nucl-th digest · May 25, 2018

The Role of Tensor Force in Heavy-Ion Fusion Dynamics

The tensor force is implemented into the time-dependent Hartree-Fock (TDHF) theory so that both exotic and stable collision partners, as well as their dynamics in heavy-ion fusion, can be described microscopically. The role of tensor force on fusion dynamics is systematically investigated for

^{40} Ca +^{40} Ca

^{40} Ca +^{48} Ca

^{48} Ca +^{48} Ca

^{48} Ca +^{56} Ni

, and

^{56} Ni +^{56} Ni

reactions which vary by the total number of spin-unsaturated magic numbers in target and projectile. A notable effect on fusion barriers and cross sections is observed by the inclusion of tensor force. The origin of this effect is analyzed. The influence of isoscalar and isovector tensor terms is investigated with the T

I J

forces. These effects of tensor force in fusion dynamics are essentially attributed to the shift of low-lying vibration states of colliding partners and nucleon transfer in the asymmetric reactions. Our calculations of above-barrier fusion cross sections also show that tensor force does not significantly affect the dynamical dissipation at near-barrier energies.

nucl-thnucl-exPLB(2018)·54 citations

The cathode tube effect: heavy quarks probing the Glasma in p-Pb collisions

Marco Ruggieri🇨🇳 · Santosh K. Das🇨🇳

We study the propagation of charm quarks in the early stage of high energy proton-lead collision, considering the interaction of these quarks with the evolving Glasma by means of the Wong equations. Neglecting quantum fluctuations at the initial time the Glasma is made of longitudinal fields, but the dynamics leads to a quick formation of transverse fields; we estimate such a formation time as $Δ t \approx 0.1$ fm/c which is of the same order of the formation time of heavy quark pairs $t_{formation} \approx 1/ (2 m)$ . Limiting ourselves to the simple case of a static longitudinal geometry, we find that heavy quarks are accelerated by the strong transverse color fields in the early stage and this leads to a tilting of the $c -$ quarks spectrum towards higher $p_{T}$ states. This average acceleration can be understood in terms of drag and diffusion of $c -$ quarks in a hot medium and appears to be similar to the one felt by the electrons ejected by the electron cannon in a cathode tube: we dub this effect as {\it cathode tube effect}. The tilting of the spectrum affects the nuclear modification factor, $R_{pPb}$ , suppressing this below one at low $p_{T}$ and making it larger than one at intermediate $p_{T}$ . We compute $R_{pPb} (p_{T})$ after the evolution of charm quarks in the gluon fields and we find that its shape is in qualitative agreement with the measurements of the same quantity for $D -$ mesons in proton-lead collisions.

nucl-thhep-phnucl-exPRD(2018)·55 citations

Friday·May 25, 2018

The Role of Tensor Force in Heavy-Ion Fusion Dynamics

The cathode tube effect: heavy quarks probing the Glasma in p-Pb collisions

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