Borexino: real-time detection of low energy solar neutrinos

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1 Borexino: real-time detection of low energy solar neutrinos Andrea Pocar - Stanford University SSI SLAC, August 12, 2008 A. Pocar - SSI SLAC, August 12,

2 outline - solar neutrinos and neutrino oscillations - Borexino: physics goals and design - background reduction days of Borexino data - future A. Pocar - SSI SLAC, August 12,

3 Fundamental fusion reaction: 4p 4 He + 2e + + 2ν e MeV neutrino production in the sun pp chain p + p d + e + + ν e (99.77%) p + e - + p d + ν e (0.23%) ν pp ν pep ~3% of the energy is carried away by kinetic energy of neutrinos 85% p + d 3 He + γ 10-5 % ν hep 3He + 3 He α + 2p 15% 3He + p 4 He + e + + ν e pp I 99.9% 3He + α 7 Be + γ 0.1% 7Be + e - 7 Li + ν e 7Be + p 8 (p, B + γ 4 He) ν Be7 7Li + p 2α 8B 2α + e + + ν e (p,γ) pp II pp III ν B8 (p, 4 He) A. Pocar - SSI SLAC, August 12, C 15N CNO cycle (p,γ) e +,ν e ν O15 (p,γ) 13N 15O e +,ν e ν N13 (p,γ) e +,ν e 13C 14N 16O 17F 17O ν F17 (p,γ)

4 solar neutrino spectrum water ~2/5 gallium ~1/2 chlorine ~1/3 BPS % Borexino 10 ± 5 A. Pocar - SSI SLAC, August 12,

the solar neutrino problem - All experiments prior to SNO have observed fewer (1/3 to 1/2) solar neutrinos than expected from the standard solar model (SSM) and the theory of weak interactions -

5 the solar neutrino problem - All experiments prior to SNO have observed fewer (1/3 to 1/2) solar neutrinos than expected from the standard solar model (SSM) and the theory of weak interactions - Furthermore, the data vs theory deficit was inconsistent between experiments Clues: - different thresholds - Cl/Ga experiments only sensitive to electron ν s - water Čerenkov detectors are sensitive to all ν flavours (with different cross sections) - SNO measured charged and neutral currents: ν x + d ν x + p + n ν e + d e - + p + p A. Pocar - SSI SLAC, August 12, SNU (Solar Neutrino Unit) = captures/atom/second 5

charged current neutral current elastic scattering neutrino oscillations SNO measured: - a reduced solar ν e flux (~1/3) - a positive solar ν μ,τ flux - total solar neutrino flux consistent with

6 charged current neutral current elastic scattering neutrino oscillations SNO measured: - a reduced solar ν e flux (~1/3) - a positive solar ν μ,τ flux - total solar neutrino flux consistent with expectations from the SSM [Ahmad et al., Phys. Rev. Lett. 89 (2002) ] - the sun only produces electron neutrinos which therefore oscillate before they are detected on earth - oscillations imply that weak and energy (mass) eigenstates are different, which in turn requires neutrinos (at least one) to be massive: - solar experiments + KamLAND yield (LMA-MSW): Δm 2 12 ~ ev 2 tan 2 θ12 ~ 0.4 A. Pocar - SSI SLAC, August 12,

7 MSW effect - νe s interact with electrons via both neutral and charged currents; their propagation is affected by matter differently than for ν μτ s νe and νμτ has a different index of refraction (Wolfenstein, 1978) - resonant amplification of oscillations is possible due to enhanced forward scattering of νe (Mikheyev & Smirnov, 1985) - solar neutrinos are affected by the dense solar matter, an energy-dependent effect P ee Bahcall & Peña-Garay - Low energy (pp) neutrinos are barely affected (Pee ~ 56%) - High energy ( 8 B) neutrinos are most affected (P ee ~ 32%) (small effect for propagation through the earth, day/night) - no direct data at intermediate energy 0.0!!cos(2" 12 ) E A. Pocar - SSI SLAC, August 12,

8 before Borexino Solar Neutrino Survival Probability P ee Be LMA Prediction Be LMA-NSI Prediction MaVaN Prediction SNO Data Ga/Cl Data Before Borexino 0.6 Barger et al., PRL 95, (2005) A. Pocar - SSI SLAC, August 12, 2008 Friedland et al., PLB 594, 347 (2004) 1 10 E [MeV] 8

