Direct Dark Matter Detection - Part III Julien Billard Institut de Physique Nucléaire de Lyon / CNRS / Université Lyon 1 Ecole de GIF September 19-24, 2016 1
Where to look for Dark Matter? 10 - 37 10 - 1 C D D A M 10 - 38 10 - 2 M I S C ( l 2 ) 0 1 2 i t e 10 - 39 10 - 3 ( CoGeNT 2 0 WIMP - nucleon cross section @ cm 2 D (2012) 1 WIMP - nucleon cross section @ pb D 3 ) 10 - 40 10 - 4 CDMS Si S (2013) u SIMPLE (2012) p e 10 - 41 COUPP (2012) r 10 - 5 C DAMA D ZEPLIN-III (2012) M S CRESST 10 - 42 10 - 6 CDMS II Ge (2009) L T ( 2 0 EDELWEISS (2011) Xenon100 (2012) 1 4 ) 10 - 43 10 - 7 LUX (2013) 10 - 44 10 - 8 10 - 45 10 - 9 10 - 46 10 - 10 10 - 47 10 - 11 Everywhere !! 10 - 48 10 - 12 10 - 49 10 - 13 10 - 14 10 - 50 1 10 100 1000 10 4 2 Julien Billard (IPNL) - GIF 2016 WIMP Mass @ GeV ê c 2 D
Where to look for Dark Matter? 10 - 37 10 - 1 C D D A M 10 - 38 10 - 2 M I S C ( l 2 ) 0 1 2 i t e 10 - 39 10 - 3 ( CoGeNT 2 0 WIMP - nucleon cross section @ cm 2 D (2012) 1 WIMP - nucleon cross section @ pb D 3 ) 10 - 40 10 - 4 CDMS Si S (2013) u SIMPLE (2012) p e 10 - 41 COUPP (2012) r 10 - 5 C DAMA D ZEPLIN-III (2012) M S CRESST 10 - 42 10 - 6 CDMS II Ge (2009) L T ( 2 0 EDELWEISS (2011) Xenon100 (2012) 1 4 ) 10 - 43 10 - 7 LUX (2013) 10 - 44 10 - 8 10 - 45 10 - 9 10 - 46 10 - 10 Everywhere !! 10 - 47 10 - 11 … Wait, not so fast ! 10 - 48 10 - 12 10 - 49 10 - 13 10 - 14 10 - 50 1 10 100 1000 10 4 3 Julien Billard (IPNL) - GIF 2016 WIMP Mass @ GeV ê c 2 D
The neutrino background Neutrino WIMP Based on: - J. Billard, L. Strigari and E. Figueroa-Feliciano, PRD 89 (2014) - F. Ruppin, J. Billard, L. Strigari and E. Figueroa-Feliciano, PRD 90 (2014) - C. O’Hare, J. Billard, E. Figueroa-Feliciano, A. Green and L. Strigari, PRD 92 (2015) 4 Julien Billard (IPNL) - GIF 2016
The neutrino background The neutrino flux at an Earth based detector: 13 10 ] -1 12 10 .MeV pp pep hep -1 7Be_384.3keV 9 .s 10 7Be_861.3keV -2 Neutrino Flux [cm 8B 13N 15O 6 10 17F dsnbflux_8 dsnbflux_5 dsnbflux_3 3 10 AtmNu_e AtmNu_ebar AtmNu_mu AtmNu_mubar 1 Geo neutrinos are negligible -3 10 3 -1 2 10 10 10 1 10 Neutrino Energy [MeV] 5 Julien Billard (IPNL) - GIF 2016
The neutrino background The neutrino flux at an Earth based detector: 13 10 ] -1 12 10 .MeV pp pep Solar neutrinos: pp-chain hep -1 7Be_384.3keV 9 .s 10 7Be_861.3keV -2 Neutrino Flux [cm 8B 13N 15O 6 10 17F dsnbflux_8 dsnbflux_5 dsnbflux_3 3 10 AtmNu_e AtmNu_ebar AtmNu_mu AtmNu_mubar 1 Geo neutrinos are negligible -3 10 3 -1 2 10 10 10 1 10 Neutrino Energy [MeV] 5 Julien Billard (IPNL) - GIF 2016
The neutrino background The neutrino flux at an Earth based detector: 13 10 ] -1 12 10 .MeV pp pep Solar neutrinos: pp-chain hep -1 7Be_384.3keV 9 .s 10 7Be_861.3keV -2 Neutrino Flux [cm 8B 13N Solar neutrinos: CNO 15O 6 10 17F dsnbflux_8 dsnbflux_5 dsnbflux_3 3 10 AtmNu_e AtmNu_ebar AtmNu_mu AtmNu_mubar 1 Geo neutrinos are negligible -3 10 3 -1 2 10 10 10 1 10 Neutrino Energy [MeV] 5 Julien Billard (IPNL) - GIF 2016
