3+1 sterile neutrino @NuFact

1. Jacobo López–Pavón IFT UAM/CSIC 3+1 sterile neutrino @NuFact NuFact 09 @ IIT, Chicago, July 20-25

2. Based on a collaboration with: Andrea Donini, Ken-ichi Fuki, Davide Meloni and Osamu Yasuda e-Print: [arXiv:0812.3703]

3. Motivations • Neutrino masses and mixing → evidence of Physics Beyond the SM • Sterile neutrinos stronglyaffect the oscillation physics • This is what LSND seems to indicate: the existence of a fourth sterile neutrino, much heavier than the rest light neutrinos. • Experiments such as MiniBoone do not confirm the LSND results. • Difficult to accommodate all oscillation data including LSND in 4 neutrino models. Tension remains in 3+2 and 3+3 models.

4. Motivations • Sterile neutrino scenarios which satisfy all neutrino oscillation data except LSND are still possible. • Many theories of NP have in their low energy spectrum singlet fermions. • The simplest extension to account for neutrino masses: SM + singlet fermions with a Majorana mass term. Following the renormalization group analyses, M can be anything: as it is dictated by chiral symmetry. If M is small, lepton number is partially conserved: this range of values is natural. Motivation for not assuming as usual.

5. Goals We will analyze the future sensitivity to the new parameters associated to the 3+1 sterile model in a NuFact, without imposing LSND constraints but considering the information from the rest of present experiments. Study of CP violation in the context of sterile neutrino

6. Set-up • 50 GeV NuFact useful muon decays/year/baseline Hybrid-MIND detectors @ L=3000 km and L=7500 km Both polarities running for 4 years each • 20 GeV NuFact (ISS scenario) • useful muon decays/year/baseline • Hybrid-MIND detectors @ L=4000 km and L=7500 km • Both polarities running for 4 years each 4kton MECC + 50kton MIND VS 4kton MECC + 50kton MIND

7. Why we consider this set up? It is well known that the higher energy we have, the better we can explore the New Physics. An evident motivation: the channel is a very interesting one to study New Physics.

8. Parametrization disappears Since we are interested in the atmospheric regime, , Let us take advantage of the following parametrization: Can be put anywhere It reduces to the standard case if sterile neutrino decauple

9. Best sensitivity to Probabilities in matter Expanding with respect the following small parameters… Golden and Silver do not seem to be the best option to study sterile neutrinos New possible CP-violation Signal !

10. Golden and Silver seems to be not souseful for constraint sterile • Neutrino physics. • We will focus on the sector. At the probability level, we can say • is the best channel to see a possible sterile signal, moreover, is • the best one to see the new CP-violation associated. • This can be show in general for generic NP (as NSI or the MUV scheme, • hep-ph/0703098). For this reason we will call him: • E.Fernandez-Martinez, M.B.Gavela, J.Lopez-Pavon,O. Yasuda 07 • Tosihiko Ota, Joe Sato 02 Probabilities in matter • In anycase, we have analyzed all the possible channels

11. Sensitivities

12. Sensitivity to : Golden and Silver channels Golden Golden +Silver NuFact 50 GeV NuFact 20 GeV 90%CL A bit better • Sensitivity to similar to the standard analyses: long baseline better. • Sensitivity to : it is not improved the present bound

13. Sensitivity to : disappearence & discovery Without correlated systematic error Uncorrelated+correlated systematics (conservative) NuFact 20 GeV NuFact 50 GeV 90%CL better

14. Uncorrelated Sensitivities 90%CL Present NuFact 50 GeV NuFact 20 GeV

15. CP violation signals

16. Can the measurement of the 3-family Dirac phase be affected by the sterile neutrinos ?

17. Measurement of the standard 3-family phase L=7500 km L=3000 km Combination Standard analyses NuFact 50 GeV Golden + Silver 99%CL • For small values of almost no differences with 3-family case.

18. Measurement of the standard 3-family phase L=7500 km Standard analyses Combination L=3000 km NuFact 50 GeV Golden + Silver 99%CL Sterile neutrino effect ! • Some sensitivity @ the “Magic Baseline”

19. Mesurement of the standard 3-family phase • For small values of no differences with 3-family case. • Close to the upper bound, 3+1 contourns are orthogonal to • 3-family ones. Competitive • The sensitivity @ L=7500 km would be a sterile physics effect.

20. Could we measure the new phases ?

21. Can we measure the new phases ? Which would be the best channel? • Golden & Silver probabilities are very suppressed by small parameters: New possible CP-violation Effect!!

