Tue·Apr 7, 2020Tuesday·April 7, 2020

1. 01*

   Electromagnetic & Weak Probes: Experimental Overview

   Frank Geurts🇺🇸

   Electromagnetic and electroweak probes are the most versatile probes in the study of heavy-ion collisions. Produced at every stage in the evolution of QCD matter, its messengers are practically inert to the strongly interacting medium they travel through. In this contribution, I will discuss a selection of new results from experiments at the LHC, RHIC, and SIS facilities, spanning almost four orders of magnitude in beam energy. I will conclude with a brief overview of the experimental landscape in the near future.

   nucl-exhep-exNPA(2021)·2 citations
2. 02*

   Structure effects on the giant monopole resonance and determinations of the nuclear incompressibility

   K. B. Howard🇺🇸

   Giant resonances are collective nuclear vibrations which provide a unique laboratory setting to probe the bulk properties of the nuclear force. One of the isoscalar compressional modes -- the isoscalar giant monopole resonance (ISGMR) -- is useful in constraining the equation of state (EoS) of nuclear matter. For example, the nuclear incompressibility, $K_{\infty }$, is a fundamental quantity in the EoS and is directly correlated with the energies of the ISGMR in finite nuclei. Previous work has shown that interactions with $K_{\infty }$ which reproduce the energies of the ISGMR in ${}^{208}$Pb and ${}^{90}$Zr well, overestimate those of the tin and cadmium nuclei. To further investigate where this "softness" appears in moving away from the doubly-closed nucleus ${}^{90}$Zr, and how this effect develops, the first portion of this thesis consists of measurements of the ISGMR in the molybdenum isotopes. Comparison of the ISGMR strengths with Random Phase Approximation calculations shows that these nuclei have ISGMR energies which are overestimated to a similar degree as seen in the tin and cadmium nuclei, while the strength of ${}^{208}$Pb is precisely reproduced. This suggests clearly that the molybdenum nuclei exhibit the same open-shell softness which has been documented previously. The ISGMR in isotopes encompassing a broad range of proton-neutron asymmetries constrains the dependence of the nuclear incompressibility on the isospin asymmetry, as quantified by the asymmetry term, $K_{\tau }$. To reconcile previously-published and highly concerning conclusions that $K_{\tau }=+582$ MeV, the second portion of this thesis is focused upon independently studying this claim. A simultaneous measurement of the ISGMR in ${}^{40,42,44,48}$Ca has excluded the possibility of a positive value for $K_{\tau }$, and found consistency with previous data, placing $K_{\tau }$ at $-510\pm 115$ MeV.

   nucl-ex8 citations
3. 03*

   Yield ratio of hypertriton to light nuclei in heavy-ion collisions from $\sqrt{{\mathrm{s}}_{\mathrm{NN}}}$ = 4.9 GeV to 2.76 TeV

   Tianhao Shao🇨🇳 · Jinhui Chen🇨🇳 · Che Ming Ko🇺🇸 · Kai-Jia Sun🇺🇸 · Zhangbu Xu🇺🇸

   We resolve the difference in the yield ratio ${\mathrm{S}}_3$ = $\frac{{\mathrm{N}}_{{}_{\mathrm{\Lambda }}^3\mathrm{H}}/{\mathrm{N}}_{\mathrm{\Lambda }}}{{\mathrm{N}}_{{}^3\mathrm{He}}/{\mathrm{N}}_{\mathrm{p}}}$ measured in Au+Au collisions at $\sqrt{{\mathrm{s}}_{\mathrm{NN}}}$ = 200 GeV and in Pb-Pb collisions at $\sqrt{{\mathrm{s}}_{\mathrm{NN}}}$ = 2.76 TeV by adopting a different treatment of the weak decay contribution to the proton yield in Au+Au collisions at $\sqrt{{\mathrm{s}}_{\mathrm{NN}}}$ = 200 GeV. We then use the coalescence model to extract information on the $\Lambda$ and nucleon density fluctuations at the kinetic freeze-out of heavy ion collisions. We also show from available experimental data that the yield ratio ${\mathrm{S}}_2$ = $\frac{{\mathrm{N}}_{{}_{\mathrm{\Lambda }}^3\mathrm{H}}}{{\mathrm{N}}_{\mathrm{\Lambda }}{\mathrm{N}}_{\mathrm{d}}}$ is a more promising observable than ${\mathrm{S}}_3$ for probing the local baryon-strangeness correlation in the produced medium.

