Mon·Oct 19, 2020Monday·October 19, 2020

1. 01*

   Total kinetic energy and mass yields from the fast neutron-induced fission of ${}^{239}$Pu

   Alexander Chemey (1) · Ashley Pica (1) · Liangyu Yao (1) · Walter Loveland (1) · Hye Young Lee (2) · S.A. Kuvin (2)

   The total kinetic energy (TKE) release in fission is an important observable, constituting over 80% of the energy released in fission (E${}_f$ $\approx$ 200 MeV). While the TKE release in the ${}^{239}$Pu(n,f) reaction was previously measured up to 50 MeV incident neutron energy (E${}_n$), there were features in TKE release at the highest values of E${}_n$ that were puzzling. There was a marked flattening of TKE release from E${}_n$ = 30 to 50 MeV, in disagreement with the clearly decreasing TKE observed from E${}_n$ = 0.5 to 30 MeV. To verify and clarify this trend, TKE measurements at higher values of E${}_n$ were made. We present absolute measurements of TKE release in ${}^{239}$Pu(n,f) from E${}_n$ = 2.4 to 100 MeV. We used silicon PIN detectors to measure the fragment energies and deduce mass-yield curves using the 2E-method. We also discuss fission asymmetry and the relationships between approximate fission fragment mass and distortion.

   nucl-exEPJA(2020)·10 citations
2. 02*

   J/$\psi$ production measurements at mid-rapidity using the ALICE detector at the LHC

   Ingrid McKibben Lofnes (on behalf of the ALICE Collaboration)🇳🇴

   Charmonium production is highly sensitive to the hot and dense medium created in (ultra)-relativistic heavy-ion collisions, known as the Quark-Gluon Plasma (QGP). Measurements of the J/$\psi$ production serve as important tools for studying the properties of this medium. In addition to QGP effects, the J/$\psi$ production is modified by the presence of cold nuclear matter (CNM) effects such as shadowing or parton energy loss. These effects are studied in proton-nucleus collisions where no QGP formation is expected. In order to quantify how the J/$\psi$ production is modified by the medium, the vacuum production is modelled in proton-proton (pp) collisions and used as a reference for heavy-ion and proton-nucleus collisions. Measurements in pp collisions also serve as important tools for testing Quantum Chromodynamic (QCD) based models in both perturbative and non-perturbative regimes. The ALICE detector has the unique capability of measuring the J/$\psi$ at mid-rapidity through the di-electron channel down to zero transverse momentum. In this contribution a selection of the newest J/$\psi$ measurements at mid-rapidity performed by the ALICE Collaboration during the LHC Run 2 period will be discussed.

   nucl-exhep-exPoS(2020)·1 citation
3. 03*

   Annual variations of the ${}^{214}$Po, ${}^{213}$Po and ${}^{212}$Po half-life values

   E.N.Alexeev · A.M.Gangapshev🇷🇺 · Yu.M.Gavrilyuk🇷🇺 · A.M.Gezhaev · V.V.Kazalov🇷🇺 · V.V.Kuzminov🇷🇺 · S.I.Panasenko🇺🇦 · O.D.Petrenko · S.S.Ratkevich🇺🇦

   Results of a comparative analysis of the ${}^{214}$Po ($T_{1/2}=163.47\pm 0.03$ $\mu$s), ${}^{213}$Po ($T_{1/2}=3.705\pm 0.001$ $\mu$s) and ${}^{212}$Po ($T_{1/2}=294.09\pm 0.07$ ns) half-life annular variation parameters are presented. It is shown that two independent sequential sets of the ${}^{214}$Po $\tau$-values $(\tau \equiv T_{1/2})$ obtained in the spaced laboratories can be described by sinusoidal functions. The sinusoid curve with amplitude $A=(5.0\pm 1.5)\cdot 10^{-4}$, period $\omega =(365\pm 8)$ days, and phase $\varphi =(170\pm 7)$ days approximates the set of ${}^{214}$Po $\tau$ values obtained at BNO INR RAS during the $\sim$973 days starting on January 4, 2012. The function approximates a set of $\tau$-values with a time duration of $\sim 1460$ days obtained at the KhNU has an amplitude $A=(4.9\pm 1.8)\cdot 10^{-4}$, a period $\omega =(377\pm 13)$ days and a phase $\varphi =(77\pm 10)$ days. The ${}^{213}$Po $\tau$-value set with a time duration of $\sim 1700$ days can be described by a sinusoidal function with an amplitude $A=(3.9\pm 1.2)\cdot 10^{-4}$, a period $\omega =(370\pm 13)$ days and a phase $\varphi =(130\pm 9)$ days. The ${}^{212}$Po $\tau$-value set with a time duration of $\sim 670$ days can be described by a sinusoidal function with an amplitude $A=(7.5\pm 1.6)\cdot 10^{-4}$, a period $\omega =(375\pm 13)$ days and a phase $\varphi =(40\pm 10)$ days.

   nucl-exastro-ph.SRJ.Phys.Conf.Ser.(2020)·3 citations
4. 04*

   On the Possibility of Dibaryon Formation near the N*(1440)N threshold -- the Isoscalar Single-Pion Production Revisited

