Wed·Mar 8, 2023Wednesday·March 8, 2023

1. 01*

   Elliptic Flow of Heavy-Flavor Decay Electrons in Au+Au Collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}$ = 27 and 54.4 GeV at RHIC

   STAR Collaboration: M. I. Abdulhamid · B. E. Aboona · J. Adam · L. Adamczyk · J. R. Adams · I. Aggarwal · M. M. Aggarwal · Z. Ahammed · D. M. Anderson · E. C. Aschenauer · S. Aslam · J. Atchison and 362 other authors

   We report on new measurements of elliptic flow ($v_2$) of electrons from heavy-flavor hadron decays at mid-rapidity ($|y|<0.8$) in Au+Au collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}$ = 27 and 54.4 GeV from the STAR experiment. Heavy-flavor decay electrons ($e^{\mathrm{HF}}$) in Au+Au collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}$ = 54.4 GeV exhibit a non-zero $v_2$ in the transverse momentum ($p_{\mathrm{T}}$) region of $p_{\mathrm{T}}<$ 2 GeV/$c$ with the magnitude comparable to that at $\sqrt{s_{{}_{\mathrm{NN}}}}=200$ GeV. The measured $e^{\mathrm{HF}}$ $v_2$ at 54.4 GeV is also consistent with the expectation of their parent charm hadron $v_2$ following number-of-constituent-quark scaling as other light and strange flavor hadrons at this energy. These suggest that charm quarks gain significant collectivity through the evolution of the QCD medium and may reach local thermal equilibrium in Au+Au collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=54.4$ GeV. The measured $e^{\mathrm{HF}}$ $v_2$ in Au+Au collisions at $\sqrt{s_{{}_{\mathrm{NN}}}}=$ 27 GeV is consistent with zero within large uncertainties. The energy dependence of $v_2$ for different flavor particles ($\pi ,\varphi ,D^0/e^{\mathrm{HF}}$) shows an indication of quark mass hierarchy in reaching thermalization in high-energy nuclear collisions.

   nucl-exhep-exPLB(2023)·6 citations
2. 02*

   Spin-parities of sub-threshold resonances in the ${}^{18}$F(p, $\alpha$)${}^{15}$O reaction

   F. Portillo · R. Longland🇺🇸 · A. L. Cooper · S. Hunt · A. M. Laird🇬🇧 · C. Marshall🇺🇸 · K. Setoodehnia🇺🇸

   The ${}^{18}$F(p, $\alpha$)${}^{15}$O reaction is key to determining the ${}^{18}$F abundance in classical novae. However, the cross section for this reaction has large uncertainties at low energies largely caused by interference effects. Here, we resolve a longstanding issue with unknown spin-parities of sub-threshold states in ${}^{19}$Ne that reduces these uncertainties. The ${}^{20}$Ne(${}^3$He, ${}^4$He)${}^{19}$Ne neutron pick-up reaction was used to populate ${}^{19}$Ne excited states, focusing on the energy region of astrophysical interest ($\approx$ 6 - 7 MeV). The experiment was performed at the Triangle Universities Nuclear Laboratory using the high resolution Enge split-pole magnetic spectrograph. Spins and parities were found for states in the astrophysical energy range. In particular, the state at 6.133 MeV (E${}_r^{\text{c.m.}}=-278$ keV) was found to have spin and parity of $3/2^{+}$ and we confirm the existence of an unresolved doublet close to 6.288 MeV (E${}_r^{\text{c.m.}}=-120$ keV) with J${}^{\pi }$ = $1/2^{+}$ and a high-spin state. Using these results, we demonstrate a significant factor of two decrease in the reaction rate uncertainties at nova temperatures.

   nucl-exPRC(2023)·5 citations
3. 03*

   Search for jet quenching effects on the plain jet mass in Pb+Pb collisions at the LHC with a multiphase transport model

   Xiang-Pan Duan🇨🇳 · Guo-Liang Ma🇨🇳

   The plain jet mass distributions of reconstructed jets are investigated in p+p and 0-10$\%$ most central Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76\mathrm{TeV}$ using a dynamical multiphase transport model with a string melting mechanism. It is observed that the mean charged jet mass increases with increasing jet transverse momentum and jet radius in central Pb+Pb collisions. It is demonstrated that the plain jet mass of reconstructed partonic jet is shifted to a higher value after the evolution of partonic stage due to jet quenching in central Pb+Pb collisions. However, the jet mass shift effect is strongly weakened by non-perturbative effects from hadronization and hadron rescatterings. This makes it difficult to observe significant hot medium modification effects on the plain jet mass distribution in the final state of relativistic heavy-ion collisions.

