neutrinos at the sns (spallation neutron source) 1 yu.efremenko 0. a little bit of modern neutrino...
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Neutrinos at the SNS (Spallation Neutron Source)
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Yu.Efremenko
0. A little bit of Modern Neutrino History
1. Why Low Energy Neutrinos are Good
2. Some Proposed Neutrino Experiments at SNS
ORNL
Supper Neutrino Source
Lets Look Back in Time
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The Earliest Neutrino Conference that has Transparencies posted on the WEB is Neutrino 1998
Yes !!! m122 = 7.58·10-5 eV2 sin2(2θ12)=0.87
SNO & KamLAND
From the opening talk by P.Ramond(Florida)
Yes !!! m322 = 2.4·10-3 eV2 sin2 (2θ23)=1.00
SuperK, K2K, MINOS
MiniBoone left door open for some exotic scenarios
Two out of three done!!!!!
Ten Years later
Now We Have New Set of Experimental Challenges
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We have a long list of neutrino properties to study.
Neutrino Mass –> KATRIN + Set of Double Beta Experimentsθ13 -> DoubleChooz, Daya Bay, T2K, NOVA
CP phase–> Long Baseline experiments
At the same time we have to look at what role neutrinos are playing in our Universe.
To do so we have to better understand neutrino interactions with nuclei!
Man Made Neutrino Sources
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Nuclear reactorsE<10 MeV
H.E. “accelerators”E>100 MeV
Stop Pion Facilities 10<E<53 MeV
Very interesting region. It is nicely coincides with
neutrino energies produced during the
Super Novae Explosion
In E-M LSN~L galaxy
In NeutrinosLSN~ 3000 L galaxy
Core-collapse supernovae
SN 1987aAnglo-Australian Observatory
• Destruction of massive star initiated by the Fe core collapse
1053 ergs of energy released
99% carried by neutrinos
• A few should happen every century in our Galaxy, but the last one observed was over 300 years ago (recently discovered ~150 years old remnants of SN in M.W. G1.9+0.3)
• Dominant contributor to Galactic nucleosynthesis
• Neutrinos and the weak interaction play a crucial role in the mechanism, which is not well understood
SN neutrino spectra, 0.1 s post-bounce
Neutrinos and Core Collapse SN
The weak interaction plays a crucial role in supernova !We need good understanding of neutrino interactions !
• Electron capture and the charged-current e reaction are governed by the same nuclear matrix element:e + A(Z,N) A(Z+1,N-1) + e-
• New calculations using a hybrid model of SMMC and RPA predict significantly higher rates for N>40
• Supernovae models w/ new rates:
shock starts deeper and weaker but less impedance
Electron capture and core collapse • Neutrinos interactions are
believed to be crucial in the delayed mechanism
• Realistic treatment of opacities is required for supernova models
opacities
• Many ingredients• Charged-current
reactions on free nucleons (and nuclei)
• Neutral-current scattering
• A coherent scattering• e-e scattering• scattering• annihilation
reactions and nucleosynthesis
• Neutrino reactions with nuclei ahead of the shock may alter the entropy & composition of in fall [Bruenn & Haxton (1991)].
• Neutrino reactions may have an important influence on nucleosynthesis in the r process: setting the neutron-to-proton ratio and altering the abundance pattern [Haxton et al. (1997)].
Supernova Neutrino Observations
High statistic measurement of neutrino signal from SN
will provide wealth of information about SN
dynamics
ADONIS
or
HALO
• An accurate understanding of neutrino cross sections is important for SN neutrino
detectors.
• Nuclei of interest: C, O, Fe, Pb
SN 1987A
Diffuse Supernovae Neutrino (DSN) Detection
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While waiting for SN to happen in the Milky Way we can search for diffuse SN flux
From: C.Lunardini, astro-ph/0610534
Several proposals are aiming to be sensitive enough to see
DSN:•GADZOOKS•HyperKamiokande•UNO•MEMHYS•LENA•LANNDD•GLACIER
Atmospheric Neutrino Background for DSN
Water Cherenkov detectors:
Detectors with Neutron Detection Capabilities:
From LENA proposal: Phys.Rev.D75:023007 there is claim of background free window from 10 till 25 MeV
Irreducible background from atmospheric neutrino interactions:
limit discovery potential.
