Tue·Jan 8, 2019Tuesday·January 8, 2019

1. 01*

   Observation of excited states in ${}^{20}$Mg sheds light on nuclear forces and shell evolution

   J. S. Randhawa🇨🇦 · R. Kanungo🇨🇦 · M. Holl🇩🇪 · J. D. Holt🇨🇦 · P. Navratil🇨🇦 · S. R. Stroberg🇨🇦 · G. Hagen🇺🇸 · G. R. Jansen🇺🇸 · M. Alcorta🇨🇦 · C. Andreoiu🇨🇦 · C. Barnes · C. Burbadge🇨🇦 and 26 other authors

   The exotic Borromean nucleus ${}^{20}$Mg with $N$ = 8, located at the proton drip-line provides a unique testing ground for nuclear forces and the evolution of shell structure in the neutron-deficient region. We report on the first observation of proton unbound resonances together with bound states in ${}^{20}$Mg from the ${}^{20}$Mg($d$,$d^{\prime }$) reaction performed at TRIUMF. Phenomenological shell-model calculations offer a reasonable description. However, our experimental results present a challenge for current first-principles nuclear structure approaches and point to the need for improved chiral forces and {\it ab initio} calculations. Furthermore, the differential cross section of the first excited state is compared with distorted-wave Born approximation calculations to deduce a neutron quadrupole deformation parameter of ${\beta }_n$=0.46$\pm$0.21. This provides the first indication of a possible weakening of the $N$ = 8 shell closure at the proton drip-line.

   nucl-exnucl-thPRC(2019)·17 citations
2. 02*

   Overview of latest results from PHENIX

   Takao Sakaguchi · PHENIX collaboration

   An overview of the latest results on the hard probes from the PHENIX experiment at RHIC is given. The results on the measurements of high $p_T$ hadrons, hadron-hadron correlations, open heavy flavor and quarkonia, and direct photons from large (Au+Au) to small collision systems ($p$+Al and $p/d{/}^3$He+Au) provided a deeper insight on the medium created in the large systems and the possible onset of QGP-nization in transition from small to large systems.

   nucl-exhep-exPoS(2019)·10 citations
3. 03*

   Doppler Broadening in ${}^{20}$Mg($\beta p\gamma$)${}^{19}$Ne Decay

   Brent E. Glassman · David Pérez-Loureiro · Chris Wrede · Jacob Allen · Dan W. Bardayan · Michael B. Bennett · Kelly A. Chipps · Michael Febbraro · Moshe Friedman · Cathleen Fry · Matt Hall · Oscar Hall and 9 other authors

   Background: The ${}^{15}$O($\alpha ,\gamma$)${}^{19}$Ne bottleneck reaction in Type I x-ray bursts is the most important thermonuclear reaction rate to constrain experimentally, in order to improve the accuracy of burst light-curve simulations. A proposed technique to determine the thermonuclear rate of this reaction employs the ${}^{20}$Mg($\beta p\alpha$)${}^{15}$O decay sequence. The key ${}^{15}$O($\alpha ,\gamma$)${}^{19}$Ne resonance at an excitation of 4.03 MeV is now known to be fed in ${}^{20}$Mg($\beta p\gamma$)${}^{19}$Ne; however, the energies of the protons feeding the 4.03 MeV state are unknown. Knowledge of the proton energies will facilitate future ${}^{20}$Mg($\beta p\alpha$)${}^{15}$O measurements. Purpose: To determine the energy of the proton transition feeding the 4.03 MeV state in ${}^{19}$Ne. Method: A fast beam of ${}^{20}$Mg was implanted into a plastic scintillator, which was used to detect $\beta$ particles. 16 high purity germanium detectors were used to detect $\gamma$ rays emitted following $\beta p$ decay. A Monte Carlo method was used to simulate the Doppler broadening of ${}^{19}$Ne $\gamma$ rays and compare to the experimental data. Results: The center of mass energy between the proton and ${}^{19}$Ne, feeding the 4.03 MeV state, is measured to be 1.21${}_{-0.22}^{+0.25}$ MeV, corresponding to a ${}^{20}$Na excitation energy of 7.44${}_{-0.22}^{+0.25}$ MeV. Absolute feeding intensities and $\gamma$-decay branching ratios of ${}^{19}$Ne states were determined including the 1615 keV state. A new $\gamma$ decay branch from the 1536 keV state in ${}^{19}$Ne to the ground state is reported. The lifetime of the 1507 keV state in ${}^{19}$Ne is measured to be 4.3${}_{-1.1}^{+1.3}$ ps resolving discrepancies in the literature. Conflicting ${}^{20}$Mg($\beta p$) decay schemes in published literature are clarified.

