The Majorana Experiment
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The Majorana Experiment Experimental Design 2-decay simplified Feynman diagram. Vacuum Jacket Cold Finger A plot of sensitivity of the Majorana experiment given for different backgrounds in the Region of Interest (ROI) around the -decay Q-value (2039 keV). A cutaway view of the proposed 57-crystal cryostat module and an enlarged view of the 3-crystal string. Double-Beta Decay Recent results from Super-Kamiokande, SNO, KamLAND [1-3] and other neutrino experiments have demonstrated that neutrinos are massive and change flavor. Probing the absolute scale of neutrino masses requires completing additional experiments including direct mass measurements and neutrinoless double-beta decay searches. Τhe discovery of neutrinoless double-beta (0) decay would determine the absolute mass scale of the neutrino as well as establish the Majorana nature of the neutrino mass. The Majorana collaboration proposes to search for this process by employing high-purity, segmented germanium enriched to 86% 76 Ge as both source and detector. Recent improvements in signal processing, detector design, and advances in controlling intrinsic and external backgrounds will augment this well-established technique. In addition, the collaboration seeks to demonstrate backgrounds at or below 1 count/tonne/year in the 0 decay peak 4 keV region of interest in order to justify a possible future scaling to larger detector mass (1 tonne). Such low backgrounds would enable sensitivity to a 76 Ge 0 half-life of 5.510 26 years after an exposure time of 464 kg-years. [1] Y. Ashie et al. (Super-Kamiokande), Phys. Rev. D71, 112005 (2005), hep- ex/0501064. [2] S. N. Ahmed et al. (SNO), Phys. Rev. Lett. 92, 181301 (2004), nucl-ex/0309004. [3] T. Araki et al. (KamLAND), Phys. Rev. Lett. 94, 081801 (2005), hep-ex/0406035. In 0 neutrinos do not carry away any kinetic energy, and so the decay endpoint energy (Q-value) deposited by the two s provides the signal of interest. The plot to the right shows the double- beta decay spectrum and position of the 0 peak as a function of the sum of the electrons’ energy normalized to the Q-value of the decay (2039 keV for 76 Ge). 0-decay simplified Feynman diagram. Most even-even nuclei are energetically forbidden to undergo decay. However, double-beta decay is possible for a number of these nuclei. This process (2-decay) involving 2 neutrinos and 2 s has been observed, for example: The more interesting and as yet unobserved case occurs when the two neutrons exchange a virtual neutrino and emit no neutrinos (0 decay). 0 decay requires that neutrinos be their own anti-particles, or Majorana particles. An experimental measurement of this process would provide an indication of physics beyond the standard model. Abstract S. R. Elliott and P. Vogel, Ann. Rev. Nucl. Part. Sci. 52, 115 (2002). Three stripped-away views of proposed experimental setup with multiple modules. Clockwise from above: shown with copper shield; with lead shielding; and with muon-veto shielding. This design enables removing and adding modules without disturbing other modules. 57-crystal modules Copper shield Dewars Lead shield Muon veto LFEPs Background Reduction The Majorana Experiment will make use of the latest in background rejection techniques, material assay, and clean construction methods in an effort to reach our background goal of 1 count/tonne-year in the 4 keV region of interest around 2039 keV. Multi-crystal granularity: The close-packed, 57-crystal array design increases the chance of rejection in a multiple crystal event. Simultaneous signals in two detectors cannot be 0. Segmentation allows for further discrimination of multi-site events within an individual crystal. Shown is a 2 x 3 segmentation scheme as in the Majorana Reference Design. Single-site time correlation: Looking forward or backward in time from an event in the ROI to find a signature of parent or daughter isotopes at the same location can lead to further background reduction (rejection of 68 Ge shown). Pulse-shape analysis can distinguish between single-site (top of figure) and multi-site (bottom of figure) events, perform a full 3-D reconstruction of an event, and potentially serve to reject surface activity. The largest background contributions for Majorana originate from impurities in copper. Advances in the electroforming of copper underground and in the development of ultra-sensitive material assay methods (ICPMS) lead to construction of ultra-pure materials. Sensitivity Cap Tube (0.0178 cm wall) Ge (1.1 kg) (62mm x 70 mm) Tray (Plastic, Si, etc) N2 sparse gas flow control Programmable power supply Radium & particulate filtration and chemical scavenge Inner bath containment & Cu bus Cu sulfate bath with cover gas, mandrel, current Front view Side view Corrosive aerosol & gas removal
description
The Majorana Experiment. Radium & particulate filtration and chemical scavenge. Corrosive aerosol & gas removal. Front view. Side view. N2 sparse gas flow control. Inner bath containment & Cu bus. Cu sulfate bath with cover gas, mandrel, current. Programmable power supply. Abstract. - PowerPoint PPT Presentation
Transcript of The Majorana Experiment
The Majorana Experiment
Experimental Design
2-decay simplified Feynman diagram.
