Long baseline neutrino oscillations:Theoretical aspects

NOW 2008 Conca Specchiulla, ItalySeptember 9, 2008

Walter WinterUniversität Würzburg

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Contents

Theoretical motivation:Quantities of interest

How to measure these? - Phenomenology Experiment choice and optimization Neutrino factory: what can we expect? The potentially unexpected Summary

Quantities of interest

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Theoretical motivation Mass models describe masses and mixings (mass

matrices) by symmetries, GUTs, anarchy arguments, etc.

From that: predictions for observables

Example: Literature research for 13

13 as performance indicator for models (Albright, Chen, 2006)

Talk: Mu-Chun Chen, Friday

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Large mixingsfrom CL and sectors?

Example: 23l = 12

= /4, perturbations from CL sector

(can be connected with textures) (Niehage, Winter, 2008)

Another example: QLC+Flavor symmetrieslead e.g. to

Modern QLC scenarios do not have an exact factor k=1 there (depends on model) (e.g. Plentinger, Seidl, Winter, 2008; see also: Frampton, Matsuzaki, 2008)

Some other examples

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!

k as performance indicator for QLC modelsk

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Perform. indicators for theoryWhat observables test the theory space most efficiently?

Magnitude of 13 (see before!) Mass hierarchy

(strongly affects textures) Deviations from max. mixing

(- symmetry?) 23 octant |sin212-1/3|

(tribimaximal mixings?) |sinCP-1| (CP violation)

(leptogenesis?) Value of CP

k C+ 12 ~ /4 ~ 23 (k as indicator for quark-lepton unification models?)

Dev. from std. osc. framework

(Antusch et al, hep-ph/0404268)

Most important for LBL experiments

Long baseline phenomenology

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Why GeV energies?

Unoscillated flux Cross sections ~ E (DIS regime) Flux ~ E2 (beam collimation)

For fixed L: unoscillated event rate ~ E3

Oscillated flux Adjust baseline to stay on osc. maximum

Flux ~ 1/L2, L ~ E on oscillation maximumEvent rate ~ E on oscillation maximum

In addition:Matter effects (resonance energy ~ 10 GeV in Earth‘s mantle)Measure mass hierarchy, Flux(L) ~ const. at resonance

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GeV Long baseline experiments

Contamination

Source Production … and Detection Limitations L <E>

Beam,Super-beam

Intrinsic beam BGs,systematics

100-2,500 km

~ 0.5 – 5 GeV

Neutrino factory

Charge identification,NC BG

700-7,500 km

2-25 GeV

-beam Sourceluminosity

100-7,500 km

0.3 – 10 GeV

For leading atm. params Signal prop. sin2213

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Channels of interest

Disappearance for m312, 23:

NB: We expand in

Appearance for 13, CPV, MH: Golden: e (NF/BB) or e(SB)

(e.g., De Rujula, Gavela, Hernandez, 1999; Cervera et al, 2000)

Silver: e (NF – low statistics!?)(Donini, Meloni, Migliozzi, 2002; Autiero et al, 2004)

Platinum: e (NF: difficult!)(see e.g. ISS physics working group report)

Other appearance: (OPERA, NF?) Neutral currents for new physics

(e.g., Barger, Geer, Whisnant, 2004; MINOS, 2008)

31 = m312 L/(4E)

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Appearance channels

(Cervera et al. 2000; Freund, Huber, Lindner, 2000; Huber, Winter, 2003; Akhmedov et al, 2004)

Antineutrinos: Magic baseline: Silver: Superbeams, Plat.:

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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

-beam,

-beam, anti-

Iso-probability curves

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Degeneracy resolution Matter effects (sign-

degeneracy) – long baseline, high E

Different beam energies or better energy resolution in detector

Second baseline

Good enough statistics

Other channels

Other experimentclasses

Talk: Thomas Schwetz

WBB FNAL-DUSEL, T2KK, NF@long L, …

Monochromatic beam, Beta beam with different isotopes, WBB, …

T2KK, magic baseline ~ 7500 km, SuperNOvA

Neutrino factory, beta beam, Mton WC

SB+BB CERN-Frejus, silver/platinum @ NF

Atmospheric, …

(many many authors, see e.g. ISS physics WG report)(Minakata, Nunokawa, 2001; Parke)

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On-axis WBB versus off-axis NBBExample: NuMI-like beam 100kt liquid argon

CP=-/2

CP=+/2

sin2213 CP violation Mass hierarchy

(Barger et al, hep-ph/0703029)

Constraintfrom

NuMIbeam

FNAL-DUSELWBB

Ash RiverOA,NOvA*

Off-axis technology may not be necessary if the detector is good enough, i.e., has good BG rejection and good energy resolution! WC good enough???

