67 research outputs found
Improving the kinetic couplings in lattice nonrelativistic QCD
We improve the non-relativistic QCD (NRQCD) action by comparing the
dispersion relation to that of the continuum through in
perturbation theory. The one-loop matching coefficients of the
kinetic operators are determined, as well as the scale at
which to evaluate in the -scheme for each quantity. We utilise
automated lattice perturbation theory using twisted boundary conditions as an
infrared regulator. The one-loop radiative corrections to the mass
renormalisation, zero-point energy and overall energy-shift of an NRQCD
-quark are also found. We also explore how a Fat-smeared NRQCD action and
changes of the stability parameter affect the coefficients. Finally, we use
gluon field ensembles at multiple lattice spacing values, all of which include
, , and quark vacuum polarisation, to test how the improvements
affect the non-perturbatively determined and
kinetic masses, and the tuning of the quark mass
HQET at order : II. Spectroscopy in the quenched approximation
Using Heavy Quark Effective Theory with non-perturbatively determined
parameters in a quenched lattice calculation, we evaluate the splittings
between the ground state and the first two radially excited states of the
system at static order. We also determine the splitting between first excited
and ground state, and between the and ground states to order
. The Generalized Eigenvalue Problem and the use of all-to-all
propagators are important ingredients of our approach.Comment: (1+18) pages, 3 figures (4 pdf files); pdflatex; v2: corrections to
table 1, results unaffecte
A Profile Likelihood Analysis of the Constrained MSSM with Genetic Algorithms
The Constrained Minimal Supersymmetric Standard Model (CMSSM) is one of the
simplest and most widely-studied supersymmetric extensions to the standard
model of particle physics. Nevertheless, current data do not sufficiently
constrain the model parameters in a way completely independent of priors,
statistical measures and scanning techniques. We present a new technique for
scanning supersymmetric parameter spaces, optimised for frequentist profile
likelihood analyses and based on Genetic Algorithms. We apply this technique to
the CMSSM, taking into account existing collider and cosmological data in our
global fit. We compare our method to the MultiNest algorithm, an efficient
Bayesian technique, paying particular attention to the best-fit points and
implications for particle masses at the LHC and dark matter searches. Our
global best-fit point lies in the focus point region. We find many
high-likelihood points in both the stau co-annihilation and focus point
regions, including a previously neglected section of the co-annihilation region
at large m_0. We show that there are many high-likelihood points in the CMSSM
parameter space commonly missed by existing scanning techniques, especially at
high masses. This has a significant influence on the derived confidence regions
for parameters and observables, and can dramatically change the entire
statistical inference of such scans.Comment: 47 pages, 8 figures; Fig. 8, Table 7 and more discussions added to
Sec. 3.4.2 in response to referee's comments; accepted for publication in
JHE
The hadronic vacuum polarization contribution to the muon g − 2 from lattice QCD
We present a calculation of the hadronic vacuum polarization contribution to
the muon anomalous magnetic moment, , in lattice QCD
employing dynamical up and down quarks. We focus on controlling the infrared
regime of the vacuum polarization function. To this end we employ several
complementary approaches, including Pad\'e fits, time moments and the
time-momentum representation. We correct our results for finite-volume effects
by combining the Gounaris-Sakurai parameterization of the timelike pion form
factor with the L\"uscher formalism. On a subset of our ensembles we have
derived an upper bound on the magnitude of quark-disconnected diagrams and
found that they decrease the estimate for by at most 2%.
