Thu·Mar 19, 2015Thursday·March 19, 2015

1. 01*

   First Measurement of the Polarization Observable E in the $\vec{p}(\vec{\gamma },{\pi }^{+})n$ Reaction up to 2.25 GeV

   S. Strauch🇺🇸 · W.J. Briscoe🇺🇸 · M. Döring🇺🇸 · E. Klempt🇩🇪 · V.A. Nikonov🇷🇺 · E. Pasyuk🇺🇸 · D. Rönchen🇩🇪 · A.V. Sarantsev🇷🇺 · I. Strakovsky🇺🇸 · R. Workman🇺🇸 · K.P. Adhikari🇺🇸 · D. Adikaram🇺🇸 and 156 other authors

   First results from the longitudinally polarized frozen-spin target (FROST) program are reported. The double-polarization observable E, for the reaction $\vec{\gamma }\vec{p}\to {\pi }^{+}n$, has been measured using a circularly polarized tagged-photon beam, with energies from 0.35 to 2.37 GeV. The final-state pions were detected with the CEBAF Large Acceptance Spectrometer in Hall B at the Thomas Jefferson National Accelerator Facility. These polarization data agree fairly well with previous partial-wave analyses at low photon energies. Over much of the covered energy range, however, significant deviations are observed, particularly in the high-energy region where high-L multipoles contribute. The data have been included in new multipole analyses resulting in updated nucleon resonance parameters. We report updated fits from the Bonn-Gatchina, Jülich, and SAID groups.

   nucl-exhep-exPLB(2015)·45 citations
2. 02*

   The electron screening puzzle and nuclear clustering

   C. Spitaleri🇮🇹 · C.A. Bertulani🇺🇸 · L. Fortunato🇮🇹 · A. Vitturi

   Accurate measurements of nuclear reactions of astrophysical interest within, or close to, the Gamow peak, show evidence of an unexpected effect attributed to the presence of atomic electrons in the target. The experiments need to include an effective "screening" potential to explain the enhancement of the cross sections at the lowest measurable energies. Despite various theoretical studies conducted over the past 20 years and numerous experimental measurements, a theory has not yet been found that can explain the cause of the exceedingly high values of the screening potential needed to explain the data. In this letter we show that instead of an atomic physics solution of the "electron screening puzzle", the reason for the large screening potential values is in fact due to clusterization effects in nuclear reactions, in particular for reaction involving light nuclei.

   nucl-exastro-ph.COastro-ph.SRnucl-thPLB(2016)·49 citations
3. 03*

   Determination of the Beam-Spin Asymmetry of Deuteron Photodisintegration in the Energy Region $E_{\gamma }=1.1-2.3$ GeV

   Nicholas Zachariou🇺🇸 · Yordanka Ilieva🇺🇸 · Nikolay Ya. Ivanov🇦🇲 · Misak M Sargsian🇺🇸 · Robert Avakian🇦🇲 · Gerald Feldman🇺🇸 · Pawel Nadel-Turonski🇺🇸 · K.P. Adhikari🇺🇸 · D. Adikaram🇺🇸 · M.D. Anderson🇬🇧 · S. Anefalos Pereira🇮🇹 · H. Avakian🇺🇸 and 131 other authors

   The beam-spin asymmetry, $\Sigma$, for the reaction $\gamma d\to pn$ has been measured using the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility (JLab) for six photon-energy bins between 1.1 and 2.3 GeV, and proton angles in the center-of-mass frame, ${\theta }_{c.m.}$, between $25^{\circ }$ and $160^{\circ }$. These are the first measurements of beam-spin asymmetries at ${\theta }_{c.m.}=90^{\circ }$ for photon-beam energies above 1.6 GeV, and the first measurements for angles other than ${\theta }_{c.m.}=90^{\circ }$. The angular and energy dependence of $\Sigma$ is expected to aid in the development of QCD-based models to understand the mechanisms of deuteron photodisintegration in the transition region between hadronic and partonic degrees of freedom, where both effective field theories and perturbative QCD cannot make reliable predictions.

