192 days of Borexino - slac.stanford.edu · Cristiano Galbiati on behalf of Borexino Collaboration Tuesday, May 27, 2008 2. Solar Neutrinos Spectrum Tuesday, May 27, 2008 3. Solar

192 days of BorexinoNeutrino 2008

Christchurch, New ZelandMay 26, 2008

Cristiano Galbiation behalf of

Borexino Collaboration

2Tuesday, May 27, 2008

Solar Neutrinos Spectrum


Solar Neutrinos SpectrumSNO,

SuperK



SuperKCl Experiment



SuperKCl ExperimentGa Experiment



SuperKCl Experiment

Borexino

Ga Experiment


For high energy 8B neutrinos - object of observation by SNO and SuperKamiokaNDE - matter dominated oscillations in the high density of electrons Ne in sun’s core

For low energy neutrinos, flavor change dominated by vacuum oscillations.

Regime transition expected between 1-2 MeV

Fundamental prediction of MSW-LMA theoryExploring the vacuum-matter transition:

untested feature of MSW-LMA solutionpossibly sensitive to new physics

pep and 7Be neutrinos good sources to study the transition!

Bahcall &Peña-Garay

Resonant Oscillations in Matter:the MSW effect

1! 12

sin2 2!12

sin2 !12

!!!m2

124E cos 2!12 +

"2GF Ne

!m212

4E sin 2!12!m2

124E sin 2!12

!m212

4E cos 2!12

"

Pee

E0.0

0.2

0.4

0.6

0.8

1.0

!!cos(2"12)

! =23/2GF NeE

!m2= 0.22

!E

1 MeV

" !" · Z/A

100 g cm!3

" !7! 10!5 ev2

!m2

"

E[MeV] = 6.8! 106 cos (2!12)!m212[eV2]

"[g/cm3]Z/A" 1–2 MeV

! > 1

! < cos 2"12


Before Borexino [MeV]E1 10

ee

P

0.2

0.3

0.4

0.5

0.6

0.7

0.8

MSW-LMA Prediction

SNO Data

Ga/Cl Data Before Borexino

Solar Neutrino Survival Probability


Before Borexino

Barger et al.,PRL 95, 211802 (2005)

Friedland et al.,PLB 594, 347 (2004)

[MeV]E1 10

ee

P

0.2

0.3

0.4

0.5

0.6

0.7

0.8

MSW-LMA Prediction

MSW-LMA-NSI Prediction

MaVaN Prediction

SNO Data




Neutrinos and Solar Metallicity

• A direct measurement of the CNO neutrinos rate could help solve the latest controversy surrounding the Standard Solar Model

• One fundamental input of the Standard Solar Model is the metallicity of the Sun - abundance of all elements above Helium

• The Standard Solar Model, based on the old metallicity derived by Grevesse and Sauval (Space Sci. Rev. 85, 161 (1998)), is in agreement within 0.5% with the solar sound speed measured by helioseismology.

• Latest work by Asplund, Grevesse and Sauval (Nucl. Phys. A 777, 1 (2006)) indicates a metallicity lower by a factor ~2. This result destroys the agreement with helioseismology

maybe it was fortuitous agreement before with high metallicity?

• use solar neutrino measurements to help resolve!7Be (12% difference) and CNO (50-60% difference)


Solar Model Chemical ControversyBahcall, Serenelli and Basu, AstropJ 621, L85(2005)

Helioseismology incompatible with low metallicity solar models. Could be resolved by measuring CNO neutrinos

Φ(cm-2s-1)

pp(×1010)

7Be(×109)

8B(×106)

13N(×108)

15O(×108)

17F(×106)

BS05GS 98

5.99 4.84 5.69 3.07 2.33 5.84

BS05 AGS 05

6.05 4.34 4.51 2.01 1.45 3.25

Δ +1% -10% -21% -35% -38% -44%

σSSM

±1% ±5% ±16% ±15% ±15% ±15%


Borexino: the Science Goals• To make the first ever observations of sub-MeV neutrinos in real time,

especially for 7Be neutrinos, testing the Standard Solar Model and the MSW-LMA solution of the Solar Neutrino Problem

• To provide a strong constraint on the 7Be rate, at or below 5%, such as to provide an essential input to check the balance between photon luminosity and neutrino luminosity of the Sun

balance check at 1% level ideal. Requires 7Be flux measured at 5% and pp flux measured at 1% level

• To confirm the solar origin of 7Be neutrinos, by checking the expected 7% seasonal variation of the signal due to the Earth’s orbital eccentricity

• To explore possible traces of non-standard neutrino-matter interactions or presence of mass varying neutrinos.

