Wed·Oct 17, 2018Wednesday·October 17, 2018

1. 01*

   Collective Effects in Nuclear Collisions: Experimental Overview

   You Zhou🇩🇰

   These conferences proceedings summarize the experimental findings of collective effects in nuclear collisions, as presented at the Quark Matter 2018 conference.

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

   Investigating 16O with the 15N(p,{\alpha})12C reaction

   J.A. Swartz🇿🇦 · H.O.U. Fynbo🇩🇰 · K.L. Andersen · M. Munch🇩🇰 · O.S. Kirsebom

   The 16O nucleus was investigated through the 15N(p,{\alpha})12C reaction at excitation energies from Ex = 12 231 to 15 700 keV using proton beams from a 5 MeV Van de Graaff accelerator at beam energies of Ep = 331 to 3800 keV. Alpha decay from resonant states in 16O was strongly observed for ten known excited states in this region. The candidate 4-alpha cluster state at Ex = 15.1 MeV was investigated particularly intensely in order to understand its particle decay channels.

   nucl-exAIP Conf.Proc.(2018)·0 citations
3. 03*

   Half-Lives of Neutron Rich ${}^{130}$Cd and ${}^{131}$In

   R. Dunlop🇨🇦 · C. E. Svensson🇨🇦 · C. Andreoiu🇨🇦 · G. C. Ball🇨🇦 · N. Bernier🇨🇦 · V. Bildstein🇨🇦 · H. Bidaman🇨🇦 · P. Boubel🇨🇦 · C. Burbadge🇨🇦 · R. Caballero-Folch🇨🇦 · I. Dillmann🇨🇦 · M. R. Dunlop🇨🇦 and 31 other authors

   The half-lives of isotopes around the $N=82$ shell closure are an important ingredient in astrophysical simulations and strongly influence the magnitude of the second $r$-process abundance peak in the $A\sim 130$ region. The most neutron-rich $N=82$ nuclei are not accessible to the current generation of radioactive beam facilities and $r$-process simulations must therefore rely on calculations of the half-lives of the isotopes involved. Half-life measurements of the experimentally accessible nuclei in this region are important in order to benchmark these calculations. The half-life of ${}^{130}$Cd is particularly important as it is used to tune the Gamow-Teller quenching in shell-model calculations for the $\beta$ decay of other nuclei in this region. In this work, the GRIFFIN $\gamma$-ray spectrometer at the TRIUMF-ISAC facility was used to measure the half-life of ${}_{48}^{130}$Cd${}_{82}$ to be $T_{1/2}=126(4)$ ms. In addition, the half-lives of the three $\beta$ decaying states of ${}_{49}^{131}$In${}_{82}$ were measured to be $T_{1/2}(1/2^{-})=328(15)$ ms, $T_{1/2}(9/2^{+})=265(8)$ ms, and $T_{1/2}(21/2^{+})=323(50)$ ms, respectively, providing an important benchmark for half-life calculations in this region.

   nucl-ex0 citations
4. 04*

   The time spectra in the neutron radiative decay experiment

   R. U. Khafizov · I. A. Kolesnikov · M. V. Nikolenko · S. A. Tarnovitsky · S. V. Tolokonnikov · V. D. Torokhov · G. M. Trifonov · V. A. Solovei · M. R. Kolkhidashvili · I. V. Konorov🇩🇪

   To measure the main characteristics of radiative neutron decay, namely its relative intensity BR (branching ratio), it is necessary to measure the spectra of double coincidences between beta-electron and proton as well as the spectra of triple coincidences of electron, proton and radiative gamma-quantum. Analysis of double coincidences spectra requires one to distinguish events of ordinary neutron beta decay from the background; analysis of triple coincidences relies on distinguishing radiative neutron decay from background events. As demonstrated in our first experiment, these spectra presented a heterogeneous background that included response peaks related to the registration of electrons and protons by our electronic detection system. The NIST experimental group (emiT group) observed an analogous pattern on the spectrum of double coincidences. The current report is dedicated to the analysis of this heterogeneous background. In particular, this report demonstrates that the use of response function methodology allows to clearly identify radiative neutron decay events and to distinguish them from the background. This methodology enabled us to become the first team to measure the relative intensity of radiative neutron decay B.R.= (3.2+-1.6)*10-3 (where C.L.=99.7% and gamma quanta energy exceeds 35 kev). In addition, the review emphasizes that the background events on the spectrum of double coincidences are caused by ion registration, and demonstrates that one cannot ignore the ionic background, which is why experiment registered the ions and not recoil protons.

   nucl-exphysics.ins-det0 citations
5. 05*

   Systematic studies of charmonium-, bottomonium-, and $B_c$-like tetraquark states

   Jing Wu🇨🇳 · Xiang Liu🇨🇳 · Yan-Rui Liu🇨🇳 · Shi-Lin Zhu🇨🇳

   We study the mass splittings of $Q_1{q}_2{\bar{Q}}_3{\bar{q}}_4$ ($Q=c,b$, $q=u,d,s$) tetraquark states with chromomagnetic interactions between their quark components. Assuming that $X(4140)$ is the lowest $J^{PC}=1^{++}$ $cs\bar{c}\bar{s}$ tetraquark, we estimate the masses of the other tetraquark states. From the obtained masses and defined measure reflecting effective quark interactions, we find the following assignments for several exotic states: (1) both $X(3860)$ and the newly observed $Z_c(4100)$ seem to be $0^{++}$ $cn\bar{c}\bar{n}$ tetraquarks; (2) $Z_c(4200)$ is probably a $1^{+-}$ $cn\bar{c}\bar{n}$ tetraquark; (3) $Z_c(3900)$, $X(3940)$, and $X(4160)$ are unlikely compact tetraquarks; (4) $Z_c(4020)$ is unlikely a compact tetraquark, but seems the hidden-charm correspondence of $Z_b(10650)$ with $J^{PC}=1^{+-}$; and (5) $Z_c(4250)$ can be a tetraquark candidate but the quantum numbers cannot be assigned at present. We hope further studies may check the predictions and assignments given here.

   ↳ hep-phhep-exhep-latnucl-ex+1PRD(2019)·60 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.