126 research outputs found
Measurements of group velocity of light in the lake Baikal water
The results of direct measurements of group velocity of light in the lake
Baikal water at the depth of 1100 m are presented. The lake Baikal water
dispersion has been measured at three wavelengths: 370 nm, 470 nm and 525 nm.
The results are in a rather good agreement with theoretical predictions.Comment: 4 pages, 5 figures, talk presented at RICH2002, to be published in
NIMA; misprints corrected in formula at page
Disruption of actin microfilaments by cytochalasin D leads to activation of p53
AbstractActivation of p53 plays a central role in the cell's response to various stress signals. We investigated whether p53 is activated upon disruption of actin microfilaments, caused by cytochalasin D (CD). We show that treatment with CD leads to accumulation of p53 in the cells and activation of p53-dependent transcription. Treatment with CD led to arrest of G1-to-S transition in cells retaining wild-type p53, while cells with inactivated p53 showed partial rescue from it. CD also induces apoptosis in p53+/+, but not in p53−/− cells. The obtained data suggest that disruption of the actin microfilaments activates p53-dependent pathways
An observation of a new class of afterpulses with delay time in the range of 70-200 microseconds in classical vacuum photomultipliers
We present results of the first observation of afterpulses with extremely
long (~120 microseconds) delay time from the main pulse in 8 inch classical
vacuum photomultipliers.Comment: To be published in NIM
Photoelectron backscattering in vacuum phototubes
In this article we describe results of a photoelectron backscattering effect
in vacuum phototubes: classical photomultipliers (PMT) and hybrid phototubes
(PH). Late pulses occurring in PMTs are attributed to the photoelectron
backscattering and distinguished from pulses due to an anode glow effect. The
late pulses are measured in a number of PMTs and HPs with various photocathode
sizes covering 1-50 cm range and different types of the first dynode materials
and construction designs. It is shown that the late pulses are a generic
feature of all vacuum photodetectors - PMTs and PHs and they don't deteriorate
dramatically amplitude and timing responses of vacuum phototubes
Pion, kaon, proton and anti-proton transverse momentum distributions from p+p and d+Au collisions at GeV
Identified mid-rapidity particle spectra of , , and
from 200 GeV p+p and d+Au collisions are reported. A
time-of-flight detector based on multi-gap resistive plate chamber technology
is used for particle identification. The particle-species dependence of the
Cronin effect is observed to be significantly smaller than that at lower
energies. The ratio of the nuclear modification factor () between
protons and charged hadrons () in the transverse momentum
range GeV/c is measured to be
(stat)(syst) in minimum-bias collisions and shows little
centrality dependence. The yield ratio of in minimum-bias d+Au
collisions is found to be a factor of 2 lower than that in Au+Au collisions,
indicating that the Cronin effect alone is not enough to account for the
relative baryon enhancement observed in heavy ion collisions at RHIC.Comment: 6 pages, 4 figures, 1 table. We extended the pion spectra from
transverse momentum 1.8 GeV/c to 3. GeV/
Azimuthal anisotropy at RHIC: the first and fourth harmonics
We report the first observations of the first harmonic (directed flow, v_1),
and the fourth harmonic (v_4), in the azimuthal distribution of particles with
respect to the reaction plane in Au+Au collisions at the Relativistic Heavy Ion
Collider (RHIC). Both measurements were done taking advantage of the large
elliptic flow (v_2) generated at RHIC. From the correlation of v_2 with v_1 it
is determined that v_2 is positive, or {\it in-plane}. The integrated v_4 is
about a factor of 10 smaller than v_2. For the sixth (v_6) and eighth (v_8)
harmonics upper limits on the magnitudes are reported.Comment: 6 pages with 3 figures, as accepted for Phys. Rev. Letters The data
tables are at
http://www.star.bnl.gov/central/publications/pubDetail.php?id=3
Demonstration of the temporal matter-wave Talbot effect for trapped matter waves
We demonstrate the temporal Talbot effect for trapped matter waves using
ultracold atoms in an optical lattice. We investigate the phase evolution of an
array of essentially non-interacting matter waves and observe matter-wave
collapse and revival in the form of a Talbot interference pattern. By using
long expansion times, we image momentum space with sub-recoil resolution,
allowing us to observe fractional Talbot fringes up to 10th order.Comment: 17 pages, 7 figure
Kaon Production and Kaon to Pion Ratio in Au+Au Collisions at \snn=130 GeV
Mid-rapidity transverse mass spectra and multiplicity densities of charged
and neutral kaons are reported for Au+Au collisions at \snn=130 GeV at RHIC.
The spectra are exponential in transverse mass, with an inverse slope of about
280 MeV in central collisions. The multiplicity densities for these particles
scale with the negative hadron pseudo-rapidity density. The charged kaon to
pion ratios are and
for the most central collisions. The ratio is lower than the same
ratio observed at the SPS while the is higher than the SPS result.
Both ratios are enhanced by about 50% relative to p+p and +p
collision data at similar energies.Comment: 6 pages, 3 figures, 1 tabl
The energy dependence of angular correlations inferred from mean- fluctuation scale dependence in heavy ion collisions at the SPS and RHIC
We present the first study of the energy dependence of angular
correlations inferred from event-wise mean transverse momentum
fluctuations in heavy ion collisions. We compare our large-acceptance
measurements at CM energies $\sqrt{s_{NN}} =$ 19.6, 62.4, 130 and 200 GeV to
SPS measurements at 12.3 and 17.3 GeV. $p_t$ angular correlation structure
suggests that the principal source of $p_t$ correlations and fluctuations is
minijets (minimum-bias parton fragments). We observe a dramatic increase in
correlations and fluctuations from SPS to RHIC energies, increasing linearly
with $\ln \sqrt{s_{NN}}$ from the onset of observable jet-related
fluctuations near 10 GeV.Comment: 10 pages, 4 figure
Partonic flow and -meson production in Au+Au collisions at = 200 GeV
We present first measurements of the -meson elliptic flow
() and high statistics distributions for different
centralities from = 200 GeV Au+Au collisions at RHIC. In
minimum bias collisions the of the meson is consistent with the
trend observed for mesons. The ratio of the yields of the to those of
the as a function of transverse momentum is consistent with a model
based on the recombination of thermal quarks up to GeV/,
but disagrees at higher momenta. The nuclear modification factor () of
follows the trend observed in the mesons rather than in
baryons, supporting baryon-meson scaling. Since -mesons are
made via coalescence of seemingly thermalized quarks in central Au+Au
collisions, the observations imply hot and dense matter with partonic
collectivity has been formed at RHIC.Comment: 6 pages, 4 figures, submit to PR
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