subgroups are periodic or of finite rank
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