Search for CP violation in the lepton sector

n

Cristina VOLPE

(Institut de Physique Nucléaire Orsay, France)

Introduction

OUTLINE

CP violation searches with future facilities CP violation searches and astrophysics Conclusions

Major advances in neutrino physics

L SOURCE n

e

n m DETECTOR n

e

n m Pontecorvo, 1957 AN IMPRESSIVE PROGRESS IN THE LAST DECADE in our knowledge of its properties.

1.6

1.4

1.2

1 0.8

0.6

oscillation decoherence decay

Many puzzles have been solved with an incredible impact on various domains of physics.

0.4

0.2

1 10 10

2

L n /E n 10

3

ratio [km/GeV] 10

4

Among the fundamental implications…

Neutrinos are massive particles

, contrary to what was believed for decades .

The origin of neutrino mass and its smallness needs to be understood.

The solar neutrino deficit problem is clarified.

We understand the energy production in stars.

It opens a new possibility to understand the matter versus anti-matter asymmetry in the Universe.

A key step for one of the major open questions in modern cosmology.

THE 3-flavours OSCILLATION PARAMETERS

     n n n n

e

e

n m n t t      In the case of three families, there are three mass eigenstates ( n

1 ,

n

2 ,

n

3

) and three flavour eigenstates ( n

e ,

n m

,

n t ).

n

3

n m  m 21 2  m 32 2 n t n

1

q

12

q

23

q n e

13

i

 1 , n  2 3 

m i

2 

m

2 2 

m

2 1 

m

Only two  m 2 2 3 

m

2 2 

m

2 1 

m

2 3 are independent.

The two basis are related by a unitary matrix, called the Maki-Nakagawa-Sakata Pontecorvo (MNSP) matrix.

c ij

 cos q

ij s ij

 sin q

ij

      1 0 0 

c

0

s

23 23

s

0 23

c

23           q 23 

s c

0 13 13

e i

 0 1 0

s

13

c e

0  13

i

 q 13           

c

12 0

s

12

s c

12 12 0 q 0 0 1           n n n

1

2 2

3

     THE CP violating phase INTRODUCES A n n ASYMMETRY.

THE key OPEN QUESTIONS

> The third mixing angle q

13

Double-CHOOZ, Daya-Bay, T2K,..

> The Dirac phase > The Majorana phases from double-beta decay experiments > The absolute mass scale > The mass hierarchy KATRIN, MARE,… supernovae, n -factories, double-beta,… > The neutrino nature Gerda, Cuore, Super-Nemo,…

A wealth of experiments are under construction or at a R&D level.

exciting discoveries might be close…

q

13

– expected sensitivities

P. Huber, M. Lindner, T. Schwetz, W. Winter, arXiv: 0907.1861

Discovery potential (90% CL) for sin 2 from reactors and accelerators 2 q 13 THE VALUE OF Q 13 CRUCIAL FOR FUTURE STRATEGIES.

CPV sensitivity

P. Huber, M. Lindner, T. Schwetz, W. Winter, arXiv: 0907.1861

sensitivity limits (90% CL) from T2K, NO n A and reactors LONG-TERM expensive PROJECTS might be necessary.

Long-term accelerator projects

> Super-beams intense conventional beams from muon and pion decay > Beta-beams – intense and pure neutrino beams from boosted accelerated ions > Neutrino factories – intense neutrino beams from stored muons THE GOAL : to investigate very small hierarchy. Q 13 values, the Dirac CP phase and the mass

The beta

6 6 n

e

ions at rest

-beam concept

6 He 6 Li n

e

ions are boosted neutrino beams Zucchelli, PLB 2002 Average neutrino energy :

E

n

= 2

g

Q

b , Flux emittance :

1/

g

.

No beam associated background (the n -beams are produced from primary particles).

Several beta-beam scenarios proposed

See Volpe, Topical Review on “Beta-beams”, J.Phys.G34, R1 (2007) hep-ph/0605033

Low-energy

g

= 5 -14

C. Volpe, Journ. Phys. G. 30 (2004), hep-ph/0303222 .

CP

Beta-beams

P. Zucchelli, Phys. Lett. B 2002

High-energy and very high-energy

g

= 100

g

= 300

g

= 1000

J. Burguet-Castell, D. Casper, JJ Gomez-Cadenas, P. Hernandez, F. Sanchez, Nucl. Phys. B695, 217 (2004), hep-ph/0312068.

Electron-capture

J. Bernabeu, J. Burguet-Castell, C. Espinoza, M. Lindroos, JHEP 0512 (2005) 014, hep-ph/0505054 .

THE standard baseline scenario

EURISOL

Proton driver

SPL

P. Zucchelli, Phys. Lett. B (2002) B. Autin et al. , J. Phys. G

To a far detector

29 (2003) 1785.

