Tue·Nov 30, 2021Tuesday·November 30, 2021

1. 01*

   Cross-sections of photoneutron reactions on ${}^{181}$Ta at $e_{\gamma \max }$ up to 95 MeV

   O.S. Deiev🇺🇦 · I.S. Timchenko🇺🇦 · S.N. Olejnik🇺🇦 · V.A. Kushnir🇺🇦 · V.V. Mytrochenko🇺🇦 · S.A. Perezhogin🇺🇦

   The total bremsstrahlung flux-averaged cross-sections $⟨\sigma (E_{\gamma \max })⟩$ for the photonuclear reactions ${}^{181}\mathrm{Ta}(\gamma ,\text{x}\mathrm{n};\text{x}\le 8{)}^{181-\text{x}}\mathrm{Ta}$ have been measured in the range of end-point energies $E_{\gamma \max }$ up to 95 MeV. The experiments were performed with the beam from the NSC KIPT electron linear accelerator LUE-40 with the use of the activation and off-line $\gamma$-ray spectrometric technique. The calculation of average cross-sections was carried out using the cross-section values computed with the TALYS1.95 code for different level density models $LD$ 1-6. A comparison between the experimental total cross-sections $⟨\sigma (E_{\gamma \max })⟩$ and the theoretical values has shown satisfactory agreement for the ${}^{181}\mathrm{Ta}(\gamma ,\text{x}\mathrm{n})$ reactions with the escape of 1-4, 6 and 7 neutrons. The closest agreement with the measured data is observed with the $LD$5 computation version, which represents the microscopic level density model taking into account Hilaire's combinatorial tables.

   nucl-exPRC(2022)·16 citations
2. 02*

   Precise measurement of differential cross sections of the {\Sigma}-p --> {\Lambda} n reaction in momentum range 470-650 MeV/c

   J-PARC E40 Collaboration: K. Miwa🇯🇵 · J. K. Ahn🇰🇷 · Y. Akazawa🇯🇵 · T. Aramaki🇯🇵 · S. Ashikaga🇯🇵 · S. Callier🇫🇷 · N. Chiga🇯🇵 · S. W. Choi🇯🇵 · H. Ekawa🇯🇵 · P. Evtoukhovitch🇷🇺 · N. Fujioka🇯🇵 · M. Fujita🇯🇵 and 59 other authors

   The differential cross sections of the {\Sigma}-p --> {\Lambda} n reaction were measured accurately for the {\Sigma}- momentum (p_{{\Sigma}}) ranging from 470 to 650 MeV/c at the J-PARC Hadron Experimental Facility. Precise angular information about the {\Sigma}-p --> {\Lambda} n reaction was obtained for the first time by detecting approximately 100 reaction events at each angular step of {\Delta}cos{\theta} = 0.1. The obtained differential cross sections show slightly forward-peaking structure in the measured momentum regions.The cross sections integrated for -0.7 < cos{\theta} < 1.0 were obtained as 22.5 +- 0.68 (stat.) +- 0.65 (syst.) mb and 15.8 +-0.83(stat.) +- 0.52 (syst.) mb for 470<p_{{\Sigma}}(MeV/c)<550 and 550<p_{{\Sigma}}(MeV/c)<650, respectively. These results show a drastic improvement compared to past measurements of the hyperon-proton scattering experiments. They will play essential roles in updating the theoretical models of the baryon-baryon interactions.

   nucl-exnucl-thPRL(2022)·53 citations
3. 03*

   Narrow resonances in the continuum of the unbound nucleus ${}^{15}$F

   V. Girard-Alcindor (1 and 2) · A. Mercenne (3) · I. Stefan (2) · F. de Oliveira Santos (1) · N. Michel (4) · M. Płoszajczak (1) · M. Assié (2) · A. Lemasson (1) · E. Clément (1) · F. Flavigny (5) · A. Matta (5) · D. Ramos (1) and 91 other authors

