Testing neutrino properties at the Neutrino Factory
Astroparticle seminarINFN TorinoDecember 3, 2009
Walter WinterUniversität Würzburg
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Contents
The most prominent “neutrino” property: leptonic CP violation (CPV)
CPV Phenomenology Neutrino factory experiment Near detectors at the Neutrino Factory New physics searches with near
detectors Summary
CPV: Motivation from theory
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Where does CPV enter? Example: Type I seesaw (heavy SM singlets Nc)
Charged leptonmass terms
Eff. neutrinomass terms
Block-diag.
CC
Primary source of CPV(depends BSM theory)
Effective source of CPV(only sectorial origin relevant)
Observable CPV(completely model-indep.)
Could also be type-II, III seesaw,
radiative generation of neutrino mass, etc.
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From the measurement point of view:It makes sense to discuss only observable CPV(because anything else is model-dependent!)
At high E (type I-seesaw): 9 (MR)+18 (MD)+18 (Ml) = 45 parameters
At low E: 6 (masses) + 3 (mixing angles) + 3 (phases) = 12 parameters
Connection to measurement
There is no specific connectionbetween low- and
high-E CPV!
But: that‘s not true for special (restrictive) assumptions!
CPV in 0 decayLBL accessible CPV: If UPMNS real CP conserved
Extremely difficult! (Pascoli, Petcov, Rodejohann, hep-ph/0209059)
Requires 13 > 0
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Why is CPV interesting? Leptogenesis:
CPV from Nc decays
If special assumptions(such as hier. MR, NH light neutrinos, …)
it is possible that CP is the only source of CPV for leptogensis! If CPV discovery: It is
possible to write down a model, in which the baryon asymmetry comes from CP only
(Nc)i (Nc)i
~ MD (in basis where
Ml and MR diagonal)
(Pascoli, Petcov, Riotto, hep-ph/0611338 )Different curves:different assumptions for 13, …
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How well do we need to measure?
We need generic argumentsExample: Parameter space scan for eff. 3x3 case (QLC-type assumptions, arbitrary phases, arbitrary Ml)
The QLC-type assumptions lead to deviations O(C) ~ 13
Can also be seen in sum rules for certain assumptions, such as
(: model parameter) This talk: Want Cabibbo-angle order precision for CP!
(Niehage, Winter, arXiv:0804.1546)
(arXiv:0709.2163)
CPV phenomenology
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Terminology
Any value of CP
(except for 0 and )violates CP
Sensitivity to CPV:Exclude CP-conservingsolutions 0 and for any choiceof the other oscillationparameters in their allowed ranges
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Measurement of CPV
(Cervera et al. 2000; Freund, Huber, Lindner, 2000; Huber, Winter, 2003; Akhmedov et al, 2004)
Antineutrinos: Magic baseline: Silver: Platinum, Superb.:
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Degeneracies
CP asymmetry
(vacuum) suggests the use of neutrinos and antineutrinos
One discrete deg.remains in (13,)-plane
(Burguet-Castell et al, 2001)Burguet-Castell et al, 2001)
Additional degeneracies: Additional degeneracies: (Barger, Marfatia, Whisnant, 2001)(Barger, Marfatia, Whisnant, 2001) Sign-degeneracy Sign-degeneracy
(Minakata, Nunokawa, 2001)(Minakata, Nunokawa, 2001) Octant degeneracy Octant degeneracy
(Fogli, Lisi, 1996)(Fogli, Lisi, 1996)
Best-fit
Antineutrinos
Iso-probability curves
Neutrinos
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Intrinsic vs. extrinsic CPV The dilemma: Strong matter effects (high E, long L),
but Earth matter violates CP Intrinsic CPV (CP) has to be
disentangled from extrinsic CPV (from matter effects)
Example: -transitFake sign-solutioncrosses CP conservingsolution
Typical ways out: T-inverted channel?
