Fri·Feb 28, 2020Friday·February 28, 2020

1. 01*

   Two-neutron knockout as a probe of the composition of states in ${}^{22}$Mg, ${}^{23}$Al, and ${}^{24}$Si

   B. Longfellow🇺🇸 · A. Gade🇺🇸 · J. A. Tostevin🇬🇧 · E. C. Simpson🇦🇺 · B. A. Brown🇺🇸 · A. Magilligan🇺🇸 · D. Bazin🇺🇸 · P. C. Bender🇨🇦 · M. Bowry🇺🇸 · B. Elman · E. Lunderberg🇺🇸 · D. Rhodes🇺🇸 and 3 other authors

   Simpson and Tostevin proposed that the width and shape of exclusive parallel momentum distributions of the A-2 residue in direct two-nucleon knockout reactions carry a measurable sensitivity to the nucleon single-particle configurations and their couplings within the wave functions of exotic nuclei. We report here on the first benchmarks and use of this new spectroscopic tool. Exclusive parallel momentum distributions for states in the neutron-deficient nuclei ${}^{22}$Mg, ${}^{23}$Al, and ${}^{24}$Si populated in such direct two-neutron removal reactions were extracted and compared to predictions combining eikonal reaction theory and shell-model calculations. For the well-known ${}^{22}$Mg and ${}^{23}$Al nuclei, measurements and calculations were found to agree, supporting the dependence of the parallel momentum distribution width on the angular momentum composition of the shell-model two-neutron amplitudes. In ${}^{24}$Si, a level at 3439(9) keV, of relevance for the important ${}^{23}$Al(p,$\gamma$)${}^{24}$Si astrophysical reaction rate, was confirmed to be the $2_2^{+}$ state, while the $4_1^{+}$ state, expected to be strongly populated in two-neutron knockout, was not observed. This puzzle is resolved by theoretical considerations of the Thomas-Ehrman shift, which also suggest that a previously reported 3471-keV state in ${}^{24}$Si is in fact the ($0_2^{+}$) level with one of the largest experimental mirror-energy shifts ever observed.

   nucl-exPRC(2020)·20 citations
2. 02*

   Long-range collectivity in small collision-systems with two- and four-particle correlations @ STAR

   Roy A. Lacey (for the STAR Collaboration)🇺🇸

   New STAR differential and integral v{2,3} measurements that explicitly account for non-flow contributions are reported for p/d/3He+Au, collisions at Roots=200 GeV. The measurements, which leverage the two-particle correlators for p/d/3He+Au and minimum-bias p+p collisions in tandem with three well-established methods of non-flow subtraction, are observed to be method-independent. For comparable multiplicities, they further indicate system-independent v2{2} and v3{2} values that are consistent with the critical role of both size (N{ch}) and the subnucleonic-fluctuations-driven eccentricities e{2,3} but are inconsistent with the notion of shape engineering in p/d/3He+Au collisions. The scaling function derived from the measurements, confirm the important role of final-state effects across a broad spectrum of collision-system sizes and energies and suggests an increase in eta/s(T,muB) for small collision-systems.

   nucl-exhep-exhep-phnucl-thNPA(2021)·14 citations
3. 03*

   Directed and elliptic flow of identified hadrons, high-$p_{\mathrm{T}}$ charged hadrons and light nuclei in Au+Au collisions at STAR

   Kishora Nayak (for the STAR Collaboration)🇨🇳

   In this proceeding, we present the new precise directed flow $v_1$, measurement of $\pi$, $K$, $p$ and $\varphi$ in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 27, 54.4 GeV and deuteron at $\sqrt{s_{\mathrm{NN}}}$ = 7.7, 11.5, 14.5 and 19.6 GeV. The first measurement of pseudorapidity and centrality dependence of the $v_1$ of high-$p_T$ ($>$5 GeV/$c$) charged hadrons in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV are reported. The elliptic flow $v_2$, of identified hadrons ($\pi$, $K$, $p$, $\varphi$, $K_S^0$, $\Lambda$, $\Xi$, $\Omega$) in Au+Au collisions at $\sqrt{s_{\mathrm{NN}}}$ = 54.4 GeV are also presented. The results are compared with model calculations to discuss the physics implications.

   nucl-exhep-exNPA(2021)·6 citations
4. 04*

   Feasibility studies of conserved charge fluctuations in Au-Au collisions with CBM

   Subhasis Samanta (for the CBM Collaboration)🇮🇳

   We present the CBM physics performance study for measurements of the higher order cumulants of the net-proton multiplicity distributions. These observables are proxy for net-baryon fluctuations and are commonly used to study the phase structure of QCD phase diagram. The simulation is done for $Au+Au$ collision at beam kinetic energy $E_{lab}=10$ AGeV. The cumulants of net-proton distributions have been calculated at midrapidity ($|\Delta y|=1$) for the transverse momentum range $0.2<p_T<2.0$ GeV/c. The centrality dependence of cumulants of net-proton upto order four is presented. The efficiency and detector effects are corrected using unfolding techniques. This work shows that the higher order cumulants of net-proton can be measured using the CBM detector.

