The next generation of neutrino-less Double Beta Decay (NDBD) experiments may provide an intriguing direction for extensions of the Standard Model, including lepton number violation by two units and a new Majorana mass term in quantum field theory unlike that of the Standard Model Higgs mass. If the neutrino is a Majorana particle, it would be the only known fermion whose anti-particle is itself. The absolute scale of neutrino masses can also be uniquely determined via such experiments. These are fundamental questions of modern physics.

This award will enable the UCLA group to continue their research program in the CUORE NDBD experiment at the Gran Sasso underground laboratory. The experiment is currently in the construction phase and is expected to start data-taking by the end of 2014. The UCLA research effort will focus on the quality assurance of the CUORE electronics system and on the understanding of background sources. They will be responsible for testing, installation and commissioning of the CUORE electronics system in collaboration with the University of South Carolina and Milan groups. They will continue to work on the Monte Carlo simulations of the CUORE-0/CUORE background sources.

Broad Impact The NDBD experiments address fundamental physics issues that have a scientific impact much beyond particle and nuclear physics. The CUORE bolometer detector represents a major advance of detector technology in neutrino sciences and is probably the best alpha detector with a FWHM resolution of a few kiloelectronvolt (keV), which may have applications in nuclear radiation measurements for physics and other applied sciences. They will continue to involve their undergraduate students and NSF-REU students in the research programs and provide them with research experiences in neutrino physics and modern detector technology.

Project Report

The UCLA group has been working on the Cryogenic Underground Observatory for Rare Events (CUORE) experiment to search for neutrinoless double beta decay (0vbb) from Te130 isotopes. The NSF grant supported our participation in the CUORE experiment which includes testing of CUORE front-end read-out electronics and Monte Carlo simulations for CUORE0/CUORE background sources. One post-doc and a graduate student from UCLA were supported by the NSF grant. Experimental search for neutrinoless double beta decay is one of the frontiers of modern physics. It addresses the fundamental questions of the nature of the neutrino particle (Majorana or Dirac) and the scale of the neutrino masses. If neutrinos and anti-neutrinos are the same particle (so called Majorana particle), neutrinos would violate the lepton quantum number by 2 units and the neutrino section may reveal complete new physics beyond the Standard Model. For example, the neutrino mass will not be originated from the Standard Model Higgs mechanism. Possible CP symmetry violation in the lepton sector may also be a viable option contributing to the matter and anti-matter asymmetry in the Universe. The CUORE experiment is one of the 2nd generation of 0vbb experiments which is pushing the detection sensitivity to an interesting range. The UCLA group has been able to actively participating in this frontier research with the support from the NSF. During the period of this NSF grant, the UCLA Group completed the testing of the Bessel filter boards and the main amplifier boards for the CUORE front-end electronics project. These are critical components of the electronics system and we have devoted considerable resources to testing these boards, fix problems and characterization of the performance of the electronics. We completed the tasks of testing these two boards by the end of August 2014 and delivered the tested boards to Milan/LNGS. Our student, Brian Zhu, has been working on the Monte Carlo simulations for the background sources. We have improved the Geant description of the CUORE/CUORE0 detector in the simulation and carried out systematic simulations to match the CUORE0 measurement of the background. The simulation work is still ongoing. The CUORE experiment is expected to complete its construction in early 2015 and the commissioning and data-taking will start shortly afterwards. The UCLA group will continue to contribute to the CUORE construction and scientific program in the coming years.

National Science Foundation (NSF)
Division of Physics (PHY)
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Jonathan Whitmore
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