1,284 research outputs found
Proton/pion ratios and radial flow in pp and peripheral heavy ion collisions
The production of baryon and mesons in the RHIC heavy-ion experiments has
received a lot of attention lately. Although not widely known, the pp data
measured concurrently with heavy ion collisions do not find a convincing
explanation in terms of simple models. We present the results of an afterburner
to Pythia and Hijing event generators, simulating radial flow which seems to
qualitatively explain the experimental results when applied to the pp collision
data from RHIC at 200 GeV center-of-mass energy.Comment: 4 page, 5 figures. Prepared for X Mexican Workshop on Particles and
Filed, Morelia Michoacan, November 7-17,2005. Referenced was corrected.
Section 2, a sentence was modifie
Azimuthal Correlations in p-p collisions
We report the analysis of experimental azimuthal correlations measured by
STAR in p-p collisions at = 200 GeV. We conclude that for a fit
of data using Pythia event generator we need to include two values of .Comment: 4 page, 3 figures. Prepared for X Mexican Workshop on Particles and
Fields. Morelia Mich. Nov 7-12, 200
R&D results on a CsI-TTGEM based photodetector
The very high momentum particle identification detector proposed for the
ALICE upgrade is a focusing RICH using a C4F10 gaseous radiator. For the
detection of Cherenkov photons, one of the options currently under
investigation is to use a CsI coated Triple-Thick-GEM (CsI-TTGEM) with metallic
or resistive electrodes. We will present results from the laboratory studies as
well as preliminary results of beam tests of a RICH detector prototype
consisting of a CaF2 radiator coupled to a 10x10 cm2 CsI-TTGEM equipped with a
pad readout and GASSIPLEX-based front-end electronics. With such a prototype
the detection of Cherenkov photons simultaneously with minimum ionizing
particles has been achieved for the first time in a stable operation mode
Probing compact dark matter objects with microlensing in gravitationally lensed quasars
The microlensing signal in the light curves of gravitationally lensed quasars can shed light on the dark matter (DM) composition in their lensing galaxies. Here, we investigate a sample of six lensed quasars from the most recent and best COSMOGRAIL observations: HE 1104-1805, HE 0435-1223, RX J1131-1231, WFI 2033-4723, PG 1115+080, and J1206+4332, yielding a total of eight microlensing light curves, when combining independent image pairs and typically spanning ten years. We explore the microlensing signals to determine whether the standard assumptions on the stellar populations are sufficient to account for the amplitudes of the measured signals or whether additional microlenses are needed. We use the most detailed lens models to date from the H0LiCOW/TDCOSMO collaboration to derive the microlensing parameters, such as the convergence, shear, and stellar/dark matter mass fraction at the position of the quasar images. We use these parameters to generate simulated microlensing light curves. Finally, we propose a methodology based on the Kolmogorov-Smirnov test to verify whether the observed microlensing amplitudes in our data are compatible with the most standard scenario, whereby galaxies are composed of stars as compact bodies and smoothly distributed DM. Given our current sample, we show that the standard scenario cannot be rejected, in contrast with previous results by Hawkins (2020a, A&A, 633, A107), claiming that a population of stellar mass primordial black holes (PBHs) is necessary to explain the observed amplitude of the microlensing signal in lensed quasar light curves. We further estimate the number of microlensing light curves needed to effectively distinguish between the standard scenario with stellar microlensing and a scenario that describes that all the DM contained in galaxies is in the form of compact objects such as PBHs, with a mean mass of 0.2 Mo. We find that about 900 microlensing curves from the Rubin Observatory will be sufficient to discriminate between the two extreme scenarios at a 95% confidence level.</p
The current progress of the ALICE Ring Imaging Cherenkov Detector
Recently, the last two modules (out of seven) of the ALICE High Momentum
Particle Identification detector (HMPID) were assembled and tested. The full
detector, after a pre-commissioning phase, has been installed in the
experimental area, inside the ALICE solenoid, at the end of September 2006. In
this paper we review the status of the ALICE/HMPID project and we present a
summary of the series production of the CsI photo-cathodes. We describe the key
features of the production procedure which ensures high quality photo-cathodes
as well as the results of the quality assessment performed by means of a
specially developed 2D scanner system able to produce a detailed map of the CsI
photo-current over the entire photo-cathode surface.
Finally we present our recent R&D efforts toward the development of a novel
generation of imaging Cherenkov detectors with the aim to identify, in heavy
ions collisions, hadrons up to 30 GeV/c.Comment: Presented at the Imaging-2006 Conference, Stockholm, Sweden, June
200
Radial flow afterburner for event generators and the baryon puzzle
A simple afterburner including radial flow to the randomized transverse
momentum obtained from event generators, Pythia and Hijing, has been
implemented to calculate the ratios and compare them with available
data. A coherent trend of qualitative agreement has been obtained in
collisions and in for various centralities. Those results indicate that
the radial flow does play an important role in the so called baryon puzzle
anomaly.Comment: 11 pages, 5 figures. To appear in Journal of Physics
Photosensitive Strip RETHGEM
An innovative photosensitive gaseous detector, consisting of a GEM like
amplification structure with double layered electrodes (instead of commonly
used metallic ones) coated with a CsI reflective photocathode, is described. In
one of our latest designs, the inner electrode consists of a metallic grid and
the outer one is made of resistive strips; the latter are manufactured by a
screen printing technology on the top of the metallic strips grid The inner
metallic grid is used for 2D position measurements whereas the resistive layer
provides an efficient spark protected operation at high gains - close to the
breakdown limit. Detectors with active areas of 10cm x10cm and 10cm x20cm were
tested under various conditions including the operation in photosensitive gas
mixtures containing ethylferrocene or TMAE vapors. The new technique could have
many applications requiring robust and reliable large area detectors for UV
visualization, as for example, in Cherenkov imaging devices.Comment: Presentes at the International Conference NDIP 2008, July 2008,
Franc
Aging of large area CsI photocathodes for the ALICE HMPID prototypes
The ALICE HMPID RICH detector is equipped with CsI photocathodes in a MWPC for the detection of Cherenkov photons. The long term operational experience with large area CsI photocathodes will be described. The RICH prototypes have shown a very high stability of operation and performance, at a gain of 10 \5 and with rates up to 2x10 \4 cm-2 s-1. When exposure to air has been avoided, no degradation of the CsI quantum efficiency has been observed on photocathodes periodically exposed to test-beams over 7 years, corresponding to local integrated charge densities of ~ 1 mC cm-2. The results of limited exposures to oxygen and humidity will also be presented
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