Energy Dependence and Physics Reach in regard to Beta/EC Beams

J. BernabeuU. Valencia and IFIC

B. Pontecorvo School

September 2007

Energy Dependence and Physics potential in regard to Beta/EC Beams

Third generation proposals for the CP phase δ ß Beams: combination 6He ()- 18Ne() at the same γ EC Beams: combination of two energies for the same ion

150Dy Comparison between ( low energy Ep(SPS) ≤ 450 GeV,

Frejus) and (high energy Ep(SPS) ≤ 1000 GeV, Canfranc )

The Pontecorvo MNS Matrix

3

2

1

Ue

10000

0010

0

00

001

1212

1212

1313

1313

2323

2323 cssc

ces

esc

csscU

i

i

For Flavour oscillations U: 3 mixings, 1 phase

Atmospheric KEK More LBL-beams

Appearance e!Reactor Matter in Atmospheric…

SolarKAMLAND

Even if theyare Majorana

After diagonalization of the neutrino mass matrix,

Beta Beam Concept P. Zuchelli

Design and performance: M. Benedikt, M. Lindroos, M. Mezzetto…

Neutrino Oscillation Physics

)4

sin(4

)4

cos(~

)4

(sin2sin

)4

(sin2sin)(

ceInterferen

213

212

213

Solar

2122

1222

23

cAtmospheri

2132

1322

23

ELm

ELm

ELmJ

ELmc

ELmsP e

• After atmospheric and solar discoveries and accelerator and reactor measurements → 13 ,

Appearance probability: For Beta Beams,

• 6He antineutrino beam combined with 18Ne neutrino beam • 5 years each• Intensity of 2.9x1018 6He and 1.1x1018 18Ne decays per year • Detection by charged-current event with a muon in the final state 440 Kton fiducial mass water Cherenkov detector

Beta Beams

• Neutrino Continuous Spectrum implies the need of the reconstruction of the energy in the detector for each event, based on the quasi elastic channel

6 He 18 Ne

Fixing the CERN-Frejus baseline Is the sensitivity to CP

Violation and θ13 changing with energy?• For γ > 80, the sensitivity changes rather slowly because the flux at low energies does not reduce significantly.• Then it is not advantageous to increase the energy if the baseline is not correspondingly scaled to remain closed to the atmospheric oscillation maximum: remember L/E ! J. Burguet-Castell et al.

Fixing γ• The maximum energy reachable with the present SPS is γ=150.

• L = 300 Km is clearly favoured, but …

• Is the sensitivity to θ13 and δ changing with the baseline?

Comparison of two set-ups

Setups with the same γ for both ions

Set up I : γ =120, L=130 Km (Frejus)

Set up II : γ =330, L=650 Km (Canfranc)

Set up II needs the upgrade of SPS until Ep=1000 GeV

Conclusion: Set up II is clearly better. It provides better precision and resolves the degeneracies.

J. Burguet - Castell et al.

Comparison of two set-ups

CP violation exclusion plot at 99% CL.

Exclusion plot for θ13 at 99 % CL.

Outlook: R & D effort to design Beta-beams for the upgraded CERN-SPS (Ep=1000 GeV) appears justified.

Interest of energy dependence in suppressed neutrino oscillations

• Appearance probability:• |Ue3| gives the strength of P(ne→νμ)

δ acts as a phase shift

• δ gives the interference pattern: CP odd term is odd in E/L• This result is a consequence of a theorem under the assumptions of CPT invariance and absence of absorptive parts

This suggests the idea of a monochromatic neutrino beam to separate δ and |Ue3| by energy dependence!

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sin(4

)4

cos(~

)4

(sin2sin

)4

(sin2sin)(

ceInterferen

213

212

213

Solar

2122

1222

23

cAtmospheri

2132

1322

23

ELm

ELm

ELmJ

ELmc

ELmsP e

Interest of energy dependence in suppressed neutrino oscillations

Canfranc Frejus

Neutrinos from electron capture

Electron capture:

From the single energy e--capture neutrino spectrum,we can get a pure and monochromatic beam byaccelerating ec-unstable ions No need to reconstruct the neutrino energy in the detector !

2 body decay! a single discrete energy ifa single final nuclear level is populated

How can we obtain a monochromatic neutrino beam?

Forward directionZ protonsN neutrons

Z-1 protonsN+1 neutrons

boostJ. Bernabeu et al

An idea whose time has arrived !

