Optical Time Projection Chambers:
A New Look at Dark Matter & Neutrino
Physics
Jocelyn Monroe,
Royal Holloway University of London
Department of Physics Seminar,
Kyoto University
Dec. 9, 2016

Outline
Physics Motivation
Detector Development for Dark Matter-Experimental Considerations-Direction Measurement Progress in DMTPC
Outlook for Large Detectors-Geo-Neutrino Sensitivity-HPTPC for Neutrino Physics

RHUL Jocelyn Monroe

Dec. 9, 2016

Dark Matter is ~25% of the energy density of the universe.

RHUL Jocelyn Monroe

Dec. 9, 2016

What do we know about Dark Matter?

optically dark
density ~ 0.3 GeV/cm3
dark matter particle
mass: ~unknown
interactions: very weak,~collision-less~150

RHUL Jocelyn Monroe

Dec. 9, 2016

Direct Detection
Signal:χN ➙χNχχ

Backgrounds:
γ e- ➙ γ en N➙ n N
N ➙ N’ + α, eν N➙ ν N

γ
RHUL Jocelyn MonroeγDec. 9, 2016

WIMP Scatteringχ1
ED = mD v22χ

kinematics: v/c ~ 8E-4!
recoil angle strongly correlatedwith incoming WIMP directionr =q2 = 2mT Erecoil

4mD mT(mD + mT )2N

N
Erecoil = ED r

(1

cosq)
2

Spin Independent:χscatters coherently off ofthe entire nucleus A: σ~A2
D. Z. Freedman, PRD 9, 1389 (1974)

Spin Dependent:
mainly unpaired nucleons contributeto scattering amplitude: σ~ J(J+1)
detector requirements: measure recoil energy, time, +angle
RHUL Jocelyn Monroe

Dec. 9, 2016

Observable: Recoil Energy
χ

10

Sc

χ

He

Io
n

iza

at

100 GeV/c2 WIMP mass
1E-45 cm2 WIMP-nucleon SI σ

in

till
a

tio

n

1

0.1

tio
n

~

detector requirements: ~1-10s of keV energy threshold, background rates << 1/kg-yr
RHUL Jocelyn Monroe

Dec. 9, 2016

The Dark Matter Wind apparently“blows” from Cygnus
directional detection:
search for a dark matter source

Daily direction modulation:
asymmetry ~ 20-100%
in forward-backward
event rate.
Spergel, Phys. Rev. D36:1353 (1988)

Unambiguous proof:
Correlation of WIMP-induced nuclear recoil signal with galactic motion
RHUL Jocelyn Monroe

Dec. 9, 2016

Directional Detection Goal

Events /kg / day

if you can reconstruct the energy and angle of the recoil nucleus,
you have a dark matter telescope
0.18
0.16
0.14
0.12
0.1
0.08
0.06
0.04
0.02
0
Re 0 20
coi 400.8 1
0.6
l K 6080
ine 100
0.20.4 ψLAB )tic 120
0(-0.2
En 140Cos-0.4
erg 160y (k180200 -1-0.8-0.6
eV)

A. M. Green, B. Morgan,
astro-ph/0609115

simulated reconstructed dark mattersky map: search for anisotropy
Signal characteristics:(i) forward-backward asymmetry in galactic frame, (ii) sidereal modulation in lab
RHUL Jocelyn Monroe

Dec. 9, 2016

Outline
Physics Motivation
Detector Development-Experimental Considerations for Dark Matter Searches-Direction Measurement Progress in DMTPC
Outlook for Large Exposure-Geo-Neutrino Sensitivity-HPTPC for Neutrino Physics

RHUL Jocelyn Monroe

Dec. 9, 2016

Optimization

how many events to detect the dark matter wind?
No background, 3-d vector read-out, ET = 20 keV

Detector Properties:
energy thresholdbackgroundreconstruction(2D vs. 3D)
vector or axialreconstruction*Perfect Case(no detector effects)

A. M. Green, B. Morgan,

Astropart.Phys.27:142-149,2007

J. Billard, F. Mayet, D. Santos,
EAS Publ.Ser.53 (2012) 67-75

do not need “zero background”
for directional detectors
simulation with
100RHUL
signal,Jocelyn
100 background
MonroeF. Mayet, JM, et al. arXiv:1602.03781
Dec. 9, 2016

TPC Directional Detectors

χ

e

-V

F
F

C

CF4+

F

CF4+ CF +
4

F

e-

CF4+
e-

e-

Electric
Field

e+V

χ
RHUL Jocelyn Monroe& electron current

Dec. 9, 2016

Directional R&D Around the WorldDRIFTNEWAGEDRIFT: MWPC readout, operating 0.8m3
detector in Boulby since 2001. Negativeion drift of CS2+CF4.

