Mon·Apr 6, 2015Monday·April 6, 2015

1. 01*

   Nuclear structure beyond the neutron drip line: the lowest energy states in ${}^9$He via their T=5/2 isobaric analogs in ${}^9$Li

   E. Uberseder🇺🇸 · G.V. Rogachev🇺🇸 · V.Z. Goldberg🇺🇸 · E. Koshchiy · B.T. Roeder🇺🇸 · M. Alcorta🇨🇦 · G. Chubarian · B. Davids🇨🇦 · C. Fu🇺🇸 · J. Hooker🇺🇸 · H. Jayatissa · D. Melconian🇺🇸 · R.E. Tribble🇺🇸

   The level structure of the very neutron rich and unbound ${}^9$He nucleus has been the subject of significant experimental and theoretical study. Many recent works have claimed that the two lowest energy ${}^9$He states exist with spins $J^{\pi }=1/2^{+}$ and $J^{\pi }=1/2^{-}$ and widths on the order of hundreds of keV. These findings cannot be reconciled with our contemporary understanding of nuclear structure. The present work is the first high-resolution study with low statistical uncertainty of the relevant excitation energy range in the ${}^8$He$+n$ system, performed via a search for the T=5/2 isobaric analog states in ${}^9$Li populated through ${}^8$He+p elastic scattering. The present data show no indication of any narrow structures. Instead, we find evidence for a broad $J^{\pi }=1/2^{+}$ state in ${}^9$He located approximately 3 MeV above the neutron decay threshold.

   nucl-exPLB(2016)·18 citations
2. 02*

   New method for a continuous determination of the spin tune in storage rings and implications for precision experiments

   D. Eversmann🇩🇪 · V. Hejny🇩🇪 · F. Hinder🇩🇪 · A. Kacharava🇩🇪 · J. Pretz🇩🇪 · F. Rathmann🇩🇪 · M. Rosenthal🇩🇪 · F. Trinkel🇩🇪 · S. Andrianov🇷🇺 · W. Augustyniak🇵🇱 · Z. Bagdasarian🇬🇪 · M. Bai🇩🇪 and 89 other authors

   A new method to determine the spin tune is described and tested. In an ideal planar magnetic ring, the spin tune - defined as the number of spin precessions per turn - is given by ${\nu }_s=\gamma G$ (gamma is the Lorentz factor, $G$ the magnetic anomaly). For 970 MeV/c deuterons coherently precessing with a frequency of ~120 kHz in the Cooler Synchrotron COSY, the spin tune is deduced from the up-down asymmetry of deuteron carbon scattering. In a time interval of 2.6 s, the spin tune was determined with a precision of the order $10^{-8}$, and to $1\cdot 10^{-10}$ for a continuous 100 s accelerator cycle. This renders the presented method a new precision tool for accelerator physics: controlling the spin motion of particles to high precision is mandatory, in particular, for the measurement of electric dipole moments of charged particles in a storage ring.

   ↳ physics.acc-phnucl-exPRL(2015)·107 citations
3. 03*

   Sequential Regeneration of Charmonia in Heavy-Ion Collisions

   Xiaojian Du🇺🇸 · Ralf Rapp🇺🇸

   We investigate the production of psi(2S) in nuclear collisions at RHIC and LHC energies. We first address charmonium production in 200 GeV d-Au collisions at RHIC; the strong suppression of psi' mesons observed in these reactions indicates mechanisms beyond initial cold nuclear matter effects. We find that a more complete treatment of hadronic dissociation reactions leads to appreciable psi' suppression in the hadronic medium of an expanding fireball background for d-Au collisions. When implementing the updated hadronic reaction rates into a fireball for 2.76 TeV Pb-Pb collisions at LHC, the regeneration of psi' mesons occurs significantly later than for J/psi's. Despite a smaller total number of regenerated psi', the stronger radial flow at their time of production induces a marked enhancement of their R_{AA} relative to J/psi's in a momentum range p_t \simeq 3-6 GeV. We explore the consequences and uncertainties of this "sequential regeneration" mechanism on the R_{AA} double ratio and find that it can reproduce the trends observed in recent CMS data.

   ↳ hep-phnucl-exnucl-thNPA(2015)·227 citations
4. 04*

   Kaon and pion parton distribution amplitudes to twist-three

   Chao Shi🇨🇳 · Chen Chen🇨🇳 · Lei Chang🇦🇺 · Craig D. Roberts🇺🇸 · Sebastian M. Schmidt🇩🇪 · Hong-Shi Zong🇨🇳

   We compute all kaon and pion parton distribution amplitudes (PDAs) to twist-three and find that only the pseudotensor PDA can reasonably be approximated by its conformal limit expression. At terrestrially accessible energy scales, the twist-two and pseudoscalar twist-three PDAs differ significantly from those functions commonly associated with their forms in QCD's conformal limit. In all amplitudes studied, SU(3) flavour-symmetry breaking is typically a 13% effect. This scale is determined by nonperturbative dynamics; namely, the current-quark-mass dependence of dynamical chiral symmetry breaking. The heavier-quark is favoured by this distortion, for example, support is shifted to the s-quark in the negative kaon. It appears, therefore, that at energy scales accessible with existing and foreseeable facilities, one may obtain reliable expectations for experimental outcomes by using these "strongly dressed" PDAs in formulae for hard exclusive processes. Following this procedure, any discrepancies between experiment and theory will be significantly smaller than those produced by using the conformal-limit PDAs. Moreover, the magnitude of any disagreement will either be a better estimate of higher-order, higher-twist effects or provide more realistic constraints on the Standard Model.

   ↳ nucl-thhep-lathep-phnucl-exPRD(2015)·82 citations
5. 05*

   The competition between alpha decay and spontaneous fission in odd-even and odd-odd nuclei in the range 99 \leg Z \leg 129

   K. P. Santhosh🇮🇳 · B. Priyanka🇮🇳

   The predictions on the mode of decay of the odd-even and odd-odd isotopes of heavy and superheavy nuclei with Z = 99-129, in the range 228 \leg A \leg 336, have been done within the Coulomb and proximity potential model for deformed nuclei (CPPMDN). A comparison of our calculated alpha half lives with the values computed using other theoretical models shows good agreement with each other. An extensive study on the spontaneous fission half lives of all the isotopes under study has been performed to identify the long-lived isotopes in the mass region. The study reveals that the alpha decay half lives and the mode of decay of the isotopes with Z = 109, 111, 113, 115 and 117, evaluated using our formalisms, agrees well with the experimental observations. As our study on the odd-even and odd-odd isotopes of Z = 99-129 predicts that, the isotopes ${}^{238,240-254}$99, ${}^{244,246-258}$101, ${}^{248,250,252-260,262}$103, ${}^{254,256,258-262,264}$105, ${}^{258,260,262-264,266}$107, ${}^{262,264,266-274}$109, ${}^{266,268-279}$111, ${}^{270-284,286}$113, ${}^{272-289,291}$115, ${}^{274-299}$117, ${}^{276-307}$119, ${}^{281-314}$121, ${}^{287-320,322}$123, ${}^{295-325}$125, ${}^{302-327}$127 and ${}^{309-329}$129 survive fission and have alpha decay channel as the prominent mode of decay, these nuclei could possibly be synthesized in the laboratory and this could be of great interest to the experimentalists. The behaviour of these nuclei against the proton decay has also been studied to identify the probable proton emitters in this region of nuclei.

   ↳ nucl-thnucl-exNPA(2015)·26 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.