arXiv subjects

Harald W. Griesshammer

Publications and source records attributed to Harald W. Griesshammer.

59 records · Page 4Linked to original sources

arXiv1999

Quartet S Wave Neutron Deuteron Scattering in Effective Field Theory

The real and imaginary part of the quartet S wave phase shift in nd scattering (^4 S_{3/2}) for centre-of-mass momenta of up to 300 MeV (E_cm \approx 70 MeV) is presented in effective field theory, using both perturbative pions and a theory in which pions are integrated out. As available, the calculation agrees with both experimental data and potential model calculations, but extends to a higher, so far untested momentum régime above the deuteron breakup point. A Lagrangean more feasible for numerical computations is derived.

nucl-th↗

arXiv1998

Gamma-Deuteron Compton Scattering in Effective Field Theory

The differential cross section for gamma-deuteron Compton scattering is computed to next-to-leading order (NLO) in an effective field theory that describes nucleon-nucleon interactions below the pion production threshold. Contributions at NLO include the nucleon isoscalar electric polarizability from its 1/m_pi behavior in the chiral limit. The parameter free prediction of the gamma-deuteron differential cross section at NLO is in good agreement with data.

nucl-th↗

arXiv1998

The Polarizability of the Deuteron

The scalar and tensor polarizabilities of the deuteron are calculated using the recently developed effective field theory that describes nucleon-nucleon interactions. Leading and next-to-leading order contributions in the perturbative expansion predict a scalar electric polarizability of 0.595 fm^3. The tensor electric polarizability receives contributions starting at next-to-leading order from the exchange of a single potential pion and is found to be -0.062 fm^3. We compute the leading contributions to the scalar and tensor magnetic polarizabilities, finding 0.067 fm^3 and 0.195 fm^3, respectively.

nucl-th↗

arXiv1997

Magnetic Defects Signal Failure of Abelian Projection Gauges in QCD

Magnetically charged Abelian defects are shown to arise on most compact base manifolds and in most Abelian projection gauges. They obey the Dirac quantisation condition and give rise to homogeneous magnetic background fields. The reasons for their occurrence are global failures of the procedure with which gauge covariant operators are diagonalised or their eigenphases extracted. Defects related to the former case are string-like; for the latter case they resemble domain walls. Either configuration forms the generic case and indicates a failure of gauge fixing as continuity and periodicity properties of the functional space are changed. These results are first obtained in canonically quantised QCD_{3+1} and path integral QCD_{2+1} on the torus for the modified axial gauge which keeps only the eigenphases as dynamical variables of the Wilson line in the x_3-direction. In the end, they are extended to other gauges, dimensions and standard manifolds.

hep-ph↗

arXiv1996

Field Configurations and the SU(2) Haar Measure in QCD

We characterise a class of SU(2) gluonic field configurations in the modified axial gauge where a zero mode component vanishes at some space point but the global Haar measure remains non-zero. The consequence of this is that gluonic wavefunctionals need not vanish at the boundary of the fundamental modular domain, which itself permits $θ$ dependence in QCD(3+1).

hep-th↗