Tests of nonstandard neutrino interactions NSI Cecilia Lunardini

Tests of non-standard neutrino interactions (NSI) Cecilia Lunardini Institute for Nuclear Theory University of Washington, Seattle

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

New interactions: a possibility n Not excluded by neutrino coupling measurements n Theoretically sensible q New physics new couplings (new gauge bosons, …)

Neutral current, low energy n Neutral current q n Low energy q n neutrino + q, e Momentum transfer << new physics scale 4 -fermion interactions q Flavor changing+flavor preserving NSI

Accelerator limits (direct only) n Direct bounds: CHARM, Nu. Te. V q no SU(2) + charged lepton data Strong in muon sector q Weak in e-tau sector q Zeller et al. , PRL 88, 2002 Vilain et al. , PLB 335, 1994

Neutrino oscillation sensitivity n n NSI contribute to matter effects (MSW)! Example: solar neutrinos q NSI in e-tau sector only

Understanding the survival probability n Regimes: n n Vacuum dominates vacuum mixing Matter dominates NSI mixing n Not zero if NSI are flavor-changing!

The survival probability 1 10 E/Me. V NSI on quarks only, same couplings for u and d Positive coupling: longer step Negative coupling: Flattening

Regeneration in the Earth: day/night q q If small Earth effect can be suppressed by “Large” flavor changing NSI needed

Fit to the data? n Good fit needs: q q ~ 30% survival of 8 B Flat SK and SNO spectrum n n 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 n Bounds on NSI q q NSI on quarks. Fit of n n n 2002 Kam. LAND data + BP 04 model+ solar Cl, Ga rates, SK-ES, SNO daynight (phase I) SNO rates (phase II), neutral current SNO free parameter (modified by NSI) e 11=0, A=1 , -0. 32 <eu 12<0. 14 90% C. L. -0. 19 <eu 12<0. 11 90% C. L. Best for flat spectrum eu 12 < -0. 08 new solution!

Results/2 : a new solution! n LMA-0 : Day/Night suppressed by (q - a)~ 0. 15 eu 11=ed 11=-0. 065 ; eu 12 = ed 12=-0. 15 LMA-II c 2 = 79. 9 LMA-I c 2 = 79. 6 LMA-0 a=0. 41 c 2 = 81. 7 90, 95, 99. 73% C. L.

LMA-1 and LMA-0 : (Best-fit parameters taken) n Large effects at medium energy! 8 B

Update with Kam. LAND 2004 data n Only minor changes q LMA-D excluded by atmospheric neutrinos

LMA-1 and LMA-0 compatible with atmospheric+K 2 K+MINOS n Section of 3 D region at eee=-0. 15 (others marginalized) ; inverted hierarchy c 2 min=48. 50 for no NSI n Contours: c 2 - c 2 min=7. 81, 11. 35, 18. 80 (95%, 99%, 3. 6 s) LMA-0 LMA-1

Potential for low energy experiments! n Look for suppression of Be 7 and pep fluxes

NSI at LENS Plot courtesy of C. Grieb See Grieb & Raghavan, hep-ph/0609030

n Look for distortions in the shape of the survival probability at intermediate E q Lack of upturn below SK/SNO threshold 1 10 E/Me. V

FAQs n How large NSI are needed? q n Are these values natural? q n Not very… but possible Can these effects be mimicked by other physics? q n About 10% of standard coupling per each component of matter (electrons, u, d, quarks) yes: sterile neutrinos, noise in solar matter, mass varying neutrinos Can other experiments test this? q Neutrino factories, LBL beams, Kam. LAND high statistics (LMA-0)

Conclusions n Possible large neutral current NSI of neutrinos in the e-tau sector q n allowed by all existing experiments (accelerators, neutrino oscillations exp. ) Large NSI could have tiny effects where we have looked so far! q little effect on current solar data (8 B), on atmospheric neutrinos and on short-medium baseline neutrino beams (MINOS)

n But could appear dramatically in lower energy solar neutrino data! q q n Different shape of probability Suppression of 7 Be, pep Win-win game for low energy detectors! q q Negative result? best constraint on NSI Positive result? Another evidence of new physics in neutrinos n Different vacuum oscillations parameters (solar mass splitting smaller, atmospheric mixing not maximal)?