CP violation and mass hierarchy searches
with Neutrino Factories and Beta Beams
NuGoa – Aspects of NeutrinosGoa, IndiaApril 10, 2009
Walter WinterUniversität Würzburg
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Contents
Motivation from theory: CPV CPV Phenomenology The experiments Optimization for CPV CP precision measurement CPV from non-standard physics Mass hierarchy measurement 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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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)
The experiments
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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 figures (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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Current status: A variety of ideas
“Classical” beta beams: “Medium” gamma options (150 < < ~350)
- Alternative to superbeam! Possible at SPS (+ upgrades)- Usually: Water Cherenkov detector (for Ne/He)(Burguet-Castell et al, 2003+2005; Huber et al, 2005; Donini, Fernandez-Martinez, 2006;
Coloma et al, 2007; Winter, 2008)
“High” gamma options (>> 350)- Require large accelerator (Tevatron or LHC-size)- Water Cherenkov detector or TASD or MID? (dep. on , isotopes(Burguet-Castell et al, 2003; Huber et al, 2005; Agarwalla et al, 2005, 2006, 2007, 2008, 2008;
Donini et al, 2006; Meloni et al, 2008)
Hybrids: Beta beam + superbeam
(CERN-Frejus; Fermilab: see Jansson et al, 2007) “Isotope cocktail” beta beams (alternating ions)
(Donini, Fernandez-Martinez, 2006) Classical beta beam + Electron capture beam
(Bernabeu et al, 2009)
… The CPV performance depends very much on the choice
from this list!
Often: baseline Europe-India
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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)
Optimization for CPV
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Small 13:Optimize discovery reach in 13 direction
Large 13:Optimize discovery reach in (true) CP direction~ Precision!
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 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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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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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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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; see also Masina, 2005; Antusch, King 2005 for similar sum
rules) 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, 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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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: difficult to 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, 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
Mass hierarchy (MH)
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Motivation
Specific models typically come together with specific MH prediction (e.g. textures are very different)
Good model discriminator(Albright, Chen, hep-h/0608137)
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8
Normal Inverted
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Magic baseline:Removes all degeneracy issues (and is long!)
Resonance: 1-A 0 (NH: , IH: anti-)Damping: sign(A)=-1 (NH: anti-, IH: )Energy close to resonance energy helps (~ 8 GeV)
To first approximation: Pe ~ L2 (e.g. at resonance)Baseline length helps (compensates 1/L2 flux drop)
Matter effects
(Cervera et al. 2000; Freund, Huber, Lindner, 2000; Huber, Winter, 2003; Akhmedov et al, 2004)
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Baseline dependence
Comparison matter (solid) and vacuum (dashed)
Matter effects (hierarchy dependent) increasewith L
Event rate (, NH) hardly drops with LGo to long L!
(Freund, Lindner, Petcov, Romanino, 1999)
(m212 0)
Eve
nt
rate
s (A
.U.)
Vacuum, NH or IH
NH matter effect
NH matter effect
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Mass hierarchy sensitivity
For a given set of true 13 and CP: Find the sgn-deg.solution
Repeat that for all true true 13 and CP (for this plot)
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Small 13 optimization: NF
Magic baseline good choice for MH E ~ 15 GeV sufficient (peaks at 8 GeV)
(Huber, Lindner, Rolinec, Winter, 2006) (Kopp, Ota, Winter, 2008)
E-L (single baseline) L1-L2 (two baselines)
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Small 13 optimization: BB
Only B-Li offers high enough energies for „moderately high“ Magic baseline global optimum if >=350 (B-Li) Recently two-baseline setups discussed
(Coloma, Donini, Fernandez-Martinez, Lopez-Pavon, 2007; Agarwalla, Choubey, Raychaudhuri, 2008)
(Agarwalla, Choubey, Raychaudhuri, Winter, 2008)
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Optimization for large 13
Performance as defined before (incl. 3 MH)
L > 500 km necessary Large enough luminosity
needed High enough necessary
Ne-He: limited to > 120
B-Li: in principle, smaller possible
High = high E = stronger matter effects!
(arXiv:0804.4000)(arXiv:0804.4000)
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Physics case for CERN-India?(neutrino factory)
MH measurement if 13 small (see before; also de Gouvea, Winter, 2006)
Degeneracy resolution for 10-4 ≤ sin2213 ≤ 10-2 (Huber, Winter, 2003)
Risk minimization (e.g., 13 precision measurement) (Gandhi, Winter, 2007)
Compementary measurement(e.g. in presence of NSI)(Ribeiro et al, 2007)
MSW effect verification (even for 13=0) (Winter, 2005)
Fancy stuff (e.g. matter density measurement) (Gandhi, Winter, 2007)
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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% 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 MH for small 13 requires magic baseline