Peter C. Bruns

Publications (6)0 Total impact

• Article: Pion photoproduction off the proton in a gauge-invariant chiral unitary framework

  Maxim Mai, Peter C. Bruns, Ulf-G. Meissner
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  ABSTRACT: We investigate pion photoproduction off the proton in a manifestly gauge-invariant chiral unitary extension of chiral perturbation theory. In a first step, we consider meson-baryon scattering taking into account all next-to-leading order contact interactions. The resulting low-energy constants are determined by a fit to s-wave pion-nucleon scattering and the low-energy data for the reaction pi- p --> eta n. To assess the theoretical uncertainty, we perform two different fit strategies. Having determined the low-energy constants, we then analyse the data on the s-wave multipole amplitudes E0+ of pion and eta photoproduction. These are parameter-free predictions, as the two new low-energy constants are determined by the neutron and proton magnetic moments.
  07/2012;
• Article: Meson–baryon scattering in manifestly Lorentz invariant chiral perturbation theory

  Maxim Mai, Peter C. Bruns, Bastian Kubis, Ulf‐G. Meißner
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  ABSTRACT: We analyze meson–baryon scattering lengths in the framework of covariant baryon chiral perturbation theory at leading one‐loop order. We compute the complete set of matching relations between the dimension‐two low‐energy constants in the two‐ and three‐flavor formulations of the theory. We derive new two‐flavor low‐energy theorems for pion–hyperon scattering that can be tested in lattice simulations.
  AIP Conference Proceedings. 10/2011; 1374(1):481-484.
• Source

  Available from: ArXiv

  Article: Chiral extrapolation of nucleon wave function normalization constants

  Philipp Wein, Peter C. Bruns, Thomas R. Hemmert, Andreas Schäfer
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  ABSTRACT: Within the framework of two-flavor covariant baryon chiral perturbation theory we have expressed the Chernyak-Zhitnitsky, Ioffe and Dosch currents in terms of chiral fields to provide leading one-loop extrapolation formulae for the leading and next-to-leading twist normalization constants $f_N$, $\lambda_1$ and $\lambda_2$. Finite volume effects due to pion loops have been taken into account. The occurring low energy constants are fitted to data obtained from recent lattice QCD simulations in order to extract the values at the physical point.
  06/2011;
• Source

  Available from: ArXiv

  Article: The first PDF moments for three dynamical flavors in Baryon Chiral Perturbation Theory

  Peter C. Bruns, Ludwig Greil, Andreas Schäfer
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  ABSTRACT: We present a calculation of generalized baryon form factors in the framework of three-flavor covariant baryon chiral perturbation theory at leading one-loop order. This is needed for lattice calculations of the first moments of generalized parton distribution functions. The formulae we derive can be used to guide the chiral extrapolation of such lattice results.
  05/2011;
• Source

  Available from: ArXiv

  Article: Chiral dynamics of the S11(1535) and S11(1650) resonances revisited

  Peter C. Bruns, Maxim Mai, Ulf-G. Meißner
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  ABSTRACT: We analyze s-wave pion–nucleon scattering in a unitarized chiral effective Lagrangian including all dimension two contact terms. We find that both the S11(1535) and the S11(1650) are dynamically generated, but the S31(1620) is not. We further discuss the structure of these dynamically generated resonances.
  Physics Letters B. 12/2010;
• Source

  Available from: ArXiv

  Article: Aspects of meson-baryon scattering in three- and two-flavor chiral perturbation theory

  Maxim Mai, Peter C. Bruns, Bastian Kubis, Ulf-G. Meißner
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  ABSTRACT: We analyze meson-baryon scattering lengths in the framework of covariant baryon chiral perturbation theory at leading one-loop order. We compute the complete set of matching relations between the dimension-two low-energy constants in the two- and three-flavor formulations of the theory. We derive new two-flavor low-energy theorems for pion-hyperon and pion-cascade scattering that can be tested in lattice simulations. Comment: 22 pages, 5 figures, version published in Phys. Rev. D
  05/2009;