847 research outputs found
U_A(1) Symmetry Restoration from an In-Medium eta' Mass Reduction in sqrt(s(NN)) = 200 GeV Au+Au Collisions
A reduction of the mass of the eta'(958) meson may signal restoration of the
U_A(1) symmetry in a hot and dense hadronic matter, corresponding to the return
of the 9th, "prodigal" Goldstone boson. We report on an analysis of a combined
PHENIX and STAR data set on the intercept parameter of the two-pion
Bose-Einstein correlation functions, as measuremed in sqrt(s(NN)) = 200 GeV Au
+ Au collisions at RHIC. To describe this combined PHENIX and STAR dataset, an
in-medium eta' mass reduction of at least 200 MeV is needed, at the 99.9 %
confidence level in a broad model class of resonance abundances.Comment: 12 pages, 5 figures, to appear in the Proceedings of the Gribov'80
Memorial Worksho
Significant in-medium reduction of the mass of eta' mesons in sqrt(s(NN)) = 200 GeV Au+Au collisions
PHENIX and STAR data on the intercept parameter of the two-pion Bose-Einstein
correlation functions in GeV Au+Au collisions were
analysed in terms of various models of hadronic abundances. To describe these
data, an in-medium mass decrease of at least 200 MeV was needed
in each case.Comment: Dedicated to 60th birthday of Miklos Gyulassy. 2 pages, 4 figures -
To appear in the conference proceedings for Quark Matter 2009, March 30 -
April 4, Knoxville, Tennesse
A ratchet mechanism for amplification in low-frequency mammalian hearing
The sensitivity and frequency selectivity of hearing result from tuned
amplification by an active process in the mechanoreceptive hair cells. In most
vertebrates the active process stems from the active motility of hair bundles.
The mammalian cochlea exhibits an additional form of mechanical activity termed
electromotility: its outer hair cells (OHCs) change length upon electrical
stimulation. The relative contributions of these two mechanisms to the active
process in the mammalian inner ear is the subject of intense current debate.
Here we show that active hair-bundle motility and electromotility can together
implement an efficient mechanism for amplification that functions like a
ratchet: sound-evoked forces acting on the basilar membrane are transmitted to
the hair bundles whereas electromotility decouples active hair-bundle forces
from the basilar membrane. This unidirectional coupling can extend the hearing
range well below the resonant frequency of the basilar membrane. It thereby
provides a concept for low-frequency hearing that accounts for a variety of
unexplained experimental observations from the cochlear apex, including the
shape and phase behavior of apical tuning curves, their lack of significant
nonlinearities, and the shape changes of threshold tuning curves of auditory
nerve fibers along the cochlea. The ratchet mechanism constitutes a general
design principle for implementing mechanical amplification in engineering
applications.Comment: 6 pages, 4 figures, plus Supplementary Information. Animation
available on the PNAS website (http://dx.doi.org/10.1073/pnas.0914345107)
Correlations of electrons from heavy flavor decay in p+p, d+Au and Au+Au collisions
In relativistic heavy ion collisions heavy flavor probes are crucial to understand the interactions between partons and the produced hot nuclear matter. Measurements in p+p collisions provide information about how the heavy quarks are produced and fragment and in d+Au collisions are sensitive to possible effects from cold nuclear matter. Azimuthal correlation measurements involving heavy flavor probes are complementary to single particle spectra measurements and provide additional information about production and interactions of heavy quarks. Measurements of electrons with heavy flavor decay with other hadrons from the event can provide information about how the heavy quark interacts with the produced matter and can be compared to similar measurements from light hadron correlations. Correlations between electrons from heavy flavor decay with muons, also from heavy flavor decay, can provide further information about heavy flavor production and cold nuclear matter effects in d+Au collisions with a very clean signal. We present PHENIX results for electron-hadron correlations in p+p and Au+Au collisions and electron-muon correlations in p+p and d+Au collisions and discuss the implications of these measurements
LHC Optics Measurement with Proton Tracks Detected by the Roman Pots of the TOTEM Experiment
Precise knowledge of the beam optics at the LHC is crucial to fulfil the
physics goals of the TOTEM experiment, where the kinematics of the scattered
protons is reconstructed with the near-beam telescopes -- so-called Roman Pots
(RP). Before being detected, the protons' trajectories are influenced by the
magnetic fields of the accelerator lattice. Thus precise understanding of the
proton transport is of key importance for the experiment. A novel method of
optics evaluation is proposed which exploits kinematical distributions of
elastically scattered protons observed in the RPs. Theoretical predictions, as
well as Monte Carlo studies, show that the residual uncertainty of this optics
estimation method is smaller than 0.25 percent.Comment: 20 pages, 11 figures, 5 figures, to be submitted to New J. Phy
Double diffractive cross-section measurement in the forward region at LHC
The first double diffractive cross-section measurement in the very forward
region has been carried out by the TOTEM experiment at the LHC with
center-of-mass energy of sqrt(s)=7 TeV. By utilizing the very forward TOTEM
tracking detectors T1 and T2, which extend up to |eta|=6.5, a clean sample of
double diffractive pp events was extracted. From these events, we measured the
cross-section sigma_DD =(116 +- 25) mub for events where both diffractive
systems have 4.7 <|eta|_min < 6.5 .Comment: 5 pages, 1 figure, submitted for publicatio
First Results from the TOTEM Experiment
The first physics results from the TOTEM experiment are here reported,
concerning the measurements of the total, differential elastic, elastic and
inelastic pp cross-section at the LHC energy of = 7 TeV, obtained
using the luminosity measurement from CMS. A preliminary measurement of the
forward charged particle distribution is also shown.Comment: Conference Proceeding. MPI@LHC 2010: 2nd International Workshop on
Multiple Partonic Interactions at the LHC. Glasgow (UK), 29th of November to
the 3rd of December 201
Performance of the TOTEM Detectors at the LHC
The TOTEM Experiment is designed to measure the total proton-proton
cross-section with the luminosity-independent method and to study elastic and
diffractive pp scattering at the LHC. To achieve optimum forward coverage for
charged particles emitted by the pp collisions in the interaction point IP5,
two tracking telescopes, T1 and T2, are installed on each side of the IP in the
pseudorapidity region 3.1 < = |eta | < = 6.5, and special movable beam-pipe
insertions - called Roman Pots (RP) - are placed at distances of +- 147 m and
+- 220 m from IP5. This article describes in detail the working of the TOTEM
detector to produce physics results in the first three years of operation and
data taking at the LHC.Comment: 40 pages, 31 figures, submitted to Int. J. Mod. Phys.
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