S. Burgos et al., Astropart. Phys. 28, 409 (2007)

NEWAGE: mu-PIX readout of CF4 target,
in Kamioka. First directional limit.
K. Miuchi, et al., Phys.Lett.B654:58-64 (2007)

MIMAC

MIMAC: micromegas readout of CF4target, in Modane. Focus on low energy.
D. Santos, et al., J. Phys. Conf. 65, 021012 (2007)

DMTPC

DMTPC: optical (CCD) and charge
readout of CF4 targe, commissioning 1m3
module. 2D + 1D, focus on vector direction.
D. Dujmic, JM, et al., NIM A 584:337 (2008)CYGNUS: coordination of directional R&D

plus R&D on fine-grained emulsions, pixel chips, high P gas, biological detectors, C nanotubes, ++RHUL Jocelyn Monroe

Dec. 9, 2016

OpticalReadout(DMTPC)

Photon Signal

χ

CCD
e

-V

ChargeReadout(NEWAGE,MIMAC)

χ+V

Electron/Ion
Signal& electron
current

MWPC
Readout
collaboration (DRIFT)

Directional Detection
Whitepaper: arXiv:0911.0323
DRIFT
RHUL Jocelyn Monroe

Dec. 9, 2016

Dark Matter-Induced Recoil Signal Direction
distribution of signal events determined by:1)

1. angular resolution of elastic scattering
2. dark matter velocity dispersion+σθ = ~30o2)=
RHUL Jocelyn Monroe

for 100 GeV WIMPs, need ~50 keV energy
threshold for direction anisotropy at 3σ

Dec. 9, 2016

Impact of Detector Physics on Signal Directionality
recoil kinematics:+ straggling:σθ of recoilσθ = ~30o2) +diffusion:σθ ~30o@ 50 keV

RHUL Jocelyn Monroe

direction,
relative toinitial track
direction~25o @ 50 keV3) + TPC
gain and
500 umreadoutpitch
σθ ~35o@ 50 keV
Dec. 9, 2016

Backgrounds inDirectional Detectors

MC

Three strategies:
1. range vs. energy
2. tracking (106 electron rejection)
3. angular distribution(important for ν-N coherent scattering!)

F

α

e-

JM, P. Fisher, Phys. Rev. D 76:033007 (2007)

D. Snowden-Ifft

40 keV
nuclearrecoils

15 keValphas
13 keV electrons

RHUL Jocelyn Monroe

Dec. 9, 2016

Readout Requirements: Segmentation and Low Noise
At 50 keV, F recoil track lengthis 1 mm (@ 60 Torr CF4),
2.5 mm (@ 30 Torr CF4).
As the F travels, it loses energy
to the medium, which hassignificant fluctuations (straggling)--- F recoil 60 Torr
- -F recoil 30 Torr--- alpha 60 Torr
- -alpha 30 Torr

To determine the track angle
requires > 2 measurements along
the track, and in the presence ofstraggling, readout noise, etc.
require more.
need >500 um resolution,
for direction measurement
at 50 keV recoil energy.

given quenching and W for CF4, primary signal size of O(102 -103) e- / track
RHUL Jocelyn Monroe

Dec. 9, 2016

Timeline of Optical TPCs (using CCDs)
1988 Masek et al., dark
matterwith
UV
lens+ imageintensifier + CCD in
1988:
CCD
cost
(my
estimate)
0.05$/channeln dataP-10/CH4 + TEA, MWPC + 4.5 kG B field PRL73 8 (1994) 1067
1988 Charpak, Breskin et al., UV RICH, multi-stage MWPC + intensifier + CCD
Nucl. Instrum. Methods A 273 (1988) 798, IEEE Trans.Nucl.Sci. 35 (1988) 483-486

