Discovery Potential of Next-Generation Double- Decay Experiments - - PowerPoint PPT Presentation

Discovery Potential of Next-Generation Double-β Decay Experiments

Matteo Agostini*, Jason Detwiler, Giovanni Benato, Javier Menendez and Francesco Vissani * Munich Technical University (TUM) TAUP 2019 Toyama Japan Sep 8-14, 2019

A Portal to Physics Beyond the Standard Model

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light/heavy neutrinos right-handed current gluino / R-parity

[Faessler et al, PRD, 83, 11 (2011), 113003]

Phase Space Factor Hadronic coupling Particle Physics Decay probability proportional to coherent sum of involved mechanisms: Nuclear Physics

Phase Space Factor Hadronic coupling

A Portal to Physics Beyond the Standard Model

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Particle Physics light neutrinos Decay probability proportional to coherent sum of involved mechanisms: Effective Majorana Mass Nuclear Physics

New Insight From Effective Field Theory

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➢ Exchange of high-energy light neutrinos expected to be a higher-order correction ➢ EFT suggests it could even be a leading contribution [Cirigliano et al., PRL 120 (2018) 202001] ➢ new contact term connecting T1/2 to mββ ➢ impact unlear, no constraints on the hadronic coupling gv

NN (not even the sign!)

• M. Agostini (TU Munich)

hadronic coupling

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New Insight From EFT

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Impact of LNV operators (dim 5/7/9) summarized by Master Formula [Cirigliano et al., JHEP 12, 097 (2018)] Assuming no interference, the master formula can be simplified as: ➢ new NMEs are combinations of M0v

heavy and M0v

➢ T1/2∼Λ6

• r Λ’ 10 ⇨ λ energy scale of new physics

[Credit to J. Menendez]

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Update on Standard NME

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➢ NME estimates within a factor 3 ➢ systematic over or under estimation ⇨ consistent NME pattern across isotopes ➢ NSM ⇨ smallest values ➢ EDF ⇨ largest values ➢ recent QRPA calculations with deformation suggest smaller NMEs than previous spherical QRPA ➢ bars in figure very small part of theoretical uncertainties

• M. Agostini (TU Munich)

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Spread of NMEs within given model estimate of uncertainties

Extraction of T1/2 in the Experiments

Sensitivity fully defined by 2 parameters: ➢ sensitive exposure (Miso per live time per signal efficiency) ➢ sensitive background (background rate after analysis cuts normalized to sensitive exposure)

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➢ typically based on complex MV analysis ➢ multiparameter space composed of: ➢ signal region: ➢ lowest background ➢ sensitivity to N0νββ∼Nbkg ➢ background region: ➢ higher background ➢ important to constrain the bkg ➢ sensitivity given by counting analysis in signal region (with fixed background)

• M. Agostini (TU Munich)

[M.A., G. Benato, J. Detwiler, PRD 96, 053001 2017)]

nEXO (innermost volume) ➢ external background reduces with standoff distance ➢ counting and nominal sensitivities within 15% (for a FV of 1.5 ton)

Counting versus MVA

KamLAND-Zen 400 (asymmetric volume) ➢ r < 1.26 m (z > 0) & r < 1.06 m (z < 0) ➢ nominal sensitivity T1/2 = 5.6e25 yr ➢

• ur counting analysis T1/2 = 6.1e25 yr

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• M. Agostini (TU Munich)

[Inoue, Review talk at DBD16, Osaka, Japan] ]

r2 (m)

[nEXO pre-CDR] ]

3σ discovery sensitivity 90% CL limit setting sensitivity counting analysis nominal values

The reach of an experiment is typically characterized through limit setting sensitivity: “limit on signal strength expected assuming no signal” signal discovery sensitivity: “minimal signal strength for which a discovery is expected” At the background level of next-gen experiments: ➢ Different sensitivity definitions ⇨ different numbers ➢ limit setting sensitivity has pathological behaviours

Sensitivity

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• M. Agostini (TU Munich)

