Connecting Neutrinoless double beta decay to colliders. Or not. Amherst, Massachusetts July 2017 Michael Graesser (Los Alamos) based on: MG, arXiv:1606.04549, submitted to JHEP V. Cirigliano, W. Dekens, MG, E. Mereghetti, (PLB 2017,1701.01443) V. Cirigliano, W. Dekens, J. de Vries, MG, E. Mereghetti, (1707/08.zzzz)
Neutrinoless double beta decay and TeV* scale physics Motivation Neutrinos have mass and search is on to discover the nature of their mass. Ongoing or future experiments may detect a “neutrinoless double beta decay” signal. Such a signal arises when neutrino masses violate lepton number (i.e., Majorana) Question: is that the correct interpretation of such a signal? Are there other (new physics scenario) interpretations?
New physics scenarios for neutrinoless double beta decay Should a Δ L=2 signal be detected, such exotic possibilities should be excluded before concluding that effect is due to Majorana neutrino exchange Resolving competing explanations may need a next-generation detector reconstructing both electron kinematics (e.g. NEXT, SuperNEMO) 300 300 300 250 250 250 � m Ν � � meV � � m Ν � � meV � � m Ν � � meV � 200 200 200 150 150 150 100 100 100 50 50 50 0 0 0 � 4 � 2 0 2 4 � 4 � 2 0 2 4 � 4 � 2 0 2 4 Λ � 10 � 7 � Λ � 10 � 7 � Λ � 10 � 7 � (a) (b) (c) Comparison SuperNEMO sensitivity to various admixtures of W R contribution (0%, 30%, 100%). Figure from Arnold et. al. (SuperNEMO, 2010) • If hierarchy is “normal’’, then planned 0nubb have no chance of detecting Standard Model Majorana neutrinos (outside of the quasi-degenerate region) • In such a circumstance, only hope is for exotic scenarios
BSM contributions to neutrinoless beta decay: Left-Right symmetric model • new electroweak gauge bosons couple to right-handed currents • new right-handed or “sterile” neutrinos, electroweak partners of Standard Model right-handed electron d u • possibility for type-II see-saw at TeV scale L Y = 1 ↵ ∆ L � ∆ L ⌅ L + 1 M ν L M ν R ↵ ∆ R � ∆ R ⌅ R + h.c. , 2 ⌅ L 2 ⌅ R W R • Assuming a type-II see-saw, C invariance leads e − the connection between th M ν R / ↵ ∆ R � = M ∗ ν L / ↵ ∆ L � ∗ . or m N m ν X N R M R the proportionality of the lightest m N in GeV 1 10 100 400 500 1. 1 . 0 e − 0.5 normal inverted W R ν + N | in eV 0.1 0 . 1 u 0.05 | m ee d 0.01 0 . 01 0.005 M WR = 3 . 5 TeV largest m N = 0 . 5 TeV 10 − 3 0.001 10 − 4 10 4 0.001 0 . 001 0.01 0 . 01 0.1 0 . 1 1 1 lightest neutrino mass in eV Figure from Tello, Nemevsek, Nesti, Senjanovic and Vissani, 2011
BSM contributions to neutrinoless beta decay: R-parity violation inspired • see also e.g. Deppisch, Hirsch, Pas, 2012 • new charged scalar leptons (“sleptons”) d u • new electroweak partners of the electron • generate different contact operator at low energies ˜ e LNV = C 1 e − O 1 = ¯ Q ⌧ + d ¯ Q ⌧ + d ¯ L e ff LL C Λ 5 O 1 +h . c . , F X see e.g. M. Ramsey-Musolf, T. Peng and P . Winslow, 2015 F e − for thorough LHC collider phenomenology analysis (and see M. Ramsey Musolf’s talk) ˜ e u • R-M P W include leading 2 pion interactions and RGE d analysis, backgrounds, detector sim. • and determine signal acceptances - very model- dependent
Sidebar: Acceptance is model-dependent E.g.Monojet bounds on Non-standard Neutrino Interactions (A. Friedland, MG, I. Shoemaker, L. Vecchi, ’12) q/q g q/q g q/q g ν α ν α ν α q/q ν β q/q ν β q/q ν β Z’ model For fixed cuts, weaker limit for lighter mediator • can’t just use reported sigma*BR, common to ν ν ν many 0nubb <-> LHC comparisons • need to determine acceptance for your ν ν ν favorite model 10 1 10 0 CDF ADD l o Broad resonance w v CDF GSNP P e 10 0 T 10 - 1 r y H C i g D h F P LHC lowPT T acceptance G S N 10 - 2 10 - 1 P CDF ADD ∂ LHC highPT 10 - 3 h i g h P T 10 - 2 LHC veryhighPT 10 - 4 10 - 3 10 0 10 1 10 2 10 3 10 4 10 5 10 0 10 1 10 2 10 3 10 4 M Z ' @ GeV D M Z ' @ GeV D
BSM contributions to neutrinoless beta decay e- e- High Energy d d u u e- e- n n p p e- e- Low existing and Energy A’ next-gen-multi-tonne A’ experiments A A
