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Electron Recoil & Dark Matter Direct Detection

Electron Recoil & Dark Matter Direct Detection. Qing Wang Tsinghua Univ. Beijing. Background and Status of ER Our present understanding. Cosmology, Astrophysics Search DM particle physics. Cosmology & Astrophysics ： Found ！. Particle Physics ： Not Found ！.

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Electron Recoil & Dark Matter Direct Detection

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  1. ElectronRecoil &Dark Matter Direct Detection Qing WangTsinghua Univ. Beijing

  2. Background and Status of ER Our present understanding

  3. Cosmology,Astrophysics Search DM particle physics

  4. Cosmology & Astrophysics： Found ！

  5. Particle Physics：Not Found ！ No unambiguous evidence has been obtained to date ColliderExperiment Direct Detection IndirectDetection

  6. Nuclear Recoil&Electron Recoil

  7. Electron Recoilnot considered at very beginning !

  8. m，v0,vˊ EstimationofRecoil Energy M,v，v0ˊ Targetrecoil vtarget initial v0’DMinitial v0DMfinal v’ ForM>>m rest nucleon ER~2v02m2/M~ 2keV ×(m/10GeV)2×100GeV/M v0~10-3； for electron m>>M ER~2v02M~1eVChemistry & Biology Theory& Exp not preferelectronrecoil Angle between incident particle & target CM frame traditional threshold Lower detection bound m reduce from 10GeVto 1GeV，NR reduce from 2keVto 20eV，ER keep1eV ！ Too smallfor electron recoil energy

  9. 1st rise up ER energy~keV

  10. Bounded electron of NaI(Tl)has10-4 probabilityv2>1/2（p>0.5MeV） Sodiumiodide

  11. Theory& Exp not preferERagain ! Phys.Rev. D80 (2009) 083502 DAMA signal was explained as ERavoid contradiction with other exps Assume DM only interact with leptons leptophilic But Leptonsloop induce enough NR And electroncannot seen as free particle While CDMS analysis on ER spectrumgives no signal Phys.Rev. D81 (2010) 042002 with some velocity distribution

  12. A new gauge boson X, couples to SM particles and the WIMP through kinetic vector boson mixing with properties: 2me ≤ mX ≤ mχβ ≤mχαDM Typical values：mX = 0.1–1 GeV, mχ = 0.1–1 TeV，αDM = αem mχ = 10GeV mχ = 100GeV 2nd rise up mχ = 1000GeV pick back small recoil energy~10eV hydrogenic atom；massless mediator

  13. Recoilenergy~1-10eV Free electron with momentum distribution change to bound state wave function， effect of large momentum tail change to： ★ larger contributionfrom initial larger momentum state phase space ★smaller contributiondue to overcome ionization energy

  14. Recoil energy: keV region: NRdominant ！ eV region: ER dominant ! 10~several hundred eV region: ? That’s CDEX most interested region !

  15. Static free electron If R0 Universal 0.245, 0.433,0.571 ER spectrum Phase B：> NR spectrum NR spectrum Phase A：> ER spectrum Event rate Static target： Recoil energy Incident kinetic energy Incident particle mass Needs initial momentum distribution and bounded states effects!

  16. Free electron with some momentum distribution Impact of electron Initial velocity

  17. Free electron with some momentum distribution Energy<0 Phase B Too big energy ？ Phase A Effect of initial velocity Phase B

  18. Free electron with some momentum distribution 4.3, 7×10-7 4.7, 5×10-8

  19. Free electron with some momentum distribution 0.37, 0.33 2.8, 3×10-5 4.3, 7×10-7

  20. When dark matter mass become small More steep Reduce little bit increase

  21. At 10~several hundred eVregion: Competation result of ER and NR is still not clear May or may not produce measurable event rate More nuclear & atomic calculation is needed !

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