Prospective for low mass dark matter with LUX and LZ Paolo Beltrame University of Edinburgh on behalf of the LUX and LZ Collaborations
Direct detection ? Z,A Z,A - Dark Matter Weakly Interactive Massive Particle (WIMP) in direct search experiments - Nuclear Recoil (NR) in the target material, ~ keVnr energy deposit - Electron Recoil (ER) giving most of the background (keVee) - Standard WIMP searches (> 10 GeV/c 2 mass)… but not only P. Beltrame - Prospect in Low Mass Dark Matter (Munich, 30/11 - 1/12 2015) 2
Liquid Xenon - Radio-pure noble gas - Liquid detectors easily scalable - Scalar WIMP-nucleus: A 2 - Self shielding from external enhancement background sources - Natural Xe ~50% odd isotopes: - Combining the two => ultra-low- spin-dependent interactions background inner volume P. Beltrame - Prospect in Low Mass Dark Matter (Munich, 30/11 - 1/12 2015) 3
Dual phase Xe TPC - Primary scintillationlight (“S1”) at the particle - Liquid Xe interaction vertex - Electrons extracted from the interaction drifted by electric field to the surface and into the Gas Xe. Proportional scintillationlight (“S2”) Ø Multiple scatter event identification (via S2) Ø 3-D localisation of each vertex (via S1 and S2) Ø ER/NR discrimination (via S2/S1) Ø Sensitivity to single electrons (S2) P. Beltrame - Prospect in Low Mass Dark Matter (Munich, 30/11 - 1/12 2015) 4
The LUX Collaboration Large Underground Xenon experiments Brown Richard Gaitskell PI, Professor SD School of Mines Simon Fiorucci Research Associate PI, Professor Xinhua Bai Samuel Chung Chan Graduate Student Doug Tiedt Graduate Student Dongqing Huang Graduate Student Will Taylor Graduate Student SDSTA Casey Rhyne Graduate Student James Verbus Graduate Student David Taylor Project Engineer Imperial College London Mark Hanhardt Support Scientist Henrique Araujo PI, Reader SUNY at Albany Tim Sumner Professor Alastair Currie Postdoc PI, Professor Matthew Szydagis Graduate Student Adam Bailey Jeremy Mock Postdoc Khadeeja Yazdani Graduate Student Steven Young Graduate Student Lawrence Berkeley + UC Berkeley Texas A&M PI, Professor Bob Jacobsen Murdock Gilchriese Senior Scientist James White † PI, Professor Senior Scientist Kevin Lesko PI, Professor Robert Webb Peter Sorensen Scientist Graduate Student Rachel Mannino Scientist Victor Gehman Paul Terman Graduate Student Postdoc Attila Dobi UC Davis Daniel Hogan Graduate Student Graduate Student Mia Ihm Kate Kamdin Graduate Student PI, Professor Mani Tripathi Kelsey Oliver-Mallory Graduate Student Britt Hollbrook Senior Engineer Development Engineer John Thmpson Lawrence Livermore Dave Herner Senior Machinist Ray Gerhard Electronics Engineer Adam Bernstein PI, Leader of Adv. Detectors Grp. University of South Dakota University of Edinburgh Postdoc Aaron Manalasay Staff Physicist Kareem Kazkaz Postdoc Scott Stephenson Brian Lenardo Graduate Student Alex Murphy PI, Reader James Moard Graduate Student Dongming Mei PI, Professor LIP Coimbra Graduate Student Sergey Uvarov Paolo Beltrame Research Fellow Chao Zhang Postdoc Graduate Student Jacob Cutter James Dobson Postdoc Graduate Student PI, Professor Angela Chiller Isabel Lopes Maria Francesca Marzioni Graduate Student Assistant Professor Chris Chiller Graduate Student Jose Pinto da Cunha UC Santa Barbara Tom Davison Graduate Student Vladimir Solovov Senior Researcher Auxiliary Researcher Francisco Neves Harry Nelson PI, Professor Yale University of Maryland Alexander Lindote Postdoc Professor Mike Witherell Claudio Silva Postdoc Susanne Kyre Engineer Carter Hall PI, Professor SLAC Nation Accelerator Laboratory Daniel McKinsey PI, Professor Dean White Engineer Richard Knoche Graduate Student Research Scientist Ethan Bernard Carmen Carmona Postdoc Jon Balajthy Graduate Student Markus Horn Thomas Shutt PI, Professor Research Scientist Scott Haselschwardt Graduate Student PI, Professor Blair Edwards Postdoc Dan Akerib Curt Nehrkorn Graduate Student University of Rochester Kim Palladino Project Scientist Scott Hertel Postdoc Melih Solmaz Graduate Student Research Associate Postdoc Tomasz Biesiadzinski Kevin O’Sullivan Christina Ignarra Research Associate University College London PI, Professor Elizabeth Boulton Graduate Student Frank Wolfs Research Associate Senior Scientist Wing To Wojtek Skutski Nicole Larsen Graduate Student Graduate Student Graduate Student Graduate Student Rosie Bramante Chamkaur Ghag PI, Lecturer Eryk Druszkiewicz Evan Pease Wei Ji Graduate Student Dev Ashish Khaitan Graduate Student Graduate Student Lea Reichhart Postdoc Brian Tennyson T.J. Whitis Graduate Student Mongkol Moongweluwan Graduate Student Lucie Tvrznikova Graduate Student Sally Shaw Graduate Student P. Beltrame - Prospect in Low Mass Dark Matter (Munich, 30/11 - 1/12 2015) 5
