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Neutrinos at the Spallation Neutron Source

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Neutrinos at the Spallation Neutron Source U H M E P Neutrinos at the Spallation Neutron Source CLEAR Ed Hungerford Feb 25, 2008 UniversityE. V. Hungerford of Houston University of Houston 1 U H M E P Collaborating Institutions University of Alabama, Argonne National Laboratory, California Institute of Technology, ado School of Mines, University of Houston, JINR-Dubna, Los Alamos National Laboratory, North Carolina Central University, Oak Ridge National Laboratory, University of South Carolina, University of Tennessee, Triangle Nuclear Laboratory, University of Wisconsin, Yale University Feb 25, 2008 E. V. Hungerford University of Houston 2 U H M E P The Neutrino - n → p + e + νe The electrons from beta decay were observed to have a continuous spectrum Pauli in 1930 proposed that to conserve Tmax = Q Energy and Momentum another particle, with little or no interaction was required – The neutrino • Neutrinos have VERY small masses n p + e + e • Only left handed neutrinos interact -- very “I am embarrassed that I have weakly proposed a particle that can • 3-generations of never be seen” neutrinos – Lepton number is conserved Feb 25, 2008 E. V. Hungerford University of Houston 3 U H M E P What about the Neutrino? • Neutrinos – Dirac, Majorana? • What are the neutrino masses ? • What is the neutrino mass hierarchy ? • Is CP violated in the neutrino sector ? • Are there additional neutrino types, e.g. sterile and non- SM neutrinos? • What are the mixing angles (in particular 13 )? • How do neutrinos affect the evolution of our universe? Feb 25, 2008 E. V. Hungerford University of Houston 4 U H M E P How do neutrinos affect the evolution of our universe? In Contradiction to Newton’s Concept of the “Fixed Stars” our Universe has, and now is, EVOLVING Neutrinos and the weak interaction are believed to be SUPERNOVA crucial in the Core-collapse Type II Supernovae – How does • Dominant contributor to Galactic this happen? nucleosynthesis • Occurs in the collapse of the iron core of a massive star - 8-10 Solar mass • Extremely energetic explosion 1053 ergs of energy released 99% in neutrino emission SN 1987A Brightest SN in • A few per century in our Galaxy (last SN 400 yrs ago) 400 yrs Feb 25, 2008 160,000 LY awayE. V. Hungerford University of Houston 5 U H M E Neutrino Emission from P Supernovae Matter Gains Energy From Neutrinos Shock Matter Loses Gravitational Energy to Neutrinos Feb 25, 2008 E. V. Hungerford University of Houston 6 U H M E P Convective Model and Neutrino Heating Feb 25, 2008 E. V. Hungerford University of Houston 7 U H M From: Adam Burrows E www.astro.princeton.edu~/ P 2-D Model of Core Collapse burrows 15 Solar Masses •0.0 < t < 0.318s Feb 25, 2008 E. V. Hungerford University of Houston 8 U H M E P Neutrino Emission From: Adam Burrows www.astro.princeton.edu~/ burrows 15 Solar Masses •0.0 < t < 0.318s Feb 25, 2008 E. V. Hungerford University of Houston 9 U H M E P Neutrino reactions and nucleosynthesis •Neutrino reactions with nuclei ahead of the shock -nucleus cross sections alter the entropy & composition of the infall are important for [Bruenn & Haxton (1991)]. understanding the supernova explosion •Neutrino reactions alter the elemental distribution mechanism and for in the ejected material - Cross sections are important nucleosynthesis for interpreting observations in metal-poor stars [Fröhlich et al., astro-ph/0410208 (2005)]. •Neutrino energy transport reheats the shock. The model has a hot dense core of neutrons surrounded by a shell of alpha and neutrons surrounded by a shell of Fe and Ni, surrounded by consecutive shells of lighter elements. Explosion ejects outer shells.[Ann Rev 27(77)167] Feb 25, 2008 E. V. Hungerford University of Houston 10 U H M E P Electron capture and Core collapse • Electron capture and the charged-current The weak interaction plays a e reaction are governed by the same crucial role in establishing the nuclear matrix element. Electron capture dynamics of the supernova changes protons into neutrons shock wave - e + A(Z,N) A(Z-1,N+1) + e Iron core mass and - • To Calculate rates we need neutronization depend on e • Gamow-Teller strength distributions capture and beta decay rates for A<65 • First-forbidden contribution • gA /gV modifications by nuclear medium, etc Electron capture producing e on heavy nuclei remains • New calculations using a hybrid model of important throughout collapse. Shell Model Monte Carlo (SMMC) and RPA predict significantly higher rates for N>40 and supernovae