   nucl-exnucl-thCPC(2020)·16 citations
4. 04*

   Branching ratio of the super-allowed beta decay of 10C

   B. Blank🇫🇷 · M. Aouadi🇫🇷 · P. Ascher🇫🇷 · M. Gerbaux🇫🇷 · J. Giovinazzo🇫🇷 · S. Grevy🇫🇷 · T. Kurtukian Nieto🇫🇷 · M.R. Dunlop🇨🇦 · R. Dunlop🇨🇦 · A.T. Laffoley🇨🇦 · G.F. Grinyer🇨🇦 · P. Finlay🇧🇪

   In an experiment performed at the ISOLDE facility of CERN, the super-allowed beta-decay branching ratio of 10C was determined with a high-precision single-crystal germanium detector. In order to evaluate the contribution of the pile-up of two 511 keV gamma quanta to one of the gamma-ray peaks of interest at 1021.7 keV, data were not only taken with 10C, but also with a 19Ne beam. The final result for the super-allowed decay branch is 1.4638(50)%, in agreement with the average from literature.

   nucl-exEPJA(2020)·5 citations
5. 05*

   Measurement of differential cross sections for deuteron-proton breakup reaction at 160 MeV

   W. Parol🇵🇱 · A. Kozela🇵🇱 · K. Bodek🇵🇱 · A. Deltuva🇱🇹 · M. Eslami-Kalantari🇮🇷 · J. Golak🇵🇱 · N. Kalantar-Nayestanaki🇳🇱 · G. Khatri🇨🇭 · St. Kistryn🇵🇱 · B. Kłos🇵🇱 · J. Kuboś🇵🇱 · P. Kulessa🇵🇱 and 15 other authors

   Differential cross sections for deuteron breakup ${}^{1}H(d,pp)n$ reaction were measured for a large set of 243 geometrical configurations at the beam energy of 80 MeV/nucleon. The cross section data are normalized by the luminosity factor obtained on the basis of simultaneous measurement of elastic scattering channel and the existing cross section data for this process. The results are compared to the theoretical calculations modeling nuclear interaction with and without taking into account the three-nucleon force (3NF) and Coulomb interaction. In the validated region of the phase space both the Coulomb force and 3NF play an important role in a good description of the data. There are also regions, where the improvements of description due to including 3NF are not sufficient.

   nucl-exPRC(2020)·11 citations
6. 06*

   First limits on double beta decays in ${}^{232}$Th

   M. Laubenstein🇮🇹 · B. Lehnert🇺🇸 · S. S. Nagorny🇨🇦

   As one of the primordial radioactive isotopes, ${}^{232}$Th mainly undergoes $\alpha$-decay with a half-life of $1.402\times 10^{10}$ yr. However, it is also one of 35 double beta decay candidates in which the single $\beta$-decay is forbidden or strongly suppressed. 181 mg of thorium contained in a gas mantle was measured in an HPGe well-detector at the Gran Sasso Underground Laboratory (LNGS) with a total exposure of 3.25 g $\times$ d. We obtain half-life limits on all double beta decay modes of ${}^{232}$Th to excited states of ${}^{232}$U on the order of $10^{11-15}$ yr. For the most likely transition into the $0_1^{+}$ state we find a lower half-life limit of $6.3\times 10^{14}$ yr (90% credibility). These are the first constraints on double beta decay excited state transition in ${}^{232}$Th.

   nucl-exEPJC(2020)·1 citation
7. 07*

   Threshold ${\pi }^{-}$ Photoproduction on the Neutron

   W.J. Briscoe (GWU)🇺🇸 · A.E. Kudryavtsev (ITEP)🇺🇸 · I.I. Strakovsky (GWU)🇺🇸 · V.E. Tarasov (ITEP)🇷🇺 · R.L. Workman (GWU)🇺🇸

   Recent data from the PIONS$@$MAX-lab Collaboration, measuring the total cross section of the pion incoherent photoproduction $\gamma d\to {\pi }^{-}pp$ near threshold, have been used to extract the E${}_{0+}$ multipole and total cross section of the reaction $\gamma n\to {\pi }^{-}p$, also near threshold. These are the first measurements of the reaction $\gamma d\to {\pi }^{-}pp$ in the threshold region. The value of E${}_{0+}$ is extracted through a fit to the deuteron data in a photoproduction model accounting for final-state interactions. The model takes an $S$-wave approximation for the elementary reaction $\gamma n\to {\pi }^{-}p$ with E${}_{0+}=$ const in the threshold region. The obtained value E${}_{0+}=-31.86\pm 0.8$ (in $10^{-3}/m_{{\pi }^{+}}$ units) is in agreement with other existing results. Model predictions for the total cross section $\sigma (\gamma n\to {\pi }^{-}p)$ are also given.

