800 research outputs found
Investigating scalar meson mixing in nucleon--nucleon and deuteron--deuteron collisions
The advantages to study charge--symmetry breaking and especially the
phenomenon of f0-a0 mixing in nucleon--nucleon and deuteron--deuteron induced
reactions are discussed.Comment: Invited talk at the international High Energy Physics Workshop
'Scalar Mesons: an Interesting Puzzle for QCD', May 16-18, 2003, SUNY
Institute of Technology, Utica, New Yor
The piNN system - recent progress
Recent progress towards an understanding of the piNN system within chiral
perturbation theory is reported. The focus lies on an effective field theory
calculation and its comparison to phenomenological calculations for the
reaction NN->d pi. In addition, the resulting absorptive and dispersive
corrections to the pi-d scattering length are discussed briefly.Comment: Plenary talk at 5th International Workshop on Chiral Dynamics, theory
and Experiment (CD 2006), Durham / Chapel Hill, North Carolina, 18-22 Sep
200
QCD tests from pion reactions on few-nucleon systems
We show on two examples, namely a calculation for charge symmetry breaking in
pn->d pi^0 that allows one to extract the quark mass difference induced part of
the proton--neutron mass difference and a high precision calculation for
pion--deuteron scattering and its implications for the value of the charged
pion--nucleon coupling constant, how QCD tests can be performed from low energy
hadronic observables.Comment: 9 pages; Invited talk at workshop CHIRAL'10, Valencia (Spain), June
21-24, 201
NN-->NNpi from the effective field theory point of view: short comings and gains
Based on a counting scheme for the application of chiral perturbation theory
to pion production in NN collisions p-wave production is studied. It is
demonstrated that, contrary to the s-wave production where loops enter at too
low an order to allow the scheme predictive power, there are certain p-wave
observables where parameter free predictions are possible. These predictions
are consistent with experimental data. We show that the investigation of
charged pion production yields a constraint on a contribution to the
three-nucleon force with a spin-isospin structure that could resolve the
puzzle in scattering.Comment: 4 pages, 3 figures, Contribution to "MESON2000", Workshop on
production, properties and interaction of mesons, Cracow, Poland, 19-23 May
200
Theoretical understanding of pion production in nucleon-nucleon collisions - a status report
A status report is given for the current theoretical understanding of pion
production close to threshold. In the first part of the talk predictions of a
meson exchange model are compared to recent polarized data for the reactions
as well as revealing, that the former reaction
is badly described whereas the predictions for the latter turn out to be
consistent with the data. Recent progress in the application of chiral
perturbation theory allows to understand this difference.Comment: 3 pages, 1 figure, Presented at the 7th International Workshop on
Meson Production, Properties and Interactions, MESON2002, Krakow, Polan
Meson exchange models for Meson production
The production of mesons in nucleon-nucleon collisions is reviewed from the
viewpoint of the meson-exchange picture. In the first part various possible
production mechanisms and their relative importance are discussed. In addition,
general features of meson production are described.
In the second part special emphasis is put on pion production. Implications
of chiral perturbation theory are discussed. Results based on a specific
meson-exchange model for pion production in nucleon-nucleon collisions are
presented. The model is utilized to calculate several spin-dependent
observables of the reactions and such as
spin-correlation parameters. This allows us to study the role of the Delta
resonance at close to threshold energies.
The talk closes with a brief discussion of the production of mesons as
an example for the production of heavier mesons. A strategy is outlined that
allows to extract information on the structure of the nucleon from the reaction
.Comment: Invited talk at the 4th International Conference on Physics at
Storage Rings (STORI99), Bloomington, IN USA, Sept. 12-16, 1999; 15 pages, 6
figure
Modelling low-mass resonances in multi-body decays
Recent advances towards a model-independent description of hadronic few-body
final states, relevant for the extraction of direct CP violation from the
decays of heavy mesons, are presented.Comment: 10 pages; to appear in the proceedings of The 6th International
Workshop on Charm Physics (CHARM 2013
How and when can one identify hadronic molecules in the baryon spectrum
A method to identify hadronic molecules in the particle spectrum is reviewed
and the conditions for its applicability discussed. Special emphasis is put on
the discussion of molecule candidates in the baryon spectrum.Comment: Talk presentent at NSTAR 2007, 5 - 8 September 2007, Bonn, German
Complete next-to-leading order calculation for pion production in nucleon-nucleon collisions at threshold
Based on a counting scheme that explicitly takes into account the large
momentum sqrt(M m_pi) characteristic for pion production in nucleon-nucleon
collisions we calculate all diagrams for the reaction NN --> NN pi at threshold
up to next-to-leading order. At this order there are no free parameters and the
size of the next-to-leading order contributions is in line with the expectation
from power counting. The sum of loop corrections at that order vanishes for the
process pp --> pp pi^0 at threshold. The total contribution at next-to-leading
order from loop diagrams that include the delta degree of freedom vanishes at
threshold in both reaction channels pp --> pp pi^0, pn pi^+.Comment: 9 pages, 4 figure
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