Inside of SNO+ detector during cavity water fill, May 2014

Future Geoneutrino Detections

SNO+

Joachim RoseUniversity of Liverpool

Neutrino GeoscienceParis, June 2015

SNO+ Collaboration

Queen’s Univ.Laurentian Univ.Univ. of AlbertaTRIUMFSNOLAB

BNL, AASU,Penn., UNC,U Washington,UC Berkley/LBNLChicago,UC Davis

OxfordSussexLancasterLiverpoolQMUL

TU Dresden LIP LisboaLIP Coimbra

UNAM

Overview

I Conversion of SNO detector :

SNO+ construction progress

I Geoneutrino inverse beta-decayevent rate calculation

I Continental vs oceaniccrust abundances

I Accuracy and errors ofsurvival probability estimates

SNO detector cavern wide angle ’fisheye’ view

Future SNO+ detector characteristics

SNO detector, image National Geographic

I conversion of SNO to search forneutrinoless double beta-decay

I tellurium loaded into scintillator2340 kg Te at 0.3% loading

I 12 m diameter acrylic vessel

I 780 tons liquid scintillator

I surrounded by ⇡ 9500 PMT18 m diameter support structure

I 1700 tonnes water inner shielding5300 tonnes water outside

I cavern Urylon liner radon seal,anti-radon cover gas layer

I location Sudbury, Ontario, Canada

I depth 2092 m below surface6010 m water equivalent

Conversion into SNO+

Earlier presentation by Mark Chen at Neutrino Geoscience 2013 conference.

Fibre coupled LED light pulse event

Telluric acid, underground storage

I install underground liquid scintillator plant (X)

I add an acrylic vessel hold-down mechanism XI repair, i.e. PMT bases, cavity floor liner XI upgrade the data acquisition, trigger, electronics XI improve the cover gas radon exclusionXI change the calibration source manipulator X

prepare new radioactive calibration sources XI new fibre coupled LED calibration system XI new simulation and event reconstruction codes XI develop technique for tellurium loading XI acquire tellurium acid, store underground XI raise cavern and acrylic vessel water levels ( X)

I fill with (pure or Te loaded) scintillator

Install Liquid Scintillator Plant ` Scintillator plants

Richard Ford (SNOLAB) NSERC Review, Kingston, 6-Dec-2014

`

Richard Ford (SNOLAB) LRT2015, Seattle, 18-Mar-2015

`

Richard Ford (SNOLAB) LRT2015, Seattle, 18-Mar-2015

Neutrinoless double beta-decay

Envisaged detector operation sequence:- short initial water fill,- short liquid scintillator background verification,- long tellurium loaded scintillator phase (geoneutrino data),- afterwards pure liquid scintillator phase (geoneutrino data)

Why yet another geoneutrino rate calculation?

[MeV]ν

anti-neutrino energy E1.8 2 2.2 2.4 2.6 2.8 3 3.2

[TN

U/M

eV]

νev

ent r

ate

dR/d

E

0

20

40

60

80

100

Geoneutrino inverse beta-decay event rate

I Energy spectrum (or spectra)are necessary input for detectorsimulation and data analysis

I Which e↵ects change theshape of the energy spectrum?

I Expected inverse beta-decayevent rate at SNO+ location

R = 39.2 TNU

For a specific chosen set ofassumptions1, i.e. thorium anduranium abundances.

1S. T. Dye, Earth and Planetary Science Letters 297 (2010) 1-9

Geoneutrino flux prediction

d�i (~R)dE⌫̄

=

ZdV

⇢(~r)

4⇡|~R �~r |2

· ai (~r)Ci

⌧imi· fi (E⌫̄) · Ps(E⌫̄ , r̃, R̃, ne(̃r

0))

I Adaptive Monte Carlo volume integration (GSL/FGSL, Vegas)

I Earth model: Crust 2.0 and PREM (layer depth, density)

I Thorium and uranium abundances as in Dye (2010)

I Th and U decay chains (rates, energy spectra) as in Fiorentini (2007) 2

I Neutrino survival probability calculation : new code

I three mass eigenstates neutrino oscillation

I electron-neutrino interaction potential (matter e↵ect)

I varying electron number density ne (̃r0) along neutrino path

I Oscillation parameters: Forero et al., Physical Review D 90 (2014)

2Fiorentini, Lissia, Mantovani, Physics Reports 453 (2007)

Continental vs oceanic crust, elevation

longitude [degrees]150− 100− 50− 0 50 100 150

cos(

thet

a)

1−

0.8−

0.6−

0.4−

0.2−

0

0.2

0.4

0.6

0.8

1

0

1000

2000

3000

4000

5000

longitude [degrees]270 272 274 276 278 280 282 284 286 288

cos(

thet

a)

