Jose BernabeuJose BernabeuU. Valencia and U. Valencia and

IFICIFIC

XIII International Workshop on Neutrino Telescopes

March 2009

CP Violation in CP Violation in Neutrino Oscillations Neutrino Oscillations without Antineutrinos: without Antineutrinos:

Energy DependenceEnergy Dependence

ProgrammeProgramme What is known, what is unknown in Neutrino OscillationsWhat is known, what is unknown in Neutrino Oscillations

Third Generation of Neutrino Experiments: CP Violation Third Generation of Neutrino Experiments: CP Violation

The CP phase with neutrinos only: Energy DependenceThe CP phase with neutrinos only: Energy Dependence

A combined BB and EC experiment for the same ion A combined BB and EC experiment for the same ion

YtterbiumYtterbium

Comparison between Comparison between

i) low energy (Ei) low energy (Epp(SPS) ≤ 450 GeV, Frejus and Canfranc) (SPS) ≤ 450 GeV, Frejus and Canfranc)

ii) high energy (Eii) high energy (Epp(SPS) ≤ 1000 GeV, Canfranc and (SPS) ≤ 1000 GeV, Canfranc and

Boulby)Boulby)

CP-Violation Discovery Potential and Mass Hierarchy CP-Violation Discovery Potential and Mass Hierarchy

DeterminationDetermination

ConclusionsConclusions

Neutrino flavour Neutrino flavour oscillationsoscillations

2512

2

2323

2

1065.7

104.2

eVm

eVm

304.0sin

50.0sin

122

232

o1013 ?

Majorana neutrinos? 0: masses and phases

Absolute neutrino masses ? 3 H beta, Cosmology

Form of the mass spectrum Matter effect in neutrino propagation

What is What is known, known, what is what is unknownunknown

, A hint ?

The Pontecorvo MNS The Pontecorvo MNS MatrixMatrix

3

2

1

Ue

100

0

0

0

010

0

0

0

001

1212

1212

1313

1313

2323

2323 cs

sc

ces

esc

cs

scUi

i

For Flavour oscillations U: 3 mixings, 1 phase

Atmospheric KEK, MINOS, OPERA

•Appearance e!•Reactors •Matter effects

SolarKAMLANDBorexino

Even if theyare Majorana

After diagonalization of the neutrino mass matrix,

Three Generations Three Generations of Experiments of Experiments

0. Only three? MiniBoone I. Solar Sector, Atmospheric Sector

II. Connection between both Sectors

III. CP-Violating Interference δ Super-Beams? Beta/ EC Beams? Neutrino Factory?

ΔΔm2

12, θ12│Δm2

23│, θ23

Borexino MINOS, OPERA

θθ13, Sign (Δm2

23)Double CHOOZ, Daya Bay, T2K, NOVA, …

European Strategy Plan demands for ~ 2012 a CDR with the alternatives: SuperBeams, Beta/EC Beams, Neutrino Factory.

SuperBeam: no pure Flavour, uncertain continuous Spectrum.

Beta Beam: pure Flavour, known continuous Spectrum.

EC Beam: pure Flavour, known single Monochromatic Beam.

Neutrino Factory: pure Flavour iff detector with charge discrimination, known continuous Spectrum.

Frejus

• CPV can be observed either by an Asymmetry between Neutrinos and Antineutrinos or by Energy Dependence (CP phase as a phase shift) in the Neutrino channel, or both.

Third Generation Experiments: CP Violation

Why Energy Dependence ?A theorem

CP violation: )()( ee PP

CPT invariance + CP violation = T non-invariance )()( ee PP

No Absorptive part Hermitian Hamiltonian CP odd = T odd =

is an odd function of time = L !

)()( ee PP

In vacuum neutrino oscillationsIn vacuum neutrino oscillations for relativistic neutrinos L/E dependence, so

CP-even (odd) terms in the appearance probability Even (odd) functions of energy. Then ENERGY DEPENDENCE disentangles the CP-even and CP-odd terms

Interest of energy Interest of energy dependence in suppressed dependence in suppressed neutrino oscillationsneutrino oscillations

• Appearance probability:

• |Ue3| gives the strength of P(νe→νμ)

• δ gives the interference pattern: CP odd term is odd CP odd term is odd in E/Lin E/L• δ acts as a phase shift This suggests the idea of either a monochromatic

neutrino beam to separate δ and |Ue3| by energy dependence with different boosts, or a combination of channels with different neutrino energies in the same boost