   ↳ nucl-thhep-exhep-phnucl-exEPJA(2020)·16 citations
8. 08*

   Correlation between mean transverse momentum and anisotropic flow in heavy-ion collisions

   Giuliano Giacalone🇫🇷 · Fernando G. Gardim🇧🇷 · Jacquelyn Noronha-Hostler🇺🇸 · Jean-Yves Ollitrault🇫🇷

   The correlation between the mean transverse momentum of outgoing particles, $⟨p_t⟩$, and the magnitude of anisotropic flow, $v_n$, has recently been measured in Pb+Pb collisions at the CERN Large Hadron Collider, as a function of the collision centrality. We confirm the previous observation that event-by-event hydrodynamics predicts a correlation between $v_n$ and $⟨p_t⟩$ that is similar to that measured in data. We show that the magnitude of this correlation can be directly predicted from the initial condition of the hydrodynamic calculation, for $n=2,3$, if one replaces $v_n$ by the corresponding initial-state anisotropy, ${\epsilon }_n$, and $⟨p_t⟩$ by the total energy per unit rapidity of the fluid at the beginning of the hydrodynamic expansion.

   ↳ nucl-thhep-phnucl-exPRC(2021)·86 citations
9. 09*

   Secondary $\gamma$-ray decays from the partial-wave $T$ matrix with an $R$-matrix application to ${}^{15}\mathrm{N}(p,{\alpha }_1\gamma ){}^{12}\mathrm{C}$

   Carl R. Brune🇺🇸 · R. James deBoer🇺🇸

   The secondary $\gamma$ rays emitted following a nuclear reaction are often relatively straightforward to detect experimentally. Despite the large volume of such data, a practical formalism for describing these $\gamma$ rays in terms of partial-wave $T$-matrix elements has never been given. The partial-wave formalism is applicable when $R$-matrix methods are used to describe the reaction in question. This paper supplies the needed framework, and it is demonstrated by the application to the ${}^{15}\mathrm{N}(p,{\alpha }_1\gamma ){}^{12}\mathrm{C}$ reaction.

   ↳ nucl-thnucl-exPRC(2020)·5 citations
10. 10*

    Brief history of the search for critical structures in heavy-ion collisions

    Marek Gazdzicki🇵🇱 · Mark Gorenstein🇺🇦 · Peter Seyboth🇵🇱

    The paper briefly presents history, status, and plans of the search for the critical structures - the onset of fireball, the onset of deconfinement, and the deconfinement critical point - in high energy nucleus-nucleus collisions. First, the basic ideas are introduced, the history of the observation of strongly interacting matter in heavy ion collisions is reviewed, and the path towards the quark-gluon plasma discovery is sketched. Then the status of the search for critical structures is discussed - the discovery of the onset of deconfinement, indications for the onset of fireball, and still inconclusive results concerning the deconfinement critical point. Finally, an attempt to formulate priorities for future measurements - charm quarks vs the onset of deconfinement and detailed study of the onset of fireball - closes the paper.

    ↳ hep-phnucl-exnucl-thActa Phys.Polon.B(2020)·11 citations
11. 11*

    Solitons in nuclear time-dependent density functional theory

    Yoritaka Iwata🇯🇵

    The soliton existence in sub-atomic many-nucleon systems is discussed. In many nucleon dynamics represented by the nuclear time-dependent density functional formalism, much attention is paid to energy and mass dependence of the soliton existence. In conclusion, the existence of nuclear soliton is clarified if the temperature of nuclear system is from 10 to 30 MeV. With respect to the mass dependence ${}^4$He and ${}^{16}$O are suggested to be the candidates for the self-bound states exhibiting the property of nuclear soliton.

