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Tests of non-standard neutrino interactions (NSI)

Tests of non-standard neutrino interactions (NSI). Cecilia Lunardini Institute for Nuclear Theory University of Washington, Seattle. Menu. N on S tandard neutrino-matter I nteractions Accelerator limits Neutrino oscillation sensitivity NSI effects on solar neutrinos

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Tests of non-standard neutrino interactions (NSI)

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

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

  3. New interactions: a possibility • Not excluded by neutrino coupling measurements • Theoretically sensible • New physics  new couplings (new gauge bosons, …)

  4. 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

  5. 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, 2002 Vilain et al., PLB335, 1994

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

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

  8. 1 10 The survival probability E/MeV NSI on quarks only, same couplings for u and d Positive coupling: longer step Negative coupling: Flattening

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

  10. 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

  11. 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) e11=0, -0.32 <eu12<0.14 90% C.L. • A=1 , -0.19 <eu12<0.11 90% C.L. eu12 < -0.08 new solution! Best for flat spectrum

  12. LMA-II LMA-I LMA-0 c2 = 79.9 a=0.41 c2 = 79.6 c2 = 81.7 Results/2 : a new solution! • LMA-0 : Day/Night suppressed by (q - a)~ 0.15 eu11=ed11=-0.065 ; eu12 = ed12=-0.15 90,95,99,99.73% C.L.

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

  14. Update with KamLAND 2004 data • Only minor changes • LMA-D excluded by atmospheric neutrinos

  15. LMA-1 and LMA-0 compatible with atmospheric+K2K+MINOS • Section of 3D region at eee=-0.15 (others marginalized) ; inverted hierarchy • c2min=48.50 for no NSI • Contours: c2 - c2min=7.81, 11.35, 18.80 (95%,99%, 3.6 s) LMA-0 LMA-1

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

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

  18. 1 10 E/MeV • Look for distortions in the shape of the survival probability at intermediate E • Lack of upturn below SK/SNO threshold

  19. 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)

  20. 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)

  21. 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)?

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