470 research outputs found
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
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
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
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
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
Ioffe-time distribution of quarks in the photon
We have analysed the Ioffe-time distribution of quarks in virtual photons
using Operator Product Expansion of the correlation function that determines
the matrix element of the corresponding quark string operator. The distribution
for a transversally polarised photon admits a spectral representation which can
be continued to the on-shell region . The resulting model Ioffe-time
distribution turns out to be larger than parametrisations of the available
data. This result is linked to the slope of the quark
distribution at the origin, which comes out too large as well.Comment: 12 pages, LaTex, one uuencoded figur
Probing partonic structure in gamma* gamma -> pi pi near threshold
Hadron pair production gamma* gamma -> h hbar in the region where the c.m.
energy is much smaller than the photon virtuality can be described in a
factorized form, as the convolution of a partonic handbag diagram and
generalized distribution amplitudes which are new non-perturbative functions
describing the exclusive fragmentation of a quark-antiquark pair into two
hadrons. Scaling behavior and a selection rule on photon helicity are
signatures of this mechanism. The case where h is a pion is emphasized.Comment: 8 pages, 1 figure, LaTeX2
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