    ↳ nucl-thnucl-exFront.Phys.(2020)·1 citation
12. 12*

    Prediction of the analyzing power for $\vec{p}$+${}^6$He elastic scattering at 200 MeV from $\vec{p}$+${}^4$He elastic scattering at 200 MeV

    Masahiro Ishii🇯🇵 · Yasunori Iseri · Masanobu Yahiro🇯🇵

    We apply the cluster-folding (CF) model for $\vec{p}{+}^6$He scattering at 200 MeV, where the potential between $\vec{p}$ and ${}^4$He is fitted to data on $\vec{p}{+}^4$He scattering at 200 MeV. For $\vec{p}{+}^6$He scattering at 200 MeV, the CF model reproduces measured differential cross section with no free parameter, We then predict the analyzing power $A_y(q)$ with the CF model, where $q$ is the transfer momentum. Johnson, Al-Khalili and Tostevin construct a theory for one-neutron halo scattering, taking (1) the adiabatic approximation and (2) neglecting the interaction between a valence neutron and a target, and yield a simple relationship between the elastic scattering of a halo nucleus and of its core under certain conditions. We improve their theory with (3) the eikonal approximation in order to determine $A_y(q)$ for ${}^6$He from the data on $A_y(q)$ for ${}^4$He. The improved theory is accurate, when approximation (1)--(3) are good. Among the three approximations, approximation (2) is most essential. The CF model shows that approximation (2) is good in $0.9<q<2.4$ fm${}^{-1}$. In the improved theory, the $A_y(q)$ for ${}^6$He is the same as that for ${}^4$He. In $0.9<q<2.4$ fm${}^{-1}$, we then predict $A_y(q)$ for $\vec{p}{+}^6$He scattering at 200 MeV from measured $A_y(q)$ for $\vec{p}{+}^4$He scattering at 200 MeV. We thus predict $A_y(q)$ with the model-dependent and the model-independent prescription. The ratio of differential cross sections measured for ${}^6$He to that for ${}^4$He is related to the wave function of ${}^6$He. We then determine the radius between ${}^4$He and the center-of-mass of valence two neutrons in ${}^6$He. The radius is 5.77 fm.

    ↳ nucl-thnucl-exPRC(2021)·0 citations
13. 13*

    Alpha spectrometric characterization of thin ${}^{233}$U sources for ${}^{229\text{(m)}}$Th production

    Raphael Haas🇺🇸 · Michelle Hufnagel · Roman Abrosimov · Christoph E. Düllmann🇩🇪 · Dominik Krupp · Christoph Mokry · Dennis Renisch · Jörg Runke · Ulrich W. Scherer

    Four different techniques were applied for the production of ${}^{233}$U alpha recoil ion sources, providing ${}^{229}$Th ions. They were compared with respect to a minimum energy spread of the ${}^{229}$Th recoil ions, using the emitted alpha particles as an indicator. The techniques of Molecular Plating, Drop-on-Demand inkjet printing, chelation from dilute nitric acid solution on chemically functionalized silicon surfaces, and self-adsorption on passivated titanium surfaces were used. All fabricated sources were characterized by using alpha spectrometry, radiographic imaging, and scanning electron microscopy. A direct validation for the estimated recoil ion rate was obtained by collecting ${}^{228}$Th recoil ions from ${}^{232}$U recoil ion sources prepared by self-adsorption and Molecular Plating. The chelation and the self-adsorption based approaches appear most promising for the preparation of recoil ion sources delivering monochromatic recoil ions.

    ↳ physics.ins-detnucl-exRadiochim.Acta(2020)·4 citations
14. 14*

    Measurement of charged pion double spin asymmetries at midrapidity in longitudinally polarized $p$$+$$p$ collisions at $\sqrt{s}=510$ GeV

    U.A. Acharya · A. Adare · C. Aidala · N.N. Ajitanand · Y. Akiba · R. Akimoto · M. Alfred · N. Apadula · Y. Aramaki · H. Asano · E.T. Atomssa · T.C. Awes and 349 other authors

    The PHENIX experiment at the Relativistic Heavy Ion Collider has measured the longitudinal double spin asymmetries, $A_{LL}$, for charged pions at midrapidity ($|\eta |<0.35$) in longitudinally polarized $p$$+$$p$ collisions at $\sqrt{s}=510$ GeV. These measurements are sensitive to the gluon spin contribution to the total spin of the proton in the parton momentum fraction $x$ range between 0.04 and 0.09. One can infer the sign of the gluon polarization from the ordering of pion asymmetries with charge alone. The asymmetries are found to be consistent with global quantum-chromodynamics fits of deep-inelastic scattering and data at $\sqrt{s}=200$ GeV, which show a nonzero positive contribution of gluon spin to the proton spin.

