Dark Matter: New Results from Direct Detection
PANIC at MIT July 25, 2011
Laura Baudis University of Zurich Matter and Energy Content of our Universe
Laura Baudis, University of Zurich, Dark Matter, PANIC 2011 Some dark matter candidates: Particle Dark Mattermass vs. Candidates interaction strength plane
Some Dark Matter Candidate Particles
24 10 Masses and cross sections 21 10 18 Fig. by Howie Baer span many orders of 10 15 10 12 magnitude 10 9 10 Q-ball 6 10 3 -6 15 10 0 From 10 eV to 10 GeV 10 -3 10 neutrinos WIMPs : -6 10 neutralino
(pb) -9 10 KK photon
int -12 From non-interacting to 10 branon ! wimpzilla -15 LTP 10 strongly interacting -18 Black Hole Remnant 10 -21 10 -24 10 axion axino -27 10 SuperWIMPs : We know that the dark -30 10 fuzzy CDM gravitino -33 matter particle must be some 10 KK graviton -36 10 -39 state not contained in the 10 -33 -30 -27 -24 -21 -18 -15 -12 -9 -6 -3 0 3 6 9 12 15 18 Standard Model 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 mass (GeV)
Monday, July 6, 2009 3 Laura Baudis, University of Zurich, Dark Matter, PANIC 2011 Weakly Interacting Massive Particles
One good idea: WIMPs; in thermal equilibrium in the early Universe
χ +¯χ X + X¯ ↔ Decouple from the rest of the particles when M >> T (“cold”)
Their relic density can account for the dark matter if the annihilation cross section is weak (~ pb)
2 27 3 1 1 Ω h 3 10− cm s− χ × σ v A Such particles are predicted to exist in most Beyond-Standard-Model theories (neutralino, lightest Kaluza-Klein particle, etc)
Laura Baudis, University of Zurich, Dark Matter, PANIC 2011 eeaMroá naota(UZH) Undagoitia Marrodán Teresa IPsearch WIMP χχ detection Indirect → e + e − , p p χ detection Direct N → akMatter Dark χ N The WIMP Hypothesis is Testable !"#$%#&''()*+,+-#)
Deep underground In space→ At the LHC akb .Baroncelli A. by Talk p+p rdcina LHC at Production rnbe 10/014/31 / 4 21/07/2011 Grenoble, •)./0-12#")"#,#3,1-'().14&56714)#$#3,-1"#') 312#-),8#)39$&4"-&36$)'+-:63#')1:),8#)"#,#3,1-)
;*.<=>) → •))?@)ABB) C)64")D@?BB)C)"#,#3,1-')6$-#6"9)
E+&$,>) χ
•)F+--#4,$9)26$&"674C),8#)"#'&C4)6,)GHI) lot a + •)J$64),1)-+4)?B) @)ABB)C)"#,#3,1-')&4)DBKD() LBBB)MC>"69) •)H#4'&72&,9)-#638)NO@KB PQ)0E)
χ χ χ q q χ
- q q χ q- q χ
We should learn a lot from direct detectors, from indirect detectors and from accelerators!
Laura Baudis, University of Zurich, Dark Matter, PANIC 2011 Direct Detection of WIMPs: Principle
Elastic collisions with nuclei in ultra-low background detectors
Energy of recoiling nucleus: few tens of keV WIMP
q2 µ2v2
ER = = (1 cosθ) ER 2mN mN −
• q = momentum transfer
• µ = reduced mass (mN = nucleus mass; mΧ = WIMP mass) • v = mean WIMP-velocity relative to the target • θ = scattering angle in the center of mass system WIMP Laura Baudis, University of Zurich, Dark Matter, PANIC 2011 Expected Rates in a Terrestrial Detector
For now strongly simplified: Astrophysics
ρχ R N σχN v ∼ mχ
N = number of target nuclei in a detector Particle physics
ρχ = local density of the dark matter in the Milky Way
mχ = WIMP-mass
σχN =cross section for WIMP-nucleus elastic scattering
Laura Baudis, University of Zurich, Dark Matter, PANIC 2011 Local Density of WIMPs in the Milky Way
3 3 ρ =0.1 0.7GeVcm− ρ =2 7GeVcm− halo − disk −
0.3 GeV cm-3 ⇒ ~ 3000 WIMPs m-3
(MW = 100 GeV)
WIMP flux on Earth: ~ 105 cm-2s-1 (100 GeV WIMP)
Even though WIMPs are weakly interacting, this flux is large enough so that a potentially measurable fraction
(J. Diemand et all, Nature 454, 2008, 735-738) will elastically scatter off nuclei