- In heavy nuclei (rate proportional to square wave function at the origin) and proton rich nuclei (to restore the same orbital angular momentum for protons and neutrons ) Superallowed Gamow-Teller transition The “breakthrough” came thanks to the recent discovery of isotopes with half-lives of a few minutes or less, which decay in neutrino channels near 100% through electron capture to a single Gamow-Teller resonance.

Implementation● The facility would require a different approach to acceleration and storageof the ion beam compared to the standard beta-beam, as the atomic electrons of the ions cannot be fully stripped.● Partly charged ions have a short vacuum life-time. The isotope we discuss ( 150Dy) has a half-life ≤ vacuum half-life ~ few minutes.● For the rest, setup similar to that of a beta-beam. Due to possible problems with space charge if we want to accumulate 1018 decaying ions per year Look for an isotope with all the nice properties pointed out before and a half- life near 1 sec.

Electron neutrino flux

Notice the proportionality with γ2 and the monochromaticity• Strategy:

Put all the intensity at the energy in which the sensitivity to Physics is higher !

Experimental set-up for EC

5 years 90 (close to minimum energy to avoid background) 5 years = 195 (maximum achievable at present SPS)

L = 130 km (CERN-Frejus)

● 440 kton water ckov detectorAppearance &Disappearance

● 1018 decaying ions/year

Versus 10 years for each γ the virtues of two energies

• Set up I (low energy, Frejus):

• Combine two different energies for the same ion and baseline

• Set up II (high energy, Canfranc):

5 years 195 (maximum achievable at present SPS) 5 years = 440 (maximum achievable at upgraded SPS)

L = 650 km (CERN - Canfranc)

Set up I - Disentangling θ13 and δ

Much betterseparation for two different energies, evenwith lower statistics

Access to measure the CP phase as a phase-shift

The virtues of two energies

130 km

Set up I: Fit of 13 , from statistical distribution

The principle of an energy dependent measurement is working and a window is open to the discovery of CP violation

Set up I:Exclusion plot: sensitivity

Total running time: 10 years... Significant below 1o

013

Set up I: Exclusion plot: CP sensitivity

Total running time: 10 years... Significant for θ13 > 40

Set up II: The virtues of combining two energies

650 km

Conclusion: the separation between 13 and is much better than that for set up I

Set up II: Fit of 13 , from statistical distribution

Conclusion: the precision reachable for the CP phase is better than that for set up I <-> WITH NEUTRINOS ONLY, AT TWO SELECTED DIFFERENT ENERGIES

δ

θ13

Set up II: θ13 sensitivity

0.1 – 0.4 degrees, depending on δ

Set up II: Exclusion plot: CP sensitivity

Without any previous information on θ13 …

Set up II: δ sensitivity

θ13

δ

δ sensitivity < 45º for θ13 ≥ 3 º. Asymptotically, a δ sensitivity of ± 18º

99 % C L

Set up II: Exclusion plot: CP sensitivity

IMPRESSIVE !!!If θ13 previously known …

Set up II: δ sensitivity

δ sensitivity < 45º for θ13 ≥ 0.4 º. Asymptotically, a δ sensitivity of ± 8º

δ

50

-50

θ13

1 3

99 % C L

Conclusions The simulations of the Physics Output for both Beta and EC beams indicate: THE 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.

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 presence of δ is easier to observe in the region of the second oscillation: Set up II in EC beams has an

impressive sensitivity to CPV, particularly if the mixing is previously known. The mixing is better seen around the first oscillation maximum, instead.

Besides the feasibility studies for the machine, MOST IMPORTANT FOR PHYSICS IS THE

STUDY OF THE OPTIMAL CONFIGURATION BY COMBINING - Low energy ( < 2017(?)) with high energy (> 2017(?)) - Frejus (L=130 Km) with Canfranc (L=650 Km) , i.e., the decay “ring” should be a

triangle and not a rectangle. - EC monochromatic neutrinos with 6He beta- antineutrinos.

MUST DEFINE A PROGRAM TO DETERMINE INDEPENDENTLY THE RELEVANT CROSS SECTION

The result of the synergy of Neutrino Oscillation Physics with LHC- Physics (SPS upgrade) and, in the case of Beta/EC Beams, with Nuclear Physics (EURISOL) for the Facility at CERN, could be completed with the synergy with Astroparticle Physics for a Multipurpose Detector, common to neutrino oscillation studies with terrestrial beams, Atmospheric Neutrinos (neutrino mass hierarchy), supernova neutrinos and Proton decay!!!

Outlook

MUCHAS GRACIAS!