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

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

Motivations Neutrino masses and mixing → evidence of Physics Beyond the SM Sterile neutrinos strongly affect 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.

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.

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 Goals

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

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.

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

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

Probabilities in matter Golden and Silver seems to be not so useful 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/ ). For this reason we will call him: E.Fernandez-Martinez, M.B.Gavela, J.Lopez-Pavon,O. Yasuda 07 Tosihiko Ota, Joe Sato 02 In anycase, we have analyzed all the possible channels

Sensitivities

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

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

Uncorrelated Sensitivities 90%CL NuFact 50 GeVPresentNuFact 20 GeV

CP violation signals

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

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

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

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. The L=7500 km would be a sterile physics effect. Competitive

Could we measure the new phases ?

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

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

99% New CP-phase (   ) discovery potencial + NuFact 50 GeV 50% CP-coverage 80% CP-coverage

Conclusions Analyze 3+1 neutrino sterile NuFact. Comparing two set-ups: - E=50 GeV; useful muon decays/year/baseline; Hybrid-MIND L=3000 km and L=7500 km. - E=20 GeV; useful muon decays/year/baseline; Hybrid-MIND 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 L=7500 km, Sterile neutrino effect!

Conclusions NuFact 50 GeV Present 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”. 50 GeV NuFact performs better than the 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). NuFact 20 GeV

Back-up slides

Dependence of sensitivity in systematic errors Mass/kton correlated systematics in normalization bin-to-bin uncorrelated error 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. 90%CL NuFact 20 GeV

Dependence of sensitivity in systematic errors Mass/kton correlated systematics in normalization bin-to-bin uncorrelated error 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. 90%CL NuFact 50 GeV Less demanding than the ISS set-up because The higher energy.

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

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.

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

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

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

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

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 Experimental details: Detector Efficiencies Placed in front of MIND ArXiv: hep-ph/ x 5, thanks to magnetization decays into e and into hadrons can be used in addition to decay (only the 17% of the total)

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: ArXiv: hep-ph/ x 5

where analyses Sensitivities Correlated systematic errors

analyses Uncorrelated bin-to-bin systematic errors With given just above. Signal

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

Probabilities Golden&Silver

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

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

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