Tests of non-standard neutrino interactions (NSI)

Cecilia Lunardini

Institute for Nuclear Theory

University of Washington, Seattle

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Non Standard neutrino-matter Interactions Accelerator limits Neutrino oscillation sensitivity NSI effects on solar neutrinos Ideas for low energy experiments

New interactions: a possibility Not excluded by neutrino coupling

measurements

Theoretically sensible New physics new couplings (new gauge

bosons, …)

Neutral current, low energy

Neutral current neutrino + q,e neutrino + q,e

Low energy Momentum transfer << new physics scale

4-fermion interactions Flavor changing+flavor preserving NSI

Accelerator limits (direct only) Direct bounds: CHARM, NuTeV

no SU(2) + charged lepton data Strong in muon sector

Weak in e-tau sector

Zeller et al., PRL 88, 2002Vilain et al., PLB335, 1994

Neutrino oscillation sensitivity NSI contribute to matter effects (MSW)! Example: solar neutrinos

NSI in e-tau sector only

Understanding the survival probability Regimes:

Vacuum dominates vacuum mixing Matter dominates NSI mixing

Not zero if NSI are flavor-changing!

The survival probability

E/MeV

Positive coupling: longer step

Negative coupling: Flattening

101

NSI on quarks only, same couplings for u and d

Regeneration in the Earth: day/night

If Earth effect can be suppressed by small

“Large” flavor changing NSI needed

07.0)22sin(tan)(

)(2

Earth

A

DayNight

DayNight

)(

Fit to the data?

Good fit needs: ~ 30% survival of 8B Flat SK and SNO

spectrum No indication of upturn at

lower E No evidence of Earth

matter effect (< ~ 7%)

favored

Small mass splitting possible for small )(

Results of data analysis/1 Bounds on NSI

NSI on quarks. Fit of

2002 KamLAND data + BP04 model+ solar Cl, Ga rates, SK-ES, SNO day-night

(phase I) SNO rates (phase II), neutral current SNO free parameter (modified by NSI)

11=0, -0.32 <u12<0.14 90% C.L.

1 , -0.19 <u12<0.11 90% C.L.

u12 < -0.08 new solution!

Best for flat spectrum

LMA-0

LMA-I

LMA-II

0.41

Results/2 : a new solution!

LMA-0 : Day/Night suppressed by ( - )~ 0.15 u

11=d11=-0.065 ; u

12 = d12=-0.15

90,95,99,99.73% C.L.

2 = 79.6

2 = 79.9

2 = 81.7

LMA-1 and LMA-0 : Large effects at medium energy!

8 B

(Best-fit parameters taken)

Update with KamLAND 2004 data Only minor changes

LMA-D excluded by atmospheric neutrinos

LMA-1 and LMA-0 compatible with atmospheric+K2K+MINOS Section of 3D

region at e=-0.15 (others marginalized) ; inverted hierarchy

2min=48.50 for no

NSI

Contours: 2 - 2

min=7.81, 11.35, 18.80 (95%,99%, 3.6 )

LMA-0

LMA-1

Potential for low energy experiments! Look for suppression of Be7 and pep fluxes

NSI at LENS

See Grieb & Raghavan, hep-ph/0609030

Plot courtesy of C. Grieb

Look for distortions in the shape of the survival probability at intermediate E Lack of upturn below SK/SNO threshold

E/MeV101

FAQs

How large NSI are needed? About 10% of standard coupling per each component of

matter (electrons, u,d, quarks) Are these values natural?

Not very… but possible Can these effects be mimicked by other physics?

yes: sterile neutrinos, noise in solar matter, mass varying neutrinos

Can other experiments test this? Neutrino factories, LBL beams, KamLAND high statistics

(LMA-0)

Conclusions

Possible large neutral current NSI of neutrinos in the e-tau sector allowed by all existing experiments (accelerators,

neutrino oscillations exp.)

Large NSI could have tiny effects where we have looked so far! little effect on current solar data (8B), on

atmospheric neutrinos and on short-medium baseline neutrino beams (MINOS)

But could appear dramatically in lower energy solar neutrino data! Different shape of probability Suppression of 7Be, pep

Win-win game for low energy detectors! Negative result? best constraint on NSI Positive result? Another evidence of new

physics in neutrinos Different vacuum oscillations parameters (solar mass

splitting smaller, atmospheric mixing not maximal)?