BOREXINO

Collaboration:

- Italy: Universita' e INFN di genova, Milano, Pavia, Perugia and LNGS
- Belgium: I.R.M.M. European Joint Research Center - Geel
- Canada: Queen's University - Kingston
- France: College de France - Paris
- Germany: Max-Planck-Institut fuer Kernphysik Heidelberg, Technische Universitaet Muenchen
- Hungary: KFKI-RMKI Research Institute for Particle & Nuclear Physics Budapest
- Poland: Institute of Physics, Jagellonian University, Cracow
- Russia: J.I.N.R. DUBNA, Kurchatov Institute - Moscow
- USA: Bell Laboratories - Lucent Technologies, Massachusetts Institute of Technology, Princeton University, Virginia Polytechnic Institute

Location of the experiment: Laboratorio Nazionale del Gran Sasso (LNGS)

National Responsible: G. Bellini (Mi)

1. Goal of the experiment

Borexino, a solar neutrino real time experiment at LNGS, makes use of the neutrino-electron scattering reaction to detect neutrinos emitted from the Sun. It is the only experiment in real time planned for the next few years, having a threshold below 1 MeV.

In Borexino we are mainly interested in the observation of the 7Be neutrinos, which is a monochromatic line at 863 keV.

More on the experiments…

2.

Activities during 2001

The major accomplishment in the year 2001 concerns the installation of important parts of the detector and of the ancillary plants. The installation of phototubes on the sphere and relative cables and electronics are completed. The optical fibers system for scintillator and buffer monitoring and for photomultipliers (PMT’s) equalization are installed.

A first test with a complete electronis, daq and online monitor system of the phototubes in the upper part of the sphere was already done.

The DataBase for on line and offline, the online monitor and the offline reconstruction program are almost completed.

A new measurement phase with the Counting Test Facility, for scintillator qualification is in progress.

The following achievements have been obtained:

Cables, PMTs, optical fibers installation completion. | 1-10-2001 | 100%
Data Acquisition System and electronics testing. | 1-12-2001 | 100%
Completion of detector filling station. | 31-12-2001 | 90%
PC procurement for testing in Counting Test Facility (CTF) at LNGS. | 1-10-2001 | 80%

- The scintillator procurement for CTF is on time

Milestones 2002

Completion of scintillator testing with CTF | 1-02-2002
Inner Vessel installation (Princeton Univ. responsibility). | 1-03-2002
Scintillator (PC) trasportation for the inner vessel | 1-03-2002
Water filling of the external tank. | 1-05-2002
Buffer PC procurement and Borexino filling | 1-06-2002
Borexino operational. | 1-09-2002

3. INFN contribution to the experiment in terms of manpower and financial support

Manpower: 48 researchers (31 FTE), 9 technicians (8 FTE)

Budget for the year 2002: 3721 kEuro

4. Number of publications in refereed journals (in 2001): 3

5. Number of talks to conferences (in 2001): 4

6. Number of undergraduate and doctoral thesis on the experiment:

- n. 2 Ph.D.
- n. 5 Laurea Diplomas

7. Leadership roles and primary responsibilities of the experiment

- G. Bellini(Mi) is the spokesman of the experiment.
- G. Manuzio (Ge) is a member of the Executive Committee.
- G. Ranucci (Mi) is the Project Manager (in 2002)

Several physicists of the Italian part of the collaboration are responsible of some of the main subsystems and plants of the experiment:

- M. Giammarchi - liquid plants;
- G. Ranucci – PMT’s;
- M. Pallavicini - Electronics, Daq;
- D. Giugni - Engineering;
- R. Tartaglia - Site manager,
- S. Malvezzi – Calibrations;
- E. Meroni – Software;
- G. Testera - Scintillator

8. Innovative instruments

The Counting Test Facility has been demonstrated to be one of the lowest background facilities in the World.

The collaboration has developed measurement techniques for radioassay of constructing materials, water, and nitrogen at unprecedented sensitivity levels.

The levels of purification of liquid scintillator and the sensitivities in the low radioactivity measurements reached by the collaboration represent a record in this field.

9.Competing experiments

There are no direct competitors in the near future for the 7Be neutrino measurements.

However, the Japanese experiment Kamland, after a first measurement phase for reactor antineutrinos, that aims to explore the LMA solution at larger mass, could be upgraded to attempt the 7Be measurement.

10. International committee which has reviewed the experiment

The experiment is continuously reviewed by the Committee II of INFN, by the NSF, by the German funding agencies, and by the International Scientific Committee of the Gran Sasso Laboratory.