Mon·Jan 26, 2015Monday·January 26, 2015

1. 01*

   A precision measurement of the $p$($e,e^{\prime }p$)${\pi }^0$ reaction at threshold

   K. Chirapatpimol · M.H. Shabestari · R.A. Lindgren · L.C. Smith · J.R.M. Annand · D.W. Higinbotham · B. Moffit · V. Nelyubin · B.E. Norum · K. Allada · K. Aniol · K. Ardashev and 82 other authors

   New results are reported from a measurement of ${\pi }^0$ electroproduction near threshold using the $p(e,e^{\prime }p){\pi }^0$ reaction. The experiment was designed to determine precisely the energy dependence of $s-$ and $p-$wave electromagnetic multipoles as a stringent test of the predictions of Chiral Perturbation Theory (ChPT). The data were taken with an electron beam energy of 1192 MeV using a two-spectrometer setup in Hall A at Jefferson Lab. For the first time, complete coverage of the ${\varphi }_{\pi }^{\ast }$ and ${\theta }_{\pi }^{\ast }$ angles in the $p{\pi }^0$ center-of-mass was obtained for invariant energies above threshold from 0.5 MeV up to 15 MeV. The 4-momentum transfer $Q^2$ coverage ranges from 0.05 to 0.155 (GeV/c)${}^2$ in fine steps. A simple phenomenological analysis of our data shows strong disagreement with $p-$wave predictions from ChPT for $Q^2>0.07$ (GeV/c)${}^2$, while the $s-$wave predictions are in reasonable agreement.

   nucl-exPRL(2015)·7 citations
2. 02*

   Unprecedented studies of the low-energy negatively charged kaons interactions in nuclear matter by AMADEUS

   C. Curceanu🇮🇹 · K. Piscicchia🇮🇹 · M. Bazzi🇮🇹 · C. Berucci🇦🇹 · D. Bosnar🇭🇷 · A.M. Bragadireanu🇷🇴 · A. Clozza🇮🇹 · M. Cargnelli🇦🇹 · A. D'uffizi🇮🇹 · L. Fabbietti🇩🇪 · C. Fiorini🇮🇹 · F. Ghio🇮🇹 and 18 other authors

   The AMADEUS experiment aims to provide unique quality data of $K^{-}$ hadronic interactions in light nuclear targets, in order to solve fundamental open questions in the non-perturbative strangeness QCD sector, like the controversial nature of the $\Lambda (1405)$ state, the yield of hyperon formation below threshold, the yield and shape of multi-nucleon $K^{-}$ absorption, processes which are intimately connected to the possible existence of exotic antikaon multi-nucleon clusters. AMADEUS takes advantage of the DA$\Phi$NE collider, which provides a unique source of monochromatic low-momentum kaons and exploits the KLOE detector as an active target, in order to obtain excellent acceptance and resolution data for $K^{-}$ nuclear capture on H, ${}^4$He, ${}^9$Be and ${}^{12}$C, both at-rest and in-flight. During the second half of 2012 a successful data taking was performed with a dedicated pure carbon target implemented in the central region of KLOE, providing a high statistic sample of pure at-rest $K^{-}$ nuclear interactions. For the future dedicated setups involving cryogenic gaseous targets are under preparation.

   nucl-exActa Phys.Polon.B(2015)·28 citations
3. 03*

   Neutron Matter from Low to High Density

   Stefano Gandolfi🇺🇸 · Alexandros Gezerlis🇨🇦 · J. Carlson🇺🇸

   Neutron matter is an intriguing nuclear system with multiple connections to other areas of physics. Considerable progress has been made over the last two decades in exploring the properties of pure neutron fluids. Here we begin by reviewing work done to explore the behavior of very low density neutron matter, which forms a strongly paired superfluid and is thus similar to cold Fermi atoms, though at energy scales differing by many orders of magnitude. We then increase the density, discussing work that ties the study of neutron matter with the determination of the properties of neutron-rich nuclei and neutron-star crusts. After this, we review the impact neutron matter at even higher densities has on the mass-radius relation of neutron stars, thereby making contact with astrophysical observations.

   ↳ nucl-thastro-ph.SRcond-mat.quant-gasnucl-exAnn.Rev.Nucl.Part.Sci.(2015)·169 citations
4. 04*

   Search for polarization effects in the antiproton production process

   D. Grzonka🇩🇪 · K. Kilian🇩🇪 · J. Ritman🇩🇪 · T. Sefzick🇩🇪 · W. Oelert🇩🇪 · M. Diermaier🇦🇹 · E. Widmann🇦🇹 · J. Zmeskal🇦🇹 · B. Glowacz🇵🇱 · P. Moskal🇵🇱 · M. Zielinski🇵🇱 · M. Wolke🇸🇪 and 12 other authors

   For the production of a polarized antiproton beam various methods have been suggested including the possibility that antiprotons may be produced polarized which will be checked experimentally. The polarization of antiprotons produced under typical conditions for antiproton beam preparation will be measured at the CERN/PS. If the production process creates some polarization a polarized antiproton beam could be prepared by a rather simple modification of the antiproton beam facility. The detection setup and the expected experimental conditions are described.

