3,263 research outputs found
Deconstructing the Antlia cluster core
The present literature does not give a satisfactory answer to the question
about the nature of the "Antlia galaxy cluster". The radial velocities of
galaxies found in the region around the giant ellipticals NGC 3258/3268 range
from about 1000 km/s to 4000 km/s. We characterise this region and its possible
kinematical and population substructure. We have obtained VLT--VIMOS
multi-object spectra of the galaxy population in the inner part of the Antlia
cluster and measure radial velocities for 45 potential members. We supplement
our galaxy sample with literature data, ending up with 105 galaxy velocities.
We find a large radial velocity dispersion for the entire sample as reported in
previous papers. However, we find three groups at about 1900 km/s, 2800 km/s,
and 3700 km/s, which we interpret as differences in the recession velocities
rather than peculiar velocities. The high radial velocity dispersion of
galaxies in the Antlia region reflects a considerable extension along the line
of sight.Comment: 11 pages, 7 figures, accepted in A&
Treatment of the background error in the statistical analysis of Poisson processes
The formalism that allows to take into account the error sigma_b of the
expected mean background b in the statistical analysis of a Poisson process
with the frequentistic method is presented. It is shown that the error sigma_b
cannot be neglected if it is not much smaller than sqrt(b). The resulting
confidence belt is larger that the one for sigma_b=0, leading to larger
confidence intervals for the mean mu of signal events.Comment: 15 pages including 2 figures, RevTeX. Final version published in
Phys. Rev. D 59 (1999) 11300
Review of Recent Searches for Rare and Forbidden Dilepton Decays of Charmed Mesons
I briefly review the results of recent searches for flavor-changing neutral
current and lepton-flavor and lepton-number violating decays of D+, Ds, and D0
mesons (and their antiparticles) into modes containing muons and electrons. The
primary focus is the results from Fermilab charm hadroproduction experiment
E791. E791 examined 24 pi,l,l and K,l,l decay modes of D+ and Ds and l+l- decay
modes of D0. Limits presented by E791 for 22 rare and forbidden dilepton decays
of D mesons were more stringent than those obtained from previous searches, or
else were the first reported.Comment: 8 pages, 1 figure, uses psfig.sty and RevTeX, submitted to Modern
Physics Letters A, based on a Fermilab "Joint Theoretical and Experimental"
tal
Top mixing in effective theories
We review how top mixing with light quarks constrains new physics beyond the
Standard Model using the effective Lagrangian approach.Comment: 4 pages, contribution to Workshop "Loops and Legs in Quantum Field
Theory", April 200
Homocysteine treatment alters redox capacity of both endothelial and tumor cells
Homocysteine is a non-proteinogenic amino acid playing key roles in two interconnected metabolic pathways, namely, the activated methyl cycle and the linear trans-sulfuration pathway that allows the conversion of methionine to cysteine. A dysregulation of intracellular homocysteine metabolism could yield an increased export of this amino acid, leading to hyperhomocysteinemia, which has been associated with an increased risk of cardiovascular diseases. In spite of decades of experimental effort, there is no definitive consensus on what could be the molecular mechanisms whereby hyperhomocysteinemia could contribute to cardiovascular disease. The redox active nature of homocysteine has favored the idea of an induction of oxidative stress as the underlying mechanism of homocysteine toxicity. In contrast, homocysteine can also behave as an anti-oxidant. The present work is aimed to further analyze the capacity of homocysteine to modulate the redox capacity of both endothelial and tumor cells.
[Our experimental work is supported by grants BIO2014-56092-R (MINECO and FEDER) and P12-CTS-1507 (Andalusian Government and FEDER) and funds from group BIO-267 (Andalusian Government). The "CIBER de Enfermedades Raras" is an initiative from the ISCIII (Spain)].Universidad de MĂĄlaga. Campus de Excelencia Internacional AndalucĂa Tech
The Hagedorn temperature Revisited
The Hagedorn temperature, T_H is determined from the number of hadronic
resonances including all mesons and baryons. This leads to a stable result T_H
= 174 MeV consistent with the critical and the chemical freeze-out temperatures
at zero chemical potential. We use this result to calculate the speed of sound
and other thermodynamic quantities in the resonance hadron gas model for a wide
range of baryon chemical potentials following the chemical freeze-out curve. We
compare some of our results to those obtained previously in other papers.Comment: 13 pages, 4 figure
Phases and Amplitudes in Inclusive and Decays
In inclusive decays of the (3097), electromagnetic and gluonic
annihilation amplitudes add incoherently, namely they are 90 out of
phase. We argue that this incoherence must persist in each exclusive decay
channel. For inclusive (3686) decays, we suggest the absence of a
significant direct annihilation amplitude into three gluons and propose a new
amplitude via QCD anomalies and the (3526) off shell. Phenomenological
implications for exclusive decay channels are pointed out.Comment: 10 page
Modification of Z Boson Properties in Quark-Gluon Plasma
We calculate the change in the effective mass and width of a Z boson in the
environment of a quark-gluon plasma under the conditions expected in Pb-Pb
collisions at the LHC. The change in width is predicted to be only about 1 MeV
at a temperature of 1 GeV, compared to the natural width of 24907 MeV. The
mass shift is even smaller. Hence no observable effects are to be expected.Comment: 7 pages latex file with 6 embedded PS figure
Muon Detection of TeV Gamma Rays from Gamma Ray Bursts
Because of the limited size of the satellite-borne instruments, it has not
been possible to observe the flux of gamma ray bursts (GRB) beyond GeV energy.
We here show that it is possible to detect the GRB radiation of TeV energy and
above, by detecting the muon secondaries produced when the gamma rays shower in
the Earth's atmosphere. Observation is made possible by the recent
commissioning of underground detectors (AMANDA, the Lake Baikal detector and
MILAGRO) which combine a low muon threshold of a few hundred GeV or less, with
a large effective area of 10^3 m^2 or more. Observations will not only provide
new insights in the origin and characteristics of GRB, they also provide
quantitative information on the diffuse infrared background.Comment: Revtex, 12 pages, 3 postscript figures, uses epsfig.st
Baryon Masses in Chiral Perturbation Theory with Infrared Regularization
The baryon masses are examined in SU(3) chiral perturbation theory to third
order using the recently proposed infrared regularization scheme. Fourth order
is estimated by evaluating the dominant diagram. With this regularization the
magnitude of the loop integrals is reduced so that the convergence of the
series appears to be better than in the heavy baryon approach.Comment: The original third order calculation is supplemented by an estimate
of fourth order using just the dominant diagram. The convergence still
appears to be better than in the heavy baryon approach. To be published in
Phys. Rev. C. 15 pages latex, 2 postscript figure
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