   ↳ nucl-thhep-phnucl-exEPJA(2023)·3 citations
4. 04*

   The Neutron Mean Life and Big Bang Nucleosynthesis

   Tsung-Han Yeh🇨🇦 · Keith A. Olive🇺🇸 · Brian D. Fields🇺🇸

   We explore the effect of neutron lifetime and its uncertainty on standard big-bang nucleosynthesis (BBN). BBN describes the cosmic production of the light nuclides ${}^1\mathrm{H}$, $\mathrm{D}$, ${}^3\mathrm{H}$+${}^3\mathrm{He}$, ${}^4\mathrm{He}$, and ${}^7\mathrm{Li}$+${}^7\mathrm{Be}$ in the first minutes of cosmic time. The neutron mean life ${\tau }_n$ has two roles in modern BBN calculations: (1) it normalizes the matrix element for weak $n\leftrightarrow p$ interconversions, and (2) it sets the rate of free neutron decay after the weak interactions freeze out. We review the history of the interplay between ${\tau }_n$ measurements and BBN, and present a study of the sensitivity of the light element abundances to the modern neutron lifetime measurements. We find that ${\tau }_n$ uncertainties dominate the predicted ${}^4\mathrm{He}$ error budget, but these theory errors remain smaller than the uncertainties in ${}^4\mathrm{He}$ observations, even with the dispersion in recent neutron lifetime measurements. For the other light-element predictions, ${\tau }_n$ contributes negligibly to their error budget. Turning the problem around, we combine present BBN and cosmic microwave background (CMB) determinations of the cosmic baryon density to $\text{predict}$ a "cosmologically preferred" mean life of ${\tau }_n(\mathrm{BBN}+\mathrm{CMB})=870\pm 16\sec$, which is consistent with experimental mean life determinations. We go on to show that if future astronomical and cosmological helium observations can reach an uncertainty of ${\sigma }_{\mathrm{obs}}(Y_p)=0.001$ in the ${}^4\mathrm{He}$ mass fraction $Y_p$, this could begin to discriminate between the mean life determinations.

   ↳ astro-ph.COhep-phnucl-exnucl-thUniverse(2023)·14 citations
5. 05*

   Neutrinoless double-beta decay in the neutrino-extended Standard Model

   Wouter Dekens🇺🇸 · Jordy de Vries🇳🇱 · Emanuele Mereghetti🇺🇸 · Javier Menéndez🇪🇸 · Pablo Soriano🇪🇸 · Guanghui Zhou🇳🇱

   We investigate neutrinoless double-beta decay ($0\nu \beta \beta$) in the minimal extension of the standard model of particle physics, the $\nu$SM, where gauge-singlet right-handed neutrinos give rise to Dirac and Majorana neutrino mass terms. We focus on the associated sterile neutrinos and argue that the usual evaluation of their contributions to $0\nu \beta \beta$, based on mass-dependent nuclear matrix elements, is missing important contributions from neutrinos with ultrasoft and hard momenta. We identify the hadronic and nuclear matrix elements that enter the new contributions, and calculate all relevant nuclear matrix elements for ${}^{136}$Xe using the nuclear shell model. Finally, we illustrate the impact on $0\nu \beta \beta$ rates in specific neutrino mass models and show that the new contributions significantly alter the $0\nu \beta \beta$ rate in most parts of the $\nu$SM parameter space.

   ↳ hep-phhep-exnucl-exnucl-thPRC(2023)·37 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.