LJ(neutrino! inferred)LJ(photon)

= 1.4+0.2!0.3(

+0.7!0.6)

J.N. Bahcall and C. Pena-Garay,JHEP 11, 004 (2003)


Borexino: Additional Possibilities for 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?


Detection Principles

• Detection via scintillation light

• Features: • Very low energy threshold• Good position recostruction by time of flight• Good energy resolution

• Drawbacks:• No direction measurements• ν induced events can’t be distinguished from

other β/γ due to natural radioactivity

• Experiment requires extreme purity from all radioactive contaminants


CollaborationAstroparticle and Cosmology Laboratory – Paris, FranceINFN Laboratori Nazionali del Gran Sasso – Assergi, Italy

INFN e Dipartimento di Fisica dell’Università – Genova, ItalyINFN e Dipartimento di Fisica dell’Università– Milano, Italy

INFN e Dipartimento di Chimica dell’Università – Perugia, ItalyInstitute for Nuclear Research – Gatchina, Russia

Institute of Physics, Jagellonian University – Cracow, PolandJoin Institute for Nuclear Research – Dubna, Russia

Kurchatov Institute – Moscow, RussiaMax-Planck Institute fuer Kernphysik – Heidelberg, Germany

Princeton University – Princeton, NJ, USATechnische Universität – Muenchen, Germany

University of Massachusetts at Amherst, MA, USAUniversity of Moscow – Moscow, Russia

Virginia Tech – Blacksburg, VA, USA


Stainless Steel SphereExternal water tank

Nylon Inner VesselNylon Outer Vessel

Fiducial volume

InternalPMTs

Scintillator

Buffer

WaterRopes

Steel platesfor extrashielding

Borexino Detector

MuonPMTs




Fiducial volume

InternalPMTs

Scintillator

Buffer

WaterRopes


Borexino Detector

MuonPMTs

Located in LNGS - 3800 m.w.e. against cosmic rays




Fiducial volume

InternalPMTs

Scintillator

Buffer

WaterRopes


Borexino Detector

MuonPMTs

Active Target: 278 Tons of Liquid Scintillatorin Nylon Vessel of 4.25 m radius




Fiducial volume

InternalPMTs

Scintillator

Buffer

WaterRopes


Borexino Detector

MuonPMTs

1st shield: 890 tons of ultra-pure buffer liquidin a stainless steel sphere of 6.75 m radius




Fiducial volume

InternalPMTs

Scintillator

Buffer

WaterRopes


Borexino Detector

MuonPMTs

External nylon vessel - A barrier against Rnemitted by PMTs and Stainless Steel




Fiducial volume

InternalPMTs

Scintillator

Buffer

WaterRopes


Borexino Detector

MuonPMTs

2214 PMTs detect light emitted by the scintillator1843 with optical concentrators, the rest without for muons




Fiducial volume

InternalPMTs

Scintillator

Buffer

WaterRopes


Borexino Detector

MuonPMTs

2nd shield: 2100 tons of ultra-pure waterin a cylindrical dome




Fiducial volume

InternalPMTs

Scintillator

Buffer

WaterRopes


Borexino Detector

MuonPMTs

200 PMTs mounted on the SSS detectCherenkov light emitted in the water by muons


• Low background nylon vessel fabricated in hermetically sealed low radon clean room (~1 yr)

• Rapid transport of scintillator solvent (PC) from production plant to underground lab to avoid cosmogenic production of radioactivity (7Be)

• Underground purification plant to distill scintillator components.

• Gas stripping of scintlllator with special nitrogen free of radioactive 85Kr and 39Ar from air

• All materials electropolished SS or teflon, precision cleaned with a dedicated cleaning module

Special Methods Developed







Expected (or dream?) Spectrum

0 200 400 600 800 1000-210

-110

1

10

210

310

410

510

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

Photoelectrons [pe]

Energy [MeV]Counts/(10 keV x day x 100 tons)

Expected SpectrumTotal Spectrum 7BeCNO + pep 14C11C 10C


Data: Raw Spectrum (No Cuts)

0 200 400 600 800 1000-210

-110

1

10

210

310

410

510

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

Photoelectrons [pe]


Measured Spectrum

All data after basic selection cuts

Expected SpectrumTotal Spectrum 7Be


Data: Fiducial Cut (100 tons)

