SNO Solar Neutrino Results Jos Maneira LIPLisboa Portugal
SNO & Solar Neutrino Results José Maneira (LIP-Lisboa, Portugal) (on behalf of the SNO collaboration, with thanks to Y. Takeuchi from Super. K) Neutrino Oscillation Workshop - NOW 2006 Otranto, September 11, 2006
Outline Introduction Solar Neutrino Results from SNO & Super-K The Super. K and SNO detectors 8 B fluxes Spectral measurements Time variations (Day-Night, Periodicities) Hep solar neutrino limits Prospects for SNO Low energy threshold analysis and Phase III See this afternoon's talks by G. Ranucci and M. Smy on Prospects for Borexino and Phase III of Super. K 2 J. Maneira –NOW 2006 – Otranto - September 11, 2006
the Super. K and SNO detectors
Super. Kamiokande LINAC Electronics hut + e- Water and air purification system Control room Atotsu entrance (for solar neutrinos) Sensitive to e e- =~0. 15× ee- 41. 4 m Timing Ikeno-yama Kamioka-cho, Gifu 3 km 1 km 2 km 39. 3 m Inner Detector 50 kton water fid. vol. 22. 5 kton Mozumi SK Atotsu Outer Detector 1885 of 8 inch PMTs (SK-III) Ring pattern (2700 mwe) Vertex position direction Number of hit PMTs Energy (calibration with LINAC and 16 N) 4 J. Maneira –NOW 2006 – Otranto - September 11, 2006
Super. K data taking phases Feb-1996 Apr-2006 Aug-2002 SK-I (1996 -2001) SK-II (2002 -2005) SK-III (2006 -) • Photo coverage 40% • Photo coverage 19% • Photo coverage 40% 5 J. Maneira –NOW 2006 – Otranto - September 11, 2006
Sudbury Neutrino Observatory • Creighton mine in Sudbury, Canada • 2039 m depth • 6000 mwe Heavy Water : 1000 ton Support structure for 9500 PMT Acrylic Vessel: 12 m diameter Internal H 2 O shielding: 1700 ton External H 2 O shielding: 5300 ton Urylon liner: Radon sealing 6 J. Maneira –NOW 2006 – Otranto - September 11, 2006
Neutrino Reactions in SNO CC e + d → p + e - - e only - Energy spectrum sensitivity - Weak directional sensitivity � 1 -1/3 cos(� ) NC x + d → x + p + n - Same cross section for all 3 flavors -Total flux measurement of 8 B solar neutrinos ES x + e- → x + e - - Higher cross section (6 x) for e, than for and - Low statistics - Strong directional sensitivity 7 J. Maneira –NOW 2006 – Otranto - September 11, 2006
SNO observables PMT Measurements -position -time -charge Reconstructed event -vertex -direction -energy -isotropy 8 J. Maneira –NOW 2006 – Otranto - September 11, 2006
8 B solar neutrinos
8 B flux from SK-II Full SK-II run period (Dec. 2002 ~ Oct. 2005) first 159 days last 631 days Flux x 106 cm-2 s-1 New SK-I result: 2. 35 +/-0. 02(stat. ) +/-0. 08(syst. ) 8. 0 -20 Me. V 7. 0 -20 Me. V Total 791 days Systematic errors are under study. Consistent with SK -I 10 J. Maneira –NOW 2006 – Otranto - September 11, 2006
Signal Extraction in SNO Salt Phase maximum likelihood fit of model PDF’s to data event variables R (radial position) 14(isotropy) cos sun and E(energy) CC-NC separation 14 NC CC ES separation cos sun ES don’t use E ->“energy-unconstrained” -> fit out CC spectrum! 11 J. Maneira –NOW 2006 – Otranto - September 11, 2006
SNO flux results (salt) SNO Collaboration, PRC 72, 055502 (2005) ES 391 Days of Dissolved Salt Data CC SSM x 106 cm-2 s-1 Evidence for flavor change Confirmation of solar model prediction Consistent with Phase I results NC 12 J. Maneira –NOW 2006 – Otranto - September 11, 2006