shock starts deeper Neutrino Transports energy and weaker from the core to the outer shell Feb 25, 2008 E. V. Hungerford University of Houston 11 U H M E P Supernovae and Nucleosynthesis 126 Input The landscape and the models 82 • masses • weak decay properties rp process • neutrino interactions 50 • thermal properties protons 82 28 8 50 2 28 neutrons 2 8 A convolution of nuclear structure, nuclear astrophysics, weak interactions Ab initio few-body calculations Feb 25, 2008 E. V. Hungerford University of Houston 12 U H M E B. S. Mayer P A Simulation of Neutrino www.astro.princeton.edu/~ Nucleosynthesis burrows Nucleosynthesis for a Shock passing through 28Si Feb 25, 2008 E. V. Hungerford University of Houston 13 U H M E Neutrino-nuclear P cross-sections Charged Current Feb 25, 2008 E. V. Hungerford University of Houston 14 U H M E Neutrino-nuclear P cross-sections Neutral Current Coherent (Elastic) Magnetic Moment Feb 25, 2008 E. V. Hungerford University of Houston 15 U H M E Neutrino-nuclear P cross-sections • Both cross sections are needed for supernova modeling - a few % accuracy is required • Radiative corrections and in-mediun effects (rescaling ga/gv, correlations,, etc ) are required for CC • Only the CC cross section in C is reasonably well-measured (10%). • Coherent NC-nuclear has not been observed • Needed for the calibration of astrophysical neutrino detectors (Low Energy) Feb 25, 2008 E. V. Hungerford University of Houston 16 U H M E P Basic Interaction Z 1, A l Z, A Charged current: Z 1, A l * Neutral current: Z, A (Z, A ) All reactions are possible f l, l as long as they obey selection rules i Neutral current T+1 l T+1 T=1 N Z T T T=1 2 T T+1 N Z M T T 2 MT = -T-1 T=1 T-1 Charged current T T=0 MT = -T+1 MT = -T T=1 (T>=1/2) Charged current Feb 25, 2008 E. V. Hungerford University of Houston 17 U H M E 12 P C Example 1+,T=0 12.71 MeV Qb 16.32 MeV , b+ -,b- e Qb= 13.37 MeV Feb 25, 2008 E. V. Hungerford University of Houston 18 U H M E P Neutrino-Fe CC Cross section 1- GT 2- Fermi (IA) Allowed Feb 25, 2008 E. V. Hungerford University of Houston 19 U H M E P CRPA angular distribution e θ 16F Feb 25, 2008 E. V. Hungerford University of Houston 20 U H M E P Neutral Current Reactions Coherent Scattering from Nuclei 35 MeV For Coherent Scattering qR ≤ 1 All Flavors Participate Cross Section ~A2 Signature is a x 10 of CC value VERY low energy Nuclear Recoil Feb 25, 2008 E. V. Hungerford University of Houston 21 U H M E P The Oak Ridge Spallation Neutron Source CLEAR Feb 25, 2008 E. V. Hungerford University of Houston 22 U H M E P SNS Parameters •Primary proton beam energy - 1.3 GeV •Intensity - 9.6 1015 protons/sec •Number of protons on the target 0.687x1016 s-1 (1.1 ma) •Pulse duration - 380ns(FWHM) •Repetition rate - 60Hz •Total power – 1.4 MW •Liquid Mercury target • 0.13 neutrinos of each flavor produced by one proton (9 x 1014 s-1) •Number of neutrinos produced ~ 1.91022/year •There is a larger flux of ~MeV anti-neutrinos from radioactive decay from the target Feb 25, 2008 E. V. Hungerford University of Houston 23 U H M E P Stopped pion decay Produces s with the same energy range as supernovae KARMEN at ISIS (RAL) 65 tons of liquid Scintillator 100 events/year LSND at Los Alamos + C, = (81) x 10-42 cm2 +Fe (~40%) 12C [Auerbach et al. (2001)] +Iodine (40%) [Distel et al. (2003)] Feb 25, 2008 E. V. Hungerford University of Houston 24 U H M E Neutrinos from Stopped P π and μ decay Neutrinos from Stopped Time Structure of neutrinos Pion Facilities From the SNS + + π → μ + ν μ + + μ → e + ν μ + νe Feb 25, 2008 E. V. Hungerford University of Houston 25 U H M E P Motivation for -SNS Neutrinos from Supernovae e Important Energy Window e e •Just right for supernovae studies _ _ •High Neutrino Flux •SN detector calibration •Almost no data Neutrinos from Stopped Pion Facilities Extremely high neutrino flux • Potential for precision measurements • Can address a number of new physics issues • Nuclear Physics processes • Can begin with small detectors Feb 25, 2008 E. V. Hungerford University of Houston 26 U H M E P Comparison of SNS with other stopped pion facilities Facility LANSCE ISIS SNS SNS Advantage Beam energy 0.8 GeV 0.8 GeV 1.3 GeV 1.7 Beam current 1.0 mA 0.2 mA 1.1 mA (0.8MW) (0.16MW) (1.4 MW) 1.75 Coulomb delivered 6500 2370 22000 3 per year to the (LSND) (KARMEN) target Beam structure Continuous Two 200 nsec 380 nsec Separation bunches separated FWHM from e, by 300 nsec pulses at 60 better BG repetition rate - 50 Hz suppression Hz Target Various Water cooled Mercury Source Tantalum compactness Feb 25, 2008 E.
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