59 research outputs found
Quark Asymmetries in Nucleons
We have developed a physical model for the non-perturbative x-shape of parton
density functions in the proton, based on Gaussian fluctuations in momenta, and
quantum fluctuations of the proton into meson-baryon pairs. The model describes
the proton structure function and gives a natural explanation of observed quark
asymmetries, such as the difference between the anti-up and anti-down sea quark
distributions and between the up and down valence distributions. We also find
an asymmetry in the momentum distribution of strange and anti-strange quarks in
the nucleon, large enough to reduce the NuTeV anomaly to a level which does not
give a significant indication of physics beyond the standard model.Comment: 4 pages, 5 figures. Talk given at DIS 2005, Madison, USA, April
27-May 1, 200
Simplified Models for a First Characterization of New Physics at the LHC
Low-energy SUSY and several other theories that address the hierarchy problem
predict pair-production at the LHC of particles with Standard Model quantum
numbers that decay to jets, missing energy, and possibly leptons. If an excess
of such events is seen in LHC data, a theoretical framework in which to
describe it will be essential to constraining the structure of the new physics.
We propose a basis of four deliberately simplified models, each specified by
only 2-3 masses and 4-5 branching ratios, for use in a first characterization
of data. Fits of these simplified models to the data furnish a quantitative
presentation of the jet structure, electroweak decays, and heavy-flavor content
of the data, independent of detector effects. These fits, together with plots
comparing their predictions to distributions in data, can be used as targets
for describing the data within any full theoretical model.Comment: 76 pages, 24 figures, 9 table
Measuring Sparticles with the Matrix Element
We apply the Matrix Element Method (MEM) to mass determination of squark pair
production with direct decay to quarks and LSP at the LHC, showing that
simultaneous mass determination of squarks and LSP is possible. We furthermore
propose methods for inclusion of QCD radiation effects in the MEM.Comment: 4 pages, 2 figures. To appear in the proceedings of SUSY09, the 17th
International Conference on Supersymmetry and the Unification of Fundamental
Interactions. Figures replaced (corrected y axis labels
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