Mon·Jul 14, 2014Monday·July 14, 2014

1. 01*

   Inclusive spectrum of the $d({\pi }^{+},K^{+})$ reaction at 1.69 GeV/c

   Yudai Ichikawa🇯🇵 · Tomofumi Nagae🇯🇵 · Hyoungchan Bhang🇰🇷 · Stefania Bufalino🇮🇹 · Hiroyuki Ekawa🇯🇵 · Petr Evtoukhovitch🇷🇺 · Alessandro Feliciello🇮🇹 · Hiroyuki Fujioka🇯🇵 · Shoichi Hasegawa🇯🇵 · Shuhei Hayakawa🇯🇵 · Ryotaro Honda🇯🇵 · Kenji Hosomi🇯🇵 and 32 other authors

   We have measured an inclusive missing-mass spectrum of the $d({\pi }^{+},K^{+})$ reaction at the pion incident momentum of 1.69 GeV/$c$ at the laboratory scattering angles between 2${}^{\circ }$ and 16${}^{\circ }$ with the missing-mass resolution of 2.7 $\pm$ 0.1 MeV/$c^2$ (FWHM) at the missing mass of 2.27 GeV/$c^2$. In this Letter, we first try to understand the spectrum as a simple quasi-free picture based on several known elementary cross sections, considering the neutron/proton Fermi motion in deuteron. While gross spectrum structures are well understood in this picture, we have observed two distinct deviations; one peculiar enhancement at 2.13 GeV/$c^2$ is due to the $\Sigma N$ cusp, and the other notable feature is a shift of a broad bump structure, mainly originating from hyperon resonance productions of $\Lambda (1405)$ and $\Sigma (1385{)}^{+/0}$, by about 22.4 $\pm$ 0.4 (stat.) ${}_{-1.7}^{+2.7}$ (syst.) MeV/$c^2$ toward the low-mass side, which is calculated in the kinematics of a proton at rest as the target.

   nucl-exPTEP(2014)·29 citations
2. 02*

   A Technical Review of Penning Trap based Investigations in Neutron Decay

   J. Byrne🇬🇧

   This review is concerned with a detailed analysis of some of the technical problems which arise in the application of the Penning trap method to the experimental study of neutron $\beta$ -decay,a technique which was first successfully tested on the low-flux swimming-pool reactor LIDO (capture flux =3$\cdot 10^6$cm${}^{(}-2)$s${}^{(}-1)$) at AERE Harwell in the 1970's. It does not discuss the scientific merits or demerits of these studies. Of particular importance are the trapping and release of neutron decay protons, and the influence of magnetic mirror effects and radial drifting on the trapped particles. Since these have energies < 1 keV they must be accelerated to energies of order 20-30 keV following release, at which point they are recorded in a silicon surface barrier detector. However serious difficulties were encountered in the post-release acceleration process with vacuum breakdown in the presence of crossed electric and magnetic fields.

   nucl-exphysics.ins-det2 citations
3. 03*

   Polarized light ions and spectator nucleon tagging at EIC

   V. Guzey🇷🇺 · D. Higinbotham🇺🇸 · Ch. Hyde🇺🇸 · P. Nadel-Turonski🇺🇸 · K. Park🇺🇸 · M. Sargsian🇺🇸 · M. Strikman🇺🇸 · C. Weiss🇺🇸

   An Electron-Ion Collider (EIC) with suitable forward detection capabilities would enable a unique experimental program of deep-inelastic scattering (DIS) from polarized light nuclei (deuterium 2H, helium 3He) with spectator nucleon tagging. Such measurements promise significant advances in several key areas of nuclear physics and QCD: (a) neutron spin structure, by using polarized deuterium and eliminating nuclear effects through on-shell extrapolation in the spectator proton momentum; (b) quark/gluon structure of the bound nucleon at x > 0.1 and the dynamical mechanisms acting on it, by measuring the spectator momentum dependence of nuclear structure functions; (c) coherent effects in QCD, by exploring shadowing in tagged DIS on deuterium at x << 0.1. The JLab MEIC design (CM energy sqrt{s} = 15-50 GeV/nucleon, luminosity ~ 10^{34} cm^{-2} s^{-1}) provides polarized deuterium beams and excellent coverage and resolution for forward spectator tagging. We summarize the physics topics, the detector and beam requirements for spectator tagging, and on-going R&D efforts.

   ↳ hep-phnucl-exnucl-thPoS(2014)·8 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.