228 research outputs found
Precision Jet Substructure from Boosted Event Shapes
Jet substructure has emerged as a critical tool for LHC searches, but studies
so far have relied heavily on shower Monte Carlo simulations, which formally
approximate QCD at leading-log level. We demonstrate that systematic
higher-order QCD computations of jet substructure can be carried out by
boosting global event shapes by a large momentum Q, and accounting for effects
due to finite jet size, initial-state radiation (ISR), and the underlying event
(UE) as 1/Q corrections. In particular, we compute the 2-subjettiness
substructure distribution for boosted Z -> q qbar events at the LHC at
next-to-next-to-next-to-leading-log order. The calculation is greatly
simplified by recycling the known results for the thrust distribution in e+ e-
collisions. The 2-subjettiness distribution quickly saturates, becoming Q
independent for Q > 400 GeV. Crucially, the effects of jet contamination from
ISR/UE can be subtracted out analytically at large Q, without knowing their
detailed form. Amusingly, the Q=infinity and Q=0 distributions are related by a
scaling by e, up to next-to-leading-log order.Comment: 5 pages, 7 figure
Jet Physics from Static Charges in AdS
Soft interactions with high-energy jets are explored in radial coordinates
which exploit the approximately conformal behavior of perturbative gauge
theories. In these coordinates, the jets, approximated by Wilson lines, become
static charges in Euclidean AdS. The anomalous dimension of the corresponding
Wilson line operator is then determined by the potential energy of the charges.
To study these Wilson lines we introduce a "conformal gauge" which does not
have kinetic mixing between radial and angular directions, and show that a
number of properties of Wilson lines are reproduced through relatively simple
calculations. For example, certain non-planar graphs involving multiple Wilson
lines automatically vanish. We also discuss the linear growth of the charges'
imaginary potential energy with separation, and a relationship between Wilson
line diagrams and Witten diagrams.Comment: 34 pages, 7 figures; V2: minor edits, added reference
Using integrative taxonomy to distinguish cryptic halfbeak species and interpret distribution patterns, fisheries landings, and speciation
Context. Species classification disputes can be resolved using integrative taxonomy, which
involves the use of both phenotypic and genetic information to determine species boundaries.
Aims. Our aim was to clarify species boundaries of two commercially important cryptic species
of halfbeak (Hemiramphidae), whose distributions overlap in south-eastern Australia, and assist
fisheries management. Methods. We applied an integrative taxonomic approach to clarify
species boundaries and assist fisheries management. Key results. Mitochondrial DNA and
morphological data exhibited significant differences between the two species. The low level of
mitochondrial DNA divergence, coupled with the lack of difference in the nuclear DNA,
suggests that these species diverged relatively recently (c. 500 000 years ago) when compared
with other species within the Hyporhamphus genus (>2.4 million years ago). Genetic differences
between the species were accompanied by differences in modal gill raker counts, mean upper-
jaw and preorbital length, and otolith shape. Conclusions. On the basis of these genetic and
morphological differences, as well as the lack of morphological intergradation between species
along the overlapping boundaries of their geographical distributions, we propose that
Hyporhamphus australis and Hyporhamphus melanochir remain valid species. Implications. This
study has illustrated the need for an integrative taxonomic approach when assessing species
boundaries and has provided a methodological framework for studying other cryptic fish species
in a management context
Liberal market economies, business, and political finance: Britain under New Labour
The extent and nature of business financing of parties is an important feature of political finance. Britainâs transparent and permissive regulatory system provides an excellent opportunity to study business financing of parties. Business donations have been very important to the Conservative party over the last decade, and of only marginal importance to Labour. Unlike other Conservative contributors, business donors are more likely to contribute when the party is popular. In contrast to the previous period of Conservative government, the biggest British businesses tended to abstain from political finance under New Labour. However, their bias towards the Conservatives is affected by the partyâs popularity and the closeness of an election. Britain shares the political importance of business financing of parties and its mixture of ideological and pragmatic motivations with other liberal market economies. However, in Britain the bias towards the right is much stronger and the role of big business more marginal
On Power Suppressed Operators and Gauge Invariance in SCET
The form of collinear gauge invariance for power suppressed operators in the
soft-collinear effective theory is discussed. Using a field redefinition we
show that it is possible to make any power suppressed ultrasoft-collinear
operators invariant under the original leading order gauge transformations. Our
manipulations avoid gauge fixing. The Lagrangians to O(lambda^2) are given in