    ↳ hep-exnucl-exPRD(2020)·21 citations
15. 15*

    Fluctuation dynamics near the QCD critical point

    Lipei Du🇺🇸 · Ulrich Heinz🇺🇸 · Krishna Rajagopal🇺🇸 · Yi Yin🇨🇳

    The evolution of non-hydrodynamic slow processes near the QCD critical point is explored with the novel Hydro+ framework, which extends the conventional hydrodynamic description by coupling it to additional explicitly evolving slow modes describing long wavelength fluctuations. Their slow relaxation is controlled by critical behavior of the correlation length and is independent from gradients of matter density and pressure that control the evolution of the hydrodynamic quantities. In this exploratory study we follow the evolution of the slow modes on top of a simplified QCD matter background, allowing us to clearly distinguish, and study both separately and in combination, the main effects controlling the dynamics of critical slow modes. In particular, we show how the evolution of the slow modes depend on their wave number, the expansion of and advection by the fluid background, and the behavior of the correlation length. Non-equilibrium contributions from the slow modes to bulk matter properties that affect the bulk dynamics (entropy, pressure, temperature and chemical potential) are discussed and found to be small.

    ↳ nucl-thhep-phhep-thnucl-exPRC(2020)·63 citations
16. 16*

    Magnetic moments of short-lived nuclei with part-per-million accuracy: Towards novel applications of $\beta$-detected NMR in physics, chemistry and biology

    R. D. Harding · S. Pallada · J. Croese · A. A. Antušek · M. Baranowski · M. L. Bissell · L. Cerato · Dziubinska-Kühn · W. Gins · F. P. Gustafsson · A. Javaji · R. B. Jolivet and 15 other authors

    We determine for the first time the magnetic dipole moment of a short-lived nucleus with part-per-million (ppm) accuracy. To achieve this two orders of magnitude improvement over previous studies, we implement a number of innovations into our $\beta$-detected Nuclear Magnetic Resonance ($\beta$-NMR) setup at ISOLDE/CERN. Using liquid samples as hosts we obtain narrow, sub-kHz linewidth, resonances, while a simultaneous in-situ ${}^1$H NMR measurement allows us to calibrate and stabilize the magnetic field to ppm precision, thus eliminating the need for additional $\beta$-NMR reference measurements. Furthermore, we use ab initio calculations of NMR shielding constants to improve the accuracy of the reference magnetic moment, thus removing a large systematic error. We demonstrate the potential of this combined approach with the 1.1 s half-life radioactive nucleus ${}^{26}$Na, which is relevant for biochemical studies. Our technique can be readily extended to other isotopic chains, providing accurate magnetic moments for many short-lived nuclei. Furthermore, we discuss how our approach can open the path towards a wide range of applications of the ultra-sensitive $\beta$-NMR in physics, chemistry, and biology.

    ↳ physics.chem-phnucl-exPRX(2020)·13 citations
17. 17*

    Precision efficiency calibration of a high-purity co-axial germanium detector at low energies

    B. Blank🇫🇷 · P. Ascher🇫🇷 · M. Gerbaux🇫🇷 · J. Giovinazzo🇫🇷 · S. Grevy🇫🇷 · T. Kurtukian Nieto🇫🇷 · M. Versteegen🇫🇷 · J.C. Thomas🇫🇷

    Following work done in the energy region above 100 keV, the high-precision calibration of a co-axial high-purity germanium detector has been continued in the energy region below 100 keV. Previous measurements or Monte-Carlo simulations have been repeated with higher statistics and new source measurements have been added. A precision as in the high-energy part, i.e. an absolute precision for the detection efficiency of 0.2%, has been reached. The low-energy behaviour of the germanium detector was further scrutinized by studying the germanium X-ray escape probability for the detection of low-energy photons. In addition, one experimental point, a gamma ray at 2168 keV from the decay of 38K, has been included for the total-to-peak ratios agreeing well with simulations. The same gamma ray was also added for the single- and double-escape probabilities. Finally, the long term stability of the efficiency of the germanium detector was investigated by regularly measuring the full-energy peak efficiency with a precisely calibrated 60Co source and found to be perfectly stable over a period of 10 years.

    ↳ physics.ins-detnucl-exNucl.Instrum.Meth.A(2020)·1 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.