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

Particle A Portal to Physics Beyond the Standard Model Physics Decay probability proportional to coherent sum of involved mechanisms: Hadronic coupling Nuclear Physics Phase Space Factor [Faessler et al, PRD, 83, 11 (2011), 113003] light/heavy neutrinos right-handed current gluino / R-parity 2

Particle A Portal to Physics Beyond the Standard Model Physics Decay probability proportional to coherent sum of involved mechanisms: Hadronic coupling Nuclear Physics Phase Space Factor Effective Majorana Mass light neutrinos 3

New Insight From Effective Field Theory hadronic coupling Exchange of high-energy light neutrinos ➢ expected to be a higher-order correction EFT suggests it could even be a leading ➢ p r e l i m contribution [Cirigliano et al., PRL 120 i n a r y (2018) 202001] new contact term connecting T 1/2 to m ββ ➢ impact unlear, no constraints on the ➢ NN hadronic coupling g v (not even the sign!) M. Agostini (TU Munich) 4

New Insight From EFT p r e l i m i n a r y 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: [Credit to J. Menendez] new NMEs are combinations of M 0v heavy and M 0v ➢ T 1/2 ∼ Λ 6 or Λ’ 10 ⇨ λ energy scale of new physics ➢ 5

Update on Standard NME ➢ NME estimates within a factor 3 p r e l i m i n a r y 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 Spread of NMEs within given model estimate of uncertainties M. Agostini (TU Munich) 6

Extraction of T 1/2 in the Experiments typically based on complex MV analysis Sensitivity fully defined by 2 parameters: ➢ multiparameter space composed of: sensitive exposure (M iso per live time ➢ ➢ per signal efficiency) signal region : ➢ lowest background sensitive background (background ➢ ➢ sensitivity to N 0νββ ∼ N bkg rate after analysis cuts normalized to ➢ sensitive exposure) ➢ background region : higher background ➢ ➢ important to constrain the bkg sensitivity given by counting analysis in ➢ [ M.A., G. Benato, J. Detwiler, PRD 96, 053001 2017)] signal region (with fixed background) M. Agostini (TU Munich) 7

90% CL limit Counting versus MVA setting sensitivity KamLAND-Zen 400 (asymmetric volume) r < 1.26 m (z > 0) & r < 1.06 m (z < 0) ➢ ➢ nominal sensitivity T 1/2 = 5.6e25 yr our counting analysis T 1/2 = 6.1e25 yr ➢ 3σ discovery counting nominal sensitivity analysis values nEXO (innermost volume) external background ➢ reduces with standoff distance counting and nominal ➢ sensitivities within 15% (for a FV of 1.5 ton) r 2 (m) M. Agostini (TU Munich) [Inoue, Review talk at DBD16, Osaka, Japan] [nEXO pre-CDR] 8 ] ]

Sensitivity The reach of an experiment is typically characterized through median limit setting sensitivity: 99.7% CL “limit on signal strength expected assuming no signal” upper limit 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 ➢ median limit setting sensitivity has pathological behaviours ➢ 99.7% CL signal discovery We search for a signal... let’s focus on the discovery sensitivity M. Agostini (TU Munich) [ M.A. , G Benato and J A Detwiler, PRD 96, 053001 (2017)] 9

y r a n i m i l e r p Ge experiments Xe experiments Te experiments (high natural abundance) Mo experiments Other experiments will be included soon

y r a n i m i l e r p solid liquid/gas solid

y r a n i m i l e r p Low efficiency because of fiducialization

y r a n i m i l e r p next-gen experiments < 1 bkg count/yr

Sensitive Exposure and Background p p r e r l e i m l i m i n i n a a r y r y M. Agostini (TU Munich) 14

Sensitive Exposure and Backgrounds p p r e r l e i m l i m i n i n a a r y r r y o g d n e i n t e n l u p r m o c M. Agostini (TU Munich) 15

Sensitive Exposure and Backgrounds p p r e r l e i m l i m i n i n a a r y r r y o natural Te g d n e i n t e n l u p r m o c Xe Ge Mo M. Agostini (TU Munich) 16

p r e l m ββ Projected Sensitivities i m i n a r y T 1/2 - m ββ conversion: no contact term, g a = 1.27 ➢ important achievements: ➢ m ββ = 100 meV ⇨ running experiments ➢ m ββ = 49 meV ⇨ KZ-800, SNO+ I, L200 ➢ m ββ = 17 meV ⇨ next-gen experiments ➢ IO space fully probed by some exps for IBM/EDF ➢ worst case QRPA and NSM hard to fight ➢ M. Agostini (TU Munich) 17

p r e l i m i n a r Other BSM Physics y 14 TeV Assuming contributions from leading terms: Λ’ ≳ 10 TeV for dim7 operators ➢ Λ ≳ 200 TeV for dim9 operators ➢ or Double-beta decay probes energy scales above LHC and future accelerator-based experiments! M. Agostini (TU Munich) 18

Inverted/Normal Ordering High discovery power even assuming NO: m ββ 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) Posterior probability from Bayesian fit (flat prior on phases) m ββ [eV] M. Agostini (TU Munich) 19 [ M.A. , Merle, Zuber EPJ C76 (2016) no.4, 176] [ M.A., G. Benato, J. Detwiler, PRD 96, 053001 2017)]

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 T 1/2 and dim 7/9 operators) 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! M. Agostini (TU Munich) 20

p r e l i m i n a r y

p r e l i m i n a r Time Evolution y After 5 yr live time within 30% of final T 1/2 sensitivity ➢ within 10% of final m ββ sensitivity ➢ 22

Exchange of heavy-Majorana neutrinos [A. Altre et al., JHEP 0905 (2009) 030] Rep. Prog. Phys. 79 (2016) 124201] 0 𝜉𝛾𝛾 constraint assuming no cancellation M. Agostini (TU Munich) 23

[King, Merle, Stuart, JHEP 1312, 005 (2013)] Other Extensions flavor models ➢ 3+1 sterile ➢ dim 7 and 9 operators ➢ ... ➢ [W Rodejohann, Int.J.Mod.Phys. E20(2011)] [Cirigliano et al. JHEP 12 082 (2017)] [King, Merle, Stuart, JHEP 1312, 005 (2013)] [ M.A. , Merle, Zuber EPJ C76 (2016) no.4, 176] M. Agostini (TU Munich) 24

Neutrino Mass Observables Beta-decay kinematic (KATRIN) Cosmology (Planck, Euclid) electron neutrino mass sum of neutrinos masses 17 meV Degenerate Majorana masses probed! 0 𝜉𝛾𝛾 searches, cosmological surveys and direct mass ➢ ➢ ➢ Next target inverted ordering band measurements give complementary information! M. Agostini (TU Munich) 25