n

e

ISOL production

ISOL target & ion source

beam preparation

ECR pulsed

Ion acceleration

Linac, 0.4 GeV

PS SPS

93 GeV

n source decay ring 6 He , 18 Ne

Lss = 2.5 km

acceleration at medium energy

RCS, 1.5 GeV 8.7 GeV

Acceleration to final energy

PS and SPS

IT REQUIRES OF VERY THE PRODUCTION AND ACCELERATION INTENSE RADIOACTIVE IONS BEAMS (RIB) .

EURISOL Design Study (FP6 2005-2009) -> Conceptual Report

THE standard baseline scenario

65 m n

e FREJUS MEGATON DETECTOR

60 m Frejus Underground Laboratory

THE SEARCH for CP and T violation:

n

e

 n m

(

b

+)

n m  n

e (

p

+ ) MULTIPURPOSE DETECTOR

CP violation , (relic) supernova neutrinos and proton decay.

CP T

n

e

 n m

(

b

-)

n m  n

e (

p

)

(with Beta-beams) (conventional beams) Three technologies under study (water Cherenkov, scintillator, liquid argon)

LAGUNA Design Study (2008-10)

IN THE LITERATURE…

Two kinds of studies of the physics reach can be found : 1) based on values of the ion intensities and boosts that are obtained extrapolating well-known technologies and existing accelerators.

2) based on values of the ion intensities and boosts that are treated as “free” parameters, with the aim of exploring the conditions to achieve optimal sensitivities.

Sensitivity to

Q

13

and CP violation

After 10 years running (5+5, or 2+8) with 440 kton detector, 5.8 (2.2) 10 18 6 He ( 18 Ne)/s, g = 100 Mezzetto 2005 Campagne, Maltoni, Mezzetto, Schwetz, JHEP 0704:003 (2007). hep-ph/0603172

Synergy with athmospherics

First proposed in : .

Hubert, Maltoni, Schwetz, Phys. Rev. D 71, 053006 (2005). hep-ph/0501037.

Campagne, Maltoni, Mezzetto, Schwetz, JHEP 0704:003 (2007). hep-ph/0603172 Helps identify the mass hierarchy and the octant degeneracy.

Comparison with other facilities

1 0.6

b beam

ISS study

10 -5 10 -4 10 -3 sin 2 2 q 13 International Scoping Study Physics Working Group, arXiv: 0710.4947 .

THE BETA-BEAM PROJECT IS A COMPETITIVE option.

LOW ENERGY BETA-BEAMS

C.Volpe, J Phys G 30 (2004).

A proposal to establish a facility for the production of intense and pure low energy neutrino beams (100 MeV).

E U R I S O L

PS

BASELINE

SPS

storage ring n n close detector PHYSICS POTENTIAL n -nucleus cross sections (detector’s response, r-process, 2 b decay) fundamental interactions studies (Weinberg angle , CVC test, m n ) astrophysical applications PHYSICS STUDIED WITHIN THE EURISOL DS (FP6, 2005-2009)

EURISOL DS (2005-09): Some conclusions

Two sets of candidate ions are being considered : 6 He/ 18 Ne and 8 B/ 8 Li Three ion production techniques have been and will be investigated.

-the standard ISOL technique : the requires 6 He intensity is achievable, the 18 Ne intensity lower - direct production (M.Loislet-Leuven, M. Hass-Soreq, GANIL) : 6 He and 18 Ne intensities should be achievable - storage ring production : suitable for 8 B/ 8 Li. C. Rubbia et al, NIM A 568(2006) 475. The direct and storage ring production methods will be studied within EUROnu. If the ions are bunched to suppress the backgrounds, there might be a conflict with the EURISOL requirements.

The ion stacking method in the storage ring ok. IMPORTANT PROGRESS ON THE FEASIBILITY PERFORMED.

Further work will be done within EUROnu both on the feasibility and on the physics reach.

CP violation searches and astrophysics

Solar neutrinos

H.Minakata and S. Watanabe, Phys. Lett. B 468, 256 (1999)

.

UHE neutrinos

Walter Winter, Phys. Rev. D 74, 033015 (2006)

.

