NSI versus NU at the Neutrino Factory

Euronu meetingStrasbourgJune 2-4, 2010

Walter WinterUniversität Würzburg

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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

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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

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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.!

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Lepton flavor violation… and the story of SU(2) gauge invariance

Strongbounds

e e

e

NSI(FCNC)

e e

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/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

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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

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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 near detector at NuFact would help to improve these by a factor of a few

(Tang, Winter, arXiv:0903.3039)

ND5: OPERA-like ND at d=1 km, 90% CL

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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)

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Impact of near detector

Example: (Antusch, Blennow, Fernandez-Martinez, Lopez-Pavon, arXiv:0903.3986)

near detector important to detect zero-distance effect

Curves: 10kt, 1 kt, 100 t, no ND

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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, OF) Particular correlation among source, propagation, detection effects Experiment-independent: appear at NuFact + Superbeam!

2. 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

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CorrelationsSource – propagation - detection

1. OF (for ordinary matter with Np = Nn)

Forbidden:(see e.g. Fernandez-Martinez, Gavela, Lopez-Pavon, Yasuda, 2007; Antusch, Baumann, Fernandez-Martinez, 2008)

2. OS (without CLFV)

Forbidden:… and no detector effects (leptonic NSI)!(Gavela, Hernandez, Ota, Winter, 2008)

3. Other: No particular correlations, all effects allowed

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NuFact versus Superbeam

One can exclude by the discovery of certain effects

Maybe most interesting:

(Meloni, Ohlsson, Winter, Zhang,

2009)

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Example:

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 appearance channel (SBL, NuFact)

Not in Superbeam

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Pheno consequences (NF)

Difficult to disentangle with NuFact alone Use superbeam?

(Meloni, Ohlsson, Winter, Zhang, 2009)

ND-L: OPERA-like at 1km

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Distinguishing NSI from NU

Can hardly distinguish with NuFact alone in region beyond current bounds

Need Superbeam exp. with sensitivity << 10-3 (90% CL)(Meloni, Ohlsson, Winter, Zhang, 2009)

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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 existFor 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“