Bubble Chambers for Dark Matter Detection Bubble Chambers for Dark - - PowerPoint PPT Presentation

Bubble Chambers for Dark Matter Detection Bubble Chambers for Dark Matter Detection : COUPP (Chicagoland Observatory for COUPP (Chicagoland Observatory for Underground Particle Physics) Underground Particle Physics) Brian Odom Brian Odom

• Sept. 12, 2007

Brian Odom TAUP 2007

Wilson Fellows: Andrew Sonnenschein Staff Scientists: Peter Cooper Mike Crisler Martin Hu Erik Ramberg Bob Tschirhart Principal Investigator: Juan Collar (spokesperson) Graduate Students: Nathan Riley Matthew Szydagis Undergraduates: Luke Goetzke Hannes Schimmelpfennig KICP Fellows: Brian Odom University of Chicago University of Chicago

The COUPP Team The COUPP Team

National Science Foundation Kavli Institute for Cosmological Physics Department of Energy

Funding Fermi National Fermi National Accelerator Accelerator Laboratory Laboratory Principal Investigator: Ilan Levine Undergraduates: Earl Neeley Tina Marie Shepherd Engineers: Ed Behnke Indiana University Indiana University South Bend South Bend

• Sept. 12, 2007

Brian Odom TAUP 2007

Wish List for a Tough Problem Wish List for a Tough Problem

Dream Detector: Dream Detector:

• Scalable

Scalable

• Cheap

Cheap

• Radiopure

Radiopure

• Good background-

Good background- rejection rejection

• Multiple active nuclei

Multiple active nuclei

• Easy to swap targets

Easy to swap targets

~ 1 recoil / kg / day ~ 1 recoil / kg / day ~ 1 recoil / ton / year! ~ 1 recoil / ton / year!

A A bubble chamber bubble chamber (bulk superheated liquid detector) (bulk superheated liquid detector) potentially fulfills all those wishes… potentially fulfills all those wishes…if it actually works if it actually works

• Sept. 12, 2007

Brian Odom TAUP 2007

Bubble Chambers for Rare Event Searches? Bubble Chambers for Rare Event Searches?

• In

In recent HEP, bubble chambers with recent HEP, bubble chambers with metallic parts metallic parts were stable were stable for for ~ 10 milliseconds…killer dead time ~ 10 milliseconds…killer dead time

• But the many of the original chambers were

But the many of the original chambers were glass glass

• Condense

Condensed matter research strongly suggests that both b d matter research strongly suggests that both bulk and lk and surface spontaneous nucleation surface spontaneous nucleation rates can be made low enough rates can be made low enough

Roger Hildebrand at UofC holding Roger Hildebrand at UofC holding the first Hydrogen bubble chamber the first Hydrogen bubble chamber

• Sept. 12, 2007

Brian Odom TAUP 2007

Try This At Home? Try This At Home?

A single A single microscopic microscopic interaction (nuclear recoil) gives a interaction (nuclear recoil) gives a macroscopic macroscopic signal (boiling) signal (boiling) The WIMP signal is just as large as the fork signal! The WIMP signal is just as large as the fork signal!

• Sept. 12, 2007

Brian Odom TAUP 2007

β and and γ Insensitivity Insensitivity

• Most experiments, after heroic cleaning and shielding, still

Most experiments, after heroic cleaning and shielding, still must cut many must cut many β, γ events events

• Bubble chambers can be operated essentially MIP-blind

Bubble chambers can be operated essentially MIP-blind

Seitz (hot spike) model:

• Sept. 12, 2007

Brian Odom TAUP 2007

Freedom to Choose Target Freedom to Choose Target

In general SUSY, channel of first In general SUSY, channel of first detection is unknown: detection is unknown:

• Spin-dependent

Spin-dependent: use fluor : use fluorine ne

• Spin-independent

Spin-independent: use : use something heavy something heavy We use C We use CF3I, for excellent , for excellent sensitivity in both channels. sensitivity in both channels. Other advantages of CF Other advantages of CF3I : I :

• Inexpensiv

expensive (40 USD / kg) e (40 USD / kg)

• Near room temperature

Near room temperature

• peration (~
• peration (~ 40 C)

40 C)

• Safe (non-toxic, fire extinguisher)

Safe (non-toxic, fire extinguisher)

• Sept. 12, 2007

Brian Odom TAUP 2007

Freedom to Swap Target Freedom to Swap Target

Dark blue: LSP (SUGRA) Light blue: LKP

(Bertone, C (Bertone, Cerdeno deno, C Collar, llar, and O and Odom,

• m,

to appear in to appear in PRL, PRL, arXiv:07 arXiv:0705 05.2 .2502) 502)

Swapping Target Liquids: Swapping Target Liquids:

