32,604 research outputs found
Quark and Gluon Tagging at the LHC
Being able to distinguish light-quark jets from gluon jets on an
event-by-event basis could significantly enhance the reach for many new physics
searches at the Large Hadron Collider. Through an exhaustive search of existing
and novel jet substructure observables, we find that a multivariate approach
can filter out over 95% of the gluon jets while keeping more than half of the
light-quark jets. Moreover, a combination of two simple variables, the charge
track multiplicity and the -weighted linear radial moment (girth), can
achieve similar results. While this pair appears very promising, our study is
only Monte Carlo based, and other discriminants may work better with real data
in a realistic experimental environment. To that end, we explore many other
observables constructed using different jet sizes and parameters, and highlight
those that deserve further theoretical and experimental scrutiny. Additional
information, including distributions of around 10,000 variables, can be found
on this website http://jets.physics.harvard.edu/qvg .Comment: 5 pages, 3 figures. v2 published versio
Energy conditions for a generally coupled scalar field outside a reflecting sphere
We calculate the stress-energy tensor for a scalar field with general
curvature coupling, outside a perfectly reflecting sphere with Dirichlet
boundary conditions. For conformal coupling we find that the null energy
condition is always obeyed, and therefore the averaged null energy condition
(ANEC) is also obeyed. Since the ANEC is independent of curvature coupling, we
conclude that the ANEC is obeyed for scalar fields with any curvature coupling
in this situation. We also show how the spherical case goes over to that of a
flat plate as one approaches the sphere.Comment: Accepted for publication in Phys. Rev.
Vacuum state of the quantum string without anomalies in any number of dimensions
We show that the anomalies of the Virasoro algebra are due to the asymmetric
behavior of raising and lowering operators with respect to the ground state of
the string. With the adoption of a symmetric vacuum we obtain a non-anomalous
theory in any number of dimensions. In particular for D=4.Comment: 14 pages, LaTex, no figure
Electron Self Energy for Higher Excited S Levels
A nonperturbative numerical evaluation of the one-photon electron self energy
for the 3S and 4S states with charge numbers Z=1 to 5 is described. The
numerical results are in agreement with known terms in the expansion of the
self energy in powers of Zalpha.Comment: 3 pages, RevTeX, to appear in Phys. Rev.
The Induced Magnetic Field of the Moon: Conductivity Profiles and Inferred Temperature
Electromagnetic induction in the moon driven by fluctuations of the interplanetary magnetic field is used to determine the lunar bulk electrical conductivity. The present data clearly show the north-south and east-west transfer function difference as well as high frequency rollover. The difference is shown to be compatible over the mid-frequency range with a noise source associated with the compression of the local remanent field by solar wind dynamic pressure fluctuations. Models for two, three, and four layer; current layer, double current layer, and core plus current layer moons are generated by inversion of the data using a theory which incorporates higher order multipoles. Core radii conductivities generally are in the range 1200 to 1300 km and 0.001 to 0.003 mhos/m; and for the conducting shell 1500 to 1700 km with 0.0001 to 0.0007 mhos/m with an outer layer taken as nonconducting. Core temperature based on available olivine data is 700 to 1000 C
Precision of the calibration of the AXAF engineering test article (VETA) mirrors
Measurements of the VETA encircled energies have been performed at 5 energies within 16 radii ranging from 0.05 to 200 arcseconds. We report here on the analysis of the accuracy of those measurements. A common 'error tree' structure applies, and we present representative numbers for the larger terms. At 0.277, 1.5, and 2.07 keV, and for radii of 3 arcsec and larger, our measurements have estimated 1 sigma errors of 0.6 to 1.5 percent. Effects of measurement statistics and of the VETA test mount limit the accuracy at smaller angles, and modulation by the counter window support structure together with the imperfect position repeatability limit the accuracy for the 0.93 and 2.3 keV energies. We expect to mitigate these limitations when calibrating the complete AXAF flight mirror assembly
Random field Ising systems on a general hierarchical lattice: Rigorous inequalities
Random Ising systems on a general hierarchical lattice with both, random
fields and random bonds, are considered. Rigorous inequalities between
eigenvalues of the Jacobian renormalization matrix at the pure fixed point are
obtained. These inequalities lead to upper bounds on the crossover exponents
.Comment: LaTeX, 13 pages, figs. 1a,1b,2. To be published in PR
Quantum macrostatistical picture of nonequilibrium steady states
We employ a quantum macrostatistical treatment of irreversible processes to
prove that, in nonequilibrium steady states, (a) the hydrodynamical observables
execute a generalised Onsager-Machlup process and (b) the spatial correlations
of these observables are generically of long range. The key assumptions behind
these results are a nonequilibrium version of Onsager's regression hypothesis,
together with certain hypotheses of chaoticity and local equilibrium for
hydrodynamical fluctuations.Comment: TeX, 13 page
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