771 research outputs found
The ``Out-Longitudinal'' Cross Term and Other Model Independent Features of the Two-Particle HBT Correlation Function
Using two specific models and a model independent formalism, we show that an
``out-longitudinal'' cross term should be included in any gaussian fits to
correlation data. In addition, we show that correlation radii (including the
cross term) measure lengths of homogeneity within the source, not necessarily
geometric sizes.Comment: 4 pages, uuencoded compressed postscrip
Observing Non-Gaussian Sources in Heavy-Ion Reactions
We examine the possibility of extracting non-Gaussian sources from
two-particle correlations in heavy-ion reactions. Non-Gaussian sources have
been predicted in a variety of model calculations and may have been seen in
various like-meson pair correlations. As a tool for this investigation, we have
developed an improved imaging method that relies on a Basis spline expansion of
the source functions with an improved implementation of constraints. We examine
under what conditions this improved method can distinguish between Gaussian and
non-Gaussian sources. Finally, we investigate pion, kaon, and proton sources
from the p-Pb reaction at 450 GeV/nucleon and from the S-Pb reaction at 200
GeV/nucleon studied by the NA44 experiment. Both the pion and kaon sources from
the S-Pb correlations seem to exhibit a Gaussian core with an extended,
non-Gaussian halo. We also find evidence for a scaling of the source widths
with particle mass in the sources from the p-Pb reaction.Comment: 16 pages, 15 figures, 5 tables, uses RevTex3.
Pion interferometry with pion-source-medium interactions
An extended pion source, which can be temporarily created by a high energy
nuclear collision, will also absorb and distort the outgoing pions. We discuss
how this effect alters the interferometric pattern of the two-pion momentum
correlation function. In particular, we show that the two-pion correlation
function decreases rapidly when the opening angle between the pions increases.
The opening-angle dependence should serve as a new means of obtaining
information about the pion source in the analysis of experimental data.Comment: 14 pages (revtex) and 9 figures (uuencoded), Caltech preprint
MAP-175, Indiana Univ. preprint IU/NTC 914-1
Bose-Einstein Correlations for Three-Dimensionally Expanding, Cylindrically Symmetric, Finite Systems
The parameters of the Bose-Einstein correlation function may obey an {\it
-scaling}, as observed in and reactions at CERN SPS.
This -scaling implies that the Bose-Einstein correlation functions view
only a small part of the big and expanding system. The full sizes of the
expanding system at the last interaction are shown to be measurable with the
help the invariant momentum distribution of the emitted particles. A vanishing
duration parameter can also be generated in the considered model-class with a
specific dependence.Comment: 35 pages, ReVTeX, LaTeX, no figures, discussion extende
Improving the sensitivity of future GW observatories in the 1-10 Hz band: Newtonian and seismic noise
The next generation gravitational wave interferometric detectors will likely be underground detectors to extend the GW detection frequency band to frequencies below the Newtonian noise limit. Newtonian noise originates from the continuous motion of the Earth’s crust driven by human activity, tidal stresses and seismic motion, and from mass density fluctuations in the atmosphere. It is calculated that on Earth’s surface, on a typical day, it will exceed the expected GW signals at frequencies below 10 Hz. The noise will decrease underground by an unknown amount. It is
important to investigate and to quantify this expected reduction and its effect on the sensitivity of future detectors, to plan for further improvement strategies. We report about some of these aspects. Analytical models can be used in the simplest scenarios to get a better qualitative and semi-quantitative understanding. As more complete modeling can be done numerically, we will discuss also some results obtained with a finite-element-based modeling tool. The method is verified by comparing its results with the results of analytic calculations for surface detectors. A key point about noise models is their initial parameters and conditions, which require detailed information about seismic motion in a real scenario. We will describe an effort to characterize the seismic activity at the Homestake mine which is currently in progress. This activity is specifically aimed to provide informations and to explore the site as a possible candidate for an underground observatory. Although the only compelling reason to put the interferometer underground is to reduce the Newtonian noise, we expect that the more stable underground environment will have a more general positive impact on the sensitivity.We will end this report with some considerations about seismic and suspension noise
Two-Proton Correlations near Midrapidity in p+Pb and S+Pb Collisions at the CERN SPS
Correlations of two protons emitted near midrapidity in p+Pb collisions at
450 GeV/c and S+Pb collisions at 200A GeV/c are presented, as measured by the
NA44 Experiment. The correlation effect, which arises as a result of final
state interactions and Fermi-Dirac statistics, is related to the space-time
characteristics of proton emission. The measured source sizes are smaller than
the size of the target lead nucleus but larger than the sizes of the
projectiles. A dependence on the collision centrality is observed; the source
size increases with decreasing impact parameter. Proton source sizes near
midrapidity appear to be smaller than those of pions in the same interactions.
Quantitative agreement with the results of RQMD (v1.08) simulations is found
for p+Pb collisions. For S+Pb collisions the measured correlation effect is
somewhat weaker than that predicted by the model simulations, implying either a
larger source size or larger contribution of protons from long-lived particle
decays.Comment: 10 pages (LaTeX) text, 4 (EPS) figures; accepted for publication in
Phys. Lett.
