Nuclear Theory·nucl-th

Friday·June 15, 2018

6 papers—2 primary·4 cross-listed

01
Low-energy quadrupole states in neutron-rich tin nuclei
E. Yüksel🇭🇷 · G. Colò🇮🇹 · E. Khan🇫🇷 · Y. F. Niu🇷🇴
We present a study on the isoscalar quadrupole strength in tin nuclei, focusing mainly on the low-energy region. The calculations are performed using the Skyrme type energy density functionals within the fully self-consistent quasiparticle random phase approximation, allowing for a good description of the experimental data for the first 2 $^{+}$ state and the isoscalar giant quadrupole resonance. It is found that the first $2^{+}$ state and the low-energy quadrupole states between 3 and 6 MeV display an opposite behavior with increasing neutron number. While the strength of the first $2^{+}$ state decreases, some excited states start to accumulate between 3 and 6 MeV, and increase their strength with increasing neutron number. This low-energy region between 3 and 6 MeV is quite sensitive to the changes in the shell structure with increasing neutron number. In particular, between $^{116}$ Sn and $^{132}$ Sn, the filling of the neutron orbitals with large values of $j$ , has an important impact on the low-energy region. Our analysis shows that the low-energy states have a non-collective character, except the first 2 $^{+}$ state. In addition, the states in the low-energy region above 5 MeV display an interesting pattern: with the increase of the neutron number, their strength increases and their nature changes, namely they switch from proton excitations to neutron-dominated one. We conclude that the low-energy quadrupole states between 3 and 6 MeV can provide information about the shell evolution in open-shell nuclei.
nucl-thnucl-exPRC(2018)·14 citations
02
Probing the in-Medium QCD Force by Open Heavy-Flavor Observables
Shuai Y.F. Liu🇺🇸 · Min He🇨🇳 · Ralf Rapp🇺🇸
The determination of the color force in a quark-gluon plasma (QGP) is a key objective in the investigation of strong-interaction matter. Open and hidden heavy-flavor observables in heavy-ion collisions (HICs) are believed to provide insights into this problem by comparing calculations of heavy-quark (HQ) and quarkonium transport with pertinent experimental data. In this work, we utilize the $T$ -matrix formalism to compute charm-quark transport coefficients for various input potentials previously extracted from simultaneous fits to lattice-QCD data for HQ free energies, quarkonium correlators and the QGP equation of state. We investigate the impact of off-shell effects (spectral functions) in the QGP medium on the HQ transport, and compare to earlier results using the free or internal HQ energies as potential proxies. We then employ the transport coefficients in relativistic Langevin simulations for HICs to test the sensitivity of heavy-flavor observables to the HQ interactions in the QGP. We find that a strongly-coupled $T$ -matrix solution generates a HQ elliptic flow comparable to the results from the internal energy at low momentum, driven by a long-range remnant of the confining force, while falling off stronger with increasing 3-momentum. The weakly coupled $T$ -matrix solution, whose underlying potential is close to the free energy, leads to an elliptic flow well below the experimentally observed range.
nucl-thhep-phnucl-exPRC(2019)·42 citations
03
Hollowness in $pp$ and $p p ˉ$ scattering in a Regge model
Wojciech Broniowski🇵🇱 · László Jenkovszky🇺🇦 · Enrique Ruiz Arriola🇪🇸 · István Szanyi🇺🇦
The proton-proton and proton-antiproton inelasticity profiles in the impact parameter display very interesting and sensitive features which cannot be deduced solely from the current large body of high-energy scattering data. In particular, phenomenological studies exhibit a link between the ratio of the real to imaginary parts of the elastic scattering amplitude at a finite momentum transfer, and the corresponding change of character of the inelastic processes from central to peripheral collisions. We describe how a theoretical model, accommodating the existing data, based on the Regge hypothesis including both the Pomeron and odderon as double poles, and $ω$ and $f$ mesons as single poles in the complex- $J$ plane, generates a hollow in the inelasticity at low impact parameters. The hollowness effect, which generally may be sensitive to model details, does unequivocally take place both for $pp$ and $p p ˉ$ collisions within the applied Regge framework, indicating inapplicability of inelasticity-folding geometric approaches.
↳ hep-phnucl-thPRD(2018)·47 citations
04
Charge-dependent Flow Induced by Magnetic and Electric Fields in Heavy Ion Collisions
