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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