69 research outputs found
Unruh quantization in presence of a condensate
We have shown that the Unruh quantization scheme can be realized in Minkowski
spacetime in the presence of Bose-Einstein condensate containing infinite
average number of particles in the zero boost mode and located basically inside
the light cone. Unlike the case of an empty Minkowski spacetime the condensate
provides the boundary conditions necessary for the Fulling quantization of the
part of the field restricted only to the Rindler wedge of Minkowski spacetime.Comment: 4 page
An example of a uniformly accelerated particle detector with non-Unruh response
We propose a scalar background in Minkowski spacetime imparting constant
proper acceleration to a classical particle. In contrast to the case of a
constant electric field the proposed scalar potential does not create
particle-antiparticle pairs. Therefore an elementary particle accelerated by
such field is a more appropriate candidate for an "Unruh-detector" than a
particle moving in a constant electric field. We show that the proposed
detector does not reveal the universal thermal response of the Unruh type.Comment: 12 pages, 1 figur
Analysis of CLAS data on double charge pion electroproduction
Recent developments in phenomenological analysis of the CLAS data on 2
electroproduction are presented. The contributions from isobar channels and
, electrocouplings at from 0.25 to 0.6
GeV were determined from the analysis of comprehensive data on differential
and fully integrated 2 cross sections. Experiment Numbers: E94-005 Group:
Hall BComment: Paper compiled for NSTAR2007 meetin
Quantum field aspect of Unruh problem
It is shown using both conventional and algebraic approach to quantum field
theory that it is impossible to perform quantization on Unruh modes in
Minkowski spacetime. Such quantization implies setting boundary condition for
the quantum field operator which changes topological properties and symmetry
group of spacetime and leads to field theory in two disconnected left and right
Rindler spacetimes. It means that "Unruh effect" does not exist.Comment: LaTeX, 13 pages, 1 figur
Long- and short-term earthquake prediction in Kamchatka
This paper presents the results of long- and short-term earthquake prediction obtained during 1971–1974. They can be summarized as follows:
The map of long-term prediction for the Kurile—Kamchatka zone compiled in 1965 and supplemented in 1972 by S.A. Fedotov is in good agreement (in four of four possible cases) with recorded seismicity.
The results obtained allow us to suppose that the areas for which the log (Ep/Es) of small earthquakes is low may be the areas of future large earthquakes.
Prediction of active periods for the Kamchatka earthquakes with M > 7 has been made on the basis of studying the correlation of seismicity with the lunar tide with a 18.6-year period. A possibility has been found for using the phenomenon of “induced foreshocks” for earthquake prediction, i.e., when a large remote earthquake induces small preceding events in the zone of preparation of a large earthquake.
The following three methods were used for operative short-term prediction of the time and place of future earthquakes with M > 5.5.
1.(1) Use of specific electrotelluric field anomalies, from 5 to 20 days in duration, which are recorded by a specially designed network of stations.
2.(2) Method of Vp/Vs anomalies. The anomalously high and low Vp/Vs values for a seismic station point to the possibility of large earthquakes near the latter.
3.(3) The earthquake statistics method described by Fedotov et al. in 1972.
Short-term seismic prediction is being made twice a week in two versions: Forecast I (for the whole of Kamchatka) and Forecast II (for each of six overlapping segments of the Kamchatka seismic zone).
This paper discusses the results of successful testing of short-term earthquake prediction during two years. During the “alarm” periods the probability of large earthquakes is double the average.
Paper presented at the Symposium on Earthquake Forerunners Searching, Tashkent, May 26–June 1, 1974
Electroexcitation of nucleon resonances
We review recent progress in the investigation of the electroexcitation of
nucleon resonances, both in experiment and in theory. The most accurate results
have been obtained for the electroexcitation amplitudes of the four lowest
excited states, which have been measured in a range of Q2 up to 8 and 4.5 GeV2
for the Delta(1232)P33, N(1535)S11 and N(1440)P11, N(1520)D13}, respectively.
These results have been confronted with calculations based on lattice QCD,
large-Nc relations, perturbative QCD (pQCD), and QCD-inspired models. The
amplitudes for the Delta(1232) indicate large pion-cloud contributions at low
Q2 and don't show any sign of approaching the pQCD regime for Q2<7 GeV2.
