Tue·Jun 2, 2015Tuesday·June 2, 2015

1. 01*

   Measurements of the ion fraction and mobility of alpha and beta decay products in liquid xenon using EXO-200

   J.B. Albert🇺🇸 · D.J. Auty🇺🇸 · P.S. Barbeau🇺🇸 · D. Beck🇺🇸 · V. Belov🇷🇺 · M. Breidenbach🇺🇸 · T. Brunner🇺🇸 · A. Burenkov🇷🇺 · G.F. Cao🇨🇳 · C. Chambers🇺🇸 · B. Cleveland🇨🇦 · M. Coon🇺🇸 and 73 other authors

   Alpha decays in the EXO-200 detector are used to measure the fraction of charged ${}^{218}\mathrm{Po}$ and ${}^{214}\mathrm{Bi}$ daughters created from alpha and beta decays, respectively. ${}^{222}\mathrm{Rn}$ alpha decays in liquid xenon (LXe) are found to produce ${}^{218}{\mathrm{Po}}^{+}$ ions $50.3\pm 3.0\%$ of the time, while the remainder of the ${}^{218}\mathrm{Po}$ atoms are neutral. The fraction of ${}^{214}{\mathrm{Bi}}^{+}$ from ${}^{214}\mathrm{Pb}$ beta decays in LXe is found to be $76.4\pm 5.7\%$, inferred from the relative rates of ${}^{218}\mathrm{Po}$ and ${}^{214}\mathrm{Po}$ alpha decays in the LXe. The average velocity of ${}^{218}\mathrm{Po}$ ions is observed to decrease for longer drift times. Initially the ions have a mobility of $0.390\pm 0.006{\mathrm{cm}}^2/(\mathrm{kV}\mathrm{s})$, and at long drift times the mobility is $0.219\pm 0.004{\mathrm{cm}}^2/(\mathrm{kV}\mathrm{s})$. Time constants associated with the change in mobility during drift of the ${}^{218}{\mathrm{Po}}^{+}$ ions are found to be proportional to the electron lifetime in the LXe.

   nucl-exphysics.ins-detPRC(2015)·87 citations
2. 02*

   Measurement of the Doubly-Polarized $\overrightarrow{{}^{3}He}(\vec{\gamma },n)pp$ Reaction at 16.5 MeV and Its Implications for the GDH Sum Rule

   G.Laskaris🇺🇸 · X.Yan · J.M.Mueller🇺🇸 · W.R.Zimmerman🇺🇸 · W.Xiong🇺🇸 · M.W.Ahmed🇺🇸 · T.Averett🇺🇸 · P.-H.Chu🇺🇸 · A.Deltuva🇱🇹 · C.Flower · A.C.Fonseca🇵🇹 · H.Gao🇺🇸 and 10 other authors

   We report new measurements of the doubly-polarized photodisintegration of ${}^3$He at an incident photon energy of 16.5 MeV, carried out at the High Intensity $\gamma$-ray Source (HI$\gamma$S) facility located at Triangle Universities Nuclear Laboratory (TUNL). The spin-dependent double-differential cross sections and the contribution from the three--body channel to the Gerasimov-Drell-Hearn (GDH) integrand were extracted and compared with the state-of-the-art three--body calculations. The calculations, which include the Coulomb interaction and are in good agreement with the results of previous measurements at 12.8 and 14.7 MeV, can no longer describe the cross section results at 16.5 MeV. The GDH integrand was found to be about one standard deviation larger than the maximum value predicted by the theories.

   nucl-exPLB(2015)·8 citations
3. 03*

   Probing the N = 32 shell closure below the magic proton number Z = 20: Mass measurements of the exotic isotopes 52,53K

   M. Rosenbusch🇩🇪 · P. Ascher🇫🇷 · D. Atanasov🇩🇪 · C. Barbieri🇬🇧 · D. Beck🇺🇸 · K. Blaum🇩🇪 · Ch. Borgmann🇩🇪 · M. Breitenfeldt🇧🇪 · R.B. Cakirli🇹🇷 · A. Cipollone🇬🇧 · S. George🇩🇪 · F. Herfurth🇩🇪 and 12 other authors

   The recently confirmed neutron-shell closure at N = 32 has been investigated for the first time below the magic proton number Z = 20 with mass measurements of the exotic isotopes 52,53K, the latter being the shortest-lived nuclide investigated at the online mass spectrometer ISOLTRAP. The resulting two-neutron separation energies reveal a 3 MeV shell gap at N = 32, slightly lower than for 52Ca, highlighting the doubly-magic nature of this nuclide. Skyrme-Hartree-Fock-Boguliubov and ab initio Gorkov-Green function calculations are challenged by the new measurements but reproduce qualitatively the observed shell effect.