~ 600 kpc
Laura Baudis, University of Zurich, Dark Matter, PANIC 2011 WIMP Mass and Cross Section
Example for recent predictions from supersymmetry: 13 cross sections down to a few ×10-47 cm2
-40 -40 ] 10 ] 10 2 2 CMSSM -41 -41 [cm 10 Buchmueller et al; [cm 10 SI p SI p # # arXiv:1102.4585v1 [hep-ph] 10-42 10-42
10-43 10-43
-1 -1 10-44 ~ 1 event10-44 kg year
10-45 10-45
10-46 10-46
-1 -1 10-47 ~ 1 event10-47 ton year
-48 -48 10 2 3 10 2 3 10 210 10 210 m"0 [GeV/c ] m"0 [GeV/c ] ! ! 1 1
Laura Baudis, University of Zurich, Dark Matter, PANIC 2011
-40 -40 ] 10 ] 10 2 2
-41 -41 [cm 10 [cm 10 SI p SI p # # 10-42 10-42
10-43 10-43
10-44 10-44
10-45 10-45
10-46 10-46
10-47 10-47
-48 -48 10 2 3 10 2 3 10 210 10 210 m"0 [GeV/c ] m"0 [GeV/c ] ! ! 1 1
0 SI Figure 7. The regions of the (mχ˜1 , σp ) planes in the CMSSM (upper left), NUHM1 (top right), VCMSSM (lower left) and mSUGRA (lower right) favoured at the 68% and 95% CL including the CMS constraint (solid lines) and excluding it (dashed lines). The best-fit points after (before) the CMS and ATLAS constraints [19,20] are shown as open (solid) green stars, and the best pre-LHC fits as green ‘snowflakes’. The results are calculated assuming ΣπN =64MeV.
Ref. [59] analyzes the CMS constraint within CYT (grant FPA 2007–66387 and FPA 2010– the CMSSM and reaches similar conclusions on 22163-C02-01), and the work of K.A.O. was sup- the increases in m1/2 and tan β that it entails. ported in part by DOE grant DE–FG02–94ER– Ref. [60] considers a more general model than 40823 at the University of Minnesota. K.A.O. those examined here. also thanks SLAC (supported by the DOE un- der contract number DE-AC02-76SF00515) and the Stanford Institute for Theoretical Physics for This work was supported in part by the Euro- their hospitality and support while this work was pean Community’s Marie-Curie Research Train- being finished. ing Network under contracts MRTN-CT-2006- 035505 ‘Tools and Precision Calculations for Physics Discoveries at Colliders’ and MRTN-CT- REFERENCES 2006-035482 ‘FLAVIAnet’, and by the Spanish MEC and FEDER under grant FPA2005-01678. 1. G. Aad et al. ATLAS Collaboration, Expected The work of S.H. was supported in part by CI- Performance of the ATLAS Experiment - De- Expected Interaction Rates
Differential recoil rate: integrate over WIMP velocity distribution
Kinematics vmax dR σ0ρ0 2 f(v, t) 3 = 2 F (ER) d v 2 2 dE2 R 2mχµ v>√mN ER/2µ v dN ρχ σp|F (q)| A 3 f⊕(#v,t) (t)= 2 d v dER mχ 2µp !v>vmin(E ) v Different WIMPR masses Different target nuclei
5 10 20 m [GeV] 30 ! m +M 40 χ ER 50 vmin = MWIMP = 100 GeV mχ 2M -44 2 " σWN=1×10 cm minimal v required to produce recoil ER
events on Ge / keV [arb. Units] Diff. rate [events/(100 kg d keV)] d Diff.kg [events/(100 rate 0 10 20 30 40 50 Recoil energy [keVr] Enr [keV] (Standard halo model with ρ= 0.3 GeV/cm3) spectrum gets shifted to lowLaura energies Baudis, University of forZurich, Dark low Matter, WIMP PANIC 2011 masses ⇒ need light target and/or low threshold on ER to see light WIMPs
T. Schwetz, TEXAS 2010, 9 Dec 2010 – p. 7 The Challenge
To observe a signal which is: very small ( few keV) extremely rare (1 per ton per year?) embedded in a background that is millions of times higher
• Why is it challenging?
• Detection of low-energy particles - done! ➡e.g. micro-calorimetry with phonon readout
• Rare event searches with ultra-low backgrounds - done! ➡e.g SuperK, Borexino, SNO, etc
• But: can we do both?
