Latest results from the XENON Program

Transcription

1 Rencntres de Mrind 2013 Latest results frm the XENON Prgram Maxime Le Callch, On behalf f the XENON Cllabratin Very High Energy Phenmena in the Universe

2 Rencntres de Mrind 2013, VHEPU The XENON cllabratin: Mre than 100 peple frm 16 institutins: Purdue M. Le Callch, Subatech, Nantes (Fr) Bern 2

3 Rencntres de Mrind 2013, VHEPU Intrductin t Dark Matter: What d we knw abut Dark Matter: Characteristics f the DM candidate: - Lw interactin with EM radiatins and barynic matter - Stable (relic density) - Nn-relativistic (structures) DM candidate: - WIMPs, Weakly Interactive Massive Particle (SUSY) Direct detectin with xenn: Rate ~ M det M χ ρσ v χ + N χ + N M. Le Callch, Subatech, Nantes (Fra) χ Nuclei E recil 100 kev Sme advantages f xenn: High stpping pwer Intrinsically pure Scalable Spin Independent and Dependent analysis Nuclear recil 3

4 The XENON100 TPC: GXe Ande mesh grid mesh Cathde mesh LXe (62 kg) ~ 30 cm ~ 30 cm E d ~ 0.53kV/cm χ/ n γ / β S1 S1 S2 e- e- e- S1 Drift time Drift time S2 S2 Field shaping rings Rencntres de Mrind 2013, VHEPU E. Aprile et al. (XENON100), Astrpart. Phys. 35, (2012) Nuclear Recil Electrnic Recil M. Le Callch, Subatech, Nantes (Fr) Scintillatin (S1) and Charge (S2) Signals - ER / NR discriminatin 3D Recnstructin fr fiducializatin: - (XY) Tp PMTs hit pattern (± 3 mm) - (Z) Drift time (± 0.3 mm) Multiple scattering rejectin Tp array 98 PMTs Bttm array 80 PMTs Materials selected fr lw radiactivity - Neutrn / WIMP discriminatin 4

5 Rencntres de Mrind 2013, VHEPU New data taking in : New data taking fr Dark Matter search : - Frm March 1 st 2011 up t April 1 st Mre than ne year f cntinuus peratin! - A ttal f live days f data cllected - Excellent detectr perfrmance and stability Increase γ calibratin - 35x mre data than science data in regin f interest (ROI), taken during all the science run Increase neutrn calibratin: - tw expsure campaigns: - At beginning - At abut the end E.Aprile et al., Phys. Rev. Let. 105, (2010) f the run Kr cntaminatin in Xe: - Reduced by a factr 20 by crygenic distillatin E.Aprile et al., Phys. Rev. Let. 107, (2011) M. Le Callch, Subatech, Nantes (Fr) E.Aprile et al., Phys. Rev. Let. 109, (2012) 5

6 Rencntres de Mrind 2013, VHEPU Reduced 85 Kr level and backgrund: The 85 Kr istpe: - Naturally present in cmmercial xenn - Lng-lived β - emitter (99.6%) with E max = 687 kev - Previus science run sensibility limited because f accidental leak leading t high Kr/Xe level Kr reductin: - Befre the beginning f the science run, in Fall 2010, LXe was distilled by n-site dedicated clumn - Kr/Xe prprtin reduced dramatically: - RGMS Measurement: (19±1) ppt XENON100 distillatin clumn Kr in 2 nd science run M. Le Callch, Subatech, Nantes (Fr) Backgrund: - Very gd agreement between MC simulatins fr EM backgrund and measured data in WIMP search regin - Backgrund is well understd in the full energy range 6

7 Rencntres de Mrind 2013, VHEPU Imprved S2 trigger efficiency and lwered S1 threshld: Imprved S2 trigger efficiency: - 100% efficiency fr S2 150 PE (~ 10 electrns) - Ability t trigger n smaller signals S2 threshld (S2>150 pe) NR acceptance Overall acceptance Lwered S1 threshld - Frm 4 PE (8.7 kevnr) t 3 PE (6.6 kevnr) M. Le Callch, Subatech, Nantes (Fr) 7

8 - 60 C and 232 Th surces used fr ER calibratin - Data taken weekly during all the science run (40 lives days) - 35x mre data than fr Dark Matter search - Expected events in a benchmark regin : ± events AmBe surce used fr neutrn recil calibratin - Tw expsure campaigns (beginning and end f the run) - Nuclear recil estimatins dne with Geant4 simulatin - Expected events in a benchmark regin : events Rencntres de Mrind 2013, VHEPU Expected Backgrund during the secnd science run: Electrnic recil backgrund: Neutrn recil backgrund: Ttal backgrund: - In the benchmark regin, the expected backgrund is in ttal: 1. 0 ± 0. 2 events E. Aprile et al. (XENON100), arxiv: E. Aprile et al. (XENON100), Phys. Rev. Lett. 109, (2012) M. Le Callch, Subatech, Nantes (Fr) 8

