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Low Energy Neutrinos- Oscillometry and Coherent Elastic Scattering

Low Energy Neutrinos- Oscillometry and Coherent Elastic Scattering. J.D. Vergados University of Ioannina Greece. Main Topics. A future neutrino oscillation experiment ( including the measurement of θ 13 ) Neutrino detection via Neutral current interactions with spherical TPC detectors

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Low Energy Neutrinos- Oscillometry and Coherent Elastic Scattering

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  1. Low Energy Neutrinos-Oscillometry and Coherent Elastic Scattering • J.D. VergadosUniversity of IoanninaGreece 4th Symposiun on large TPC's Paris18-19/12/08

  2. Main Topics • A future neutrino oscillation experiment (including the measurement of θ13) • Neutrino detection via Neutral current interactions with spherical TPC detectors -Tests with neutrinos from SNS (neutron spallation source) - Neutrinos in Astrophysics (supernova detection) • Fancy neutrino beams with prescribed CP composition 4th Symposiun on large TPC's Paris18-19/12/08

  3. NOSTOS: SPHERICAL TPC’s for detecting Earth or sky neutrinos • A) LOW ENERGY “NEUTRINOS IN A SPHERICAL BOX”(electron recoilsfrom low energy neutrinos) • B)A Network ofNeutral Current Spherical TPC’sfor DedicatedSUPERNOVA NEUTRINO DETECTION AND OTHER APPLICATIONS (nuclear recoils – coherent neutral current interaction) 4th Symposiun on large TPC's Paris18-19/12/08

  4. Main Features Of NESTOS A(Low energy neutrino sources: triton decay or electron capture targets) • Very low energy neutrinos  small oscillation lengths • Thefull oscillationtakes place inside the detector (many standard experiments simultaneously) • νe disappearance experiment • νμ + ντ“appearance” experiment (indirect) 4th Symposiun on large TPC's Paris18-19/12/08

  5. Standard Neutrino Oscillation ExperimentsEffectively analyzed as two generations • Appearance P(να-> νβ, α≠β)=sin22θsin2 π(L/L0) • Disappearance P(να-> να)=1-sin22θsin2 π(L/L0) • θ is the “effective” mixing angle • L0 the oscillation Length =(4πEν)/Δm2 or L0=2.476km {Eν/1MeV}/{Δm2 /10-3eV2}= 2.476m {Eν/1keV}/{Δm2 /10-3eV2} • L is the source detector distance 4th Symposiun on large TPC's Paris18-19/12/08

  6. Table I: Best fit values from global data(solar, atmospheric, reactor (KamLAND and CHOOZE) and K2K experiments)Also recently : Pascoli & Petcov arXiv0711.4993Schwetz & Valle arXiv: 0808.2016 4th Symposiun on large TPC's Paris18-19/12/08

  7. Electron Neutrino disappearance P(νe ->νe) 4th Symposiun on large TPC's Paris18-19/12/08

  8. with L31=L32 -L21. If s13<<1 we get 4th Symposiun on large TPC's Paris18-19/12/08

  9. Two oscillations for a triton source: L32 =6.5 m L21= 50L32 4th Symposiun on large TPC's Paris18-19/12/08

  10. both oscillations; triton source; L32=6.5 m, L21 =50L32 4th Symposiun on large TPC's Paris18-19/12/08

  11. The NOSTOS PROPOSAL: L32 =6.5 m (Triton Neutrinos, Spherical TPC, Electron Scattering) 4th Symposiun on large TPC's Paris18-19/12/08

  12. The charged current (top) and the neutral current (bottom) cross section as a function of Te/Eν. (Dotted neutrino, Continuous  antineutrino) 4th Symposiun on large TPC's Paris18-19/12/08