0 200 400 600 800 1000-210

-110

1

10

210

310

410

510

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

Photoelectrons [pe]


Measured Spectrum


After fiducial volume cut



Data: α/β Stat. Subtraction

0 200 400 600 800 1000-210

-110

1

10

210

310

410

510

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

Photoelectrons [pe]


Measured Spectrum



After statistical subtraction of !‘s



Data: Final Comparison

0 200 400 600 800 1000-210

-110

1

10

210

310

410

510

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

Photoelectrons [pe]


Measured Spectrum






Energy [keV]200 400 600 800 1000 1200 1400 1600 1800 2000

Counts/(10 keV x day x 100 tons)

-310

-210

-110

1

10

210

310

410

510

Fit: !2/NDF = 185/1747Be: 49±3 cpd/100 tons210Bi+CNO: 23±2 cpd/100 tons85Kr: 25±3 cpd/100 tons11C: 25±1 cpd/100 tons14C 10C

New Results:192 Days


New Results:192 Days

Energy [keV]

400 600 800 1000 1200 1400 1600

Counts/(10 keV x day x 100 tons)

-210

-110

1

10

210

Fit: !2/NDF = 55/607Be: 49±3 cpd/100 tons210Bi+CNO: 20±2 cpd/100 tons85Kr: 29±4 cpd/100 tons11C: 24±1 cpd/100 tons


Systematic & Measurement

Expected interaction rate in absence of

oscillations:75±4 cpd/100 tons

for LMA-MSW oscillations:

48±4 cpd/100 tons

7Be Rate:49±3stat±4syst cpd/100 tons

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

Estimated 1σ Systematic Uncertainties* [%]

*Prior to Calibration


Neutrino Magnetic Moment

EM current affects cross section σSpectral shape sensitive to μνSensitivity enhanced at low energies (σ≈1/T)

!d!

dT

"

W

=2G2

F me

"

#g2

L + g2R

!1! T

E!

"2

! gLgRmeT

E2!

$

!d!

dT

"

EM

= µ2!"#2

em

m2e

!1T! 1

E!

"

Estimate Method90% C.L.10-11 μB

SuperK 8B <11

Montanino et al. 7Be <8.4

GEMMA Reactor <5.8

Borexino 7Be <5.4



ee

P

0.2

0.3

0.4

0.5

0.6

0.7

0.8

MSW-LMA Prediction


MaVaN Prediction

SNO Data




νe Survival ProbabilityGlobal Analysis

• We determine the survival probability for 7Be electron neutrinos νe under the assumption of the high-Z SSM (Bahcall-Pena Garay-Serenelli 2007, BPS07)

•

•

• Consistent with expectation from MSW-LMA (S. Abe et al., arXiv:0801.4589v2)

•

• No oscillations hypothesis (Pee=1) excluded at 4σ C.L.

!!7Be

"= (5.08± 0.25)! 109 cm!2s!1

Pee

!7Be

"= 0.56± 0.10

Pee

!7Be

"= 0.541± 0.017


νe Survival ProbabilityGlobal Analysis

• We determine the survival probability for 7Be and pp electron neutrinos νe under the assumption of the high-Z BPS07 SSM and using input from all solar experiments (cfr. Barger et al., PRL 88, 011302 (2002))

•

•

Pee

!7Be

"= 0.56± 0.08

Pee (pp) = 0.57± 0.09



ee

P

0.2

0.3

0.4

0.5

0.6

0.7

0.8

MSW-LMA Prediction


MaVaN Prediction

SNO Data




After Borexino [MeV]E1 10

ee

P

0.2

0.3

0.4

0.5

0.6

0.7

0.8

MSW-LMA Prediction


MaVaN Prediction

SNO Data

Borexino Data

Ga Data after Borexino



7Be Neutrinos Flux• Note:

• Best estimate prior to Borexino, as determined with global fit to all solar and reactor data, with the assumption of the constraint on solar luminosity (M.C. Gonzalez-Garcia and Maltoni, Phys. Rep 460, 1 (2008)

•

• Assuming the high-Z BPS07 SSM and the constraint on solar luminosity, we obtain:

•

fBe = 1.03+0.24!1.03

fBe = 1.02± 0.10

fi =!i

!SSMi

!!7Be

"= (5.18± 0.52)! 109 cm!2s!1


pp and CNO Neutrinos FluxesRl [SNU] =

!