Laura Baudis, University of Zurich, Dark Matter, PANIC 2011 Direct Dark Matter Detection Techniques
WIMP Phonons WIMP
Al2O3: CRESST-I
Ge, Si: CDMS CaWO4, Al2O3: Ge: EDELWEISS CRESST
C, F, I, Br: NaI: DAMA/LIBRA PICASSO, COUPP NaI: ANAIS here: Ge: Texono, CoGeNT CsI: KIMS 3 focus CS2,CF4, He: DRIFT LXe: XENON LXe: XMASS DMTPC, MIMAC LXe: LUX LAr, LNe: on Ar+C H : Newage LXe: ZEPLIN 2 6 DEAP/CLEAN LAr: WARP recent LAr: ArDM Charge Light results Laura Baudis, University of Zurich, Dark Matter, PANIC 2011 Phonons: Cryogenic Experiments at T~ mK
Detect a temperature increase after a particle interacts in an absorber
χ χ
T0 E
Absorber T-sensor
T-sensors: superconductor thermistors or superconducting transition sensors
Laura Baudis, University of Zurich, Dark Matter, PANIC 2011 Phonons: Cryogenic Experiments at T~ mK
Advantages: high sensitivity to nuclear recoils (measure the full energy in the phonon channel); good energy resolution, low energy threshold (keV to sub-keV)
Ratio of light/phonon or charge/phonon:
nuclear!"#$%" versus&'( electronic#)*"#$ recoils#+%,# discrimination-+
! 1';%=*=@*%=7%B';%=7*;=* 9"*:";"<;=#)*/>/?@*5'$$'A*'7:*7"6;#=7A CD=7=7A*!"#$%&'* :%A;%756%AD"A*(";E""7* "&"<;#=7*'7:*76<&"'#* electronic recoils #"<=%&A2 Background region ! F=7%B';%=7*,%"&:*('7:AG* @67<;%=7Ratio'&*@=#$*( 'ofA": *=7* H%7:D'#:*$=:"&*@%;*;=* 7"6;#=7Acharge*@#=$*/>/?@* <'&%(#';%=72 to nuclear recoils ! ?6;*';*;E=*A;'7:'#:* :"I%';%=phonon7A*@=#*76<&"'#* Expected signal region #"<=%&*A"&"<;%=72
! J6&K*"&"<;#=7*#"<=%&A* '6;=$';%<'&&,*D'I"* ,%"&:L-*'@;"#*<'&%(#';%=72
!"#$%&'()*+',*-.)*/..0 12*32*45(6#7 8 Laura Baudis, University of Zurich, Dark Matter, PANIC 2011 Phonons: The CDMS Experiment
Final WIMP search runs - 191 kg-d: 2 events passing all cuts
Gamma-Background Science, 1186112 (2010)
Event 1: Tower 1, ZIP 5 (T1Z5) Sat. Oct. 27, 2007 Expected signal region Event 2: Tower 3, ZIP 4 (T3Z4) Sun. Aug. 5, 2007
Expected background: 0.8 ± 0.1 (stat) ± 0.2 (syst) events Probability to observe two or more events is 23%
Laura Baudis, University of Zurich, Dark Matter, PANIC 2011 Signal Significance likelihood ratio test probability that data are compatible with → background only Resulting significance for a signal: 4.6 σ ∼ systematic background uncertainties still under study → ultimate clarification by reduction of background level →
Signal Significance likelihood ratio test probability that data are compatible with → background only Resulting significance for a signal: 4.6 σ ∼ systematic background uncertainties still under study → ultimate clarification by reduction of background level →
Phonons: CRESST and EDELWEISS WIMP search : final results EDELWEISS at Modane Run 32 – ExcessCRESST of Eventsat LNGS in O-Band
fiducial volume events, 427 kg.d
γ + β band 䍐 Five WIMP candidates: 50 events in acceptance - 4 evts: 20.8 < E < 23.2 keV region - 1 evt @ 172 keV acceptance region (O-band)
αbut: Ostrong overlap between O,Ca « alpha tail » alphas degraded alphas Wand W-band in this energy Possible WIMP Signal region!
