Search for Dark Ma-er with bubble chambers Orin Harris - PowerPoint PPT Presentation

Search for Dark Ma-er with bubble chambers Orin Harris Northeastern Illinois University APS DPF 2017 1

Bubble chamber: theory In a superheated fluid, bubbles will • collapse unless they are large enough (r c ) to overcome surface tension: must deposit E th in a radius less than r c à E th & E th /r c = dE/dx threshold surface tension Threshold based on theory of Seitz • (Phys. of Fluids I, 2 (1958)) vapor pressure For a given fluid: Classical Thermodynamics gives E th , r c in terms of P, T liquid pressure 2

Pressure & temperature à min energy, dE/dx threshold à sensiZve to nuclear recoils but not electron recoils 1950s-1970s Neutron calibraZon event 3

Gamma/Beta Backgrounds Gamma Rejection by Chamber 10 -2 Various PICO Detectors PICO-0.1 10 -3 U Chicago COUPP-1L 10 -4 Queen's Probability of Nucleation C 3 F 8 CF 3 I COUPP-4 PICO-2L 10 -5 PICO-60 10 -6 10 -7 10 -8 10 -9 10 -10 10 -11 Aim for this level for 1 year exposure 10 -12 0 2 4 6 8 10 12 Threshold (keV) 4

Nuclear target Response funcZons • Big advantage of bubble , , chambers is the ease of , etc changing nuclear target (lot’s of candidate refrigerants) • Previously used CF 3 I (I for SI sensiZvity, F for SD sensiZvity), now using C 3 F 8 (focusing on SD sensiZvity, low mass) A. L. Fitzpatrick, see also: 0908.2991, 1203.3542, 1211.2818, 1308.6288 5

PICO Bubble chamber operaZon Pressure expansion puts target Wait for parZcle interacZon to fluid in superheated state nucleate a bubble, recompress Buffer fluid (water) Synthetic silica jar Target fluid Hydraulic (CF 3 I/C 3 F 8 ) fluid 6 to hydraulic controller

Cameras capture stereoscopic AcousZc sensors & fast pressure bubble images @ 100 fps transducer capture sound & pressure rise from bubble growth (primary trigger) 7 50ms

AcousZc discriminaZon of α’s • Clear acousZc signature of single nuclear recoil (track < ~μm) COUPP-4 • Sound emission peaks CF 3 I Target at r bubble ≈ 10 μm • α track much larger (~40 μm) à separate nucleaZon sites à α’s several Zmes louder 8

The PICO program PICO: merger of PI CASSO • and CO UPP collaboraZons PICO-2L C 3 F 8 (2014-17) • C. Amole et al. , PICO-60 PICO-2L Phys. Rev. Le-. 114 , 231302 (2015) Phys. Rev. D 93 , 061101 (2016) PICO-60 CF 3 I (2013) • Phys. Rev. D 93 , 061101 (2016) PICO-60 C 3 F 8 (2016-17) • Phys. Rev. Le-. 118 , 251301 (2017) PICO-40L (2017-18) • PICO-500 (future) • 9

PICO-60 Cleaning Every component touching the inner volume • was cleaned against MIL-STD-1246C level 50 Post-FiltraZon ParZculate Size DistribuZon ----- Mil-Std 1246C level 100 ----- Mil-Std 1246C level 50 (Goal) Par8cles/liter ----- Mil-Std 1246C level 25 * Filter Sample Normalized by Flow Par8culate <15 µ m <25 µ m <50 µ m <100 µ m 10 <5 µ m Size Bin

PICO-60 run with blinded acousZcs Filled with 52 kg C 3 F 8 in June, 2016 • C. Amole et al ., arXiv:1702.07666 – Blind analysis on data from November 2016 and January 2017 1167-kg-days at 3.3 keV threshold 106 bulk singles in WIMP search dataset • – Consistent with 222 Rn decay rate Expected Neutron Background • – 3 mulZple bubbles in the physics data – 3:1 mulZples to singles raZo from calibraZon and simulaZon – 0-3 bulk singles would be consistent with neutrons and no anomalous background 11

Amer Opening the Box C. Amole et al ., arXiv:1702.07666 No events in signal region! AcousZc Parameter Radon chain alphas 12

Spin-dependent Limits SD WIMP-proton cross section [cm 2 ] 10 -37 PICASSO 10 -38 10 -39 SuperK IceCube Factor of 17 improvement! 10 -40 PICO-60 C 3 F 8 10 -41 10 1 10 2 10 3 WIMP mass [GeV/c 2 ] C. Amole et al ., arXiv:1702.07666 13

Moving forward: PICO-40L Eliminate buffer fluid Purpose of PICO-40L Thermal Gradient buffer liquid is to isolate the acZve liquid from the stainless parts Thermal gradient can PICO-60 ensure that target fluid near stainless parts is not acZve 14

Summary PICO-40L • PICO bubble chambers at the 40L Thermal Gradient scale are background-free • PICO dominates the search for spin- dependent WIMP-proton coupling • PICO-40L: Design changes expected to further improve bubble chamber stability and lower neutron background, deployment this year • Ton-scale PICO-500 in engineering stage, goal: data taking in 2019 15

O. Harris E. Vázquez-Jáuregui I. Lawson C. Amole, M. Besnier, G. Caria, G. Giroux, A. Kamaha, A. Noble M. Ardid, M. Bou-Cabo, I. Felis D.M. Asn er, J. Hall D. Baxter, C.E. Dahl, M. Jin, J. Zhang S. Fallows, C. Krauss, P. Bhattacharjee. P. Mitra M. Das, S. Seth S.J. Brice, D. Broemmelsiek, P.S. Cooper, M. Crisler, E. Behnke, H. Borsodi, O. Harris, R. Neilson K. Clark W.H. Lippincott, E. Ramberg, A. LeClair, I. Levine, E. Mann, M.K. Ruschman, A. Sonnenschein J. Wells R. Filgas, I. Stekl F. Debris, M. Fines-Neuschild, F. Girard, C.M. Jackson, J. Farine, A. Le Blanc, J.I. Collar, M. Lafrenière, M. Laurin, R. Podviyanuk, O. Scallon, A.E. Robinson D. Maurya, S. Priya J.-P. Martin, A. Plante, 16 U. Wichoski N. Starinski, V. Zacek

BACKUP 17

Long term • Coherent neutrino background much lower for light target compared to Xe 18

Nucleon Coupling Limits Limits on neutron vs proton spin-dependent coupling P a LUX n d a X - I I PICO-60 C 3 F 8 PICO-2L C 3 F 8 PICO-60 CF 3 I C. Amole et al ., arXiv:1702.07666 See Tovey for details: D.R. Tovey, et al. , Phys. Le-. B 488, 17 (2000) 19

Comparison to Collider C. Amole et al ., arXiv:1702.07666 20