(e.g. beta beam+superbeam,platinum channel at NF, NF+SB)
Second (magic) baseline(Huber, Lindner, Winter, hep-ph/0204352)
NuFact, L=3000 km
Fit
True CP (violates
CP maximally)
Degeneracy above 2
(excluded)
True
Critical range
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The magic baseline
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CPV discovery reach … in (true) sin2213 and CP
Sensitive region as a
function of true 13 and CP
CP values now stacked for each 13
Read: If sin2213=10-3, we
expect a discovery for 80% of all values of CP
No CPV discovery ifCP too close to 0 or
No CPV discovery forall values of CP3
~ Cabibbo-angleprecision at 2 BENCHMARK!
Best performanceclose to max.
CPV (CP = /2 or 3/2)
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Next generation reach
Includes Double Chooz, Daya Bay, T2K, NOvA
(Huber, Lindner, Schwetz, Winter, arXiv:0907.1896)
90% CL
Beyond the next generationExample: Neutrino factory
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Neutrino factory:International design study
IDS-NF: Initiative from ~ 2007-
2012 to present a design report, schedule, cost estimate, risk assessment for a neutrino factory
In Europe: Close connection to „Eurous“ proposal within the FP 07
In the US: „Muon collider task force“ISS
(Geer, 1997; de Rujula, Gavela, Hernandez, 1998; Cervera et al, 2000)
Signal prop. sin2213
Contamination
Muons decay in straight sections of a storage ring
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IDS-NF baseline setup 1.0 Two decay rings E=25 GeV
5x1020 useful muon decays per baseline(both polarities!)
Two baselines:~4000 + 7500 km
Two MIND, 50kt each
Currently: MECC at shorter baseline (https://www.ids-nf.org/)(https://www.ids-nf.org/)
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NF physics potential Excellent 13, MH,
CPV discovery reaches (IDS-NF, 2007)
Robust optimum for ~ 4000 + 7500 km
Optimization even robust under non-standard physics(dashed curves)
(Kopp, Ota, Winter, arXiv:0804.2261; see also: Gandhi, Winter, 2007)
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Steve Geer‘s vision
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Neutrino factory in stages?
Phase I: Five years low-E NuFact, TASD@900km Phase II: 5 yr, energy upgrade 25 GeV, MIND@4000km Phase III: 5 yr, second baseline MIND@7500 km
(Tang, Winter, arXiv:0911.5052) Example: 13 not found
Near detectors at the Neutrino Factory
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Near detectors for standard oscillation physics
Need two near detectors, because +/- circulate in different directions
For cross section measurements, no CID required, only excellent flavor-ID
Possible locations:
(Tang, Winter, arXiv:0903.3039)
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Requirementsfor standard oscillation physics (summary)
Muon neutrino+antineutrino inclusive CC event rates measured (other flavors not needed in far detectors for IDS-NF baseline)
Charge identification to understand backgrounds (but no intrinsic beam contamination), no e,
At least same characteristics/quality (energy resolution etc.) as far detectors(a silicon vertex detector or ECC or liquid argon may do much better …)
Location and size not really relevant, because extremely large statistics (maybe size relevant for beam monitoring, background extrapolation)
The specifications of the near detectors may actually be driven by new physics searches!
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Beam+straight geometry
Near detectors described in GLoBES by (E)=Aeff/Adet x on-axis flux and
For (E) ~ 1: Far detector limit Example: OPERA-
sized detector at d=1 km:
L > ~1 km: GLoBES std. description valid(with Leff)
(Tang, Winter, arXiv:0903.3039)
New physics searches with near detectors
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Effective operator picture if mediators integrated out:
Describes additions to the SM in a gauge-inv. way! Example: TeV-scale new physics
d=6: ~ (100 GeV/1 TeV)2 ~ 10-2 compared to the SMd=8: ~ (100 GeV/1 TeV)4 ~ 10-4 compared to the SM
Interesting dimension six operatorsFermion-mediated Non-unitarity (NU)Scalar or vector mediated Non-standard int. (NSI)
New physics from heavy mediators
mass d=6, 8, 10, ...: NSI, NU
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Example 1:
Non-standard interactions Typically described by effective four
fermion interactions (here with leptons)
May lead to matter NSI (for ==e)
May also lead to source/detector NSI(e.g. NuFact:
s for ==e, =)These source/det.NSI are process-dep.!
