FNAL PAC 20 June 2016 Caveats I am not an expert in NLDBD If I say something wrong or out of date please speak up As chair of the Nuclear Science Advisory Committee I served on the last two NSAC Subcommittees on NLDBD and chaired the Long Range Plan These reports are good summar ID: 1040181
Download Presentation The PPT/PDF document "Neutrinoless Double Beta Decay – Stat..." is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
1. Neutrinoless Double Beta Decay – Status and PlansFNAL PAC 20 June 2016
2. CaveatsI am not an expert in NLDBD. If I say something wrong or out of date, please speak up.As chair of the Nuclear Science Advisory Committee, I served on the last two NSAC Subcommittees on NLDBD and chaired the Long Range Plan. These reports are good summaries of the field and the issues. I don’t represent the agencies. I will summarize the general plans of DOE and NSF as reported to NSAC.
3. 2015 LRP Recommendations – in briefThe exact text is important!RecommendationsFollow the 2007 LRPLead a ton-scale neutrinoless double beta decay experimentBuild an Electron Ion Collider after FRIB construction is competeIncrease investment in small and mid scale projects and initiativesInitiativesTheory and Theory ComputingR&D for the EIC and neutrinoless double beta decayWorkforce, Education and Outreach3
4. RECOMMENDATION IIThe excess of matter over antimatter in the universe is one of the most compelling mysteries in all of science. The observation of neutrinoless double beta decay in nuclei would immediately demonstrate that neutrinos are their own antiparticles and would have profound implications for our understanding of the matter-antimatter mystery. We recommend the timely development and deployment of a U.S.-led ton-scale neutrinoless double beta decay experiment. A ton-scale instrument designed to search for this as-yet unseen nuclear decay will provide the most powerful test of the particle-antiparticle nature of neutrinos ever performed. With recent experimental breakthroughs pioneered by U.S. physicists and the availability of deep underground laboratories, we are poised to make a major discovery. This recommendation flows out of the targeted investments of the third bullet in Recommendation I. It must be part of a broader program that includes U.S. participation in complementary experimental efforts leveraging international investments together with enhanced theoretical efforts to enable full realization of this opportunity.4Note there is a specific cost estimate associated with this recommendation.
5. Neutrinoless Double Beta DecayObservation of Neutrinoless Double Beta Decay wouldDemonstrate the lepton number is not conservedProve that a neutrino is an elementary Majorana particle, that is, its own antiparticle.Suggest that a new mechanism for mass generation, not the Higgs mechanism, is at work.Provide evidence for one of the key ingredients that could explain the preponderance of matter over antimatter in the universe, leptogenesis. But not a direct connection.5
6. MechanismsMediated by a light Majorana neutrinoAdditional emission of hypothetical bosons calls MajoronsExchange of heavy Majorana neutrinoExchange of sterile neutrinoAll four of these mechanisms require there is a Majorana component to the neutrino mass matrix, but it does not need to be dominant.
7.
8. 80nbb decayExperimental Issues Good energy resolution Low background Majorana n Flip helicity: - RH coupling - m ≠ 0
9. 9NLDBD and Neutrino MassPhase spaceNuclear Matrix Element
10. This prize follows the 2002 Nobel prize winning work of Davis and Koshiba for detecting cosmic neutrinos.This work sets a minimum mass for the heaviest of the three neutrinos of58 meV.
11. NLDBD is Obviously at the Intersection of Nuclear and Particle PhysicsIt Is being done by groups working in both subfields that emphasize detector technologies from both subfields At DOE, neutrinoless double beta decay was declared Nuclear Physics and reactor and accelerator based oscillation neutrino experiments were declared High Energy Physics.NSF has now moved NLDBD out of Particle Astrophysics into Nuclear PhysicsOther countries divide the space differently
12. In the light neutrino exchange mechanism the decay rate depends directly on a weighted sum of the masses of light neutrinos. With data from neutrino oscillations which only measure mass differences, we know the expected weighted sum, subject to knowing the mass of the lightest neutrino, which hierarchy is realized in nature, and the new Majorana phases.Goal of ton-scale experiments12
13. Other Information on Neutrino Masses Direct measurement in nuclear beta decay: KATRIN aiming for 200 meVLong-Baseline Neutrino Oscillations (HEP): NOVA expects 3 sigma determination of hierarchy in three years. First data release of T2K and Nova provide 1-2 sigma hints of normal hierarchyIn both cases there are only a few events and the conclusion requires excellent control of backgrounds. Stay tuned.Cosmology sets limits on the sum of the masses: Current limit: Planck + BAO: < 230 meV implies mββ < 80 meV Planck + SDSS + BAO +Lyman alpha forest < 208 meVCMB-S4 + DESI project < 15 meV (early 2020’s)These constraints rely on an underlying set of simplifying model assumptions[scale invariance, flatness, w = -1, etc.]. This introduces a level of theoreticalmodel (systematic) uncertainty. Laboratory complementarity is essential.eV sterile neutrinos also can increase the weighted mass sumWe need to have double beta decay results on the same time scale as these complementary results. Tension between them can point to other well motivated neutrinoless double beta decay mechanisms or issues in cosmology.13
14.
