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

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: [hep-ph], EURONU-WP arXiv: [hep-ph]

3  Effective operator picture if mediators integrated out: Describes additions to the SM in a gauge-inv. way!  BEYOND NEUTRINO MASS: Interesting leptonic dimension six operators Fermion-mediated  Non-unitarity (NU) Scalar- or vector-mediated  Non-standard int. (NSI) New physics from heavy mediators 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  =  =e)  May also lead to source/detector NSI (e.g. NuFact:   NF for  =  =e,  =  ) These source/det.NSI are process-dep.!

5 Lepton flavor violation … and the story of SU(2) gauge invariance  Strong bounds ee e  NSI (FCNC) ee e  CLFV e  4 -NSI (FCNC) Ex.: e e  Affects neutrino oscillations in matter (or neutrino production)  Affects environments with high 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/ ; Antusch, Baumann, Fernandez-Martinez, arXiv: ; Gavela, Hernandez, Ota, Winter,arXiv: )  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 mediator No CLFV:  d=6 NSI without CLFV imply, in general (even with loops): (Gavela, Hernandez, Ota, Winter, 2008) Projection on basisFeynman diagrams

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: ; Biggio, Blennow, Fernandez-Martinez, arXiv: )  A  near detector at NuFact would help to improve these by a factor of a few (Tang, Winter, arXiv: ) ND5: OPERA-like ND at d=1 km, 90% CL

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  with N=(1+  ) 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: )   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: 1.Fermion-mediated leptonic d=6 operator (NU, O F )  Particular correlation among source, propagation, detection effects  Experiment-independent: appear at NuFact + Superbeam! 2.Scalar-mediated leptonic d=6 operator (NSI, O S )  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 independently Antusch, Blennow, Fernandez-Martinez, Ota, arXiv:

11 Correlations Source – propagation - detection 1.O F (for ordinary matter with N p = N n ) Forbidden: (see e.g. Fernandez-Martinez, Gavela, Lopez-Pavon, Yasuda, 2007; Antusch, Baumann, Fernandez-Martinez, 2008) 2.O S (without CLFV) Forbidden: … and no detector effects (leptonic NSI)! (Gavela, Hernandez, Ota, Winter, 2008) 3.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:    Relationships: O F : O S :  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  appearance channel (SBL, NuFact) Not in Superbeam

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

15 Distinguishing NSI from NU  Can hardly distinguish with NuFact alone in region beyond current bounds  Need Superbeam exp. with sensitivity   << (90% CL) (Meloni, Ohlsson, Winter, Zhang, 2009)

16 Summary  There is a physics case for a NuFact  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“