NSI versus NU at the Neutrino Factory

1. NSI versus NU at the Neutrino Factory Euronu meeting Strasbourg June 2-4, 2010Walter Winter Universität Würzburg TexPoint fonts used in EMF: AAAAAAAA

2. Contents • Introduction:New physics from heavy mediators • Non-standard interactions (NSI) • Non-unitarity (NU) • NU versus NSI at the NuFact • Summary • Based on „Non-standard interactions versus non-unitary lepton flavor mixing at a neutrino factory“ by Davide Meloni, Tommy Ohlsson, Walter Winter, He Zhang, JHEP 04 (2010) 041, arXiv:0912.2735 [hep-ph] , EURONU-WP6-09-14

3. New physics from heavy mediators • Effective operator picture if mediators integrated out:Describes additions to the SM in a gauge-inv. way! • BEYOND NEUTRINO MASS:Interesting leptonic dimension six operatorsFermion-mediated  Non-unitarity (NU)Scalar- or vector-mediated Non-standard int. (NSI) n mass d=6, 8, 10, ...: NSI, NU

4. Non-standard interactions • Typically described by effective four fermion interactions (here with leptons) • May lead to matter NSI (for g=d=e) • May also lead to source/detector NSI(e.g. NuFact: embNF for a=d=e, g=m) These source/det.NSI are process-dep.!

5. Lepton flavor violation… and the story of SU(2) gauge invariance • Strongbounds Ex.: NSI(FCNC) 4n-NSI(FCNC) CLFV e m ne nm ne nm ne ne e e e e • Affects neutrino oscillations in matter (or neutrino production) • Affects environments with high n densities (supernovae) BUT: These phenomena are connected by SU(2) gauge invariance • Almost impossible to construct a model for large (O(0.1)) leptonic matter NSI with d=6 operators (Bergmann, Grossman, Pierce, hep-ph/9909390; Antusch, Baumann, Fernandez-Martinez, arXiv:0807.1003; Gavela, Hernandez, Ota, Winter,arXiv:0809.3451) • Even with d=8 effective operators, constructing a model with large NSI is not trivial! • This talk: Focus on „small“ O(0.01) – O(0.001) effects

6. d=6 NSI without CLFV • At d=6: Simplest possibility is operator of the type • Without cancellations: Singly charged scalar is the only possible mediatorNo CLFV: • d=6 NSI without CLFV imply, in general (even with loops): Feynman diagrams Projection on basis (Gavela, Hernandez, Ota, Winter, 2008)

7. Current bounds and measurements at NuFact • Compared to the model-independent bounds, the bounds for the scalar-mediated d=6 operators are strong (e.g. from lepton universality tests)(Antusch, Baumann, Fernandez-Martinez, arXiv:0807.1003; Biggio, Blennow, Fernandez-Martinez, arXiv:0907.0097) • A ntnear detector at NuFact would help to improve these by a factor of a few ND5: OPERA-like ND at d=1 km, 90% CL (Tang, Winter, arXiv:0903.3039)

8. Non-unitarity of mixing matrix • Integrating out heavy fermion fields (such as in a type-I TeV see-saw), one obtains neutrino mass and the d=6 operator (de Gouvea et al, 2002; Abada et al, 2007) • Re-diagonalizing and re-normalizing the kinetic terms of the neutrinos, one has(Broncano, Gavela, Jenkins, 2003; Antusch et al, 2006) • This can be described by an effective (non-unitary) mixing matrix e with N=(1+e) U • Similar effect to NSI, but source, detector, and matter NSI are correlated in a particular, fundamental way (i.e., process-independent)

9. Impact of near detector • Example: (Antusch, Blennow, Fernandez-Martinez, Lopez-Pavon, arXiv:0903.3986) • nt near detector important to detect zero-distance effect Curves: 10kt, 1 kt, 100 t, no ND

10. NU versus NSI (d=6) Distinguish two classes of d=6 non-standard effects (NSE) without CLFV: • Fermion-mediated leptonic d=6 operator (NU, OF) • Particular correlation among source, propagation, detection effects • Experiment-independent: appear at NuFact + Superbeam! • Scalar-mediated leptonic d=6 operator (NSI, OS) • At tree level, no cancellations: Only mediated by scalars • Leads to source NSI at NuFact (not superbeam) and matter NSI • Can one identify these/distinguish these? • Theory: Can one distinguish between fermions and scalars as heavy mediators (simplest interpretation)? NB: These two are the only classes of d=6 operators leading to NSE without CLFV Hadronic NSI: not possible to cancel CLFV independentlyAntusch, Blennow, Fernandez-Martinez, Ota, arXiv:1005.0756

11. CorrelationsSource – propagation - detection • OF (for ordinary matter with Np = Nn)Forbidden:(see e.g. Fernandez-Martinez, Gavela, Lopez-Pavon, Yasuda, 2007; Antusch, Baumann, Fernandez-Martinez, 2008) • OS(without CLFV)Forbidden:… and no detector effects (leptonic NSI)!(Gavela, Hernandez, Ota, Winter, 2008) • Other: No particular correlations, all effects allowed

12. NuFact versus Superbeam • One can exclude by the discovery of certain effects • Maybe most interesting: (Meloni, Ohlsson, Winter, Zhang, 2009)

13. Example: emt • Relationships:OF: OS: • Probability difference:(Kopp, Lindner, Ota, Sato, 2007 vs. Antusch, Blennow, Fernandez-Martinez, Lopez-Pavon, 2009; see Meloni, Ohlsson, Winter, Zhang, 2009) • Consequence: Difference depends on NSI CP-phase • If nt appearance channel (SBL, NuFact) Not in Superbeam

14. Pheno consequences (NF) • Difficult to disentangle with NuFact alone  Use superbeam? ND-L: OPERA-like at 1km (Meloni, Ohlsson, Winter, Zhang, 2009)

15. Distinguishing NSI from NU • Can hardly distinguish with NuFact alone in region beyond current bounds • Need Superbeam exp. with sensitivity emt << 10-3 (90% CL) (Meloni, Ohlsson, Winter, Zhang, 2009)

16. Summary • There is a physics case for a NuFact nt near detector for NSI, NU • For NSE from d=6 effective operators without CLFV certain correlation between source and propagation effects exist • For NuFact, because of the neutrino production by muon decays, these are partly similar for NSI and NU, which makes it hard to distinguish these effects • An independent measurement at a superbeam could lift this ambiguity • At d=6, the simplest interpretation of „NSI versus NU“ is: „Scalar versus fermion as heavy mediator“