fit WIMP signal, takingarXiv1103.4070 into account aboveRaimund Strauss, backgrounds TU Munich 32 Ge detectors at 18J. mKGironnet - IPNL - (Patrasmχ 2011and Possibleσ as free WIMP parameters)CaWO Signal310 detectors at 10 mK best fit to the observed57 events events: (730 kg-day) 5 events (427 kg-day) fit WIMP signal, taking into account above backgrounds (m and σ asfocus free parameters) on reducing backgrounds 3 expected from backgrounds α eventsχ 9.3 best fit to the observed events: neutron events 17.3 operates new, 800 g detectors with α events 9.3 2 e/γ events 9.0 (fixed) mχ 13 GeV/c improved background rejection neutron events 17.3 ∼ 2 5 e/γ events 9.0 (fixed) mσχ 13 GeV/3 c10− pb signal events 22.6 ∼ ∼ ·5 σ 3 10− pb Laura Baudis, University of Zurich, Dark Matter, PANIC 2011 signal events 22.6 ∼ ·
Jens Schmaler Results from the CRESST Dark Matter Search 10
Jens Schmaler Results from the CRESST Dark Matter Search 10 Future Cryogenic Dark Matter Projects ULISSE = LSM extension Cryogenic mK Experiments: Near Future • Civil works started for safety gallery US/Canada: SuperCDMS (15 kg Europe:(600m EURECA done )(100 kg to 1.0 CRESST at LNGS EDELWEISS at LSM to 1.5CDMS/SuperCDMS tons Ge experiment) at Soudan ton• Decisioncryogenic experiment)for ULISSE to be taken in
10 kg array of 33 CaWO4 spring 2011 to profit of dig machines 10 kg (30 modules) of NTD LargerCDMS-II Gerun 129detectors in progress (650g) with Multi-target approach detectors SuperCDMS detectors (1!! thick ZIPs, new 66 SQUID channel array and NbSi Ge detectors in (2X M!, capital) new cryostat improvedeach 650 g of readout Ge) have been tested - new limit from operating 2 Installation of first SuperTower at To• beRecommendation located at the ULISSE by LabSAC in 2010 detectors (48 kg d) published - new charge electrodes - 100 kg d under analysis ToSoudan be located in spring 2009 at SnoLAB (Modane extension) in France in 2008, arXiv:0809.1829v1 SuperCDMS:-45 2 The Next Generation - data taking in progress Goal: 5 x 10 cm with 16 kg Ge • Decision now (november 2010) in - new run in progress hands of prime minister
Laura Baudis, University of Zurich, Dark Matter, PANIC 2011
Laura Baudis, University of Zurich, ENTApP DM Workshop, February 3, 2009 Rupak Mahapatra 21 UC Santa Barbara for the CDMS Collaboration Light: Noble Liquids TPCs
Large, scalable, homogeneous and self-shielding detectors
Prompt (S1) light signal after interaction in the active volume
Charge is drifted, extracted into the gas phase and detected as proportional light (S2)
- charge/light depends on dE/dx - good 3D position resolution
=> particle identification
Ar (A = 40); λ = 128 nm Xe (A=131); λ = 178 nm Laura Baudis, University of Zurich, Dark Matter, PANIC 2011 Future:XENON1T XENON1T
!"#$#%&'(')#*+ Total1 of ton 2.4 fiducialton LXe (1 masston fiducial) (total of 2.4 ton LXe) Drift length!"#$#%&' ~1m !"#$#%& Drift length(')#*+',-.//'01 = 90 cm 100x background reduction∼ with respect to !'2'3'4.567'89:6/; XENON100100x ''''.<5:=>'.8background reduction BCDEF+' The XENON ExperimentGDEH compared''''.<5:?6'3@A='?65A to XENON100 Enclosed by a 5m water shield (passive and activeShielding: muon veto) 5 m water around the detector XENON100 Timeline 2011 -XENON1T 2015 Titanium cryostat Low radioactivity photosensors
"#;/<=<>)?#)*@#ABC#>'D(0EEF@#E<#G5H$ # Timeline: 2011 - 2015 "#I==/ !"#$%&'()**#+,#-./0%&1#2#34565788 9: Teresa Marrodán Undagoitia (UZH)1 m Dark Matter 10Grenoble, m 21/07/2011 26 / 31 In conventional shield at LNGS In water Cerenkov shield at LNGS 2008 - 2011; taking science data 2011- 2015; construction to start soon Laura Baudis, University of Zurich, Dark Matter, PANIC 2011 The XENON100 Detector 161 kg of ultra-pure liquid xenon (LXe), 62 kg in the active target volume 30 cm drift gap TPC with two PMT arrays (242 PMTs) to detect the prompt and proportional scintillation signals Laura Baudis, University of Zurich, Dark Matter, PANIC 2011 Example of a 9 keV Nuclear Recoil Event S2 drift time -->z S1 70µs ~ 12cm 4 photoelectrons detected 645 photoelectrons detected from about 100 S1 photons from 32 ionization electrons which generated about 3000 S2 photons Laura Baudis, University of Zurich, Dark Matter, PANIC 2011 21 