9 Borexino: main science goals - experiment conceived in the mid 90 s, before the discovery of atmospheric neutrino oscillations in 1998 by Super/Kamiokande - data from only 4 solar neutrino experiments (Chlorine, Gallex, Sage, Kamiokande) left no space for the 7 Be neutrinos without oscillations - Make the first ever observations of sub-mev neutrinos in real time, especially for 7 Be solar neutrinos, testing the Standard Solar Model and the MSW-LMA solution of the Solar Neutrino Problem (and check their solar origin by measuring the expected 7% seasonal variation of the signal due to the Earth s orbital eccentricity) - Provide a strong constraint on the 7 Be rate, at or below 5% (provide an essential input to check the balance between photon luminosity and neutrino luminosity of the Sun (requires 7 Be flux measured at 5% and pp flux at 1%) - Explore possible traces of non-standard neutrino-matter interactions or presence of mass varying neutrinos. A. Pocar - SSI SLAC, August 12,

10 additional possible first time measurements - CNO neutrinos (direct indication of metallicity in the Sun s core) - pep neutrinos (indirect constraint on pp neutrino flux) - low energy (2-5 MeV) 8B neutrinos - tail end of pp neutrinos spectrum? A. Pocar - SSI SLAC, August 12,

11 Detection technique Water Čerenkov detectors have a lower energy threshold of 5-6 MeV Neutrino electron scattering on electrons in a large target of organic liquid scintillator: - measure the energy of recoiling electrons: very low energy threshold - high light yield (good energy resolution) - good position reconstruction (photon time of flight) - possible to re-purify the scintillator (needed because ν, β, γ events look alike) - separate high and low ionization events (α/β discrimination) - no directional information 14C background 7Be: no oscillation 7Be: LMA prediction 7Be: if P ee = 0 finite energy resolution mono-energetic 862 kev 7 Be neutrinos produce an almost flat spectrum with a 667 kev endpoint A. Pocar - SSI SLAC, August 12,

12 Borexino challenges The experiment s main background is natural radioactivity Natural radioactivity: - 14 C, present in organic scintillator (β, t1/2=5730 y, Q=156 kev) - long-lived primordial radioactivity: 232 Th, 235 U, 238 U, 40 K (α, β, γ) - radon and radon daughters on surfaces ( 222 Rn, 210 Pb, 210 Po) - 39 Ar, 85 Kr ((β, t1/2=270/10 y, Q=565/687 kev) - need to use the cleanest materials available - minimize air exposure: 222 Rn (tens Bq/m 3 ), 85 Kr (1 Bq/m 3 ), 39 Ar (16 mbq/m 3 ) Muons and muon induced radioactivity - need to be deep underground - 11 C, 10 C, 7 Be and others [C. Arpesella et al., Astropart. Phys. 18 (2002) 1] A. Pocar - SSI SLAC, August 12,

13 Gran Sasso Gran Sasso (LNGS) 3500 m.w.e. shielding muon flux ~ 1/h/m 2 A. Pocar - SSI SLAC, August 12,

14 ν Graded shielding design ν n e γ Rn A. Pocar - SSI SLAC, August 12,

15 Event generation ν-e scattering + 2 ionization + UV light emission e scintillation light detection with 2200 PMTs solvent (PC) + fluor (PPO, 1,5 g/l) energy and position of each event with photon arrival time and collected charge A. Pocar - SSI SLAC, August 12,

Scintillator purification - petroleum derivative with 12 C/ 14 C ~ 10-18 ( 10 6 lower than surface carbon) - fast shipment underground to minimize 7 Be activation (EC, t 1/2 =53 d, 478 kev γ-ray) -

16 Scintillator purification - petroleum derivative with 12 C/ 14 C ~ ( 10 6 lower than surface carbon) - fast shipment underground to minimize 7 Be activation (EC, t 1/2 =53 d, 478 kev γ-ray) - 6-stage distillation + low Ar/Kr N2 gas stripping for PC solvent - separate filtration, distillation + stripping for concentrated PPO fluor solution - all plants, tanks and lines precision cleaned (detergent + acid etching) A. Pocar - SSI SLAC, August 12,

3) x 10-16 g/g 232Th = (4.4 ± 1.5) x 10-16 g/g 14C/ 12 C = (1.94 ± 0.

