8 research outputs found
The Strange Parton Distribution of the Nucleon: Global Analysis and Applications
The strangeness degrees of freedom in the parton structure of the nucleon are
explored in the global analysis framework, using the new CTEQ6.5 implementation
of the general mass perturbative QCD formalism of Collins. We systematically
determine the constraining power of available hard scattering experimental data
on the magnitude and shape of the strange quark and anti-quark parton
distributions. We find that current data favor a distinct shape of the strange
sea compared to the isoscalar non-strange sea. A new reference parton
distribution set, CTEQ6.5S0, and representative sets spanning the allowed
ranges of magnitude and shape of the strange distributions, are presented. Some
applications to physical processes of current interest in hadron collider
phenomenology are discussed.Comment: 19 pages; revised version submitted to JHE
Inelastic Black Hole Production and Large Extra Dimensions
Black hole production in elementary particle collisions is among the most
promising probes of large extra spacetime dimensions. Studies of black holes at
particle colliders have assumed that all of the incoming energy is captured in
the resulting black hole. We incorporate the inelasticity inherent in such
processes and determine the prospects for discovering black holes in colliders
and cosmic ray experiments, employing a dynamical model of Hawking evolution.
At the Large Hadron Collider, inelasticity reduces rates by factors of 10^3 to
10^6 in the accessible parameter space, moderating, but not eliminating, hopes
for black hole discovery. At the Pierre Auger Observatory, rates are suppressed
by a factor of 10. We evaluate the impact of cosmic ray observations on
collider prospects.Comment: References adde
The Underlying Event and the Total Cross Section from Tevatron to the LHC
Multiple partonic interactions are widely used to simulate the hadronic final
state in high energy hadronic collisions, and successfully describe many
features of the data. It is important to make maximum use of the available
physical constraints on such models, particularly given the large extrapolation
from current high energy data to LHC energies. In eikonal models, the rate of
multiparton interactions is coupled to the energy dependence of the total cross
section. Using a Monte Carlo implementation of such a model, we study the
connection between the total cross section, the jet cross section, and the
underlying event. By imposing internal consistency on the model, we derive
constraints on its parameters at the LHC. By imposing internal consistency on
the model and comparing to current data we constrain the allowed range of its
parameters. We show that measurements of the total proton-proton cross-section
at the LHC are likely to break this internal consistency, and thus to require
an extension of the model. Likely such extensions are that hard scatters probe
a denser matter distribution inside the proton in impact parameter space than
soft scatters, a conclusion also supported by Tevatron data on double-parton
scattering, and/or that the basic parameters of the model are energy dependent.Comment: 17 pages, 6 figures, version accepted by JHE
Updated Limits on TeV-Scale Gravity from Absence of Neutrino Cosmic Ray Showers Mediated by Black Holes
We revise existing limits on the D-dimensional Planck scale M_D from the
nonobservation of microscopic black holes produced by high energy cosmic
neutrinos in scenarios with D=4+n large extra dimensions. Previous studies have
neglected the energy radiated in gravitational waves by the multipole moments
of the incoming shock waves. We include the effects of energy loss, as well as
form factors for black hole production and recent null results from cosmic ray
detectors. For n>4, we obtain M_D > 1.0 - 1.4 TeV. These bounds are among the
most stringent and conservative to date.Comment: 11 pages, 4 figure
Measurement of the W-boson mass in pp collisions at √s=7 TeV with the ATLAS detector
A measurement of the mass of the W boson is presented based on proton–proton collision data recorded in 2011 at a centre-of-mass energy of 7 TeV with the ATLAS detector at the LHC, and corresponding to 4.6 fb−1 of integrated luminosity. The selected data sample consists of 7.8×106 candidates in the W→μν channel and 5.9×106 candidates in the W→eν channel. The W-boson mass is obtained from template fits to the reconstructed distributions of the charged lepton transverse momentum and of the W boson transverse mass in the electron and muon decay channels, yielding
mW=80370±7 (stat.)±11(exp. syst.)
±14(mod. syst.) MeV
=80370±19MeV,
where the first uncertainty is statistical, the second corresponds to the experimental systematic uncertainty, and the third to the physics-modelling systematic uncertainty. A measurement of the mass difference between the W+ and W−bosons yields mW+−mW−=−29±28 MeV
Diffraction Scattering Of Composite Particles.
PhDNuclear physicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/185279/2/6813381.pd