Energy spectra SNO: CC spectrum from salt phase unconstrained fit No evidence for deviations from standard 8 B shape 13 J. Maneira –NOW 2006 – Otranto - September 11, 2006
Day-Night asymmetry ADN= (Day-Night) (Day+Night)/2 Preliminary for SK-II (systematic errors are under study) ADN (SK-II) = -0. 064 ± 0. 043 (stat. ) ADN (SK-I) = -0. 021 ± 0. 020+0. 013 SNO Combined I+II - 0. 012 14 J. Maneira –NOW 2006 – Otranto - September 11, 2006
Global oscillation analysis of solar and reactor data 2 -flavor analyis Cl + Ga + SK-I daynight spectra + SNO-II LMA-I only allowed region Maximal mixing excluded Solar + Kam. LAND 15 J. Maneira –NOW 2006 – Otranto - September 11, 2006
time modulations
Super. K Periodicity analysis Following claims of periodicity in their data, Super. K published (see hep-ex/0307070) its own periodicity analysis, using a Lomb periodogram. The event arrival times are fit to: (t) = N[1+A cos ( t+ )] For the combined data sets, the biggest peak occurs at a period of 13. 76 days, with a Lomb power=7. 51 Monte Carlo shows that 19% of simulated data sets give a peak at least this large, so no statistical fluctuations are consistent. See also Ranucci, Phys. Rev. D 73: 103003, 2006 17 J. Maneira –NOW 2006 – Otranto - September 11, 2006
SNO Periodicity Analysis SNO has published (see PRD 72 2005, 052010) its own periodicity analysis of the D 2 O and salt data sets, using both a Lomb-Scargle periodogram and an unbinned maximum likelihood fit. The event arrival times are fit to: (t) = N[1+A cos ( t+ )] For the combined data sets, the biggest peak occurs at a period of 2. 4 days, with a significance statistic of S=8. 8 Monte Carlo shows that 35% of simulated data sets give a peak at least this large. No evidence for modulation in any of SNO's data. 18 See also Ranucci & Rovere (hep-ph/0605212) J. Maneira –NOW 2006 – Otranto - September 11, 2006
Observed Time Variations Only evidence for time modulation in SNO and Super. K is due to the Earth orbit eccentricity Super. K-I & II SNO Best-fit eccentricity: = 0. 0143 ± 0. 0086 Actual eccentricity: = 0. 0167 19 J. Maneira –NOW 2006 – Otranto - September 11, 2006
hep solar neutrinos
hep searches Standard Solar Model (7. 97 ± 1. 24) x 103 cm 2 s-1 Possible hep signal lies between 8 B solar neutrinos and atmospheric neutrinos 18. 77 Me. V 21 J. Maneira –NOW 2006 – Otranto - September 11, 2006
Hep limit from SK-I MC hep-ex/0508053 Expected hep signal in 18 -21 Me. V = 1. 06 (Expected 8 B bkg in 18 -21 Me. V =1. 72 ) 4. 9 ± 2. 7 observed Assuming all signals are hep , then flux limit (90%CL)= 7. 9 x SSMBP 2001 7. 3 x 104/cm 2/s Assuming oscillations, total flux limit = 1. 5 x 105/cm 2/s 22 J. Maneira –NOW 2006 – Otranto - September 11, 2006
Hep search in SNO-I 6. 13 Me. V Gamma Rays: 16 N D 2 O Data neutrons 8 B Electrons atmospheric neutrinos DSNB Electrons 19. 8 Me. V Gamma Rays: p. T Michel Electrons hep Electrons 23 J. Maneira –NOW 2006 – Otranto - September 11, 2006
Hep limits from SNO-I We define an optimal signal box based on MC simulations while “hiding” the energy interval 12<Te<35 Me. V hep-ex/0607010 Expect: 3. 1 ± 0. 6 bkg events 0. 99 ± 0. 09 signal events We observe 2 events Total flux limit: hep< 2. 3 x 104 cm-2 s-1 (90% C. L. ) < 2. 9 Solar Models Improves Previous Limits x 6. 5 24 J. Maneira –NOW 2006 – Otranto - September 11, 2006