)4

sin(4

)4

cos(~

)4

(sin2sin

)4

(sin2sin)(

ceInterferen

213

212

213

Solar

2122

1222

23

cAtmospheri

2132

1322

23

E

Lm

E

Lm

E

LmJ

E

Lmc

E

LmsP e

• CP violation accessible in suppressed appearance experiments, in order to have access to the interference between the atmospheric and solar probability amplitudes

Neutrinos from electron Neutrinos from electron capturecapture

Electron capture:

From the From the single energysingle energy e e---capture neutrino spectrum, -capture neutrino spectrum, we can we can get aget a pure and monochromaticpure and monochromatic beambeam by by accelerating ec-accelerating ec-unstable ionsunstable ions and choosing forward and choosing forward νν’s ’s One can One can concentrate all the intensity at the most appropriate concentrate all the intensity at the most appropriate energy for extracting the neutrino parameters energy for extracting the neutrino parameters

● 22 body decay! body decay! In the CMIn the CM , a single discrete single discrete energyenergy if a single final nuclear level is populated

How can we obtain a monochromatic neutrino beam?

Forward directionForward directionZ protonsN neutrons

Z-1 protonsN+1 neutrons

boostboost

J. B., C. E. et al

Eν

A combined beta-beam and A combined beta-beam and EC neutrino experimentEC neutrino experiment (156Yb)

• Suppressed appearance probabilities for the CERN-Frejus (130 Km, red line) and CERN-Canfranc (650 Km, blue line) baselines. The unoscillated neutrino flux is shown for γ=166

• Suppressed appearance probabilities for the CERN-Canfranc (650 Km, blue line) and CERN-Boulby (1050 Km, red line) baselines. The unoscillated neutrino flux is shown for γ=369

Similarities and Differences Similarities and Differences between Beta beam and EC between Beta beam and EC neutrinosneutrinos- In proton rich nuclei (to restore the same orbital angular momentum for protons and neutrons )

Superallowed Gamow-Teller transitionSuperallowed Gamow-Teller transition ● The “breakthrough” came thanks to the recent discovery of isotopes with small half-lives of one minute or less, which decay in neutrino channels near 100% to a SINGLE Gamow-a SINGLE Gamow-Teller resonance.Teller resonance.

Nuclear

• A Facility with an EC channel would require a A Facility with an EC channel would require a different approach different approach to acceleration and storageto acceleration and storage of the ion beam compared to the of the ion beam compared to the standard beta-beam, as the atomic electrons of the standard beta-beam, as the atomic electrons of the ions cannot ions cannot be fully strippedbe fully stripped• Partly charged ions have Partly charged ions have a short vacuum life-timea short vacuum life-time against against collisions. The interesting isotopes have to have collisions. The interesting isotopes have to have

half-life < vacuum half-life ~ few min.

Electron neutrino fluxes Electron neutrino fluxes from EC and BBfrom EC and BB Distribution of neutrino energy per unit surface at the detector in the

forward direction:

2222

2

2

)1()1()( ee

iones yyyyygL

N

dSdE

Nd

• Notice: i) All Nuclear Physics input is under control ii) The Intensity increases like γ2 with the Lorentz factor. iii) The Monochromatic lineMonochromatic line E=2E=2γγEE00 is higher by 22γγ MeV to the end point MeV to the end point

of of the the ββ+ + spectrum

EC:

20

12

0 yE

Ey

0E

my ee

2

4422

11log15)892(1

60

1)(

e

eeeeee

y

yyyyyyg

eECe mQmQE 0

BB:

, and

Experimental Setups for Experimental Setups for the combined the combined experimentexperiment

Appearance Experiment : Electron Neutrino Flux × Oscillation Probability to muon neutrinos × CC Cross Section for muon production.