Example of a 9 keV Nuclear Recoil Event Top PMT array Bottom PMT array xe100_091215_1039_000030-830 Laura Baudis, University of Zurich, Dark Matter, PANIC 2011 22 XENON100: New Results Exposure: ~ 1471 kg-days (48 kg fiducial mass); January - June 2010 Signal region: 3 events observed Blue bands: Expected backgrounds: 1- and 2-σ expectation, based on zero signal 1.8 ± 0.6 gamma leakage events Limit (dark blue): 0.1 ± 0.08 ± 0.04 neutron events 1.5 - 2 σ worse, given 2 events at high S1 (28% Poisson probability to see 3 events when ~ 2 -45 2 Limit at MW = 50 GeV: 7 x 10 cm (90% C.L.) are expected) Laura Baudis, University of Zurich, Dark Matter, PANIC 2011 XENON: status and sensitivity New dark matter run started in March 2011 ( ~ 90 days of data) Concentration of 85Kr: lower by a factor of 5 Improved LXe purity and lower trigger threshold In parallel: construction of XENON1T @ LNGS Laura Baudis, University of Zurich, Dark Matter, PANIC 2011 Light: Liquid Xenon Detectors !"#$%&'()*$ LUX at Homestake XMASS at Kamioka • LUX in the US ➡350 kg LXe TPC, 100 kg fiducial ➡in commissioning above ground at Homestake ➡to be placed underground in spring 2012 • XMASS in Japan ➡800 kg single phase detector (642 PMTs), 100 kg fiducial, 10x10 m water shield ➡commissioning run in 2011 lower half upper and lower half Laura Baudis, University of Zurich, Dark Matter, PANIC 2011 Masaki Yamashita 2010年3月23日火曜日 Light: Liquid Argon Detectors ArDM-1t: HV System Results presented at GLA2010 - see WARP at LNGS FeasibilityArDM of at high-voltage Canfranc systems for a very long drift in liquid argon TPCs. S. Horikawa, A. Badertscher, L. Kaufmann, M. Laffranchi, A. Marchionni, M. Messina, G. Natterer, A. Rubbia. Sep 2010. 8pp. Temporary • WARP at LNGS entry e-Print: arXiv:1009.4908 [physics.ins-det] ➡ 140 kg LAr TPC !"#$%&'()$&*+' 210 stages Cockroft-Walton ➡ 8.4 t LAr veto shield !,,&-.*/' [Greinacher] circuit ➡ technical runs in 2008 and 2010 012%34'56678' 30 field shapers with 4 cm ➡ new technical run since June 2011 spacing 400 kV at cathode [3 kV/cm] • ArDM at Canfranc good drift field linearity ➡850 kg LAr TPC Rotary system for discharging ➡commissioned at CERN tested up to 70 kV [0.6 kV/cm] in ➡approved by LSC in Oct 2010 stable conditions and no particular ➡to be installed underground by the training end of 2011 suffered one sparking at 80kV ! "#$%&'()*(+,$+$-'). /01))23-4))5671-'81+,)± 9:3;<==)± >%+1)!?);<== ! Tuesday, June 7, 2011 Laura Baudis, University of Zurich, Dark Matter, PANIC 2011 Light: Liquid Argon Detectors • Single-phase detectors: use pulse MiniClean and DEAP at SnoLAB shape information + fiducialization • MiniCLEAN at SnoLAB ➡500 kg LAr (150 kg fiducial) ➡single-phase open volume ➡under construction at SNOLAB ➡to run 2012 - 2014 • DEAP-3600 at SnoLAB ➡3600 kg LAr (1000 kg fiducial) ➡single-phase detector ➡under construction at SNOLAB ➡to run 2014 - 2019 Laura Baudis, University of Zurich, Dark Matter, PANIC 2011 DARWIN: DARk matter WImp search with Noble liquids R&D and design study for next-generation noble liquid detector Location: Gran Sasso (Italy) or ULISSE (Modane Lab extension, France) Physics goal: prove WIMP-nucleon cross sections beyond 10-47 cm2 Preliminary LAr LXe 2009 - 2012: R&D and Design Study 2013: Submission of LoI, engineering studies 2014 - 2015: Construction and commissioning 2016 - 2020: Operation, physics data (darwin.physik.uzh.ch) arXiv:1012.4764v1 Laura Baudis, University of Zurich, Dark Matter, PANIC 2011 Charge: DAMA/LIBRA 250 kg of ultra-pure NaI crystals at LNGS; 0.82 tons-year Observes a time variation in the event rate with T = 1 year, ϕ = June 2±7 days Amplitude of the modulation: ~ 0.018 counts day-1 kg-1 keV-1 2-4 keV R.Bernabei et al, Eur.Phys.J. C67 (2010) Laura Baudis, University of Zurich, Dark Matter, PANIC 2011 Charge: DAMA/LIBRA Origin of the time variation in the observed rate: motion of the Earth-Sun system through the WIMP halo? environmental effects? unclear! see also David Nygren, arXiv:1102.0815 Muon rate in LNGS* Muon rate variation at LNGS: Amplitude: ~ 0.015; T = 1 year, ϕ = July 15±15 days * M.Selvi et al., Proc. 31st ICRC, ŁÓDŹ 2009 Laura Baudis, University of Zurich, Dark Matter, PANIC 2011 Charge: CoGeNT Point-contact, 330 g Ge detector at Soudan Energy threshold: ~ 0.5 keV ionization (~ 2 keV NR energy) 2011: claim of an annual modulation at 2.8-σ level (0.5 - 3 keVee), ~ 450 days arXiv: 1002.4703; C. E. Aalseth et al., PRL106 arXiv: 1106.0650; C. E. Aalseth et al. 0.5 - 0.9 keV 0.5 - 3.0 keV 3.0 - 4.5 keV surface events 1 keVee ~ 4 keV nuclear recoil energy Laura Baudis, University of Zurich, Dark Matter, PANIC 2011 New results from CDMS and XENON10 CDMS: 241 kg-days with 8 Ge detectors XENON10: 14 kg-days using LXe !"