CP violation searches with Neutrino Factories and Beta Beams

Neutrinos in Particle, in Nuclear and in AstrophysicsTrento, ItalyNovember 20, 2008

Walter WinterUniversität Würzburg

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Contents

Motivation from theory CPV Phenomenology CP precision measurement CPV from non-standard physics Summary

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)

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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 ofCPV for leptogensis!

(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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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 for CP

~ 85%!Fraction 80% (3)

corresponds to Cabibbo-angleprecision at 2 BENCHMARK!

Best performanceclose to max.

CPV (CP = /2 or 3/2)

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CPV as a fct. of 13

General structure: Signal

Even without systematics (NC, mis-ID, …):

For sin2213 << 2 ~ 10-3

Lose sensitivity with sin 213

For sin2213 >~ 2 ~ 10-3

Sensitivity almost constant over wide range of 13

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Small 13:Optimize discovery reach in 13 direction

Large 13:Optimize discovery reach in (true) CP direction

What defines “small” vs “large 13”? A Double Chooz, Day Bay, T2K, … discovery?

Optimization for CPV

Optimization for small 13

Optimization for large 13

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Large 13 strategy

Assume e.g. that Double Chooz discovers 13

Minimum wish listeasy to define: 5 independent confirmation of 13 > 0 3 mass hierarchy determination for any (true) CP

3 CP violation determination for 80% (true) CP

(~ 2 sensitvity to a Cabibbo angle-size CP violation)

For any (true) 13 in 90% CL D-Chooz allowed range! What is the minimal effort (minimal cost) for that?

NB: Such a minimum wish list is non-trivial for small 13

(arXiv:0804.4000(arXiv:0804.4000; Sim. from hep-ph/0601266; Sim. from hep-ph/0601266; 1.5 yr far det. + 1.5 yr both det.)1.5 yr far det. + 1.5 yr both det.)

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More recent modifications: Higher (Burguet-Castell et al, hep-ph/0312068)

Different isotope pairs leading to higher neutrino energies (same )

Beta beam concept… originally proposed for CERN

(http://ie.lbl.gov/toi)

Key figure (any beta beam):Useful ion decays/year?

Often used “standard values”:3 1018 6He decays/year1 1018 18Ne decays/year

Typical ~ 100 – 150 (for

CERN SPS) eFeNe 189

1810

eLiHe 63

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(CERN layout; Bouchez, Lindroos, Mezzetto, 2003; Lindroos, 2003; Mezzetto, 2003; Autin et al, 2003)

(Zucchelli, 2002)

(C. Rubbia, et al, 2006)

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Example: Minimal beta beam

Minimal effort = One baseline only Minimal Minimal luminosity Any L (green-field!)

Example: Optimize L-for fixed Lumi:CPV constrains

minimal as large as 350

may not even be necessary!(see hep-ph/0503021)

CERN-SPS good enough?

(arXiv:0804.4000)(arXiv:0804.4000)

Sensitivity for entire Double Chooz allowed range!

5yr x 1.1 1018 Ne and 5yr x 2.9 1018 He useful decays

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Example: low-E NuFact A low-E NuFact

performs similarly Combination with

platinumchannel or superbeam may help

(from: Huber, Winter, arXiv:0706.2862; also: Geer, Mena, Pascoli, hep-ph/0701258; Bross et al, arXiv:0708.3889)

Benchmark: 80% 3

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Assume that Double Chooz … do not find 13 Example: Beta beam in 13-direction (for max. CPV)

„Minimal effort“ is a matter of cost!

Small 13 strategyExample: Beta beams

(Huber et al, hep-ph/0506237) (Agarwalla et al, arXiv:0802.3621)

50 kt MIDL=400 km

LSF ~ 2

(LSF)

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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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CPV physics potential

3 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)

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Experiment comparison

The sensitivities are expected to lie somewhere between the limiting curves

Example: IDS-NF baseline(~ dashed curve)

(ISS physics WG report, arXiv:0810.4947, Fig. 105)

CP precision measurement

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Theoretical exampleLarge mixingsfrom CL and sectors?

Example: 23l = 12

= /4, perturbations from CL sector

(can be connected with textures) (Niehage, Winter, arXiv:0804.1546) The value of CP is interesting (even if there is no CPV)

Phenomenological exampleStaging scenarios: Build one baseline first, and then decide depending on the outcome Is CP in the „good“ (0 < CP < ) or „evil“ ( < CP < 2) range?

(signal for neutrinos ~ +sin CP)

Why is that interesting?

12l dominates 13

l dominates

12 ~ /4 + 13 cos CP 12 ~ /4 – 13 cos CP

13 > 0.1, CP ~ 13 > 0.1, CP ~

23 ~ /4 – (13)2/2 23 ~ /4 + (13)2/2

CP andoctant

discriminatethese

examples!

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Performance indicator: CP coverage

Problem: CP is a phase (cyclic)

Define CP coverage (CPC):Allowed range for CP which fits a chosen true value

Depends on true 13 and true CP

Range: 0 < CPC <= 360

Small CPC limit:Precision of CP

Large CPC limit:360 - CPCis excluded range

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CP pattern

Performance as a function of CP (true)

Example: Staging.If 3000-4000 km baseline operates first, one can use this information to determine if a second baseline is needed

(Huber, Lindner, Winter, hep-ph/0412199)

Exclusion limitPrecision limit

CPV from non-standard physics?

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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(Gonzalez-Garcia et al, hep-ph/0105159; Fernandez-Martinez et al, hep-ph/0703098; Altarelli, Meloni, 0809.1041) (arXiv:0808.3583)

IDS-NF baseline 1.0

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Effective operator picture:

Describes additions to the SM in a gauge-inv. way! Example: NSI for 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

Current bounds, such as from CLFV: one cannot construct large (= observable) leptonic matter NSI with d=6 operators (except for

m, maybe)

(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!

Models for large NSI?

mass d=6, 8, 10, ...: NSI

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Systematic analysis for d=8

Decompose all d=8 leptonic operators systematicallyThe bounds on individual

operators from non-unitarity, EWPD, etc 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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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 What precision do we want for it? Cabibbo-angle

precision? Relates to fraction of „CP“ ~ 80-85% The perspectives for a measurement are best if 13 is

not too small and not too large For a BB or NF, the experiment optimization/choice

depends on 13 large or small Other interesting aspects in connection with CPV:

CP precision measurement, NSI-CPV

Backup

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Minimal beta beam at the CERN-SPS?( fixed to maximum at SPS)

(arXiv:0809.3890)(arXiv:0809.3890)

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Appearance ratesNF Golden-SB appearance-NF Platinum

Ep chosen such that SB peaks at lower E Platinum peaks at higher E (spectrum!)

(Huber, Winter, 2007)

2.5 102.5 10

2121 useful muon decays

useful muon decays

Golden

E=5 GeVL=1250 km

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Low-E Nufact optimization

Geer et al. choices are sufficiently close to optimum NF-SB synergistic, better performance than NF alone Our choices : L = 900 km, E = 5 GeV and L=1250 km, E=5 GeV

(given the low energy ~ minimum effort constraint)

CP

fraction for discovery (3) , sin

2213 =

0.1

(Huber, Winter, 2007)

Doubleluminosity!

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(Mats Lindroos)

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(Mats Lindroos)