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

2

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