NNR05 Workshop
Neutrino Nuclear Responses in
Double Beta Decays and Low-energy Astro-neutrinos

I. Motivation and scope

Interest of neutrinos (ν) has recently been sharpened by the discovery of the neutrino oscillations. Fundamental properties of ν’s and ν nuclear interactions are studied in nuclear micro-laboratories as well. Neutrino-less double beta decays (ββ) are sensitive and realistic probes for studying neutrino masses and the Majorana nature. Solar and supernova neutrinos are of great interest for particle and astro nuclear physics.

Neutrino nuclear responses are crucial for neutrino studies in nuclei. Nuclear responses for ββ decays are described in terms of nuclear matrix elements. They have extensively been studied theoretically in terms of nuclear models. However, calculated values are sensitive to nuclear parameters used in the calculations. Thus experimental studies of nuclear responses are useful for checking the calculations and for providing data relevant to the nuclear responses.

Neutrinos involved in ββ and astro nuclear physics are mostly low-energy neutrinos with 0.01 – 0.1 GeV. Accordingly, the neutrino nuclear responses are spin isospin responses with low multi-polarities of L= 0~3. Thus they can be studied experimentally by using low-energy probes with E < GeV. In fact, the spin isospin responses for the lowest multi-pole of L=0 have extensively been studied at RCNP, MSU, KVI, TUDA and others. High E-resolution systems there are very powerful for studying ν nuclear responses for low-lying states. Medium energy photons at JASRI/SPring-8 can be used to study CC and NC weak currents. J-PARC is of potential interest for low-energy ν beams to be used for ν response studies.

The present workshop aims at productive discussions on ββ-ν responses (nuclear matrix elements) and related ν responses in astro particle physics to find possible ways to study the ν responses with L>0, which are crucial for neutrino-lass ββ decays and SN neutrinos, and others and to promote corporative works internationally.
This workshop is in line with the recent international statement;
http://www.rcnp.osaka-u.ac.jp/~ejiri/DBD-Lett and the statement at the recent workshop at Durham in May 2005.