80 research outputs found
The Search for Stable, Massive, Elementary Particles
In this paper we review the experimental and observational searches for
stable, massive, elementary particles other than the electron and proton. The
particles may be neutral, may have unit charge or may have fractional charge.
They may interact through the strong, electromagnetic, weak or gravitational
forces or through some unknown force. The purpose of this review is to provide
a guide for future searches - what is known, what is not known, and what appear
to be the most fruitful areas for new searches. A variety of experimental and
observational methods such as accelerator experiments, cosmic ray studies,
searches for exotic particles in bulk matter and searches using astrophysical
observations is included in this review.Comment: 34 pages, 8 eps figure
Searching for Gravitational Waves from Binary Inspirals with LIGO
We describe the current status of the search for gravitational waves from
inspiralling compact binary systems in LIGO data. We review the result from the
first scientific run of LIGO (S1). We present the goals of the search of data
taken in the second scientific run (S2) and describe the differences between
the methods used in S1 and S2.Comment: 9 pages, 2 figures. Published in proceedings of the 8th Gravitational
Wave Data Analysis Workshop, Milwaukee, WI, USA, 17-20 December 200
Momentum Distribution in the Decay B-->J/psi+X
We combine the NRQCD formalism for the inclusive color singlet and octet
production of charmonium states with the parton and the ACCMM model,
respectively, and calculate the momentum distribution in the decay B-->J/psi+X.
Neglecting the kinematics of soft gluon radiation, we find that the motion of
the b quark in the bound state can account, to a large extent, for the observed
spectrum. The parton model gives a satisfactory presentation of the data,
provided that the heavy quark momentum distribution is taken to be soft. To be
explicit, we obtain epsilon_p=O(0.008-0.012) for the parameter of the Peterson
et al. distribution function. The ACCMM model can account for the data more
accurately. The preferred Fermi momentum p_F=O(0.57 GeV) is in good agreement
with recent studies of the heavy quark's kinetic energy.Comment: revised version to be published in Phys. Rev. D; 27 pages, LaTeX, 7
eps figures, uses a4wide.sty, epsfig.sty and amssymb.st
Nuclear matter effects on production in asymmetric Cu+Au collisions at = 200 GeV
We report on production from asymmetric Cu+Au heavy-ion collisions
at =200 GeV at the Relativistic Heavy Ion Collider at both
forward (Cu-going direction) and backward (Au-going direction) rapidities. The
nuclear modification of yields in CuAu collisions in the Au-going
direction is found to be comparable to that in AuAu collisions when plotted
as a function of the number of participating nucleons. In the Cu-going
direction, production shows a stronger suppression. This difference is
comparable in magnitude and has the same sign as the difference expected from
shadowing effects due to stronger low- gluon suppression in the larger Au
nucleus. The relative suppression is opposite to that expected from hot nuclear
matter dissociation, since a higher energy density is expected in the Au-going
direction.Comment: 349 authors, 10 pages, 4 figures, and 4 tables. Submitted to Phys.
Rev. C. For v2, fixed LaTeX error in 3rd-to-last sentence. 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
Quantum state preparation and macroscopic entanglement in gravitational-wave detectors
Long-baseline laser-interferometer gravitational-wave detectors are operating
at a factor of 10 (in amplitude) above the standard quantum limit (SQL) within
a broad frequency band. Such a low classical noise budget has already allowed
the creation of a controlled 2.7 kg macroscopic oscillator with an effective
eigenfrequency of 150 Hz and an occupation number of 200. This result, along
with the prospect for further improvements, heralds the new possibility of
experimentally probing macroscopic quantum mechanics (MQM) - quantum mechanical
behavior of objects in the realm of everyday experience - using
gravitational-wave detectors. In this paper, we provide the mathematical
foundation for the first step of a MQM experiment: the preparation of a
macroscopic test mass into a nearly minimum-Heisenberg-limited Gaussian quantum
state, which is possible if the interferometer's classical noise beats the SQL
in a broad frequency band. Our formalism, based on Wiener filtering, allows a
straightforward conversion from the classical noise budget of a laser
interferometer, in terms of noise spectra, into the strategy for quantum state
preparation, and the quality of the prepared state. Using this formalism, we
consider how Gaussian entanglement can be built among two macroscopic test
masses, and the performance of the planned Advanced LIGO interferometers in
quantum-state preparation
Transverse-Momentum Dependence of the J/psi Nuclear Modification in d+Au Collisions at sqrt(s_NN)=200 GeV
We present measured J/psi production rates in d+Au collisions at sqrt(s_NN) =
200 GeV over a broad range of transverse momentum (p_T=0-14 GeV/c) and rapidity
(-2.2<y<2.2). We construct the nuclear-modification factor R_dAu for these
kinematics and as a function of collision centrality (related to impact
parameter for the R_dAu collision). We find that the modification is largest
for collisions with small impact parameters, and observe a suppression
(R_dAu<1) for p_T<4 GeV/c at positive rapidities. At negative rapidity we
observe a suppression for p_T1) for p_T>2
GeV/c. The observed enhancement at negative rapidity has implications for the
observed modification in heavy-ion collisions at high p_T.Comment: 384 authors, 24 pages, 19 figures, 13 tables. Submitted to Phys. Rev.