2002 Fraga et al., thermal neutron imaging with CCD readout of GEMs
Nucl. Instrum. Methods A 478 (2002) 357

CCD2006 Weissman et al., (O-TPC) nuclear astrophysics cross sections with multi-stage
MWPC + image intensifier + CCD in CO2 (80%) + N2 (20%) mixtures
J. Instrum. 1 (2006) P05002

2007 Dujmic et al., (DMTPC) dark matter directional detection, with mesh-based
amplification region + optical lens + CCD, in CF4 mixtures
Nucl.Instrum.Meth. A584 (2008) 327-333

2014 Phan et al., dark matter directional detection, GEMs + CCD in SF6
Physics Reports 662 (2016) 1-46

2016 CERN GDD (Reindl, Resnati et al.), MPGDs + CCD studies with RD51
https://indico.cern.ch/event/568177/
RHUL Jocelyn Monroe

alpha data
2016: CCD cost (my estimate) 0.005$/channel)

Dec. 9, 2016

Dark Matter Time Projection
Chamber (DMTPC) Principle

1. primary ionization encodes
track direction via dE/dx profileFχ
e30TorrEF

2. drifting electrons preserve dE/dx
profile if diffusion is smalle-

3. multiplication in amplification
region produces e- + scintillation

0V

on
r
t
u
e
n
t)
d
(
beam

0.005$/
channelCounts+3kV

CCD
cameraPix

minimum wetted materials
RHUL Jocelyn Monroe

D. Dujmic, JM et al.,
NIM A 528 (2008) 327

el
N

um
b

er

(Y

)

)

Pi

er (X
b
m
u
xel N

Dec. 9, 2016

M ~ (Voutx1.4pC/V) / (5.9keV/W)
W = 33.8 +/- 0.4 eV(I. Wolfe S.B.thesis)

d
cte
pe

Multiplication calibrated with
Fe-55, anode signal amplitude

Fe-55
ExpectedEx

Charge Readout

MeasureSparksAnode Voltage (V)cartoon of electron vs. NR
Mesh signal readout with ns-risetime
amplifier, to measure Δz and for PID
RHUL Jocelyn Monroe

Dec. 9, 2016

CF4 Scintillation
countsratio of scintillation to ionizationin avalanche determines optical ‘gain’
measurement 140-180 Torr,
result: γ/e- = 0.34 +/- 0.04
A. Kaboth, JM, et al., NIM A 592:63-72 (2008)

PhotonSignalOut

CF4 spectrum well-matched to CCD QE
CCD
range

RHUL Jocelyn Monroe

Dec. 9, 2016

CCD Readout

CCD Noise Data

ADU/keV

Total optical system gain:

1x1 bin2x2 bin
4x4 bin

Data

Simulation

F

Increasing gain + track length withlower pressure, but decreasing mass!

αe-Key to identifying low energy tracks is
S:N per pixel, @50 keVr want S:N >10
RHUL Jocelyn Monroe

Dec. 9, 2016

Directionality I

γ<0n

CCD readout of 100 torr
TPC with MWPC
2D angle + head-tailfrom light asymmetry(measure skewness)

1st DMTPC Prototype

Dujmic et al., NIM A584:327-333 (2008)

Recoil direction

Signed cosine (E>200 keV), 5 cm drift
Dujmic, et al., NIM A584:327-333 (2008)

pixel # x
Resolution (deg)σqchallenge to scaling up: diffusion!

σ2 = (D/µ) 2 zDRIFT / E
Christophorou et al., J. Phys. Ref. Chem. Data (1996)• Cf-252 Data-- MC

RHUL Jocelyn Monroe

E/NDec. 9, 2016
[Td]

Light readout

F
0V
+V

e

-

CCD

n calibration data

10L active volume,
20 cm drift,
CCD and charge
readout of 2 TPCs,
75 torr CF4
Chargereadout