17 Alimonti et al., Nucl. Instr. Meth A 406 (1998) 411 Counting Test Facility Measurement of scintillator contaminations proving the feasibility of Borexino (1995): 238U = (3.5 ± 1.3) x g/g 232Th = (4.4 ± 1.5) x g/g 14C/ 12 C = (1.94 ± 0.09) x note: Th and U contamination dominated by external background campaigns (1995, 2001, ): - testing facility for scintillator ( 14 C) - materials employed in Borexino (nylon, ropes) - scintillator purification strategies - limits on rare phenomena (e-decay, magnetic moment,...) A. Pocar - SSI SLAC, August 12,

the KamLAND example In KamLAND, where little specific measures were taken to maximize radio-purity at low energy, the background was 5 orders of

18 the KamLAND example In KamLAND, where little specific measures were taken to maximize radio-purity at low energy, the background was 5 orders of magnitude above the 7 Be expected signal [Kishimoto for the KamLAND collaboration, TAUP 2007, Sendai, Japan] A. Pocar - SSI SLAC, August 12,

Nylon vessels - nylon pellets with 10-12 Th, U concentration in weight (ppt) [C. Arpesella et al., Astropart. Phys. 18, 1 (2002)] - clean extrusion and post-extrusion surface cleaning to level 25 Mil.

, NIM A 498, 240 (2003)] - nylon vessels (inner for scintillator containment, outer Rn barrier) made in a class 100 clean room - surfaces kept covered as much as possible during assembly, shipping

19 Nylon vessels - nylon pellets with Th, U concentration in weight (ppt) [C. Arpesella et al., Astropart. Phys. 18, 1 (2002)] - clean extrusion and post-extrusion surface cleaning to level 25 Mil. Std. 1246C ( 226 Ra contamination of final film < 21 μbq/kg) [M. Wójcik et al., NIM A 498, 240 (2003)] - nylon vessels (inner for scintillator containment, outer Rn barrier) made in a class 100 clean room - surfaces kept covered as much as possible during assembly, shipping and installation - each vessels assembled as a self-covering stack and assembled into a nested set - radon-scrubbed clean room make up air, via a room temperature vacuum swing adsorption (VSA) on activated charcoal device (first of its kind) - clean room air humidified with aged water - detector turned into a class 10,000 clean room [J. Benziger et al., NIM A 582, 509 (2007)] A. Pocar - SSI SLAC, August 12,

20 Nylon vessel installation A. Pocar - SSI SLAC, August 12,

21 Borexino gas purging Nylon vessel inflation: - low Rn synthetic air - low Rn N2 - low Ar, Kr, Rn N2 A. Pocar - SSI SLAC, August 12,

22 A. Pocar - SSI SLAC, August 12,

23 Borexino water filling interesting optics: total internal reflection! Detector filling with ultra-pure water 12 muon events from CNGS neutrino beam observed 10/2006 (the detector ~80% full) A. Pocar - SSI SLAC, August 12,

24 Borexino water filling Water filling: complete plant commissioning + rinse surfaces from Rn daughter A. Pocar - SSI SLAC, August 12,

25 Borexino scintillator filling Scintillator inserted from the top: track its purity with fully shielded detector A. Pocar - SSI SLAC, August 12,

Borexino scintillator filling Detector full, May 15

26 Borexino scintillator filling Detector full, May A. Pocar - SSI SLAC, August 12,

27 First data Raw energy spectrum (no cuts) days of detector live time tons of scintillator Main features: 14 C: used for energy calibration and mass normalization 210 Po: monitor of detector stability continuous γ spectrum events/(days x 100 tons x 5 photoelectrons) 14 C 210 Po raw data predicted 7 Be neutrino signal (MSW-LMA oscillations) background from external gamma rays Borexino data Light yield: ~ 500 photoelectrons every 1 MeV of energy release (for electrons) [~ 10% less for γ rays, much less (factor of ~ 10) for α particles because of quenching where the ionization density in the scintillator is higher] A. Pocar - SSI SLAC, August 12,

28 Fiducial volume Select only the innermost 100 tons (within a 3 meter radius) of scintillator to improve S/N, taking advantage of the increased shielding layer - events selected according to their reconstructed position - eliminates most external γ-ray background - also eliminates signals from radioactivity on the inner vessel and radon emanated from its surface A. Pocar - SSI SLAC, August 12,

Fiducial volume definition: Selecting the fiducial volume - position reconstruction algorithms not completely calibrated and have some systematic radial biases - we select the spherical volume

