nucl-th digest · May 25, 2017

Effect of finite particle number sampling on baryon number fluctuations

The effects of finite particle number sampling on the net baryon number cumulants, extracted from fluid dynamical simulations, are studied. The commonly used finite particle number sampling procedure introduces an additional Poissonian (or multinomial if global baryon number conservation is enforced) contribution which increases the extracted moments of the baryon number distribution. If this procedure is applied to a fluctuating fluid dynamics framework one severely overestimates the actual cumulants. We show that the sampling of so called test-particles suppresses the additional contribution to the moments by at least one power of the number of test-particles. We demonstrate this method in a numerical fluid dynamics simulation that includes the effects of spinodal decomposition due to a first order phase transition. Furthermore, in the limit where anti-baryons can be ignored, we derive analytic formulas which capture exactly the effect of particle sampling on the baryon number cumulants. These formulas may be used to test the various numerical particle sampling algorithms.

Comments:: 9 pages 3 figures
Subjects:: Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:: 1705.08538 [pdf]

PRC(2017)·18 citations

[Submitted on 24 May 2017]

Emergence of clusters: Halos, Efimov states, and experimental signals

D. Hove · E. Garrido · P. Sarriguren · D.V. Fedorov · H.O.U. Fynbo · A.S. Jensen · N.T. Zinner

We investigate emergence of halos and Efimov states in nuclei by use of a newly designed model which combines self-consistent mean-field and three-body descriptions. Recent interest in neutron heavy calcium isotopes makes $^{72}$ Ca ( $^{70}$ Ca+n+n) an ideal realistic candidate on the neutron dripline, and we use it as a representative example that illustrates our broadly applicable conclusions. By smooth variation of the interactions we simulate the crossover from well-bound systems to structures beyond the threshold of binding, and find that halo-configurations emerge from the mean-field structure for three-body binding energy less than $\sim 100$ keV. Strong evidence is provided that Efimov states cannot exist in nuclei. The structure that bears the most resemblance to an Efimov state is a giant halo extending beyond the neutron-core scattering length. We show that the observable large-distance decay properties of the wave function can differ substantially from the bulk part at short distances, and that this evolution can be traced with our combination of few- and many-body formalisms. This connection is vital for interpretation of measurements such as those where an initial state is populated in a reaction or by a beta-decay.

Comments:: 5 pages, 5 figures, under review
Subjects:: Nuclear Theory (nucl-th)
arXiv:: 1705.08718 [pdf]

PRL(2018)·24 citations

Thursday·May 25, 2017

Effect of finite particle number sampling on baryon number fluctuations

Emergence of clusters: Halos, Efimov states, and experimental signals

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