The neutrino background The neutrino flux at an Earth based detector: 13 10 ] -1 12 10 .MeV pp pep Solar neutrinos: pp-chain hep -1 7Be_384.3keV 9 .s 10 7Be_861.3keV -2 Neutrino Flux [cm 8B 13N Solar neutrinos: CNO 15O 6 10 17F dsnbflux_8 DSNB neutrinos dsnbflux_5 dsnbflux_3 3 10 AtmNu_e AtmNu_ebar AtmNu_mu AtmNu_mubar 1 Geo neutrinos are negligible -3 10 3 -1 2 10 10 10 1 10 Neutrino Energy [MeV] 5 Julien Billard (IPNL) - GIF 2016
The neutrino background The neutrino flux at an Earth based detector: 13 10 ] -1 12 10 .MeV pp pep Solar neutrinos: pp-chain hep -1 7Be_384.3keV 9 .s 10 7Be_861.3keV -2 Neutrino Flux [cm 8B 13N Solar neutrinos: CNO 15O 6 10 17F dsnbflux_8 DSNB neutrinos dsnbflux_5 dsnbflux_3 3 10 AtmNu_e AtmNu_ebar Atm. neutrinos AtmNu_mu AtmNu_mubar 1 Geo neutrinos are negligible -3 10 3 -1 2 10 10 10 1 10 Neutrino Energy [MeV] 5 Julien Billard (IPNL) - GIF 2016
The neutrino background Neutrino interactions with Dark Matter experiment target material • Coherent neutrino-nucleus elastic scattering (CNS): Nuclear recoil � � � � • σ : Cross Section • G f : Fermi Constant • E r : Recoil Energy • Q W : Weak Charge ~ A Ν Ν Neutral current • E ν : Neutrino Energy • m N : Atomic Mass No flavor-specific terms!!! Same rate for ν e , ν µ , and ν τ Ultimate background to direct detection 6 Julien Billard (IPNL) - GIF 2016
The neutrino background Neutrino interactions with Dark Matter experiment target material • Coherent neutrino-nucleus elastic scattering (CNS): pp pp 8 5 10 10 ] ] pep pep -1 -1 Event rate [(ton.year.keV) Number of events [(ton.year) hep hep 4 7Be_384.3keV 10 7Be_384.3keV 7Be_861.3keV 7Be_861.3keV 8B 8B 5 10 13N 13N 15O 15O 17F 17F 2 10 dsnbflux_8 dsnbflux_8 dsnbflux_5 dsnbflux_5 dsnbflux_3 dsnbflux_3 2 10 AtmNu_e AtmNu_e AtmNu_ebar AtmNu_ebar AtmNu_mu 1 AtmNu_mu AtmNu_mubar AtmNu_mubar Total Total -1 10 -2 10 -4 10 -4 10 -3 -2 -1 2 -3 -2 -1 2 10 10 10 10 10 10 10 10 1 10 1 10 Recoil energy [keV] Energy threshold [keV] Depending on the Energy threshold, the CNS background can be very high! - 1 keV threshold -> 100 evt/ton/year on Ge detector 7 Julien Billard (IPNL) - GIF 2016
The neutrino background Neutrino interactions with Dark Matter experiment target material 8 10 ] -1 -45 2 2 WIMP signal: m = 6 GeV/c , = 4.4x10 cm σ Event rate [(ton.year.keV) χ -n χ Total CNS background Weak neutrino-electron 5 10 2 10 1 − 10 4 − 10 3 − 2 1 2 − − 10 10 10 1 10 10 Recoil energy [keV] 8 Julien Billard (IPNL) - GIF 2016
The neutrino background Neutrino interactions with Dark Matter experiment target material 8 10 Neutrino-electron ] -1 -45 2 2 WIMP signal: m = 6 GeV/c , = 4.4x10 cm σ Event rate [(ton.year.keV) χ -n χ background Total CNS background Weak neutrino-electron 5 10 negligible for Ge cryogenic detectors BUT problematic for Xe based detectors 2 10 1 − 10 4 − 10 3 − 2 1 2 − − 10 10 10 1 10 10 Recoil energy [keV] 8 Julien Billard (IPNL) - GIF 2016
