3+1 sterile neutrino @NuFact

3+1 sterile neutrino @NuFact

Jacobo López–Pavón

IFT UAM/CSIC

NuFlavourCoseners House, Abingdon, UK

8-10 June, 2009

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 shown for other NP cases. For this reason we will call him:

• 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%CLA bit better

Without correlated systematic error Uncorrelated+correlated

systematics (conservative)

Signals

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

NuFact 50 GeV

24 5º

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.

202 10

205 10

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 (hep-ph/0703098). 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 achived if we are able to improve the tau detectors (“Discovery channel” has nice statistics).

NuFact 20 GeV

º14º8

Back-up slides

Probabilities Golden&Silver

8

6

6


99% CL

24 34 3 132 sin sinN N s s


L=3000 km

L=7500 km

NuFact 50 GeV


99% CL

24 34 3 132 sin sinN N s s


Disappearence L=3000 km

DiscoveryL=3000 km

NuFact 50 GeV

Disappearence3000+7500 km Discovery

L=7500 kmDiscovery

3000+7500 km


99% CL

24 34 3 132 sin sinN N s s


Disappearence L=3000 km

DiscoveryL=3000 km

NuFact 50 GeV

Disappearence3000+7500 km Discovery

L=7500 kmDiscovery

3000+7500 km

• 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.


Discrimination between 3 and 4 family Disappearence & Discovery

90%CL

Discrimination between 3 and 4 family Golden & Silver


90%CL

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

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

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


90%CLNuFact 50 GeV

2242 ...s


90%CLNuFact 50 GeV

2242 ...s


90%CLNuFact 50 GeV

2242 ...s

Probabilities mu/tau sector 14 13 0

Improving tau detection

Improving tau detection


NuFact 50 GeV

90%CL

• Sensitivity to : it is not improved the present bound14

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

13

Golden

Golden+Silver


90%CL

• Sensitivity to : it is not improved the present bound 14

• Sensitivity to similar to the standard analyses. 13

NuFact 20 GeV

Golden

Golden+Silver

Documents

3+1 sterile neutrino @NuFact