   nucl-exnucl-thPRL(2015)·114 citations
4. 04*

   From CELSIUS to COSY: on the observation of a dibaryon resonance

   H. Clement🇩🇪 · M. Bashkanov🇩🇪 · T. Skorodko🇩🇪

   Using the high-quality beam of storage rings in combination with a pellet target and the hermetic WASA detector covering practically the full solid angle the two-pion production in nucleon-nucleon collisions has been systematically studied by exclusive and kinematically complete measurements -- first at CELSIUS and subsequently at COSY. These measurements resulted in a detailed understanding of the two-pion production mechanism by $t$-channel meson exchange. The investigation of the ABC effect in double-pionic fusion reactions lead the trace to the observation of a narrow dibaryon resonance with $I(J^P)=0(3^{+})$ about 80 MeV below the nominal mass of the conventional $\Delta \Delta$ system. New neutron-proton scattering data, taken with polarized beam at COSY, produce a pole in the coupled ${}^3{D}_3$ - ${}^3{G}_3$ partial waves at ($2380\pm 10-i40\pm 5$) MeV establishing thus the first observation of a genuine $s$-channel dibaryon resonance.

   nucl-exPhys.Scripta T(2015)·11 citations
5. 05*

   Measurement of differential $J/\psi$ production cross-sections and forward-backward ratio in p+Pb collisions with the ATLAS detector

   ATLAS Collaboration

   Measurements of differential cross-sections for $J/\psi$ production in p+Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV at the LHC with the ATLAS detector are presented. The data set used corresponds to an integrated luminosity of 28.1 nb${}^{-1}$. The $J/\psi$ mesons are reconstructed in the dimuon decay channel over the transverse momentum range $8<p_{\mathrm{T}}<30$ GeV and over the center-of-mass rapidity range $-2.87<y^{\ast }<1.94$. Prompt $J/\psi$ are separated from $J/\psi$ resulting from $b$-hadron decays through an analysis of the distance between the $J/\psi$ decay vertex and the event primary vertex. The differential cross-section for production of nonprompt $J/\psi$ is compared to a FONLL calculation that does not include nuclear effects. Forward-backward production ratios are presented and compared to theoretical predictions. These results constrain the kinematic dependence of nuclear modifications of charmonium and $b$-quark production in p+Pb collisions.

   ↳ hep-exnucl-exPRC(2015)·60 citations
6. 06*

   Observation of gravitationally induced vertical striation of polarized ultracold neutrons by spin-echo spectroscopy

   S. Afach🇨🇭 · N.J. Ayres🇬🇧 · G. Ban🇫🇷 · G. Bison🇨🇭 · K. Bodek🇵🇱 · Z. Chowdhuri🇨🇭 · M. Daum🇨🇭 · M. Fertl🇨🇭 · B. Franke🇨🇭 · W.C. Griffith🇬🇧 · Z.D. Grujić🇨🇭 · P.G. Harris🇬🇧 and 36 other authors

   We describe a spin-echo method for ultracold neutrons (UCNs) confined in a precession chamber and exposed to a $|B_0|=1\text{muT}$ magnetic field. We have demonstrated that the analysis of UCN spin-echo resonance signals in combination with knowledge of the ambient magnetic field provides an excellent method by which to reconstruct the energy spectrum of a confined ensemble of neutrons. The method takes advantage of the relative dephasing of spins arising from a gravitationally induced striation of stored UCN of different energies, and also permits an improved determination of the vertical magnetic-field gradient with an exceptional accuracy of $1.1\text{pT/cm}$. This novel combination of a well-known nuclear resonance method and gravitationally induced vertical striation is unique in the realm of nuclear and particle physics and should prove to be invaluable for the assessment of systematic effects in precision experiments such as searches for an electric dipole moment of the neutron or the measurement of the neutron lifetime.

   ↳ physics.ins-detnucl-exPRL(2015)·34 citations
7. 07*

   The Possible Origin and Implications of the Shoulder in Reactor Neutrino Spectra

   A.C. Hayes🇺🇸 · J. L. Friar🇺🇸 · G. T. Garvey🇺🇸 · Duligur Ibeling🇺🇸 · Gerard Jungman🇺🇸 · T. Kawano🇺🇸 · Robert W. Mills🇺🇸

   We analyze within a nuclear database framework the shoulder observed in the antineutrino spectra in current reactor experiments. We find that the ENDF/B-VII.1 database predicts that the antineutrino shoulder arises from an analogous shoulder in the aggregate fission beta spectra. In contrast, the JEFF-3.1.1 database does not predict a shoulder for two out of three of the modern reactor neutrino experiments, and the shoulder that is predicted by JEFF-3.1.1 arises from ${}^{238}$U. We consider several possible origins of the shoulder, and find possible explanations. For example, there could be a problem with the measured aggregate beta spectra, or the harder neutron spectrum at a light-water power reactor could affect the distribution of beta-decaying isotopes. In addition to the fissile actinides, we find that ${}^{238}$U could also play a significant role in distorting the total antineutrino spectrum. Distinguishing these and quantifying whether there is an anomaly associated with measured reactor neutrino signals will require new short-baseline experiments, both at thermal reactors and at reactors with a sizable epithermal neutron component.

   ↳ nucl-thhep-exnucl-exphysics.ins-detPRD(2015)·122 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.