The neutrino background Neutrino interactions with Dark Matter experiment target material 8 10 Neutrino-electron ] -1 -45 2 2 WIMP signal: m = 6 GeV/c , = 4.4x10 cm σ Event rate [(ton.year.keV) χ -n χ background Total CNS background Weak neutrino-electron 5 10 negligible for Ge cryogenic detectors BUT problematic for Xe based detectors 2 10 1 − 10 WIMP or neutrino ( 8 B)?? 4 − 10 3 − 2 1 2 − − 10 10 10 1 10 10 Recoil energy [keV] 8 Julien Billard (IPNL) - GIF 2016
The neutrino background WIMP and neutrino equivalence: ➡ Using a maximum likelihood analysis where we fit a WIMP hypothesis to the different neutrino components we can determine the WIMP-neutrino equivalent models Xe target, no energy threshold, perfect energy resolution 9 Julien Billard (IPNL) - GIF 2016
The neutrino background (F. Ruppin et al., PRD 90 (2014)) WIMP discovery potential: • 90% probability to get a 3 sigma or more WIMP discovery significance • Computed using a profile likelihood ratio test statistic Exposure (ton-year) 1e-05 0.0001 0.001 0.01 0.1 1 10 100 1000 SI discovery limit at 6 GeV/c 2 [cm 2 ] 1% 10% 2% 15% 10 -42 ∝ 1/MT 5% 20% Saturation regime 10 -43 2 orders of magnitude Discrimination 10 -44 High stats 8B ∝ 1/ √ M T 10 -45 10 -46 10 -2 10 -1 10 0 10 1 10 2 10 3 10 4 10 5 10 6 Number of expected 8 B neutrino events In the case of a perfect spectral matching , we expect the sensitivity to scale as: 10 Julien Billard (IPNL) - GIF 2016
The neutrino background (F. Ruppin et al., PRD 90 (2014)) 11 Julien Billard (IPNL) - GIF 2016
The neutrino background 12 Julien Billard (IPNL) - GIF 2016
The neutrino background How to bypass this neutrino-induced saturation of the sensitivity? 1. Reducing the systematic uncertainties on neutrino fluxes 2. Annual modulation (first studied in J. H. Davis, JCAP 2015) 3. Directional detection (first studied in P. Grothaus et al., PRD 2014) 4. Target complementarity: combining data from several experiments, (F. Ruppin et al., PRD 2014) 13 Julien Billard (IPNL) - GIF 2016
The neutrino background Considering target complementarity from different experiments ➡ The additional discrimination power brought by using different targets is related by how different are the WIMP-neutrino equivalent models (F. Ruppin et al., PRD 90 (2014)) C O F Si Ar Ca Ge I Xe W C O F Si Ar Ca Ge I Xe W 12 SI SD p WIMP-nucleon cross section [cm 2 ] 10 -36 SD n 11 WIMP mass [GeV/c 2 ] 10 10 -38 9 Great complementarity 10 -40 in the SD-p case between Ge and F! 8 10 -42 7 6 10 -44 5 20 40 60 80 100 120 140 160 180 20 40 60 80 100 120 140 160 180 Target number of nucleons (A) Target number of nucleons (A) • Moderate differences in the WIMP mass and in the SI cross sections (SI and CNS are coherent) • Huge differences in the SD case -> WIMP hypothesis can’t fit all experiments 14 Julien Billard (IPNL) - GIF 2016
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