Tue·Oct 29, 2019Tuesday·October 29, 2019

1. 01*

   Pairing properties of the double-{\beta} emitter 116Cd

   D. K. Sharp🇬🇧 · S. J. Freeman🇬🇧 · B. D. Cropper🇬🇧 · P. J. Davies🇬🇧 · T. Faestermann🇩🇪 · T. M. Hatfield🇬🇧 · R. Hertenberger🇩🇪 · S. J. F. Hughes🇬🇧 · P. T. MacGregor🇬🇧 · H. -F. Wirth🇩🇪

   The pairing properties of the neutrinoless double-$\beta$ decay candidate ${}^{116}$Cd have been investigated. Measurements of the two-neutron removal reactions on isotopes of ${}^{114,116}$Cd have been made in order to identify 0${}^{+}$ strength in the residual nuclei up to $\approx$3 MeV. No significant $L=0$ strength has been found in excited states indicating that the Bardeen-Cooper-Schrieffer (BCS) approximation is a reasonable basis to describe the neutrons in the ground state. This approximation avoids complications in calculations of double-$\beta$ decay matrix elements that use the quasiparticle random-phase approximation (QRPA) techniques. However this is not the case for the protons, where pair vibrations are prevalent and the BCS approximation is no longer valid, complicating the use of traditional QRPA techniques for this system as a whole.

   nucl-exPRC(2019)·5 citations
2. 02*

   Measurement of $e^{+}{e}^{-}$ Momentum and Angular Distributions from Linearly Polarized Photon Collisions

   STAR Collaboration: M. S. Abdallah · B. E. Aboona · J. Adam · L. Adamczyk · J. R. Adams · J. K. Adkins · G. Agakishiev · I. Aggarwal · M. M. Aggarwal · Z. Ahammed · I. Alekseev · D. M. Anderson and 385 other authors

   The Breit-Wheeler process which produces matter and anti-matter from photon collisions is investigated experimentally through the observation of 6085 exclusive electron-positron pairs in ultra-peripheral Au+Au collisions at $\sqrt{s_{{}_{NN}}}=200$ GeV. The measurements reveal a large fourth-order angular modulation of $\cos 4\Delta \varphi =(16.8\pm 2.5)\%$ and smooth invariant mass distribution absent of vector mesons ($\varphi$, $\omega$ and $\rho$) at the experimental limit of $\le 0.2\%$ of the observed yields. The differential cross section as a function of $e^{+}{e}^{-}$ pair transverse momentum $P_{\perp }$ peaks at low value with $\sqrt{⟨P_{\perp }^2⟩}=38.1\pm 0.9$ MeV and displays a significant centrality dependence. These features are consistent with QED calculations for the collision of linearly polarized photons quantized from the extremely strong electromagnetic fields generated by the highly charged Au nuclei at ultra-relativistic speed. The experimental results have implications for vacuum birefringence and for mapping the magnetic field which is important for emergent QCD phenomena.

   nucl-exPRL(2021)·212 citations
3. 03*

   Study of the Hyperon-Nucleon Interaction via Final-State Interactions in Exclusive Reactions

   Nicholas Zachariou🇬🇧 · Daniel Watts🇬🇧 · Yordanka Ilieva🇺🇸

   A novel approach that allows access to long-sought information on the Hyperon-Nucleon (YN) interaction was developed by producing a hyperon beam within a few-body nuclear system, and studying final-state interactions. The determination of polarisation observables, and specifically the beam spin asymmetry, in exclusive reactions allows a detailed study of the various final-state interactions and provides us with the tools needed to isolate kinematic regimes where the YN interaction dominates. High-statistics data collected using the CLAS detector housed in Hall-B of the Thomas Jefferson laboratory allows us to obtain a large set of polarisation observables and place stringent constraints on the underlying dynamics of the YN interaction.

   nucl-exSciPost Phys.Proc.(2020)·1 citation
4. 04*

   Theoretical analysis of ${}^8$Li + ${}^{208}$Pb reaction and the critical angular momentum for complete fusion

   Bahati Mukeru · Mantile L. Lekala🇿🇦 · Jesus Lubian · Lauro Tomio🇧🇷

   In a theoretical approach, the complete and incomplete fusions are investigated by considering the ${}^8$Li+${}^{208}$Pb reaction. By decreasing the projectile ground-state binding energy ${\epsilon }_b$ from its known experimental value, the complete fusion is shown to have insignificant dependence on such variations, whereas the incomplete fusion strongly depends on that. The complete and incomplete fusion cross sections are calculated by using a combination of both continuum-discretized coupled-channel and sum-rule models. To this end, an incident-energy dependent cut-off angular momentum $L_c$ is first obtained by using the available complete fusion experimental data, within an approach which is extended to model results obtained for other incident-energies. An approximated fitted expression linking $L_c$ to the well-known critical value $L_{\mathrm{crit}}$ derived by Wilczyński [Nucl. Phys. A 216 (1973) 386] suggests a generalization of the corresponding sum-rule model to energies around and below the Coulomb barrier.