  13. In α(νe ,e) detector all flavors produce electrons, with rates depending on the electron energy Te: R(νe->νe)/≈{1- sin2 (2θ21) sin2 [π(L\L21)] -sin2 (2θ13) sin2 [π(L\L23)]}{σ(νe,Τe)/ σ(νe,0)} • R(νe-> να,να=νμ or ντ)≈ { sin2 (2θ12) sin2 [π(L\L21)]+ sin2 (2θ13) sin2 [π(L\L32)]} {σ(να,Τe)/ σ(νe,0)} • Thus the effective oscillation probabilities: • P(νe->νe)= R(νe->νe)/ {σ(νe,Τe)/ σ(νe,0)} • Will appear as: • P(νe->νe)≈ 1- χ(Εν,Τe) { sin2 (2θ12) sin2 [π(L\L21)] +sin2 (2θ13) sin2 [π(L\L32)]} 4th Symposiun on large TPC's Paris18-19/12/08

  14. Effective oscillation Probability vs L for Εν=60 keV ,Te=2keVand sin2 (2θ13) =0.170, 0.085, 0.045(Dotted Antineutrino, continuous neutrino) 4th Symposiun on large TPC's Paris18-19/12/08

  15. Effective oscillation Probability vs L for L for Εν=60 keV, Te=10 keV and sin2 (2θ13) =0.170, 0.085, 0.045(Dotted Antineutrino, continuous neutrino) 4th Symposiun on large TPC's Paris18-19/12/08

  16. The differential cross section must be averaged over the neutrino spectrum: 4th Symposiun on large TPC's Paris18-19/12/08

  17. The differential cross section dσ/dTein units of 510-52 m2/keV for sin2 (2θ13)= 0.085 and Te=0.2,0.4,0.6,0.8,1.0,1.2 keV 4th Symposiun on large TPC's Paris18-19/12/08

  18. The event rate.Source 20 Kg of tritium.Detector: Ar at 10 Atm. (Must be multiplied by (1-Exp[-t/τ]) to get # of events in time t) 4th Symposiun on large TPC's Paris18-19/12/08

  19. NOSTOS PROPOSAL: L32 =6.5 m (Triton Neutrinos, Spherical TPC, Electron Scattering)sin22θ13=0.170 (left); sin22θ13=0.085 (right) 4th Symposiun on large TPC's Paris18-19/12/08

  20. Schematic View of the NOSTOS DetectorGood resolution & Low threshold (<100eV) 4th Symposiun on large TPC's Paris18-19/12/08

  21. Other low energy neutrino sources • Difficult to accumulate 20 kg (220 MCurie) of triton. • Other very low energy neutrino sources may have to be considered • Electron capture monochromatic sources are preferred. • One needs: 1. A nucleus living long enough for the experiment to be done. 2. A compromise regarding the neutrino energy: -Sufficiently high to yield enough events -Not too high to yield small neutrino oscillation lengths • Such candidates can be found. 4th Symposiun on large TPC's Paris18-19/12/08

  22. Some sources of low energyMono-energetic Neutrinos (Y. Giomataris, N. Novikov, JDV)One may employ Strow-method with Length>10m • Some candidates are: • A=157 (Tb), T1/2 = 70 y, Eν=9.8keV,L0=4.9 m • A=163 (Ho), T1/2 =4500, Eν =0.5-2.6keV, L0=0.3-1.6 m • A=193 (Pt), T1/2 =56.8y,Eν =43.8 keV, L0=21 m • A=178 (W), T1/2=21.6d, Eν =24 keV, L0=12 m • A=194 (Hg), T1/2 =440y, Eν =55keV, L0=27 m • Α=202 (Pb), T1/2 =5x104 y, Eν =35 keV, L0=17 m 4th Symposiun on large TPC's Paris18-19/12/08

  23. The oscillation profile for various targets 4th Symposiun on large TPC's Paris18-19/12/08

  24. The difer. rate dR/((dL/1m)(dT/1keV)) (to be multiplied by 1-Exp[t/τ]) A=193 (Pt), Te =1eV A=193 (Pt), Te =2.5 keV 4th Symposiun on large TPC's Paris18-19/12/08

