503 research outputs found
Preliminary Results on gamma gamma -> Ks K pi from CLEO
We analyzed 13.8 fb^{-1} of the integrated e+e- luminosity collected at 10.6
GeV center-of-mass energy with the CLEO II and II.V detectors to study
exclusive two-photon production of single hadronic resonances. We searched for
hadrons decaying into Ks K pi when both leptons remain undetected. In this
analysis we studied the detection efficiency and evaluated systematic errors
using independent data samples. We estimated 90% CL upper limits on the
products of the two-photon partial widths of (pseudo)scalar hadrons with masses
below 1.7 GeV/c2 and their branching fractions into Ks K pi. Our preliminary
results are marginally consistent with the first observation of eta(1440) in
two-photon collisions by the L3 experiment.Comment: 4 pages, 1 figure, proceedings contribution for PANIC'0
Tagging Two-Photon Production at the LHC
Tagging two-photon production offers a significant extension of the LHC
physics programme. Effective luminosity of high-energy gamma-gamma collisions
reaches 1% of the proton-proton luminosity and the standard detector techniques
used for measuring very forward proton scattering should allow for a reliable
extraction of interesting two-photon interactions. Particularly exciting is a
possibility of detecting two-photon exclusive Higgs boson production at the
LHC.Comment: 9 pages and 4 figure
Towards a Precise Parton Luminosity Determination at the CERN LHC
A new approach to determine the LHC luminosity is investigated. Instead of
employing the proton-proton luminosity measurement, we suggest to measure
directly the parton-parton luminosity. It is shown that the electron and muon
pseudorapidity distributions, originating from the decay of W+, W- and Z0
bosons produced at 14 TeV pp collisions (LHC), constrain the x distributions of
sea and valence quarks and antiquarks in the range from about 3 x 10**-4 to
about 10**-1 at a Q**2 of about 10**4 GeV**2. Furthermore, it is demonstrated
that, once the quark and antiquark structure functions are constrained from the
W+,W- and Z0 production dynamics, other quark-antiquark related scattering
processes at the LHC like q-qbar --> W+W- can be predicted accurately. Thus,
the lepton pseudorapidity distributions provide the key to a precise parton
luminosity monitor at the LHC, with accuracies of about +-1% compared to the so
far considered goal of +-5%.Comment: plain tex, 14 pages, 5 figure
Results of the Baikal experiment on observations of macroscopic nonlocal correlations in reverse time
Although the general theory macroscopic quantum entanglement of is still in
its infancy, consideration of the matter in the framework of action-at-a
distance electrodynamics predicts for the random dissipative processes
observability of the advanced nonlocal correlations. These correlations were
really revealed in our previous experiments with some large-scale
heliogeophysical processes as the source ones and the lab detectors as the
probe ones. Recently a new experiment has been performing on the base of Baikal
Deep Water Neutrino Observatory. The thick water layer is an excellent shield
against any local impacts on the detectors. The first annual series 2012/2013
has demonstrated that detector signals respond to the heliogeophysical
processes and causal connection of the signals directed downwards: from the
Earth surface to the Baikal floor. But this nonlocal connection proved to be in
reverse time. In addition advanced nonlocal correlation of the detector signal
with the regional source-process: the random component of hydrological activity
in the upper layer was revealed and the possibility of its forecast on nonlocal
correlations was demonstrated. But the strongest macroscopic nonlocal
correlations are observed at extremely low frequencies, that is at periods of
several months. Therefore the above results should be verified in a longer
experiment. We verify them by data of the second annual series 2013/2014 of the
Baikal experiment. All the results have been confirmed, although some
quantitative parameters of correlations and time reversal causal links turned
out different due to nonstationarity of the source-processes. A new result is
displaying of the advanced response of nonlocal correlation detector to the
earthquake. This opens up the prospect of the earthquake forecast on the new
physical principle, although further confirmation in the next events is
certainly needed.Comment: 9 pages, 9 figure
Optical polarization observations with the MASTER robotic net
We present results of optical polarization observations performed with the
MASTER robotic net for three types of objects: gamma-ray bursts, supernovae,
and blazars. For the Swift gamma-ray bursts GRB100906A, GRB110422A, GRB121011A,
polarization observations were obtained during very early stages of optical
emission. For GRB100906A it was the first prompt optical polarization
observation in the world. Photometry in polarizers is presented for Type Ia
Supernova 2012bh during 20 days, starting on March 27, 2012. We find that the
linear polarization of SN 2012bh at the early stage of the envelope expansion
was less than 3%. Polarization measurements for the blazars OC 457, 3C 454.3,
QSO B1215+303, 87GB 165943.2+395846 at single nights are presented. We infer
the degree of the linear polarization and polarization angle. The blazars OC
457 and 3C 454.3 were observed during their periods of activity. The results
show that MASTER is able to measure substantially polarized light; at the same
time it is not suitable for determining weak polarization (less than 5%) of dim
objects (fainter than 16). Polarimetric observations of the optical
emission from gamma-ray bursts and supernovae are necessary to investigate the
nature of these transient objects.Comment: 31 pages, 12 figures, 4 tables; Exposure times in Table 2 have been
correcte
Production of relativistic positronium in collisions of photons and electrons with nuclei and atoms
We consider the production of ultrarelativistic positronium (Ps) in and processes where is an atom or a nucleus
with charge . For the photoproduction of para- and ortho-Ps and the
electroproduction of para-Ps we obtain the most complete description compared
with previous works. It includes high order corrections and
polarization effects. The accuracy of the obtained cross sections is determined
by omitted terms of the order of the inverse Ps Lorentz factor squared. The
studied high order multi-photon electroproduction of ortho-Ps dominates for the
collision of electrons with heavy atoms over the bremsstrahlung production from
the electron via a virtual photon proposed by Holvik and Olsen. Our results
complete and correct the studies of those authors.Comment: 19 pages, 9 figures, RevTex; v2: minor corrections for the accuracy
of the results, a discussion of the literature added in a footnote, one
additional reference; v3: diagram of Fig.2 correcte
Virtual photon structure functions and positivity constraints
We study the three positivity constraints among the eight virtual photon
structure functions, derived from the Cauchy-Schwarz inequality and which are
hence model-independent. The photon structure functions obtained from the
simple parton model show quite different behaviors in a massive quark or a
massless quark case, but they satisfy, in both cases, the three positivity
constraints. We then discuss an inequality which holds among the unpolarized
and polarized photon structure functions , and
, in the kinematic region , where is the mass squared of the probe (target) photon, and we examine
whether this inequality is satisfied by the perturbative QCD results.Comment: 24 pages, 13 eps figure
Equivalent Photon Approach to Simultaneous Excitation in Heavy Ion Collision
We apply the Equivalent Photon Approximation to calculate cross sections for
the simultaneous excitation of two heavy ions in relativistic collisions. We
study especially the excitation of two nuclei to a 1- - state and show that the
equations are symmetric with respect to both ions. We also examine the limit in
which the excitation energy of one of the nuclei goes to zero, which gives the
elastic case. Finally a few remarks about the limits of this approach are made.Comment: 9 pages REVTex, 4 Figures included, see also
http://www.phys.washington.edu/~hencken
- …