45 research outputs found
Status of Chiral-Scale Perturbation Theory
Chiral-scale perturbation theory PT has been proposed as an
alternative to chiral perturbation theory which
explains the rule for kaon decays. It is based on a low-energy
expansion about an infrared fixed point in three-flavor QCD. In
PT, quark condensation induces nine Nambu-Goldstone bosons: and a QCD dilaton
which we identify with the resonance. Partial conservation
of the dilatation and chiral currents constrains low-energy constants which
enter the effective Lagrangian of PT. These constraints allow us
to obtain new phenomenological bounds on the dilaton decay constant via the
coupling of to pions, whose value is known precisely from
dispersive analyses of scattering. Improved predictions for and the coupling are also noted. To test
PT for kaon decays, we revive a 1985 proposal for lattice
methods to be applied to on-shell.Comment: 10 pages, 1 figure. Presented at the 8th International Workshop on
Chiral Dynamics, 29 June 2015 - 03 July 2015, Pisa, Italy. Revision:
references and comment adde
Light stops, blind spots, and isospin violation in the MSSM
In the framework of the MSSM, we examine several simplified models where only
a few superpartners are light. This allows us to study WIMP--nucleus scattering
in terms of a handful of MSSM parameters and thereby scrutinize their impact on
dark matter direct-detection experiments. Focusing on spin-independent
WIMP--nucleon scattering, we derive simplified, analytic expressions for the
Wilson coefficients associated with Higgs and squark exchange. We utilize these
results to study the complementarity of constraints due to direct-detection,
flavor, and collider experiments. We also identify parameter configurations
that produce (almost) vanishing cross sections. In the proximity of these
so-called blind spots, we find that the amount of isospin violation may be much
larger than typically expected in the MSSM. This feature is a generic property
of parameter regions where cross sections are suppressed, and highlights the
importance of a careful analysis of the nucleon matrix elements and the
associated hadronic uncertainties. This becomes especially relevant once the
increased sensitivity of future direct-detection experiments corners the MSSM
into these regions of parameter space.Comment: 38 pages, 15 figures. v2: expanded text in Sec. 3 concerning relic
density and (g-2)_mu constraints, clarified text on isospin violation. Fig. 1
is new, minor changes to Figs. 3,4,10. References added, journal versio
Probing lepton flavour (universality) violation at NA62 and future kaon experiments
Recent results from the LHC's first run have revealed intriguing departures
from lepton flavour universality in the semi-leptonic decays of -mesons. We
discuss the complementary role that rare kaon decays can provide in testing new
physics explanations of these flavour anomalies. In the framework of minimal
flavour violation, we relate the chiral low-energy constants involved in
and (\ell = \mu \mbox{ or } e) with the
new physics Wilson coefficients of the effective Hamiltonian. We
comment on the determination of these low-energy constants at NA62 and future
kaon experiments, as well as the required improvements in sensitivity necessary
to test the -physics anomalies in the kaon sector.Comment: 6 pages, Presented at the International Conference on Kaon Physics
2016, 14-17 September 2016, Birmingham, U
Dark Matter: Connecting LHC searches to direct detection
In these proceedings we review the interplay between LHC searches for dark
matter and direct detection experiments. For this purpose we consider two prime
examples: the effective field theory (EFT) approach and the minimal
supersymmetric standard model (MSSM). In the EFT scenario we show that for
operators which do not enter directly direct detection at tree-level, but only
via loop effects, LHC searches give complementary constraints. In the MSSM stop
and Higgs exchange contribute to the direct detection amplitude. Therefore, LHC
searches for supersymmetric particles and heavy Higgses place constraints on
the same parameter space as direct detection.Comment: 5 pages, 3 figures, proceedings for Moriond Gravitation 201
rule for kaon decays derived from QCD infrared fixed point
This article gives details of our proposal to replace ordinary chiral
perturbation theory PT by 3-flavor
chiral-scale perturbation theory PT. In PT,
amplitudes are expanded at low energies and small quark masses about an
infrared fixed point of 3-flavor QCD. At
, the quark condensate induces nine Nambu-Goldstone bosons:
and a QCD dilaton . Physically,
appears as the resonance, a pole at a complex mass with real part
. The rule for nonleptonic -decays is then a
consequence of PT, with a coupling fixed by data for
and . We estimate
for the nonperturbative Drell-Yan ratio at , and
show that, in the many-color limit, becomes a narrow
state with planar-gluon corrections. Rules for the order of terms in
PT loop expansions are derived in Appendix A, and extended in
Appendix B to include inverse-power Li-Pagels singularities due to external
operators. This relates to an observation that, for channels,
partial conservation of the dilatation current is not equivalent to
-pole dominance.Comment: 20 pages, 11 figures. This article is an expanded version of the
letter arXiv:1203.1321 (2012). v4: Fig. 1 moved to second page to match PRD
formatting, minor changes to text and reference
Enhanced Fatty Acid Oxidation and FATP4 Protein Expression after Endurance Exercise Training in Human Skeletal Muscle
FATP1 and FATP4 appear to be important for the cellular uptake and handling of long chain fatty acids (LCFA). These findings were obtained from loss- or gain of function models. However, reports on FATP1 and FATP4 in human skeletal muscle are limited. Aerobic training enhances lipid oxidation; however, it is not known whether this involves up-regulation of FATP1 and FATP4 protein. Therefore, the aim of this project was to investigate FATP1 and FATP4 protein expression in the vastus lateralis muscle from healthy human individuals and to what extent FATP1 and FATP4 protein expression were affected by an increased fuel demand induced by exercise training. Eight young healthy males were recruited to the study. All subjects were non smokers and did not participate in regular physical activity (<1 time per week for the past 6 months, VO2peak 3.4±0.1 l O2 min−1). Subjects underwent an 8 week supervised aerobic training program. Training induced an increase in VO2peak from 3.4±0.1 to 3.9±0.1 l min−1 and citrate synthase activity was increased from 53.7±2.5 to 80.8±3.7 µmol g−1 min−1. The protein content of FATP4 was increased by 33%, whereas FATP1 protein content was reduced by 20%. Interestingly, at the end of the training intervention a significant association (r2 = 0.74) between the observed increase in skeletal muscle FATP4 protein expression and lipid oxidation during a 120 min endurance exercise test was observed. In conclusion, based on the present findings it is suggested that FATP1 and FATP4 proteins perform different functional roles in handling LCFA in skeletal muscle with FATP4 apparently more important as a lipid transport protein directing lipids for lipid oxidation