#"$%& CDMS XENON10 CDMS Collaboration, PRL 106, 131302 (2011) XENON10 Collaboration, arXiv:1104.3088, accepted in PRL • '()%*+,-.,*/0&-%%1#*&-//& 2-)3"3-$*%&2(1/3&4*&5+(#&6789%&& 90% CL upper limits on elastic scattering cross section CDMS SUF CDMS Soudan • :(&4-2;<+(1)3&%14$+-2.()=& (1 keV thresh) (10 keV thresh) • !"#"$%&%*$&1%")<&(>.#1#&")$*+,-/& #*$?(3@& DAMA/LIBRA S. Yellin, PRD, 66, 032005 (2002); arXiv:0709.2701v1 (2007) CoGeNT • A)*+<0&")$*+,-/%&(+3*+*3&40& These results 3*$*2$(+& (~14 kg d) • B(+&%>")C")3*>*)3*)$D&*/-%.2& XENON100 XENON10 XENON100 (~1500 kg d) %2-E*+") JW&8((+*D&'-/$*2?& K9R&K>+"/&8**.)<&C&8-0&TD&TGUU& V& Directional Detectors DMTPC at MIT • Correlate direction of nuclear recoil with galactic motion Light readout • Would provide robust signature CCD (PMT) • 10 - 100 events needed, depending on directional capabilities -V • DMTPC (CF4 gas TPC, at MIT) ➡first results from 10 lTPC F e- ➡1 m3 planned for WIPP 0V +V Charge 0V readout • DRIFT (negative ion, CS2 TPC, at Boulby) ➡ results from 1.5 kg-days -V ➡24 m3 planned (4 kg target) Light readout CCD (PMT) Laura Baudis, University of Zurich, Dark Matter, PANIC 2011 Summary and Prospects LHC/ILC Direct detection discover relic particle discover new particles determine physics model constrain (m,ρ×σ) and mWIMP predict direct/indirect with input from LHC/ILC cross sections determine ρlocal Indirect detection discover relic particle constrain (m,σ×∫ρ2) with input from LHC/ILC determine ρGC/halo Laura Baudis, University of Zurich, Dark Matter, PANIC 2011 End Laura Baudis, University of Zurich, Dark Matter, PANIC 2011 Beyond Current Detectors: DARWIN To reconstruct WIMP properties such a mass and scattering cross section we will (likely) need larger detectors for high-stats recoil spectra 6 Phys. Rev. D 83, 083505 (2011) 3 3 # =0.4 GeV/cm , v =544 km/s, v =230 km/s, k=1 # =0.4 GeV/cm , v =544 km/s, v =230 km/s, k=1 -8.2 [pb] 0 esc -8.2 0 [pb] 0 esc 0 p SI p SI " " fixed galactic model fixed galactic model -8.4 -8.4 reconstruction probabilities reconstruction probabilities for Ar, Ge, Xe for Xe, Xe + Ge, Xe + Ge + Ar -8.6 -8.6 -8.8 -8.8 -9 10-9 -9 10-9 -9.2 -9.2 Xe Xe Ge Xe+Ge Ar Xe+Ge+Ar -9.4 -9.4 DM benchmarks DM benchmarks 50 102 103 50 102 103 m! [GeV] m! [GeV] Miguel Pato, Laura Baudis, Gianfranco Bertone, Roberto Ruiz de Austri, Louis E. Strigarip and Roberto Trotta FIG. 1: The joint 68% and 95% posterior probability contours in the mχ σ plane for the three DM benchmarks − SI (mχLaura=25 Baudis,, 50 University, 250 GeV)of Zurich, Dark with Matter, fixed PANIC Galactic 2011 model, i.e. fixed astrophysical parameters. In the left frame we show the re- construction capabilities of Xe, Ge and Ar configurations separately, whereas in the right frame the combined data sets Xe+Ge and Xe+Ge+Ar are shown. For the local circular velocity and its uncertainty, a va- mock data that in turn are used to reconstruct the poste- p riety1.2 of measurements1.4 1.6 1.8 presents2 2.2 a broad2.4 range2.6 2.8 of central3 rior1.2 for the1.4 DM1.6 parameters1.8 2 m2.2χ and2.4 σSI2.6. The2.8 left3 frame values and uncertainties [56]. To again remain conserva- of Fig. 1 presents the results for the three benchmarks tive we use an interval bracketing recent determinations: and for Xe, Ge and Ar separately. Contours in the figure delimit regions of joint 68% and 95% posterior probabil- v0 = vlsr = 230 30 km/s (1σ) , (15) ity. Several comments are in order here. First, it is ev- ± ident that the Ar configuration is less constraining than where we take a Gaussian prior with the above mean and Xe or Ge ones, which can be traced back to its smaller A standard deviation. To account for the variation of