956 research outputs found
Computational Modeling of Solvent Effect on Fluorescence Spectra. Implications to the Fluorescent State Structure
The financial support of the National Science Fund of Bulgaria (Contract DN 19/11, 10.12.2017) is gratefully acknowledged
Design and Photophysics of 2-Vinyl Quinazolin-4-ones
The reported work has been carried out under Contract DN 19/11, 10.12.2017, with the National Science Fund of Bulgaria
Status and Performance of New Silicon Stripixel Detector for the PHENIX Experiment at RHIC: Beta Source, Cosmic-rays and Proton Beam at 120 GeV
We are constructing a Silicon Vertex Tracker detector (VTX) for the PHENIX
experiment at RHIC. Our main motivation is to enable measurements of heavy
flavor production (charm and beauty) in p+p, p+d and A+A collisions. Such data
will illuminate the properties of the matter created in high-energy heavy-ion
collisions. The measurements also will reveal the distribution of gluons in
protons from p+p collisions. The VTX detector consists of four layers of barrel
detectors and covers |eta|< 1.2, and almost a 2pi in azimuth. The inner two
silicon barrels consist of silicon pixel sensors; their technology accords with
that of the ALICE1LHCB sensor-readout hybrid. The outer two barrels are silicon
stripixel detectors with a new "spiral" design, and a single-sided sensor with
2-dimensional (X, U) readout. In this paper, we describe the silicon stripixel
detector and discuss its performance, including its response to electrons from
a beta source (90Sr), muons from cosmic-rays, and a 120 GeV proton beam. The
results from the proton beam demonstrate that the principle of two-dimensional
position sensitivity based on charge sharing works; the signal-to-noise value
is 10.4, the position resolution is 33.6 um for X-stripixel (35.2 um for
U-stripixel), and the tracking efficiencies in the X- and U-stripixels are,
over 98.9 +/- 0.2%. The stripixel detector within the VTX project is in the
pre-production phase.Comment: Accepted for publication in Journal of Instrumentation (JINST).
Invited talk at Pixel 2008 International Workshop, September 23-26, 2008,
Fermilab, Batavia, Illinois, U.S.
L\'evy-stable two-pion Bose-Einstein correlations in GeV AuAu collisions
We present a detailed measurement of charged two-pion correlation functions
in 0%-30% centrality GeV AuAu collisions by the
PHENIX experiment at the Relativistic Heavy Ion Collider. The data are well
described by Bose-Einstein correlation functions stemming from L\'evy-stable
source distributions. Using a fine transverse momentum binning, we extract the
correlation strength parameter , the L\'evy index of stability
and the L\'evy length scale parameter as a function of average
transverse mass of the pair . We find that the positively and the
negatively charged pion pairs yield consistent results, and their correlation
functions are represented, within uncertainties, by the same L\'evy-stable
source functions. The measurements indicate a decrease of the
strength of the correlations at low . The L\'evy length scale parameter
decreases with increasing , following a hydrodynamically
predicted type of scaling behavior. The values of the L\'evy index of stability
are found to be significantly lower than the Gaussian case of
, but also significantly larger than the conjectured value that may
characterize the critical point of a second-order quark-hadron phase
transition.Comment: 448 authors, 25 pages, 11 figures, 4 tables, 2010 data. v2 is version
accepted for publication in 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
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
J/psi suppression at forward rapidity in Au+Au collisions at sqrt(s_NN)=39 and 62.4 GeV
We present measurements of the J/psi invariant yields in sqrt(s_NN)=39 and
62.4 GeV Au+Au collisions at forward rapidity (1.2<|y|<2.2). Invariant yields
are presented as a function of both collision centrality and transverse
momentum. Nuclear modifications are obtained for central relative to peripheral
Au+Au collisions (R_CP) and for various centrality selections in Au+Au relative
to scaled p+p cross sections obtained from other measurements (R_AA). The
observed suppression patterns at 39 and 62.4 GeV are quite similar to those
previously measured at 200 GeV. This similar suppression presents a challenge
to theoretical models that contain various competing mechanisms with different
energy dependencies, some of which cause suppression and others enhancement.Comment: 365 authors, 10 pages, 11 figures, 4 tables. Submitted to 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.
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