332 research outputs found
Quantum Chromodynamics
After a brief historical review of the emergence of QCD as the quantum field
theory of strong interactions, the basic notions of colour and gauge invariance
are introduced leading to the QCD Lagrangian. The second lecture is devoted to
perturbative QCD, from tree-level processes to higher-order corrections in
renormalized perturbation theory, including jet production in e+ e-
annihilation, hadronic tau decays and deep inelastic scattering. The final two
lectures treat various aspects of QCD beyond perturbation theory. The main
theme is effective field theories, from heavy quarks to the light quark sector
where the spontaneously broken chiral symmetry of QCD plays a crucial role.Comment: 48 pages, 28 figures. Lectures given at the 2005 European School of
High-Energy Physics, Kitzbuehel, Austria, Aug. 21 - Sept. 3, 2005; to appear
in the Proceedings (CERN Yellow Report
Mesonic low-energy constants
We review the status of the coupling constants of chiral Lagrangians in the
meson sector, the so-called low-energy constants (LECs). Special emphasis is
put on the chiral and Lagrangians for the strong interactions
of light mesons. The theoretical and experimental input for determining the
corresponding LECs is discussed. In the two-flavour sector, we review the
knowledge of the LECs from both continuum fits and lattice QCD
analyses. For chiral , NNLO effects play a much bigger role. Our main
new results are fits of the LECs both at NLO and NNLO, making extensive
use of the available knowledge of NNLO LECs. We compare our results with
available lattice determinations. Resonance saturation of LECs and the
convergence of chiral to NNLO are discussed. We also review the status
of predictions for the LECs of chiral Lagrangians with dynamical photons and
leptons.Comment: 36 pages, prepared for Annual Review of Nuclear and Particle Science,
typos corrected, reference added, results unchange
The Mesonic Chiral Lagrangian of Order
We construct the effective chiral Lagrangian for chiral perturbation theory
in the mesonic even-intrinsic-parity sector at order . The Lagrangian
contains 112 in principle measurable + 3 contact terms for the general case of
light flavours, 90+4 for three and 53+4 for two flavours. The equivalence
between equations of motion and field redefinitions to remove spurious terms in
the Lagrangians is shown to all orders in the chiral expansion. We also discuss
and implement other methods for reducing the number of terms to a minimal set.Comment: 21 pages, uses longtable.sty, one more contact term found, extensive
renumbering of 3 flavour term
Fingerprint-based in silico models for the prediction of P-glycoprotein substrates and inhibitors
AbstractP-Glycoprotein (P-gp, ABCB1) plays a significant role in determining the ADMET properties of drugs and drug candidates. Substrates of P-gp are not only subject to multidrug resistance (MDR) in tumor therapy, they are also associated with poor pharmacokinetic profiles. In contrast, inhibitors of P-gp have been advocated as modulators of MDR. However, due to the polyspecificity of P-gp, knowledge on the molecular basis of ligand–transporter interaction is still poor, which renders the prediction of whether a compound is a P-gp substrate/non-substrate or an inhibitor/non-inhibitor quite challenging. In the present investigation, we used a set of fingerprints representing the presence/absence of various functional groups for machine learning based classification of a set of 484 substrates/non-substrates and a set of 1935 inhibitors/non-inhibitors. Best models were obtained using a combination of a wrapper subset evaluator (WSE) with random forest (RF), kappa nearest neighbor (kNN) and support vector machine (SVM), showing accuracies >70%. Best P-gp substrate models were further validated with three sets of external P-gp substrate sources, which include Drug Bank (n=134), TP Search (n=90) and a set compiled from literature (n=76). Association rule analysis explores the various structural feature requirements for P-gp substrates and inhibitors
Extracting short-distance physics from K_{L,S} -> pi0 e+ e- decays
We present a new analysis of the rare decay K_L -> pi0 e+ e- taking into
account important experimental progress that has recently been achieved in
measuring K_L -> pi0 gamma gamma and K_S -> pi0 e+ e-. This includes a brief
review of the direct CP-violating component, a calculation of the indirect
CP-violating contribution, which is now possible after the measurement of K_S
-> pi0 e+ e-, and a re-analysis of the CP conserving part. The latter is shown
to be negligible, based on experimental input from K_L -> pi0 gamma gamma, a
more general treatment of the form factor entering the dispersive contribution,
and on a comparison with the CP violating rate, which can now be estimated
reliably. We predict B(K_L -> pi0 e+ e-) = (3.2 +1.2 -0.8) 10^{-11} in the
Standard Model, dominated by CP violation with a sizable contribution (~40%)
from the direct effect, largely through interference with the indirect one.
Methods to deal with the severe backgrounds for K_L -> pi0 e+ e- using
Dalitz-plot analysis and time-dependent K_L-K_S interference are also briefly
discussed.Comment: 24 pages, 6 figures; v2: minor modifications, published versio
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