Limits on Diffuse Supernova Neutrino Background Neutrinos from extragalactic supernovae since the beginning of star formation in the Universe Model predictions of DSNB e flux in range 22. 9 < E < 36. 9 Me. V 0. 19 to 1. 49 cm-2 s-1 Best direct limit 6. 8 x 103 cm 2 -1 s in 25 < E < 50 (Mont Blanc) SNO analysis In 21 < Ee < 35 Me. V 0. 18 background expected No events observed Limit: 70 cm-2 s-1 in 22. 9< E < 36. 9 Me. V 2 orders of magnitude better than previous See F. Fleurot's talks for online burst SN analysis 25 J. Maneira –NOW 2006 – Otranto - September 11, 2006
Prospects for SNO
Precision MSW measurements Push sensitivity for spectral distortions, improve CC/NC In LMA region, tightness of sin 2 12 contour is driven mainly by SNO CC/NC ratio But 13 also depends on CC/NC 27 J. Maneira –NOW 2006 – Otranto - September 11, 2006
Solar neutrino sensitivity to 13 Maltoni et al. , hep-ph/0309130 90, 95, 99% CL Chooz m 232 from SK atmospheric 28 J. Maneira –NOW 2006 – Otranto - September 11, 2006
Low energy threshold analysis New combined analysis of Phase I and II data Better energy estimation, better resolution Several other improvements to MC and cuts Reduction of background tails Low threshold: 4 Me. V looks good Lower systematics Simulated data Preliminary!! 29 J. Maneira –NOW 2006 – Otranto - September 11, 2006
Improving resolution by accounting channel-by-channel variations 30 J. Maneira –NOW 2006 – Otranto - September 11, 2006
New energy estimators Comparison between 16 N calibration source data and MC New “Total Light” Energy Estimator Improved “Prompt Light” Energy Estimator RMS Spread in Previous Analyses … = 0. 7 31 J. Maneira –NOW 2006 – Otranto - September 11, 2006
SNO Phase III
3 neutron detection methods Phase I (D 2 O) Phase II (salt) Phase III(3 He) Summer 04 -Dec. 06 Nov. 99 - May 01 July 01 - Sep. 03 n captures on 2 H(n, )3 H = 0. 0005 b Observe 6. 25 Me. V PMT array readout 2 t Na. Cl. n captures on 35 Cl(n, )36 Cl = 44 b Observe multiple ’s PMT array readout 40 proportional counters 3 He(n, p)3 H = 5330 b independent readout Enhanced NC Event by Event NC Good CC 2 H+n 35 Cl+n 5 cm 8. 6 Me. V 6. 25 Me. V 3 H Initial Results n 3 H 3 He 36 Cl Recent Results p n + 3 He p + 3 H 33 Now Running J. Maneira –NOW 2006 – Otranto - September 11, 2006
Neutral Current Detectors 3 He + n →p + 3 H + 0. 764 Me. V The Neutral Current Detectors (NCDs) are 3 He proportional counters, that detect the p and/or 3 H from neutron capture 5 cm wide and ~10 m long, attached to the bottom of the acrylic vessel 40 are installed, 4 of which have 4 He instead of 3 He, for background control Measure NC with different systematics Break NC, CC correlations 34 J. Maneira –NOW 2006 – Otranto - September 11, 2006
4 3 He He 35 J. Maneira –NOW 2006 – Otranto - September 11, 2006
Working around the NCDs in the Optical Calibration PMT occupancy map with Laser source in the center of the detector NCD shadows 36 J. Maneira –NOW 2006 – Otranto - September 11, 2006
Preliminary Blind Analysis of NCD energy spectrum Next : Adding Pulse Shape Discrimination 37 J. Maneira –NOW 2006 – Otranto - September 11, 2006
