1 BOREXINO on behalf of the BOREXINO collaboration Zaymidoroga O.A Spokesman from Jinr Bellini G Spokesman from Italy

2 Outline BOREXINO: project & status Method of investigation Technical aspects Requirements and realization of purification of materials CTF: analysis of data Physical results obtained on CTF prototype Outlook

3 Tasks of Borexino An international project for the precise and direct determination of the flux of the solar neutrinos produced in the Be-7 electron capture process in the Sun and study the phenomenon of neutrino oscillation for low energy solar neutrino spectrum using calorimetric, liquid scintillator and low background detector Borexino situated in the underground Gran Sasso laboratory.A pilot program for the full-size detector, the Counting Test Facility- CTF, provided the convincing evidence that the technological challenge of the experiment, the achievement in the scintillator of unprecendented radiopurity levels were accomplished successfully, thus opening the way to the realization of the milestone of experiment-Borexino in the period ,first priority.

4 238 U contamination Method: identification of the sequence 214 Bi(  )  214 Po( ,  =235  s)  210 Pb No internal events cut: 238 U from 214 Bi  214 Po :  0.03 counts/1ton/day (5.7  0.3  g/g)

5 232 Th contamination Method: Maximum likekihood to identify the sequence 212 Bi(  )  212 Po( ,  =432ns)  208 Pb Using only internal events: r  0.6m BiPo: counts/1ton/day (68.3%) Th eq :  g/g

6 The CTF as a tool for tuning the apparatus before filling CTF main goalCTF main goal: assessment of the performances of the different BOREXINO sub-systems The CTF to test the C14 content in the PC The CTF to test the efficiency of the three purification methods The CTF to test the cleanliness of the apparatus

7 Contamination from 14 C

8 CTF: PC intrinsic contamination Study of the CTF events radial distribution Set of selected events in the Neutrino Window [0.25,0.8]MeV devided into: bulk surface + external For this specific example: Bulk = counts/day Bulk  = counts/1ton/day Count rate reduced by: PC distillation (good expected reduction factor) Better N 2 (for BX much less Ar & Kr contamination)

9 BOREXINO: detector 18m 13.7m Main Goal:Main Goal: sub-MeV neutrinos detection (solar-Be7) Target mass = 300/100tons organic scintillator PC + PPO(1.5g/l) Detection by ES  careful background subtraction + high level of radiopurity required

10 BOREXINO: radiopurity requirements Typical Conc. Borexino level 14 C 14 C/ 12 C< C/ 12 C~ U, 232 Th~ 1ppm in dust ~ 1ppb stainless steel ~ 1ppt IV nylon ~ g/g(PC) K nat ~ 1ppm in dust< g/g(PC) 222 Rn~ 10Bq / m 3 in air ~ 70  Bq / m 3 in PC (0.3ev/day/100tons) 85 Kr, ( 39 Ar)1.1Bq/m 3 (13mBq/m 3 ) in air 0.16  Bq/m 3 (0.5  Bq/m 3 ) in N events/day/ton If secular equilibrium is broken: contaminants such as 210 Pb, 210 Po may be a serious problem

11 BOREXINO: expected signal  Neutrino window [0.25,0.8] MeV  C14/C12 =  U,Th at g/g  K at g/g  effic.for Alfa/BetaD=95%  Ar and Kr according to requirements S/N ~ 1.2 Muon-induced background according to T. Hagner et al. Astrop. Phys. 14(2000)33-47

12 BOREXINO: subsystems Scintillator purification systems:  Water extraction  Vacuum distillation  Silicagel adsorption CTF + DI Water plant Storage tanks: 300tons of PC detector

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14 85 Kr activity after N 2 stripping radial cut at 70cm  85 Kr activity from ML fit : events/day (68.3%)  events/kg/day (95%) with 259days of DAQ  if 85 Kr which comes with N 2 is in equilibrium with the PC: expected ~11 cpd Model: f(t) = B + A Exp[-t/1.46]/1.46 Radial cut: r  70cm Maximum likelihood fit