9 Data analysis: Rencntres de Mrind 2013, VHEPU Blinded analysis: - NR and ER discriminatin by S2/S1 rati - Defined blind regin: - S1 in benchmark regin (3 30 PE) - S2 threshld cut (S2 > 150 PE) % ER rejectin line (Nt used in PL analysis) Fiducializatin: - Events rejectin by defining a 34 kg ellipsid E. Aprile et al. (XENON100), arxiv: M. Le Callch, Subatech, Nantes (Fr) 9

10 Results: n WIMP signal Rencntres de Mrind 2013, VHEPU Prfile Likelihd analysis: Crsscheck: using benchmark regin - S1 range frm 3 30 PE - Signal regin abve 97% NR quantile Results: - After unblinding, 2 events were fund in the benchmark WIMP search regin - Bth events have an S1 signal between 3 PE and 4 PE - Wavefrms are f high quality - Bth events are at the lwer edge f NR band - Prbability that 2 events fluctuate ver the backgrund expectatin is 26.4 % N WIMP signal!!! - S1 range frm 3 20 PE - Signal regin abve 97% NR quantile - Signal regin belw 99.75% rejectin line fr ER M. Le Callch, Subatech, Nantes (Fr) 10

11 Latest SI limit frm XENON100 : Rencntres de Mrind 2013, VHEPU Lwest limit fr M χ = 55 GeV/c 2 : cm 2 (90% C.L.) XENON100 Spin-independent WIMP-nuclen crss-sectin E. Aprile et al. (XENON100), Phys. Rev. Lett. 109, (2012) M. Le Callch, Subatech, Nantes (Fr) 11

12 Rencntres de Mrind 2013, VHEPU New XENON100 Spin Dependent limit: XENON100 SD Analysis: Neutrn: - Analysis fr SD cupling f WIMPs t 129 Xe (26.2%) and 131 Xe (21.8%) (unpaired n) - Event selectin and data analysis (Prfile Likelihd) as fr SI analysis - Results by using the new nuclear mdel frm Menendez et al. - Relatively small impact f nuclear mdel fr pure neutrn cupling - Strng dependence n nuclear mdel used fr pure prtn cupling Prtn: Neutrn cupling: lwest limit (WIMP masses > 6 GeV/c²) M χ = 45 GeV. c 2 : cm 2 (90% C.L.) E. Aprile et al. (XENON100), arxiv:1301,6620 M. Le Callch, Subatech, Nantes (Fr) 12

13 Rencntres de Mrind 2013, VHEPU Other upcming results frm XENON100: - A new run has started with new purificatin frm Kr by distillatin - Expected Nuclear Recil backgrund in XENON100 - MC / Data cmparisn fr XENON100 Nuclear Recil respnse - Single electrns charge signals in XENON100 - Gamma backgrund annual mdulatin analysis - Much mre M. Le Callch, Subatech, Nantes (Fr) 13

14 Rencntres de Mrind 2013, VHEPU Next step: XENON1T XENON100 Hall B XENON1T Characteristics: - 1 m drift TPC with 2.4 tn LXe (1 tn fiducial) - 10 m water shield as Cerenkv Mun Vet x less backgrund than XENON100 - Apprved by INFN fr installatin at LNGS - Majrity f funding secured - Cnstructin starts in Spring Science Data prjected t start in Sensitivity gal: The Recvering and Strage system f XENON1T: ReStX Heat exchanger Cling system T XENON1T crystat cm 2 after 2 years f data taking M. Le Callch, Subatech, Nantes (Fr) 3.2 m 2.7 m - R&D in Subatech labratry - Will be installed in Gran Sass in

15 Rencntres de Mrind 2013, VHEPU Summary: XENON100 Latest run: 225 live days f new data, n dark matter evidence Mst stringent Spin Independent results: M χ = 55 GeV/c 2 : cm 2 (90% C.L.) Mst stringent Spin Dependent results: M χ = 45 GeV/c 2 : cm 2 (90% C.L., neutrn) We are currently taking new data Twards the next generatin: XENON1T XENON1T cnstructin in Hall B will start in Spring 2013 Thank yu fr yur attentin M. Le Callch, Subatech, Nantes (Fr) 15