18 research outputs found
Development of Resistive Electrode Gas Electron Multiplier (RE-GEM)
We successfully produced Resistive-Electrode Gas Electron Multiplier (RE-GEM) which has resistive electrodes instead of the metal ones which are employed for the standard GEM foils. RE-GEM has a resistive electrode of 25 micron-thick and an insulator layer of 100 micron-thick. The hole structure of RE-GEM is a single conical with the wider and narrower hole diameters of 80 micron and 60 micron, respectively. A hole pitch of RE-GEM is 140 micron. We obtained the maximum gain of about 600 and the typical energy resolution of about 20% (FWHM) at an applied voltage between the resistive electrodes of 620 V, using a collimated 8 keV X-rays from a generator in a gas mixture of 70% Ar and 30% CO2 by volume at the atmospheric pressure. We measured the effective gain as a function of the electric field of the drift region and obtained the maximum gain at an drift field of 0.5 kV/cm
Measurement of higher cumulants of net-charge multiplicity distributions in AuAu collisions at GeV
We report the measurement of cumulants () of the net-charge
distributions measured within pseudorapidity () in AuAu
collisions at GeV with the PHENIX experiment at the
Relativistic Heavy Ion Collider. The ratios of cumulants (e.g. ,
) of the net-charge distributions, which can be related to volume
independent susceptibility ratios, are studied as a function of centrality and
energy. These quantities are important to understand the quantum-chromodynamics
phase diagram and possible existence of a critical end point. The measured
values are very well described by expectation from negative binomial
distributions. We do not observe any nonmonotonic behavior in the ratios of the
cumulants as a function of collision energy. The measured values of and can be directly compared to lattice
quantum-chromodynamics calculations and thus allow extraction of both the
chemical freeze-out temperature and the baryon chemical potential at each
center-of-mass energy.Comment: 512 authors, 8 pages, 4 figures, 1 table. v2 is version accepted for
publication in Phys. Rev. C as a Rapid Communication. Plain text data tables
for the points plotted in figures for this and previous PHENIX publications
are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm
Single electron yields from semileptonic charm and bottom hadron decays in AuAu collisions at GeV
The PHENIX Collaboration at the Relativistic Heavy Ion Collider has measured
open heavy-flavor production in minimum bias AuAu collisions at
GeV via the yields of electrons from semileptonic decays
of charm and bottom hadrons. Previous heavy-flavor electron measurements
indicated substantial modification in the momentum distribution of the parent
heavy quarks due to the quark-gluon plasma created in these collisions. For the
first time, using the PHENIX silicon vertex detector to measure precision
displaced tracking, the relative contributions from charm and bottom hadrons to
these electrons as a function of transverse momentum are measured in AuAu
collisions. We compare the fraction of electrons from bottom hadrons to
previously published results extracted from electron-hadron correlations in
collisions at GeV and find the fractions to be
similar within the large uncertainties on both measurements for
GeV/. We use the bottom electron fractions in AuAu and along
with the previously measured heavy flavor electron to calculate the
for electrons from charm and bottom hadron decays separately. We find
that electrons from bottom hadron decays are less suppressed than those from
charm for the region GeV/.Comment: 432 authors, 33 pages, 23 figures, 2 tables, 2011 data. v2 is version
accepted for publication by Phys. Rev. C. Plain text data tables for the
points plotted in figures for this and previous PHENIX publications are (or
will be) publicly available at http://www.phenix.bnl.gov/papers.htm
Transverse energy production and charged-particle multiplicity at midrapidity in various systems from to 200 GeV
Measurements of midrapidity charged particle multiplicity distributions,
, and midrapidity transverse-energy distributions,
, are presented for a variety of collision systems and energies.
Included are distributions for AuAu collisions at ,
130, 62.4, 39, 27, 19.6, 14.5, and 7.7 GeV, CuCu collisions at
and 62.4 GeV, CuAu collisions at
GeV, UU collisions at GeV,
Au collisions at GeV, HeAu collisions at
GeV, and collisions at
GeV. Centrality-dependent distributions at midrapidity are presented in terms
of the number of nucleon participants, , and the number of
constituent quark participants, . For all collisions
down to GeV, it is observed that the midrapidity data
are better described by scaling with than scaling with . Also presented are estimates of the Bjorken energy density,
, and the ratio of to ,
the latter of which is seen to be constant as a function of centrality for all
systems.Comment: 706 authors, 32 pages, 20 figures, 34 tables, 2004, 2005, 2008, 2010,
2011, and 2012 data. v2 is version accepted for publication in Phys. Rev.