CP violation and mass hierarchy searches with Neutrino Factories and Beta Beams

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CP violation and mass hierarchy searches with
Neutrino Factories and Beta Beams

• NuGoa Aspects of Neutrinos
• Goa, India
• April 10, 2009Walter Winter
• Universität Würzburg

TexPoint fonts used in EMF AAAAAAAA
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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

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Motivation from theory
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Where does CPV enter?

• Example Type I seesaw (heavy SM singlets Nc)

Could also be type-II, III seesaw,radiative
generation of neutrino mass, etc.
Block-diag.
Primary source of CPV(depends BSM theory)
Charged leptonmass terms
Eff. neutrinomass terms
Effective source of CPV(only sectorial origin
relevant)
Observable CPV(completely model-indep.)
CC
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Connection to measurement

• From the measurement point of viewIt 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

CPV in 0nbb decay
LBL accessible CPV dIf ? UPMNS
real ? CP conserved
Extremely difficult! (Pascoli, Petcov,
Rodejohann, hep-ph/0209059)
There is no specific connectionbetween low- and
high-E CPV!
But thats not true for special (restrictive)
assumptions!
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Why is CPV interesting?

• LeptogenesisCPV from Nc decays
• If special assumptions(such as hier. MR,NH
  light neutrinos, )it is possible that dCPis
  the only source ofCPV for leptogensis!

(Nc)i
(Nc)i
MD (in basis where Ml and MR diagonal)
Different curvesdifferent assumptions for q13,
(Pascoli, Petcov, Riotto, hep-ph/0611338 )
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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(qC) 13?
• Can also be seen in sum rules for certain
  assumptions, such as(F model parameter)
• This talk Want Cabibbo-angle order precision for
  dCP!

(arXiv0709.2163)
(Niehage, Winter, arXiv0804.1546)
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CPV phenomenology
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Terminology

• Any value of dCP(except for 0 and p)violates CP
• Sensitivity to CPVExclude CP-conservingsoluti
  ons 0 and pfor any choiceof the other
  oscillationparameters in their allowed ranges

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Measurement of CPV

• Antineutrinos
• Magic baseline
• Silver
• Platinum, Superb.

(Cervera et al. 2000 Freund, Huber, Lindner,
2000 Huber, Winter, 2003 Akhmedov et al, 2004)
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Degeneracies
Iso-probability curves

• CP asymmetry(vacuum) suggests the use of
  neutrinos and antineutrinos
• One discrete deg.remains in (q13,d)-plane
  (Burguet-Castell et al, 2001)
• Additional degeneracies (Barger, Marfatia,
  Whisnant, 2001)
• Sign-degeneracy (Minakata, Nunokawa, 2001)
• Octant degeneracy (Fogli, Lisi, 1996)

Neutrinos
Antineutrinos
Best-fit
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Intrinsic vs. extrinsic CPV

• The dilemma Strong matter effects (high E, long
  L), but Earth matter violates CP
• Intrinsic CPV (dCP) has to be disentangled from
  extrinsic CPV (from matter effects)
• Example p-transitFake sign-solutioncrosses CP
  conservingsolution
• Typical ways out
• T-inverted channel?(e.g. beta beamsuperbeam,pla
  tinum channel at NF, NFSB)
• Second (magic) baseline

Critical range
NuFact, L3000 km
True dCP (violates CP maximally)
Degeneracy above 2s (excluded)
Fit
True
(Huber, Lindner, Winter, hep-ph/0204352)
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The magic baseline
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CPV discovery reach
in (true) sin22q13 and dCP
Best performanceclose to max. CPV (dCP p/2 or
3p/2)
Sensitive region as a function of true q13 and dCP
dCP values now stacked for each q13
No CPV discovery ifdCP too close to 0 or p
No CPV discovery forall values of dCP
3s
Cabibbo-angleprecision at 2s BENCHMARK!
Read If sin22q1310-3, we expect a discovery for
80 of all values of dCP
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The experiments
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Beta beam concept originally proposed for CERN
(CERN layout Bouchez, Lindroos, Mezzetto, 2003
Lindroos, 2003 Mezzetto, 2003 Autin et al, 2003)
(Zucchelli, 2002)

• Key figures (any beta beam) g, useful ion
  decays/year?
• Often used standard values3 1018 6He
  decays/year1 1018 18Ne decays/year
• Typical g 100 150 (for CERN SPS)

g

• More recent modifications
• Higher g (Burguet-Castell et al, hep-ph/0312068)
• Different isotope pairs leading to higher
  neutrino energies (same g)

(http//ie.lbl.gov/toi)
(C. Rubbia, et al, 2006)
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Current status A variety of ideas