9% of the total number of 14 C-like events in the 60-80 photoelectron range z vs R c scatter plot Possible problems: - 14 C may not be evenly distributed in the detector if the scintillator came from

29 Fiducial volume definition: Selecting the fiducial volume - position reconstruction algorithms not completely calibrated and have some systematic radial biases - we select the spherical volume centered on the detector center which produces (100 tons / 278 tons) = 35.9% of the total number of 14 C-like events in the photoelectron range z vs R c scatter plot Possible problems: - 14 C may not be evenly distributed in the detector if the scintillator came from different batches and mixing is not complete - position reconstruction may have different systematic biases (scaling factors) at 14 C and 7 Be neutrino energies - possible light loss for events farther from the center of the detector!"#"$%&"'s$n).$/&%#$!&$,#'&<#$>)'').$9,&'$+-$#%/:0m. $ 9,&'$RLB.$!")!$M#%#!,)!#$!"#$=099#, The mass normalization is the largest source of systematic error - will perform source calibrations in the future R! x " y!! A. Pocar - SSI SLAC, August 12, c

30 Delayed coincidences Certain isotopes can be readily identified as they produce coincident decays in rapid succession at the same location in the detector β+γ α 214 Bi 214 Po 210 Pb (τ = 237 μs, 238 U chain, 222 Rn daughter) 3.3 MeV 7.7 MeV β+γ α 212 Bi 212 Po 208 Pb (τ = 431 ns, BR = 64%, 232 Th chain) 3.3 MeV 8.8 MeV β γ 85 Kr 85m Rb 85 Rb (τ = 1.46 μs, BR = 0.43%) 687 kev 514 kev False positives are extremely unlikely as the coincidence time is much smaller than the time separation of random events of similar energies (this is true even without applying tight constraints on the position of the events in the pair) A. Pocar - SSI SLAC, August 12,

31 Radon daughters subtraction Bi/ 214 Po decays can be easily removed from the data set - their rate in the detector is the same as that of all isotopes which constitute the rapid succession of α and β decays separating 222 Rn and 210 Pb: 222 Rn 218 Po 214 Pb 214 Bi 214 Po 210 Pb ( 210 Bi 210 Po 206 Pb) τ = 5.5 d 4.4 m 39 m 28 m 237 μs 22.3 y - Excluding events preceding a BiPo-214 coincidence by 3 hours or less, and within 1 m of the BiPo-214 events spatial locations, lets us eliminate > 90% of each of these five species from the data, with little sample loss - This is particularly useful for the β-emitting isotope 214 Pb, whose spectrum has a broad peak near the 7 Be neutrino shoulder energy. A. Pocar - SSI SLAC, August 12,

32 Data after fiducial volume and radon cuts days tons exposure (note: events with z > 1.8 m were also excluded due to Rn contamination during detector top-off operations) Main features: 14 C: unaltered 210 Po: - sharper peak - same amplitude gamma background substantially reduced 11 C: muon produced positron emitter events/(days x 100 tons x 5 photoelectrons) Energy Raw spectrum energy spectrum (fid. vol. (no + Rn cuts) cuts) 14 C 210 Po 7 Be raw data data after fid. vol. + Rn cuts predicted 7 Be neutrino signal (MSW-LMA oscillations) background from external gamma rays 7 Be Compton shoulder visible after these very simply cuts! background from external gamma rays 11 C Borexino data A. Pocar - SSI SLAC, August 12,

33 210 Po background Po (τ = 200 d) activity is ~ 60 events/d/ton (> 100 the predicted 7 Be solar neutrino rate!) Po is out of equilibrium with 210 Pb and 210 Bi, since the decay rate of the latter is >100 times smaller (β and γ decays of 210 Pb are < 100 kev and buried under 14 C) events/(days x 100 tons x 5 photoelectrons) 210 Po data after fid. vol. + Rn cuts fitted 210 Po α peak (gaussian) 210 Bi β spectrum if it were in equilibrium with 210 Po > 2 orders of magnitude Borexino data 210 Po has a very complicated chemistry, certainly different than that of 210 Pb: - confirms tests performed with the latest CTF runs - also seen during recent KamLAND scintillator purification - contamination and wash-off patterns studied in the lab - needs dedicated purification strategy A. Pocar - SSI SLAC, August 12, 2008 [Kishimoto, TAUP 2007, Sendai, Japan] 33

