Inner Nylon Vessel - Universität Hamburg

Search for new Physics with SOX
Tagung der Deutschen Physikalischen Gesellschaft
Mainz 2014
Mikko Meyer
on behalf of the BOREXINO Collaboration
Mikko Meyer
Institut für Experimentalphysik (Universität Hamburg) DPG 2014 - Mainz
Motivation

SOX: Short distance neutrino Oscillations with BoreXino
P (ν e →ν e )≈1−sin 2 ( 2θ 14) sin 2 (Δ m 241

L
)
4E
Motivation:

Search for sterile neutrinos and other short distance effects

Measurement of neutrino magnetic moment

Measurement of gV and gA at low energy
Mikko Meyer
DPG 2014 - Mainz
Slide 2
March 2014
Hints for Sterile Neutrinos
Phys.Rev.D83:073006,2011
 Re-evaluation of neutron life time
→ Cross section of IBD (inverse beta
decay) might be affected
 Reactor anomaly: Flux re-calculations
→ Neutrino deficit observed
 LSND anomaly
 Cosmological hints
 Gallex and SAGE calibration campaign
with artificial neutrino source
→ Both experiments show a deficit w.r.t.
expectations
Mikko Meyer
DPG 2014 - Mainz
Slide 3
March 2014
Artificial Neutrino Source
 The idea to deploy a source in Borexino dates back to the beginning of the project
 Successfully implemented by Gallex (LNGS) and SAGE (Russia)
 Recently, revised and re-proposed by many authors to search for sterile neutrinos:
 N.G. Basov, V. B. Rozanov, JETP 42 (1985)
 Borexino proposal, 1991 (Sr90)
J.N.Bahcall,P.I.Krastev,E.Lisi, Phys.Lett.B348:121-123,1995
N.Ferrari,G.Fiorentini,B.Ricci, Phys. Lett B 387, 1996 (Cr51)
I.R.Barabanov et al., Astrop. Phys. 8 (1997)
Gallex coll. PL B 420 (1998) 114 Done (Cr51)
A.Ianni,D.Montanino, Astrop. Phys. 10, 1999 (Cr51 and Sr90)
A.Ianni,D.Montanino,G.Scioscia, Eur. Phys. J C8, 1999 (Cr51 and Sr90)
SAGE coll. PRC 59 (1999) 2246 Done (Cr51 and Ar37)
SAGE coll. PRC 73 (2006) 045805
C.Grieb,J.Link,R.S.Raghavan, Phys.Rev.D75:093006,2007
V.N.Gravrin et al., arXiv: nucl-ex:1006.2103
C.Giunti,M.Laveder, Phys.Rev.D82:113009,2010
C.Giunti,M.Laveder, arXiv:1012.4356
SOX proposal - ERC 320873 - Feb. 2012 - approved Oct. 2012
Mikko Meyer
DPG 2014 - Mainz
Slide 4
March 2014
Borexino Collaboration
Mikko Meyer
DPG 2013 - Dresden
Slide 5
March 2014
Borexino Experiment

Main Task: Solar neutrino experiment

e.g. 7Be and pep

Neutrino-Electron scattering


Very low background (shielding,
selection and purification)
Additional physics:

Anti-Neutrino detection (e.g. geo-neutrinos)

Inverse beta decay
Credit: Istockphoto. Taken from:http://www.astrobio.net/images/galleryimages_images/Gallery_Image_8047.jpg (bottom) and
http://www.artinaid.com/2013/04/how-does-the-sun-generate-energy/ (top)
Mikko Meyer
DPG 2014 - Mainz
Slide 6
March 2014
Borexino Detector
Solar neutrinos
Geo neutrinos
Mikko Meyer
DPG 2014 - Mainz
Slide 7
March 2014
Borexino Detector
Inner Nylon Vessel
Mikko Meyer
DPG 2014 - Mainz
Slide 8
March 2014
Borexino Detector
Outer Nylon Vessel
Inner Nylon Vessel
Mikko Meyer
DPG 2014 - Mainz
Slide 9
March 2014
Borexino Detector
Outer Nylon Vessel
Inner Nylon Vessel
8.5m
11m
Mikko Meyer
DPG 2014 - Mainz
Slide 10
March 2014
Borexino Detector
Outer Nylon Vessel
Inner Nylon Vessel
Scintillator: 270t PC-PPO
8.5m
11m
Used fiducial volume: 100t
Neutrino detection:

Neutrino – Electron scattering

Inverse beta decay
Mikko Meyer
DPG 2014 - Mainz
Slide 11
March 2014
Borexino Detector
Outer Nylon Vessel
Inner Nylon Vessel
Stainless Steel
Sphere + Water Tank
Structure for 2214 PMTs + 210 PMTs
Mikko Meyer
DPG 2014 - Mainz
Slide 12
March 2014
Mikko Meyer
DPG 2014 - Mainz
Slide 13
March 2014
SOX Concept
Phase A: 51Cr
 8.25 m beneath detector
 EC source
Phase B: 144Ce-144Pr
 Source in water tank
 β− source
Phase C: 144Ce-144Pr
 Source in center of detector
 β− source
Mikko Meyer
DPG 2014 - Mainz
Slide 14
March 2014
Location for 51Cr Source
Mikko Meyer
DPG 2014 - Mainz
Slide 15
March 2014
Artificial Neutrino Sources
Source
51
144
Cr
Production
τ [days]
Decay mode
Energy
[MeV]
Mass
[kg/MCi]
Neutron irradiation of
50
Cr in reactor
40
EC
γ 320 keV (10%)
0.746
0.011
411
β-
<2.9985
7.6
Ce-144Pr Chemical extraction
from spent nuclear fuel
Mikko Meyer
DPG 2014 - Mainz
Slide 16
March 2014
51
Cr Source
 Disappearance experiment
 Sensitivity depends on
●
Statistics (source activity)
• Error on activity (in particular)
and on efficiency
 Background is approximately
constant while signal is not
 Additional: Spatial waves
Mikko Meyer
DPG 2014 - Mainz
Slide 17
March 2014
Credit: L. Vanhoefer
144
Ce-144Pr Source
prompt signal
 2D oscillation pattern

IBD: νe + p → e+ + n
• Prompt signal: Positron annihilation
delayed signal
• Delayed signal: Neutron capture on
hydrogen
• Signal is time and space correlated
 Nearly background free
 Neutrino energy is correlated to visible
energy by:
• Ee= Ev – (Mn – Mp)
Ee: Positron energy, Ev: Neutrino Energy, Mn: Neutron mass Mp: Proton mass
Mikko Meyer
DPG 2014 - Mainz
Slide 18
March 2014
Oscillometry


Observation of waves within detector
With expected Δm² and ~ 1 MeV energy → Wavelength is smaller than detector size,
but bigger than resolution (~ 15 cm)
→ Direct measurement of Δm²14 and θ14
Mikko Meyer
DPG 2014 - Mainz
Slide 19
March 2014
Expected Sensitivity
JHEP08 (2013) 038
 SOX-A:
• 10 MCi
• 1% precision in activity,
1% in FV determination
• 2015/16 (any time during
next solar neutrino phase)
 SOX-B and SOX-C:
• 75 kCi (B), 50 kCi (C)
• 1.5% precision in activity
2.0% bin-to-bin error for systematics
• 2015/2016? (SOX-B)
• 2016-2017 (SOX-C) (major detector upgrade needed)
Mikko Meyer
DPG 2014 - Mainz
Slide 20
March 2014
Other low Energy Neutrino Physics

Weinberg angle

Magnetic moment

Coupling constants gV and gA
(CHARM II: E~10 GeV)
Mikko Meyer
DPG 2014 - Mainz
Slide 21
March 2014
Further Reading...
Mikko Meyer
DPG 2014 - Mainz
Slide 22
March 2014
Summary
 Several anomalies could be explained by a fourth (sterile) neutrino
 BOREXINO experiment well suited for the detection in the favoured range
(Δm²14~1eV²)
 Two sources will be placed near or inside Borexino
• 51Cr (neutrino)
• 144Ce-144Pr (antineutrino)
 Most attractive: Oscillometry → Oberservation of waves within the detector
 Additional physics potential: Neutrino magnetic moment, coupling constants
Mikko Meyer
DPG 2014 - Mainz
END
March 2014
Mikko Meyer – Universität Hamburg - [email protected]
DPG 2014 - Mainz
END
Additional slides...
Mikko Meyer – Universität Hamburg - [email protected]
DPG 2014 - Mainz
END
Technology: Cr-51 Source
 SOX concept similiar to GALLEX 1994
 ~36 kg, 50Cr enriched at 38% irradiated in
high neutron flux reactor
 Possible Reactors: Russia (best), USA,
Europe
 W shield
 Special attention must be paid to the
thermal design
 10MCi (2 kW)
 External T not to high
 Internal T below syntherization (750°)
Mikko Meyer
DPG 2014 - Mainz
Source Production
 Natural Chromium consists of 4 stable
istotopes
Table 1:
Isotopic composition of chromium and thermal
neutron capture cross-section (measured at
2200m/s)
 Production steps:
 Chromium isotopic enrichment
Isotopic
composition
of natural Cr
Isotopic
composition
of the
enriched Cr
used in
GALLEX
Thermal
neutron
capture
crosssections
(barns)
 CrO2F2 CrO3
 Chromium irradiation
 Irradiation @ Siloé (Grenoble, France),
swimming pool reactor with
35MW thermal power
 Dedicated core speciafally built to
contain 34 fuel elements
 Checker-board configuration
 Core immersed in water (moderator,
coolant, shielding)
Mikko Meyer
DPG 2014 - Mainz
50
Cr
4.35%
38.6%
15.9
52
Cr
83.8%
60.7%
0.76
53
Cr
9.5%
0.7%
18.2
54
Cr
2.35%
<0.3%
0.36
Source Production: irradiation
Physics Letters B 342 (1995) 440-450
Mikko Meyer
DPG 2014 - Mainz

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