   nucl-exPRC(2015)·8 citations
4. 04*

   A comparison of two magnetic ultra-cold neutron trapping concepts using a Halbach-octupole array

   K. Leung · S. Ivanov🇫🇷 · F. Martin · F. Rosenau🇫🇷 · M. Simson · O. Zimmer🇫🇷

   This paper describes a new magnetic trap for ultra-cold neutrons (UCNs) made from a 1.2 m long Halbach-octupole array of permanent magnets with an inner bore radius of 47 mm combined with an assembly of superconducting end coils and bias field solenoid. The use of the trap in a vertical, magneto-gravitational and a horizontal setup are compared in terms of the effective volume and ability to control key systematic effects that need to be addressed in high precision neutron lifetime measurements.

   ↳ physics.ins-detnucl-ex15, pages 145-154. World Scientific, 2014·0 citations
5. 05*

   Enhancement of Light Yield and Stability of Radio-Pure Tetraphenyl-Butadiene Based Coatings for VUV Light Detection in Cryogenic Environments

   Laura Baudis🇨🇭 · Giovanni Benato🇨🇭 · Rugard Dressler🇨🇭 · Francesco Piastra🇨🇭 · Ilya Usoltsev🇨🇭 · Manuel Walter🇨🇭

   The detection of VUV scintillation light, e.g. in (liquid) argon detectors, commonly includes a reflector with a fluorescent coating, converting UV photons to visible light. The light yield of these detectors depends directly on the conversion efficiency. Several coating/reflector combinations were produced using VM2000, a specular reflecting multi layer polymer, and Tetratex, a diffuse reflecting PTFE fabric, as reflector foils. The light yield of these coatings was optimised and has been measured in a dedicated liquid argon setup built at the University of Zurich. It employs a small, 1.3 kg LAr cell viewed by a 3-inch, low radioactivity PMT of type R11065-10 from Hamamatsu. The cryogenic stability of these coatings was additionally studied. The optimum reflector/coating combination was found to be Tetratex dip coated with Tetraphenyl-butadiene with a thickness of 0.9 mg/cm${}^2$ resulting in a 3.6 times higher light yield compared to uncoated VM2000. Its performance was stable in long term measurements, ran up to 100 days, in liquid argon. This coated reflector was further investigated concerning radioactive impurities found to be suitable for current and upcoming low-background experiments. Therefore it is used for the liquid argon veto in Phase II of the GERDA neutrinoless double beta decay experiment.

   ↳ physics.ins-detastro-ph.IMnucl-exJINST(2015)·12 citations
6. 06*

   A new method for analyzing collimation angle of neutron Soller collimator

   Jian-Bo Gao · Yun-Tao Liu · Dong-Feng Chen

   A new method for analyzing collimation angle of neutron Soller collimator is described. Gaussian distribution formula is used to define the angle distribution function of neutron source and neutron transmission function of Soller collimator. A relationship between FWHM of collimator rocking curve and collimation angle is derived.

   ↳ physics.ins-detnucl-exCPC(2016)·0 citations
7. 07*

   Study on neutron radiation field of carbon ions therapy

   Jun-Kui Xu · You-Wu Su · Wu-Yuan Li · Wei-Wei Yan · Xi-Meng Chen🇨🇳 · Wang Mao · Cheng-Guo Pang

   Carbon ions offer significant advantages for deep-seated local tumors therapy due to their physical and biological properties. Secondary particles, especially neutrons caused by heavy ion reactions should be carefully considered in treatment process and radiation protection. For radiation protection purposes, the FLUKA Code was used in order to evaluate the radiation field at deep tumor therapy room of HIRFL in this paper. The neutron energy spectra, neutron dose and energy deposition of carbon ion and neutron in tissue-like media was studied for bombardment of solid water target by 430MeV/u C ions. It is found that the calculated neutron dose have a good agreement with the experimental date, and the secondary neutron dose may not exceed one in a thousand of the carbon ions dose at Bragg peak area in tissue-like media.

   ↳ physics.med-phnucl-exphysics.ins-detCPC(2016)·1 citation

* 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.