Voltage-V

pixel Y

2nd Prototype

pixel X
mesh signal
anode signal

Charge-V

Light readout

time (s)goal: charge and light = reject backgrounds + 3D R&D
RHUL Jocelyn Monroe

Dec. 9, 2016

Cu Mesh, 256 um pitch

MWPC

Pixel Number (X)~28cm

Pixel Number (Y)CCD
readout
area

Pixel Number (Y)Amplification Region

Mesh

D. Dujmic et al., Astropart. Phys. 30 (2008)eSS

SS or Cu mesh

Pixel Number (X)G10Resistive separators, dia=0.5mm, every 2.5cm
RHUL Jocelyn Monroe

20x smaller pitch,
10x larger gain, 1->2DDec. 9, 2016

CCD Length and Energy Calibration
illuminate with Co-57 (122,137
keV) andneutronCs-137 (662 keV) for length calibrationenergymeasure optical plate scale by comparing
features in gamma data with photo
typically ~140-170 um/pixel(then bin 2x2 to 4x4 before readout)

Energy Ca-V

α sources for energy calibration (4.4 MeV)-V
measuregain (ADU/keVee) by comparing
α energy measured in external solid state
detector with energy in CCD, at track end:
typical gain ~ 20-40 ADU/keV
RHUL Jocelyn Monroe

Example image

Dec. 9, 2016

“WIMP” Calibration

100keV recoil angle

Neutron elastic scattering mimics dark
matter recoils, and most neutrons below~4 MeV (n,alpha) production threshold

minimum
recoilenergydetected:
30-50 keV

Cf-252 MC(Hitachiquenchingmodel)

Energy and recoil angle distributions
similar to dark matter induced recoils
RHUL Jocelyn Monroe

Projected Range (mm)Cf-252 (~mCi), AmBe, and d-t n at surface,
AmBe (8.9 uCi) source undergroundneutronenergySourceRecoil angle

14.1 MeV
neutrons

80deg

Neutrons fromAmBe

~68 deg (avg)

Neutrons from
Cf252

~57deg (avg)

200GeV WIMP

~43deg (avg)

10He• 10L Surface
8

Cf-252 Data-- SRIM MC

90
80

C

70
60

6

50

F

4

40
30
20

2

10
00

100

200

300 0

Recoil Energy (keV)

Dec. 9, 2016

Projected Range (mm)Backgrounds, CCD Readout
20

15

10

Cf252 Data
“WIMP” Data

500

CCD artifacts:same position as
sparksAlphas:edge crossing

200

400

600

800

Visible Energy (keV)“Cosmics”: one hot pixel, large cluster rms
Cf252
MC

Cf252
Data

104 rejection of backgrounds from range vs. energy
S. Ahlen, et al., Phys. Lett. B 695 (2011)

RHUL Jocelyn Monroe

Dec. 9, 2016

Background Rejection with Charge
optical AND charge readout rejects
CCD artifact AND gamma backgrounds
J. Lopez, JM, et al., NIM A 696 (2012) 121(J. Lopez)>1.1E-5 (90% CL) γ rejection from rise time vs. E:~102 rejection from Echarge vs. ECCD:

surfacecalibration data

RHUL Jocelyn Monroe

Dec. 9, 2016

3D R&D
tracking in z (drift direction):

anode Vmesh V• angled alpha calibration source
produces tracks of known Δzcharge:• measure mesh signal rise time
• find similar tracking resolution in Δz(J. Lopez)(from charge) as in x-y (from CCD)
towards
anode

J. Lopez, JM, et al., NIM A 696 (2012) 121

light:• measure PMT signal pulse
away from
anode

width
• pulse width varies with Δz,
shape varies with +/-Δz

R&D on identifying cathodeevents using PMT readout
RHUL Jocelyn Monroe

Dec. 9, 2016

Direction Calibration
Need a source of known energy and angle

neutronenergy3rd prototype,4 cameras,
25 cm drift,
20L active vol.
S. Henderson, PhD thesis (2013)

But, neutron scattering kinematics
produce wide range of angles, andneutrons are hard to collimate.