Vacuum
Jacket
ColdFinger
A plot of sensitivity of the Majorana experiment given for different backgrounds in the Region of Interest (ROI) around the -decay Q-value (2039 keV).
A cutaway view of the proposed 57-crystal cryostat module and an enlarged view of the 3-crystal string.
Double-Beta Decay
Recent results from Super-Kamiokande, SNO, KamLAND [1-3] and other neutrino experiments have demonstrated that neutrinos are massive and change flavor. Probing the absolute scale of neutrino masses requires completing additional experiments including direct mass measurements and neutrinoless double-beta decay searches. Τhe discovery of neutrinoless double-beta (0) decay would determine the absolute mass scale of the neutrino as well as establish the Majorana nature of the neutrino mass. The Majorana collaboration proposes to search for this process by employing high-purity, segmented germanium enriched to 86% 76Ge as both source and detector. Recent improvements in signal processing, detector design, and advances in controlling intrinsic and external backgrounds will augment this well-established technique. In addition, the collaboration seeks to demonstrate backgrounds at or below 1 count/tonne/year in the 0 decay peak 4 keV region of interest in order to justify a possible future scaling to larger detector mass (1 tonne). Such low backgrounds would enable sensitivity to a 76Ge 0 half-life of 5.51026 years after an exposure time of 464 kg-years. [1] Y. Ashie et al. (Super-Kamiokande), Phys. Rev. D71, 112005 (2005), hep-ex/0501064.[2] S. N. Ahmed et al. (SNO), Phys. Rev. Lett. 92, 181301 (2004), nucl-ex/0309004.[3] T. Araki et al. (KamLAND), Phys. Rev. Lett. 94, 081801 (2005), hep-ex/0406035.
In 0 neutrinos do not carry away any kinetic energy, and so the decay endpoint energy (Q-value) deposited by the two s provides the signal of interest. The plot to the right shows the double-beta decay spectrum and position of the 0 peak as a function of the sum of the electrons’ energy normalized to the Q-value of the decay (2039 keV for 76Ge).
0-decay simplified Feynman diagram.
Most even-even nuclei are energetically forbidden to undergo decay. However, double-beta decay is possible for a number of these nuclei. This process (2-decay) involving 2 neutrinos and 2 s has been observed, for example:
The more interesting and as yet unobserved case occurs when the two neutrons exchange a virtual neutrino and emit no neutrinos (0 decay). 0 decay requires that neutrinos be their own anti-particles, or Majorana particles. An experimental measurement of this process would provide an indication of physics beyond the standard model.
Abstract
S. R. Elliott and P. Vogel, Ann. Rev. Nucl. Part. Sci. 52, 115 (2002).
Three stripped-away views of proposed experimental setup with multiple modules. Clockwise from above: shown with copper shield; with lead shielding; and with muon-veto shielding. This design enables removing and adding modules without disturbing other modules.
57-crystalmodules
57-crystalmodules
Coppershield
Coppershield
DewarsDewars
LeadshieldLead
shield
Muon vetoMuon veto
LFEPsLFEPs
Background ReductionThe Majorana Experiment will make use of the latest in background rejection techniques, material assay, and clean construction methods in an effort to reach our background goal of 1 count/tonne-year in the 4 keV region of interest around 2039 keV.
Multi-crystal granularity: The close-packed, 57-crystal array design increases the chance of rejection in a multiple crystal event. Simultaneous signals in two detectors cannot be
0.
Segmentation allows for further discrimination of multi-site events within an individual crystal. Shown is a 2 x 3 segmentation scheme as in the Majorana Reference Design.
Single-site time correlation: Looking forward or backward in time from an event in the ROI to find a signature of parent or daughter isotopes at the same location can lead to further background reduction (rejection of 68Ge shown).
Pulse-shape analysis can distinguish between single-site (top of figure) and multi-site (bottom of figure) events, perform a full 3-D reconstruction of an event, and potentially serve to reject surface activity.
The largest background contributions for Majorana originate from impurities in copper. Advances in the electroforming of copper underground and in the development of ultra-sensitive material assay methods (ICPMS) lead to construction of ultra-pure materials.
Sensitivity
CapCap
Tube (0.0178 cm wall)
Tube (0.0178 cm wall)
Ge (1.1 kg)(62mm x 70 mm)
Ge (1.1 kg)(62mm x 70 mm)
Tray(Plastic, Si, etc)
Tray(Plastic, Si, etc)
N2 sparse gas flow control
Programmable power supply
Radium & particulate filtration and chemical scavenge
Inner bath containment & Cu bus
Cu sulfate bath with cover gas, mandrel, current
Front view Side view
Corrosive aerosol & gas removal
