5,934 research outputs found

    Evidence for Neutrino Mass: A Decade of Discovery

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    Neutrino mass and mixing are amongst the major discoveries of recent years. From the observation of flavor change in solar and atmospheric neutrino experiments to the measurements of neutrino mixing with terrestrial neutrinos, recent experiments have provided consistent and compelling evidence for the mixing of massive neutrinos. The discoveries at Super-Kamiokande, SNO, and KamLAND have solved the long-standing solar neutrino problem and demand that we make the first significant revision of the Standard Model in decades. Searches for neutrinoless double-beta decay probe the particle nature of neutrinos and continue to place limits on the effective mass of the neutrino. Possible signs of neutrinoless double-beta decay will stimulate neutrino mass searches in the next decade and beyond. I review the recent discoveries in neutrino physics and the current evidence for massive neutrinos.Comment: Invited talk at SEESAW25: International Conference on the Seesaw Mechanism and Neutrino Mass, Paris, France, 10-11 June 200

    Search for Sterile Neutrinos with a Radioactive Source at Daya Bay

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    The far site detector complex of the Daya Bay reactor experiment is proposed as a location to search for sterile neutrinos with > eV mass. Antineutrinos from a 500 kCi 144Ce-144Pr beta-decay source (DeltaQ=2.996 MeV) would be detected by four identical 20-ton antineutrino targets. The site layout allows flexible source placement; several specific source locations are discussed. In one year, the 3+1 sterile neutrino hypothesis can be tested at essentially the full suggested range of the parameters Delta m^2_{new} and sin^22theta_{new} (90% C.L.). The backgrounds from six nuclear reactors at >1.6 km distance are shown to be manageable. Advantages of performing the experiment at the Daya Bay far site are described

    Background Studies for the Neutral Current Detector Array in the Sudbury Neutrino Observatory

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    An array of 3He-filled proportional counters will be used in the Sudbury Neutrino Observatory to measure the neutral-current interaction of neutrinos and deuterium. We describe the backgrounds to this detection method.Comment: Accepted for publication in the proceedings of TAUP99. 2 page

    Optical Susceptibilities of Polymers: Current-Current versus Dipole-Dipole Correlation

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    The static current operator leads to definitional zero frequency divergence and unphysical results in studying nonlinear optical susceptibilities of polymers. A well-defined dipole-dipole correlation is superior to the complicated current-current correlation to solve this problem. As illustrative examples, optical susceptibilities under both SSH and TLM models of trans-(CH)_x are studied. New analytical results are obtained. The reasons of previous improper results are analyzed

    Long-Term Testing and Properties of Acrylic for the Daya Bay Antineutrino Detectors

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    The Daya Bay reactor antineutrino experiment has recently measured the neutrino mixing parameter sin22{\theta}13 by observing electron antineutrino disappearance over kilometer-scale baselines using six antineutrino detectors at near and far distances from reactor cores at the Daya Bay nuclear power complex. Liquid scintillator contained in transparent target vessels is used to detect electron antineutrinos via the inverse beta-decay reaction. The Daya Bay experiment will operate for about five years yielding a precision measurement of sin22{\theta}13. We report on long-term studies of poly(methyl methacrylate) known as acrylic, which is the primary material used in the fabrication of the target vessels for the experiment's antineutrino detectors. In these studies, acrylic samples are subjected to gaseous and liquid environmental conditions similar to those experienced during construction, transport, and operation of the Daya Bay acrylic target vessels and detectors. Mechanical and optical stability of the acrylic as well as its interaction with detector liquids is reported.Comment: 17 pages, 13 figures Submitted to JINS

    Experimental and theoretical investigation of the flashback of a swirling, bluff-body stabilised, premixed flame

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    Flashback of an open turbulent, premixed flame in a swirl burner with central bluff-body is considered. The aim is to obtain further understanding of the physical mechanisms responsible for the upstream flame propagation. Previous studies on the same configuration hypothesised that there is an adverse pressure gradient in the direction of flame propagation. In this paper this is further investigated experimentally and theoretically. Static gauge pressure is measured on the surface of the bluff-body during flame flashback. Simultaneously, flame luminosity is imaged at 5 kHz. The results indicate that the static pressure rises downstream of the propagating reactive front. This is, then, discussed in the context of the theory of vortex bursting. An existing theory of flame propagation in the core flow is extended to a configuration similar to that investigated experimentally. The theory, although highly simplified, explains the generation of adverse pressure gradient across the flame and is qualitatively consistent with the experiment

    Securing a Journalist\u27s Testimonial Privilege in the International Criminal Court

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    This Article argues that given the unique and significant contribution of journalists to uncovering and documenting war crimes, the ICC should amend its evidentiary rules to recognize a qualified journalist\u27s privilege. In doing so, the ICC should clearly identify who may benefit from such a privilege, clarify a procedure for balancing the need of reportorial testimony against prosecution and defense interests, and, lastly provide for mandatory consultations between the court and affected news organizations or journalists before allowing the issuance of a subpoena. Such clarity will benefit not only journalists working in war zones and the ICC, but will provide guidance for future ad hoc international tribunals. Part II of this paper will examine the role of journalists in war zones, discuss the Brdjanin case, and consider the challenges of codifying a qualified privilege for reporters working in conflict areas. Part II will analyze the difficulties of defining a journalist. Part IV will examine the municipal and international law bases for recognizing a journalists privilege and the effects of conflicting legal interests on such a privilege. As a comparison to journalist\u27s privilege, it will consider codified confidential communications (such as doctor-patient and priest-penitent) and officials and members of the ICRC. Part V will address the moral setting of a war crimes tribunal. Part VI will conclude with a proposed procedural rule for adoption by the ICC
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