   nucl-exPRC(2019)·13 citations
4. 04*

   A novel approach to medical radioisotope production using inverse kinematics: a successful production test of the theranostic radionuclide 67Cu

   G Souliotis🇬🇷 · M Rodrigues🇧🇷 · K Wang🇺🇸 · V Iacob · N Nica · B Roeder🇺🇸 · G Tabacaru🇫🇷 · M Yu🇨🇦 · P Zanotti-Fregonara · A Bonasera🇺🇸

   A novel method for the production of important medical radioisotopes has been developed. The approach is based on performing the nuclear reaction in inverse kinematics, namely sending a heavy-ion beam of appropriate energy on a light target (e.g. H, d, He) and collecting the isotope of interest. In this work, as a proof-of-concept, we studied the production of the theranostic radionuclide 67Cu (T 1/2 =62 h) via the reaction of a 70Zn beam at 15 MeV/nucleon with a hydrogen gas target. The 67Cu radionuclide, alongside other coproduced isotopes, was collected after the gas target on an Al catcher foil and their radioactivity was measured by off-line {\gamma}-ray analysis. After 36 h from the end of the irradiation, apart from the product of interest 67Cu, the main radioimpurity coming from the 70Zn+p reaction was 69mZn (T 1/2 =13.8 h) that can be reduced by further radio-cooling. Moreover, along with the radionuclide of interest produced in inverse kinematics, the production of additional radioisotopes is possible by making use of the forward-focused neutrons from the reaction and letting them interact with a secondary target. A preliminary successful test of this concept was realized in the present study. The main requirement to obtain activities appropriate for preclinical studies is the development of high-intensity heavy-ion primary beams.

   ↳ physics.med-phnucl-exAppl.Radiat.Isot.(2019)·4 citations
5. 05*

   Shrinking the Quark Gluon Plasma

   Matthew D. Sievert🇺🇸 · Jacquelyn Noronha-Hostler🇺🇸

   In recent years the understanding on the limits of the smallest possible droplet of the Quark Gluon Plasma has been called into question. Experimental results from both the Large Hadron Collider and the Relativistic Heavy Ion Collider have provided hints that the Quark Gluon Plasma may be produced in systems as small as that formed in pPb or dAu collisions. Yet alternative explanations still exist from correlations arising from quarks and gluons in a color glass condensate picture. In order to resolve these two scenarios, a system size scan has been proposed at the Large Hadron Collider for collisions of ArAr and OO. Here we make predictions for a possible future run of ArAr and OO collisions at the Large Hadron Collider and study the system size dependence of a variety of flow observables. We find that linear response (from the initial conditions to the final flow harmonics) becomes more dominant in smaller systems whereas linear+cubic response can accurately predict multi-particle cumulants for a wide range of centralities in large systems.

   ↳ nucl-thhep-phnucl-exPRC(2019)·90 citations
6. 06*

   Origin of the Heaviest Elements: the Rapid Neutron-Capture Process

   John J. Cowan🇺🇸 · Christopher Sneden🇺🇸 · James E. Lawler🇺🇸 · Ani Aprahamian🇺🇸 · Michael Wiescher🇺🇸 · Karlheinz Langanke🇩🇪 · Gabriel Martínez-Pinedo🇩🇪 · Friedrich-Karl Thielemann🇨🇭

   The production of about half of the heavy elements found in nature is assigned to a specific astrophysical nucleosynthesis process: the rapid neutron capture process (r-process). Although this idea has been postulated more than six decades ago, the full understanding faces two types of uncertainties/open questions: (a) The nucleosynthesis path in the nuclear chart runs close to the neutron-drip line, where presently only limited experimental information is available, and one has to rely strongly on theoretical predictions for nuclear properties. (b) While for many years the occurrence of the r-process has been associated with supernovae, more recent studies have cast substantial doubts on this environment. Alternative scenarios include the mergers of neutron stars, neutron-star black hole mergers, but possibly also rare classes of supernovae as well as hypernovae/collapsars with polar jet ejecta and also accretion disk outflows related to the collapse of fast rotating massive stars with high magnetic fields. Stellar r-process abundance observations, have provided insights into, and constraints on the frequency of and conditions in the responsible stellar production sites. One of them, neutron star mergers, was just identified and related to the Gravitational Wave event GW170817. High resolution observations, increasingly more precise due to improved experimental atomic data, have been particularly important in defining the heavy element abundance patterns of the old halo stars, and thus determining the extent, and nature, of the earliest nucleosynthesis in our Galaxy. Combining new results and important breakthroughs in the related nuclear, atomic and astronomical fields of science, this review attempts to provide an answer to the question "How Were the Elements from Iron to Uranium Made?" (Abridged)

   ↳ astro-ph.HEnucl-exnucl-thRMP(2021)·574 citations
7. 07*

   Open Heavy Flavors in Nuclear Collisions: Theory Overview

   Pol Bernard Gossiaux🇫🇷

   I review the current status and some prospects of theoretical studies on open heavy flavor physics in nuclear collisions at RHIC and LHC energies.