Supernova neutrinos

E

. Akhmedov, C.Lunardini & A.Smirnov, Nucl.Phys.B643 (2002) 339.

A. B. Balantekin, J. Gava, C. Volpe, PLB662, 396 (2008), arXiv:0710.3112. J. Gava, C. Volpe, Phys. Rev. D78, 083007(2008), arXiv:0807.3418.

J Kneller and G.C. McLaughlin, arXiv:0904.3823.

Core-collapse supernovae (SN)

n t NS n m n

e

99 % of the energy is emitted as neutrinos of all flavours in a short burst of about 10 s .

A possible site for the nucleosynthesis of the heavy elements, but present calculations fail to reproduce the observed abundances. n -PROPERTIES CAN HAVE EFFECTS IN THE STAR OR IMPACT THE SIGNAL IN A SN OBSERVATORY.

Neutrino propagation in media

n e

e

W e n

e

V ( r ) G F r e .

induces a n PROPAGATION IN SN : Neutrino-neutrino interaction is important.

the beautiful explanation of the « solar neutrino deficit » problem !

are non-linear.

t=1s t=1.5s

There are also shock wave effects. These engender multiple resonances and phase effects.

E n =20 MeV Turbulence effects are just being considered.

See the review from Duan and Kneller, arXiv:0904.0974

IMPRESSIVE PROGRESS IN THE LAST FEW YEARS !

A lot of work still needs to be done …

The search for the third

n

-mixing angle

First calculation including the nn interaction and shock wave effects .

Gava, Kneller, Volpe, McLaughlin, Phys. Rev. Lett. 103 (2009), arXiv:0902.0317

adiabatic

FLUXES ON EARTH

n

e

+ p n + e+ non-adiabatic 29 MeV 15 MeV

POSITRON TIME SIGNAL

The dip (bump) can be seen at 3.5 (1) sigma in Super-Kamiokande if a supernova at 10 kpc explodes..

A SIGNATURE IN THE POSITRON TIME SIGNAL IF sin 2 2 q 13 > 10 -5 OR sin2 q 13 < 10 -5

CP violation and core-collapse SN

A. B. Balantekin, J. Gava, C. Volpe, PLB662, 396 (2008), arXiv:0710.3112

We have demonstrated under which conditions there can be CP violating effects in supernovae. Here the main steps :

The neutrino evolution equations in matter are with vacuum term matterterm the T23 basis factorizes out easily and gives:

CP violation and core-collapse SN

This leads to the two following relations: Evolution operator in the T 23 The electron neutrino survival probability does not depend on  .

basis

We have demonstrated that these relations also hold when the

nn

interaction is included.

J. Gava, C. Volpe, Phys. Rev. D78, 083007(2008), arXiv:0807.3418.

NS 20 Km The neutrinosphere is where neutrinos finally decouple from matter.

Tree level

L

n

-

neutrino fluxes at the neutrinosphere (Fermi-Dirac or power law ) The electron neutrino flux in the SN: AT TREE LEVEL THE n e-FLUXES DO NOT DEPEND ON THE CP PHASE.

Conditions for CP effects in SN

In the Standard Model loop corrections for the v interaction with matter should be included.

Beyond the Standard Model might introduce differences in the n m and n t interaction wiht matter (Flavor Changing Neutral Currents , …).

at the neutrinosphere AND also The n propagation Hamiltonian does not factorize any more !

THERE CAN BE CP-VIOLATION EFFECTS IN SUPERNOVAE.

Numerical results : effects on the flux ratios

200 Km in the star

Standard MSW, tree level More realistic case !

n n interaction and 1-loop Inverted hierarchy and small J. Gava, C. Volpe, Phys. Rev. D78, 083007(2008), arXiv:0807.3418.

EFFECTS OF 5-10 % ON THE ELECTRON NEUTRINO FLUXES in the SUPERNOVA.

Numerical results : effects on Ye

The electron fraction is a key parameter for the r-process nucleosynthesis : A. B. Balantekin, J. Gava, C. Volpe, PLB662, 396 (2008), arXiv:0710.3112

VERY SMALL EFFECTS ON THE ELECTRON FRACTION.

Conclusions

The value of

Q 13

sets the strategy for CP violation searches. Beta-beams - A very competitive option.

-The report on the feasibility from the EURISOL DS soon available. Future studies (ex. ion intensity within EUROnu).

Neutrinos in core-collapse supernovae : We have set the basis for the exploration of CP violation in dense media.

Thank you!

Danke.

Grazie.

Merci.

Andromeda (M31)