  25. Conclusions on NOSTOS A Very low energy neutrinos: • They will soon be oscillating in a spherical box. They may measure or yield a better limit on θ13 • They will improve the limit on the neutrino magnetic moment by at least two orders of magnitude. • They will measure the Weinberg angle at very low momentum transfers (the analysis is much simpler than that of the atomic experiments) • Detect low energy solar neutrinos (pp & 7 Be) 4th Symposiun on large TPC's Paris18-19/12/08

  26. NESTOS B: NUCLEAR RECOILS • ANetworkof Neutral Current Spherical TPC’s for Dedicated SUPERNOVA NEUTRINODETECTION 4th Symposiun on large TPC's Paris18-19/12/08

  27. Why Neutrinos? Neutrinos: • Travel large distances with the speed of light (with light one cannot observe further than 50 Mpc (1Mpc=3.3x106light years)) • They can pass through obstacles • They do not get distorted on the way • They are not affected by magnetic fields • They are not affected by oscillations; So they reveal information about the source interior 4th Symposiun on large TPC's Paris18-19/12/08

  28. Prototype Supernova in our galaxy • Distance: D=10 kpc=3.1x1022cm • Duration: 10 s • Energy Output :Almost all gravitational energy goes into the neutrinos Eν =1.5x1053 erg (mSN/msun)2 (10km/RSN) • Typical value: 3x1053ergs • A few SN per century expected 4th Symposiun on large TPC's Paris18-19/12/08

  29. Assumptions about the Neutrino Content of Supernova explosion • 3 Neutrino Flavors carrying 0.5x1053 ergs each • Each flavor is characterized by its flux, which is a distribution times its cross section • The distribution is taken as Fermi-Dirac distribution (with zero chemical potential) The characteristic temperatures are: T=8 MeV (for μ and τ neutrinos and antineutrinos) T=3.5 MeV for νeand 5 MeV for anti-νe 4th Symposiun on large TPC's Paris18-19/12/08

  30. Simple Neutrino Spectrum The short dash: νe; The long dash: anti- νe; Continuous curve: all other flavors 4th Symposiun on large TPC's Paris18-19/12/08

  31. Advantages of a Neutral Current Detector • All neutrinos contribute • The event rate is not affected by neutrino oscillations • Idealprobe for the neutrino source • The target proton contribution is negligible, but all neutrons contribute • The rate is proportional to N2 4th Symposiun on large TPC's Paris18-19/12/08

  32. The prototype at SACLAY 4th Symposiun on large TPC's Paris18-19/12/08

  33. For an average neutrino energy of ~34 MeV…. • The average nuclear recoil energy is: He Ne ArKrXe <Er>: 0.576 0.117 0.0580.0290.017 MeV • The threshold neutrino energy (for nuclear recoil energy Eth=250 eV) is He Ne ArKrXe (Eν)th 0.70 1.58 2.243.164.05 MeV 4th Symposiun on large TPC's Paris18-19/12/08

  34. The dif. event rate forXe(arbitrary units).Including the Nuclear Form Factor(20% effect mainly at high energies) • The short dash: νe; The long dash: anti- νe; Continuous curve: all other flavors 4th Symposiun on large TPC's Paris18-19/12/08

  35. Expected total number of events • For p=10 Atm, R=4m, D=10 kpc, Uν =0.5x1053 ergs • #of events (no quenching, zero threshold) He Ne Ar KrXeXe (with Nuc. F.F) 1.25 31.6 1536141880 1435 • Quenching factor He Ne Ar Kr Xe 0.29 0.31 0.35 0.38 0.49 • # of events (after quenching, Eth =0.1 keV) He Ne ArKr XeXe (with Nuc. F.F) 0.61 12.0 53.5190545 415 4th Symposiun on large TPC's Paris18-19/12/08

  36. A possible test for the detector efficiency: The Oak Ridge Spallation Neutron Source (SNS).(Giomataris, Avignone & JDV) • # π+ : 6 1014 per second • N(νμ)=6 1014 per second (discreet) • N(νe)=N(νμ-bar) =6 1014 per second (continuous) 4th Symposiun on large TPC's Paris18-19/12/08