the and larger Ethr. Moreover, it is also apparent that, while local density of dark matter in our modeling, we will take Ge is the most effective target for the benchmarks with a mean value and error given by [57, 58] mχ = 25, 250 GeV, Xe appears the best for a WIMP with mχ = 50 GeV (see below for a detailed discussion). Let 3 ρ0 =0.4 0.1 GeV/cm (1σ) , (16) us stress as well that the 250 GeV WIMP proves very ± difficult to constrain in terms of mass and cross-section There are several other recent results that determine ρ0, due to the high-mass degeneracy explained in Section II. both consistent [59] and somewhat discrepant [60] with Taking into account the differences in adopted values and our adopted value. Even in light of these uncertainties, procedures, our results are in qualitative agreement with we take Eq. (16) to represent a conservative range for the Ref. [26], where a study on the supersymmetrical frame- purposes of our study. work was performed. However, it is worth noticing that For completeness Table II summarises the information the contours in Ref. [26] do not extend to high masses on the parameters used in our analysis. as ours for the 250 GeV benchmark – this is likely be- cause the volume at high masses in a supersymmetrical parameter space is small. VI. RESULTS In the right frame of Fig. 1 we show the reconstruction capabilities attained if one combines Xe and Ge data, A. Complementarity of targets or Xe, Ge and Ar together, again for when the Galac- tic model parameters are kept fixed. In this case, for We start by assuming the three dark matter bench- mχ = 25, 50 GeV, the configuration Xe+Ar+Ge allows mark models described in Section II (mχ = 25, 50, 250 the extraction of the correct mass to better than (10) p 9 O GeV with σSI = 10− pb) and fix the Galactic model GeV accuracy. For reference, the (marginalised) mass 3 parameters to their fiducial values, ρ0 =0.4 GeV/cm , accuracy for different mock data sets is listed in Table v0 = 230 km/s, vesc = 544 km/s, k = 1. With the exper- III. For mχ = 250 GeV, it is only possible to obtain a imental capabilities outlined in Section III, we generate lower limit on mχ. XENON100 Backgrounds: Data and Predictions Data versus Monte Carlo simulations (no MC tuning, input from screening values for U/Th/K/Co/Cs etc of all detector components); no active liquid xenon veto cut Background is 100 times lower than in XENON10 and meets design specifications XENON100 collaboration, arXiv:1101.3866, PRD 83, 082001 (2011) 214 208 60 Tl 60 data (Fall 2009, no veto cut) Pb 137 Co Co 40 Cs 54Mn K MC (total) 228 85 ] Ac MC ( Kr, 120 ppt) -1 MC (222Rn, 21 µBq/mkg) -2 10 MC (136Xe 2ν ββ ) keV -1 85 222 214Bi day Kr Rn -1 2νββ 214 Bi 208 10-3 Tl Rate [events kg 10-4 0 500 1000 1500 2000 2500 3000 Energy [keV] Laura Baudis, University of Zurich, Dark Matter, PANIC 2011 XENON100 Backgrounds: Data and Predictions Data versus Monte Carlo simulations (no MC tuning, input from screening values for U/Th/K/Co/Cs etc of all detector components); no active liquid xenon veto cut Background is 100 times lower than in XENON10 (and any other dark matter experiment) and meets design specifications CRESST CoGeNT CDMS XENON10 DAMA XENON100 Laura Baudis, University of Zurich, Dark Matter, PANIC 2011 XENON100: New Results Exposure: ~ 1471 kg-days; data taken during January - June 2010 Signal region: Fiducial mass region: 3 events are observed 48 kg of liquid xenon 1.8 ± 0.6 gamma leakage events expected 900 events in total 0.1 ± 0.08 ± 0.04 neutron events expected Laura Baudis, University of Zurich, Dark Matter, PANIC 2011 Cuts acceptance and light yield parameterization all cuts apart from the S2/S1 discrimination cut NR acceptance for a 99.75% ER rejection S1 E = nr L L eff · y mean (solid) and 1-, 2-sigma uncertainties (blue bands) of Leff direct measurements Laura Baudis, University of Zurich, Dark Matter, PANIC 2011 Phase-space structure in the local dark matter distribution 3 for all six halos with about 200 million particles within R200.Fur- -3 1 -3 1 10 0 10 0 ther details of the halos and their characteristics can be found in ! ! -1 -1 Springel et al. (2008). " " 4 4 In the following analysis we will often compare the six