However background from neutral current reactions
have not been considered yet.We need good understanding of neutrino Carbon and
neutrino Oxygen interactions!!!
Antineutrino Channel with neutron detection will eliminate such a background
,1112
, ee CnC
XO 16
enpe
SuperK92 kton·y
Neutrino Nuclear Interactions at Low MeV Range are:
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Important for understanding of supernovae mechanism Important for neutrino detection from SN
Important for Calculations of backgrounds for DSN Have a general interest for the nuclear theory
So far it is a green field. Only -C interactions have been
accurately studied experimentally.
There are ~ 40% accurate data for d,Fe,I
It is important to provide accurate v-A measurements for wide range of isotopes
Early interest in low energy neutrino nucleus cross sections:
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Twenty five years later, same scientist is still interested in neutrino-nucleus cross sections
Neutrino Coherent Scattering
Detectable only via very low energy (~10keV) nuclear recoil
A
Z0
AD.Z. Freedman PRD 9 (1974)A. Drukier & L. Stodolsky, PRD 30, 2295 (1984)Horowitz et al. astro-ph/0302071
Straight-forward to calculate
“Huge” cross section > 10-39 cm2
Never observedImportant for supernova dynamics (neutrino opacity)
What Physics Could be Learned From Neutrino Coherent Scattering?
Basically, any deviation from SM is interesting...
- Weak mixing angle: could measure to ~few % (new channel)- Non Standard Interactions (NSI) of neutrinos: could significantly improve constraints- Neutrino magnetic moment: hard, but conceivable
K. Scholberg, Phys. Rev D 73 (2006) 033005
It is difficult to do it on Nuclear Reactors because of the continues flux and very low recoil energies
New Facility -SNS
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SNS
Presently being commissioned.0.5 MW power has been achieved last week ~7x1012 / spill
x ~1000 LINAC:
Accumulator Ring:
Repeat 60/sec.
Eventual operation > 1 MW (~FY09)
Similar pulse structure to ISIS greatly suppressed backgrounds1 GeV
(~10x ISIS)
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Accelerator
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Target
Neutrino Production at SNS
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Specific benefits of neutrinos at SNS
•Well known neutrino spectra (DAR)•Separate neutrinos of different flavors by time cut
A+
-~99%
+
e+
p
Fragments
e
26 nsec
2200 nsec
~ 1 GeV
Fragments
CAPTURE
•Very high neutrino intensities ~ 1015 /sec•Pulsed Structure
Potential Locations for Neutrino Experiments at theSpallation Neutron Source
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60 m
protons
20 m2 x 6.5 m (high)
Close to target ~ 20 m 2x107 /cm2/s
=165 to protons lower backgrounds
proposed site inside target building
The SNSTarget hall
There are multiple sites available outside of target building.
