Tue·Aug 16, 2011Tuesday·August 16, 2011

1. 01*

   Chiral three-nucleon forces and bound excited states in neutron-rich oxygen isotopes

   J. D. Holt🇺🇸 · J. Menendez🇩🇪 · A. Schwenk🇩🇪

   We study the spectra of neutron-rich oxygen isotopes based on chiral two- and three-nucleon interactions. First, we benchmark our many-body approach by comparing ground-state energies to coupled-cluster results for the same two-nucleon interaction, with overall good agreement. We then calculate bound excited states in 21,22,23O, focusing on the role of three-nucleon forces, in the standard sd shell and an extended sdf7/2p3/2 valence space. Chiral three-nucleon forces provide important one- and two-body contributions between valence neutrons. We find that both these contributions and an extended valence space are necessary to reproduce key signatures of novel shell evolution, such as the N = 14 magic number and the low-lying states in 21O and 23O, which are too compressed with two-nucleon interactions only. For the extended space calculations, this presents first work based on nuclear forces without adjustments. Future work is needed and open questions are discussed.

   ↳ nucl-thnucl-exEPJA(2013)·72 citations
2. 02*

   Search for a new gauge boson in the $A^{\prime }$ Experiment (APEX)

   S.Abrahamyan🇦🇲 · Z.Ahmed🇺🇸 · K.Allada🇺🇸 · D.Anez🇨🇦 · T.Averett🇺🇸 · A.Barbieri🇺🇸 · K.Bartlett🇺🇸 · J.Beacham🇺🇸 · J.Bono🇺🇸 · J.R.Boyce🇺🇸 · P.Brindza🇺🇸 · A.Camsonne🇺🇸 and 54 other authors

   We present a search at Jefferson Laboratory for new forces mediated by sub-GeV vector bosons with weak coupling ${\alpha }^{\prime }$ to electrons. Such a particle $A^{\prime }$ can be produced in electron-nucleus fixed-target scattering and then decay to an $e^{+}{e}^{-}$ pair, producing a narrow resonance in the QED trident spectrum. Using APEX test run data, we searched in the mass range 175--250 MeV, found no evidence for an $A^{\prime }\to e^{+}{e}^{-}$ reaction, and set an upper limit of ${\alpha }^{\prime }/\alpha \simeq 10^{-6}$. Our findings demonstrate that fixed-target searches can explore a new, wide, and important range of masses and couplings for sub-GeV forces.

   ↳ hep-exhep-phnucl-exPRL(2011)·447 citations
3. 03*

   Low background detector with enriched 116CdWO4 crystal scintillators to search for double beta decay of 116Cd

   A.S. Barabash (1)🇷🇺 · P. Belli (2)🇮🇹 · R. Bernabei (2,3)🇮🇹 · R.S. Boiko (4)🇺🇦 · F. Cappella (5,6)🇮🇹 · V. Caracciolo (7,8)🇮🇹 · D.M. Chernyak (4)🇺🇦 · R. Cerulli (7)🇮🇹 · F.A. Danevich (4)🇺🇦 · M.L. Di Vacri (7)🇮🇹 · A.E. Dossovitskiy (9)🇷🇺 · E.N. Galashov (10)🇷🇺 and 19 other authors

   A cadmium tungstate crystal boule enriched in ${}^{116}$Cd to 82% with mass of 1868 g was grown by the low-thermal-gradient Czochralski technique. The isotopic composition of cadmium and the trace contamination of the crystal were estimated by High Resolution Inductively Coupled Plasma Mass-Spectrometry. The crystal scintillators produced from the boule were subjected to characterization that included measurements of transmittance and energy resolution. A low background scintillation detector with two ${}^{116}$CdWO${}_4$ crystal scintillators (586 g and 589 g) was developed. The detector was running over 1727 h deep underground at the Gran Sasso National Laboratories of the INFN (Italy), which allowed to estimate the radioactive contamination of the enriched crystal scintillators. The radiopurity of a third ${}^{116}$CdWO${}_4$ sample (326 g) was tested with the help of ultra-low background high purity germanium $\gamma$ detector. Monte Carlo simulations of double $\beta$ processes in ${}^{116}$Cd were used to estimate the sensitivity of an experiment to search for double $\beta$ decay of ${}^{116}$Cd.

