6,113 research outputs found
Direct Photons in Ion Collisions at FAIR Energies
Estimations of prompt photon production at FAIR (Facility for Antiproton and
Ion Research) energies using the extrapolation of existing data are presented.
About prompt with 2 GeV/c per Au+Au central event at
25 AGeV are expected. With the planed beam intensity , 1% interaction
rate and 10% centrality, at CBM (Compressed Baryonic Matter) experiment one can
expect prompt rate ~100/s.
Predictions for direct photons by some generators (PYTHIA, UrQMD, RQMD, HSD,
HIJING) are analyzed. One of the main sources of direct photons (due to meson
scatterings ) is not implemented in
the heavy-ion generators. Corresponding cross-sections for this source have
been prepared for implementation into the HSD code.
Main experimental methods to study direct photons (subtraction method,
momentum correlations method and internal conversion method) are shortly
reviewed. High intensity beam, good tracking and good particle
identification of the CBM detector favor to measure direct photons by all the
methods.Comment: 7 pages,5 figures,Talk at Baldin ISHEPP XVIII, Dubna, 25 - 30
September 200
Surface-to-volume ratio with oscillating gradients
Restrictions to diffusion result in the dispersion of the bulk diffusion
coefficient. We derive the exact universal high-frequency behavior of the
diffusion coefficient in terms of the surface-to-volume ratio of the
restrictions. This frequency dependence can be applied to quantify structure of
complex samples with NMR using oscillating field gradients and static-gradient
CPMG. We also demonstrate the inter-relations between different equivalent
diffusion metrics, and describe how to calculate the effect of restrictions for
arbitrary gradient waveforms.Comment: 6 pages, 1 figur
Natural scale of cosmological constant in seesaw mechanism with broken SUSY
The cosmological constant is inherently determined by the scale of breaking
down supersymmetry in the mechanism of seesaw fluctuations of two
vacuum-states.Comment: 4 pages, revtex4 class, reference adde
The slowly passage through the resonances and wave packets with the different carriers
Solution of the nonlinear Klein-Gordon equation perturbed by small external
force is investigated. The perturbation is represented by finite collections of
harmonics. The frequencies of the perturbation vary slowly and pass through the
resonant values consecutively. The resonances lead to the sequence of the wave
packets with the different fast oscillated carriers. Full asymptotic
description of this process is presented.Comment: 24 pages, LaTe
Scattering of solitons on resonance
We investigate a propagation of solitons for nonlinear Schrodinger equation
under small driving force. The driving force passes the resonance. The process
of scattering on the resonance leads to changing of number of solitons. After
the resonance the number of solitons depends on the amplitude of the driving
force.Comment: LaTeX, 10 page
Properties of potential modelling three benchmarks: the cosmological constant, inflation and three generations
We argue for a model of low-energy correction to the inflationary potential
as caused by the gauge-mediated breaking down the supersymmetry at the scale of
\mu_\textsc{x}\sim 10^4 GeV, that provides us with the seesaw mechanism of
thin domain wall fluctuations in the flat vacuum. The fluctuations are
responsible for the vacuum with the cosmological constant at the scale of
eV suppressed by the Planckian mass
via \mu_\Lambda\sim\mu_\textsc{x}^2/m_\mathtt{Pl}. The appropriate vacuum
state is occupied after the inflation with quartic coupling constant
\lambda\sim\mu_\textsc{x}/m_\mathtt{Pl}\sim 10^{-14} inherently related with
the bare mass scale of \widetilde m\sim\sqrt{\mu_\textsc{x}m_\mathtt{Pl}}\sim
10^{12} GeV determining the thickness of domain walls . Such the parameters of potential are still marginally
consistent with the observed inhomogeneity of matter density in the Universe.
The inflationary evolution suggests the vacuum structure compatible with three
fermionic generations of matter as well as with observed hierarchies of masses
and mixing in the Standard Model.Comment: 12 pages, 1 figure, revtex4 class, references adde
Renormalization group analysis of cosmological constraint on the mass of Higgs scalar
The Higgs boson of Standard Model, minimally coupled to the gravitation, is
not able to produce the inflation of early Universe if its mass exceeds the
threshold value, which is equal to m_H^{min} = 142 GeV in the tree
approximation for the scalar potential. Two-loop corrections modify the
estimate as m_H^{min} = 150 \pm 3 GeV, so that higher-order corrections of
perturbation theory are completely under control, though they are numerically
important in respect of experimental searches.Comment: 6 page
The capture into parametric autoresonance
In this work we show that the capture into parametric resonance may be
explained as the pitchfork bifurcation in the primary parametric resonance
equation. We prove that the solution close to the moment of the capture is
described by the Painleve-2 equation. We obtain the connection formulas for the
asymptotic solution of the primary parametric resonance equation before and
after the capture using the matching of the asymptotic expansions.Comment: LaTeX, 21 pages, 3 figure
The surface density of holographic entropy
On the basis of postulates for the holographic description of gravity and the
introduction of entropic force, for static sources we derive the universal law:
the entropy of a holographic screen is equal to quarter of its area in the
Planck system of units.Comment: 6 page
Asymptotic description of nonlinear resonance
We study a hard regime of stimulation of two-frequency oscillations in the
main resonance equation with a fast oscillating external force: \ve i \psi' +
|\psi|^2\psi = \exp\big(it^2/ (2\ve)\big), 0<\ve\ll1. This phenomenon is
caused by resonance between an eigenmode and the external force. The asymptotic
solution before, inside and after the resonance layer is studied in detail and
matched.Comment: LaTeX, 48 pages, two figure
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