Dimension 7 Δ L =2 Nice figures from E. Mereghetti, LNV operators INT seminar 2017 e - e - d e - e - ε ij ε mn L T i C ( D µ L ) j H m ( D µ H ) n ε ij ¯ d γ µ u L T i C ( D µ L ) j u e - e - ν ν e - d e - ε ij ε mn ¯ dL i Q T j CL m H n ε ij ε mn L T i C γ µ e H j H m ( D µ H ) n u ν ν Sample dimension -5,-7,-9 Δ L =2 LNV operators W R W R ν R ν R ν R W R e - d ν e - e - ν u ν
Dimension 7 Δ L =2 Nice figures from E. Mereghetti, LNV operators INT seminar 2017 e - e - d e - e - ε ij ε mn L T i C ( D µ L ) j H m ( D µ H ) n ε ij ¯ d γ µ u L T i C ( D µ L ) j u e - e - ν ν e - d e - ε ij ε mn ¯ dL i Q T j CL m H n ε ij ε mn L T i C γ µ e H j H m ( D µ H ) n u ν ν Sample dimension -5,-7,-9 Δ L =2 LNV operators W R W R ν R ν R ν R W R e - d ν e - Part 1 e - ν u ν
Dimension 7 Δ L =2 Nice figures from E. Mereghetti, LNV operators INT seminar 2017 e - e - d e - e - ε ij ε mn L T i C ( D µ L ) j H m ( D µ H ) n ε ij ¯ d γ µ u L T i C ( D µ L ) j u e - e - ν ν e - d e - ε ij ε mn ¯ dL i Q T j CL m H n ε ij ε mn L T i C γ µ e H j H m ( D µ H ) n u ν ν Sample dimension -5,-7,-9 Δ L =2 LNV operators W R W R ν R ν R ν R W R e - d ν e - e - ν u ν Part 2
Disclaimer/Philosophy for new physics scenarios for neutrinoless double beta decay • Will use effective field theory to study connection between high-energy (below Δ L=2 mass scale) and 0nubb experiments (low-energy) • Plug-in favorite UV model to matching condition of Wilson coefficients • But it would be nice if favorite UV model had some other compelling feature (Feynman) • Theoretical inputs: - (pQCD) anomalous dimensions of operators - lattice inputs to QCD matrix elements (becoming increasingly under control) - nuclear matrix elements of nucleon operators • Neutrino mass generation may be sub-dominant to 0nubb experimental signal (see Michael Ramsey-Musolf’s talk)
BSM contributions to neutrinoless beta decay Model -> gauge e- e- High invariant operators Energy d d u u RG evolution Match at EW scale RG evolution to QCD scale e- e- Match onto chiral EFT n (lattice input for LEC) n p p e- e- Low Neutrino potentials, Energy A’ nuclear matrix element A’ A A
Effective field theory analysis of BSM contributions to neutrinoless double beta decay • new particles generating Δ L=2 processes have masses in multi-TeV scale. • 0nubb process generated at very short distances. • Leading effects of such TeV scale physics can be described by series of Δ L=2 violating operators involving only quarks and leptons c d Λ d − 4 O ( d ) X i L eff = L SM + L ν ,M + i i,d> 4 e.g., dd → uue − e − (collider signal: Keung, Senjanovic, PRL, 1983)
At “low energy” - ie QCD scale - there are a number of “short distance” operators that contribute to neutrinoless double beta decay (Prezeau, Ramsey-Musolf and Vogel (PRD, 68, 2003)) " X # 1 ee c + c 0 X c i,V O µ e γ 5 e c � e γ µ γ 5 e c � L e ff = c i,S ¯ O i + ¯ i,S ¯ i Λ 5 LNV i =vector i =scalar What is a minimal basis (MG, arXiv:1606.04549) ? • leading Δ L=2 operator with two charged leptons has a minimum of 4 quarks, in other words, dimension 9 • For Δ L=2 phenomenology (e.g., 0nubb decay rates) need to know a minimal basis of operators, the set of relevant operators that cannot be reduced by Fierz operators • Electromagnetic invariance: 24 (compared to 14=2*5+4 in prior literature): 8 scalar and 8 vector 4-quark operators • Electroweak invariance: If scale Λ of Δ L=2 violating physics is much larger than the electroweak scale, effect of Δ L=2 physics appears as a series of higher dimension operators invariant under the full Standard Model gauge symmetry • If color + electroweak invariance is imposed, then 11 operators at LO in v/ Λ : 7 scalar and 4 vector • At hadron colliders, if E << Λ , then collider only probing (color + electroweak invariant) Δ L=2 contact operators. In this “contact limit” can classify their experimental signatures.
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