0.6

0.65

0.7

0.75

0.8

0

100

200

300

400

500

600

I Crust 2.0 model

I select continental (oceanic) crust by elevation only

I predicted SNO+ rate : 39.8 TNU

I compare with 39.2 TNU, Dye (2010)

Select by elevation and crust thickness

longitude [degrees]150− 100− 50− 0 50 100 150

cos(

thet

a)

1−

0.8−

0.6−

0.4−

0.2−

0

0.2

0.4

0.6

0.8

1

10000

20000

30000

40000

50000

60000

70000

I Crust 2.0 model

I add all tiles of crust thickness > 15 km to continental crust

I new predicted SNO+ rate : 41.5 TNU

I previously, select by elevation only, rate was 39.8 TNU

Survival probability, for three neutrino states, with matter e↵ect

ı ~ d

dt

| ⌫(t) > =

"1

2E⌫U†

0 0 00 �m2

21 00 0 �m2

31

!U+

V(t) 0 00 0 00 0 0

!#| ⌫(t) >

V (t) =p2 · GF · ne(~r(t) )

New numerical code:3

I Break neutrino path into (many) steps of constant matter density

I For each step solve equation numerically (eigenvalue problem)

I Compare numerical values (LAPACK95) against analytical solution

I Checks against known special cases (exponential, constant, zero density)

I Similar to GLoBES (⌫ beams), optimised for Earth volume integration

I Also run as parallel calculations on a GPU, speedup ⇠ 100 times

3R. Fair, S. Hussain, B. Mawdsley, Final year projects, Liverpool, 2014/15

Survival probability

Frequently made approximation:

Ps ⇡ 1� sin

2(2✓12) · sin2(1.27�m

212L

E

) ⇡ 0.56± 0.02

Full calculation with three neutrinos, matter e↵ect, Earth volume average:

neutrino energy [MeV]1.8 2 2.2 2.4 2.6 2.8 3 3.2 3.4

aver

age

prob

abilit

y

0.54

0.545

0.55

0.555

0.56

0.565

0.57

0.575

0.58

I Errors shown are due to numerical integration over volume.

I There is an (expected) change of survival probability with energy.

I Small e↵ect relative to the overall error due to sin

2(2✓12).