terms of these new fields. We then give a simple procedure for constructing
power suppressed soft-collinear operators in SCET_II by using an intermediate
theory SCET_I.Comment: 15 pages, journal versio
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Jet physics from static charges in AdS space
Soft interactions with high-energy jets are explored in radial coordinates which exploit the approximately conformal behavior of perturbative gauge theories. In these coordinates, the jets, approximated by Wilson lines, become static charges in Euclidean AdS. The anomalous dimension of the corresponding Wilson line operator is then determined by the potential energy of the charges. To study these Wilson lines we introduce a âconformal gaugeâ which does not have kinetic mixing between radial and angular directions, and show that a number of properties of Wilson lines are reproduced through relatively simple calculations. For example, certain non-planar graphs involving multiple Wilson lines automatically vanish. We also discuss the linear growth of the chargesâ imaginary potential energy with separation, and a relationship between Wilson line diagrams and Witten diagrams.Physic
Recommended from our members
Precision Jet Substructure from Boosted Event Shapes
Jet substructure has emerged as a critical tool for LHC searches, but studies so far have relied heavily on shower Monte Carlo simulations, which formally approximate QCD at leading-log level. We demonstrate that systematic higher-order QCD computations of jet substructure can be carried out by boosting global event shapes by a large momentum Q, and accounting for effects due to finite jet size, initial-state radiation (ISR), and the underlying event (UE) as 1/Q corrections. In particular, we compute the 2-subjettiness substructure distribution for boosted Z â q qÂŻ events at the LHC at next-to-next-to-next-to-leading-log order. The calculation is greatly simplified by recycling the known results for the thrust distribution in e + e â collisions. The 2-subjettiness distribution quickly saturates, becoming Q independent for Q >⌠400 GeV. Crucially, the effects of jet contamination from ISR/UE can be subtracted out analytically at large Q, without knowing their detailed form. Amusingly, the Q = â and Q = 0 distributions are related by a scaling by e, up to next-to-leading-log order.Physic
Multiple AMPK activators inhibit L-Carnitine uptake in C2C12 skeletal muscle myotubes
Mutations in the gene that encodes the principal L-Carnitine transporter, OCTN2, can lead to a reduced intracellular L-Carnitine pool and the disease Primary Carnitine Deficiency. L-Carnitine supplementation is used therapeutically to increase intracellular L-Carnitine. As AMPK and insulin regulate fat metabolism and substrate uptake we hypothesised that AMPK activating compounds and insulin would increase L-Carnitine uptake in C2C12myotubes. The cells express all three OCTN transporters at the mRNA level and immunohistochemistry confirmed expression at the protein level. Contrary to our hypothesis, despite significant activation of PKB and 2DG uptake, insulin did not increase L-Carnitine uptake at 100nM. However, L-Carnitine uptake was modestly increased at a dose of 150nM insulin. A range of AMPK activators that increase intracellular calcium content [caffeine (10mM, 5mM, 1mM, 0.5mM), A23187 (10μM)], inhibit mitochondrial function [Sodium Azide (75μM), Rotenone (1μM), Berberine (100μM), DNP (500μM)] or directly activate AMPK [AICAR (250μM)] were assessed for their ability to regulate L-Carnitine uptake. All compounds tested significantly inhibited L-Carnitine uptake. Inhibition by caffeine was not dantrolene (10μM) sensitive. Saturation curve analysis suggested that caffeine did not competitively inhibit L-Carnitine transport. However, the AMPK inhibitor Compound C (10μM) partially rescued the effect of caffeine suggesting that AMPK may play a role in the inhibitory effects of caffeine. However, caffeine likely inhibits L-Carnitine uptake by alternative mechanisms independently of calcium release. PKA activation or direct interference with transporter function may play a role
Renormalization schemes and the range of two-nucleon effective field theory
The OS and PDS renormalization schemes for the effective field theory with
nucleons and pions are investigated. We explain in detail how the
renormalization is implemented using local counterterms. Fits to the NN
scattering data are performed in the 1S0 and 3S1 channels for different values
of mu_R. An error analysis indicates that the range of the theory with
perturbative pions is consistent with 500 MeV.Comment: 40 pages, typos corrected, journal version. Discussion of the range
in section VII clarified, conclusions unchange
Model independent results for and at order
Exclusive semileptonic B decays into and mesons are
investigated including order corrections using the
heavy quark effective theory. At zero recoil, the
corrections can be written in terms of the leading Isgur-Wise function for
these transitions, , and known meson mass splittings. We obtain an almost
model independent prediction for the shape of the spectrum near zero recoil,
including order corrections. We determine
from the measured branching ratio. Implications for B
decay sum rules are discussed.Comment: 11 pages, revte
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