27,287 research outputs found
The statistical parton distributions: status and prospects
New experimental results on polarized structure functions, cross sections for
neutral and charge current reactions and () charge
current on isoscalar targets are compared with predictions using the
statistical parton distributions, which were previously determined. New data on
cross sections for Drell-Yan processes, single jet in collisions and
inclusive production in collisions are also compared with
predictions from this theoretical approach. The good agreement which we find
with all these tests against experiment, strenghtens our opinion on the
relevance of the role of quantum statistics for parton distributions. We will
also discuss the prospects of this physical framework.Comment: 34 pages, 23 figures, references and figures adde
The strangeness content of the nucleon
We evaluate the matrix element of in hadron states on a lattice.
We find substantial mixing of the connected and disconnected contributions so
that the lattice result that the disconnected contribution to the nucleon is
large does not imply that the content is large. This has
implications for dark matter searches.Comment: contribution to Lattice2001(matrixelement
LHC Coverage of RPV MSSM with Light Stops
We examine the sensitivity of recent LHC searches to signatures of
supersymmetry with R-parity violation (RPV). Motivated by naturalness of the
Higgs potential, which would favor light third-generation squarks, and the
stringent LHC bounds on spectra in which the gluino or first and second
generation squarks are light, we focus on scenarios dominated by the pair
production of light stops. We consider the various possible direct and cascade
decays of the stop that involve the trilinear RPV operators. We find that in
many cases, the existing searches exclude stops in the natural mass range and
beyond. However, typically there is little or no sensitivity to cases dominated
by UDD operators or LQD operators involving taus. We propose several ideas for
searches which could address the existing gaps in experimental coverage of
these signals.Comment: 41 pages, 12 figures; v2: included new searches (see footnote 10),
minor corrections and improvement
Novel Bose-Einstein Interference in the Passage of a Fast Particle in a Dense Medium
When an energetic particle collides coherently with many medium particles at
high energies, the Bose-Einstein symmetry with respect to the interchange of
the exchanged virtual bosons leads to a destructive interference of the Feynman
amplitudes in most regions of the phase space but a constructive interference
in some other regions of the phase space. As a consequence, the recoiling
medium particles have a tendency to come out collectively along the direction
of the incident fast particle, each carrying a substantial fraction of the
incident longitudinal momentum. Such an interference appearing as collective
recoils of scatterers along the incident particle direction may have been
observed in angular correlations of hadrons associated with a high-
trigger in high-energy AuAu collisions at RHIC.Comment: 10 pages, 2 figures, invited talk presented at the 35th Symposium on
Nuclear Physics, Cocoyoc, Mexico, January 3, 2012, to be published in IOP
Conference Serie
Structure functions at large x
Structure function data together with other measurements from fixed-target
deep inelastic scattering and hadron-hadron collider experiments which
contribute to our knowledge of the parton density functions are reviewed. The
inclusive cross-section measurements of neutral and charged current
interactions at HERA are presented and their impact on the parton density
functions is discussed. Future prospects for an improved knowledge of the
parton density functions at large x are briefly mentioned.Comment: Invited talk given at the workshop on ``New Trends in HERA Physics
2001'', Ringberg castle, Germany, June 17-22, 200
Light hadrons in 2+1 flavor lattice QCD
This talk will focus on recent results by the MILC collaboration from
simulations of light hadrons in 2+1 flavor lattice QCD. We have achieved high
precision results in the pseudoscalar sector, including masses and decay
constants, plus quark masses and Gasser-Leutwyler parameters from well
controlled chiral perturbation theory fits to our data. We also show
spectroscopy results for vector mesons and baryons.Comment: To appear in the proceedings of the First Meeting of the APS Topical
Group on Hadronic Physics, Fermilab, Batavia, Illinois, Oct. 24-26, 200
The mass of the charm quark from unquenched lattice QCD at fixed lattice spacing
We determine the mass of the charm quark () from lattice QCD with two
flavors of dynamical quarks with a mass around the strange quark. We compare
this to a determination in quenched QCD which has the same lattice spacing (0.1
fm). We investigate different formulations of the quark mass, based on the
Vector Ward Identity, PCAC relation and the FNAL heavy quark formalism. Based
on these preliminary results we find no effects due to sea quarks with a mass
around strange.Comment: Presented at 21st International Symposium on Lattice Field Theory
(LATTICE 2003), Tsukuba, Japan, 15-19 July, 200
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