875 research outputs found
Results from the test bench of the Geometry Monitoring System of the ALICE Muon Spectrometer
We present the results obtained with the test bench of the Geometry Monitoring System (GMS) for the ALICE Muon Spectrometer. It consists in a mock up, reproducing at full scale, three half planes of the chambers 6, 7 and 8 of the spectrometer. We show that the GMS is able to measure transverse displacements with an accuracy of 1.5 microm. We show also that the resolution deteriorates by a factor 3 to 4 when thermal gradients are generated
Meson Production in In-In Collisions and the Puzzle
The NA60 experiment measured dimuon production in In-In collisions at 158
AGeV. This paper presents a high statistics measurement of with
the specific objective to provide insight on the puzzle, i.e. the
difference in the inverse slopes and absolute yields measured by NA49 and
NA50 in the kaon and lepton channel, respectively. Transverse momentum
distributions were studied as a function of centrality. The slope parameter
shows a rapid increase with centrality, followed by a saturation. Variations of
with the fit range of the order of 15 MeV were observed, possibly as a
consequence of radial flow. The meson yield normalized to the number of
participants increases with centrality and is consistently higher than the
yield measured by the NA49 experiment at any centrality.Comment: 4 Pages, 2 Figures. Proceedings of the 20 International
Conference on Ultra-Relativistic Nucleus Nucleus Collision
First Measurement of the rho Spectral Function in High-Energy Nuclear Collisions
We report on a precision measurement of low-mass muon pairs in 158 AGeV
indium-indium collisions at the CERN SPS. A significant excess of pairs is
observed above the yield expected from neutral meson decays. The unprecedented
sample size of 360 000 dimuons and the good mass resolution of about 2% allow
us to isolate the excess by subtraction of the decay sources. The shape of the
resulting mass spectrum is consistent with a dominant contribution from
pi+pi-->rho-->mu+mu- annihilation. The associated space-time averaged rho
spectral function shows a strong broadening, but essentially no shift in mass.
This may rule out theoretical models linking hadron masse
Thermal dileptons at SPS energies
Clear signs of excess dileptons above the known sources were found at the SPS
since long. However, a real clarification of these observations was only
recently achieved by NA60, measuring dimuons with unprecedented precision in
158A GeV, In-In collisions. The excess mass spectrum in the region M<1 GeV is
consistent with a dominant contribution from pi+pi- -> rho -> mu+mu-
annihilation. The associated rho spectral function shows a strong broadening,
but essentially no shift in mass. In the region M>1 GeV, the excess is found to
be prompt, not due to enhanced charm production. The inverse slope parameter
Teff associated with the transverse momentum spectra rises with mass up to the
rho, followed by a sudden decline above. While the initial rise, coupled to a
hierarchy in hadron freeze-out, points to radial flow of a hadronic decay
source, the decline above signals a transition to a low-flow source, presumably
of partonic origin. The mass spectra show at low transverse momenta the steep
rise towards low masses characteristic for Planck-like radiation. The
polarization of the excess referred to the Collins Soper frame is found to be
isotropic. All observations are consistent with the interpretation of the
excess as thermal radiation.Comment: Prepared for 20th International Conference on Ultra-Relativistic
Nucleus-Nucleus Collisions: Quark Matter 2008 (QM2008), Jaipur, India, 4-10
Feb. 200
Link between Intestinal CD36 Ligand Binding and Satiety Induced by a High Protein Diet in Mice
CD36 is a ubiquitous membrane glycoprotein that binds long-chain fatty acids. The presence of a functional CD36 is required for the induction of satiety by a lipid load and its role as a lipid receptor driving cellular signal has recently been demonstrated. Our project aimed to further explore the role of intestinal CD36 in the regulation of food intake. Duodenal infusions of vehicle or sulfo-N-succinimidyl-oleate (SSO) was performed prior to acute infusions of saline or Intralipid (IL) in mice. Infusion of minute quantities of IL induced a decrease in food intake (FI) compared to saline. Infusion of SSO had the same effect but no additive inhibitory effect was observed in presence of IL. No IL- or SSO-mediated satiety occurred in CD36-null mice. To determine whether the CD36-mediated hypophagic effect of lipids was maintained in animals fed a satietogen diet, mice were subjected to a High-Protein diet (HPD). Concomitantly with the satiety effect, a rise in intestinal CD36 gene expression was observed. No satiety effect occurred in CD36-null mice. HPD-fed WT mice showed a diminished FI compared to control mice, after saline duodenal infusion. But there was no further decrease after lipid infusion. The lipid-induced decrease in FI observed on control mice was accompanied by a rise in jejunal oleylethanolamide (OEA). Its level was higher in HPD-fed mice than in controls after saline infusion and was not changed by lipids. Overall, we demonstrate that lipid binding to intestinal CD36 is sufficient to produce a satiety effect. Moreover, it could participate in the satiety effect induced by HPD. Intestine can modulate FI by several mechanisms including an increase in OEA production and CD36 gene expression. Furthermore, intestine of mice adapted to HPD have a diminished capacity to modulate their food intake in response to dietary lipids
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