   H. Clement🇩🇪 · T. Skorodko🇩🇪 · E. Doroshkevich🇷🇺

   The isoscalar single-pion production exhibits a broad bump in the energy dependence of the total cross section, which does not correspond to the usual opening of the $N^{\ast }(1440)$ production channel with subsequent pion decay. In arxiv:2102.05575 it was interpreted as a narrow Breit-Wigner structure, which leads in a sequential single-pion production process to a possible explanation of the $d^{\ast }(2380)$ resonance. We demonstrate that such an attempt fails already, when confronted with the data base for isoscalar single-pion production. We investigate whether the observed bump structure rather points to the formation of dibaryon states with $I(J^P)=0(1^{+})$ and $0(1^{-})$ near the $N^{\ast }(1440)N$ threshold. This situation would be similar to the situation at the $\Delta (1232)N$ threshold, where the signature of a number of dibaryonic resonances has been found.

   nucl-exhep-exhep-phnucl-thPRC(2022)·14 citations
5. 05*

   Neutron hardness of EJ-276 scintillation material

   S. Mianowski🇵🇱 · K. Brylew🇵🇱 · A. Dziedzic🇵🇱 · K. Grzenda🇵🇱 · P. Karpowicz🇵🇱 · A. Korgul🇵🇱 · M. Krakowiak🇵🇱 · R. Prokopowicz🇵🇱 · G. Madejowski🇵🇱 · Z. Mianowska🇵🇱 · M. Moszynski🇵🇱 · T. Szczesniak🇵🇱 · M. Ziemba🇵🇱

   This paper presents the results of the fast neutron irradiation (E${}_n$ > 0.5MeV) of an EJ-276 scintillator performed in the MARIA research reactor with fluence up to 5.3$\times$10${}^{15}$ particles/cm${}^2$. In our work, four samples with size $\varphi$25.4~mm$\times$5~mm were tested. The changes in the light yield, emission and absorption spectrum and neutron/gamma discrimination using PuBe source before and after irradiation are presented. The figure of merit in neutron/gamma discrimination based on the charge integration method for different neutron fluences and different short gate integration times are determined.

   ↳ physics.ins-dethep-exnucl-exJINST(2020)·0 citations
6. 06*

   Self-Similarity, Fractality and Entropy Principle in Collisions of Hadrons and Nuclei at Tevatron, RHIC and LHC

   I. Zborovsky🇨🇿 · M. Tokarev🇷🇺

   $z$-Scaling of inclusive spectra as a manifestation of self-similarity and fractality of hadron interactions is illustrated. The scaling for negative particle production in $Au+Au$ collisions from BES-I program at RHIC is demonstrated. The scaling variable $z$ depends on the momentum fractions of the colliding objects carried by the interacting constituents, and on the momentum fractions of the fragmenting objects in the scattered and recoil directions carried by the inclusive particle and its counterpart, respectively. Structures of the colliding objects and fragmentation processes in final state are expressed by fractal dimensions. Medium produced in the collisions is described by a specific heat. The scaling function $\psi (z)$ reveals energy, angular, multiplicity, and flavor independence. It has a power behavior at high $z$ (high $p_T$). Based on the entropy principle and $z$-scaling, energy loss as a function of the collision energy, centrality and transverse momentum of inclusive particle is estimated. New conservation law including fractal dimensions is found. Quantization of fractal dimensions is discussed.

   ↳ hep-phhep-exnucl-exPoS(2021)·3 citations
7. 07*

   Isoscalar monopole and dipole transitions in ${}^{24}$Mg, ${}^{26}$Mg and ${}^{28}$Si

   P. Adsley🇿🇦 · V. O. Nesterenko🇷🇺 · M. Kimura🇯🇵 · L. M. Donaldson🇿🇦 · R. Neveling🇿🇦 · J. W. Brümmer🇿🇦 · D. G. Jenkins🇬🇧 · N. Y. Kheswa🇿🇦 · J. Kvasil🇨🇿 · K. C. W. Li🇿🇦 · D. J. Marin-Lámbarri🇿🇦 · Z. Mabika🇿🇦 and 7 other authors

   Nuclei in the $sd$-shell demonstrate a remarkable interplay of cluster and mean-field phenomena. The $N=Z$ nuclei, such as ${}^{24}$Mg and ${}^{28}$Si, have been the focus of the theoretical study of both these phenomena in the past. The cluster and vortical mean-field phenomena can be probed by excitation of isoscalar monopole and dipole states in scattering of isoscalar particles such as deuterons or $\alpha$ particles. Inelastically scattered $\alpha$ particles were momentum-analysed in the K600 magnetic spectrometer at iThemba LABS, Cape Town, South Africa. The scattered particles were detected in two multi-wire drift chambers and two plastic scintillators placed at the focal plane of the K600. In the theoretical discussion, the QRPA and AMD+GCM were used. The QRPA calculations lead us to conclude that: i) the mean-field vorticity appears mainly in dipole states with $K=1$, ii) the dipole (monopole) states should have strong deformation-induced octupole (quadrupole) admixtures, and iii) that near the $\alpha$-particle threshold, there should exist a collective state (with $K=0$ for prolate nuclei and $K=1$ for oblate nuclei) with an impressive octupole strength. The results of the AMD+GCM calculations suggest that some observed states may have a mixed (mean-field + cluster) character or correspond to particular cluster configurations. A tentative correspondence between observed states and theoretical states from QRPA and AMD+GCM was established. The QRPA and AMD+GCM analysis shows that low-energy isoscalar dipole states combine cluster and mean-field properties. The QRPA calculations show that the low-energy vorticity is well localized in ${}^{24}$Mg, fragmented in ${}^{26}$Mg, and absent in ${}^{28}$Si.

   ↳ nucl-thnucl-exPRC(2021)·12 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.