Nucleon Polarisabilities from Deuteron Compton Scattering, and Its Lessons for Chiral Power Counting

A brief review of Compton scattering off the deuteron in Chiral Effective Field Theory, including gauge invariance and the correct Thomson limit. We model-independently determine the iso-scalar, spin-independent dipole polarisabilities of the nucleon at zero energy from all Compton data below 100 MeV as \alpha_{E1}^s=11.3+-0.7_{stat}\+-0.6_{Baldin}+-1_{theory}, \beta_{M1}^s=3.2-+0.7_{stat}+-0.6_{Baldin}+-1_{theory}, each in 10^{-4} fm^3. Proton and neutron polarisabilities are therefore identical within (predominantly statistical) errors.Comment: 3 pages LaTeX2e, including 1 figures in 2 .eps files embedded with includegraphicx. Contribution to the 5th International Workshop on Chiral Dynamics, Theory and Experiment, Durham/Chapel Hill NC (USA), 18th -- 22nd September 2006. To be published in the proceeding

A Consistency Test of EFT Power Countings from Residual Cutoff Dependence

A method to quantitatively assess the consistency of power-counting proposals in Effective Field Theories (EFT) which are non-perturbative at leading order is presented. The Renormalisation Group evolution of an observable predicts the functional form of its residual cutoff dependence on the breakdown scale of an EFT, on the low-momentum scales, and on the order of the calculation. Passing this test is a necessary but not sufficient consistency criterion for a suggested power counting whose exact nature is disputed. In Chiral Effective Field Theory (ChiEFT) with more than one nucleon, a lack of universally accepted analytic solutions obfuscates the convergence pattern in results. This led to proposals which predict different sets of Low Energy Coefficients (LECs) at the same chiral order, and at times even predict a different ordering long-range contributions. The method may independently check whether an observable is renormalised at a given order, and proves estimates of both the breakdown scale and the momentum-dependent order-by-order convergence pattern. Conversely, it helps identify those LECs (and long-range pieces) which ensure renormalised observables at a given order. I also discuss assumptions and the relation to Wilson's Renormalisation Group; useful observable and cutoff choices; the momentum window with likely best signals; its dependence on the values and forms of cutoffs as well as on the EFT parameters; the impact of fitting LECs to data; and caveats as well as limitations. Since the test is designed to minimise the use of data, it quantitatively falsifies if the EFT has been renormalised consistently. This complements other tests which quantify how an EFT compares to experiment. Its application in particular to the 3P0 and P2-3F2 partial waves of NN scattering in ChiEFT may elucidate persistent power-counting issues.Comment: 15 pages LaTeX2e (pdflatex) including 5 figures as .pdf files using includegraphics. Final version to appear in Europ. J. Phys. A topical issue "The Tower of Effective (Field) Theories and the Emergence of Nuclear Phenomena". arXiv admin note: substantial text overlap with arXiv:1511.00490 Author's note: substantial corrections in key argument and expansions. Version appearing in Eur Phys J

Deuteron Compton Scattering: A Random Walk

In this sketch, some recent developments in Compton scattering off the deuteron are reviewed. The strong energy-dependence of the scalar magnetic dipole polarisability \beta_M1 turns out to be crucial to understand the data from Saskatoon at 94 MeV. Chiral Effective Field Theory is used to extract the static iso-scalar dipole polarisabilities as \bar{\alpha}^s=12.6\pm1.4_{stat}\pm1.0_{wavefu} and \bar{\beta}^s=2.3\pm1.7_{stat}\pm0.8_{wavefu}, in units of 10^{-4} fm^3. Therefore, proton and neutron polarisabilities are identical within error bars. For details and a better list of references, consult the given references.Comment: 8 pages LaTeX2e with 6 figures, using graphicx and aipproc. Plenary talk given at the 19th European Conference on Few-Body Problems in Physics, Groningen (The Netherlands), 23rd - 27th August 2004. To be published in the proceeding

Perturbative Pions in Deuteron Compton Scattering and Three Body Physics

Elastic deuteron Compton scattering and the quartet S wave of nd scattering are investigated in the effective field theory of nuclear physics with perturbative pions. Convergence and aggreement with experiment are good.Comment: 2 pages stone-age LaTeX2 with 2 figures, using sprocl.sty and epsfig (4 .eps figures). Abstract of a talk held at the Workshop Chiral Dynamics 2000: Theory and Experiment, TJNL (Newport News,USA) 17th -- 22nd July 2000; to be published in the Proceeding

A Tale of Two and Three Bodies

This presentation is a concise teaser for the Effective Field Theory (EFT) of two and three nucleon systems as it emerged in the last three years, using a lot of words and figures, and a few cheats.Comment: 6 pages LaTeX2e with 3 figures, using ws-p8-50x6-00.cls (included), epsfig (4 .eps figures) and feynmp (necessary Metapost files included). Talk held at the Conference Bologna 2000 - Structure of the Nucleus at the Dawn of the Century, Bologna (Italy) 29th May -- 3rd June 2000; to be published in the Proceeding

Effective Field Theory with Two and Three Nucleons

Progress in the Effective Field Theory of two and three nucleon systems is sketched, concentrating on the low energy version in which pions are integrated out as explicit degrees of freedom. Examples given are calculations of deuteron Compton scattering, three body forces and the triton, and nd partial waves.Comment: 11 pages LaTeX2e with 8 figures, using includegraphicx (6 .eps figures) and feynmp (necessary Metapost files included). Invited plenary talk at the XVIIth European Conference on Few Body Problems in Physics, \'Evora (Portugal) 11th -- 16th September 2000; to be published in the Proceeding