On axis

C

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Quantification of performance

Commonly used performance indicators:Indicator Description + -

13 sensitivity (limit)

New 13 limit if no signal

Does not depend on (true) CP, MH

Strongly affected by degs (corresponds to worst case discovery reach)

13, CPV, MH discovery reach

Range of (true) 13 and CP for which 13, CPV, or MH can be discovered

Comprehensive picture of parameter space

Difficult to visualize: Depends on two true parameters

Sensitivity to octant

Range of (true) 13, 23 (and CP) for which the 23 octant can be established

Comprehensive picture of parameter space

Many true parameter dependencies

…

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Example: Discovery reaches… and the “Fraction of CP”

Sensitive region as function of true 13 and

CP

CP values now stacked for each 13

Read: If sin2213=0.04, we expect a discovery for

20% of all values of CP

Worst case 13 reach

Best case 13 reach

“Typical” CP:CP fraction 50%

Sometimes: Band for risk wrt CP

Simplifications:

Sometimes:choose specifc CP,

e.g. 3/2(worst/best case)

A

B

C

D E

F

G

Experiment choice and optimization (some thoughts)

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Small 13:Optimize 13, MH, and CPV discovery reaches in 13 direction

Large 13:Optimize 13, MH, and CPV discovery reaches in (true) CP direction

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

Optimization of exps

(3m312=0.0022 eV2

Optimization for small 13

Optimization for large 13

T2KK

Beta beam

NuF

act

B

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Timescale for 13 discovery?

(Huber, Kopp, Lindner, Rolinec, Winter, 2006)

Assume:Decision on future experiments made after some LHC running and next-generation experiments

Two examples: ~ 2011: sin2213 > 0.04?

~ 2015: sin2213 > 0.01?

D

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Large 13 strategy

Assume that Double Chooz finds 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

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

NB: CP fraction 80% comes from comparison with IDS-NF baseline etc.

(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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Example: Minimal beta beam

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

Example: Optimize L-for fixed Lumi: as large as 350

may not even be necessary!

(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 decaysMore on beta beams: Mezzetto‘s talk!

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Small 13 strategy Assume that Double Chooz … do not find 13 Minimum wish list:

discovery of 13 > 0 3 mass hierarchy determination 3 CP violation determination

For as small as possible (true) 13 Two unknowns here:

For what fraction of (true) CP? One has to make a choice (e.g. max. CP violation, for 80% of all CP, for 50%, …)

How small 13 is actually good enough? Minimal effort is a matter of cost! Maybe the physics case will be defined

otherwise?

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Connection to high-E frontier?

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Optimal strategy vs. regional interests?

So far: purely conceptual …

… however, the optimal strategy depends on regional boundary conditions!

CERN-INO?JHF-INO?

Talk: Goswami

Talks:Goodman (US)Evans (MINOS)

Kurimoto (SciBooNE)

Talks:Ronga (Gran Sasso)

Scott-Lavina (OPERA)Sala (CNGS)

Talks:Kakuno (T2K)Dufour (T2KK)

Physics potential of the neutrino factory: what can we expect?

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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

Talks:Long (IDS-NF)Bonesini (R&D)

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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/)

More by Ken Long

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Physics potential

3

BB B

Excellent 13, MH, CPV discovery reaches

About 10% full width error (3) on log10 (sin2213) for sin2213 = 0.001(Gandhi, Winter, hep-ph/0612158, Fig. 6)

About 20-60 degree full width error (3) on CP for sin2213 = 0.001 (Huber, Lindner, Winter, hep-ph/0412199, Fig. 7)

But what does that mean? Cabibbo angle-precision (C ~ 13 deg.)!

Why is that relevant? Can be another feature of nontrivial QLC models:E.g. from specific texture+QLC-type assumptions:

(: model parameter)

(Niehage, Winter, 2008)

(IDS-NF, 2007)

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Two-baseline optim. revisited

Robust optimum for ~ 4000 + 7500 km

Optimization even robust under non-standard physics(dashed curves)

(Kopp, Ota, Winter, 2008)

C

C

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Matter density measurement

Assume that only one parameter measured:Constant referencedensity Ref

or lower mantle density LM

(Minakata, Uchinami, 2007; Gandhi, Winter, 2007)

True =0

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Solar term:

Note that

i.e., effect (initially) increases with baseline ( ~ L)!

MSW effect sensitivity evenfor 13=0!

MSW effect in Earth matter

(hep-ph/0411309)

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C

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Octant degeneracy

4000 km alone: Problems with degs for intermediate 13

7200 km alone: No sensitivity for small 13

4000 km + 7200 km: Good for all 13

(Gandhi, Winter, 2007)

Similar performanceto Gold+Silver* @ 4000km

Meloni, arXiv:0802.0086

The unexpected!?

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~ current bound

Neutrino osc. framework incomplete?

Example: non-standard interactions (NSI) from effective four-fermion interactions:

Discovery potential for NSI-CP violation 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

Talk by T. Ota

See also talk by D. Meloni

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Help from other experiments?

Physics scenario:Double Chooz finds 13and ~ a total of 100 muon tracks from astrophysical sources observed (ratio of muon tracks to showers), only m1 stableon extragalatic distances

Double Choozalone and this informationcould establish CPV

Other sources of information: Supernovae, atmospheric, LHC, 0

Talks: Petcov, Schwetz, Sigl, … (Maltoni, Winter, 2008)

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Outlook: How to design the optimal experiment

Future LBL experiment

Physics

Politics

Theory Performance indicators: 13, CP violation, MH, …Correlations+

Degeneracies Resolution strategies

New physics? Inclusive strategies(more channels, etc.)

Potitical boundary conditions

(e.g., Obama vs. McCain)

Same measurement

by other experiment

(e.g., MH from supernova)

Regionalinterests

(e.g., DUSEL, T2KK, …)

LHC(e.g.,connection to high-E frontier)