• Upon discovery, makes ~ orthogonal cuts

Upon discovery, makes ~ orthogonal cuts in in parameter parameter space pace

• Alternatively, use different ta

Alternatively, use different targets for neutron rejection. rgets for neutron rejection. (Response of CF3I and C3F8 to ne (Response of CF3I and C3F8 to neutrons is very similar, but, for utrons is very similar, but, for example, SI WIMP response is very different) example, SI WIMP response is very different)

• Sept. 12, 2007

Brian Odom TAUP 2007

2 kg Prototype Chamber 2 kg Prototype Chamber

Bulk CF3I touches only the quartz Bulk CF3I touches only the quartz

Movie posted at http://kicp.uchicago.edu/~odom/presentations/bubble3.avi

• Sept. 12, 2007

Brian Odom TAUP 2007

Leaving “Normal” Leaving “Normal” BC Mode Far Behind BC Mode Far Behind

Decreasing superheat Decreasing superheat

• Muon tracks

Muon tracks are visible only at high superheats are visible only at high superheats

• We operate at low superheat, MIP blind

We operate at low superheat, MIP blind

• 1 nuclear recoil = 1 bubble

1 nuclear recoil = 1 bubble Muon tracks Muon tracks (Muon-blind) (Muon-blind) Nuclear recoil Nuclear recoil

• Sept. 12, 2007

Brian Odom TAUP 2007

Stereo View for Bubble Position Stereo View for Bubble Position

Position reconstruction is important for Position reconstruction is important for background rejection background rejection, ,

• f both
• f both wall events

wall events and and neutron events neutron events (multiple scattering) (multiple scattering)

• Sept. 12, 2007

Brian Odom TAUP 2007

Operation at 300 m.w.e., Fermilab Operation at 300 m.w.e., Fermilab

• Sept. 12, 2007

Brian Odom TAUP 2007

Demonstration of MIP-Blindness Demonstration of MIP-Blindness

• Intri

Intrinsi sic γ rejection rejection better than better than 10 10-10

• 10 at 10

at 10 keV threshold (best keV threshold (best measured MIP-rejection) measured MIP-rejection)

• No cuts required!

No cuts required!

• No need for

No need for β, γ shielding or attention to shielding or attention to β, γ radiopurity.

• radiopurity. E.g.

E.g.

14 14C ar

C are e O O (100 / kg- (100 / kg-day) day)

• Sept. 12, 2007

Brian Odom TAUP 2007

Neutron calibration, Neutron calibration, in situ in situ

• Switchable Am/Be

Switchable Am/Be source yields source yields 5 +/- 5 +/- 0.5 n /s when 0.5 n /s when

• n and
• n and O

O (0.2 n/day) (0.2 n/day) when off when off

• Left:

Left: blind absolute blind absolute comp compar arison

• n,

, consistent with 100% consistent with 100% efficiency efficiency

• Moderated

Moderated spectrum produces spectrum produces rec recoils approximating

• ils approximating

WIMP spectrum WIMP spectrum

• Sept. 12, 2007

Brian Odom TAUP 2007

Current Wall Background: Current Wall Background: α-Emitters

• Emitters
• Wall rate

Wall rate (0.9 / (0.9 /cm cm2/day) OK for small vessels /day) OK for small vessels (200 /day for 2 kg chamber) (200 /day for 2 kg chamber)

• γ-counting of our Ge-214 natural fused quartz
• counting of our Ge-214 natural fused quartz

found U (Th) at typical level of found U (Th) at typical level of 50 (30) ppb 50 (30) ppb — consistent with 100% of wall-event rate consistent with 100% of wall-event rate

• Commercial

Commercial α-counting gives consistent rate

• counting gives consistent rate
• Next-generation vessels

Next-generation vessels made from synthetic made from synthetic fused silica, with expected U, Th level fused silica, with expected U, Th level < 10 ppt < 10 ppt

• New vessels also undergo extra quartz etch

New vessels also undergo extra quartz etch before final annealing and are then sealed, to before final annealing and are then sealed, to guard against embedded Rn progeny guard against embedded Rn progeny

• Sept. 12, 2007

Brian Odom TAUP 2007

Current Bulk Background: Radon & Progeny Current Bulk Background: Radon & Progeny

Bulk background is consistent Bulk background is consistent with 100% Rn and progeny with 100% Rn and progeny α’s ’s 1. 1. Flat rate with sharp onset at predicted value Flat rate with sharp onset at predicted value 2. 2. Analysis of time correlat Analysis of time correlation between events supports ion between events supports 100% Rn & proge 100% Rn & progeny, 100% efficie ny, 100% efficiency ncy Predicted Predicted α onset

• nset

Predicted plateau Predicted plateau Next chambers: Next chambers: 1. 1. Non-thoriated welds Non-thoriated welds 2. 2. Metal seals against Rn Metal seals against Rn

• Sept. 12, 2007

Brian Odom TAUP 2007

Any WIMPs in the Data? Any WIMPs in the Data?