22. 1. Confusion between The new CP phase3 can be probed L=3000 km L=7500 km NuFact 50 GeV 99% CL

23. + 99% New CP-phase (3 ) discovery potencial 80% CP-coverage 50% CP-coverage NuFact 50 GeV

24. Conclusions • Analyze 3+1 neutrino sterile physics @ NuFact. Comparing two set-ups: - E=50 GeV; useful muon decays/year/baseline; Hybrid-MIND detectors @ L=3000 km and L=7500 km. • - E=20 GeV; useful muon decays/year/baseline; Hybrid-MIND • detectors @ L=4000 km and L=7500 km (ISS scenario). • Golden & Silver results not very useful to constrain the new parameters associated to the 3+1 sterile neutrino model. • The sensitivity to is basically the same as the 3-family analyses one. • For small values of measurement of is not affected by • sterile neutrinos. Saturating the bounds there is some sensitivity to • CP-violation @ L=7500 km, Sterile neutrino effect!

25. Conclusions Present NuFact 50 GeV NuFact 20 GeV • 50 GeV NuFact performs better thanthe ISS scenario due to the larger tau • cross section. Nice sensitivities to and thanks to the sector • Better results can be obteined if we are able improve the tau detectors • (remember, “Discovery channel” has nice statistics). • CP-asymmetry is a clean probe of the new phases. This is not new, can be seen for New Physics as NSI or the MUV scheme. For this reason we call this channel the “Discovery channel”.

26. Back-up slides

27. Dependence of sensitivity in systematic errors 90%CL NuFact 20 GeV Mass/kton bin-to-bin uncorrelated error correlated systematics in normalization • An increase of MECC mass from 4 kton to 8 kton only improves marginally • the sensitivity. • The bin-to-bin uncorrelated error is the more important factor to improve • the performance of the discovery channel.

28. Dependence of sensitivity in systematic errors 90%CL NuFact 50 GeV Mass/kton bin-to-bin uncorrelated error correlated systematics in normalization • Less demanding than the ISS set-up because • The higher energy. • An increase of MECC mass from 4 kton to 8 kton only improves marginally • the sensitivity. • The bin-to-bin uncorrelated error is the more important factor to improve • the performance of the discovery channel.

29. Sensitivity to special combinations of the parameter space • Golden & Silver have poor senstivity to the new angles, but not so to specific • combinations of them. • From the vacuum formula, one naively expects: • Golden • Silver

30. Sensitivity to special combinations of the parameter space • Once we choose the most suitable set of independent parameters: • Golden • Silver one obtains very nice sensitivities to these combination of parameters.

31. Sensitivity to : Golden + Silver NuFact 20 GeV NuFact 50 GeV Much better because the higher statistics Notice, different scale. 90%C.L.

32. Sensitivity to : Golden + Silver NuFact 50 GeV NuFact 20 GeV Similar reults for both energies. 90%C.L.

33. Discrimination between 3 and 4 family Golden & Silver 90%CL NuFact 20 GeV NuFact 50 GeV

34. Discrimination between 3 and 4 family Disappearence & Discovery 90%CL NuFact 20 GeV NuFact 50 GeV

35. Experimental details: Detector Efficiencies Placed in front of MIND • HybridMIND=4kton MECC+50kton MIND • MIND (ISS detector report) above 10 GeV Increasing linearly from at 1 GeV above 1 GeV (the MINOS one) • MECC (Magnetized Emulsion Cloud Chamber) above 5 GeV ArXiv: hep-ph/03051805 x 5, thanks to magnetization decays into e and into hadrons can be used in addition to decay (only the 17% of the total)

36. Experimental details: Backgrounds & Systematics • Golden: B= dominated by right-sign muons with wrong charge assigment and charmed meson decays . • Disappearence: B= negligible. Systematic-dominated. We’ve checked this including B= , all wrong-sign muon events and right-sign muons coming form discovery oscillaton with tau decaying into muons. • Silver & Discovery: ArXiv:0704.0388 ArXiv: hep-ph/0305185 x 5

38. analyses • Sensitivities where Correlated systematic errors

39. analyses Uncorrelated bin-to-bin systematicerrors • Signal With given just above.

40. Discrimination between 3 and 4 family Where is the prior from the 3+1 sterile oscillation Analyses of atmospheric and reactor data.

41. Probabilities Golden&Silver

42. 1. Confusion between The new CP phase3 can be probed L=3000 km L=7500 km NuFact 50 GeV 99% CL

43. 1. Confusion between The new CP phase3 can be probed Disappearence L=3000 km Disappearence 3000+7500 km Discovery L=7500 km Discovery 3000+7500 km NuFact 50 GeV Discovery L=3000 km 99% CL

44. 1. Confusion between The new CP phase3 can be probed Disappearence L=3000 km Disappearence 3000+7500 km Discovery L=7500 km Discovery 3000+7500 km NuFact 50 GeV Discovery L=3000 km 99% CL