133 research outputs found
The future of PHENIX: upgrading to sPHENIX and beyond
sPHENIX is a major upgrade to the PHENIX detector enabling high-rate, large acceptance measurements of upsilons, direct photons and fully reconstructed jets in p-p, p-A and A-A collisions at the Relativistic Heavy Ion Collider (RHIC). These detailed measurements will probe the Quark Gluon Plasma near its transition temperature, in a region of strongest coupling. The sPHENIX detector consists of hadronic and electromagnetic calorimetry, and charged particle tracking in conjunction with the recently acquired 1.5 tesla BaBar super-conducting solenoid. The sPHENIX acceptance of 2π in azimuth and |η| < 1.1 in pseudo-rapidity provides a factor of six improvement over the present PHENIX central spectrometer. Beyond being an excellent RHIC detector, sPHENIX provides an outstanding foundation for a detector focused on the physics of a possible future electron-ion collider at RHIC (eRHIC). In this talk we will discuss the physics potential of the sPHENIX detector, the design and technology choices for the sPHENIX calorimeters, and the conceptual design of a day-one detector for eRHIC
A Measurement of Time-Averaged Aerosol Optical Depth using Air-Showers Observed in Stereo by HiRes
Air fluorescence measurements of cosmic ray energy must be corrected for
attenuation of the atmosphere. In this paper we show that the air-showers
themselves can yield a measurement of the aerosol attenuation in terms of
optical depth, time-averaged over extended periods. Although the technique
lacks statistical power to make the critical hourly measurements that only
specialized active instruments can achieve, we note the technique does not
depend on absolute calibration of the detector hardware, and requires no
additional equipment beyond the fluorescence detectors that observe the air
showers. This paper describes the technique, and presents results based on
analysis of 1258 air-showers observed in stereo by the High Resolution Fly's
Eye over a four year span.Comment: 7 pages, 3 figures, accepted for publication by Astroparticle Physics
Journa
Diffractive \eta_c and \eta_b productions by neutrinos via neutral currents
We report a first theoretical study for neutrino-induced diffractive
productions of heavy pseudoscalar mesons, \eta_c and \eta_b, off a nucleon.
Based on factorization formalism for exclusive processes, we evaluate the
forward diffractive production cross section in perturbative QCD in terms of
the light-cone Q\bar{Q} wave functions (WFs) of \eta_{c,b} mesons and the gluon
distribution of the nucleon. The light-cone WFs of the \eta_c (\eta_b) meson
are constructed to satisfy the spin symmetry relations with those of the J/\psi
(\Upsilon) meson. The diffractive \eta_c production is governed by the
axial-vector coupling of the longitudinally polarized Z boson to Q\bar{Q} pair,
and the resulting \eta_c production rate is larger than the J/\psi one by one
order of magnitude. We also discuss the production of bottomonium \eta_b, which
shows up for higher beam energy.Comment: REVTex4, 4 pages with 3 embedded figure
Mass spectra of doubly heavy Omega_QQ' baryons
We evaluate the masses of baryons composed of two heavy quarks and a strange
quark with account for spin-dependent splittings in the framework of potential
model with the KKO potential motivated by QCD with a three-loop beta-function
for the effective charge consistent with both the perturbative limit at short
distances and linear confinement term at long distances between the quarks. The
factorization of dynamics is supposed and explored in the nonrelativistic
Schroedinger equation for the motion in the system of two heavy quarks
constituting the doubly heavy diquark and the strange quark interaction with
the diquark. The limits of approach, its justification and uncertainties are
discussed. Excited quasistable states are classified by the quantum numbers of
heavy diquark composed by the heavy quarks of the same flavor.Comment: 14 pages, revtex4-file, 3 eps-figures, 5 tables, typos correcte
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Measurement of Bottom versus Charm as a Function of Transverse Momentum with Electron-Hadron Correlations in p+p Collisions at sqrt(s)=200 GeV
The momentum distribution of electrons from semi-leptonic decays of charm and
bottom for mid-rapidity |y|<0.35 in p+p collisions at sqrt(s)=200 GeV is
measured by the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC)
over the transverse momentum range 2 < p_T < 7 GeV/c. The ratio of the yield of
electrons from bottom to that from charm is presented. The ratio is determined
using partial D/D^bar --> e^{+/-} K^{-/+} X (K unidentified) reconstruction. It
is found that the yield of electrons from bottom becomes significant above 4
GeV/c in p_T. A fixed-order-plus-next-to-leading-log (FONLL) perturbative
quantum chromodynamics (pQCD) calculation agrees with the data within the
theoretical and experimental uncertainties. The extracted total bottom
production cross section at this energy is \sigma_{b\b^bar}= 3.2
^{+1.2}_{-1.1}(stat) ^{+1.4}_{-1.3}(syst) micro b.Comment: 432 authors, 6 pages text, 3 figures. Submitted to Phys. Rev. Lett.
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
A Likelihood Method for Measuring the Ultrahigh Energy Cosmic Ray Composition
Air fluorescence detectors traditionally determine the dominant chemical
composit ion of the ultrahigh energy cosmic ray flux by comparing the averaged
slant depth of the shower maximum, , as a function of energy to the
slant depths expect ed for various hypothesized primaries. In this paper, we
present a method to make a direct measurement of the expected mean number of
protons and iron by comparing the shap es of the expected
distributions to the distribution for data. The advantages of this method
includes the use of information of the full distribution and its ability to
calculate a flux for various cosmic ray compositi ons. The same method can be
expanded to marginalize uncertainties due to choice of spectra, hadronic models
and atmospheric parameters. We demonstrate the technique with independent
simulated data samples from a parent sample of protons and iron. We accurately
predict the number of protons and iron in the parent sample and show that the
uncertainties are meaningful.Comment: 11 figures, 22 pages, accepted by Astroparticle Physic
Alternative Methods to Finding Patterns in HiRes Stereo Data
In this paper Ultra High Energy Cosmic Rays UHECRs data observed by the HiRes
fluorescence detector in stereo mode is analyzed to search for events in the
sky with an arrival direction lying on a great circle. Such structure is known
as the arc structure. The arc structure is expected when the charged cosmic
rays pass through the galactic magnetic field. The arcs searched for could
represent a broad or a small scale anisotropy depending on the proposed source
model for the UHECRs. The Arcs in this paper are looked for using Hough
transform were Hough transform is a technique used to looking for patterns in
images. No statistically significant arcs were found in this study
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