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Neutrino-nucleus cross section measurements at the SNS
Complimentary to RIB Exotic particle instead of exotic isotopes
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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 happen every century in our Galaxy, but the last one
observed was over 300 years ago
• Dominant contributor to Galactic nucleosynthesis
• Neutrinos and the weak interaction play a crucial role in the mechanism, which is not not well understood
SN neutrino spectra, 0.1 s post-bounce
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Neutrinos and Core Collapse SN
The weak interaction plays a crucial role in supernova !!!
• 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 • Prompt supernova
mechanism fails
• 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)].
• In the outer layers, neutrino reactions may be the dominant source for boron & fluorine [Woosley et al. (1990)] and rare isotopes like 138La and 180Ta [Heger et al. (2005)].
• 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)].
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Supernova observations• Measurement of the neutrino energy
spectra and time distribution from a Galactic supernova would provide a wealth of information on the conditions in supernovae, neutrino oscillations, etc.
Bruenn et al. (2004)
ADONIS• An accurate understanding of neutrino cross sections is important for designing and interpreting measurements of neutrinos from supernovae.
• Nuclei of interest: 2H, C, O, Pb
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Neutrinos Nuclei Interactions are:Important for understanding of supernovae mechanism
Important for neutrino detection from SN 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
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Currently operating at low power 100kW in FY07 ~7x1012 / spill
Crucial to understand neutron background, especially for t=1-10s
• Negligible fast neutron background expected after ~ 1 s
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Background Studies Layout
60 tons of steel installed
2 stacks of shield block
52”x 52” x 60” high
rack
Desk/PC
4 Detector stations
5” liquid scintillator3He counters
Open for prototype testing
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Installation
n/ separation
• Block installation complete
• Detectors and data acquisition system ready
• Taking data as we speak
PuBe
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SNS Collaboration
http://www.phy.ornl.gov/nusns
System Lead
TheoryMcLaughlin (NCSU)
Hix (ORNL)
SNS & Backgrounds Blackmon (ORNL)
Segmented Detector Hungerford (Houston)
Homogeneous Detector Stancu (Alabama)
A Scattering Scholberg (Duke)
Veto Greife (Mines)
Bunker Cianciolo (ORNL)
Project coordinator Efremenko (Tenn)
• Active, diverse collaboration
– 20 institutions
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Timeline
Item $M
Bunker 2.3
Veto 1.1
Segmented Detector 1.2
Homogeneous Detector 1.2
Mini-CLEAN 0.5
Cont. & Escl. (FY06$) +50%
Project Cost
FY 2010-FY2011Construction
FY07NSAC LRP
August 2005Proposal submitted
Likely withdrawn
August 2004“First green light” from SNS
October 2004Neutrino Matrix
March 2004Study report completedLetter of Intent to SNS
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Summary & Outlook
• Neutrino scattering and reactions are important for understanding supernovae– Influence core collapse
– Affect shock dynamics
– Modify the distribution of iron-peak elements
– May be the dominant source of B, F, 138La, 180Ta
– Affect r process nucleosynthesis
• The combination of high flux and favorable time structure at the SNS can allow a diverse program of measurements– High statistics in less than 1 year of operation
• We have a strong collaboration of experimentalists and theorists