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SOX: Short (distance neutrino) Oscillations with BoreXinoThe cerium experiment: CeSOX

The chromium experiment: CrSOXPerspectives and conclusions

Outlook

The SOX experiment

Jonathan Gaffioton behalf of the SOX collaboration

CNRS / APC

September 12, 2014

Jonathan Gaffiot: CNRS / APC The SOX experiment 1 / 16



Outlook

Outlook

1 SOX: Short (distance neutrino) Oscillations with BoreXinoThe scientific caseThe Borexino detectorThe SOX experiment

2 The cerium experiment: CeSOXProductionShielding and transportSignal and backgrounds

3 The chromium experiment: CrSOXProductionShielding and transportSignal and backgrounds

4 Perspectives and conclusionsCompared sensitivitySource activity measurementSchedule and perspectivesConclusions




The scientific caseThe Borexino detectorThe SOX experiment

Outlook









The scientific case

3 anomalies at the ∼ 3σ level eachLNSD [1] and MiniBooNE [2, 3]Calibration of radiochemical solar experiments [7, 8, 6]Short baseline reactor experiments [9, 10, 11, 13]

The 3 anomalies point toward a new oscillation with |∆m2new| ∼ 0.1− 5 eV2

See talks of Patrick Huber, Michele Maltoni and Thierry LasserreN

OB

S/(

NE

XP) p

red

,new

Distance to Reactor (m)

Bu

ge

y−

3

RO

VN

O

Bu

ge

y−

4

Bu

ge

y3

Bu

ge

y3

Go

esg

en

Go

esg

en

Go

esg

en

ILL

Kra

sn

oya

rsk

Kra

sn

oya

rsk−

2

Kra

sn

oya

rsk−

3

Pa

loV

erd

e

CH

OO

Z

101

102

103

0.7

0.8

0.9

1

1.1

SOX goal: unambiguously test the short baseline oscillation hypothesis





The Laboratori Nazionali del Gran Sasso (LNGS)

ref [12]

Deep underground laboratory: 1400m ⇒ 3800m.w.e. and 1.2muons h−1 m−2





The Borexino detector

Water volumeMuon veto and

radioactivity shielding2.1 kt, r=9 m, 208 PMT

Buffer volumeRadioactivity shielding

800 t, r=6.85m, 2212 PMT

Active volumeLiquid scintillator (PC+PPO)

300 t, r=4.25m

Stainless steel tanks

Nylon vessels

Stainless steel plates10 cm + 4 cm

1.05 m

8.5 m

ref [12]





The Short (distance neutrino) Oscillations with BoreXino experiment

SOX: Deploy a neutrino and an antineutrino source under Borexino

ref [15]ref [4]





Neutrino and antineutrino sources

Neutrino source:51Cr

Electron capture:753 keV (90%) and433 keV (10%) νe

Half-life: 27.7 dayProduced byneutron irradiationof (stable) 50CrScattering on e−

Backgrounds:210Po, 210Bi, and7Be solar νe

Activity: ∼ 10MCi⇒ 2 kW

144Ce

144Pr

144Nd

696 keV

17 mn

285 d

ß- < 318 keV

ß- < 2996 keV

97.9 %

ß- < 913 keV 1 %

ß- < 2301 keV 1 %

γ 2185 keV

0.7 %

Antineutrino source:144Ce-144Pr

β− decay: ν̄e up to3.00MeV144Ce half-life: 285 dExtracted from nuclearspent fuelInverse beta decay

Threshold 1.8MeVCross-section ∼ 10times higher than νeCoincidence betweene+ and neutron

∼ background freeActivity: ∼ 100 kCi⇒ 0.8 kW

Main issue: produce and bring the sources to LNGS




ProductionShielding and transportSignal and backgrounds

Outlook









Production

One company can produce such a source: the Russian FSUE Mayak PA.

