59 research outputs found
Decay of accelerated particles
We study how the decay properties of particles are changed by acceleration.
It is shown that under the influence of acceleration (1) the lifetime of
particles is modified and (2) new processes (like the decay of the proton)
become possible. This is illustrated by considering scalar models for the decay
of muons, pions, and protons. We discuss the close conceptual relation between
these processes and the Unruh effect.Comment: Latex2e, 12 pages, 6 Postscript figures included with epsfig, to
appear in Phys. Rev.
Normalization of the covariant three-body bound state vertex function
The normalization condition for the relativistic three nucleon Bethe-Salpeter
and Gross bound state vertex functions is derived, for the first time, directly
from the three body wave equations. It is also shown that the relativistic
normalization condition for the two body Gross bound state vertex function is
identical to the requirement that the bound state charge be conserved, proving
that charge is automatically conserved by this equation.Comment: 24 pages, 9 figures, published version, minor typos correcte
Resonance Model of for Kaon Production in Heavy Ion Collisions
The elementary production cross sections
and are needed to describe
kaon production in heavy ion collisions. The reactions
were studied previously by a resonance model. The model can explain the
experimental data quite well \cite{tsu}. In this article, the total cross
sections at intermediate energies (from the kaon
production threshold to3 GeV of center-of-mass energy) are
calculated for the first time using the same resonance model. The resonances,
and for the reactions, and
, and for the reactions are taken into account coherently as
the intermediate states in the calculations. Also t-channel vector meson exchange is included. The results show that
exchange is neglegible for the
reactions, whereas this meson does not contribute to the reactions. Furthemore, the
contributions to kaon production in heavy ion collisions are not only
non-neglegible but also very different from the
reactions. An argument valid for cannot be extended to
reactions. Therefore, cross sections for including correctly the different isospins must beComment: ( Replaced with corrections of printing errors in the Table. ) 15
pages, Latex file with 4 figures, 1 figure is included in the text. A
compressed uuencode file for 3 figures is appended. (A figure file format was
changed.) Also available upon reques
Chiral-symmetry restoration in the linear sigma model at nonzero temperature and baryon density
We study the chiral phase transition in the linear sigma model with 2 quark
flavors and colors. One-loop calculations predict a first-order phase
transition at both and . We also discuss the phase diagram
and make a comparison with a thermal parametrization of existing heavy-ion
experimental data.Comment: 12 pages, 6 ps-figures, LaTe
Observation of the Higgs Boson of strong interaction via Compton scattering by the nucleon
It is shown that the Quark-Level Linear Model (QLLM) leads
to a prediction for the diamagnetic term of the polarizabilities of the nucleon
which is in excellent agreement with the experimental data. The bare mass of
the meson is predicted to be MeV and the two-photon
width keV. It is argued that the
mass predicted by the QLLM corresponds to the reaction, i.e. to a -channel pole of the reaction.
Large -angle Compton scattering experiments revealing effects of the
meson in the differential cross section are discussed. Arguments are presented
that these findings may be understood as an observation of the Higgs boson of
strong interaction while being part of the constituent quark.Comment: 17 pages, 6 figure
Gauge dependence and matching procedure of a nonrelativistic QED/QCD boundstate formalism
A nonrelativistic boundstate formalism used in contemporary calculations is
investigated. It is known that the effective Hamiltonian of the boundstate
system depends on the choice of gauge. We obtain the transformation charge Q of
the Hamiltonian for an arbitrary infinitesimal change of gauge, by which gauge
independence of the mass spectrum and gauge dependences of the boundstate wave
functions are dictated. We give formal arguments based on the BRST symmetry
supplemented by power countings of Coulomb singularities of diagrams. For
illustration: (1)we calculate Q up to O(1/c), (2)we examine gauge dependences
of diagrams for a decay of a qqbar boundstate up to O(1/c) and show that
cumbersome gauge cancellations can be circumvented by directly calculating Q.