   ↳ nucl-thnucl-exNPA(2020)·8 citations
5. 05*

   Tetraneutron resonance in the presence of a dineutron

   A. Deltuva🇱🇹 · R. Lazauskas🇫🇷

   Background: Several previous studies provided contradicting results for the four-neutron system, some claiming the existence of a 0+ near-threshold resonance, others denying presence of any observable resonant states. Purpose: Since most of the studies employed enhanced two-neutron interactions to follow the evolution of an artificially bound state into a continuum one, we examine several enhancement schemes that produce a bound dineutron as well. Methods: We study the four-neutron system by solving exact four-particle equations. By varying the interaction enhancement factor we calculate two-dineutron scattering phase shifts and cross sections. Results: When the same enhancement factor is used in all partial waves, a bound tetraneutron emerges together with a strongly bound dineutron. Furthermore, such a 0+ tetraneutron evolves not into a resonance but into a virtual state. Weak enhancement of S waves together with strongly enhanced higher waves is needed for the emergence of the resonant state. Anyhow the resonant behavior disappears well before reaching the physical interaction strength. Conclusions: The interaction enhancement scheme using the same factor for all waves, employed in several previous works, is misleading for the search of 0+ resonance as only a virtual state can emerge. Evolution of a bound tetraneutron into a resonance via an intermediate virtual state is possible with strong enhancement of higher two-neutron waves.

   ↳ nucl-thnucl-exPRC(2019)·17 citations
6. 06*

   Energy and multiplicity dependence of hadronic resonance production with ALICE at the LHC

   Angela Badalá🇮🇹

   The study of hadronic resonances plays an important role both in pp and in heavy-ion collisions. Since the lifetimes of short-lived resonances are comparable with the lifetime of the fireball formed in heavy-ion collisions, regeneration and re-scattering effects can modify the measured yields, especially at low transverse momentum. Measurements in pp collisions at different energies constitute a baseline for studies in heavy-ion collisions and provide constraints for tuning QCD-inspired event generators. Furthermore, high multiplicity pp collisions, where the density and the volume of the system are expected to be larger compared to minimum bias pp collisions, can help in the search for the onset of collective phenomena. Here we present recent results on short-lived hadronic resonances obtained by the ALICE experiment at LHC energies in different collision systems (pp, p-Pb~and Pb-Pb) including new results obtained in Xe-Xe~collisions. The ALICE results on transverse momentum spectra, yields and their ratios to long-lived particles will be discussed.

   ↳ hep-exnucl-ex0 citations
7. 07*

   Pion exchange interaction in the $\gamma p\to p{e}^{+}{e}^{-}$ reaction

   Swapan Das🇮🇳

   The ${\rho }^0-\omega$ interference has been studied in the dilepton invariant mass distribution spectra in the photonuclear reaction, but that is not done for the gamma-nucleon reaction. Recent past, the $e^{+}{e}^{-}$ invariant mass distribution spectrum in the $\gamma p$ reaction, i.e., $\gamma p\to p{e}^{+}{e}^{-}$ reaction, was measured at Jefferson Laboratory to look for the ${\rho }^0-\omega$ interference in the multi-GeV region. To study the mechanism of this reaction, the differential cross section of the $e^{+}{e}^{-}$ invariant mass distribution is calculated in the quoted energy region. The reaction is assumed to proceed as $\gamma p\to Vp$; $V\to e^{+}{e}^{-}$, where $V$ denotes a vector meson, i.e., either ${\rho }^0$ or $\omega$ meson. The photoproduction of the vector meson is described by the Vector Meson Dominance (VMD) model which consists of diagonal and off-diagonal processes. The diagonal process is described as $\gamma \to V;Vp\to Vp$. The low energy $\omega$ meson photoproduction data is well described by the off-diagonal process which is illustrated as $\gamma \to {\rho }^0;{\rho }^{0}p\to \omega p$. The reaction ${\rho }^{0}p\to \omega p$ proceeds due to one pion exchange interaction. The differential cross sections of the $\gamma p\to p{e}^{+}{e}^{-}$ reaction due to the above processes of VMD model are compared, and the significance of the pion exchange interaction is investigated in the energy region of $\gamma$ beam available at Jefferson Laboratory.

