1,600 research outputs found
Coulomb potential from a particle in uniform ultrarelativistic motion
The Coulomb potential produced by an ultrarelativistic particle (such as a
heavy ion) in uniform motion is shown in the appropriate gauge to factorize
into a longitudinal Dirac delta function of (z - t) times the simple two
dimensional potential solution in the transverse direction. This form makes
manifest the source of the energy independence of the interaction.Comment: 5 pages, latex, revtex source, no figure
Some exact analytical results and a semi-empirical formula for single electron ionization induced by ultrarelativistic heavy ions
The delta function gauge of the electromagnetic potential allows
semiclassical formulas to be obtained for the probability of exciting a single
electron out of the ground state in an ultrarelativistic heavy ion reaction.
Exact formulas have been obtained in the limits of zero impact parameter and
large, perturbative, impact parameter. The perturbative impact parameter result
can be exploited to obtain a semi-empirical cross section formula of the form,
sigma = A ln(gamma) + B, for single electron ionization. A and B can be
evaluated for any combination of target and projectile, and the resulting
simple formula is good at all ultrarelativistic energies. The analytical form
of A and B elucidates a result previously found in numerical calculations:
scaled ionization cross sections decrease with increasing charge of the nucleus
being ionized. The cross section values obtained from the present formula are
in good agreement with recent CERN SPS data from a Pb beam on various nuclear
targets.Comment: 14 pages, latex, revtex source, no figure
The electromagnetic interaction of ultrarelativistic heavy ions
The validity of a delta-function approximation for the electromagnetic
interaction of relativistic heavy ions is investigated. The production of e+e-
pairs, with electron capture, is used as a test of the approximation.Comment: 11 pages, 3 figure
Higher Order QED Calculation of Ultrarelativistic Heavy Ion Production of mu+ mu- Pairs
A higher order QED calculation of the ultraperipheral heavy ion cross section
for mu+ mu- pair production at RHIC and LHC is carried out. The so-called
"Coulomb corrections" lead to an even greater percentage decrease of mu+ mu-
production from perturbation theory than the corresponding decrease for e+ e-
pair production. Unlike the e+ e- case, the finite charge distribution of the
ions (form factor) and the necessary subtraction of impact parameters with
matter overlap are significant effects in calculation an observable
ultraperipheral mu+ mu- total cross section.Comment: 7 pages, 3 figures. Version expanded with explanatory text and two
appendices on form factor treatmen
Two Center Light Cone Calculation of Pair Production Induced by Ultrarelativistic Heavy Ions
An exact solution of the two center time-dependent Dirac equation for pair
production induced by ultrarelativistic heavy ion collisions is presented.
Cross sections to specific final states approach those of perturbation theory.
Multiplicity rates are reduced from perturbation theory.Comment: 22 pages, latex, revtex source, one postscript figur
Nuclear and Particle Astrophysics at CIPANP 2003
In the nuclear and particle astrophysics session of CIPANP 2003 we heard
talks on a number of topics, focused for the most part into four broad areas.
Here we outline the discussions of the standard cosmological model, dark matter
searches, cosmic rays, and neutrino astrophysics. The robustness of theoretical
and experimental programs in all of these areas is very encouraging, and we
expect to have many questions answered, and new ones asked, in time for CIPANP
2006.Comment: 5 pages, uses aipproc.cls, parallel session summary to appear in
proceedings of CIPANP 200
Implications of muon anomalous magnetic moment for supersymmetric dark matter
The anomalous magnetic moment of the muon has recently been measured to be in
conflict with the Standard Model prediction with an excess of 2.6 sigma. Taking
the excess at face value as a measurement of the supersymmetric contribution,
we find that at 95% confidence level it imposes an upper bound of 500 GeV on
the neutralino mass and forbids higgsinos as being the bulk of cold dark
matter. Other implications for the astrophysical detection of neutralinos
include: an accessible minimum direct detection rate, lower bounds on the
indirect detection rate of neutrinos from the Sun and the Earth, and a
suppression of the intensity of gamma-ray lines from neutralino annihilations
in the galactic halo.Comment: 4 pages, 2 figures, revised version accepted for publication in
Physical Review Letter
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