i

Rl,ifiPl,iee

i = {pp, pep,CNO,7 Be,8 B}l = {Ga,Cl}

P l,iee Survival Probability

Averaged over Threshold

fi Ratio between measuredand predicted flux

fBe = 1.02± 0.10SNOBorexino

fB = 0.87± 0.08

RthGa [SNU] = 38.56fpp + 2.34fCNO + 19.44fBe + 5.43fB

RthCl [SNU] = 0.12fpep + 0.11fCNO + 0.59fBe + 2.58fB

RGa = 68.10± 3.75 SNURCl = 2.56± 0.23 SNU


pp and CNO Neutrinos FluxesWithout Luminosity Constraint:

fpp = 1.04+0.18!0.25fpp = 1.04+0.13

!0.20

With Luminosity Constraint:

fpp = 1.004+0.008!0.020 fpp = 1.02± 0.02



M. Altmann et all. (GNO Coll.),PLB 616, 574 (2005)

LCNO/LJ < 6.5% 3!LCNO/LJ < 6.2% 3!

LCNO/LJ < 13.8% 3!



0 200 400 600 800 1000-210

-110

1

10

210

310

410

510

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

Photoelectrons [pe]


Measured Spectrum







CNO, pep

0 200 400 600 800 1000-210

-110

1

10

210

310

410

510

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

Photoelectrons [pe]


Measured Spectrum






Removal of 11C BackgroundMeasuring 25 cpd/100 tons of 11C

Major background for CNO and pepCNO: 5 cpd/100 tonspep: 2 cpd/100 tons

Long-lived isotope (30 min mean life)Simple coincidence with muon impractical (dead time kills!)

Deutsch 1995:Neutron must be emitted with 11C formationTag in coincidence with muon and neutron capture (300 μs, 2.2 MeV γ-ray)

@Princeton 2005:First detailed calculation of cosmogenic production rate!95% of 11C produced in conjuction with a neutron!11C background can be reduced very significantly in Borexino and KamLAND!Opens opportunity for measurement of CNO and pep neutrinos in Borexino and KamLAND!



μ Track


μ Track

11C


μ Track

11Cn Capture


μ Track

11Cn Capture


Time / us0 100 200 300 400 500 600 700

Voltage / mV

-100

-50

0

50

100

Run56_48853

Improved Electronics


Time / us0 100 200 300 400 500 600 700

Voltage / mV

-100

-50

0

50

100

Run56_48853

Improved Electronics


• Borexino opened the study of the solar neutrinos in real time below the barrier of natural radioactivity (4 MeV)

Two measurements reported for 7Be neutrinos, favor MSW-LMA solutionBest limits for pp and CNO neutrinos, combining information from all solar and reactor experimentsOpportunities to tackle pep and CNO neutrinos in direct measurement

• Borexino will run comprehensive program for study of antineutrinos (from Earth, Sun, and Reactors)

• May prove solar origin of 7Be signal by study of seasonal oscillations

• Borexino a powerful observatory for neutrinos from Supernovae explosions within few tens of kpc

Conclusions


1989-92: Conception, start of CTF program

1995-96: Low background

achieved in CTF

1997-98: Borexino Funded

August 16 2002: Borexino Mishap

2005: Restarts of Fluid Operations

August 16 2007: Borexino Paper


Martin DeutschJanuary 29, 1917August 16, 2002



achieved in CTF






http://en.wikipedia.org/wiki/August_17


http://en.wikipedia.org/wiki/2005


John BahcallDecember 30, 1934

August 17, 2005 Martin DeutschJanuary 29, 1917August 16, 2002



achieved in CTF






http://en.wikipedia.org/wiki/December_30

http://en.wikipedia.org/wiki/December_30











• Letter submitted to online pre-print server

• arXiv:0805.3843

• See also mini-talks and posters by:

• D. d’Angelo:• “The Borexino detector: very low background levels in the scintillator”

• D. Franco:• “Performances of the Borexino Deetector”

• S. Hardy:• “Source Insertion and Location Systems for the Borexino Solar

Neutrino Detector”

• P. Lombardi:• “The Borexino detector: photomultipliers system”

• R. Saldanha:• “Cosmogenic 11C tagging in organic liquid scintillators”

More Info


The End


Documents

192 days of Borexino - slac.stanford.edu · Cristiano Galbiati on behalf of Borexino Collaboration Tuesday, May 27, 2008 2. Solar Neutrinos Spectrum Tuesday, May 27, 2008 3. Solar