Umut Gürsoy🇳🇱 · Dmitri Kharzeev🇺🇸 · Eric Marcus🇳🇱 · Krishna Rajagopal🇺🇸 · Chun Shen🇺🇸
We investigate the charge-dependent flow induced by magnetic and electric fields in heavy ion collisions. We simulate the evolution of the expanding cooling droplet of strongly coupled plasma hydrodynamically, using the iEBE-VISHNU framework, and add the magnetic and electric fields as well as the electric currents they generate in a perturbative fashion. We confirm the previously reported effect of the electromagnetically induced currents, that is a charge-odd directed flow $Δ v_{1}$ that is odd in rapidity, noting that it is induced by magnetic fields (à la Faraday and Lorentz) and by electric fields (the Coulomb field from the charged spectators). In addition, we find a charge-odd $Δ v_{3}$ that is also odd in rapidity and that has a similar physical origin. We furthermore show that the electric field produced by the net charge density of the plasma drives rapidity-even charge-dependent contributions to the radial flow $⟨ p_{T} ⟩$ and the elliptic flow $Δ v_{2}$ . Although their magnitudes are comparable to the charge-odd $Δ v_{1}$ and $Δ v_{3}$ , they have a different physical origin, namely the Coulomb forces within the plasma.
↳ hep-phhep-thnucl-exnucl-thPRC(2018)·127 citations
05
$Ξ$ (2030) and $Ξ$ (2120) as $K ˉ^{*} Σ$ molecular states
Yin Huang🇨🇳 · Rong Wang🇫🇷 · Jun He🇨🇳 · Ju-Jun Xie🇨🇳 · Lisheng Geng🇨🇳
In this work, the molecular states from the \bar{K}^{*}\Sigma interaction are studied in a quasipotential Bethe-Salpeter equation approach with the one-boson-exchange potentials. We consider the exchanges of vector (\rho,\omega and \phi) mesons and pseudoscalar (\pi and \eta) mesons to describe the \bar{K}^{*}\Sigma interaction with the coupling constants determined by the SU(3) symmetry, The poles of the scattering amplitude are searched for to find the molecular states dynamically generated from the \bar{K}^{*}\Sigma interaction. A bound state with quantum number I(J^{p})=1/2(5/2^{+}) is produced, which can be associated to the \Xi(2030) baryon. Other bound states with J\le{}5/2 are also searched for and it is found that there exist bound states with quantum numbers I(J^P)=1/2(1/2^-), 1/2(3/2^{-}), and 1/2(3/2^+). The \Xi(2120) may be a candidate for one of these three bound states. In addition, we also find two bound states with isospin 3/2 and spin parities 1/2^- and 1/2^+.
↳ hep-phnucl-th2 citations
06
Inverting the mass hierarchy of jet quenching effects with prompt $b$ -jet substructure
Ivan Vitev🇺🇸
In these proceedings, we discuss the role of heavy quark mass on the formation of parton showers. Mass effects are not well understood when parton branching occurs in nuclear matter, such as the quark-gluon plasma. Recently, a theoretically consistent picture of open heavy flavor production in ultra relativistic nuclear collisions has begun to emerge based on effective theories of QCD, such as soft collinear effective theory with Glauber gluons. We show that implementation of in-medium splitting processes containing heavy quarks into next-to-leading order calculations of heavy flavor production leads to larger cross section suppression when compared to traditional energy loss phenomenology. To better constrain the important mass dependence of in-medium splitting functions, we propose a new measurement in relativistic heavy ion collisions, based on a two-prong structure inside a reconstructed heavy flavor jet. In the region of jet transverse momenta where parton mass effects are leading, we predict a unique reversal of the mass hierarchy of jet quenching effects in heavy ion relative to proton collisions. We find that the momentum sharing distribution of prompt $b$ -tagged jets is more strongly modified in comparison to the one for light jets. The work summarized here opens new directions of research on the substructure of heavy flavor jets.
↳ hep-phnucl-thJ.Phys.Conf.Ser.(2018)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE

Low-energy quadrupole states in neutron-rich tin nuclei

Probing the in-Medium QCD Force by Open Heavy-Flavor Observables

Hollowness in pp and ppˉ​ scattering in a Regge model

Charge-dependent Flow Induced by Magnetic and Electric Fields in Heavy Ion Collisions

Ξ(2030) and Ξ(2120) as Kˉ∗Σ molecular states

Inverting the mass hierarchy of jet quenching effects with prompt b-jet substructure

Affiliations

Hollowness in $pp$ and $p p ˉ$ scattering in a Regge model

$Ξ$ (2030) and $Ξ$ (2120) as $K ˉ^{*} Σ$ molecular states

Inverting the mass hierarchy of jet quenching effects with prompt $b$ -jet substructure