Nuclear Theory·nucl-th

Friday·December 16, 2016

13 papers—7 primary·6 cross-listed

08
Jet axes and universal transverse-momentum-dependent fragmentation
Duff Neill🇺🇸 · Ignazio Scimemi🇪🇸 · Wouter J. Waalewijn🇳🇱
We study the transverse momentum spectrum of hadrons in jets. By measuring the transverse momentum with respect to a judiciously chosen axis, we find that this observable is insensitive to (the recoil of) soft radiation. Furthermore, for small transverse momenta we show that the effects of the jet boundary factorize, leading to a new transverse-momentum-dependent (TMD) fragmentation function. In contrast to the usual TMD fragmentation functions, it does not involve rapidity divergences and is universal in the sense that it is independent of the type of process and number of jets. These results directly apply to sub-jets instead of hadrons. We discuss potential applications, which include studying nuclear modification effects in heavy-ion collisions and identifying boosted heavy resonances.
↳ hep-phnucl-thJHEP(2017)·68 citations
09
Threshold effects in P-wave bottom-strange mesons
Pablo G. Ortega🇪🇸 · Jorge Segovia🇩🇪 · David R. Entem🇪🇸 · Francisco Fernández🇪🇸
Using a nonrelativistic constituent quark model in which the degrees of freedom are quark-antiquark and meson-meson components, we have recently shown that the $D^{(*)} K$ thresholds play an important role in lowering the mass of the physical $D_{s 0}^{*} (2317)$ and $D_{s 1} (2460)$ states. This observation is also supported by other theoretical approaches such as lattice-regularised QCD or chiral unitary theory in coupled channels. Herein, we extend our computation to the lowest $P$ -wave $B_{s}$ mesons, taking into account the corresponding $J^{P} = 0^{+}$ , $1^{+}$ and $2^{+}$ bottom-strange states predicted by the naive quark model and the $B K$ and $B^{*} K$ thresholds. We assume that mixing with $B_{s}^{(*)} η$ and isospin-violating decays to $B_{s}^{(*)} π$ are negligible. This computation is important because there is no experimental data in the $b s ˉ$ sector for the equivalent $j_{q}^{P} = 1/ 2^{+}$ ( $D_{s 0}^{*} (2317)$ , $D_{s 1} (2460)$ ) heavy-quark multiplet and, as it has been seen in the $c s ˉ$ sector, the naive theoretical result can be wrong by more than $100 MeV$ . Our calculation allows to introduce the coupling with the $D$ -wave $B^{*} K$ channel and to compute the probabilities associated with the different Fock components of the physical state.
↳ hep-phhep-exhep-latnucl-thPRD(2017)·49 citations
10
Dynamics, nucleosynthesis, and kilonova signature of black hole - neutron star merger ejecta
Rodrigo Fernández · Francois Foucart · Daniel Kasen · Jonas Lippuner · Dhruv Desai · Luke F. Roberts
We investigate the ejecta from black hole - neutron star mergers by modeling the formation and interaction of mass ejected in a tidal tail and a disk wind. The outflows are neutron-rich, giving rise to optical/infrared emission powered by the radioactive decay of $r$ -process elements (a kilonova). Here we perform an end-to-end study of this phenomenon, where we start from the output of a fully-relativistic merger simulation, calculate the post-merger hydrodynamical evolution of the ejecta and disk winds including neutrino physics, determine the final nucleosynthetic yields using post-processing nuclear reaction network calculations, and compute the kilonova emission with a radiative transfer code. We study the effects of the tail-to-disk mass ratio by scaling the tail density. A larger initial tail mass results in fallback matter becoming mixed into the disk and ejected in the subsequent disk wind. Relative to the case of a disk without dynamical ejecta, the combined outflow has lower mean electron fraction, faster speed, larger total mass, and larger absolute mass free of high-opacity Lanthanides or Actinides. In most cases, the nucleosynthetic yield is dominated by the heavy $r$ -process contribution from the unbound part of the tidal tail. A Solar-like abundance distribution can however be obtained when the total mass of the dynamical ejecta is comparable to the mass of the disk outflows. The kilonova has a characteristic duration of 1 week and a luminosity of ~ $1 0^{41}$ erg/s, with orientation effects leading to variations of a factor ~2 in brightness. At early times (< 1 day) the emission includes an optical component from the (hot) Lanthanide-rich material, but the spectrum evolves quickly to the infrared thereafter.
↳ astro-ph.HEastro-ph.SRgr-qcnucl-thClass.Quant.Grav.(2017)·115 citations
11
Prospects for neutrino oscillation parameters
Patrick Huber🇺🇸
In this contribution we discuss the future of the global long-baseline neutrino oscillation program. The case is made that our current lack of understanding of neutrino-nucleus interactions is a serious challenge which will need to be met with new experimental initiatives in neutrino scattering.
↳ hep-phhep-exnucl-thPoS(2017)·2 citations
12
$p_{t}$ -Angular power spectrum in ALICE events
Felipe J. Llanes-Estrada🇪🇸 · Jose L. Muñoz Martinez (Univ. Complutense de Madrid)🇪🇸
We study the particles emitted in the fireball following a Relativistic Heavy Ion Collision with the traditional angular analysis employed in cosmology and earth sciences, producing Mollweide plots of the p_t distribution of a few actual, publically released ALICE-collaboration events and calculating their angular power spectrum. With the limited statistics at hand, we do not find evidence for acoustic peaks but a decrease of C_l that is reminiscent of viscous attenuation, but subject to a strong effect from the rapidity acceptance which probably dominates (so we also subtract the m=0 component). As an exercise, we still extract a characteristic Silk damping length (proportional to the square root of the viscosity over entropy density ratio). The absence of acoustic-like peaks is also compatible with a crossover from the QGP to the hadron gas (because a surface tension at domain boundaries would effect a restoring force that could have driven acoustic oscillations). Presently an unexpected depression appears in the l=6 multipole strength, which should be revisited by the ALICE collaboration with full statistics to confirm or discard it.
↳ hep-phnucl-exnucl-thNPA(2018)·8 citations
13
A shoving model for collectivity in hadronic collisions
Christian Bierlich🇸🇪 · Gösta Gustafson🇸🇪 · Leif Lönnblad🇸🇪
An extension of the rope hadronization model, which has previously provided good descriptions of hadrochemistry in high multiplicity pp collisions, is presented. The extension includes a dynamically generated transverse pressure, produced by the excess energy from overlapping strings. We find that this model can qualitatively reproduce soft features of Quark Gluon Plasma in small systems, such as higher $⟨ p_{⊥} ⟩$ for heavier particles and long range azimuthal correlations forming a ridge. The effects are similar to those obtained from a hydrodynamic expansion, but without assuming a thermalized medium.
↳ hep-phnucl-th83 citations

Affiliations

first authorsco-authorsvia INSPIRE

Jet axes and universal transverse-momentum-dependent fragmentation

Threshold effects in P-wave bottom-strange mesons

Dynamics, nucleosynthesis, and kilonova signature of black hole - neutron star merger ejecta

Prospects for neutrino oscillation parameters

pt​-Angular power spectrum in ALICE events

A shoving model for collectivity in hadronic collisions

Affiliations

$p_{t}$ -Angular power spectrum in ALICE events