   The structure of the unbound ${}^{15}$F nucleus is investigated using the inverse kinematics resonant scattering of a radioactive ${}^{14}$O beam impinging on a CH${}_2$ target. The analysis of ${}^1$H(${}^{14}$O,p)${}^{14}$O and ${}^1$H(${}^{14}$O,2p)${}^{13}$N reactions allowed the confirmation of the previously observed narrow $1/2^{-}$ resonance, near the two-proton decay threshold, and the identification of two new narrow 5/2${}^{-}$ and 3/2${}^{-}$ resonances. The newly observed levels decay by 1p emission to the ground of ${}^{14}$O, and by sequential 2p emission to the ground state (g.s.) of ${}^{13}$N via the $1^{-}$ resonance of ${}^{14}$O. Gamow shell model (GSM) analysis of the experimental data suggests that the wave functions of the 5/2${}^{-}$ and 3/2${}^{-}$ resonances may be collectivized by the continuum coupling to nearby 2p- and 1p- decay channels. The observed excitation function ${}^1$H(${}^{14}$O,p)${}^{14}$O and resonance spectrum in ${}^{15}$F are well reproduced in the unified framework of the GSM.

   nucl-exnucl-thPRC(2022)·19 citations
4. 04*

   Evidence of Mass Ordering of Charm and Bottom Quark Energy Loss in Au+Au Collisions at RHIC

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

   Partons traversing the strongly interacting medium produced in heavy-ion collisions are expected to lose energy depending on their color charge and mass. We measure the nuclear modification factors for charm- and bottom-decay electrons, defined as the ratio of yields, scaled by the number of binary nucleon-nucleon collisions, in $\sqrt{s_{\mathrm{NN}}}$ = 200 GeV Au+Au collisions to $p$+$p$ collisions ($R_{\mathrm{AA}}$), or in central to peripheral Au+Au collisions ($R_{\mathrm{CP}}$). We find the bottom-decay electron $R_{\mathrm{AA}}$ and $R_{\mathrm{CP}}$ to be significantly higher than that of charm-decay electrons. Model calculations including mass-dependent parton energy loss in a strongly coupled medium are consistent with the measured data. These observations provide clear evidence of mass ordering of charm and bottom quark energy loss when traversing through the strongly coupled medium created in heavy-ion collisions.

   nucl-exEPJC(2022)·28 citations
5. 05*

   Hidden charm mesons in nuclear matter and nuclei

   J.J. Cobos-Martínez🇲🇽 · K. Tsushima🇧🇷 · G. Krein🇧🇷 · A.W. Thomas🇦🇺

   Recent results for the ${\eta }_c$- and $J/\psi$-nucleus bound state energies for various nuclei are presented. The attractive potentials for the ${\eta }_c$ and $J/\psi$ mesons in the nuclear medium originate, respectively, from the in-medium enhanced $D{D}^{\ast }$ and $D\bar{D}$ loops in the ${\eta }_c$ and $J/\psi$ self energies. Our results suggest that the ${\eta }_c$ and $J/\psi$ mesons should form bound states with all the nuclei considered.

   ↳ nucl-thhep-exhep-phnucl-exPoS(2022)·2 citations
6. 06*

   Semi-analytical calculation of the trajectory of relativistic nuclear collisions in the QCD phase diagram

   Todd Mendenhall🇺🇸 · Zi-Wei Lin🇺🇸

   We extend a semi-analytical model that includes the finite nuclear thickness to calculate the energy density $ϵ(t)$ and conserved-charge densities including the net-baryon density $n_{{}_{\mathrm{B}}}(t)$ produced at mid-spacetime-rapidity in central Au+Au collisions. Assuming the formation of a quark-gluon plasma with an ideal gas equation of state of either quantum or Boltzmann statistics or with a lattice QCD-based equation of state, we extract the temperature $T$ and chemical potentials ${\mu }_{{}_{\mathrm{B}}}$, ${\mu }_{{}_{\mathrm{Q}}}$ and ${\mu }_{{}_{\mathrm{S}}}$ as functions of time. This then allows us to semi-analytically calculate the $T-{\mu }_{{}_{\mathrm{B}}}$ trajectory of relativistic nuclear collisions in the QCD phase diagram, which should benefit the studies of high density physics including the search for the critical end point. This model is also useful for exploring the trajectories in the more general $T-{\mu }_{{}_{\mathrm{B}}}-{\mu }_{{}_{\mathrm{Q}}}-{\mu }_{{}_{\mathrm{S}}}$ QCD phase space.