1 Start with 2.8 t of fresh spent fuel (1.65 year of cooling time) from Kola NPP2 Cutting, digestion and PUREXr process⇒ lanthanides and actinides concentrate3 Displacement chromatography ⇒ extraction of all cerium isotopes ∼ 5 kg4 Precipitation, calcination in CeO2, pressing, encapsulation and insertion in shield





Shielding and transport2.185MeV γ ray with intensity 0.7%

19 cm tungsten alloy shielding (2.4 t)density 18 g/cm3, leading to 5× 10−7 attenuation

Selected cask: MTR from Areva TN (21 t)Certification extension ongoingFrom Mayak to LNGS through France:train, boat, truck ; supervised by Areva TN





Signal and backgrounds

Eν (MeV)

Arb

itra

ry U

nit

144Ce−

144Pr antineutrino emitted spectrum in secular equilibrium

0 0.5 1 1.5 2 2.5 310

−2

10−1

100

Cou

nts

per

0.10

mM

eV−1

bin

2 3 4 5 6 7 80

50

100

150

200

250

300

350

400

450

500

No oscillationssin2(2θ

new) = 0.10, Δm2

new= 0.5 eV2

sin2(2θnew

) = 0.10, Δm2new

= 2 eV2

R/E (m MeV−1)

Osc

/No

osc

ratio

2 3 4 5 6 7 80.85

0.9

0.95

1

∆m2new = 2.5 eV2 and sin2(2θ) = 0.16

Pattern in L and in E : shape-only signature+ disappearance measurementHuge overburden and perfect material purity⇒ no backgrounds except geoneutrinos andreactor neutrinos!Simulations show no source inducedbackground





Outlook









Production

ref [14]Re-use of Gallex Cr,36 kg enriched in50Cr at 38%

Irradiation plannedat Oak Ridge HFIRSimulations ongoingto optimize activity:currently with 2back-to-back cycles,5–6MCi are reached





Shielding and transport

Due to the short period of 51Cr, the whole procedure below must not last morethan 1 week

1 After irradiation, chromium is dispatched in hot cell between 3 capsules2 Each capsule is inserted in separated transport casks specially built by Croft (UK)3 Containers are transported by plane to Italy, then by truck to Nucleco in Casaccia4 Cr is gathered in 1 source in hot cell then inserted in a tungsten alloy shield5 The source is transported to LNGS and mounted within the calorimeter6 The whole system is inserted in the pit for 3 months7 Repeat steps 1 to 6 to reach a total of 10MCi

ref [14]





Signal and backgrounds

electron recoil energy [MeV]0.2 0.4 0.6 0.8 1 1.2 1.4 1.6

#[per

133tx

1da

yx0.1MeV

]

-110

1

10

210

310

51Cr

11C

pep-ν

7Be-ν

210Po

ref [15]

2241

142

eV2Δm0.32θsin

==

ref [5]

Below 753 keV, 2 main backgrounds:Solar neutrinos (from 7Be)210Po which peaks around 450 keV

Both are well known!Pattern measurable in L: shape-only signature+ disappearance measurement




Compared sensitivitySource activity measurementSchedule and perspectivesConclusions

Outlook









--- RA (95% C.L.)

--- RA (99% C.L.)

--- SOX Cr (95% C.L.)

--- SOX Cr (99% C.L.)

--- SOX Ce (95% C.L.)

--- SOX Ce (99% C.L.)

Global fit. Giunti et al.Physical Review D, vol.88, 073008, 2013

ref [5]

Sensitivity is dominated by statistic and activity uncertainty (particularly at high∆m2

new)





Source activity measurement

Main source activity measurement: calorimetryCross-check with other methods based on sampling are foreseen

Goal: the percent level (at least 1.5%)

(multi layer insulation not represented)

Cerium calorimeter1 day measurement before deployment

Chromium calorimeterContinuous measurement during the

experiment





Schedule and perspectives

ScheduleFebruary 2015: arrival of fresh nuclear fuel at MayakNovember 2015: delivery of the cerium source by MayakDecember 2015: start of 1.5 year of data-taking with 144Ce2016+: chromium irradiation at HFIRLater: deployment of new sources inside Borexino!

In the water volume(SOX-B)⇒ not before the end ofthe solar neutrinoprogram (2017 ?)At the center of thedetector (SOX-C), butneed a major upgrade ofthe detector

SOX-C [4]





Conclusions

SOX is designed to test unambiguously the short baseline oscillation hypothesis,searching for the oscillation as an energy and/or distance pattern

Two sources are planned: the 51Cr neutrino source and the 144Ce-144Prantineutrino source

The 144Ce-144Pr source has entered the production phase and is expected by theend of 2015 at LNGS

Important effort on calorimetry and 144Pr electron spectrum measurement tocontrol systematic uncertainties at the target level (at least 1.5%)

The 51Cr source will use the Gallex chromium and be irradiated twice at HFIR toget enough statistic, but the schedule is not fixed


Back-upReferences

Back-up


Back-upReferences

Cerium production 1


Back-upReferences

Cerium production 2


Back-upReferences

Cerium production 3


Back-upReferences

Gallex

The Gallex source

Gallex enriched chromium shippedat Saclay


Back-upReferences

References I

[1] A. Aguilar-Arevalo et al.Evidence for neutrino oscillations from the observation of anti-neutrino(electron) appearance in a anti-neutrino(muon) beam.Phys.Rev., D64:112007, 2001.

