3+1 sterile neutrino @NuFact

Jacobo López–Pavón

IFT UAM/CSIC

NuFact 09@ IIT, Chicago, July 20-25

Based on a Based on a collaboration with: with:

Andrea Donini, Ken-ichi Fuki, Davide MeloniAndrea Donini, Ken-ichi Fuki, Davide Meloniand and

Osamu YasudaOsamu Yasuda

e-Print: [arXiv:0812.3703]e-Print: [arXiv:0812.3703]

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:

2

i

ii

dMM Y

d

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.

EWM

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 detectors @ L=3000 km and L=7500 km Both polarities running for 4 years each

202 10

VS

205 10

• 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

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

2 0solm 1 disappears

It reduces to the standardcase if sterile neutrinodecauple

Can be put anywhere

Since we are interested in the atmospheric regime, ,Let us take advantage of the following parametrization:

Probabilities in matterExpanding with respect the following small parameters…

New possible CP-violation Signal !

Best sensitivity to 34 24,

Golden and Silver do not seem to be the best option to study sterile neutrinos

23 421

2

m L

E

Probabilities in matter• Golden and Silver seems to be not so useful for constraint sterileNeutrino 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 07Tosihiko Ota, Joe Sato 02

• In anycase, we have analyzed all the possible channels

Sensitivities

Sensitivity to : Golden and Silver channels13 14,

NuFact 50 GeV90%CL

• Sensitivity to : it is not improved the present bound14

• Sensitivity to similar to the standard analyses: long baseline better.

13

NuFact 20 GeVA bit better

Golden

Golden+Silver

Sensitivity to : disappearence & discovery 24 34,

NuFact 50 GeV NuFact 20 GeV

90%CL better

Without correlated systematic error Uncorrelated+correlated

systematics (conservative)

Uncorrelated Sensitivities 90%CL

NuFact 50 GeV

24

34 º12

º7.5

Present

º31

º12

14º9.5º9.5

NuFact 20 GeV

º14

º8º9.5

CP violationsignals

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.24 14,

99%CLGolden + Silver

NuFact 50 GeV

Measurement of the standard 3-family phase

Combination

L=3000 km

L=7500 km

Standard analyses

• Some sensitivity @ the “Magic Baseline” Sterile neutrino effect !

99%CLGolden + 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 to3-family ones.

13 14,

• The sensitivity @ 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?

?e ?e ?

New possible CP-violationEffect!!

•

• Golden & Silver probabilities are very suppressed by small parameters:

The new CP phase can be probed

99% CL

24 34 3 312 sin sinN N s s

1. Confusion between 31( )sign sign

L=3000 km

L=7500 km

24 5º

NuFact 50 GeV

99% New CP-phase ( ) discovery potencial

+

NuFact 50 GeV

50% CP-coverage 80% CP-coverage

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 parametersassociated 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!

202 10

205 10

13

24 14, 13

ConclusionsNuFact 50 GeV

24

34 º12º7.5

Present

º31º12

• 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”.

24 34

• 50 GeV NuFact performs better than the ISS scenario due to the larger taucross 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

º14º8

Back-up slides

Dependence of sensitivity in systematic errors

Mass/kton

correlated systematicsin normalization

bin-to-bin uncorrelatederror

• 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 systematicsin normalization

bin-to-bin uncorrelatederror

• 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 becauseThe 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

64 4 14 24 ( )eU U s s o

54 4 14 34 ( )eU U s s o

Sensitivity to special combinations of the parameter space

• Once we choose the most suitable set of independent parameters:

Golden

Silver

14 24 14 24 34, / , , ...s s s s s

14 34 14 34 24, / , , ...s s s s s

one obtains very nice sensitivities to these combination of parameters.

NuFact 50 GeV NuFact 20 GeV

Sensitivity to : Golden + Silver4 4eU U

90%C.L.

Much better because the higher statistics Notice, different scale.

NuFact 50 GeV NuFact 20 GeV

Sensitivity to : Golden + Silver4 4eU U

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/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)

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.

610

• Silver & Discovery: ArXiv:0704.0388

ArXiv: hep-ph/0305185

5NC10 N

x 5

where

analyses2

• Sensitivities

Correlated systematic errors

max min/jE E E

analyses2

Uncorrelated bin-to-bin systematic errors

With given just above.

• Signal

j

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

8

6

6

The new CP phase can be probed

99% CL

24 34 3 132 sin sinN N s s

1. Confusion between 13( )sign sign

L=3000 km

L=7500 km

NuFact 50 GeV

The new CP phase can be probed

99% CL

24 34 3 132 sin sinN N s s

1. Confusion between 13( )sign sign

Disappearence L=3000 km

DiscoveryL=3000 km

NuFact 50 GeV

Disappearence3000+7500 km Discovery

L=7500 kmDiscovery

3000+7500 km

The new CP phase can be probed

99% CL

24 34 3 132 sin sinN N s s

1. Confusion between 13( )sign sign

Disappearence L=3000 km

DiscoveryL=3000 km

NuFact 50 GeV

Disappearence3000+7500 km Discovery

L=7500 kmDiscovery

3000+7500 km