15 Dubna team(LPP) did the following: Dubna group of JINR has performed the following jobs in the frame of identifying common tasks and collaborating teams from both sides. - testing of of VME electronics for the experiment, - tuning flash electronics and analysis -participated in the PMT finishing, the mounting and cleaning -participation in production of the analog electronic modules for the experiment -proposed suggestion for the development detector with aim to upgrade Borexino prototype to be able to study solar pp-neutrino. -it were done the work for calibration big size of PMT in monitor and muon system(more than 2700PMT) Complete DAQ production and testing programm complex Only Dubna physicists suggested and made the analysis of the data of CTF-detector, which gives a new physical results

16 Total number of Publications for 3-years ●36 article have been published in European journals ●14 presentations on International Conferences

17 Search for proccesses outside the Standard Model with the prototype of the BOREXINO detector 2005

18 Search for rare processes with CTF 1. The magnetic moment of pp- and 7 Be-neutrinos: μ ν ≤ 5.5x μ B 2. Neutrino radiative decay ν H  ν L +  :  /m ν  4.2 x 10 3 s eV Electron decay mode e  +ν:   4.6 x y 4. Nucleon decays (N  3ν, NN  2ν):   (10 25 – ) y 5. Emission of heavy neutrino in 8 B-decay |U eH | 2 ≤ for m νH = (1÷12) MeV 6. Check of the Pauli principle for (n,p) in 12 C and 16 O nuclei  (10 26 – ) 7.Search for solar hadronic axions emmited in the M1-transition of Li-7 with the Borexino prototype-CTF, 478kev, constant axion-e <10^- 7,~16kev  all limits for 90% c.l.

19 Physical results Search for the solar axion emitted in the M1- transition of 7Li*. The solution to the strong CP problem of QCD proposed by Peccei and Quinn has the consequence that a new pseudoscalar particle, the axion, should be emitted in the nuclear magnetic transitions. One of the main solar reactions e- + 7Be→7Li + ν leads to 7Li* with 0.1 branching. The axion-to- gamma decay rate branching ratio of the M1 transition via axion mass: ωa/ωγ ≈ (ma/1 eV)2(ka/kγ)3

20 Axion search : New upper limit on the hadronic axion mass The expected number of events: N7Li = 9.0*10^25 – number of 7Li nucleus T = 1.1*10^7 s – time of measurement ε = (0.92±0.1) -detection efficiency of the HPGe detector for 478-keV Slim = 1040 – upper limit on the number of counts with E=478 keV for 90% c.l. ma ≤ 16.0 keV (90% c.l.) This result is two times stronger than obtained in the previous works and practically closes the allowed region of axion mass up to M1-transition <14.4 keV.

21 Lower limit, CTF (y) The best existing limit (y) Experiment 12 C ( 16 O) → 12 C( 15 O)+γ 4.2· ·10 27 KamiokaNDE 12 C→ 11 B +p 5.0· ·10 25 ELEGANT V 12 C( 16 O)→ 11 C( 15 O)+n 3.7· ·10 20 Pb 12 C→ 8 Be + α 6.1· C→ 12 N + e - + ν e 7.6· ·10 24 NEMO-2 12 C→ 12 B + e + + ν e 7.7· ·10 24 NEMO arXiv:hep-ph/  European Physics Journal C (2004). Limits on the violation of the Pauli exclusion principle CTF (4.2 t) prototype of BOREXINO (300 t)

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23 Future plan Expected fill operations in 2006 that will bring the Borexino detector to the data taking stage : Data taking with water -3-4 monthes Start filling scintillanting liquid and than Start data taking

24 Title,codes Borexino Название проекта, номер темыБорексино 1017.Годы начала – конца реализации(или продления темы) Планируемые расходы по годам2006 г.2007 г.2008 г.из бюджета ЛФЧ (k$)8-mntc/10 материалы 10/10 10/6 Руководитель проекта __ Займидорога О.А.____________________ (подпись) /2006Исследование спектра солнечных нейтринои осцилляций … (проект БОРЕКСИНО)О.А.Займидорога67352;