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Lepton flavor violation… and the story of SU(2) gauge invariance
Strongbounds
e e
e
NSI(FCNC)
e e
e CLFV e
4-NSI(FCNC)
Ex.:
e e
Affects neutrino oscillations in matter (or neutrino production)
Affects environments with high densities (supernovae)
BUT: These phenomena are connected by SU(2) gauge invariance
Difficult to construct large leptonic matter NSI with d=6 operators (Bergmann, Grossman, Pierce, hep-ph/9909390; Antusch, Baumann, Fernandez-Martinez, arXiv:0807.1003; Gavela, Hernandez, Ota, Winter,arXiv:0809.3451)
Need d=8 effective operators, …! Finding a model with large NSI is not trivial!
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Systematic analysis for d=8
Decompose all d=8 leptonic operators systematically (tree level)The bounds on individual
operators from non-unitarity, EWPD, lepton universality are very strong!
(Antusch, Baumann, Fernandez-Martinez, arXiv:0807.1003)
Need at least two mediator fields plus a number of cancellation conditions(Gavela, Hernandez, Ota, Winter, arXiv:0809.3451)
Basis (Berezhiani, Rossi, 2001)
Combinedifferent
basis elements
C1LEH, C3
LEH
Canceld=8
CLFV
But these mediators cause d=6 effects Additional cancellation condition
(Buchmüller/Wyler – basis)
Avoid CLFVat d=8:
C1LEH=C3
LEH
Feynman diagrams
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On current NSI bounds (Source NSI for NuFact)
The bounds for the d=6 (e.g.scalar-mediated) operators are strong (CLFV, Lept. univ., etc.)(Antusch, Baumann, Fernandez-Martinez, arXiv:0807.1003)
The model-independent bounds are much weaker(Biggio, Blennow, Fernandez-Martinez, arXiv:0907.0097)
However: note that here the NSI have to come from d=8 (or loop d=6?) operators ~ (v/)4 ~ 10-4 natural?
„NSI hierarchy problem“?
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Source NSI with at a NuFact
Probably most interesting for near detectors: e
s, s (no intrinsic beam BG)
Near detectors measure zero-distance effect ~ |s|2
Helps to resolve correlations
(Tang, Winter, arXiv:0903.3039)
ND5: OPERA-like ND at d=1 km, 90% CL
This correlation is always present if:- NSI from d=6 operators- No CLFV (Gavela et al,arXiv:0809.3451;see also Schwetz, Ohlsson, Zhang, arXiv:0909.0455 for a particular model)
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Other types of source NSI
In particular models, also other source NSI (without detection) are interesting
Example: (incoh.)
es from addl.
Higgs triplet asseesaw (II) mediator
1 kt, 90% CL, perfect CID
(Malinsky, Ohlsson, Zhang, arXiv:0811.3346)
Requires CID!
Geometric effects? Effects of std.
oscillations
Systematics(CID) limitation?CID important!
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Example 2:
Non-unitarity of mixing matrix Integrating out heavy fermion fields, one obtains neutrino
mass and the d=6 operator (here: fermion singlets)
Re-diagonalizing and re-normalizing the kinetic terms of the neutrinos, one has
This can be described by an effective (non-unitary) mixing matrix with N=(1+) U
Similar effect to NSI, but source, detector, and matter NSI are correlated in a particular, fundamental way (i.e., process-independent)
also: „MUV“
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Impact of near detector
Example: (Antusch, Blennow, Fernandez-Martinez, Lopez-Pavon, arXiv:0903.3986)
near detector important to detect zero-distance effect
Magnetization not mandatory, size matters
Curves: 10kt, 1 kt, 100 t, no ND
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NSI versus NU For a neutrino factory, leptonic NSI and NU may
have very similar correlations between source and matter effects, e.g.