C. Plain text data tables for the points plotted in figures for this and
previous PHENIX publications are publicly available at
http://www.phenix.bnl.gov/phenix/WWW/info/data/ppg123_data.htm
Upper limits on the strength of periodic gravitational waves from PSR J1939+2134
The first science run of the LIGO and GEO gravitational wave detectors
presented the opportunity to test methods of searching for gravitational waves
from known pulsars. Here we present new direct upper limits on the strength of
waves from the pulsar PSR J1939+2134 using two independent analysis methods,
one in the frequency domain using frequentist statistics and one in the time
domain using Bayesian inference. Both methods show that the strain amplitude at
Earth from this pulsar is less than a few times .Comment: 7 pages, 1 figure, to appear in the Proceedings of the 5th Edoardo
Amaldi Conference on Gravitational Waves, Tirrenia, Pisa, Italy, 6-11 July
200
Searching for a Stochastic Background of Gravitational Waves with LIGO
The Laser Interferometer Gravitational-wave Observatory (LIGO) has performed
the fourth science run, S4, with significantly improved interferometer
sensitivities with respect to previous runs. Using data acquired during this
science run, we place a limit on the amplitude of a stochastic background of
gravitational waves. For a frequency independent spectrum, the new limit is
. This is currently the most sensitive
result in the frequency range 51-150 Hz, with a factor of 13 improvement over
the previous LIGO result. We discuss complementarity of the new result with
other constraints on a stochastic background of gravitational waves, and we
investigate implications of the new result for different models of this
background.Comment: 37 pages, 16 figure
Improving the sensitivity to gravitational-wave sources by modifying the input-output optics of advanced interferometers
We study frequency dependent (FD) input-output schemes for signal-recycling
interferometers, the baseline design of Advanced LIGO and the current
configuration of GEO 600. Complementary to a recent proposal by Harms et al. to
use FD input squeezing and ordinary homodyne detection, we explore a scheme
which uses ordinary squeezed vacuum, but FD readout. Both schemes, which are
sub-optimal among all possible input-output schemes, provide a global noise
suppression by the power squeeze factor, while being realizable by using
detuned Fabry-Perot cavities as input/output filters. At high frequencies, the
two schemes are shown to be equivalent, while at low frequencies our scheme
gives better performance than that of Harms et al., and is nearly fully
optimal. We then study the sensitivity improvement achievable by these schemes
in Advanced LIGO era (with 30-m filter cavities and current estimates of
filter-mirror losses and thermal noise), for neutron star binary inspirals, and
for narrowband GW sources such as low-mass X-ray binaries and known radio
pulsars. Optical losses are shown to be a major obstacle for the actual
implementation of these techniques in Advanced LIGO. On time scales of
third-generation interferometers, like EURO/LIGO-III (~2012), with
kilometer-scale filter cavities, a signal-recycling interferometer with the FD
readout scheme explored in this paper can have performances comparable to
existing proposals. [abridged]Comment: Figs. 9 and 12 corrected; Appendix added for narrowband data analysi
Search for gravitational wave bursts in LIGO's third science run
We report on a search for gravitational wave bursts in data from the three
LIGO interferometric detectors during their third science run. The search
targets subsecond bursts in the frequency range 100-1100 Hz for which no
waveform model is assumed, and has a sensitivity in terms of the
root-sum-square (rss) strain amplitude of hrss ~ 10^{-20} / sqrt(Hz). No
gravitational wave signals were detected in the 8 days of analyzed data.Comment: 12 pages, 6 figures. Amaldi-6 conference proceedings to be published
in Classical and Quantum Gravit
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