• Classical beta beams
• Medium gamma options (150 lt g lt 350)
• Alternative to superbeam! Possible at SPS (
  upgrades)
• Usually Water Cherenkov detector (for Ne/He)
• (Burguet-Castell et al, 20032005 Huber et al,
  2005 Donini, Fernandez-Martinez, 2006 Coloma
  et al, 2007 Winter, 2008)
• High gamma options (g gtgt 350)
• Require large accelerator (Tevatron or LHC-size)
• Water Cherenkov detector or TASD or MID? (dep. on
  g, 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 factoryInternational design study
(Geer, 1997 de Rujula, Gavela, Hernandez, 1998
Cervera et al, 2000)
Signal prop. sin22q13
Contamination
Muons decay in straight sections of a storage ring

• 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 Euronus proposal
  within the FP 07
• In the US Muon collider task force

ISS
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IDS-NF baseline setup 1.0

• Two decay rings
• Em25 GeV
• 5x1020 useful muon decays per baseline(both
  polarities!)
• Two baselines4000 7500 km
• Two MIND, 50kt each
• Currently MECC at shorter baseline

• (https//www.ids-nf.org/)

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NF physics potential

• Excellent q13, 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, arXiv0804.2261 see also
Gandhi, Winter, 2007)
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Optimization for CPV
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Optimization for CPV

• Small q13Optimize discovery reach in q13
  direction
• Large q13Optimize discovery reach in (true)
  dCP direction Precision!
• What defines small vs large q13? A Double
  Chooz, Day Bay, T2K, discovery?

Optimization for large q13
Optimization for small q13
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Large q13 strategy

• Assume e.g. that Double Chooz discovers q13
• Minimum wish listeasy to define
• 5s independent confirmation of q13 gt 0
• 3s mass hierarchy determination for any (true)
  dCP
• 3s CP violation determination for 80 (true)
  dCP( 2s sensitvity to a Cabibbo angle-size CP
  violation)
• For any (true) q13 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 q13

(arXiv0804.4000 Sim. from hep-ph/0601266 1.5
yr far det. 1.5 yr both det.)
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Example Minimal beta beam
(arXiv0804.4000)

• Minimal effort
• One baseline only
• Minimal g
• Minimal luminosity
• Any L (green-field!)
• Example Optimize L-g for fixed Lumi
• CPV constrains minimal g
• g as large as 350 may not even be necessary!(see
  hep-ph/0503021)
• CERN-SPS good enough?

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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Small q13 strategyExample Beta beams

• Assume that Double Chooz do not find q13
• Example Beta beam in q13-direction (for max.
  CPV)
• Minimal effort is a matter of cost!

LSF 2
50 kt MIDL400 km
(LSF)
(Huber et al, hep-ph/0506237)
(Agarwalla et al, arXiv0802.3621)
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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, arXiv0810.4947, Fig. 105)
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CP precision measurement
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Why is that interesting?

• Theoretical exampleLarge mixingsfrom CL and n
  sectors?Example q23l q12n p/4,
  perturbations from CL sector(can be
  connected with textures) (Niehage,
  Winter, arXiv0804.1546 see
  also Masina, 2005 Antusch, King 2005 for similar
  sum rules)
• The value of dCP is interesting (even if there is
  no CPV)
• Phenomenological exampleStaging scenarios Build
  one baseline first, and then decide depending on
  the outcome
• Is dCP in the good (0 lt dCP lt p) or evil (p lt
  dCP lt 2p) range? (signal for neutrinos sin
  dCP)

dCP andoctantdiscriminatethese examples!
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Performance indicator CP coverage

• Problem dCP is a phase (cyclic)
• Define CP coverage (CPC)Allowed range for dCP
  which fits a chosen true value
• Depends on true q13 and true dCP
• Range 0 lt CPC lt 360?
• Small CPC limitPrecision of dCP
• Large CPC limit360? - CPCis excluded range

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CP pattern

• Performance as a function of dCP (true)
• Example Staging.If 3000-4000 km baseline
  operates first, one can use this information to
  determine if a second baseline is needed

Exclusion limit
Precision limit
(Huber, Lindner, Winter, hep-ph/0412199)
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CPV from non-standard physics?
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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 NFEven if there is no CPV
  instandard oscillations, we mayfind CPV!But
  what are the requirements for a model to predict
  such large NSI?

current bound
IDS-NF baseline 1.0
(arXiv0808.3583)
3s
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CPV discovery for large NSI

• If both q13 and eetm large, the change to
  discover any CPV will be even larger For gt
  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)

IDS-NF baseline 1.0
(arXiv0808.3583)
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Models for large NSI?

