Thu·Aug 10, 2017Thursday·August 10, 2017

1. 01*

   Measurement of the helicity asymmetry $E$ in $\omega \to {\pi }^{+}{\pi }^{-}{\pi }^0$ photoproduction

   Z. Akbar🇺🇸 · P. Roy🇩🇪 · S. Park · V. Crede🇺🇸 · A. V. Anisovich🇩🇪 · I. Denisenko🇩🇪 · E. Klempt🇩🇪 · V. A. Nikonov🇩🇪 · A. V. Sarantsev🇩🇪 · K. P. Adhikari · S. Adhikari · M. J. Amaryan🇺🇸 and 122 other authors

   The double-polarization observable $E$ was studied for the reaction $\gamma p\to p\omega$ using the CEBAF Large Acceptance Spectrometer (CLAS) in Hall B at the Thomas Jefferson National Accelerator Facility and the longitudinally-polarized frozen-spin target (FROST). The observable was measured from the charged decay mode of the meson, $\omega \to {\pi }^{+}{\pi }^{-}{\pi }^0$, using a circularly-polarized tagged-photon beam with energies ranging from the $\omega$ threshold at 1.1 to 2.3 GeV. A partial-wave analysis within the Bonn-Gatchina framework found dominant contributions from the $3/2^{+}$ partial wave near threshold, which is identified with the sub-threshold $N(1720)3/2^{+}$ nucleon resonance. To describe the entire data set, which consisted of $\omega$ differential cross sections and a large variety of polarization observables, further contributions from other nucleon resonances were found to be necessary. With respect to non-resonant mechanisms, $\pi$ exchange in the $t$-channel was found to remain small across the analyzed energy range, while pomeron $t$-channel exchange gradually grew from the reaction threshold to dominate all other contributions above $W\approx 2$ GeV.

   nucl-exhep-exPRC(2017)·25 citations
2. 02*

   Enhanced nucleon transfer in tip collisions of ${}^{238}$U+${}^{124}$Sn

   Kazuyuki Sekizawa🇯🇵

   Multinucleon transfer processes in low-energy heavy ion reactions have attracted increasing interest in recent years aiming at production of new neutron-rich isotopes. Clearly, it is an imperative task to further develop understanding of underlying reaction mechanisms to lead experiments to success. In this paper, from systematic time-dependent Hartree-Fock calculations for the ${}^{238}$U+${}^{124}$Sn reaction, it is demonstrated that transfer dynamics depend strongly on the orientations of ${}^{238}$U, quantum shells, and collision energies. Two important conclusions are obtained: (i) Experimentally observed many-proton transfer from ${}^{238}$U to ${}^{124}$Sn can be explained by a multinucleon transfer mechanism governed by enhanced neck evolution in tip collisions; (ii) Novel reaction dynamics are observed in tip collisions at energies substantially above the Coulomb barrier, where a number of nucleons are transferred from ${}^{124}$Sn to ${}^{238}$U, producing transuranium nuclei as primary reaction products, that could be a means to synthesize superheavy nuclei. Both results indicate the importance of the neck (shape) evolution dynamics, which are sensitive to the orientations, shell effects and collision energies, for exploring possible pathways to produce new unstable nuclei.

   ↳ nucl-thnucl-exPRC(2017)·63 citations
3. 03*

   Review of bottomonium measurements from CMS

   Zhen Hu🇺🇸 · Nuno T. Leonardo🇵🇹 · Tiehui Ted Liu🇺🇸 · Maksat Haytmyradov🇺🇸

   We review the results on the bottomonium system from the CMS experiment at the Large Hadron Collider. Measurements have been carried out at different center-of-mass energies in proton collisions and in collisions involving heavy ions. These include precision measurements of cross sections and polarizations, shedding light on hadroproduction mechanisms, and the observation of quarkonium sequential suppression, a notable indication of quark-gluon plasma formation. The observation of the production of bottomonium pairs is also reported along with searches for new states. We close with a brief outlook of the future physics program.

   ↳ hep-exnucl-exInt.J.Mod.Phys.A(2017)·14 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.