[M.A., G Benato and J A Detwiler, PRD 96, 053001 (2017)]

median 99.7% CL signal discovery median 99.7% CL upper limit We search for a signal... let’s focus on the discovery sensitivity

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Ge experiments Xe experiments Te experiments (high natural abundance) Mo experiments Other experiments will be included soon

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solid liquid/gas solid

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Low efficiency because of fiducialization

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next-gen experiments < 1 bkg count/yr

Sensitive Exposure and Background

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• M. Agostini (TU Munich)

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Sensitive Exposure and Backgrounds

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• M. Agostini (TU Munich)

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r u n n i n g

• r

c

• m

p l e t e d

Sensitive Exposure and Backgrounds

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• M. Agostini (TU Munich)

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r u n n i n g

• r

c

• m

p l e t e d natural Te Ge Xe Mo

➢ T1/2 - mββ conversion: no contact term, ga = 1.27 ➢ important achievements: ➢ mββ = 100 meV ⇨ running experiments ➢ mββ= 49 meV ⇨ KZ-800, SNO+ I, L200 ➢ mββ= 17 meV ⇨ next-gen experiments ➢ IO space fully probed by some exps for IBM/EDF ➢ worst case QRPA and NSM hard to fight

mββ Projected Sensitivities

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• M. Agostini (TU Munich)

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Other BSM Physics

Assuming contributions from leading terms: ➢ Λ’ ≳ 10 TeV for dim7 operators ➢ Λ ≳ 200 TeV for dim9 operators Double-beta decay probes energy scales above LHC and future accelerator-based experiments!

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• M. Agostini (TU Munich)

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• r

14 TeV

Inverted/Normal Ordering

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High discovery power even assuming NO: ➢ mββ parameter space is not equiprobable, fine tuning of majorana phases for values below 1 meV ➢ classes of models have a restricted parameter space (e.g. flavor models with sum-rules)

• M. Agostini (TU Munich)

[M.A., Merle, Zuber EPJ C76 (2016) no.4, 176] [M.A., G. Benato, J. Detwiler, PRD 96, 053001 2017)]

mββ [eV] Posterior probability from Bayesian fit (flat prior on phases)

Outlook

➢ 0νββ decay is a portal to new BSM physics ➢ important to draw attention to what we can probe (e.g. using the link between T1/2 and dim 7/9

• perators)

➢ progress on NME calculations, new challenges due to the contact operator ➢ analyses are becoming increasingly complex, discussing the signal region is useful to explain the results ➢ A signal can be around the corner, let’s think in terms of a discovery!

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• M. Agostini (TU Munich)

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Time Evolution

After 5 yr live time ➢ within 30% of final T1/2 sensitivity ➢ within 10% of final mββ sensitivity

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Exchange of heavy-Majorana neutrinos

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• M. Agostini (TU Munich)
• Rep. Prog. Phys. 79 (2016) 124201]

0𝜉𝛾𝛾 constraint assuming no cancellation

[A. Altre et al., JHEP 0905 (2009) 030]

Other Extensions

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• M. Agostini (TU Munich)

[King, Merle, Stuart, JHEP 1312, 005 (2013)] [M.A., Merle, Zuber EPJ C76 (2016) no.4, 176] [King, Merle, Stuart, JHEP 1312, 005 (2013)] [Cirigliano et al. JHEP 12 082 (2017)] [W Rodejohann, Int.J.Mod.Phys. E20(2011)]

➢ flavor models ➢ 3+1 sterile ➢ dim 7 and 9 operators ➢ ...

Neutrino Mass Observables

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Beta-decay kinematic (KATRIN) electron neutrino mass

• M. Agostini (TU Munich)

Cosmology (Planck, Euclid) sum of neutrinos masses 17 meV ➢ Degenerate Majorana masses probed! ➢ Next target inverted ordering band ➢ 0𝜉𝛾𝛾 searches, cosmological surveys and direct mass measurements give complementary information!