34 α/β discrimination α particles leave a more densely ionized track than electrons and photons (α s are ~ 8000 times more massive and travel much more slowly than electrons of the same kinetic energy, according to T = (γ - 1) mc 2 ) As a consequence, typical pulse shapes of α and β events producing the same amount of scintillation are different Two effects: 1) α particles produce less scintillation light per unit energy than electrons by a factor ~ 10, meaning that α decays (4-8 MeV) appear to have β-equivalent energies < 1 MeV 214Bi β average pulse shape 214Po α average pulse shape 2) the relative amplitude of the slow component of the scintillator pulse is greater for α particles [H. Back et al., Nucl. Instr. Meth. A 584 (2008) 98] A. Pocar - SSI SLAC, August 12,

35 Data after α subtraction raw data data after fiducial volume + Rn cuts data after α subtraction predicted 7 Be neutrino signal (MSW-LMA oscillations) Borexino data β and γ spectra unaffected by α subtraction A. Pocar - SSI SLAC, August 12,

36 7 Be solar neutrino flux Fit result for 7 Be ν: 47 ± 7 stat ± 12 sys events/(day x 100 tons) Predicted (SSM, no oscillations): 75 ± 4 theor events/(day x 100 tons) Borexino data Predicted (with LMA vacuum oscillations): 49 ± 4 theor events/(day x 100 tons) [Phys. Lett. B 658 (2008) 101, arxiv: ] A. Pocar - SSI SLAC, August 12,

37 Counts/(10 kev x day x 100 tons) days of data [arxiv: , submitted to Phys. Rev. Lett.] Fit:! 2 /NDF = 185/174 7 Be: 49±3 cpd/100 tons 210 Bi+CNO: 23±2 cpd/100 tons 85 Kr: 25±3 cpd/100 tons 11 C: 25±1 cpd/100 tons 14 C 10 C Borexino data Energy [kev] A. Pocar - SSI SLAC, August 12,

38 192 days of data (second, independent analysis) [arxiv: , submitted to Phys. Rev. Lett.] A. Pocar - SSI SLAC, August 12, 2008

39 Fiducial Volume definition: uniform background sources( 14 C, 222 Rn, capture of cosmogenic n), 220 Rn decay emitted by nylon, diffuser balls on the IV surface,laser activated. 192 days of data Expected interaction rate in absence of oscillations: 75±4 cpd/100 tons for LMA-MSW oscillations: 48±4 cpd/100 tons A. Pocar - SSI SLAC, August 12, 2008 Estimated 1σ Systematic Uncertainties * [%] Total Scintillator Mass 0.2 Fiducial Mass Ratio 6.0 Live Time 0.1 Detector Resp. Function 6.0 Cuts Efficiency 0.3 Total 8.5 * Prior to Calibration 7 Be Rate: 49±3stat±4syst cpd/100 tons

40 49 ± 3stat ± 4syst cpd/100 tons (862 kev 7 Be solar ν) Φ( 7 Βe) = (5.12 ±0.51) x 10 9 cm 2 s -1 SSM: high metallicity: (5.08±0.56) x10 9 cm -2 s -1 low metallicity: (4.55 ±0.5) x10 9 cm -2 s -1 after Borexino A. Pocar - SSI SLAC, August 12, 2008

41 !"#$%&%' ()'*+$,-"./01210&!"! 23%&'!"#$%"&'(%) *%# +,+ B8C9$,/, =D<,/, EC!"# $%&'()*+,)&(-&(,.(/ 010!"#$ %&' ()* %&' +# 456 7!"&(,.(* 010,"#$-./012"3$ &'5%/*!"#$%&'! "4 78 "49 56 $ "4 56 "$&(&)*+$$$$$$,-./0$$123 /#@$%&' 4/0$%&' ":$/;0!$#+$$$< =5>$$?;0@A 1B,!4* %&'CD?9EB)>'F G.'65"'&)H/)!B+* 64)'F#&'65')4I) 1B, J#0#6#K#%$$/)2,)5L&LK!"#$%&'$("#%)* +,)-.$/0)1,,2 A. Pocar - SSI SLAC, August 12, 2008 measured backgrounds 3#4%55"#64)7%6.55#)* 89:9;9:9)<'=9)&#)>#$%64

What next: pep and CNO solar neutrinos Scientifically desirable: - pep rate is closely connected with pp rate (low energy, mostly obscured by 14 C), first fusion step in the sun - CNO flux has large

smaller than 7 Be, which obscures most of their spectrum - pep Compton shoulder falls below the 11 C positron spectrum - 210 Bi, 40 K and 208 Tl ( 232 Th) backgrounds CNO, pep 11 C event-by-event