  37. The ORNL spectrum:Discreetνμ,continuous anti- νμ, dashed  νe 4th Symposiun on large TPC's Paris18-19/12/08

  38. The dif. event Rate 131Xe(solid<->No FF) Thick vertical bar <-> quenching νe (top) αντι-νμ (bottom) Discreet νμ Thick vertical bar <->quenching 4th Symposiun on large TPC's Paris18-19/12/08

  39. The dif. event Rate 40Ar(solid<->No FF) Thick vertical bar <-> quenching νe (top) αντι-νμ (bottom) Discreet νμ Thick vertical bar <->quenching 4th Symposiun on large TPC's Paris18-19/12/08

  40. Optimum total cross sections (Ethr=0)in units of 10-41 cm2 for131Xe and 40Ar 4th Symposiun on large TPC's Paris18-19/12/08

  41. The dependence of cross section on Ethrσ(Ethr)/σ(Ethr=0) vsEthrfor 131Xe Lower two curves <-> quenching νe (top) αντι-νμ (bottom) Lower two curves <-> quenching Discreet νμ 4th Symposiun on large TPC's Paris18-19/12/08

  42. The dependence of cross section on Ethrσ(Ethr)/σ(Ethr=0) vsEthrfor 40Ar Lower two curves <-> quenching νe (top) αντι-νμ (bottom) Lower two curves <-> quenching Discreet νμ 4th Symposiun on large TPC's Paris18-19/12/08

  43. The event rate per ton per year at a distance of 50 m from the source for Eth=0 4th Symposiun on large TPC's Paris18-19/12/08

  44. The number of events in one year for the spherical TPC detector: P=10 Atm, R=10 m, T=3000K, L=50 m 4th Symposiun on large TPC's Paris18-19/12/08

  45. The dependence on the Geometry 4th Symposiun on large TPC's Paris18-19/12/08

  46. Concluding remarks THE NOSTOS Collaboration intends to: • Use the Spallation Neutron Source (SNS) at Oak Ridge to test the coherent neutral current detector. • Build a low cost, robust and easily maintainable gaseous TPC detector Design it so it can be easily maintained (even by students) • Utilize a rich neutron target to exploit the coherence due to the neutral current. More than 500 events are expected in SN explosion in our galaxy. Note: • No need to go underground. Just 100 m underwater to maintain the high pressure • Aclusterof such detectors could localize SN 4th Symposiun on large TPC's Paris18-19/12/08

  47. FANCY NEUTRINO BEAMS • Low energy sources • Boosting the neutrino source  high energy ν’s 4th Symposiun on large TPC's Paris18-19/12/08

  48. Fancy Neutrino Beams with prescribed neutrino and antineutrino composition • Electron capture leads to mono-energetic electron neutrinos (ec). • Bound beta decay (bβ)leads to mono-energetic electron antineutrinos* with reasonable probability (mirror process of ec) as predicted by Bahcall in 1961 Confirmed experimentally in 1992. • Atoms normally electron capturing, if stripped of their electrons except for one in 1s orbit, can both beta decay (bβ,cβ)and ec • * Important also in s-processes in astrophysics (competing with low Q traditional beta decays) 4th Symposiun on large TPC's Paris18-19/12/08

  49. An Example (A. Fukumi et al; M. Jung et al PRL 69 (1992) 2164 ) 4th Symposiun on large TPC's Paris18-19/12/08

  50. Neutrino CP even-ness of the beam(it is both detector and energy dependent) • Consider the oscillations: νeνμ anti- νeanti-νμ detected via charged current reactions. Thus The CP even-nessη is defined as follows: • η=( 1-2):( 1+2) with • 1=Φ(νe)σ(νeνμ) • 2=Φ(anti-νe)σ(anti- νeαντι-νμ)  • It can be made close to zero by adjusting the energy when boosting the ion to high energy, e.g. γ=200 • For 100Ag46+ η=0.32.The large cβ (continuum)contribution can be exploited to make η≈0, by a judicious choice of the target* (e.g. Fe) . • * For most targets the charged neutrino cross section is much bigger than that for antineutrino 4th Symposiun on large TPC's Paris18-19/12/08

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