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Integral Neutron Multiplicity Measurements from Cosmic Ray Interactions in Lead. Thomas Ward, Techsource Inc. Alexander Rimsky-Korsakov and Nikolai Kudryashev, Khlopin Radium Institute Denis Beller, University of Nevada at Las Vegas
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Integral Neutron Multiplicity Measurements from Cosmic Ray Interactions in Lead Thomas Ward, Techsource Inc. Alexander Rimsky-Korsakov and Nikolai Kudryashev, Khlopin Radium Institute Denis Beller, University of Nevada at Las Vegas Paper presented at the XVII Particles and Nuclei International Conference, 24-28 October, 2005 held in Santa Fe, New Mexico
A Modular 60 Element He-3 Neutron Multiplicity Detector System for use in Cosmic Ray Experiments • Target consisted of 30x30x30 cm cube (300 kg) of Pb surrounded by polyethylene moderator 15 cm thick with the He-3 counters placed on all sides. • In some measurements a plastic scintillator or Geiger tube array was added on top for charged particle coincidences from above. • Cf-252 fission neutron efficiency was measured at 23.2% in agreement with MCNP and other Monte-Carlo codes. • Tests of a second identical system at UNLV produced similar results and detector performance was measured in-beam at Idaho Accelerator Center where the efficiency vs. count rate was measured and compared well with MCNPX model calculations.
Front View of NMDS at UNLV: Front detectors and steel support frame can be seen. The Pb is completely enclosed.
Above Ground and Underground Measurements • Above ground measurements made at KRI (St. Petersburg, Russia) and at UNLV (Las Vegas, Nevada), several measurements 23-552 hrs. June 2001-present. • 185mwe measurements in St. Petersburg metro tunnel, 24-432 hrs. • 583 mwe measurement at Pyhasalmi mine in Finland, February 2002 to February 2003, 6504 hrs. • 1166 mwe measurements at Pyhasalmi mine, September 2001 to February 2002, 1440 hrs.
Final Remarks • Peak at M=24 appears to be related to light charged particles, possibly protons (but not muons), which create central collisions disintegrating the Pb nucleus. We will continue to investigate the nature of this peak. • Peaks at M=31 and M=48 observed at a depth of 583 mwe are of unknown origin and are under further investigation. • Designs are being considered to increase the muon shield coverage for the entire target and to increase the Pb target volume to 100x100x100 cm, about 12 mt, for use in possible exotic dark matter or WIMP searches.
Dark Matter Particle: Residual Massive Neutral Gauge Boson (8.086 GeV)A Possible Candidate for WIMPPoster paper #111, this conference. “Simplified Extension of EW Mixing and the Generation of Massive Gauge Bosons”, Thomas Ward. • Off-diagonal mixing of EW Electromagnetic field with the scalar (Higgs), vector (EW) and tensor (G) fields provides for solution of the Higgs mass sectors (and top mass) along with predicting a new neutral massive tensor gauge boson, a good candidate for the dark matter particle. • The dark matter particle’s interaction with matter is expected to be primarily gravitational in nature with it’s lifetime determined by the weak interaction (WIMP) with ordinary matter and little interaction or decay electromagnetically or strongly. • The wavefunction of the WIMP is expected to be composed of a combination of lepton and quark scalar pair configurations. Given that the scalar pairs are deeply bound in the particle potentials only the neutral massless neutrino pairs are expected to weakly decay from the bound state interaction with baryonic matter of a nucleus. • A unique detection signature would be the reaction with Pb nucleus in which the Pb nucleus would totally disintegrate into neutrons + X in the 8.086 GeV weak interaction. • Poster Paper #111,