418 research outputs found
CTEQ-TEA parton distribution functions and HERA Run I and II combined data
We analyze the impact of the recent HERA run I+II combination of inclusive
deep inelastic scattering cross-section data on the CT14 global analysis of
PDFs. New PDFs at NLO and NNLO, called CT14, are obtained by
a refit of the CT14 data ensembles, in which the HERA run I combined
measurements are replaced by the new HERA run I+II combination. The CT14
functional parametrization of PDFs is flexible enough to allow good
descriptions of different flavor combinations, so we use the same
parametrization for CT14 but with an additional shape
parameter for describing the strange quark PDF. We find that the HERA I+II data
can be fit reasonably well, and both CT14 and CT14 PDFs can
describe equally well the non-HERA data included in our global analysis.
Because the CT14 and CT14 PDFs agree well within the PDF
errors, we continue to recommend CT14 PDFs for the analysis of LHC Run 2
experiments.Comment: 19 pages, 6 figures and 3 table
A Field Range Bound for General Single-Field Inflation
We explore the consequences of a detection of primordial tensor fluctuations
for general single-field models of inflation. Using the effective theory of
inflation, we propose a generalization of the Lyth bound. Our bound applies to
all single-field models with two-derivative kinetic terms for the scalar
fluctuations and is always stronger than the corresponding bound for slow-roll
models. This shows that non-trivial dynamics can't evade the Lyth bound. We
also present a weaker, but completely universal bound that holds whenever the
Null Energy Condition (NEC) is satisfied at horizon crossing.Comment: 16 page
Molecular systematics of the digenean community parasitising the cerithiid gastropod Clypeomorus batillariaeformis Habe & Kusage on the Great Barrier Reef
A rich fauna of digenetic trematodes has been documented from the Great Barrier Reef (GBR), yet little is known of the complex life-cycles of these parasites which occur in this diverse marine ecosystem. At Heron Island, a small coral cay at the southern end of the GBR, the intertidal marine gastropod Clypeomorus batillariaeformis Habe & Kusage (Cerithiidae) is especially abundant. This gastropod serves as an intermediate host for 12 trematode species utilising both fish and avian definitive hosts. However, 11 of these species have been characterised solely with morphological data. Between 2015 and 2018 we collected 4870C. batillariaeformis from Heron Island to recollect these species with the goal of using molecular data to resolve their phylogenetic placement. We found eight of the 12 previously known species and two new forms, bringing the total number of digenean species known to parasitise C. batillariaeformis to 14. The families of this trematode community now include the Atractotrematidae Yamaguti, 1939, Bivesiculidae Yamaguti, 1934, Cyathocotylidae MĂĽhling, 1898, Hemiuridae Looss, 1899, Heterophyidae Leiper, 1909, Himasthlidae Odhner, 1910, Microphallidae Ward, 1901, and Renicolidae Dollfus, 1939. Molecular data (ITS and 28S rDNA) were generated for all trematode species, and the phylogenetic position of each species was determined. The digenean community parasitising C. batillariaeformis includes several common species, as well as multiple species which are uncommon to rare. Although most of those trematodes in the community which exploit fishes as definitive hosts have remained common, the composition of those which utilise birds appears to have shifted over time
Implications of CTEQ global analysis for collider observables
The latest CTEQ6.6 parton distributions, obtained by global analysis of hard
scattering data in the framework of general-mass perturbative QCD, are employed
to study theoretical predictions and their uncertainties for significant
processes at the Fermilab Tevatron and CERN Large Hadron Collider. The
previously observed increase in predicted cross sections for the
standard-candle W and Z boson production processes in the general-mass scheme
(compared to those in the zero-mass scheme) is further investigated and
quantified. A novel method to constrain PDF uncertainties in LHC observables,
by effectively exploiting PDF-induced correlations with benchmark standard
model cross sections, is presented. Using this method, we show that the
top-antitop pair cross section can potentially serve as a standard candle
observable for the LHC processes dominated by initial-state gluon scattering.
Among other benefits, precise measurements of cross sections would
reduce PDF uncertainties in predictions for single-top quark and Higgs boson
production in the standard model and minimal supersymmetric standard model.Comment: 32 pages, 15 figures; figures with embedded fonts available at
http://hep.pa.msu.edu/cteq/public/6.6/pdfs/; extended discussion of small-x
strangeness, added references, minor changes in Figs. 2-4 in the revised
versio
Parton Distributions for Event Generators
In this paper, conventional Global QCD analysis is generalized to produce
parton distributions optimized for use with event generators at the LHC. This
optimization is accomplished by combining the constraints due to existing
hard-scattering experimental data with those from anticipated cross sections
for key representative SM processes at LHC (by the best available theory) as
joint input to the global analyses. The PDFs obtained in these new type of
global analyses using matrix elements calculated in any given order will be
best suited to work with event generators of that order, for predictions at the
LHC. This is most useful for LO event generators at present. Results obtained
from a few candidate PDF sets (labeled as CT09MCS, CT09MC1 and CT09MC2) for LO
event generators produced in this way are compared with those from other
approaches.Comment: 35 pages, 19 figures, and 4 table
Hidden in the fog: morphological and molecular characterisation of Derogenes varicus sensu stricto (Trematoda, Derogenidae) from Sweden and Norway, and redescription of two poorly known Derogenes species
Derogenes varicus (Müller, 1784) is widely reported as a trematode with exceptionally low host specificity and a wide, bipolar distribution. However, several recent studies have suggested that D. varicus represents a species complex and based on molecular evidence, four genetic lineages (labeled as “DV1–4”) have been designated within the D. varicus species complex. This possibility requires improved (ideally molecular) characterisation of specimens from the type-host (Salmo salar) and type-locality (off Denmark). During examination of trematode parasites of fish from Scandinavian and Arctic waters (Sweden and Norway), we found specimens of D. varicus in the stomach of Merlangius merlangus off the coast of Sweden, and in Gadus morhua off the coast of Sweden and Norway; we compared them to D. varicus from the type-host, the Atlantic salmon Salmo salar from Norway, to verify their conspecificity. Newly generated sequences (28S rDNA, ITS2 and cox1) of Scandinavian and Arctic specimens consistent with D. varicus all formed a single clade, DV1. 28S sequences of D. varicus from S. salar from Norway, i.e., close to the Danish type locality, clustered within the DV1 clade along with sequences of D. varicus from various hosts including Limanda limanda, G. morhua and Myoxocephalus scorpius from the White Sea and the Barents Sea (Russia), without any host-related structuring. We thus consider that the lineage DV1 represents D. varicus sensu stricto. Additionally, specimens from M. merlangus had a similar morphology and anatomy to those of D. varicus from L. limanda, G. morhua and M. scorpius from T. Odhner’s collection, supporting the presence of a single species in the DV1 lineage designated herein as D. varicus sensu stricto. We redescribe D. varicus sensu stricto, add new morphological characters and provide morphometric data. We infer that D. varicus types DV2–4 all relate to separate species. We also revise type-specimens of Derogenes minor Looss, 1901 from the A. Looss collection in the Swedish Museum of Natural History and provide redescriptions of it and of the type-species of the genus, Derogenes ruber Lühe, 1900. In light of their morphological distinctiveness relative to D. varicus sensu stricto, we reinstate D. parvus Szidat, 1950 and D. fuhrmanni Mola, 1912
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