Measured for the first time, the electroexcitation amplitudes of the Roper
resonance, N(1440)P11, provide strong evidence for this state as a
predominantly radial excitation of a three-quark (3q) ground state, with
additional non-3-quark contributions needed to describe the low Q2 behavior of
the amplitudes. The longitudinal transition amplitude for the N(1535)S11 was
determined and has become a challenge for quark models. Explanations may
require large meson-cloud contributions or alternative representations of this
state. The N(1520)D13 clearly shows the rapid changeover from helicity-3/2
dominance at the real photon point to helicity-1/2 dominance at Q2 > 0.5 GeV2,
confirming a long-standing prediction of the constituent quark model. The
interpretation of the moments of resonance transition form factors in terms of
transition transverse charge distributions in infinite momentum frame is
presented.Comment: 70 pages, 46 figures, will appear in Progress in Particle and Nuclear
Physics, v.67, p.1, 201
Measurement of the nuclear multiplicity ratio for hadronization at CLAS
The influence of cold nuclear matter on lepto-production of hadrons in
semi-inclusive deep inelastic scattering is measured using the CLAS detector in
Hall B at Jefferson Lab and a 5.014 GeV electron beam. We report the
multiplicity ratios for targets of C, Fe, and Pb relative to deuterium as a
function of the fractional virtual photon energy transferred to the
and the transverse momentum squared of the . We find that the
multiplicity ratios for are reduced in the nuclear medium at high
and low , with a trend for the transverse momentum to be
broadened in the nucleus for large .Comment: Submitted to Phys. Lett.
Demonstration of a novel technique to measure two-photon exchange effects in elastic scattering
The discrepancy between proton electromagnetic form factors extracted using
unpolarized and polarized scattering data is believed to be a consequence of
two-photon exchange (TPE) effects. However, the calculations of TPE corrections
have significant model dependence, and there is limited direct experimental
evidence for such corrections. We present the results of a new experimental
technique for making direct comparisons, which has the potential to
make precise measurements over a broad range in and scattering angles. We
use the Jefferson Lab electron beam and the Hall B photon tagger to generate a
clean but untagged photon beam. The photon beam impinges on a converter foil to
generate a mixed beam of electrons, positrons, and photons. A chicane is used
to separate and recombine the electron and positron beams while the photon beam
is stopped by a photon blocker. This provides a combined electron and positron
beam, with energies from 0.5 to 3.2 GeV, which impinges on a liquid hydrogen
target. The large acceptance CLAS detector is used to identify and reconstruct
elastic scattering events, determining both the initial lepton energy and the
sign of the scattered lepton. The data were collected in two days with a
primary electron beam energy of only 3.3 GeV, limiting the data from this run
to smaller values of and scattering angle. Nonetheless, this measurement
yields a data sample for with statistics comparable to those of the
best previous measurements. We have shown that we can cleanly identify elastic
scattering events and correct for the difference in acceptance for electron and
positron scattering. The final ratio of positron to electron scattering:
for GeV and
Precise Measurements of Beam Spin Asymmetries in Semi-Inclusive production
We present studies of single-spin asymmetries for neutral pion
electroproduction in semi-inclusive deep-inelastic scattering of 5.776 GeV
polarized electrons from an unpolarized hydrogen target, using the CEBAF Large
Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator
Facility. A substantial amplitude has been measured in the
distribution of the cross section asymmetry as a function of the azimuthal
angle of the produced neutral pion. The dependence of this amplitude
on Bjorken and on the pion transverse momentum is extracted with
significantly higher precision than previous data and is compared to model
calculations.Comment: to be submitted PL
A Bayesian analysis of pentaquark signals from CLAS data
We examine the results of two measurements by the CLAS collaboration, one of
which claimed evidence for a pentaquark, whilst the other found no
such evidence. The unique feature of these two experiments was that they were
performed with the same experimental setup. Using a Bayesian analysis we find
that the results of the two experiments are in fact compatible with each other,
but that the first measurement did not contain sufficient information to
determine unambiguously the existence of a . Further, we suggest a
means by which the existence of a new candidate particle can be tested in a
rigorous manner.Comment: 5 pages, 3 figure
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