628 research outputs found
Heavy-quark energy loss in pQCD and SYM plasmas
We consider heavy-quark energy loss and pT-broadening in a strongly-coupled
N=4 Super Yang Mills (SYM) plasma, and the problem of finite-extend matter is
addressed. When expressed in terms of the appropriate saturation momentum, one
finds identical parametric forms for the energy loss in pQCD and SYM theory,
while pT-broadening is radiation dominated in SYM theory and multiple
scattering dominated in pQCD.Comment: 5 pages, 2 figures, Proceedings of the IIIrd Workshop for Young
Scientists on the Physics of Ultrarelativistic Nucleus-Nucleus Collisions
(HotQuarks08), Estes Park, USA, August 18-23 200
Electromagnetic proton form factors in large QCD
The electromagnetic form factors of the proton are obtained using a
particular realization of QCD in the large limit (),
which sums up the infinite number of zero-width resonances to yield an Euler's
Beta function (Dual-). The form factors and
, as well as agree very well with reanalyzed space-like
data in the whole range of momentum transfer. In addition, the predicted ratio
is in good agreement with recent polarization transfer
measurements at Jefferson Lab.Comment: 10 page
E-Flow: A communication system for user notification in dynamic evacuation scenarios
Most of the current evacuation plans are based on static signaling, fixed monitoring infrastructure, and limited user notification and feedback mechanisms. These facts lead to lower situation awareness, in the case event of an emergency, such as blocked emergency exits, while delaying the reaction time of individuals. In this context, we introduce the E-Flow communication system, which improves the user awareness by integrating personal, mobile and fixed devices with the existing monitoring infrastructure. Our system broadens the notification and monitoring alternatives, in real time, among, safety staff, end-users and evacuation related devices, such as sensors and actuators
Mathematical modeling and forecasting of COVID-19: experience in Santiago de Cuba province
In the province of Santiago de Cuba, Cuba, the COVID-19 epidemic has a limited progression that shows an early small-number peak of infections. Most published mathematical models fit data with high numbers of confirmed cases. In contrast, small numbers of cases make it difficult to predict the course of the epidemic. We present two known models adapted to capture the noisy dynamics of COVID-19 in the Santiago de Cuba province. Parameters of both models were estimated using the approximate-Bayesian-computation framework with dedicated error laws. One parameter of each model was updated on key dates of travel restrictions. Both models approximately predicted the infection peak and the end of the COVID-19 epidemic in Santiago de Cuba. The first model predicted 57 reported cases and 16 unreported cases. Additionally, it estimated six initially exposed persons. The second model forecasted 51 confirmed cases at the end of the epidemic. In conclusion, an opportune epidemiological investigation, along with the low number of initially exposed individuals, might partly explain the favorable evolution of the COVID-19 epidemic in Santiago de Cuba. With the available data, the simplest model predicted the epidemic evolution with greater precision, and the more complex model helped to explain the epidemic phenomenology
The dynamics of quark-gluon plasma and AdS/CFT
In these pedagogical lectures, we present the techniques of the AdS/CFT
correspondence which can be applied to the study of real time dynamics of a
strongly coupled plasma system. These methods are based on solving
gravitational Einstein's equations on the string/gravity side of the AdS/CFT
correspondence. We illustrate these techniques with applications to the
boost-invariant expansion of a plasma system. We emphasize the common
underlying AdS/CFT description both in the large proper time regime where
hydrodynamic dynamics dominates, and in the small proper time regime where the
dynamics is far from equilibrium. These AdS/CFT methods provide a fascinating
arena interrelating General Relativity phenomenae with strongly coupled gauge
theory physics.Comment: 35 pages, 3 figures. Lectures at the 5th Aegean summer school, `From
gravity to thermal gauge theories: the AdS/CFT correspondence'. To appear in
the proceedings in `Lecture Notes in Physics
Hadrons with Charm and Beauty
By combining potential models and QCD spectral sum rules (QSSR), we discuss
the spectroscopy of the mesons and of the , and
baryons ( or ), the decay constant and the
(semi)leptonic decay modes of the meson. For the masses, the best
predictions come from potential models and read: ~MeV,
~MeV, ~GeV,
~GeV, ~GeV
and ~GeV. The decay constant is well determined from QSSR and leads to:
s.The uses of the vertex sum rules for the semileptonic decays of the
show that the -dependence of the form factors is much stronger than
predicted by vector meson dominance. It also predicts the almost equal strength
of about 0.30 sec for the semileptonic rates into
and J/. Besides these phenomenological results, we
also show explicitly how the Wilson coefficients of the and gluon condensates already contain the full
heavy quark- () and mixed- ()
condensate contributions in the OPE.}Comment: 32 pages, LaTeX, no changes in the 1994 paper, latex errors corrected
in 201
Electromagnetic Probes
A review is presented of dilepton and real photon measurements in
relativistic heavy ion collisions over a very broad energy range from the low
energies of the BEVALAC up to the highest energies available at RHIC. The
dileptons cover the invariant mass range \mll = 0 - 2.5 GeV/c, i.e. the
continuum at low and intermediate masses and the light vector mesons, . The review includes also measurements of the light vector mesons
in elementary reactions.Comment: To be published in Landolt-Boernstein Volume 1-23A; 40 pages, 24
figures. Final version updated with small changes to the text, updated
references and updated figure
Hadronic production of S- and P-wave states of (b-bar c)-quarkonium
In the leading order of the perturbative QCD, the hadronic
production cross-sections of - and -wave states of meson are
calculated. The results for the -wave levels are compared with the values
given in other papers as well as in the model of the quark fragmenatation
into . In the given order, the cross-sections of the hadronic production
of the -wave states are calculated for the first time. Their contribution
into the meson production is less than 10\%. There is a strong difference
between the predictions of the fragmentation model and the exact perturbative
calculations. These difeerences are discussed in details for the differential
distributions over various kinematical quantities.Comment: 12 pages, LATEX file, ps-figures. uuencoded compresed tar-fil
Measurement of Bose-Einstein Correlations in e+e- -> W+W- at root(s)=189GeV
We investigate Bose-Einstein correlations (BEC) in W-pair production at
root(s)=189GeV using the L3 detector at LEP. We observe BEC between particles
from a single W decay in good agreement with those from a light-quark Z decay
sample. We investigate their possible existence between particles coming from
different W's. No evidence for such inter-W BEC is found
Measurement of the W+W-gamma Cross Section and Direct Limits on Anomalous Quartic Gauge Boson Couplings at LEP
The process e+e- -> W+W-gamma is analysed using the data collected with the
L3 detector at LEP at a centre-of-mass energy of 188.6GeV, corresponding to an
integrated luminosity of 176.8pb^-1. Based on a sample of 42 selected W+W-
candidates containing an isolated hard photon, the W+W-gamma cross section,
defined within phase-space cuts, is measured to be: sigma_WWgamma = 290 +/- 80
+/- 16 fb, consistent with the Standard Model expectation. Including the
process e+e- -> nu nu gamma gamma, limits are derived on anomalous
contributions to the Standard Model quartic vertices W+W- gamma gamma and W+W-Z
gamma at 95% CL: -0.043 GeV^-2 < a_0/Lambda^2 < 0.043 GeV^-2 0.08 GeV^-2 <
a_c/Lambda^2 < 0.13 GeV^-2 0.41 GeV^-2 < a_n/Lambda^2 < 0.37 GeV^-2
- âŠ