15. New Physics and LHC15arXiv:1508.07286Type-II seesaw within left-right symmetric model
16. Neutrinoless Double Beta Decay ContextWe are aiming for U.S. leadership of the most promising ton-scale experiment, and expecting significant international and interagency (DOE, NSF) collaboration. For the highest cost options, we only projected about ~60% funding from U.S.Isotope costs: Ge $100 per gm, Te $17 per gm, Xe $9 per gm. If a positive result is seen, it needs to be confirmed on another isotope and with another technique. We expect secondary U.S. involvement in at least one other international effort would go ahead with a similar time scale.Total integrated U.S. budgets for two projects ~ $250M in $FY15Ongoing NSAC Subcommittee activities16
17. Cosmological Limits• Within the ΛCDM model, cosmology probes the neutrino freestreaming scale (neutrino hot dark matter component), which depends on Σ≡Σi mi and the relic neutrino energy spectra• Current combined bound: Σ < 230 meV This corresponds to a smaller bound on mν ~ 70-80 meV• Projected bounds ( <10 years): Σ < 100 meV (can tell ordering)Presentation to Subcommittee by K. Azerbajian (C Irvine)17
18. Major Issue: Background18 For “background-free” experiment, lifetime sensitivity goes as T1/2~ M·trun (M= isotope mass) factor of 50 in T1/2 needs factor of 50 in M (for constant trun) For experiment with background, as T1/2~ (M·trun)1/2 factor of 50 in T1/2 needs factor of 2500 in M (for constant trun) Background reduction is the key to a successful program - deep underground - radiopurity - better E resolution - better event characterization R&D will be crucial
19. Inverted Hierarchy Coverage19Figure source: A. Dueck, W. Rodejohann, and K. Zuber, Phys. Rev. D83 (2011) 113010.1026 y1027 y1028 yT½76Ge130Te136Xenow5 yrs(<mbb>=17.5meV)
20. Simple Background Estimate20NLDBD Rate = N x ln(2) / T1/2 (assume T1/2 ≈ 1028 yr)For 1 Tonne, N=106g x 6x1023 / MW (MW= 67, 130, 136 use MW≈100)So N≈ 6x1027NLDBD Rate = 0.4 /Tonne/yrBackground free Background < 0.1/Tonne/yr/ROINo one is close to this so far!
21. 21Project Isotope Isotope Mass(kg fiducial)CurrentlyAchieved(1026 yr)CUORE130Te206>0.028MAJORANA76Ge24.7GERDA76Ge18-20>0.21EXO200136Xe79>0.11NEXT-10136Xe10SuperNEMO82Se+7>0.001KamLAND-Zen136Xe434>1.1SNO+130Te160Primary goals:Demonstrate background reduction for next generation experimentExtend sensitivity to T1/2~1026 years.Current Projects2016result
22. Updated Timeline2210/15/15 NSAC MeetingConstruction Operation(not time until downselect)Today
23. Anticipated PlanWith the NSAC Subcommittee report on R&D issues, NSF and DOE are planning to submit a joint Funding Opportunity Announcement for R&D, hopefully this summer. NSF has the lead in this. Issuing a joint FOA has taken longer than anticipated. Down-select to primary DOE/NSF funded experiment in 2 ½- 3 years.International competition will be an issue. There are plans, for example, in China to move aggressively.
24. Application of modern techniques to 0nbb and 2nbb- Ab initio methods1.) Light nuclei to test gA quenching for 0nbb2.) Develop better effective interactions for heavier nucleiBetter approximations for heavy nuclei 1.) Larger model spaces2.) Density Functional Theory3.) Interacting Boson ModelLarger and broader group of nuclear theorists interested in working on this problem. This has been approved as a DOE topical collaboration in nuclear theory starting in 2016.Nuclear Theory Developments24
25. SummaryThe science is compellingWe should not wait for the results from the oscillation experiments or cosmology surveys to move forward.I anticipate we can solve the nuclear matrix element issues to at least better than a factor of two with a focused effort in theory and experiment in the next few years.The backgrounds are extremely challenging.We need to move ahead rapidly, but that always depends on budgets.