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Searching for an underground national lab in China

Searching for an underground national lab in China. Yifang Wang July 23, 2008. Motivation for an underground lab. Particle physics Double beta decays Nucleon decays Atmospheric/solar neutrinos Reactor neutrinos Long baseline neutrino oscillations Cosmic-rays ….. Gravitational waves

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Searching for an underground national lab in China

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  1. Searching for an underground national lab in China Yifang Wang July 23, 2008

  2. Motivation for an underground lab • Particle physics • Double beta decays • Nucleon decays • Atmospheric/solar neutrinos • Reactor neutrinos • Long baseline neutrino oscillations • Cosmic-rays • ….. • Gravitational waves • Environment • Geology • …

  3. A few ideas discussed in the community • Very long baseline neutrino oscillation • Beams from J-PARC to Beijing, L~ 2000 km • A (0.1-1.0)Mt water Cerenkov Detector • Very very long baseline neutrino oscillation • Beams from Fermilab to Beijing • Gravitational waves • Dark matters

  4. Measure CP, sin22q13 and Dm223 sign— very long baseline experiment

  5. J-PARC to BeijingL=2100 km, 1300 events/100kt-Yr

  6. Study of density effects: Lian-You Shan et al., Phys. Rev. D 68 (2003) 013002

  7. A typical nm CC event

  8. 1m*1m*13m尺寸的水箱模型

  9. A candidate underground lab • An aviation museum near Beijing • Total Volume: 250K m3 • Overburden: 150 m Good enough for accelerator based neutrino experiments but not deep enough for a general purpose low background underground lab.

  10. Requirements for a general purpose underground lab • Overburden > 1000 MWE • Size of the underground lab > (0.1-1.0) Mt • Rock quality: good easy construction • Tunnel length: short enough to have acceptable cost • Traffic: easy enough • Logistics: obvious

  11. Possibilities and (failed) experience • Existing underground, abandoned military facilities: for its good infrastructure, usually large underground halls • Next to traffic tunnels: to save money of tunneling, similar to that of Gran Sasso • Brand new underground experimental halls

  12. Change the direction: look at physics opportunities first • Double beta decays • Nucleon decays • Atmospheric/solar neutrinos • Reactor neutrinos: CP, theta_13, mass hierarchy • Long baseline neutrino oscillations • Cosmic-rays • ….. • Gravitational waves

  13. Neutrino mass hierarchy • Three unknowns in neutrino oscillation: • 1. delta-CP phase • 2. theta13 value • 3. mass hierarchy 2008-07-17 14

  14. Principle L/E spectrum E spectrum EL/E Three lines, one is for 1 – P21 oscillation, the other two are Pee oscillation with NH and IH. difficult to discriminate using L/E spectrum 2008-07-17 15

  15. First attempt: power spectrum of Fourier transform • Conclusion: need Sin2(2q13) > 0.02 • J. Learned et al., HEP-ex/0612022

  16. Fourier transform L. Zhan et al., hep-ex/0807.3203 • t = L/E, F(L/E) is neutrino spectrum in L/E space. • Pee is a periodic function in L/E space with oscillation frequency proportional to • In the range the P31 and P32 component is distinctive in the FCT and FST spectrum. 2008-07-17 17

  17. FCT and FST spectrum Baseline = 60 km Best fit neutrino mixing paras • Distinctive features: • 1 – P21 is weak • P31 and P32 • Symmetric P31 and P32 are broken in Pee • FCT: • NH: peak before valley • IH: valley before peak • FST: • NH: prominent peak • IH: prominent valley 2008-07-17 18

  18. Quantify Features of FCT and FST • To quantify the symmetry breaking, we define: RV and LV: the amplitude of the right and left valley in FCT spectrum. P and V: the amplitude of the peak and valley in FST spectrum. • For symmetric P31 and P32 RL = 0, PV = 0 • For asymmetric Pee • NH: RL>0 and PV>0 • IH: RL<0 and PV<0 2008-07-17 19

  19. Baseline and theta13 Baseline: 46-72 km Sin2(2q13): 0.005-0.05 Other mixing parameters from global fit Two clusters of RL and PV values show the sensitivity of mass hierarchy determination. 2008-07-17 20

  20. Limit of sin2(2q13) Clear distinctive features Better than power spectrum 2008-07-17 21

  21. Best location: Daya Bay • Th. power: 12 GW ~ now, 18 GW ~ 2010, 24 GW ~ 2015

  22. Detector: Huizhou - Baiyunzhang Altitude: ~ 1000 m, highest in Dongguan/Huizhou

  23. 1.6 km tunnel

  24. A promising underground lab • Ideal location for a (1-10)kt reactor neutrino experiment: • Mass hierarchy • Precision q12 measurement • Supernova neutrinos • Geoneutrinos • Sterile neutrinos • …. • Enough overburden as a generic underground national lab for many other applications • A detailed study and detector design will be carried out in the next few months

  25. Summary • Searches Starting from a generic underground lab not successful in the past • JPARC-Beijing long baseline exp. uncertain • A neutral continuation of Daya Bay: • Using Daya Bay as the world largest reactor complex as the neutrino source • Using current Daya Bay exp. as the near detector • Construct a generic underground lab at Baiyunzhang • Construct an (1-10) kt electron antineutrino detector A bright future of particle physics in China

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