Our final result is , where the first error is statistical, and the second denotes the
combined systematic uncertainty. Based on our findings we discuss the prospects
for determining with sub-percent precision.Comment: 42 pages, 7 figures, version published in JHE
Overconfidence in Labor Markets
This chapter reviews how worker overconfidence affects labor markets. Evidence from psychology and economics shows that in many situations, most people tend to overestimate their absolute skills, overplace themselves relative to others, and overestimate the precision of their knowledge. The chapter starts by reviewing evidence for overconfidence and for how
overconfidence affects economic choices. Next, it reviews economic explanations for overconfidence. After that, it discusses research on the impact of worker overconfidence on labor markets where wages are determined by bargaining between workers and firms. Here, three key questions are addressed. First, how does worker overconfidence affect effort provision
for a fixed compensation scheme? Second, how should firms design compensation schemes when workers are overconfident? In particular, will a compensation scheme offered to an overconfident worker have higher-or lower-powered incentives than that offered to a worker with accurate self-perception? Third, can worker overconfidence lead to a Pareto improvement? The chapter continues by reviewing research on the impact of worker overconfidence on labor markets where workers can move between firms and where neither firms nor workers have discretion over wage setting. The chapter concludes with a summary of its main findings and a discussion of avenues for future research
Population Genomics of Parallel Adaptation in Threespine Stickleback using Sequenced RAD Tags
Next-generation sequencing technology provides novel opportunities for gathering genome-scale sequence data in natural populations, laying the empirical foundation for the evolving field of population genomics. Here we conducted a genome scan of nucleotide diversity and differentiation in natural populations of threespine stickleback (Gasterosteus aculeatus). We used Illumina-sequenced RAD tags to identify and type over 45,000 single nucleotide polymorphisms (SNPs) in each of 100 individuals from two oceanic and three freshwater populations. Overall estimates of genetic diversity and differentiation among populations confirm the biogeographic hypothesis that large panmictic oceanic populations have repeatedly given rise to phenotypically divergent freshwater populations. Genomic regions exhibiting signatures of both balancing and divergent selection were remarkably consistent across multiple, independently derived populations, indicating that replicate parallel phenotypic evolution in stickleback may be occurring through extensive, parallel genetic evolution at a genome-wide scale. Some of these genomic regions co-localize with previously identified QTL for stickleback phenotypic variation identified using laboratory mapping crosses. In addition, we have identified several novel regions showing parallel differentiation across independent populations. Annotation of these regions revealed numerous genes that are candidates for stickleback phenotypic evolution and will form the basis of future genetic analyses in this and other organisms. This study represents the first high-density SNP–based genome scan of genetic diversity and differentiation for populations of threespine stickleback in the wild. These data illustrate the complementary nature of laboratory crosses and population genomic scans by confirming the adaptive significance of previously identified genomic regions, elucidating the particular evolutionary and demographic history of such regions in natural populations, and identifying new genomic regions and candidate genes of evolutionary significance
QCD and strongly coupled gauge theories : challenges and perspectives
We highlight the progress, current status, and open challenges of QCD-driven physics, in theory and in experiment. We discuss how the strong interaction is intimately connected to a broad sweep of physical problems, in settings ranging from astrophysics and cosmology to strongly coupled, complex systems in particle and condensed-matter physics, as well as to searches for physics beyond the Standard Model. We also discuss how success in describing the strong interaction impacts other fields, and, in turn, how such subjects can impact studies of the strong interaction. In the course of the work we offer a perspective on the many research streams which flow into and out of QCD, as well as a vision for future developments.Peer reviewe
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Improving the kinetic couplings in lattice nonrelativistic QCD
We improve the non-relativistic QCD (NRQCD) action by comparing the dispersion relation to that of the continuum through in perturbation theory. The one-loop matching coefficients of the kinetic operators are determined, as well as the scale at which to evaluate in the -scheme for each quantity. We utilise automated lattice perturbation theory using twisted boundary conditions as an infrared regulator. The one-loop radiative corrections to the mass renormalisation, zero-point energy and overall energy-shift of an NRQCD -quark are also found. We also explore how a Fat-smeared NRQCD action and changes of the stability parameter affect the coefficients. Finally, we use gluon field ensembles at multiple lattice spacing values, all of which include , , and quark vacuum polarisation, to test how the improvements affect the non-perturbatively determined and kinetic masses, and the tuning of the quark mass
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