1,620 research outputs found
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
Model independent bounds on the tau lepton electromagnetic and weak magnetic moments
Using LEP1, SLD and LEP2 data, for tau lepton production, and data from CDF,
D0 and LEP2, for W decays into tau leptons, we set model independent limits on
non-standard electromagnetic and weak magnetic moments of the tau lepton. The
most general effective Lagrangian giving rise to tau moments is used without
further assumptions. Precise bounds () on the non-standard model
contributions to tau electromagnetic (), tau Z-magnetic
() and tau W-magnetic ()
dipole moments are set from the analysis.Comment: 19 pages, 2 figures, elsart.sty. Revised version with new data.
Accepted for publication in Nucl. Phys.
Bounds on the Tau Magnetic Moments: Standard Model and Beyond
We obtain new bounds for the magnetic dipole moments of the tau lepton. These
limits on the magnetic couplings of the tau to the electroweak gauge bosons
(gamma, W, Z) are set in a model independent way using the most general
effective Lagrangian with the SU(2)_L x U(1)_Y symmetry. Comparison with data
from the most precise experiments at high energies shows that the present
limits are more stringent than the previous published ones. For the anomalous
magnetic moment the bounds are, for the first time, within one order of
magnitude of the standard model prediction.Comment: 8 pages, 1 figure; to appear in the proceedings of the 6th
International Workshop on Tau Lepton Physics, 18-21 September (2000),
Victoria (Canada
Analytic Perturbation Theory: A New Approach to the Analytic Continuation of the Strong Coupling Constant into the Timelike Region
The renormalization group applied to perturbation theory is ordinarily used
to define the running coupling constant in the spacelike region. However, to
describe processes with timelike momenta transfers, it is important to have a
self-consistent determination of the running coupling constant in the timelike
region. The technique called analytic perturbation theory (APT) allows a
consistent determination of this running coupling constant. The results are
found to disagree significantly with those obtained in the standard
perturbative approach. Comparison between the standard approach and APT is
carried out to two loops, and threshold matching in APT is applied in the
timelike region.Comment: 16 pages, REVTeX, 7 postscript figure
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
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
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
First Tests of a New Fast Waveform Digitizer for PMT Signal Read-out from Liquid Argon Dark Matter Detectors
Abstract A new generation Waveform Digitizer board as been recently made available on the market by CAEN. The new board CAEN V1751 with 8 Channels per board, 10 bit, 1 GS/s Flash ADC Waveform Digitizer (or 4 channel, 10 bit, 2 GS/s Flash ADC Waveform Digitizer -Dual Edge Sampling mode) with threshold and Auto-Trigger capabilities provides an ideal (relatively low-cost) solution for reading signals from liquid Argon detectors for Dark Matter search equipped with an array of PMTs for the detection of scintillation light. The board was extensively used in real experimental conditions to test its usefulness for possible future uses and to compare it with a state of the art digital oscilloscope. As results, PMT Signal sampling at 1 or 2 GS/s is appropriate for the reconstruction of the fast component of the signal scintillation in Argon (characteristic time of about 4 ns) and the extended dynamic range, after a small customization, allows for the detection of signals in the range of energy needed. The bandwidth is found to be adequate and the intrinsic noise is very low
Probing the Higgs Field Using Massive Particles as Sources and Detectors
In the Standard Model, all massive elementary particles acquire their masses
by coupling to a background Higgs field with a non-zero vacuum expectation
value. What is often overlooked is that each massive particle is also a source
of the Higgs field. A given particle can in principle shift the mass of a
neighboring particle. The mass shift effect goes beyond the usual perturbative
Feynman diagram calculations which implicitly assume that the mass of each
particle is rigidly fixed. Local mass shifts offer a unique handle on Higgs
physics since they do not require the production of on-shell Higgs bosons. We
provide theoretical estimates showing that the mass shift effect can be large
and measurable, especially near pair threshold, at both the Tevatron and the
LHC.Comment: 6 pages, no figures; Version 2 corrects some typographical errors of
factors of 2 in equations 14, 17, 18 and 19 (all of the same origin) and
mentions a linear collider as an interesting place to test the results of
this pape
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