P. Beltrame - Prospect in Low Mass Dark Matter (Munich, 30/11 - 1/12 2015) 6
Ø 47 cm diameter by 48 cm height dodecagonal “cylinder” Ø 370 kg LXe total, 250 kg active region Ø 61 PMTs on top, 61 on bottom. Low radiogenic BGs and VUV sensitivity Ø Xenon pre-purified via chromatographic separation, residual krypton levels to 3.5 ± 1 ppt (g/g) Ø Liquid is continuously recirculated (1/4 tonne per day) to maintain chemical purity Ø Ultra-low BG titanium cryostat P. Beltrame - Prospect in Low Mass Dark Matter (Munich, 30/11 - 1/12 2015) 7
WIMP search P. Beltrame - Prospect in Low Mass Dark Matter (Munich, 30/11 - 1/12 2015) 8
WIMP search (Charge/Light) (Light ~ Energy) P. Beltrame - Prospect in Low Mass Dark Matter (Munich, 30/11 - 1/12 2015) 9
WIMP search - Exposure: 85.3 live days, PRL 112, 091303 (2014) 118 kg fiducial mass - Obs. bkg. events: 160 - Drift field: 181 V/cm - Analysis 4-parameter profile likelihood, p-value of 35% consistent with backgrounds 7.6 x 10 -46 cm 2 at 33 GeV/c 2 LUX first results conservative assumption of energy cut-off at 3 keVnr: i.e. below 3 keVnr no S1 and no S2 P. Beltrame - Prospect in Low Mass Dark Matter (Munich, 30/11 - 1/12 2015) 10
WIMP sensitivity http://indico.hep.manchester.ac.uk/contributionDisplay.py?contribId= 133&sessionId=17&confId=4221 P. Beltrame - Prospect in Low Mass Dark Matter (Munich, 30/11 - 1/12 2015) 11
WIMP sensitivity http://indico.hep.manchester.ac.uk/contributionDisplay.py?contribId= 133&sessionId=17&confId=4221 Decreasing this response cutoff from 3 keV to < 1 keV provides access to a factor of 8000 more signal at M = 6 GeV P. Beltrame - Prospect in Low Mass Dark Matter (Munich, 30/11 - 1/12 2015) 12
Nuclear Recoil events New detector response calibration for NR: DD generator Monochromatic, collimated 2.45 MeV neutrons - Double scatters along beam line inside LUX. Angle gives deposited energy. => Absolute calibration of ionisation response: Q Y - Apply ionisation scale to single scatter => Absolute calibration of scintillation response: L Y P. Beltrame - Prospect in Low Mass Dark Matter (Munich, 30/11 - 1/12 2015) 13
Charge yield 1. Q y : linearity between deposited energy and ionisation signal. Measured down to 0.8 keVnr 3 keVr cut-off (2013 analysis) P. Beltrame - Prospect in Low Mass Dark Matter (Munich, 30/11 - 1/12 2015) 14
Light yield 2. L Y : linearity between deposited energy and scintillation signal. Measured down to 1.2 keVnr 3 keVr cut-off (2013 analysis) P. Beltrame - Prospect in Low Mass Dark Matter (Munich, 30/11 - 1/12 2015) 15
Electron Recoil events New detector response calibration for ER: CH 3 T injection - Light and charge yields to ~1 keVee - Detection efficiency vs energy - Informative of the background shape - “leaks” down into NR S2/S1 region, as a function of S1 from [0.2 - 5] keVee - Uniformly distributed, used with 83m Kr for fiducial volume evaluation P. Beltrame - Prospect in Low Mass Dark Matter (Munich, 30/11 - 1/12 2015) 16
ER and NR events in S2/S1 space 17
Light DM 1. WIMP search : - S1+S2 exploiting new NR calibration data (i.e. removing hard threshold at 3 keV) - S2-only: O(1 GeV/c 2 ) vanilla WIMPs 2. Axion-like particles (~keV): - S1+S2 exploiting new ER calibration data 3. Hidden-sector U(1)’ models* : - S2-only exploiting new ER calibration data * PRL 109, 021301 (2012), PRD 85, 076007 (2012) P. Beltrame - Prospect in Low Mass Dark Matter (Munich, 30/11 - 1/12 2015) 18
S2-only - S2 signal sensitive to smaller energy depositions: NR thresholds (<1 keV) too feeble for a detectable S1 - Ionisation channel sensitivity to individual electrons. Threshold for analysis at > 2 e - - Interaction point localization: S2 (x, y) and longitudinal spread for z-coordinate. P. Beltrame - Prospect in Low Mass Dark Matter (Munich, 30/11 - 1/12 2015) 19
Charge lost in the LXe Max. charge loss Experiment to impurities XENON10 ~0% +HV GXe XENON100 ~40% 0V O 2 LUX ~30% O 2 O 2 O 2 LXe e- e- e- e- e- e- O 2 O 2 e- O 2 O 2 O 2 O 2 -HV P. Beltrame - Prospect in Low Mass Dark Matter (Munich, 30/11 - 1/12 2015) 20
Charge lost in the extraction Electron Experiment extraction efficiency XENON10 ~100% +HV GXe e- e- XENON100 ~100% e- e- 0V e- e- e- LUX ~50% LXe -HV P. Beltrame - Prospect in Low Mass Dark Matter (Munich, 30/11 - 1/12 2015) 21
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