level-2 -3 resolution halos, Aq-A-2 to Aq-F-2. To facilitate this comparison, -3 3 3 10 10 ! ! we scale the halos in mass and radius by the constant required to 2 ) 2 1 f(v) give each a maximum circular velocity of V =208.49 km/s, f(v The Local Darkmax Matter1 Distribution1 the value for Aq-A-2. We will also sometimes refer to a coordi- nate system that is aligned with the principal axes of the inner halo, 0 0 Velocity Distribution of the Dark0 150Matter300 450 600 -450 -225 0 225 450 and which labels particles by an ellipsoidal radius r defined as -1 -1 ell v [km s ] v1 [km s ] the semi-major axis length of the ellipsoidal equidensity surface on -3 1 -3 1 which the particleThe dark sits. We matter determine thedistribution orientation and sharoundape of the 10 solar0 position seems 10 0 very smooth, ! ! -1 -1 these ellipsoids as follows. For each halo we begin by diagonal- " " • 2. Question:substructures how smooth are far is awaythe dark from matter the velocity Sun distribution at the solar position? ising the moment of inertia tensor of the dark matter within the 4 4 Phase-spacespherical structure shell 6kpc in the Velocity distribution in a 2 kpc box the solar circle 10 10 mon Vmax). This gives us a first estimate of the orientation and ! ! The velocity distribution of dark matter at) 2 the solar circles is) 2 smooth, close to 2 3 for all six halos with about 200 million particles within R200.Fur-shape of-3 the1 best fitting ellipsoid. We then-3 reselect1 particles with f(v Answer: smooth,f(v no streams 10 Maxwellian0 10 0 1 1 ther details of the halos and their characteristics can be found in 6kpc Density probability distribution! around the solar circle matter distribution! near the Sun. we scale the halos in mass and radius by the constant required to 2 ) 2 5 per limits established by other experiments (see Savage et al. 2004; 1 f(v) 6 kpc < r < 10 kpc High resolution simulations of f(v The Aquarius project, 6 halos give each a maximum circular velocity of Vmax =208.49 km/s, 100 Aq-A-1 Gondolo & Gelmini 2005; Gelmini 2006, for a discussion and pos- 1 1 six galaxy MNRAShalos taken 395, from 2009 the the value for Aq-A-2. We will also sometimes refer to a coordi- Aq-A-1 siblenate solutions). system that Regardless is aligned of this,with recent the principal improvements axes of thein detector inner halo, 0 0 Aquarius4 Project 3 SPATIAL0 DISTRIBUTIONS150 300 450 600 -450 Aq-A-2-225 0 225 450 technologyand which may labels enable particles a detection by an of ellipsoidal “standard model” radius r WIMPSdefinedor as -1 Aq-A-3 -1 ell -2 v [kmsmooth s ] v1 [km s ] Parameters for the Aquarius axions within a few years. The density10 of DM particles at the Earth determinesAq-A-4 the flux of the semi-major axis length of the ellipsoidal equidensity surface on -3 1 component -3 1 simulations: Event rates in all direct detection experiments are determined DM particles passing through laboratory detectors.Aq-A-5 It is important, -3 3 which the particle sits. We determine the orientation and shape of 10 0 10 0 ! ! Poisson(64) 10 therefore, to) -1 determine not only the mean value-1 of the DM density ! = 0.25 by the local DM phase-space distribution at the Earth’s position. " " m ! these ellipsoids as follows. For each halo we begin by diagonal- ! f( -4 The relevant scales are those of the apparatus and so are extremely 8 kpc from the410 Galacticintermediate Centre, but also the fluctuations4 aroundminor this !Λ = 0.75 ising the moment of inertia tensor of the dark matter within the f(v) 2 -1 -1 mean which-3 may result from small-scale structure.-3 H0= 100 h km s Mpc small from an astronomical point of view. As a result, interpret- 3 3 spherical shell 6kpc ing null results as excluding specific regions of candidate param- ! ! mon Vmax). This gives us a first estimate of the orientation and ) 2 ) 2 population simulations2 using an SPH smoothing kernel3 adapted to the 64 etershape space of must the rely best on fitting (strong) ellipsoid. assumptions We then about reselect the particl fine-scalees with 10-6 nearest neighbours.f(v We then fit a power lawf(v to the resulting dis- 1 structure of phase-space in the inner Galaxy. In most analyses the 1 1 Answer: 6kpc