   ↳ physics.ins-dethep-exnucl-exActa Phys.Polon.B(2015)·7 citations
5. 05*

   LArGe - Active background suppression using argon scintillation for the GERDA $0\nu \beta \beta$-experiment

   M. Agostini🇩🇪 · M. Barnabé-Heider🇩🇪 · D. Budjáš🇩🇪 · C. Cattadori🇮🇹 · A. Gangapshev🇷🇺 · K. Gusev🇷🇺 · M. Heisel🇩🇪 · M. Junker🇮🇹 · A. Klimenko🇷🇺 · A. Lubashevskiy🇩🇪 · K. Pelczar🇵🇱 · S. Schönert🇩🇪 · A. Smolnikov🇩🇪 · G. Zuzel🇵🇱

   LArGe is a GERDA low-background test facility to study novel background suppression methods in a low-background environment, for future application in the GERDA experiment. Similar to GERDA, LArGe operates bare germanium detectors submersed into liquid argon (1 m${}^3$, 1.4 tons), which in addition is instrumented with photomultipliers to detect argon scintillation light. The scintillation signals are used in anti-coincidence with the germanium detectors to effectively suppress background events that deposit energy in the liquid argon. The background suppression efficiency was studied in combination with a pulse shape discrimination (PSD) technique using a BEGe detector for various sources, which represent characteristic backgrounds to GERDA. Suppression factors of a few times $10^3$ have been achieved. First background data of LArGe with a coaxial HPGe detector (without PSD) yield a background index of (0.12$-$4.6)$\cdot 10^{-2}$ cts/(keV$\cdot$kg$\cdot$y) (90% C.L.), which is at the level of GERDA Phase I. Furthermore, for the first time we monitor the natural ${}^{42}$Ar abundance (parallel to GERDA), and have indication for the $2\nu \beta \beta$-decay in natural germanium. These results show the effectivity of an active liquid argon veto in an ultra-low background environment. As a consequence, the implementation of a liquid argon veto in GERDA Phase II is pursued.

   ↳ physics.ins-detnucl-exEPJC(2015)·33 citations
6. 06*

   Characterisation of a Composite LEPS

   Moumita Roy Basu🇮🇳 · Sudatta Ray · Abhijit Bisoi · M. Saha Sarkar

   A low energy photon spectrometer (LEPS), which is a composite planar HPGe, has been characterised experimentally. It has been shown that beyond 200 keV, effect of image charges deteriorates the efficiency of the detector in its addback mode. Data has been corrected on eventby- event basis resulting in improvement of the performance.

   ↳ physics.ins-detnucl-exJINST(2015)·1 citation
7. 07*

   Top-quark production in proton-nucleus and nucleus-nucleus collisions at LHC energies and beyond

   David d'Enterria🇨🇭 · Krisztian Krajczar🇨🇭 · Hannu Paukkunen🇫🇮

   Single and pair top-quark production in proton-lead (p-Pb) and lead-lead (Pb-Pb) collisions at the CERN Large Hadron Collider (LHC) and future circular collider (FCC) energies, are studied with next-to-leading-order perturbative QCD calculations including nuclear parton distribution functions. At the LHC, the pair-production cross sections amount to sigma(t-tbar) = 3.4 mub in Pb-Pb at sqrt(s) = 5.5 TeV, and sigma(t-tbar) = 60 nb in p-Pb at sqrt(s) = 8.8 TeV. At the FCC energies of sqrt(s) = 39 and 63 TeV, the same cross sections are factors of 90 and 55 times larger respectively. In the leptonic final-state t-tbar --> W+b W-bbar --> b bbar l+l- nu+nu-, after typical acceptance and efficiency cuts, one expects about 90 and 300 top-quarks per nominal LHC-year and 4.7 10^4 and 10^5 per FCC-year in Pb-Pb and p-Pb collisions respectively. The total t-tbar cross sections, dominated by gluon fusion processes, are enhanced by 3--8% in nuclear compared to p-p collisions due to an overall net gluon antishadowing, although different regions of their differential distributions are depleted due to shadowing or EMC-effect corrections. The rapidity distributions of the decay leptons in t-tbar processes can be used to reduce the uncertainty on the Pb gluon density at high virtualities by up to 30% at the LHC (full heavy-ion programme), and by 70% per FCC-year. The cross sections for single-top production in electroweak processes are also computed, yielding about a factor of 30 smaller number of measurable top-quarks after cuts, per system and per year.

   ↳ hep-phhep-exnucl-exnucl-thPLB(2015)·61 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.