3+1 sterile neutrino @nufact jacobo lópez–pavón ift uam/csic nufact 09 @ iit, chicago, july...
Post on 20-Dec-2015
216 views
TRANSCRIPT
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