Backgrounds Signal More calibrations in phase III Neutron perpendicular to anode All the optics, 16 N, point neutron and background sources from previous phases, plus: Distributed neutron and background sources (Rn, 24 Na) Surface alpha Embedded alpha Alpha beam tests Neutron parallel to anode HV Discharge
Summary Update results on fluxes, energy spectra, D/N asymmetries Time variations and Periodicity analyses Super. K and SNO analyses indicate no evidence for periodicities beyond the expected due to Earth orbit eccentricity New search for hep solar neutrinos From SNO pure D 2 O and salt phases, SK-I and new results from SK-II hep < 2. 9 SSM, 6. 5 x lower than previous limits Future Prospects Super. K-III now taking data -> see M. Smy's talk SNO phase III with Neutral Current Detectors Low Energy Threshold Analysis of existing data As well as Borexino and Kam. LAND for 7 Be neutrinos 39 J. Maneira –NOW 2006 – Otranto - September 11, 2006
40 J. Maneira –NOW 2006 – Otranto - September 11, 2006
The New SNOLAB New Excavation To Date SNO
Cosmic ray muons vs. depth
SNO+ • After heavy water is removed from SNO in 2007: • SNO plus liquid scintillator physics program – pep and CNO low energy solar neutrinos (11 C: 20 x < Gran Sasso) • SSM pep flux: uncertainty ± 1. 5% allows precision test. • Comparison with the photon luminosity. • Tests the neutrino-matter interaction, sensitive to new physics. – non-standard interactions, mass-varying neutrinos, CPT violation, large 13, sterile neutrino admixture…. – geo-neutrinos – 240 km baseline reactor oscillation confirmation – supernova neutrinos – double beta decay (150 Nd) ? 43 J. Maneira –NOW 2006 – Otranto - September 11, 2006
Survival Probability Rise stat + syst + SSM errors estimated SSM pep flux: uncertainty ± 1. 5% m 2 = 8. 0 × 10− 5 e. V 2 tan 2 = 0. 45 known source → precision test Improves precision on 12 Sensitive to new physics: • non-standard interactions • solar density perturbations • mass-varying neutrinos • CPT violation • large 13 • sterile neutrino admixture SNO CC/NC pep Studying the rise confirms MSW or perhaps shows us new physics 44 J. Maneira –NOW 2006 – Otranto - September 11, 2006
Event Rates (oscillated) 7 Be resolution with 450 photoelectrons/Me. V solar neutrinos 3600 pep/year/kton >0. 8 Me. V using BS 05(OP) and best-fit LMA 2300 CNO/year/kton >0. 8 Me. V 45 J. Maneira –NOW 2006 – Otranto - September 11, 2006
Cosmogenic 11 C background 11 these plots from the Kam. LAND proposal muon rate in Kam. LAND: 26, 000 d− 1 compared with SNO: 70 d− 1 46 J. Maneira –NOW 2006 – Otranto - September 11, 2006
Geo-Neutrino signal terrestrial antineutrino event rates: • Borexino: 10 events per year (280 tons of C 9 H 12) / 29 events reactor • Kam. LAND: 29 events per year (1000 tons CH 2) / 480 events reactor • SNO+: 64 events per year (1000 tons CH 2) / 87 events reactor based on Rothschild, Chen, Calaprice Geophys. Res. Lett. 25, 1083 (1998) geo- in Kam. LAND SNO+ geo-neutrinos and reactor background Kam. LAND geo-neutrino detection…July 28, 2005 in Natur 47 J. Maneira –NOW 2006 – Otranto - September 11, 2006
SNO++ (Nd Double Beta Decay) 0 : 1057 events per year with 1% natural Nd-loaded liquid scintillator in SNO++. Simulation assuming light output similar to Kamland. Very preliminary simulation: one year of data m = 0. 15 e. V 48 J. Maneira –NOW 2006 – Otranto - September 11, 2006
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