   ↳ physics.ins-detnucl-exJINST(2011)·54 citations
4. 04*

   Resonance-Parton Duality and the Transverse Response of Nucleons

   Murat Kaskulov🇩🇪 · Ulrich Mosel🇩🇪

   QCD-based scaling arguments predict the predominance of longitudinal over transverse electroproduction of pions by terms $\propto Q^2$. However, data from JLAB, Cornell and DESY, covering a wide kinematical range $1<Q^2<11{\mathrm{GeV}}^2$ and $2\mathrm{GeV}<W<4\mathrm{GeV}$, do not show this expected behavior. At the same time standard descriptions of pion-electroproduction on nucleons have given a very good description of the longitudinal components of the cross sections. However, these very same models have failed grossly in describing the transverse component. We discuss here a common solution to these two problems by considering the contributions of high-lying ($W>2$ GeV) nucleon resonances to pion production. The coupling strengths and form factors are obtained through hadron-parton duality. We show that an excellent description of data in a wide range of electron energies and four-momentum transfers can be obtained in such a model.

   ↳ nucl-thhep-phnucl-exAIP Conf.Proc.(2012)·0 citations
5. 05*

   Search for Narrow Nucleon Resonance in $\gamma p\to \eta p$

   A. V. Anisovich🇩🇪 · E. Klempt🇩🇪 · V. Kuznetsov🇰🇷 · V. A. Nikonov🇷🇺 · M. V. Polyakov🇩🇪 · A. V. Sarantsev🇷🇺 · U. Thoma🇩🇪

   Results of a partial wave analysis of new high-statistics data on $\gamma p\to p\eta$ from MAMI are presented. A fit using known broad resonances and only standard background amplitudes can not describe the relatively narrow peaking structure in the cross section in the mass region of 1660-1750 MeV which follows a minimum. An improved description of the data can be reached by either assuming the existence of a narrow resonance at a mass of about 1700 MeV with small photo-coupling or by a threshold effect. In the latter case the observed structure is explained by a strong (resonant or non-resonant) $\gamma p\to \omega p$ coupling in the $S_{11}$ partial wave. When the beam asymmetry data, published by part of the GRAAL collaboration, are included in the fit, the solution with a narrow $P_{11}$ state is slightly preferred. In that fit, mass and width of the hypothetical resonance are determined to $M\sim$1694 MeV and $\Gamma \sim 40$ MeV, respectively, and the photo-coupling to $\sqrt{{\mathrm{Br}}_{\eta N}}{A}_{1/2}^p\sim 2.6\cdot 10^{-3}$ GeV${}^{-1/2}$. High precision measurements of the target asymmetry and $F$-observable are mandatory to establish the possible existence of such a narrow state and to provide the necessary information to define which partial wave is responsible for the structure observed in the data.

   ↳ hep-phhep-exnucl-exnucl-th10 citations
6. 06*

   N*(1535) electroproduction at high Q2

   G. Ramalho🇵🇹 · M.T. Pena🇵🇹 · K. Tsushima🇦🇺

   A covariant spectator quark model is applied to study the gamma N -> N*(1535) reaction in the large Q2 region. Starting from the relation between the nucleon and N*(1535) systems, the N*(1535) valence quark wave function is determined without the addition of any parameters. The model is then used to calculate the gamma N -> N*(1535) transition form factors. A very interesting, useful relation between the A12 and S12 helicity amplitudes for Q2 > GeV^2, is also derived.

   ↳ hep-phhep-exhep-latnucl-ex+1AIP Conf.Proc.(2012)·0 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.