| Autor: |
Lensky, Vadim, McGovern, Judith Ann, Phillips, Daniel Robertson, Pascalutsa, Vladimir, Vadim Lensky, Judith A. McGovern, Daniel R. Phillips, Vladimir Pascalutsa |
| Jazyk: |
angličtina |
| Rok vydání: |
2012 |
| Předmět: |
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| Zdroj: |
Lensky, V, McGovern, J A, Phillips, D R & Pascalutsa, V 2012, ' Proton Compton scattering cross section in different variants of chiral effective field theory ', Physical Review C-Nuclear Physics, vol. 86, no. 4, 048201 . https://doi.org/10.1103/PhysRevC.86.048201 |
| Popis: |
Experiments to measure Compton scattering from the proton are presently being pursued at a number of fa- cilities around the world, including MAMI (Mainz) and HIS at TUNL. Chiral effective field theory (�EFT) is one of the main theoretical techniques used to analyze p scattering data in the energy range !lab < 350 MeV. �EFT generates the most general Compton amplitude that is consistent with electromagnetic gauge invariance, the pattern of chiral-symmetry breaking in QCD, and Lorentz covariance, to any given order of the small pa- rameter P � {!,m�}/�, with ! the photon energy, m� the pion mass andthe breakdown scale of the theory. By now, �EFT calculations of the p amplitude ex- ist in several different variants of the theory. Two key choices must be made: whether to include the �(1232) resonance explicitly, and whether to maintain exact Lorentz covariance or not. The pioneering calculations of Compton scattering inEFT (2, 3) were performed in a theory with only nucleons and pions as explicit de- grees of freedom: the effects of thewere encoded in a string of contact operators. This reduces the break- down scalefrom its nominal value around the mass of themeson to the energy at which theis excited, i.e. MMN � 300 MeV. In addition this work employed the heavy-baryon (HB) expansion for the nucleon propa- gators, which amounts to making an expansion in 1/MN, alongside the EFT expansion in P. In these calculations the polarizabilities � (p)1 and � (p)1 are predicted at order P 3 , and these predictions are in remarkably good agree- ment with present extractions from data (4, 5). The cor- responding results for p observables agree moderately well with data for !, p |t| < 150 MeV (6-8). Beyond this domain the absence of thesignificantly affects the abil- ity of thisEFT variant to describe the physics, at least at this low order in the expansion. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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