42 What next: pep and CNO solar neutrinos Scientifically desirable: - pep rate is closely connected with pp rate (low energy, mostly obscured by 14 C), first fusion step in the sun - CNO flux has large theoretical uncertainty (30%) depending on unknown factors of the solar chemical composition (metallicity of the mantle) Hard to detect: - the expected pep and CNO solar neutrino rates are 5-10 times smaller than 7 Be, which obscures most of their spectrum - pep Compton shoulder falls below the 11 C positron spectrum Bi, 40 K and 208 Tl ( 232 Th) backgrounds CNO, pep 11 C event-by-event subtraction: - when a muon produces a 11 C, simulations suggest that a free muon is also emitted ~95% of the times - muon, neutron capture (~200 μs) and 11 C decay (29 m) can be correlated in space and time with manageable dead time [C. Galbiati et al., Phys. Rev. C 71 (2005) ] A. Pocar - SSI SLAC, August 12,

43 μ Track n Capture 11 C #$ %&?''( %%?$6I# %% )I' I I! ' 6)5%(A.@' *"+&,& >'JK A. Pocar - SSI SLAC, August 12, 2008

44 What next: geo-neutrinos,... Antineutrinos are emitted by natural radioactivity in the earth s crust (β decays of 40 K and 238 U, 232 Th daughters) and by decaying fission products in nuclear reactors; some these can be detected by inverse β decay of protons (E > 1.8 MeV): νe + p n + e + One detects the e + annihilation followed by a 2.2 MeV γ from neutron capture on H Evidence of their detection published by KamLAND [Nature, 436 (2005) 499] ~10 geo-neutrino events/year are expected in Borexino, 280 tons (~10 from reactors) [Rothschild, Chen and Calaprice, Geophys. Res. Lett. 25 (1998) 1083; arxiv:nucl-ex/ ] What else? - 8 B solar neutrinos (matter- to vacuum-dominated oscillations) - pp solar neutrinos (possible shoulder above 14 C) - neutrinos and antineutrinos from supernovæ in our galaxy - neutrino magnetic moment with 1 MCi 51 Cr (10-11 μb sensitivity) A. Pocar - SSI SLAC, August 12,

45 A. Pocar - SSI SLAC, August 12,

46 Summary - Borexino has made the first real time measurement of 7 Be solar neutrinos and the observed flux, with 192 days of live time, is consistent with the MSW-LMA neutrino oscillation solution (and incompatible with no oscillations) - Borexino is the most sensitive solar neutrino running experiment, thanks to having achieved unprecedented low levels of background (first real-time neutrino detection below the threshold of natural radioactivity, the result of a decade-long, pioneering effort in low background physics) - Borexino is scheduled to run for many years with a challenging scientific agenda; it will attempt to measure the entire solar neutrino spectrum, terrestrial and supernova neutrinos, and possibly discover non-standard neutrino properties A. Pocar - SSI SLAC, August 12,

