Thu·Aug 1, 2002Thursday·August 1, 2002

1. 01*

   Non-Zero Magnetic Screening Mass in QED and QCD at One Loop Level in Non-Equilibrium

   Fred Cooper (LANL)🇺🇸 · Chung-Wen Kao (Manchester)🇬🇧 · Gouranga C. Nayak (LANL)🇺🇸

   Using the Schwinger-Keldysh closed time path integral formalism we show that the magnetic screening mass in QED and QCD at one loop level is non-zero as long as the single particle distribution function f(\vec{k}) is non-isotropic, {i.e.} it depends on the direction of the momentum. For isotropic distribution functions such as those corresponding to thermal equilibrium the magnetic screening mass at one loop level is found to be zero which is consistent with finite temperature field theory. The non-zero magnetic screening mass in non-isotropic non-equlibrium situations has fundamental importance in that it acts as a natural cut-off to remove infrared divergences in the magnetic sector. Thus it allows one to avoid infrared problems which previously made it difficult to use a transport theory approach using perturbative QCD or QED scattering kernels to study the thermalization of a QED or QCD plasma.

   ↳ hep-phhep-lathep-thnucl-th26 citations
2. 02*

   Nuclear forces in the chiral limit

   Evgeny Epelbaum🇩🇪 · Ulf-G. Meißner🇩🇪 · Walter Glöckle🇩🇪

   We investigate the behaviour of the nuclear forces as a function of the light quark masses (or, equivalently, pion mass) in the framework of chiral effective field theory at next-to-leading order. The nucleon-nucleon force is described in terms of one- and two-pion exchange and local short distance operators, which depend explicitly and implicitly on the quark masses. The pion propagator becomes Coulomb-like in the chiral limit and thus one has significant scattering in all partial waves. The pion-nucleon coupling depends implicitly on the quark masses and we find that it becomes stronger in the chiral limit. There is a further quark mass dependence in the S-wave four--nucleon couplings, which can be estimated by means of dimensional analysis. We find that nuclear physics in the chiral limit becomes natural. There are no new bound states, the deuteron binding energy is B_D^{CL} = 9.6 +/- 1.9^+1.8_-1.0 MeV, and the S-wave scattering lengths take values of a few fm, a_{CL} (^1S_0) = -4.1 +/- 1.6^+0.0_-0.4 fm and a_{CL} (^3S_1) = 1.5 +/- 0.4^+0.2_-0.3 fm. We also discuss the extrapolation to larger pion masses pertinent for the extraction of these quantities from lattice simulations.

   ↳ nucl-thhep-lathep-phNPA(2003)·219 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.