As an application we point out that the present calculations of top quark
momentum distribution in the ttbar threshold region are gauge dependent. We
also show possibilities for incorrect calculations of physical quantities of
boundstates when the on-shell matching procedure is employed. We give a proof
of a justification for the use of the equation of motion to simplify the form
of a local NRQCD Lagrangian. The formalism developed in this work will provide
useful cross checks in computations involving NRQED/NRQCD boundstates.Comment: 30 pages, 15 figures (ver1); Presentations of Introduction and
Conclusion were modified substantially, although none of our findings have
been changed; Side remarks have been added in various parts of the paper.
(ver2); Supplementary remarks and minor corrections (ver3
Nucleon to Delta Weak Excitation Amplitudes in the Non-relativistic Quark Model
We investigate the nucleon to Delta(1232) vector and axial vector amplitudes
in the non-relativistic quark model of the Isgur-Karl variety. A particular
interest is to investigate the SU(6) symmetry breaking, due to color hyperfine
interaction. We compare the theoretical estimates to recent experimental
investigation of the Adler amplitudes by neutrino scattering.Comment: \documentstyle[aps]{revtex}, 21pages; 11 postscript figures. Accepted
for publication by Phys. Rev.
Gravitational phase transition of heavy neutrino matter
In the framework of the Thomas-Fermi model at finite temperature, we show
that a cooling nondegenerate gas of massive neutrinos will undergo a phase
transition in which quasi-degenerate supermassive neutrino stars are formed
through gravitational collapse. For neutrinos in the mass range of 10 to 25 keV
these compact dark objects could mimic the role of supermassive black holes
that are usually assumed to exist at the centres galaxies. Astrophysical
implications and constraints on the neutrino mass are discussed for this
scenario.Comment: 10 pages, LaTex, 4 postscript figure
Condensation effects beyond one loop in the Top-mode Standard Model without gauge bosons
We study dynamical symmetry breaking in the Standard Model including the
next-to-leading order terms. We introduce at a high, but finite, energy scale
Lambda a top quark condensate H={t {bar t}} and derive, using path integral
methods, the effective potential including quadratic fluctuations in the scalar
field H. We neglect the contributions of all components of the massive
electroweak gauge bosons. The existence of a non-trivial minimum in the
effective potential leads to the condition that the cut-off Lambda is limited
from above: Lambda < Lambda_{crit} approx 4.7 m_t^{phys.} (for N_c = 3), and to
a new lower bound for the 4-fermion coupling a = (G N_c Lambda^2)/(8 pi^2) >
1.60. Similar results are obtained if we demand, instead, that the
next-to-leading order contributions not shift the location
z=(m_t^{bare}/Lambda)^2 of the minimum drastically, e.g.~by not more than a
factor of 2. The results are reproduced diagrammatically, where the leading
plus all the next-to-leading order diagrams in the (1/N_c)-expansion are
included. Dominant QCD effects are also included, but their impact on the
numerical results is shown to be small.Comment: 30 pages, LaTeX, 9 figures included in a separate tar-compressed and
uuencoded PostScript file; QCD effects included, formulations improved, new
figures 1a-1
Relativistic quantum effects of Dirac particles simulated by ultracold atoms
Quantum simulation is a powerful tool to study a variety of problems in
physics, ranging from high-energy physics to condensed-matter physics. In this
article, we review the recent theoretical and experimental progress in quantum
simulation of Dirac equation with tunable parameters by using ultracold neutral
atoms trapped in optical lattices or subject to light-induced synthetic gauge
fields. The effective theories for the quasiparticles become relativistic under
certain conditions in these systems, making them ideal platforms for studying
the exotic relativistic effects. We focus on the realization of one, two, and
three dimensional Dirac equations as well as the detection of some relativistic
effects, including particularly the well-known Zitterbewegung effect and Klein
tunneling. The realization of quantum anomalous Hall effects is also briefly
discussed.Comment: 22 pages, review article in Frontiers of Physics: Proceedings on
Quantum Dynamics of Ultracold Atom
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