   ↳ nucl-thnucl-exIJMPE(2018)·0 citations
8. 08*

   Beyond the proton drip line: Bayesian analysis of proton-emitting nuclei

   Léo Neufcourt🇺🇸 · Yuchen Cao🇺🇸 · Samuel Giuliani🇺🇸 · Witold Nazarewicz🇺🇸 · Erik Olsen🇧🇪 · Oleg B. Tarasov🇺🇸

   The limits of the nuclear landscape are determined by nuclear binding energies. Beyond the proton drip lines, where the separation energy becomes negative, there is not enough binding energy to prevent protons from escaping the nucleus. Predicting properties of unstable nuclear states in the vast territory of proton emitters poses an appreciable challenge for nuclear theory as it often involves far extrapolations. In addition, significant discrepancies between nuclear models in the proton-rich territory call for quantified predictions. With the help of Bayesian methodology, we mix a family of nuclear mass models corrected with statistical emulators trained on the experimental mass measurements, in the proton-rich region of the nuclear chart. Separation energies were computed within nuclear density functional theory using several Skyrme and Gogny energy density functionals. We also considered mass predictions based on two models used in astrophysical studies. Quantified predictions were obtained for each model using Bayesian Gaussian processes trained on separation-energy residuals and combined via Bayesian model averaging. We obtained a good agreement between averaged predictions of statistically corrected models and experiment. In particular, we quantified model results for one- and two-proton separation energies and derived probabilities of proton emission. This information enabled us to produce a quantified landscape of proton-rich nuclei. The most promising candidates for two-proton decay studies have been identified. The methodology used in this work has broad applications to model-based extrapolations of various nuclear observables. It also provides a reliable uncertainty quantification of theoretical predictions.

   ↳ nucl-thnucl-exstat.MLPRC(2020)·59 citations
9. 09*

   A decay microscope for trapped neon isotopes

   Ben Ohayon🇨🇭 · Hitesh Rahangdale🇮🇱 · Elad Parnes · Gedalia Perelman · Oded Heber · Guy Ron🇮🇱

   We review the design, simulation, and tests, of a detection system for measuring the energy distribution of daughter nuclei recoiling from the beta-decay of laser trapped neon isotopes. This distribution is sensitive to several new physics effects in the weak sector. Our `decay microscope' relies on imaging the velocity distribution of high energy recoil ions in coincidence with electrons shaken-off in the decay. We demonstrate by way of Monte-Carlo simulation, that the nuclear microscope increases the statistical sensitivity of kinematic measurements to the underlying energy distribution, and limits the main systematic bias caused by discrepancy in the trap position along the detection axis.

   ↳ physics.ins-detnucl-exPRC(2020)·7 citations
10. 10*

    Concepts for a deuterium-deuterium fusion reactor

    Roberto Onofrio🇮🇹

    We revisit the assumption that reactors based on deuterium-deuterium (D-D) fusion processes have to be necessarily developed after the successful completion of experiments and demonstrations for deuterium-tritium (D-T) fusion reactors. Two possible mechanisms for enhancing the reactivity are discussed. Hard tails in the energy distribution of the nuclei, through the so-called kappa-distribution, allow to boost the number of energetic nuclei available for fusion reactions. At higher temperatures than usually considered in D-T plasmas, vacuum polarization effects from real $e^{+}{e}^{-}$ and ${\mu }^{+}{\mu }^{-}$ pairs may provide further speed-up due to their contribution to screening of the Coulomb barrier. Furthermore, the energy collection system can benefit from the absence of the lithium blanket, both in simplicity and compactness. The usual thermal cycle can be bypassed with comparable efficiency levels using hadronic calorimetry and third-generation photovoltaic cells, possibly allowing to extend the use of fusion reactors to broader contexts, most notably maritime transport.

    ↳ physics.plasm-phnucl-exphysics.ins-detphysics.soc-phJ.Exp.Theor.Phys.(2018)·2 citations
11. 11*

    Highlights of EPS HEP 2019

    Jon Butterworth🇬🇧

    An opinionated and informal recap of highlights from the EPS HEP 2019 conference in Ghent, including some aspects of flavour physics, neutrinos, high-density QCD, astrophysics and energy frontier collider physics, and some thoughts about the future.

    ↳ hep-phastro-ph.HEhep-exnucl-exPoS(2020)·0 citations
12. 12*

    Fabrication of 3D-printed PCTFE material cups for dynamic nuclear polarization target at cryogenic temperatures

    KJ McGuire · Elena Long🇺🇸

    We present a novel method of 3D printing with the fluoroplastic Kel-F (PCTFE) that was used to create target material cups for dynamic nuclear polarization (DNP) experiments. Kel-F is used in DNP targets because it has several properties that make it well-suited to this purpose: transparency to millimeter-waves, plasticity at cryogenic temperatures, and the absence of hydrogen that would add an unwanted background to NMR signals used to measure proton polarization. A custom filament production device called the Filatizer was developed that processes commercially available rods of Kel-F into a 1.75-mm diameter filament that was 3D printed using a Prusa i3 Mk2.5S modified to achieve the high temperatures (~ 400 C) needed to melt the material and with copper-based components replaced to reduce material decomposition. This printing process does not significantly alter Kel-F's properties, and we demonstrate the first 3D-printed Kel-F target cups successfully used in DNP enhancement.

    ↳ 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.