Mauro Elias | Searcharxiv

arXiv2014

Heavy quark collisional energy loss in the quark-gluon plasma including finite relaxation time

In this paper, we calculate the soft-collisional energy loss of heavy quarks traversing the viscous quark-gluon plasma including the effects of a finite relaxation time $τ_π$ on the energy loss. We find that the collisional energy loss depends appreciably on $τ_π$ . In particular, for typical values of the viscosity-to-entropy ratio, we show that the energy loss obtained using $τ_π$ = 0 can be $\sim$ 10$\%$ larger than the one obtained using $τ_π$ = 0. Moreover, we find that the energy loss obtained using the kinetic theory expression for $τ_π$ is much larger that the one obtained with the $τ_π$ derived from the Anti de Sitter/Conformal Field Theory correspondence. Our results may be relevant in the modeling of heavy quark evolution through the quark-gluon plasma.

hep-ph↗

arXiv2013

Rotational Characterization of Hayabusa II Target Asteroid (162173) 1999 JU3

The Japanese Space Agency's Hayabusa II mission is scheduled to rendezvous with and return a sample from the near-Earth asteroid (162173) 1999 JU3. Previous visible-wavelength spectra of this object show significant variability across multiple epochs which could be the result of a compositionally heterogeneous surface. We present new visible and near-infrared spectra to demonstrate that thermally altered carbonaceous chondrites are plausible compositional analogs, however this is a tentative association due to a lack of any prominent absorption features in our data. We have also conducted a series of high signal-to-noise visible-wavelength observations to investigate the reported surface heterogeneity. Our time series of visible spectra do not show evidence for variability at a precision level of a few percent. This result suggests two most likely possibilities. One, that the surface of 1999 JU3 is homogenous and that unaccounted for systematic effects are causing spectral variation across epochs. Or two, that the surface of 1999 JU3 is regionally heterogenous, in which case existing shape models suggest that any heterogeneity must be limited to terrains smaller than approximately 5% of the total surface area. These new observations represent the last opportunity before both the launch and return of the Hayabusa II spacecraft to perform ground-based characterization of this asteroid. Ultimately, these predictions for composition and surface properties will be tested upon completion of the mission.

astro-ph.EP↗