157 research outputs found
Charge-odd correlation of lepton and pion pair production in electron-proton scattering
Charge-odd correlation of the charged pair components produced at
electron-proton scattering can measure three current correlation averaged by
proton state. In general these type correlation can be described by 14
structure functions. We restrict here by consideration of inclusive
distributions of a pair components, which is the light-cone projection of the
relevant hadronic tensor. Besides we consider the point-like approximation for
proton and pion. Numerical estimations show that charge-odd effects can be
measured in exclusive ep -> 2 pi X experiments.Comment: 10 pages, 4 figure
Vacuum polarization radiative correction to the parity violating electron scattering on heavy nuclei
The effect of vacuum polarization on the parity violating asymmetry in the
elastic electron-nucleus scattering is considered. Calculations are performed
in the high-energy approximation with an exact account for the electric field
of the nucleus. It is shown that the radiative correction to the parity
violating asymmetry is logarithmically enhanced and the value of the correction
is about -1%.Comment: 6 pages, 3 figures, REVTex
Bremsstrahlung and pair production processes at low energies, multi-differential cross section and polarization phenomena
Radiative electron-proton scattering is studied in peripheral kinematics,
where the scattered electron and photon move close to the direction of the
initial electron. Even in the case of unpolarized initial electron the photon
may have a definite polarization. The differential cross sections with
longitudinally or transversal polarized initial electron are calculated. The
same phenomena are considered for the production of an electron-positron pair
by the photon, where the final positron (electron) can be also polarized.
Differential distributions for the case of polarized initial photon are given.
Both cases of unscreened and completely screened atomic targets are considered.Comment: 15 pages, 6 figure
Off-shell scattering amplitudes in the double-logarithmic approximation
When scattering amplitudes are calculated in the double-logarithmic
approximation, it is possible to relate the double-logarithmic on-shell and
off-shell amplitudes. Explicit relations are obtained for scattering amplitudes
in QED, QCD, and the ElectroWeak Standard Model. The off-shell amplitudes are
considered in the hard and the Regge kinematic limits. We compare our results
in both the Feynman and Coulomb gauges.Comment: 15 pages, 3 figures; RevTeX
Thermodynamic Geometric Stability of Quarkonia states
We compute exact thermodynamic geometric properties of the non-abelian
quarkonium bound states from the consideration of one-loop strong coupling.
From the general statistical principle, the intrinsic geometric nature of
strongly coupled QCD is analyzed for the Columbic, rising and Regge rotating
regimes. Without any approximation, we have obtained the non-linear mass effect
for the Bloch-Nordsieck rotating strongly coupled quarkonia. For a range of
physical parameters, we show in each cases that there exists a well-defined,
non-degenerate, curved, intrinsic Riemannian manifold. As the gluons become
softer and softer, we find in the limit of the Bloch-Nordsieck resummation that
the strong coupling obtained from the Sudhakov form factor possesses exact
local and global thermodynamic properties of the underlying mesons, kaons and
particles.Comment: 45 pages, 17 figures, Keywords: Thermodynamic Geometry, Quarkonia,
Massive Quarks, QCD Form Factor. PACS: 02.40.-k; 14.40.Pq; 12.40.Nn; 14.70.D
Calcium Transient Registration in Response to Single Stimulation and During Train of Pulses in Mouse Neuromuscular Junction
© 2016, Springer Science+Business Media New York.Calcium (Ca2+) is a key ion involved in transmitter release in chemical synapses. Optical recording of fluorescence changes of Ca2+ indicators is one of the most frequently used methods to measure intracellular Ca2+ dynamics. This technique is based on use of Ca2+-binding fluorescent dyes which change their emission intensity after binding to Ca2+. The most crucial step in this type of experiments is loading of Ca2+ dye. In this paper, we present the method of Ca2+-sensitive dye loading to mammalian nerve endings through the stump of the nerve. We represent Ca2+ transient registered parameters in response to a single motor nerve stimulus. The study of Ca2+ dynamics during high frequency stimulation close to real pattern of synaptic transmission allows us to understand such fundamental process as synaptic plasticity. We describe the results obtained during the registration of Ca2+ transient caused by the rhythmic motor nerve stimulation. Intracellular level of Ca2+ estimated by the amplitude of Ca2+ transient rises with the increase of stimulation frequency. The amplitude of Ca2+ transient decreases after blocking of voltage dependent Ca2+ channels by cadmium. The obtained data showed that detected increase of fluorescence intensity is induced by Ca2+ influx through the voltage-gated Ca2+ channels to the nerve ending during an action potential. This dye-loading method is suitable for registration of presynaptic Ca2+ dynamics under both single nerve stimulus and rhythmic activity
Resummation of double logarithms in electroweak high energy processes
At future linear collider experiments in the TeV range, Sudakov
double logarithms originating from massive boson exchange can lead to
significant corrections to the cross sections of the observable processes.
These effects are important for the high precision objectives of the Next
Linear Collider. We use the infrared evolution equation, based on a gauge
invariant dispersive method, to obtain double logarithmic asymptotics of
scattering amplitudes and discuss how it can be applied, in the case of broken
gauge symmetry, to the Standard Model of electroweak processes. We discuss the
double logarithmic effects to both non-radiative processes and to processes
accompanied by soft gauge boson emission. In all cases the Sudakov double
logarithms are found to exponentiate. We also discuss double logarithmic
effects of a non-Sudakov type which appear in Regge-like processes.Comment: 26 pages, 3 figures, Latex2
Worldline Approach to Forward and Fixed Angle fermion-fermion Scattering in Yang-Mills Theories at High Energies
Worldline techniques are employed to study the general behaviour of the
fermion-fermion collision amplitude at very high energies in a non-abelian
gauge field theory for the forward and fixed angle scattering cases. A central
objective of this work is to demonstrate the simplicity by which the worldline
methodology isolates that sector of the full theory which carries the soft
physics, relevant to each process. Anomalous dimensions pertaining to a given
soft sector are identified and subseuently used to facilitate the
renormalization group running of the respective four point functions. Gluon
reggeization is achieved for forward, while Sudakov suppression is established
for fixed angle scattering.Comment: 28 pages, 10 figures in three file
Comments on operators with large spin
We consider high spin operators. We give a general argument for the
logarithmic scaling of their anomalous dimensions which is based on the
symmetries of the problem. By an analytic continuation we can also see the
origin of the double logarithmic divergence in the Sudakov factor. We show that
the cusp anomalous dimension is the energy density for a flux configuration of
the gauge theory on . We then focus on operators in super Yang Mills which carry large spin and SO(6) charge and show that in
a particular limit their properties are described in terms of a bosonic O(6)
sigma model. This can be used to make certain all loop computations in the
string theory.Comment: 33 pages, 1 figure,v2:reference to more recent work added, minor
correction
Working directly with probabilities in quantum field theory
We present a novel approach to computing transition probabilities in quantum field theory, which allows them to be written directly in terms of expectation values of nested commutators and anti-commutators of field operators, rather than squared matrix elements. We show that this leads to a diagrammatic expansion in which the retarded propagator plays a dominant role. As a result, one is able to see clearly how faster-than-light signalling is prevented between sources and detectors. Finally, we comment on potential implications of this approach for dealing with infra-red divergences
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