1,861 research outputs found
Kinetic Regimes and Cross-Over Times in Many-Particle Reacting Systems
We study kinetics of single species reactions ("A+A -> 0") for general local
reactivity Q and dynamical exponent z (rms displacement x_t ~ t^{1/z}.) For
small molecules z=2, whilst z=4,8 for certain polymer systems. For dimensions d
above the critical value d_c=z, kinetics are always mean field (MF). Below d_c,
the density n_t initially follows MF decay, n_0 - n_t ~ n_0^2 Q t. A 2-body
diffusion-controlled regime follows for strongly reactive systems (Q>Qstar ~
n_0^{(z-d)/d}) with n_0 - n_t ~ n_0^2 x_t^d. For Q<Qstar, MF kinetics persist,
with n_t ~ 1/Qt. In all cases n_t ~ 1/x_t^d at the longest times. Our analysis
avoids decoupling approximations by instead postulating weak physically
motivated bounds on correlation functions.Comment: 10 pages, 1 figure, uses bulk2.sty, minor changes, submitted to
Europhysics Letter
Recent progress on isospin breaking corrections and their impact on the muon g-2 value
We describe some recent results on isospin breaking corrections which are of
relevance for predictions of the leading order hadronic contribution to the
muon anomalous magnetic moment (amuhadLO) when using tau lepton data. When
these corrections are applied to the new combined data on the pi^+pi^0 spectral
function, the prediction for amuhadLO based on tau lepton data gets closer to
the one obtained using e^+e^- data.Comment: 6 pages, 3 figures, Proceedings of the PhiPsi09 Workshop, Oct. 13-16,
2009, Beijing, China. Some typos corrected, and the FSR correction used in a
previous work is added to Table
Hadron Production via e+e- Collisions with Initial State Radiation
A novel method of studying e+e- annihilation into hadrons using initial state
radiation at e+e- colliders is described. After brief history of the method,
its theoretical foundations are considered. Numerous experiments in which
exclusive cross sections of e+e- annihilation into hadrons below the
center-of-mass energy of 5 GeV have been measured are presented. Some
applications of the results obtained to fundamental tests of the Standard Model
are listed.Comment: 50 pages, 88 figures, accepted for publication in Rev. Mod. Phy
Coarsening in a Driven Ising Chain with Conserved Dynamics
We study the low-temperature coarsening of an Ising chain subject to
spin-exchange dynamics and a small driving force. This dynamical system reduces
to a domain diffusion process, in which entire domains undergo nearest-neighbor
hopping, except for the shortest domains -- dimers -- which undergo long-range
hopping. This system is characterized by two independent length scales: the
average domain length L(t)~t^{1/2} and the average dimer hopping distance l(t)~
t^{1/4}. As a consequence of these two scales, the density C_k(t) of domains of
length k does not obey scaling. This breakdown of scaling also leads to the
density of short domains decaying as t^{-5/4}, instead of the t^{-3/2} decay
that would arise from pure domain diffusion.Comment: 7 pages, 9 figures, revtex 2-column forma
Persistent spins in the linear diffusion approximation of phase ordering and zeros of stationary gaussian processes
The fraction r(t) of spins which have never flipped up to time t is studied
within a linear diffusion approximation to phase ordering. Numerical
simulations show that, even in this simple context, r(t) decays with time like
a power-law with a non-trival exponent which depends on the space
dimension. The local dynamics at a given point is a special case of a
stationary gaussian process of known correlation function and the exponent
is shown to be determined by the asymptotic behavior of the
probability distribution of intervals between consecutive zero-crossings of
this process. An approximate way of computing this distribution is proposed, by
taking the lengths of the intervals between successive zero-crossings as
independent random variables. The approximation gives values of the exponent
in close agreement with the results of simulations.Comment: 10 pages, 2 postscript files. Submitted to PRL. Reference screwup
correcte
New results on the hadronic vacuum polarization to the muon g-2
Results on the lowest-order hadronic vacuum polarization contribution to the
muon magnetic anomaly are presented. They are based on the latest published
experimental data used as input to the dispersion integral. Thus recent results
on tau to nutau pi pi0 decays from Belle and on e+ e- annihilation to pi+ pi-
from BABAR and KLOE are included. The new data, together with improved
isospin-breaking corrections for tau decays, result into a much better
consistency among the different results. A discrepancy between the Standard
Model prediction and the direct g-2 measurement is found at the level of 3
sigma.Comment: proceedings of the PhiPsi09 conference, Oct. 13-16, 2009, Beijing,
Chin
Operational Experience with First Circulating Beam in the LHC
Following a series of injection tests, the first attempts to pass beam around both directions of the LHC were successful and led rapidly to circulating beam in the counter clockwise direction (beam 2) and many turns of beam 1. Unfortunately the beam commissioning was curtailed by the incident in sector 34. However, measurements performed during this first commissioning period showed that the magnet model of the machine had delivered optics close to nominal and also very good performance of beam instrumentation and supporting software. Details of the machine set-up and the commissioning procedures are given. The measurements performed and the key results from this period are described
The LHC Injection Tests
A series of LHC injection tests was performed in August and September 2008. The first saw beam injected into sector 23; the second into sectors 78 and 23; the third into sectors 78-67 and sectors 23-34-45. The fourth, into sectors 23-34-45, was performed the evening before the extended injection test on the 10th September which saw both beams brought around the full circumference of the LHC. The tests enabled the testing and debugging of a number of critical control and hardware systems; testing and validation of instrumentation with beam for the first time; deployment, and validation of a number of measurement procedures. Beam based measurements revealed a number of machine configuration issues that were rapidly resolved. The tests were undoubtedly an essential precursor to the successful start of LHC beam commissioning. This paper provides an outline of preparation for the tests, the machine configuration and summarizes the measurements made and individual system performance
SP-0489: HPV-transformation in the cervix and at non-cervical sites
Pla general d'un dels panells horitzontals sobre espais verds de Barcelona a l'exposició Ciutat. Barcelona projecta a l'Edifici Fòrum. Exposició sobre la planificació urbanística i arquitectònica de Barcelon
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