990 research outputs found
Do neutrino oscillations allow an extra phenomenological parameter?
The quantity introduced recently in the phenomenological description of
neutrino oscillations is in fact not a free parameter, but a fixed number.Comment: 2 pages, LaTeX 2e style articl
The casuality and/or energy-momentum conservation constraints on QCD amplitudes in small x regime
The causality and/or the energy-momentum constraints on the amplitudes of
high energy processes are generalized to QCD. The constraints imply that the
energetic parton may experience at most one inelastic collision only and that
the number of the constituents in the light cone wave function of the
projectile is increasing with the collision energy and the atomic number.Comment: 24 pages,8 figures. The paper is streamlined, some references are
changed and misprints are eliminate
On the behaviour of single scale hard small processes in QCD near the black disc limit
We argue that at sufficiently small Bjorken where pQCD amplitude rapidly
increases with energy and violates probability conservation the shadowing
effects in the single-scale small hard QCD processes can be described by an
effective quantum field theory of interacting quasiparticles. The
quasiparticles are the perturbative QCD ladders. We find, within the WKB
approximation, that the smallness of the QCD coupling constant ensures the
hierarchy among many-quasiparticle interactions evaluated within physical
vacuum and in particular, the dominance in the Lagrangian of the triple
quasiparticle interaction. It is explained that the effective field theory
considered near the perturbative QCD vacuum contains a tachyon relevant for the
divergency of the perturbative QCD series at sufficiently small . We solve
the equations of motion of the effective field theory within the WKB
approximation and find the physical vacuum and the transitions between the
false (perturbative) and physical vacua. Classical solutions which dominate
transitions between the false and physical vacua are kinks that cannot be
decomposed into perturbative series over the powers of . These kinks
lead to color inflation and the Bose-Einstein condensation of quasiparticles.
The account of the quantum fluctuations around the WKB solution reveals the
appearance of the "massless" particles-- "phonons". It is explained that
"phonons" are relevant for the black disc behaviour of small processes,
leading to a Froissart rise of the cross-section. The condensation of the
ladders produces a color network occupying a "macroscopic" longitudinal volume.
We discuss briefly the possible detection of new QCD effects.Comment: 24 pages, 1 Figure. References added, and several misprints
eliminate
Production of electroweak bosons in e+e- annihilation at high energies
Production of electroweak bosons in e+e- annihilation into quarks and into
leptons at energies much greater than 100 Gev is considered. We account for
double-logarithmic contributions to all orders in electroweak couplings. It is
assumed that the bosons are emitted in the multi-Regge kinematics. The explicit
expressions for the scattering amplitudes of the process are obtained. It is
shown that the cross sections of the photon and Z production have the identical
energy dependence and asymptotically their ratio depends only on the Weinberg
angle whereas the energy dependence of the cross section of the W production is
suppressed by factor s^{-0.4} compared to them.Comment: Revtex4, 16 pages, 7 figures, 2 table
A gamma-ray testing technique for spacecraft
The simulated cosmic radiation effect on a spacecraft structure is evaluated by gamma ray testing in relation to structural thickness. A drawing of the test set-up is provided and measurement errors are discussed
Enhanced Pomeron diagrams: re-summation of unitarity cuts
Unitarity cuts of enhanced Pomeron diagrams are analyzed in the framework of
the Reggeon Field Theory. Assuming the validity of the
Abramovskii-Gribov-Kancheli cutting rules, we derive a complete set of cut
non-loop enhanced graphs and observe important cancellations between certain
sub-classes of the latter. We demonstrate also how the present method can be
generalized to take into consideration Pomeron loop contributions
Breakdown of PCAC in diffractive neutrino interactions
We test the hypothesis of partially conserved axial current (PCAC) in high
energy diffractive neutrino production of pions. Since the pion pole
contribution to the Adler relation (AR) is forbidden by conservation of the
lepton current, the heavier states, like the a_1 pole, \rho-\pi-cut, etc.,
control the lifetime of the hadronic fluctuations of the neutrino. We evaluate
the deviation from the AR in diffractive neutrino-production of pions on proton
and nuclear targets. At high energies, when all the relevant time scales
considerably exceed the size of the target, the AR explicitly breaks down on an
absorptive target, such as a heavy nucleus. In this regime, close to the black
disc limit, the off-diagonal diffractive amplitudes vanish, while the diagonal
one, \pi->\pi, which enters the AR, maximizes and saturates the unitarity
bound. At lower energies, in the regime of short lifetime of heavy hadronic
fluctuations the AR is restored, i.e. it is not altered by the nuclear effects.Comment: 10 pages, 5 figure
Monte Carlo treatment of hadronic interactions in enhanced Pomeron scheme: I. QGSJET-II model
The construction of a Monte Carlo generator for high energy hadronic and
nuclear collisions is discussed in detail. Interactions are treated in the
framework of the Reggeon Field Theory, taking into consideration enhanced
Pomeron diagrams which are resummed to all orders in the triple-Pomeron
coupling. Soft and "semihard" contributions to the underlying parton dynamics
are accounted for within the "semihard Pomeron" approach. The structure of cut
enhanced diagrams is analyzed; they are regrouped into a number of subclasses
characterized by positively defined contributions which define partial weights
for various "macro-configurations" of hadronic final states. An iterative
procedure for a Monte Carlo generation of the structure of final states is
described. The model results for hadronic cross sections and for particle
production are compared to experimental data
Total and diffractive cross sections in enhanced Pomeron scheme
For the first time, a systematic analysis of the high energy behavior of
total and diffractive proton-proton cross sections is performed within the
Reggeon Field Theory framework, based on the resummation of all significant
contributions of enhanced Pomeron diagrams to all orders with respect to the
triple-Pomeron coupling. The importance of different classes of enhanced graphs
is investigated and it is demonstrated that absorptive corrections due to
"net"-like enhanced diagrams and due to Pomeron "loops" are both significant
and none of those classes can be neglected at high energies. A comparison with
other approaches based on partial resummations of enhanced diagrams is
performed. In particular, important differences are found concerning the
predicted high energy behavior of total and single high mass diffraction
proton-proton cross sections, with our values of at
TeV being some % higher and with the energy rise of
saturating well below the LHC energy. The main
causes for those differences are analyzed and explained
Electroweak 2 -> 2 amplitudes for electron-positron annihilation at TeV energies
The non-radiative scattering amplitudes for electron-positron annihilation
into quark and lepton pairs in the TeV energy range are calculated in the
double-logarithmic approximation. The expressions for the amplitudes are
obtained using infrared evolution equations with different cut-offs for virtual
photons and for W and Z bosons, and compared with previous results obtained
with an universal cut-off.Comment: Revtex4, 17 pages, 7 figures. Some minor changes made, more refs
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