MHC-B variation in maternal and paternal synthetic lines of the Argentinian Campero INTA chicken
The Campero-INTA chicken of Argentina was developed to provide a robust bird that can survive under Argentinian pasture conditions with no significant additional nutrition, producing a source of animal protein for small producers or low-income families. In previous work we described the AH paternal line of Campero and its Major Histocompatibility Complex B region (MHC-B) variation. In this work we analyzed the three remaining synthetic lines used to produce the Campero-INTA production bird: lines AS, A and E. Because of the association between variation within the MHC of chickens and disease resistance, MHC variation within this breed is of particular interest. MHC variability within the lines used to produce the Campero-INTA chicken was examined using a 90 SNP panel encompassing the chicken MHC-B region plus the VNTR, LEI0258, located within the chicken MHC. Across all four lines 12 haplotypes were found, with 7 of these being previously reported in North America/European breeds, reflecting the original breed sources for these birds. Three Campero unique haplotypes were found, two of which likely originated from MHC recombination events. MHC-B variation for all lines involved with production of the final Campero-INTA bird have now been determined.EEA PergaminoFil: Iglesias, Gabriela M. Universidad Nacional de Río Negro. Sede Alto Valle y Valle Medio. Escuela de Veterinaria y Producción Agroindustrial. Cátedra de Genética; ArgentinaFil: Beker, María P. Universidad Nacional de Río Negro. Sede Alto Valle y Valle Medio. Escuela de Veterinaria y Producción Agroindustrial. Cátedra de Genética; ArgentinaFil: Remolins, José S. Universidad Nacional de Río Negro. Sede Alto Valle y Valle Medio. Escuela de Veterinaria y Producción Agroindustrial. Cátedra de Genética; ArgentinaFil: Canet, Zulma Edith. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Pergamino. Sección Avicultura; ArgentinaFil: Canet, Zulma Edith. Universidad Nacional de Rosario. Facultad de Ciencias Veterinaria. Cátedra de Genética; ArgentinaFil: Librera, José. Universidad Nacional de Rosario. Facultad de Ciencias Veterinarias. Cátedra de Genética; ArgentinaFil: Cantaro, Horacio Luis. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Alto Valle; ArgentinaFil: Cantaro, Horacio Luis. Universidad Nacional de Río Negro. Sede Alto Valle y Valle Medio. Escuela de Veterinaria y Producción Agroindustrial. Cátedra de Genética; ArgentinaFil: Maizon, Daniel Omar Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Anguil; ArgentinaFil: Fulton, Janet E. Hy-Line International; Estados Unido
Ages of stellar populations in the low-metallicity star-forming dwarf galaxies
We perform a comprehensive study of ten star-forming (SF) galaxies with the oxygen abundance Z 1 (or ~10 Gyr) just as for low-mass galaxies efficient star formation have been triggered at z ~ 0.2 (or ~2 Gyr)
Intrauterine exposure to chronic hypoxia in the rat leads to progressive diastolic function and increased aortic stiffness from early postnatal developmental stages
Aim We sought to explore whether fetal hypoxia exposure, an insult of placental insufficiency, is associated with left ventricular dysfunction and increased aortic stiffness at early postnatal ages. Methods Pregnant Sprague Dawley rats were exposed to hypoxic conditions (11.5% FiO2) from embryonic day E15‐21 or normoxic conditions (controls). After delivery, left ventricular function and aortic pulse wave velocity (measure of aortic stiffness) were assessed longitudinally by echocardiography from day 1 through week 8. A mixed ANOVA with repeated measures was performed to compare findings between groups across time. Myocardial hematoxylin and eosin and picro‐sirius staining were performed to evaluate myocyte nuclear shape and collagen fiber characteristics, respectively. Results Systolic function parameters transiently increased following hypoxia exposure primarily at week 2 (p \u3c .008). In contrast, diastolic dysfunction progressed following fetal hypoxia exposure beginning weeks 1–2 with lower early inflow Doppler velocities, and less of an increase in early to late inflow velocity ratios and annular and septal E’/A’ tissue velocities compared to controls (p \u3c .008). As further evidence of altered diastolic function, isovolumetric relaxation time was significantly shorter relative to the cardiac cycle following hypoxia exposure from week 1 onward (p \u3c .008). Aortic stiffness was greater following hypoxia from day 1 through week 8 (p \u3c .008, except week 4). Hypoxia exposure was also associated with altered nuclear shape at week 2 and increased collagen fiber thickness at week 4. Conclusion Chronic fetal hypoxia is associated with progressive LV diastolic dysfunction, which corresponds with changes in nuclear shape and collagen fiber thickness, and increased aortic stiffness from early postnatal stages
Source Dimensions in Ultrarelativistic Heavy Ion Collisions
Recent experiments on pion correlations, interpreted as interferometric
measurements of the collision zone, are compared with models that distinguish a
prehadronic phase and a hadronic phase. The models include prehadronic
longitudinal expansion, conversion to hadrons in local kinetic equilibrium, and
rescattering of the produced hadrons. We find that the longitudinal and outward
radii are surprisingly sensitive to the algorithm used for two-body collisions.
The longitudinal radius measured in collisions of 200 GeV/u sulfur nuclei on a
heavy target requires the existence of a prehadronic phase which converts to
the hadronic phase at densities around 0.8-1.0 GeV/fm. The transverse radii
cannot be reproduced without introducing more complex dynamics into the
transverse expansion.Comment: RevTeX 3.0, 28 pages, 6 figures, not included, revised version, major
change is an additional discussion of the classical two-body collision
algorithm, a (compressed) postscript file of the complete paper including
figures can be obtained from Authors or via anonymous ftp at
ftp://ftp_int.phys.washington.edu/pub/herrmann/pisource.ps.
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