Background Studies
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Neutron detectorsNeutron detectors
60 tons of steel60 tons of steel
Space for prototype developmentSpace for prototype development
Now: Background, shielding & protoype studiesNow: Background, shielding & protoype studies
-2 0 2 4 6Time (s)
Cou
nts
Par
ticl
e id neutronsneutrons
gammasgammas
Pulse height
pp~2 C~2 C
60 m
protons
2.8·1020 protons delivered on target in two week period1020 neutrino produced
Power ~ 0.4 MW
Possible Concept of Shielded Enclosure for Neutrino Experiments
• Total volume = 130 m3
4.5m x 4.5m x 6.5m (high)
• Heavily-shielded
• 60 m3 steel ~ 470 tons
1 m thick on top
0.5 m thick on sides
• Active veto
• ~70 m3 instrumentable
• Configured to allow 2 simultaneously operating detectors of up to 40 tons
A coherent scattering
43 m3 liquid detector
Segmented detector for solids
Prototypes for SN detectors
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BL18ARCS
Proton beam (RTBT)
SNS
Cosmic Ray Veto
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1.5 cm iron
wave-length shifting fibersread out by multi-anode PMT
extruded scintillator1 cm x 10 cm x 4.5 m
• Efficienciesmuons ~99% muons7.6 MeV gamma = 0.005% neutron =0.07%
BunkerSensitive to cosmic muonsBlind for gammas from
(n , gamma) capture
Veto R&D
2323
• In collaboration with MECO 100 x 4.5-m planks extruded for SNS
Homogeneous Experiment
• 3.5m x 3.5m x 3.5m steel vessel (43 m3)
• 600 PMT’s (8” Hamamatsu R5912) Fiducial volume 15.5 m3 w/ 41%
coverage
• Robust well-understood design
• E/E ~ 6%• x ~ 15-20 cm• ~ 5 - 7
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First experiments: 1300 events/yr e+12C12N+e- (mineral oil)
450 events/yr e+16O 16F+e- (water)
1000 events/yr x+2H p+n+ x (heavy water)
Performance
E/E = 6.8% at 50 MeVless if corrected for position
•E/E ~ 6%
•x ~ 15-20 cm
• ~ 5 - 7
• Neutron discrimination?
• Layout and coverage
• More compact photosensors60% of mass lost to fiducial cut
Geant4 Monte Carlo simulations ongoing
Standard Model Tests• Shape of the e spectrum from decay is sensitive to scalar and
tensor components of the weak interaction
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KARMEN upper limit
SNS expected1-yr operation
L=0
L=0.11
Armbruster et al., PRL81 (1998)
• We could substantially improve the limit on L with only 1 year of data
μ+μ
Segmented Experiment
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corrugated metal target
straw tube
anode wire16 mm
Target - thin corrugated metal sheet (e.g. 0.75 mm-thick iron)Total mass ~14 tons, 10 tons fiducialOther good metal targets: Al, Ta, Pb
Detector1.4x104 gas proportional counters (straw tube)3m long x 16mm diameter
3D position by Cell ID & charge divisionPID and Energy by track reconstructionExpected Statistic
1100 events/yr e+FeCo+e-
1100 events/yr e+AlSi+e-
4900 events/yr e+Pb Bi+e-
Straw tube R&D
• Currently testing prototypesDiameters between 10-16 mmLengths ranging up to 2 mGases (Ar-CO2, Isobutene, CF4)
• Measure resolution with cosmic muonsEnergy, position, time
• How much can time resolution be improved using pulse shape information?
• Simulations to improve the fast neutron discrimination.
28time (s)
timing problematic
Slow charge collection
ebroad
narrow
The CLEAR (Coherent Low Energy A Recoils) Experiment
A. Curioni
CLEAR
Expect ~190 events/year in 20 kg of xenon >3 keVr
SNS neutronics group calculation of neutron spectrum + Fluka sim through shielding (T. Empl) + Xe detector sim (J. Nikkel) + scaling using measured fluxes
Background for CLEAR
Osc-SNSSterile Neutrinos
Neutrino Oscillations
Test CP Violation
~ 60m
•MiniBooNE/LSND-type detector•Higher PMT coverage (25% vs 10%)•Mineral oil + scintillator (vs pure oil)
•Faster electronics (200 MHz vs 10 MHz)•Located ~60m upstream of the beam
dump/target, this location reduces DIF background
Oscillation Event Rates
Beam Width
S:B Osc. Candidate
sLSND e
600 s 1:1 35(observed R >
10)
FNAL e
600 ns 1:3 ~400
SNS e
695 ns 5:1 ~448/yearExpected for LSND best fit point of : sin22 =0.004 dm2 = 1
Summary & Outlook
• Understanding of neutrino interactions are important for:– Physics of Supernova
– Calculation of response of Large Neutrino Detectors to Milky Way Supernova
– Calculation of backgrounds from DSN
• The combination of high flux and favorable time structure at the SNS is very attractive for diverse program of neutrino studies
• New Proposals like CLEAR and Osc-SNS appeared recently
• We welcome new ideas and participation
• See http://www.phy.ornl.gov/nusns
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