300 research outputs found

### Chiral Meson Physics at Two Loops

An overview of Chiral Perturbation Theory calculations in the mesonic sector
at the two Loop level is given. Discussed in some detail are the partially
quenched case relevant for lattice QCD, the general fitting procedures and
$\pi\pi$,$\pi K$ scattering as well as the determination of $V_{us}$ and
$K_{\ell3}$ decays.Comment: 7 pages, Invited plenary talk presented at the 19th European Few-Body
conference, Groningen, The Netherlands, August 23-27, 200

### Chiral Dynamics in the Meson Sector at two Loops

I give a very short introduction to Chiral Perturbation Theory and an
overview of the next-to-next-to-leading order three-flavour calculations done.
I discuss those relevant for an improvement in the accuracy of the measurement
of $V_{us}$ in more detail. One major conclusion is that all needed $p^6$ low
energy constants can be obtained from experiment via the scalar form-factor in
$K_{\ell3}$ decays.Comment: 5 pages, Talk presented at CIPANP 2003, Conference on the
Intersections of Particle and Nuclear Physics, New York May 19-24, 200

### ChPT loops for the lattice: pion mass and decay constant, HVP at finite volume and $n\bar n$-oscillations

I present higher loop order results for several calculations in Chiral
perturbation Theory. 1) Two-loop results at finite volume for hadronic vacuum
polarization. 2) A three-loop calculation of the pion mass and decay constant
in two-flavour ChPT. For the pion mass all needed auxiliary parameters can be
determined from lattice calculations of $\pi\pi$-scattering. 3) Chiral
corrections to neutron-anti-neutron oscillations.Comment: 8 pages, presented at Lattice 2017, the 35th International Symposium
on Lattice Field Theory, Granada, Spain, 18-24 June 201

### Quark Mass dependence at Two Loops for Meson Properties

This talks contains a short introduction to Chiral Perturbation Theory and
the existing calculations to two-loop order in the mesonic sector. I include a
discussion on which quantities the expansion can be organized in. The present
best values of the Low-Energy-Constants as determined from continuum physics
are given as well as the assumptions underlying the fits to experimental data.
I present plots of masses, decay constants and $f_+(0)$ in $K_{\ell3}$ as a
function of quark or meson masses. The talk ends with a list of things for
which it would be extremely useful to have good results from lattice QCD
calculations.Comment: 15 pages, plenary talk at T he XXV International Symposium on Lattice
Field Theory, July 30 - August 4 2007, Regensburg, Germany. v2: some
clarifying statements adde

### On the Hadronic light-by-light contribution to the muon $g-2$

This talk is about the hadronic light-by-light contribution to the muon
anomalous magnetic moment, mainly our old work but including some newer results
as well. It concentrates on the model calculations. Most attention is paid to
pseudo-scalar exchange and the pion loop contribution. Scalar, $a_1$-exchange
and other contributions are shortly discussed as well. For the $\pi^0$-exchange
a possible large cancellation between connected and disconnected diagrams is
expected.Comment: 9 pages, invited talk presented at FCCP2017 - Workshop on "Flavour
changing and conserving processes," 7-9 September 2017, Anacapri, Capri
Island, Italy. arXiv admin note: substantial text overlap with
arXiv:1510.0579

### Radiative and semileptonic decays in Chiral Perturbation Theory

I give a short overview of what has been done in radiative and semileptonic
Kaon decays in Chiral Perturbation Theory. This includes for semileptonic
decays the work which has been done to order $p^6$ including preliminary
results of isospin breaking to that order in $K_{\ell3}$. For the radiative
decays I mainly present some results from recent work concerning
$K_{\ell3\gamma}$.Comment: 5 pages, presented at Kaon International Conference (KAON07), May
21-25, 2007, Laboratori Nazionali di Frascati dell'INFN, Frascati, Ital

### Eta and Eta' physics

This talk describes the reasons why $\eta$ and $\eta^\prime$ decays are an
interesting topic of study for both theory and experiment. The main part
discusses the results of the recent calculation of $\eta\to3\pi$ at two-loop
order in ChPT. Some puzzling aspects of the results compared to earlier
dispersive calculations are highlighted. I also like to remind the reader of
the use of $\eta$ and $\eta^\prime$ decays for studying the anomaly.Comment: 10 pages, {Plenary talk given at MENU07, September 10-14, 2007
J\"ulich, German

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