3,563 research outputs found
Semiconservative quasispecies equations for polysomic genomes: The general case
This paper develops a formulation of the quasispecies equations appropriate
for polysomic, semiconservatively replicating genomes. This paper is an
extension of previous work on the subject, which considered the case of haploid
genomes. Here, we develop a more general formulation of the quasispecies
equations that is applicable to diploid and even polyploid genomes.
Interestingly, with an appropriate classification of population fractions, we
obtain a system of equations that is formally identical to the haploid case. As
with the work for haploid genomes, we consider both random and immortal DNA
strand chromosome segregation mechanisms. However, in contrast to the haploid
case, we have found that an analytical solution for the mean fitness is
considerably more difficult to obtain for the polyploid case. Accordingly,
whereas for the haploid case we obtained expressions for the mean fitness for
the case of an analogue of the single-fitness-peak landscape for arbitrary
lesion repair probabilities (thereby allowing for non-complementary genomes),
here we solve for the mean fitness for the restricted case of perfect lesion
repair.Comment: 16 pages, 3 figure
Results from RHIC with Implications for LHC
Results from the PHENIX experiment at RHIC in p-p and Au+Au collisions are
reviewed from the perspective of measurements in p-p collisions at the CERN-ISR
which serve as a basis for many of the techniques used. Issues such as J/Psi
suppression and hydrodynamical flow in A+A collisions require data from
LHC-Ions for an improved understanding. Suppression of high pT particles in
Au+Au collisions, first observed at RHIC, also has unresolved mysteries such as
the equality of the suppression of inclusive pi0 (from light quarks and gluons)
and direct-single electrons (from the decay of heavy quarks) in the transverse
momentum range 4< pT < 9 GeV/c. This disfavors a radiative explanation of
suppression and leads to a fundamental question of whether the Higgs boson
gives mass to fermions. Observation of an exponential distribution of direct
photons in central Au+Au collisions for 1< pT <2 GeV/c where hard-processes are
negligible and with no similar exponential distribution in p-p collisions
indicates thermal photon emission from the medium at RHIC, making PHENIX at the
moment ``the hottest experiment in Physics''.Comment: Invited lectures at the International School of Subnuclear Physics,
47th Course, "The most unexpected at LHC and the status of High Energy
Frontier'', Erice, Sicily, Italy, August 29-September 7. 2009. 32 pages, 22
figure
A preliminary description of the Chemical Camera
Spinning cryostat, or chemical camera, for sampling supersonic gas stream and recording chemical kinetic
Why the xE distribution triggered by a leading particle does not measure the fragmentation function but does measure the ratio of the transverse momenta of the away-side jet to the trigger-side jet
Hard-scattering of point-like constituents (or partons) in p-p collisions was
discovered at the CERN-ISR in 1972 by measurements utilizing inclusive single
or pairs of hadrons with large transverse momentum (). It was generally
assumed, following Feynman, Field and Fox, as shown by data from the CERN-ISR
experiments, that the distribution of away side hadrons from a single
particle trigger [with ], corrected for of fragmentation would
be the same as that from a jet-trigger and follow the same fragmentation
function as observed in or DIS. PHENIX attempted to measure the
fragmentation function from the away side
distribution of charged particles triggered by a in p-p collisions at
RHIC and showed by explicit calculation that the distribution is actually
quite insensitive to the fragmentation function. Illustrations of the original
arguments and ISR results will be presented. Then the lack of sensitivity to
the fragmentation function will be explained, and an analytic formula for the
distribution given, in terms of incomplete Gamma functions, for the case
where the fragmentation function is exponential. The away-side distribution in
this formulation has the nice property that it both exhibits scaling and
is directly sensitive to the ratio of the away jet to that of
the trigger jet, , and thus can be used, for example, to measure
the relative energy loss of the two jets from a hard-scattering which escape
from the medium in A+A collisions. Comparisons of the analytical formula to
RHIC measurements will be presented, including data from STAR and PHENIX,
leading to some interesting conclusions.Comment: 6 pages, 5 figures, Proceedings of Poster Session, 19th International
Conference on Ultra-Relativistic Nucleus-Nucleus Collisions (Quark Matter
2006), November 14-20, 2006, Shanghai, P. R. Chin
From the ISR to RHIC--measurements of hard-scattering and jets using inclusive single particle production and 2-particle correlations
Hard scattering in p-p collisions, discovered at the CERN ISR in 1972 by the
method of leading particles, proved that the partons of Deeply Inelastic
Scattering strongly interacted with each other. Further ISR measurements
utilizing inclusive single or pairs of hadrons established that high pT
particles are produced from states with two roughly back-to-back jets which are
the result of scattering of constituents of the nucleons as desribed by Quantum
Chromodynamics (QCD), which was developed during the course of these
measurements. These techniques, which are the only practical method to study
hard-scattering and jet phenomena in Au+Au central collisions at RHIC energies,
are reviewed, as an introduction to present RHIC measurements.Comment: To appear in the proceedings of the workshop on Correlations and
Fluctuations in Relativistic Nuclear Collisions, MIT, Cambridge, MA, April
21-23, 2005, 10 pages, 9 figures, Journal of Physics: Conference Proceeding
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