Uncertainty of neutrino oscillation parameter estimates

Visualisation of Nu-Fit 2.0 ��2 data, JHEP 11 (2014) 052, arXiv:1409.5439

0.019 0.02 0.021 0.022 0.023 0.024 0.0250.27

0.28

0.29

0.3

0.31

0.32

0.33

0.34

0

1

2

3

4

5

6

7

8

9

projection: sin^2(theta13) sin^2(theta12) Delta_chi^2

0.019 0.02 0.021 0.022 0.023 0.024 0.0254.15−

4.14−

4.13−

4.12−

4.11−

4.1−

0

1

2

3

4

5

6

7

8

9

projection: sin^2(theta13) Log10(Delta_m21^2/[eV^2]) Delta_chi^2

0.27 0.28 0.29 0.3 0.31 0.32 0.33 0.344.15−

4.14−

4.13−

4.12−

4.11−

4.1−

0

1

2

3

4

5

6

7

8

9

projection: sin^2(theta12) Log10(Delta_m21^2/[eV^2]) Delta_chi^2

0.019 0.02 0.021 0.022 0.023 0.024 0.025

0.4

0.45

0.5

0.55

0.6

0

1

2

3

4

5

6

7

8

9

projection: sin^2(theta13) sin^2(theta23) Delta_chi^2

0.019 0.02 0.021 0.022 0.023 0.024 0.025

2.35

2.4

2.45

2.5

2.55

2.6

0

1

2

3

4

5

6

7

8

9

projection: sin^2(theta13) Delta_m31^2/[1e-3_eV^2] Delta_chi^2

0.4 0.45 0.5 0.55 0.6

2.35

2.4

2.45

2.5

2.55

2.6

0

1

2

3

4

5

6

7

8

9

projection: sin^2(theta23) Delta_m31^2/[1e-3_eV^2] Delta_chi^2

0.019 0.02 0.021 0.022 0.023 0.024 0.025

150−

100−

50−

0

50

100

150

0

1

2

3

4

5

6

7

8

9

projection: sin^2(theta13) Delta_CP/deg Delta_chi^2

0.4 0.45 0.5 0.55 0.6

150−

100−

50−

0

50

100

150

0

1

2

3

4

5

6

7

8

9

projection: sin^2(theta23) Delta_CP/deg Delta_chi^2

2.35 2.4 2.45 2.5 2.55 2.6

150−

100−

50−

0

50

100

150

0

1

2

3

4

5

6

7

8

9

projection: Delta_m31^2/[1e-3_eV^2] Delta_CP/deg Delta_chi^2

0.27 0.28 0.29 0.3 0.31 0.32 0.33 0.34

0.4

0.45

0.5

0.55

0.6

0

1

2

3

4

5

6

7

8

projection: sin^2(theta12) sin^2(theta23) Delta_chi^2

0.27 0.28 0.29 0.3 0.31 0.32 0.33 0.34

150−

100−

50−

0

50

100

150

0

1

2

3

4

5

6

7

8

9

projection: sin^2(theta12) Delta_CP/deg Delta_chi^2

0.27 0.28 0.29 0.3 0.31 0.32 0.33 0.34

2.35

2.4

2.45

2.5

2.55

2.6

0

1

2

3

4

5

6

7

8

9

projection: sin^2(theta12) Delta_m31^2/[1e-3_eV^2] Delta_chi^2

4.15− 4.14− 4.13− 4.12− 4.11− 4.1−

0.4

0.45

0.5

0.55

0.6

0

1

2

3

4

5

6

7

8

9

projection: Log10(Delta_m21^2/[eV^2]) sin^2(theta23) Delta_chi^2

4.15− 4.14− 4.13− 4.12− 4.11− 4.1−

150−

100−

50−

0

50

100

150

0

1

2

3

4

5

6

7

8

9

projection: Log10(Delta_m21^2/[eV^2]) Delta_CP/deg Delta_chi^2

4.15− 4.14− 4.13− 4.12− 4.11− 4.1−

2.35

2.4

2.45

2.5

2.55

2.6

0

1

2

3

4

5

6

7

8

9

projection: Log10(Delta_m21^2/[eV^2]) Delta_m31^2/[1e-3_eV^2] Delta_chi^2

I Six oscillation parameters

I 15 possible pairs

I Selected pairs(sin2(✓13), sin2(✓12)),(sin2(✓23),�m

231),

(�m

221, �CP)

I Turn ��2(x , y) intoprobability P(x , y)

I Generate random (xi , yi ) pairs

I Re-run geoneutrino calculation

I Study variations in predicted rate

Oscillation parameter uncertainty

inverse beta-decay event rate [TNU]40 40.5 41 41.5 42 42.5 43 43.5 44 44.5 45

num

ber o

f tria

ls

0

2

4

6

8

10

12

14

16

18Entries 100Mean 42.54RMS 0.7246

I Repeat calculation with sets of random oscillation parameter values

I Equal probability of each trial, consistent with ��2 distributions

I The predicted inverse beta-decay rate is (42.5± 0.8) TNU

I Appears to be a change in rate of +1 TNU

I False alarm! See next slide.

Change in event rate vs sin2(✓12)

0

2

4

6

8

10

12

14

16

inverse beta-decay event rate [TNU]40 40.5 41 41.5 42 42.5 43 43.5 44 44.5 45

)12θ(2

sin

0.26

0.27

0.28

0.29

0.3

0.31

0.32

0.33

0.34

0.35

I Shown are 100 trials, random oscillation parameters sets

I Expected strong correlation: rate and sin2(✓12).

I Forero et al., PhyRev D 90 (2014): sin2(✓12) = 0.323.

I Nu-Fit 2.0, JHEP 11 (2014) 052, sin2(✓12) = 0.304

I Di↵erence in sin2(✓12) estimate explains di↵erent rates.

I Other mixing variables with far less impact.

Scale of matter e↵ect

number of steps0 5 10 15 20 25 30

even

t rat

e [T

NU

]

53.8

53.9

54

54.1

54.2

54.3

54.4

I Example arbitrary detector location, high flux region (Himalaya).

I Neutrino propagation in steps of constants electron number density.

I Zero steps is vacuum propagation (zero density).

I Small increase in rate of ⇠ 0.2 TNU or ⇠ 0.4 % (as expected).

I Beyond ⇠ 10 steps no further improvement in accuracy.

What if electron number density is higher (lower) than expected?

relative change in electron number density0 0.2 0.4 0.6 0.8 1 1.2

inve

rse

beta

dec

ay e

vent

rate

[TN

U]

53.9

53.95

54

54.05

54.1

54.15

54.2

I Example arbitrary detector location, high flux region (Himalaya)

I Depending on chemical composition more (less) electron density,i.e. electron to nucleon ratio (Z/A) changes with hydrogen content

I Rate change of ⇠ 10�3 TNU per percent in electron number density.

I E↵ect much smaller than present error of rate measurement.

Summary, conclusion, outlook, questions

I Conversion of detector toSNO+ nearly complete

I Cavern and acrylic vesselwater fill underway

I Expect first geoneutrino(candidate) events in 2016

I Precise calculation of survivalprobability implemented

I Constant survival probabilityapproximation seems adequate

Q1 Will local models alter thepredicted energy spectrum?

Q2 How to combine local modelsand exact survival probability?