Institut de Physique Nucléaire Orsay, France Physics with a very first Low-energy Beta-beam n Cristina VOLPE Institut de Physique Nucléaire Orsay, France

P L A N n-Nucleus Interactions: Low-energy Beta-beams Site Nuclear Astrophysics - Nuclear Structure Studies - Neutrino Physics P L A N Site Status and Pespectives

n n n g The beta -beam concept 6He 6He Zucchelli, PLB 2002 Q 1/ n 6He Lorentz boost high g n 6He -beam concept

Low-energy Beta-beams C. Volpe, Journ. Phys. G. 30 (2004), hep-ph/0303222. THE PROPOSAL To exploit the beta-beam concept to produce intense and pure low energy (10-100 MeV) neutrino beams. PHYSICS POTENTIAL boost n 6He Neutrino-nucleus interaction studies. n 6He Neutrino properties, like the n magnetic moment. … A BETA-BEAM FACILITY FOR LOW ENERGY NEUTRINOS.

n-Nucleus studies: Motivation Neutrino experiments STANDARD MODEL and BEYOND NUCLEAR PHYSICS C N ne e Supernovae, Nucleosynthesis ASTROPHYSICS Neutrino-Nucleus Interactions A topic of current great interest for various domains of physics.

Understanding Nucleosynthesis The site where the heavy elements are synthetized is not known. Supernova type II explosions: 99 % of the energy is emitted as neutrinos. Calculations of abundances. neutrino capture ! N N+1 N-1 Z Z+1 neutron capture b-decay NEUTRONS PROTONS neutron-rich (exotic) nuclei. n-NUCLEUS INTERACTIONS ARE NEEDED.

Meyer, McLaughlin, Fuller, 1998.

NEUTRINOS AS a PROBE for NUCLEAR STRUCTURE STUDIES. C. Volpe et al., Phys. Rev. C65, 2002. ne + 208Pb 208Bi + e- E X A M P L E <Ene >= 15 MeV 2+ 1- 3- 1- 30 MeV 1+ 0+ Bi Pb 50 MeV The contribution to the total cross section increases for increasing impinging neutrino energy. no experimental information is available.

Neutrinoless Double-beta Decay n  n n Dirac n Majorana n = n How do we search for the n-nature? ? 76Ge 76As 76Se bb(0n) Klapdor et al., 2001 > 1.9 1025 y (90% C.L.) < mn> < 0.3 – 1.0 eV The present best limit. Beyond the Standard Model (e.g. exchange of massive Majorana neutrinos) 2b(0n): 2n  2p + 2e- Lepton-violating process

Theoretical Situation G : phase space factor M : nuclear matrix elements <mn> : effective neutrino mass G( ) M2 <mn>2 Q5 bb 1 = Theoretical predictions (mainly performed within Shell Model and QRPA) exhibit significant variations of the neutrinoless double-beta decay half-lives for the same candidate emitter. This has important implications, in particular it translates in an uncertainty on the n-mass. REDUCING THE UNCERTAINTIES: A MAJOR CHALLENGE.

76Ge Bobyk,Kaminski,Simkovic,PRC2001 76Se 76Ge 76As bb(0n) m b Several processes have been considered to constrain the nuclear matrix elements, in particular beta-decay, muon capture, 2b(2n), charge-exchange reactions. C.Volpe, hep-ph/0501233, to appear in Journ. Phys. G. One can show that the states involved in neutrinoless double beta decay due to the exchange of a massive Majorana neutrino are the same states as those excited in neutrino-nucleus interactions.

n-Nucleus Interactions: Present status Neutrinos probe nuclei over a wide energy range. Nuclear Degrees of Freedom Nucleon Degrees of Freedom SUPERNOVA ATMOSPHERE SUN,REACTOR ACCELERATORS 10 50 100 1000 (MeV) 500 n-Energy EFT, Microscopic Approaches (RPA, Shell Model), EPT,… Fermi Gas Experimental data are very scarce (deuteron and iron, carbon). Theoretical predictions are absolutely necessary. The interpolation between these two regimes as well as the extrapolation from stable to exotic nuclei are needed.

Low-energy Beta-beams C. Volpe, Journ. Phys. G. 30 (2004), hep-ph/0303222. THE PROPOSAL To exploit the beta-beam concept to produce intense and pure low energy (10-100 MeV) neutrino beams. PHYSICS POTENTIAL boost n 6He Neutrino-nucleus interaction studies. n 6He Neutrino properties, like the n magnetic moment. … A BETA-BEAM FACILITY FOR LOW ENERGY NEUTRINOS.

Neutrino-nucleus measurements SITES Neutrino-nucleus measurements Two options studied : Large ring (standard b-beam) Small Ring (ex. GSI future ring) Serreau and Volpe, hep-ph/0403293, PRC70 (2004). PS SPS E U R I S O L n Beta-beam baseline at CERN Storage Ring close detector d length of the straight sections L total length

SNS Proposal at OAK Ridge Laboratory Y. Efremenko, 2004. From the decay of pions and muons SCIENTIFIC OPPORTUNITIES (Journ. Phys. G29, 2003) Neutrino-nucleus interaction studies Neutrino-oscillation searches Non-standard components of the weak interaction We have taken similar detectors.

n-Nucleus Rates at low-energy b-beams J. Serreau and C. Volpe, PRC70 (2004) hep-ph/0403293. Neutrino Fluxes g n <En>~2gQb/2 Small Ring : Lss = 150 m, Ltot = 450m Large Ring :Lss = 2.5 km, Ltot =7.5 km Small Ring Large Ring 25779 82645 103707 7922 9453 1956 ne + 208Pb ne + 16O ne + D Events per year for g=14 Mass (tons) 35 952 360 INTERESTING INTERACTION RATES CAN BE OBTAINED. A SMALL DEVOTED STORAGE RING IS BETTER.

Low-energy Beta-beams Feasibility Study within EURISOL Design Study Beta-beam baseline at CERN E U R I S O L Acceleration issues SPS M. Benedikt and M. Lindroos, CERN Storage Ring PS Storage Ring Size Space-charge effects Duty cycle Intensities n close detector n J. Payet and Chancé, CEA Saclay, France Detectors issues (remember LSND and KARMEN) THE FEASIBILITY STUDY just STARTED.

Conclusions and Perspectives The study of neutrino-nucleus interactions at low energy represents an interesting axis of research. This is of interest for different domains of physics. Low-energy beta-beams require a small storage ring. The feasibility study has just started. A detailed study of the detector issues, at least for one typical example, is needed. Low-energy beta-beams might furnish the very first beta-beam.