[2] A.A. Aguilar-Arevalo et al.Unexplained Excess of Electron-Like Events From a 1-GeV Neutrino Beam.Phys.Rev.Lett., 102:101802, 2009.

[3] A.A. Aguilar-Arevalo et al.Event Excess in the MiniBooNE Search for ν̄µ → ν̄e Oscillations.Phys.Rev.Lett., 105:181801, 2010.

[4] Davide Bravo.ν/ν̄ sources in borexino.ICHEP, July 2014.http://indico.ific.uv.es/indico/getFile.py/access?contribId=191&sessionId=26&resId=0&materialId=slides&confId=2025.

[5] Barbara Caccianiga.Future short baseline sterile neutrino searches with nuclear decays.XXVI International Conference on Neutrino Physics and Astrophysics, June 2014.https://indico.fnal.gov/getFile.py/access?contribId=296&sessionId=25&resId=0&materialId=slides&confId=8022.

[6] C. Giunti, M. Laveder, Y.F. Li, Q.Y. Liu, and H.W. Long.Update of Short-Baseline Electron Neutrino and Antineutrino Disappearance.Phys.Rev., D86:113014, 2012.

[7] Carlo Giunti and Marco Laveder.Short-Baseline Active-Sterile Neutrino Oscillations?Mod.Phys.Lett., A22:2499–2509, 2007.

[8] Carlo Giunti and Marco Laveder.Statistical Significance of the Gallium Anomaly.Phys.Rev., C83:065504, 2011.


http://indico.ific.uv.es/indico/getFile.py/access?contribId=191&sessionId=26&resId=0&mater ialId=slides&confId=2025

http://indico.ific.uv.es/indico/getFile.py/access?contribId=191&sessionId=26&resId=0&mater ialId=slides&confId=2025

https://indico.fnal.gov/getFile.py/access?contribId=296&sessionId=25&resId=0&materialId=sl ides&confId=8022

Back-upReferences

References II

[9] Patrick Huber.Determination of antineutrino spectra from nuclear reactors.Phys. Rev. C, 84:024617, Aug 2011.

[10] Patrick Huber.Erratum: Determination of antineutrino spectra from nuclear reactors [phys. rev. c 84, 024617 (2011)].Phys. Rev. C, 85:029901, Feb 2012.

[11] G. Mention et al.The Reactor Antineutrino Anomaly.Phys. Rev., D83:073006, 2011.

[12] Mikko Meyer.Search for sterile neutrinos with the borexino detector.PANIC, August 2014.https://indico.desy.de/getFile.py/access?contribId=7&sessionId=35&resId=0&materialId=slides&confId=8648.

[13] Th. A. Mueller, D. Lhuillier, M. Fallot, A. Letourneau, S. Cormon, M. Fechner, L. Giot, T. Lasserre, J. Martino, G. Mention,A. Porta, and F. Yermia.Improved predictions of reactor antineutrino spectra.Phys. Rev. C, 83:054615, May 2011.

[14] Marco Pallavicini.Borexino & sox.Princeton, January 2014.

[15] Michael Wurm.Experimental searches on sterile neutrinos.12th International Conference on Heavy Quarks and Leptons (HQL 2014), August 2014.https://indico.mitp.uni-mainz.de/getFile.py/access?contribId=33&sessionId=6&resId=0&materialId=slides&confId=23.


https://indico.desy.de/getFile.py/access?contribId=7&sessionId=35&resId=0&materialId=slide s&confId=8648

https://indico.mitp.uni-mainz.de/getFile.py/access?contribId=33&sessionId=6&resId=0&materi alId=slides&confId=23

https://indico.mitp.uni-mainz.de/getFile.py/access?contribId=33&sessionId=6&resId=0&materi alId=slides&confId=23

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