• I: CERN-Frejus (130 Km), γ=166 SPS • II: CERN-Canfranc (650 Km), γ=166 SPS• III and III-WC: CERN-Canfranc (650 Km), γ=369 Upgraded SPS• IV and IV-WC: CERN-Boulby (1050 Km), γ=369 Upgraded SPS

Detectors:• LAr or TASD, 50 kton Neutrino spectral information from CC muon events• Water Cerenkov, 0.5 Mton Neutrino energy from QE events only + inelastic events in a single bin, with 70% efficience

• The separation between the energy of the EC spike and the end point energy of the beta-spectrum is possible: if Eν(QE)>2γEo(β), since E

ν(true)> E ν(QE), the event must be attributed to the EC flux and hence, it is not necessary to reconstruct the true energy

Comparing baselines I Comparing baselines I and IIand II For the combined BB + EC fluxes with θ13=10 and δ=900

• The BB channel contributes very little to the overall sensitivity of the setup, due to the γ2 dependence. The bulk of the sensitivity is due to the EC channel placed on the first oscillation maximum

Comparing energies II Comparing energies II and III with the same and III with the same baselinebaseline Combination of BB and EC fluxes for θ13=10 and δ=900

γ=166 γ=369

• The sensitivity is better with the upgraded SPS energy• The relative role of the two BB and EC components is exchanged when going from II to III

Setup III: The virtues of Setup III: The virtues of combining energies from BB combining energies from BB and ECand EC

• Setup III: θ13=30, δ=900

BB EC BB+EC

• The power of the combination of the two channels is in the difference in phase and in amplitude between the two fake sinusoidal solutions, selecting a narrow allowed region in the parameter space

Set up III-WC : Disentangling Set up III-WC : Disentangling θθ13 13 and δ and δ

•

• Solutions, from discrete degeneracies included, for θ13=10 , 30 and for different values of the CP phase

• The increase in event rates improves the results substantially with respect to those results for Setup III, although not as much as the size factor between the two detectors.• The effects of the hierarchy clon solution are taken into account. The mass ordering can be determined for large values of the mixing angle.• The hierarchy degeneracy worsen the ability to measure δ for negative true values of δ.

Comparing III-WC and IV-WC Boulby provides a longer baseline L=1050 km than Canfranc L=650 km. This has two

contrasting effects on the sensitivity to measure CP violation: i) Sufficient matter effects to resolve the hierarchy degeneracy for small values of θ13;

ii) It decreases the available statistics

• The smaller count rate results in a poorer resolution. • The longer baseline allows for a good determination of the mass ordering, eliminating more degenerate solutions.

CP Discovery Potential for WC

Comparing the two locations of the WC detector, the Canfranc baseline has a significally (slightly) better reach for CP violation at negative (positive) values of δ than the Boulby baseline.

Canfranc Boulby

Mass hierarchy determination Fraction of δ for which the neutrino mass

hierarchy can be determined

• III-WC with present priors in the known parameters

• III-WC with negligible errors in the known parameters

• IV-WC with present priors in the known parameters

• The Boulby baseline, with its larger matter effect, is better for the determination of the mass hierarchy

ConclusionsConclusions

The two separate channels BB and EC have a limited overlap of the allowed regions in the (θ13, δ) plane, resulting in a good resolution on the intrinsic degeneracy.

The CP phase sensitivity is obtained by only using neutrinos, thanks to the Energy Dependence of the oscillation probability with the combination of the two BB and EC channels.

THE SPS UPGRADE TO HIGHER ENERGY (Ep = 1000 GeV) IS CRUCIAL TO HAVE A BETTER SENSITIVITY TO CP VIOLATION (the main objective of the third generation neutrino oscillation experiments)

IFF ACCOMPANIED BY A LONGER BASELINE ( Canfranc or Boulby).

THE BEST E/L FOR HIGHER SENSITIVITY TO THE MIXING U(e3) IS NOT THE SAME THAN THAT FOR THE CP PHASE. Like the phase- shifts, the effect of δ is easier to observe by going to the region of

the second oscillation.

Conclusions Setups III and III-WC, with the Canfranc baseline, have

larger counting rates and a better tuning of the beam to the oscillatory pattern, resulting in a very good ability to measure the parameters. These setups provide the best sensitivity to CP violation for positive values of δ.

For negative δ, the type of hierarchy cannot be resolved in some cases for these setups.

Setups IV and IV-WC, with the Boulby baseline, provide a better determination of the hierarchy and a good reach to CP violation for negative δ, even if the mass ordering is unknown.

THE COMBINATION OF THE TWO BB AND EC BEAMS

FROM A SINGLE DECAYING ION AND A FIXED γ BOOST ACHIEVES REMARKABLE RESULTS

Acknowledgements

Thanks to many colleagues and, particularly, to my collaborators:

J. Burguet-Castell, C. Espinoza, M. Lindroos, C. Orme, S. Palomares-Ruiz and S. Pascoli.

Thank you very much for your attention…