   nucl-exNPA(2021)·1 citation
5. 05*

   Local spin polarizations in relativistic heavy ion collisions

   Shuai Y. F. Liu🇺🇸 · Yifeng Sun🇮🇹 · Che Ming Ko🇺🇸

   Based on a generalized side-jump formalism for massless chiral fermions, which naturally takes into account the spin-orbit coupling in the scattering of two chiral fermions and the chiral vortical effect in a rotating chiral fermion matter, we have developed a covariant and total angular momentum conserved chiral transport model to study both the global and local polarizations of this matter. For a system of massless quarks of random spin orientations and finite vorticity in a box, we have demonstrated that the model can exactly conserve the total angular momentum of the system and dynamically generate the quark spin polarization expected from a thermally equilibrated quark matter. Using this model to study the spin polarization in relativistic heavy-ion collision, we have found that the local quark spin polarizations depend strongly on the reference frame where they are evaluated as a result of the nontrivial axial charge distribution caused by the chiral vortical effect. We have further shown that because of the anomalous orbital or side-jump contribution to the quark spin polarization, the local quark polarizations calculated in the medium rest frame are qualitatively consistent with the local polarizations of Lambda hyperons measured in experiments.

   ↳ nucl-thhep-phnucl-exNPA(2021)·3 citations
6. 06*

   New developments in lattice QCD on equilibrium physics and phase diagram

   Heng-Tong Ding🇨🇳

   I review recent new lattice QCD results on a few selected topics which are relevant to the heavy ion physics community. Special emphasis is put on the QCD phase diagram towards the chiral limit and at nonzero baryon density as well as the fate of quarkonia and heavy quark drag coefficients.

   ↳ hep-lathep-phnucl-exnucl-thNPA(2021)·38 citations
7. 07*

   Hydrodynamic response to jets with a source based on causal diffusion

   Y. Tachibana🇺🇸 · A. Angerami🇺🇸 · S. A. Bass🇺🇸 · S. Cao🇺🇸 · Y. Chen🇨🇳 · J. Coleman🇺🇸 · L. Cunqueiro🇺🇸 · T. Dai🇺🇸 · L. Du🇺🇸 · R. Ehlers🇺🇸 · H. Elfner🇩🇪 · D. Everett🇺🇸 and 38 other authors

   We study the medium response to jet evolution in the quark-gluon plasma within the JETSCAPE framework. Recoil partons' medium response in the weakly coupled description is implemented in the multi-stage jet energy-loss model in the framework. As a further extension, the hydrodynamic description is rearranged to include in-medium jet transport based on a strong-coupling picture. To interface hydrodynamics with jet energy-loss models, the hydrodynamic source term is modeled by a causal formulation employing the relativistic diffusion equation. The jet shape and fragmentation function are studied via realistic simulations with weakly coupled recoils. We also demonstrate modifications in the medium caused by the hydrodynamic response.

   ↳ nucl-thhep-phnucl-exNPA(2021)·21 citations
8. 08*

   $\beta$ decay of even-A nuclei within the interacting boson model based on nuclear density functional theory

   K. Nomura🇭🇷 · R. Rodríguez-Guzmán🇰🇼 · L. M. Robledo🇪🇸

   We compute the $\beta$-decay $ft$-values within the frameworks of the energy density functional (EDF) and the interacting boson model (IBM). Based on the constrained mean-field calculation with the Gogny-D1M EDF, the IBM Hamiltonian for an even-even nucleus and essential ingredients of the interacting boson-fermion-fermion model (IBFFM) for describing the neighboring odd-odd nucleus are determined in a microscopic way. Only the boson-fermion and residual neutron-proton interaction strengths are determined empirically. The Gamow-Teller (GT) and Fermi (F) transition rates needed to compute the $\beta$-decay $ft$-values are obtained without any additional parameter or quenching of the $g_A$ factor. The observed $\text{ft}$ values for the ${\beta }^{+}$ decays of the even-even Ba into odd-odd Cs nuclei, and of the odd-odd Cs to the even-even Xe nuclei, with mass $A\approx 130$ are reasonably well described. The predicted GT and F transition rates represent a sensitive test of the quality of the IBM and IBFFM wave functions.

   ↳ nucl-thnucl-exPRC(2020)·19 citations
9. 09*

   Production of Quasi-Stellar Neutron Field at Explosive Stellar Temperatures

   Moshe Friedman🇺🇸

   Neutron-induced reactions on unstable isotopes play a key role in the nucleosynthesis $i$--, $r$--, $p$--, $rp$-- and $\nu p$--processes occurring in astrophysical scenarios. While direct cross section measurements are possible for long-living unstable isotopes using the neutron Time-of-Flight method, the currently available neutron intensities ($\approx 10^6$ n/s) require large samples which are not feasible for shorter lifetime isotopes. For the last four decades, the ${}^7$Li$(p,n)$ reaction has been used to provide a neutron field at a stellar temperature of $\approx$ 0.3 GK with significantly higher intensity, allowing the successful measurement of many cross sections along the $s$-process path. In this paper we describe a novel method to use this reaction to produce neutron fields at temperatures of $\approx$ 1.5-3.5 GK, relevant to scenarios such as convective shell C/Ne burning, explosive Ne/C burning, and core-collapse supernovae. This method will allow direct cross section measurements of many important reactions at explosive temperatures, such as ${}^{26}$Al$(n,p)$, ${}^{75}$Se$(n,p)$ and ${}^{56}$Ni$(n,p)$.

   ↳ physics.ins-detnucl-exEPJA(2020)·3 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.