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Neutrino spectral calculations at the Daya Bay detectors and Relations between neutrinos and CPT violations. Ho Ling Li Mentor: Karsten Heeger Department of Physics December 3, 2008. What is neutrino oscillation?.

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slide1

Neutrino spectral calculations at the Daya Bay detectorsandRelations between neutrinos and CPT violations

Ho Ling Li

Mentor: Karsten Heeger

Department of Physics

December 3, 2008

slide2

What is neutrino oscillation?

  • Neutrinos have three different types (flavors): νe, νμ, ντ, and different masses
  • Quantum mechanics predicts change of flavors when neutrinos travel in space
  • Oscillation equation (probability of appearance):

parameter that we want to measure (GOAL!)

(difference of mass)2

Units: [Δm2] = eV2; [L] = m; [E] = MeV

distance (L)

energy

Ho Ling Li

Univ. Wisconsin

Dec 3, 2008

slide3

The Daya Bay Reactor Neutrino Experiment – an introduction

  • Located in Guangdong province of China
  • Study neutrino oscillation by using the electron antineutrinos released during the fission process at Daya Bay Nuclear Power Plant and Lingao Nuclear Power Plant
  • Aim to make a precise measurement of the neutrino mixing angle θ13 with a sensitivity of 0.01 in sin2(2θ13) by measuring the flux and spectrum of electron antineutrinos

Ho Ling Li

Univ. Wisconsin

Dec 3, 2008

slide4

Goals of my research

  • Calculate the predicted spectrum of antineutrinos at the three detector sites of the Daya Bay experiment
  • Study and compare the spectral distortions due to fuel compositions and neutrino oscillation

Ho Ling Li

Univ. Wisconsin

Dec 3, 2008

slide5

Step 1: fuel composition and variation of Daya Bay Reactors

  • Fresh fuel composed of 3.2% 235U and 96.8% 238U
  • Fuel composition changes throughout the fission process and Pu isotopes are produced
  • 235U, 238U, 239Pu, 241Pu are the four main isotopes that undergo fissions and produce anti-νe

http://whyfiles.org/186ed_teller/images/fission_anim.gif

Ho Ling Li

Univ. Wisconsin

Dec 3, 2008

slide6

Step 2: the antineutrino spectra from fuel isotopes

  • data obtained from: Vogel, P., G.K. Schenter, F.M. Mann, R.E. Schenter. Reactor antineutrino spectra and their application to antineutrino-induced reactions II. Physical Review C, 24, 1543 (1981).

Pu-241

U-238

U-235

# of antineutrinos / cm2 / s

Pu-239

antineutrino energy (MeV)

Ho Ling Li

Univ. Wisconsin

Dec 3, 2008

slide7

Step 3: calculate the antineutrino spectra at a reactor

capacity × (3.125 × 1016 fissions/second/Mwatt)

The ratios of electron antineutrinos produced by the isotopes concerned

The capacities of the reactors at Daya Bay

The number of fissions of each isotope per second in different reactor cores

Ho Ling Li

Univ. Wisconsin

Dec 3, 2008

slide8

Step 4 & 5: calculate predicted spectra at detectors

# of neutrinos

antineutrino energy (MeV)

2.5 x 10-3eV2

assume sin2(2θ13) = 0.1

Units: [Δm2] = eV2; [L] = m; [E] = MeV

the only variable in the spectra

Ho Ling Li

Univ. Wisconsin

Dec 3, 2008

slide9

Step 4 & 5: calculate predicted spectra at detectors

  • at Daya Bay Near Detectors

spent (with oscillation)

fresh (without oscillation)

fresh (with oscillation)

spent (without oscillation)

Ho Ling Li

Univ. Wisconsin

Dec 3, 2008

slide10

spent (without oscillation)

spent (with oscillation)

fresh (with oscillation)

fresh (without oscillation)

Step 4 & 5: calculate predicted spectra at detectors

  • at Far Detectors

Ho Ling Li

Univ. Wisconsin

Dec 3, 2008

slide11

Comparison of the Spent Fuel and Oscillation Spectra

Effect of Spent Fuel

Effect of Neutrino Oscillation

The difference between the normalized fresh fuel spectra with and without the signature of neutrino oscillation over the normalized fresh fuel spectra without the signature of neutrino oscillation at the Far Detector

The difference between the normalized spectra of the fresh fuel and the spent fuel over the normalized spectra of the fresh fuel

ratio

ratio

antineutrino energy (MeV)

antineutrino energy (MeV)

Ho Ling Li

Univ. Wisconsin

Dec 3, 2008

slide12

Conclusions

  • Both the variation of the fuel compositions and neutrino oscillation effects lead to spectral distortions
  • The way they change the spectral shapes is distinct
  • The neutrino oscillation angle can be measured independent of the fuel compositions

Ho Ling Li

Univ. Wisconsin

Dec 3, 2008

slide14

Relations between CPT violations and ν

  • When there is CPT violation…
  • Mixing angles and the mass difference ∆m of ν and νcan be different
  • 12≠ 12, 13 ≠ 13, 23 ≠ 23
  • ∆m12 ≠ ∆m12, ∆m13 ≠ ∆m13

Univ. Wisconsin

Dec 3, 2008

slide15

Past and Present Bounds

  • S. Antusch, E. Fernandez-Martinez (2004) get:
  • | sin212–sin212| < 0.3
  • Neutrino 08
  • | sin212 – sin212| < 0.3
  • No improvement…

Univ. Wisconsin

Dec 3, 2008

slide16

Comparison with best CPT bounds from K0, K0

  • |mK - mK| < 0.44 x 10-18 GeV
  • |mK - mK| / maverage< 10-18
  • 493 MeV < mK < 498 MeV
  • => |mK - mK| < 0.5 x 10-18 GeV
  • No improvement neither…

Barger, Pakvasa, Weiler, and Whisnant. (2000)

PDG. (2007)

Univ. Wisconsin

Dec 3, 2008

slide17

Requirements for CPT symmetry to hold

  • Lorentz invariance
  • Locality
    • If extra dimension exists, interactions that are local in extra dimension “look” non-local in our world brane
    • Therefore, Lorentz invariance holds, but there is CPT violation

5D

4D brane

Univ. Wisconsin

Dec 3, 2008

slide18

Lorentz violation in neutrinos?

  • P = 1 - 0.92 sin2(17.29 x / L0 + k*L0 / x), x = L0/E
  • tan2(12) = 0.56, ∆m2 = 7.58 x 10-5 eV2
  • k = 0.005, k = 0.01, k = 0.02, k = 0.04, k = 0.08

Univ. Wisconsin

July 1, 2008

slide19

Consequence of Lorentz invariance violation

  • mwill be frame dependent
  • However, if the Lorentz invariance is broken at very high energy scale (e.g. Planck scale), the corrections will be extremely small

(mc2)2 = E2 - (pc)2

Univ. Wisconsin

Dec 3, 2008