   ↳ nucl-thhep-phnucl-exNPA(2019)·7 citations
8. 08*

   Recent developments in particle yield fluctuation measurements

   Igor Altsybeev🇷🇺

   In relativistic heavy-ion collisions, properties of the initial state and effects arising during evolution of the medium, such as a transition between the hadronic and partonic phases, should reflect themselves in event-by-event fluctuations of the number of produced particles. In this paper, recent measurements of several event-by-event observables, namely, dynamical fluctuations of relative particle yields and forward-backward correlations of different types, are discussed. Also, new observables for forward-backward correlation studies are proposed: correlations between ratios of identified particle yields in two separated acceptance intervals and the correlation between the ratio in one interval and average transverse momentum in another.

   ↳ hep-phnucl-exEPJ Web Conf.(2019)·0 citations
9. 09*

   Measurement of Longitudinal Single-Spin Asymmetry for W${}^{\pm }$ Production in Polarized Proton+Proton Collisions at STAR

   Qing-Hua Xu (for the STAR collaboration)🇨🇳

   The sea quark contribution to the nucleon spin is an important piece for a complete understanding of the nucleon spin structure. The production of $W$ bosons in longitudinally polarized $p+p$ collisions at RHIC provides an unique probe for the sea quark polarization, through the parity-violating single-spin asymmetry, $A_L$. At the STAR experiment, $W$ bosons can be effectively detected through the leptonic decay channel $W\to e\nu$ with the Electromagnetic Calorimeters and Time Projection Chamber at mid-rapidity. The previous STAR measurements of $A_L$ for $W$ boson production from datasets taken in 2011 and 2012 have provided significant constraints on the helicity distribution functions of $\bar{u}$ and $\bar{d}$ quarks. In 2013 the STAR experiment collected $p+p$ data with an integrated luminosity of about 250 pb${}^{-1}$ at $\sqrt{s}$ = 510 GeV with an average beam polarization of about $56\%$, which is about three times the total integrated luminosity of previous years. The final $A_L$ results from the STAR 2013 data sample are presented and are also combined with previous 2011+2012 results. The comparison with theoretical expectations suggests a flavor asymmetry with $\Delta \bar{u}(x)$ $>$$\Delta \bar{d}(x)$ for sea quark helicity distributions with $0.05<x<0.25$.

   ↳ hep-exnucl-exPoS(2018)·0 citations
10. 10*

    What laboratory experiments can teach us about cosmology: A chameleon example

    Clare Burrage🇬🇧

    Laboratory experiments can shed light on theories of new physics introduced in order to explain cosmological mysteries, including the nature of dark energy and dark matter. In this article I will focus on one particular example of this, the chameleon model. The chameleon is an example of a theory which could modify gravity on cosmological distance scales, but its non-linear behavior means that it can also be tested with suitably designed laboratory experiments. The aim of this overview is to present recent theoretical developments to the experimental community.

    ↳ astro-ph.COnucl-exEPJ Web Conf.(2019)·3 citations
11. 11*

    Charmonium production in pp collisions with ALICE at the LHC

    Lucas Altenkämper (on behalf of the ALICE Collaboration)🇳🇴

    Charmonia, bound states of charm and anti-charm quarks, represent an interesting probe for the study of Quantum Chromodynamics (QCD) since their production involves both hard and soft energy scales. Several effective models are available to describe the production of charmonia, but so far none have been able to describe all experimental observables simultaneously. ALICE has studied the production of charmonia in different collision systems at all available LHC energies at both mid- and forward-rapidity down to zero transverse momentum. In this contribution, different measurements performed in proton--proton (pp) collisions are presented, namely $p_{\text{T}}$-differential cross sections of inclusive J/$\psi$ and $\psi (2\text{S})$, inclusive J/$\psi$ polarization measurements and the latest results on correlations between inclusive J/$\psi$ and unidentified charged hadrons. The results are also compared to model predictions.

    ↳ hep-exnucl-exPoS(2019)·0 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.