• Effective operator pictureDescribes
  additions to the SM in a gauge-inv. way!
• Example NSI for TeV-scale new physicsd6
  (100 GeV/1 TeV)2 10-2 compared to the SMd8
  (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 d6 operators (except for ettm, maybe)
  (Bergmann, Grossman, Pierce, hep-ph/9909390
  Antusch, Baumann, Fernandez-Martinez,
  arXiv0807.1003 Gavela, Hernandez, Ota,
  Winter,arXiv0809.3451)
• Need d8 effective operators!
• Finding a model with large NSI is not trivial!

n mass
d6, 8, 10, ... NSI
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Systematic analysis for d8
Basis (Berezhiani, Rossi, 2001)
Feynman diagrams

• Decompose all d8 leptonic operators
  systematically
• The bounds on individual operators from
  non-unitarity, EWPD, lepton universality are very
  strong! (Antusch, Baumann, Fernandez-Martinez,
  arXiv0807.1003)
• Need at least two mediator fields plus a number
  of cancellation conditions(Gavela, Hernandez,
  Ota, Winter, arXiv0809.3451)

Avoid CLFVat d8C1LEHC3LEH
Combinedifferentbasis elements C1LEH, C3LEH
Canceld8CLFV
But these mediators cause d6 effects?
Additional cancellation condition(Buchmüller/Wyle
r basis)
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Mass hierarchy (MH)
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Motivation
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8
Normal
Inverted

• 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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Matter effects
(Cervera et al. 2000 Freund, Huber, Lindner,
2000 Huber, Winter, 2003 Akhmedov et al, 2004)

• Magic baseline
• Removes all degeneracy issues (and is long!)
• Resonance 1-A ? 0 (NH n, IH anti-n)Damping
  sign(A)-1 (NH anti-n, IH n)
• Energy close to resonance energy helps ( 8 GeV)
• To first approximation Pem L2 (e.g. at
  resonance)
• Baseline length helps (compensates 1/L2 flux
  drop)

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Baseline dependence
Event rates (A.U.)

• Comparison matter (solid) and vacuum (dashed)
• Matter effects (hierarchy dependent)
  increasewith L
• Event rate (n, NH) hardly drops with L
• Go to long L!

(Dm212 ? 0)
NH matter effect
Vacuum, NH or IH
NH matter effect
(Freund, Lindner, Petcov, Romanino, 1999)
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Mass hierarchy sensitivity

• For a given set of true q13 and dCP Find the
  sgn-deg.solution
• Repeat that for all true true q13
  and dCP (for this plot)

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Small q13 optimization NF
Em-L (single baseline)
L1-L2 (two baselines)
(Kopp, Ota, Winter, 2008)
(Huber, Lindner, Rolinec, Winter, 2006)

• Magic baseline good choice for MH
• Em 15 GeV sufficient (peaks at 8 GeV)

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Small q13 optimization BB
(Agarwalla, Choubey, Raychaudhuri, Winter, 2008)

• Only B-Li offers high enough energies for
  moderately high g
• Magic baseline global optimum if ggt350 (B-Li)
• Recently two-baseline setups discussed(Coloma,
  Donini, Fernandez-Martinez, Lopez-Pavon, 2007
  Agarwalla, Choubey, Raychaudhuri, 2008)

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Optimization for large q13
(arXiv0804.4000)

• Performance as defined before (incl. 3s MH)
• L gt 500 km necessary
• Large enough luminosity needed
• High enough g necessary
• Ne-He limited to g gt 120
• B-Li in principle, smaller g possible
• High g high E stronger matter effects!

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Physics case for CERN-India?(neutrino factory)

• MH measurement if q13 small (see before also de
  Gouvea, Winter, 2006)
• Degeneracy resolution for 10-4 sin22q13 10-2
  (Huber, Winter, 2003)
• Risk minimization (e.g., q13 precision
  measurement) (Gandhi, Winter, 2007)
• Compementary measurement(e.g. in presence of
  NSI)(Ribeiro et al, 2007)
• MSW effect verification (even for q130)
  (Winter, 2005)
• Fancy stuff (e.g. matter density measurement)
  (Gandhi, Winter, 2007)

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Summary

• The Dirac phase dCP is probably the only
  realistically observable CP phase in the lepton
  sector
• Maybe the only observable CPV evidence for
  leptogenesis
• This and f1, f2 the only completely
  model-inpendent parameterization of CPV
• What precision do we want for it? Cabibbo-angle
  precision? ? Relates to fraction of dCP
  80-85
• For a BB or NF, the experiment optimization/choice
  depends on q13 large or small
• Other interesting aspects in connection with CPV
  CP precision measurement, NSI-CPV
• MH for small q13 requires magic baseline