6,032 research outputs found
Performance of the distributed central analysis in BaBar
The total dataset produced by the BaBar experiment at the Stanford Linear Accelerator Center (SLAC) currently comprises roughlydata events and an equal amount of simulated events, corresponding to 23 Tbytes of real data and 51 Tbytes simulated events. Since individual analyses typically select a very small fraction of all events, it would be extremely inefficient if each analysis had to process the full dataset. A first, centrally managed analysis step is therefore a common pre-selection (âskimmingâ) of all data according to very loose, inclusive criteria to facilitate data access for later analysis. Usually, there are common selection criteria for several analysis. However, they may change over time, e.g., when new analyses are developed. Currently,$cal
Chiral approach to nuclear matter: Role of two-pion exchange with virtual delta-isobar excitation
We extend a recent three-loop calculation of nuclear matter in chiral
perturbation theory by including the effects from two-pion exchange with single
and double virtual -isobar excitation. Regularization dependent
short-range contributions from pion-loops are encoded in a few NN-contact
coupling constants. The empirical saturation point of isospin-symmetric nuclear
matter, MeV, fm, can be well reproduced
by adjusting the strength of a two-body term linear in density (and weakening
an emerging three-body term quadratic in density). The nuclear matter
compressibility comes out as MeV. The real single-particle potential
is substantially improved by the inclusion of the chiral -dynamics: it grows now monotonically with the nucleon momentum .
The effective nucleon mass at the Fermi surface takes on a realistic value of
. As a consequence of these features, the critical
temperature of the liquid-gas phase transition gets lowered to the value MeV. In this work we continue the complex-valued single-particle
potential into the region above the Fermi surface
. The effects of -exchange with virtual -excitation on the
nuclear energy density functional are also investigated. The effective nucleon
mass associated with the kinetic energy density is . Furthermore, we find that the isospin properties of nuclear matter get
significantly improved by including the chiral -dynamics.Comment: 28 pages, 13 figure
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