1,119 research outputs found
Precision predictions for supersymmetric dark matter
The dark matter relic density has been measured by Planck and its
predecessors with an accuracy of about 2%. We present theoretical calculations
with the numerical program DM@NLO in next-to-leading order SUSY QCD and beyond,
which allow to reach this precision for gaugino and squark (co-)annihilations,
and use them to scan the phenomenological MSSM for viable regions, applying
also low-energy, electroweak and hadron collider constraints.Comment: 6 pages, 1 table, 8 figures, proceedings of ICHEP 201
Autonomously acquiring declarative and procedural knowledge for ICAT systems
The construction of Intelligent Computer Aided Training (ICAT) systems is critically dependent on the ability to define and encode knowledge. This knowledge engineering effort can be broadly divided into two categories: domain knowledge and expert or task knowledge. Domain knowledge refers to the physical environment or system with which the expert interacts. Expert knowledge consists of the set of procedures and heuristics employed by the expert in performing their task. Both these areas are a significant bottleneck in the acquisition of knowledge for ICAT systems. This paper presents a research project in the area of autonomous knowledge acquisition using a passive observation concept. The system observes an expert and then generalizes the observations into production rules representing the domain expert's knowledge
Nuclear corrections in neutrino-nucleus DIS and their compatibility with global NPDF analyses
We perform a global chi^2-analysis of nuclear parton distribution functions
using data from charged current neutrino-nucleus deep-inelastic scattering
(DIS), charged-lepton-nucleus DIS, and the Drell-Yan (DY) process. We show that
the nuclear corrections in nu-A DIS are not compatible with the predictions
derived from l^+A DIS and DY data. We quantify this result using a
hypothesis-testing criterion based on the chi^2 distribution which we apply to
the total chi^2 as well as to the chi^2 of the individual data sets. We find
that it is not possible to accommodate the data from nu-A and l^+A DIS by an
acceptable combined fit. Our result has strong implications for the extraction
of both nuclear and proton parton distribution functions using combined
neutrino and charged-lepton data sets.Comment: 5 page
Next generation sequencing analysis reveals a relationship between rDNA unit diversity and locus number in Nicotiana diploids
© 2012 Matyášek et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly cited
Heavy Quark Production in the ACOT Scheme Beyond NLO
We analyze the properties of the ACOT scheme for heavy quark production and
make use of the MS-Bar massless results at NNLO and N3LO for the structure
functions F2 and FL in neutral current deep-inelastic scattering to estimate
the higher order corrections. The dominant heavy quark mass effects at higher
orders can be taken into account using the massless Wilson coefficients
together with an appropriate slow-rescaling prescription implementing the phase
space constraints. Combining the exact ACOT scheme at NLO with these
expressions should provide a good approximation to the full calculation in the
ACOT scheme at NNLO and N3LO.Comment: 4 pages, 2 figures. Presented at DIS12, March 2012, Bonn, German
A Hybrid Scheme for Heavy Flavors: Merging the FFNS and VFNS
We introduce a Hybrid Variable Flavor Number Scheme for heavy flavors,
denoted H-VFNS, which incorporates the advantages of both the traditional
Variable Flavor Number Scheme (VFNS) as well as the Fixed Flavor Number Scheme
(FFNS). By including an explicit -dependence in both the Parton
Distribution Functions (PDFs) and the strong coupling constant , we
generate coexisting sets of PDFs and for at any
scale , that are related analytically by the
matching conditions. The H-VFNS resums the heavy quark contributions and
provides the freedom to choose the optimal for each particular data set.
Thus, we can fit selected HERA data in a FFNS framework, while retaining the
benefits of the VFNS to analyze LHC data at high scales. We illustrate how such
a fit can be implemented for the case of both HERA and LHC data.Comment: 15 pages, 11 figures, updated to match journa
CTEQ nuclear parton distribution functions
We show for the first time preliminary results of nuclear parton distribution
function analysis of charged lepton DIS and Drell-Yan data within the CTEQ
framework including error PDFs. We compare our error estimates to estimates of
different nPDF groups.Comment: 5 pages, to appear in the proceedings of XXI International Workshop
on Deep-Inelastic Scattering and Related Subjects, Marseilles, Franc
Heavy quark & direct photon production and heavy quark parton densities
Direct photon production in association with a heavy quark can serve as an
excellent tool for the study of the heavy quark distributions. Currently it is
believed that heavy quarks are produced radiatively inside the nucleon, and so
there is no need to take into account heavy quark parameters inside global PDF
analyses. Certain models taking into account the possibility of an intrinsic
charm component exist. Here we present how these affect the \gamma + c cross
section. While at pA collisions the potential of this process to constrain the
gluon nuclear PDF which is currently largely unconstrained is presented.Comment: Quarkonium 2010 Proceeding
Update on nCTEQ PDFs: nuclear PDF uncertainties and LHC applications
We present updated nCTEQ nuclear parton distribution functions with errors
including pion production data from RHIC. We compare them with the results of
other groups and present selected LHC applications.Comment: Presented at DIS2014, 28 April - 2 May 2014, Warsaw, Poland.
PoS(DIS2014)04
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