919 research outputs found
Nonabelian Gauge Symmetry in the Causal Epstein-Glaser Approach
We present some generalizations of a recently proposed alternative approach
to nonabelian gauge theories based on the causal Epstein-Glaser method in
perturbative quantum field theory. Nonabelian gauge invariance is defined by a
simple commutator relation in every order of perturbation theory separately
using only the linear (abelian) BRS-transformations of the asymptotic fields.
This condition is sufficient for the unitarity of the S-matrix in the physical
subspace. We derive the most general specific coupling compatible with the
conditions of nonabelian gauge invariance and normalizability. We explicitly
show that the quadrilinear terms, the four-gluon-coupling and the
four-ghost-coupling, are generated by our linear condition of nonabelian gauge
invariance. Moreover, we work out the required generalizations for linear
gauges.Comment: 32 pages, latex-file, no figure
Comments on the Gauge Fixed BRST Cohomology and the Quantum Noether Method
We discuss in detail the relation between the gauge fixed and gauge invariant
BRST cohomology. We showed previously that in certain gauges some cohomology
classes of the gauge-fixed BRST differential do not correspond to gauge
invariant observables. We now show that in addition ``accidental'' conserved
currents may appear. These correspond one-to-one to observables that become
trivial in this gauge. We explicitly show how the gauge-fixed BRST cohomology
appears in the context of the Quantum Noether Method.Comment: 24 pages, example section improved, short version without background
material will appear in Physics Letters
Inclusive Rare B Decays
We review the present status of rare B decays, focusing on inclusive decay
modes and their role in our search for new physics. We also briefly discuss
direct CP violation in rare B decays and the rare kaon decays and , which offer complementary
opportunities for precision flavour physics.Comment: 46 pages, latex, 17 figures, references adde
New Physics Search in Flavour Physics
With the running B, kaon and neutrino physics experiments, flavour physics
takes centre stage within today's particle physics. We discuss the
opportunities offered by these experiments in our search for new physics beyond
the SM and discuss their complementarity to collider physics.
We focus on rare B and kaon decays, highlighting specific observables in an
exemplary mode. We also comment on the so-called B --> pi pi and B --> K pi
puzzles. Moreover, we briefly discuss the restrictive role of long-distance
strong interactions and some new tools such as QCD factorization and SCET to
handle them.Comment: 13 pages, 9 figure
Direct CP Violation In Radiative B Decays
We discuss the role of the radiative B decays in our
search for new physics focusing on the issue of direct CP violation. We discuss
in some detail a SM prediction for the CP asymmetries in inclusive
transitions, namely . Any measured value in significant
deviation of this estimate would indicate new sources of CP violation beyond
the CKM phase.Comment: latex, 8 pages, 3 figure
Flavour data constraints on new physics and SuperIso
We discuss the implications of B_s -> mu+mu- and B -> K*mu+mu- decays in the
context of indirect searches for new physics, emphasising the new LHCb results.
In particular, we derive the consequences of the MFV hypothesis and discuss the
importance of the MFV predictions. The impact of the recent LHCb measurements
in the context of the MSSM will also be addressed, and the SuperIso program
will be briefly described.Comment: 7 pages, 4 figures, contribution to the ICHEP 2012 Conference
proceedings, 4-11 July 2012, Melbourne, Australi
Status of SM calculations of b > s transitions
We report recent progress in SM calculations of transitions. We
discuss the first NNLL prediction of the branching
ratio, including important additional subtleties due to non-perturbative
corrections and logarithmically-enhanced cut effects, and also recent results
on the inclusive mode . Moreover, new results on
the corresponding exclusive modes are reviewed. Finally, we comment on the
present status of the so-called puzzle in hadronic
transitionsComment: 10 pages, 6 figures, minor changes, published versio
Interplay of Direct and Indirect Searches for New Physics
We report recent work on the interplay of collider and flavour physics
regarding the search for physics beyond the Standard Model.Comment: 4 pages, based on an invited talk at PANIC11, MIT, Cambridge, USA,
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