1,565 research outputs found
Quark mass effects in high energy neutrino nucleon scattering
We evaluate the neutrino nucleon charged current cross section at
next-to-leading order in quantum chromodynamic corrections in the variable
flavor number scheme and the fixed flavor number scheme, taking into account
quark masses. The number scheme dependence is largest at the highest energies
considered here, GeV, where the cross sections differ by
approximately 15 percent. We illustrate the numerical implications of the
inconsistent application of the fixed flavor number scheme.Comment: 8 pages, 8 figures, v2: updated pdfs, version accepted for
publicatio
Target Mass Corrections to Electro-Weak Structure Functions and Perturbative Neutrino Cross Sections
We provide a complete and consistent framework to include subasymptotic
perturbative as well as mass corrections to the leading twist (tau=2)
evaluation of charged and neutral current weak structure functions and the
perturbative neutrino cross sections. We revisit previous calculations in a
modern language and fill in the gaps that we find missing for a complete and
ready-to-use "NLO xi-scaling" formulary. In particular, as a new result we
formulate the mixing of the partonic and hadronic structure function tensor
basis in the operator approach to deep inelastic scattering. As an underlying
framework we follow the operator product expansion a la Georgi & Politzer that
allows the inclusion of target mass corrections at arbitrary order in QCD and
we provide explicit analytical and numerical results at NLO. We compare this
approach with a simpler collinear parton model approach to xi-scaling. Along
with target mass corrections we include heavy quark mass effects as a
calculable leading twist power suppressed correction. The complete corrections
have been implemented into a Monte Carlo integration program to evaluate
structure functions and/or integrated cross sections. As applications, we
compare the operator approach with the collinear approximation numerically and
we investigate the NLO and mass corrections to observables that are related to
the extraction of the weak mixing angle from a Paschos-Wolfenstein-like
relation in neutrino-iron scattering. We expect that the interpretation of
neutrino scattering events in terms of oscillation physics and electroweak
precision physics will benefit from our results.Comment: 26 pages, 5 figures, note added, to appear in PR
Nonparametric Stochastic Volatility
Using recent advances in the nonparametric estimation of continuous-time processes under mild statistical assumptions as well as recent developments on nonparametric volatility estimation by virtue of market microstructure noise-contaminated high-frequency asset price data, we provide (i) a theory of spot variance estimation and (ii) functional methods for stochastic volatility modelling. Our methods allow for the joint evaluation of return and volatility dynamics with nonlinear drift and diffusion functions, nonlinear leverage effects, jumps in returns and volatility with possibly state-dependent jump intensities, as well as nonlinear risk-return trade-offs. Our identification approach and asymptotic results apply under weak recurrence assumptions and, hence, accommodate the persistence properties of variance in finite samples. Functional estimation of a generalized (i.e., nonlinear) version of the square-root stochastic variance model with jumps in both volatility and returns for the S&P500 index suggests the need for richer variance dynamics than in existing work. We find a linear specification for the variance's diffusive variance to be misspecified (and inferior to a more flexible CEV specification) even when allowing for jumps in the variance dynamics.Spot variance, stochastic volatility, jumps in returns, jumps in volatility, leverage effects, risk-return trade-offs, kernel methods, recurrence, market microstructure noise.
Ultrahigh energy neutrinos, small x and unitarity
The ultrahigh energy cross section for neutrino interactions with nucleons is
reviewed, and unitarity constraints are discussed. We argue that existing QCD
extrapolations are self-consistent, and do not imply a breakdown of the
perturbative expansion in the weak coupling.Comment: 5 pages, 2 figures, RevTeX4, contribution to Snowmass 200
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