NU (generic, any exp.)NSI (d=6, no CLFV,
NF) Difficult to disentangle with NuFact alone SB?
(Meloni, Ohlsson, Winter, Zhang, to appear)
NU NSI
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Example 3:
Search for sterile neutrinos
3+n schemes of neutrinos include (light) sterile states The mixing with the active states must be small The effects on different oscillation channels depend on
the model test all possible two-flavor short baseline (SBL) cases, which are standard oscillation-free
Example: e disappearanceSome fits indicate an inconsistency between the neutrino and antineutrino data (see e.g. Giunti, Laveder, arXiv:0902.1992)
NB: Averaging over decay straight not possible! The decays from different sections contribute differently!
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SBL e disappearance
Averaging over straight important (dashed versus solid curves)
Location matters: Depends on m31
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Magnetic field if
interesting as well
(Giunti, Laveder, Winter, arXiv:0907.5487)
90% CL, 2 d.o.f.,No systematics,
m=200 kg
Two baseline setup?
d=50 m
d~2 km(as long as possible)
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SBL systematics
Systematics similar to reactor experiments:Use two detectors to cancel X-Sec errors
(Giunti, Laveder, Winter, arXiv:0907.5487)
10% shape
error
arXiv:0907.3145
Also possible with onlytwo ND (if CPT-inv. assumed)
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CPTV discovery reaches (3)
(Giunti, Laveder, Winter, arXiv:0907.5487)
Dashed curves: without averaging over straight Requires four NDs!
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Summary of (new) physics requirementsfor near detectors
Number of sitesAt least two (neutrinos and antineutrinos), for some applications four (systematics cancellation)
Exact baselinesNot relevant for source NSI, NU, important for oscillatory effects (sterile neutrinos etc.)
FlavorsAll flavors should be measured
Charge identificationIs needed for some applications (such as particular source NSI); the sensitivity is limited by the CID capabilities
Energy resolutionProbably of secondary importance (as long as as good as FD); one reason: extension of straight leads already to averaging
Detector sizeIn principle, as large as possible. In practice, limitations by beam geometry or systematics.
Detector geometryAs long (and cylindrical) as possible (active volume)
Aeff < Adet Aeff ~ Adet
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What we need to understand
How long can the baseline be for geometric reasons (maybe: use „alternative locations“)?
What is the impact of systematics (such as X-Sec errors) on new physics parameters
What other kind of potentially interesting physics with oscillatory SBL behavior is there?
How complementary or competitive is a near detector to a superbeam version, see e.g.http://www-off-axis.fnal.gov/MINSIS/Workshop next week in Madrid!
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Summary
The Dirac phase CP is probably the only realistically observable CP phase in the lepton sectorMaybe the only observable CPV evidence for leptogenesisThis and 1, 2: the only completely model-inpendent
parameterization of CPV A neutrino factory could measure that even for
extremely small 13 with „Cabbibo-angle precision“ Near detectors at a neutrino factory are very
important for new physics searches, such as Non-unitarity (heavy neutral fermions) Non-standard interactions (related to CLFV) (Light) sterile neutrinosRequirements most likely driven by new physics searches
BACKUP
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~ current bound
CPV from non-standard interactions
Example: non-standard interactions (NSI) in matter from effective four-fermion interactions:
Discovery potential for NSI-CPV in neutrino propagation at the NF
Even if there is no CPV instandard oscillations, we mayfind CPV!
But what are the requirements for a model to predict such large NSI?
(arXiv:0808.3583)3
IDS-NF baseline 1.0
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CPV discovery for large NSI
If both 13 and |em|
large, the change to discover any CPV will be even larger: For > 95% of arbitrary choices of the phases
NB: NSI-CPV can also affect the production/detection of neutrinos, e.g. in MUV(Gonzalez-Garcia et al, hep-ph/0105159; Fernandez-Martinez et al, hep-ph/0703098; Altarelli, Meloni, 0809.1041; Antusch et al, 0903.3986)
(arXiv:0808.3583)
IDS-NF baseline 1.0
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