47 the Borexino collaboration New results on solar neutrino fluxes from 192 days of Borexino data C. Arpesella, 1, 2, a H.O. Back, 3, b M. Balata, 1 G. Bellini, 2 J. Benziger, 4 S. Bonetti, 2 A. Brigatti, 2 B. Caccianiga, 2 L. Cadonati, 5, 6 F. Calaprice, 6 C. Carraro, 7 G. Cecchet, 8 A. Chavarria, 6 M. Chen, 9, 6 F. Dalnoki-Veress, 6 D. D Angelo, 2 A. de Bari, 8 A. de Bellefon, 10 H. de Kerret, 10 A. Derbin, 11 M. Deutsch, 12, a A. di Credico, 1 G. di Pietro, 1, 2 R. Eisenstein, 6 F. Elisei, 13 A. Etenko, 14 R. Fernholz, 6 K. Fomenko, 15 R. Ford, 6, 1, c D. Franco, 2 B. Freudiger, 16, a C. Galbiati, 6, 2 F. Gatti, 7 S. Gazzana, 1 M. Giammarchi, 2 D. Giugni, 2 M. Goeger-Neff, 17 T. Goldbrunner, 17, d A. Goretti, 6, 2, 1 C. Grieb, 3, e C. Hagner, 17, f W. Hampel, 16 E. Harding, 6, g S. Hardy, 3 F.X. Hartman, 16 T. Hertrich, 17 G. Heusser, 16 Aldo Ianni, 1, 6 Andrea Ianni, 6 M. Joyce, 3 J. Kiko, 16 T. Kirsten, 16 V. Kobychev, 18 G. Korga, 1 G. Korschinek, 17 D. Kryn, 10 V. Lagomarsino, 7 P. Lamarche, 6, 1 M. Laubenstein, 1 C. Lendvai, 17 M. Leung, 6 T. Lewke, 17 E. Litvinovich, 14 B. Loer, 6 P. Lombardi, 2 L. Ludhova, 2 I. Machulin, 14 S. Malvezzi, 2 S. Manecki, 3 J. Maneira, 9, 2, h W. Maneschg, 16 I. Manno, 19, 2 D. Manuzio, 7, i G. Manuzio, 7 A. Martemianov, 14, a F. Masetti, 13 U. Mazzucato, 13 K. McCarty, 6 D. McKinsey, 6, j Q. Meindl, 17 E. Meroni, 2 L. Miramonti, 2 M. Misiaszek, 20, 1 D. Montanari, 1, 6 M.E. Monzani, 1, 2 V. Muratova, 11 P. Musico, 7 H. Neder, 16 A. Nelson, 6 L. Niedermeier, 17 L. Oberauer, 17 M. Obolensky, 10 M. Orsini, 1 F. Ortica, 13 M. Pallavicini, 7 L. Papp, 1 S. Parmeggiano, 2 L. Perasso, 2 A. Pocar, 6, k R.S. Raghavan, 3 G. Ranucci, 2 W. Rau, 16, 9 A. Razeto, 1 7, 16 E. Resconi, P. Risso, 7 A. Romani, 13 D. Rountree, 3 A. Sabelnikov, 14 R. Saldanha, 6 C. Salvo, 7 D. Schimizzi, 4 S. Schönert, 16 T. Shutt, 6, l H. Simgen, 16 M. Skorokhvatov, 14 O. Smirnov, 15 A. Sonnenschein, 6, m A. Sotnikov, 15 S. Sukhotin, 14 Y. Suvorov, 2, 14 R. Tartaglia, 1 G. Testera, 7 D. Vignaud, 10 S. Vitale, 7, a R.B. Vogelaar, 3 F. von Feilitzsch, 17 R. von Hentig, 17, e T. von Hentig, 17, e M. Wojcik, 20 M. Wurm, 17 O. Zaimidoroga, 15 S. Zavatarelli, 7 and G. Zuzel 16 (Borexino Collaboration) 1 INFN Laboratori Nazionali del Gran Sasso, SS 17 bis Km , Assergi (AQ), Italy 2 Dipartimento di Fisica, Università degli Studi e INFN, Milano, Italy 3 Physics Department, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA 4 Chemical Engineering Department, Princeton University, Princeton, NJ 08544, USA 5 Physics Department, University of Massachusetts, Amherst, AM 01003, USA 6 Physics Department, Princeton University, Princeton, NJ 08544, USA 7 Dipartimento di Fisica, Università e INFN, Genova 16146, Italy 8 INFN, Pavia 27100, Italy 9 Physics Department, Queen s University, Kingston ON K7L 3N6, Canada 10 Laboratoire AstroParticule et Cosmologie, Paris cedex 13, France 11 St. Petersburg Nuclear Physics Institute, Gatchina, Russia 12 Physics Department, Massachusetts Institute of Technology, Cambridge, MA, USA 13 Dipartimento di Chimica, Università e INFN, Perugia, Italy 14 RRC Kurchatov Institute, Moscow, Russia 15 Joint Institute for Nuclear Research, Dubna, Russia 16 Max-Planck-Institut für Kernphysik, Heidelberg, Germany 17 Physik Department, Technische Universität Muenchen, Garching, Germany 18 Kiev Institute for Nuclear Research, Kiev, Ukraine 19 KFKI-RMKI, 1121 Budapest, Hungary 20 M. Smoluchowski Institute of Physics, Jagiellonian University, Krakow, Poland (Dated: June 9, 2008) A. Pocar - SSI SLAC, August 12,

Precision measurement of the Be solar neutrino interaction rate in Borexino

University of Massachusetts Amherst From the SelectedWorks of Laura Cadonati August 4, 011 Precision measurement of the Be solar neutrino interaction rate in Borexino Borexino Collaboration, Borexino Collaboration