   ↳ nucl-thnucl-exPRC(2023)·6 citations
7. 07*

   Momentum dependence of near-threshold photoproduction of ${\Xi }^{-}$ hyperons off nuclei and their properties in the nuclear medium

   E. Ya. Paryev🇷🇺

   We study the near-threshold inclusive photoproduction of ${\Xi }^{-}$ hyperons off ${}^{12}$C and ${}^{184}$W target nuclei within a first-collision model relying on the nuclear spectral function and including incoherent ${\Xi }^{-}$ production in direct elementary $\gamma p\to K^{+}{K}^{+}{\Xi }^{-}$ and $\gamma n\to K^{+}{K}^0{\Xi }^{-}$ processes. The model takes into account the impact of the nuclear effective scalar $K^{+}$, $K^0$, ${\Xi }^{-}$ and their Coulomb potentials on these processes as well as the absorption of final ${\Xi }^{-}$ hyperons in nuclear matter, the binding of intranuclear nucleons and their Fermi motion. We calculate the absolute differential cross sections and their ratios for the production of ${\Xi }^{-}$ hyperons off these nuclei at laboratory polar angles $\le$ 45${}^{\circ }$ by photons with energies of 2.5 and 3.0 GeV, with and without imposing the phase space constraints on the ${\Xi }^{-}$ emission angle in the respective $\gamma p$ center-of-mass system. We also calculate the momentum dependence of the transparency ratio for ${\Xi }^{-}$ hyperons for the ${}^{184}$W/${}^{12}$C combination at these photon energies. We show that the ${\Xi }^{-}$ momentum distributions (absolute and relative) at the adopted initial photon energies possess, contrary to the transparency ratio for ${\Xi }^{-}$ hyperons, a definite sensitivity to the considered changes in the scalar ${\Xi }^{-}$ nuclear mean-field potential at saturation density ${\rho }_0$ in the low-momentum range of 0.1--0.8 GeV/c. Therefore, the precise measurements of these distributions in a dedicated experiment at the CEBAF facility will provide valuable information on the ${\Xi }^{-}$ in-medium properties, which will be supplementary to that inferred from studying of the ($K^{-}$,$K^{+}$) reactions at initial momenta of 1.6--1.8 GeV/c.

   ↳ nucl-thhep-phnucl-exNPA(2022)·2 citations
8. 08*

   Far from equilibrium Chiral Magnetic Effect in Strong Magnetic Fields from Holography

   Sebastian Grieninger🇪🇸 · Sergio Morales-Tejera🇪🇸

   We study the real time evolution of the chiral magnetic effect out-of-equilibrium in strongly coupled anomalous field theories. We match the parameters of our model to QCD parameters and draw lessons of possible relevance for the realization of the chiral magnetic effect in heavy ion collisions. In particular, we find an equilibration time of about $\sim 0.35$ fm/c in presence of the chiral anomaly for plasma temperatures of order $T\sim 300-400$ MeV.

   ↳ hep-phhep-thnucl-exnucl-thEPJ Web Conf.(2022)·3 citations
9. 09*

   The information content of jet quenching and machine learning assisted observable design

   Yue Shi Lai🇺🇸 · James Mulligan🇺🇸 · Mateusz Płoskoń🇺🇸 · Felix Ringer🇺🇸

   Jets produced in high-energy heavy-ion collisions are modified compared to those in proton-proton collisions due to their interaction with the deconfined, strongly-coupled quark-gluon plasma (QGP). In this work, we employ machine learning techniques to identify important features that distinguish jets produced in heavy-ion collisions from jets produced in proton-proton collisions. We formulate the problem using binary classification and focus on leveraging machine learning in ways that inform theoretical calculations of jet modification: (i) we quantify the information content in terms of Infrared Collinear (IRC)-safety and in terms of hard vs. soft emissions, (ii) we identify optimally discriminating observables that are in principle calculable in perturbative QCD, and (iii) we assess the information loss due to the heavy-ion underlying event and background subtraction algorithms. We illustrate our methodology using Monte Carlo event generators, where we find that important information about jet quenching is contained not only in hard splittings but also in soft emissions and IRC-unsafe physics inside the jet. This information appears to be significantly reduced by the presence of the underlying event. We discuss the implications of this for the prospect of using jet quenching to extract properties of the QGP. Since the training labels are exactly known, this methodology can be used directly on experimental data without reliance on modeling. We outline a proposal for how such an experimental analysis can be carried out, and how it can guide future measurements.

