Constraints on Neutrino Electromagnetic Properties via Atomic Ionizations with Germanium Detectors at sub-kev Sensitivities

Transcription

1 Constraints on Neutrino Electromagnetic Properties via Atomic Ionizations with Germanium Detectors at sub-kev Sensitivities Chih-Pan Wu National Taiwan University Collaborators: Jiunn-Wei Chen, Chih-Liang Wu (NTU) Chen-Pang Liu, Hsin-Chang Chi (NDHU) Henry T. Wong, Lakhwinder Singh (AS & TEXONO) 1

2 How neutrino EM properties play an important role? nonzero millicharge exists anomalous magnetic moment exists Finite neutrino masses and mixings Chirality Charge quantization Dirac or Majorana CP phase n i W l g n j 2

3 3 TEXONO Kuo-Sheng Nuclear Power Station in Taiwan Neutrino Magnetic Moment Neutrino Millicharge

4 ν Ge Atomic Ionization (AI) 4

5 Atomic effects are important at sub-kev sensitivities 5

6 Ab initio Method for AI Free Electron Approx. (FEA) Equivalent Photon Approx. (EPA) 4-momentum transferred for fixed T in ν Ge AI: 6

7 Ab initio MCRRPA Theory for Atomic Ionization MCRRPA: multiconfiguration relativistic random phase approximation Hartree-Fock : RPA: RRPA: MCRRPA: Solve self consistently by reducing the N-body system to single-particle problem by effective mean field Include 2 particle 2 hole excitation D. Bohm and D. Pines (1952) Describe heavy noble gas (Dirac Eq.) W.R. Johnson, C.D. Lin and A. Dalgarno (1976) More than one configuration. Important for open shell system, where energy gap < closed shell K.-N. Huang and W.R. Johnson (1982) 7

8 H ( t) H V( t) One-electron Hamiltonian + Atomic Coulomb interaction Time-dependent interaction it it V ( t) [ n ( r ) e n ( r ) e ] I i i u a ( r, t) (t) is a Slater determinant of one-electron orbitals and invoke variational principle ( t) i H VI ( t) ( t) 0 t to obtain equations for u a ( r, t). RPA: Expand u a ( r, t) i t a i t i t u ( r, t) e [ u ( r) w ( r) e w ( r) e...] a into time-indep. orbitals in power of external potential a a a i MCRRPA: Approximate the many-body wave function (t) by a superposition of configuration functions (t) ( t) C ( t) ( t) 8

9 Atomic Structure of Ge For J=1, λ=1 Selection Rules: Angular Momentum Selection Rule: Parity Selection Rule: 9

10 Benchmark: Ge Photoionization Exp. data: Ge solid Theory: Ge atom (gas) Above 100 ev error under 5%. 10

11 Numerical Results: Weak Interaction Ev e 1MeV Ev e 10 kev cutoff : T Max E 2E v e 2 v e m e 0.38 kev High E ν & T, ours agreed with FEA. 11

12 Numerical Results: NMM Ev e 10 kev Ev e 1MeV EPA failed at High E ν. Ours is ~50% smaller than FEA at sub-kev. 12

13 Numerical Results: Millicharge Ev e 10 kev Ev e 1MeV mv e 0.2 ev EPA worked well due to kinematic factors of F 1 form factor receive a strong weight at peripheral scattering angles. 13

14 Experimental Limit Neutrino Magnetic Moment (NMM) Neutrino Millicharge 14

15 Summary Ab initio calculation of atomic ionization (AI) is important for Neutrino Detector threshold extend to sub-kev regime. - FEA works well only for both incident neutrino energy & transferred energy are much higher than atomic scale. - EPA works well when the forward scattering are dominated (Q 0), like F 1 form factor. Comparison with experimental data can set an upper-bound for neutrino EM properties. 15

16 Outlook Propose to Other Usages: Ge atomic ionization for light dark matter direct detection and others Detector Improvement: Solid effect - motivates even lower threshold Ge & Si detectors Other Detectors: Xe & Ar atomic ionization 16

17 Reference: J.-W. Chen et al., Phys. Lett. B 731, 159 (2014). J.-W. Chen, C.-P. Liu, C.-F. Liu, and C.-L. Wu, Phys. Rev. D 88, (2013). C. Giunti and A. Studenikin, arxiv: (2014). P. Vogel and J. Engel, Phys. Rev. D 39, 3378 (1989). K.-N. Huang and W. R. Johnson, Phys. Rev. A 25, 634 (1982). [MCRRPA Theory] J. Beringer et al., Phys. Rev. D 86, (2012). [PDG] H. T. Wong et al., Phys. Rev. D 75, (2007). [TEXONO] A. G. Beda et al., Phys. Part. Nucl. Lett. 10, 139 (2013). [GEMMA] H.-B. Li et al., Phys. Rev. Lett. 110, (2013). [TEXONO-PPCGe] B. L. Henke, E.M. Gullikson, and J.C. Davis, At. Data Nucl. Data Tables 54, 181 (1993). Thanks for your attention! 17

18 BACKUP SLIDES 18

19 Neutrino Intensity Spectrum Spectra shape for reactor neutrino due to individual production channel Total spectrum at the typical power reactor operation of Kuo-Sheng Nuclear Power Station 19

20 Two Approximations --- I Equivalent Photon Approx. 20

21 Two Approximations --- II Free Electron Approx. 21

22 Toy: ν-h atomic ionization, exact result obtained Equivalent Photon Approx. binding momentum of hydrogen: αm e Free Electron Approx. 22

23 ν Ge Kinematic Function 23

24 ν Ge Response Function 24