• Total exposure of

Total exposure of 250 kg-days 250 kg-days (Dec ’05 – (Dec ’05 – Nov ’06), with live-time

• v ’06), with live-time

fraction reaching 8 fraction reaching 80%. %. 51 kg-liv 51 kg-livedays edays used for WIMP analysis. used for WIMP analysis.

• Dashed curves:

Dashed curves: nu null hypoth hypothesis is function (NHF)--only Rn & progeny function (NHF)--only Rn & progeny

• Solid lines:

Solid lines: expected WIMP response expected WIMP response function (WRF) function (WRF) for for σSD(p)

SD(p)=3 pb

=3 pb

• Perform 2-parameter fit a*NHF +

Perform 2-parameter fit a*NHF + b*WRF (constrain b b*WRF (constrain b≥0). b=0 is 0). b=0 is generally favored. (Error matrix generally favored. (Error matrix analys analysis is, checked agains , checked against MIN t MINUIT UIT, i , is s used to obtain 90% C.L.) used to obtain 90% C.L.)

• Cross-section limits obtained from

Cross-section limits obtained from weigh weighted mean of WRF parameter ted mean of WRF parameter “b”, from 3 data sets “b”, from 3 data sets Q: How much WIMP signal could be Q: How much WIMP signal could be hiding beneath the radon & progeny? hiding beneath the radon & progeny? Note: these are Note: these are integrated energy spectra integrated energy spectra

• Sept. 12, 2007

Brian Odom TAUP 2007

COUPP (2007) Exclusion Limits COUPP (2007) Exclusion Limits

The COUPP 2 kg prototype The COUPP 2 kg prototype detector, even with minimal detector, even with minimal measures against radon, sets measures against radon, sets competitive SD(p) limits competitive SD(p) limits Worth noting: new limits are Worth noting: new limits are place placed in the low-mass re d in the low-mass region gion favored by a SD interpretation favored by a SD interpretation

• f the DAMA/NaI signal
• f the DAMA/NaI signal

• Sept. 12, 2007

Brian Odom TAUP 2007

COUPP (2007) Exclusion Limits COUPP (2007) Exclusion Limits

SD(n) and SI limits are SD(n) and SI limits are not not yet yet as interesting as interesting …but data already coming …but data already coming in from the new fill (2 kg in from the new fill (2 kg chamber, with better seals chamber, with better seals against Rn and no against Rn and no thoriated weld lines) look thoriated weld lines) look very promising… very promising…

• Sept. 12, 2007

Brian Odom TAUP 2007

Under construction: Under construction: 20 kg Windowless Chamber 20 kg Windowless Chamber

Pressure vessel is off-the-shelf Pressure vessel is off-the-shelf water water

• pipe. Readout is from internal
• pipe. Readout is from internal

cameras and encapsulated piezos. cameras and encapsulated piezos. 20 kg synthetic fused 20 kg synthetic fused silica vessel, sealed silica vessel, sealed against exposure to Rn against exposure to Rn

• Sept. 12, 2007

Brian Odom TAUP 2007

Under construction: Under construction: 20 kg Windowless Chamber 20 kg Windowless Chamber

4π water shielding water shielding and muon veto and muon veto Shielding installation at Shielding installation at TARP tunnel (300 mwe) TARP tunnel (300 mwe) near UofC near UofC

• Sept. 12, 2007

Brian Odom TAUP 2007

Under construction: 60 kg Chamber Under construction: 60 kg Chamber

For installation in NUMI For installation in NUMI tunnel, Fermilab. tunnel, Fermilab. 30 cm x 1 meter 30 cm x 1 meter inner vessel inner vessel

• Sept. 12, 2007

Brian Odom TAUP 2007

Conclusions Conclusions

• Scalable

Scalable: liquid target with : liquid target with simple instrumentation simple instrumentation

• Low cost

Low cost (<1000 USD/kg) (<1000 USD/kg)

• Outstanding

Outstanding γ-rejection

• rejection
• Single concentration: reducing

Single concentration: reducing α- emitters emitters to ~10 to ~10-17

• 17 (achieved

(achieved elsewhere) probes most SUSY elsewhere) probes most SUSY mode models ls

• 2 k

2 kg prototype prototype already already contributes to SD(p) limits, with contributes to SD(p) limits, with lower background run underway lower background run underway

• Larger masses

Larger masses coming (20 and coming (20 and 60 kg modules under construction) 60 kg modules under construction)