   ↳ hep-phhep-exnucl-exnucl-thJHEP(2022)·29 citations
10. 10*

    Probing nuclear structure with mean transverse momentum in relativistic isobar collisions

    Hao-jie Xu🇨🇳 · Wenbin Zhao🇺🇸 · Hanlin Li🇨🇳 · Ying Zhou🇨🇳 · Lie-Wen Chen🇨🇳 · Fuqiang Wang🇺🇸

    Transverse momentum ($p_T$) generation in relativistic heavy ion collisions is sensitive to the initial geometry and the final-state bulk evolution. We demonstrate with hydrodynamic calculations that the mean $p_T$ ratio ($R_{⟨p_T⟩}$) between the highly similar isobar ${}_{44}^{96}$Ru+${}_{44}^{96}$Ru and ${}_{40}^{96}$Zr+${}_{40}^{96}$Zr collisions is insensitive to the bulk evolution and remains sensitive to the small difference in the initial nuclear structure (neutron skin and deformation) between the Ru and Zr nuclei.We further find that nuclear deformation can produce an anticorrelation between $R_{⟨p_T⟩}$ and eccentricity (or elliptic flow) in central collisions. These findings suggest that the $R_{⟨p_T⟩}$ between the isobar systems can be used to measure the neutron skin thickness and deformation parameters, which can in turn constrain the nuclear symmetry energy slope parameter.

    ↳ nucl-thnucl-exPRC(2023)·80 citations
11. 11*

    Beyond-mean-field calculations of allowed and first-forbidden ${\beta }^{-}$ decays of $r$-process waiting-point nuclei

    Caroline Robin🇩🇪 · Elena Litvinova🇺🇸 · Gabriel Martínez-Pinedo🇩🇪

    $\beta$-decay rates of neutron-rich nuclei, in particular those located at neutron shell closures, play a central role in simulations of the heavy-element nucleosynthesis and resulting abundance distributions. We present $\beta$-decay half-lives of even-even $N=82$ and $N=126$ $r$-process waiting-point nuclei calculated in the approach based on relativistic quasiparticle random phase approximation with quasiparticle-vibration coupling. The calculations include both allowed and first-forbidden transitions. In the $N=82$ chain, the quasiparticle-vibration coupling has an important impact close to stability, as it increases the contribution of Gamow-Teller modes and improves the agreement with the available data. In the $N=126$ chain, we find the decay to proceed dominantly via first-forbidden transitions, even when the coupling to vibrations is included.

    ↳ nucl-thnucl-exEPJ Web Conf.(2022)·2 citations
12. 12*

    Online Bayesian Optimization for Beam Alignment in the SECAR Recoil Mass Separator

    Sara A. Miskovich · Fernando Montes🇺🇸 · Georg P. A. Berg🇺🇸 · Jeff Blackmon · Kelly A. Chipps🇺🇸 · Manoel Couder🇺🇸 · Kirby Hermansen · Ashley A. Hood🇺🇸 · Rahul Jain🇮🇳 · Hendrik Schatz🇺🇸 · Michael S. Smith · Pelagia Tsintari · Louis Wagner🇺🇸

    The SEparator for CApture Reactions (SECAR) is a next-generation recoil separator system at the Facility for Rare Isotope Beams (FRIB) designed for the direct measurement of capture reactions on unstable nuclei in inverse kinematics. To maximize the performance of the device, careful beam alignment to the central ion optical axis needs to be achieved. This can be difficult to attain through manual tuning by human operators without potentially leaving the system in a sub-optimal and irreproducible state. In this work, we present the first development of online Bayesian optimization with a Gaussian process model to tune an ion beam through a nuclear astrophysics recoil separator. We show that the method achieves small incoming angular deviations (0-1 mrad) in an efficient and reproducible manner that is at least 3 times faster than standard hand-tuning. This method is now routinely used for all separator tuning.

    ↳ physics.ins-detnucl-ex1 citation

* 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.