Cf-252 MC

Angled alpha calibration:• only track ends in active region,
can tune energy ~100 keVee• tune angle by rotating collimator
RHUL Jocelyn Monroe

Dec. 9, 2016

Track Reconstruction

hypothesis:

Measure energy from track intensity integral
Make use of the known profile of nuclear
recoils from the Bragg curve to(1) fit for the track parameters(range, angle)(2) fit for the head-tail (H-T)(3) assign confidence in H-T
determination with likelihood
ratio of two possible senses,
cut on confidence

convolve withgaussian(1)(1)

ChargeC, Deaconu, PhD thesis (2015)(2)
J. Lopez, PhD thesis (2014)

RHUL Jocelyn Monroe

Dec. 9, 2016

diffusion has a big impact!
• measure with 20, 25 cm drift• find direction reconstruction

depends most on track length,
range/width>3 for head-tail ID,

C. Deaconu, PhD (2015), Phys. Procedia
261 (2015) 39

20 cm drift:
φ - φsource (rad.)Directionality II

10L
Data

2

1D “sky map”
for 252Cf, and“WIMP ” data(80-200 keV)

300
250
200

0

MC: 40oresolution at
80 keVr

150• R&D Data
-- MC

-2

100
50

25 cm drift:

100

150

A. Kaboth PhD
thesis (2012)

200

Recoil Energy (keV)
C. Deaconu, TAUP 2013 Proceedings

Data:(But! lower P = lower dE/dx)
RHUL Jocelyn Monroe

Aug. 11, 2014

Diffusion Measurement
Measure track width fromalpha source at known
heights in detector,✓ ◆✓◆• fit for two terms:
D
z
T
DRIFT
2
2
sT (zDRIFT ) = sT,0 + 2µ

E• find z-dependent term

consistent with literature
recommended value
L. G. Christophorou, et al,
Journal of Physical and Chemical
Reference Data 25 (1996) 1341

• constant term (straggling?)

dominates until z~20cm,
and z=25 cm for σ2T<1mm
J. Battat, JM, et al., NIMA 755 (2014)• sets a maximum drift length per TPC
to be ~25 cm to preserve track direction
RHUL Jocelyn Monroe

April 7, 2016

4-shooter side
external view

DMTPCino: 1 m3 Active Volume Module
prototype for large detector:
build many 1m3 modules, because of diffusion limit.
goal: achieve similar or better S:N per pixel,
for 35o resolution at 50 keVr in 1m3 module, andR&D: 1 camera+lens/side (~0.005$/channel now)
TPC
installation
first light!
(June 2015)

1.2 m

RHUL Jocelyn Monroe~30 cmDec. 9, 2016

Signal:Noise
Lower pressure (P) gives longer range (good!), higher gain (good!), but lower dE/dx (bad!!)Signal size:

Ω=Noise size:

1−3
2
2 ~ 1016(1+ m) ( f /# )€To increase S:N: 1) increase geometric acceptance , 2) reduce N, 3) increase gas gain G
RHUL Jocelyn Monroe

Dec. 9, 2016

Optical System for Large Area Optical Readout
comparison of 20L prototype vs. DMTPCino optical systems S:N
20L prototype: 4x Alta CCD + Canon f/1.2lens
DMTPCino: 4-CCD side: Proline9000 CCD (0.01 e/pix/s dark rate) + Nikon f/0.95 lens
1-CCD side: Fairchild 486 CCD (0.0001 e/pix/s dark rate) with quad readout +large angle-of-view Canon f/0.95 lens
calculation inputs:•30 Torr pressure: 2.5 mm long track, 1 mm wide @ 50 keVr to estimate S/pixel•gas gain = assume 100,000k for DMTPCino, vs. 65,000 gain for 20L prototype•dark current rate and read noise from camera specs (confirmed in in-situ measurement)•measured scintillation spectrum, ϒ/e-, lens transmittance vs. wavelength, lens vignettingF(cm) / pixel
Lens/Cameraf#(um)

sensordiag.
(cm)

DMTPCino
1-CCD side

5/0.9515

6.14(113)2 18.4

2E-04

7

276

189/16 = 12

DMTPCino
4-CCD side

5/1.2

12

3.66

(57)2 15.6

2E-04

10

243

95/14 = 6.8

20L prototype 8.5/1.2

24

2.45

(16)2 6.65

5E-04

10

160

87/13 = 6.3

FoV
(cm)

m

acceptanceread
vixel size (um)S/N (e-/e-)noise (e-) (map to 1 pixel)(rho)

empirically: S:N>15 results in ~20 keVr track-finding threshold -> bin 2x2 before readout
RHUL Jocelyn Monroe

Dec. 9, 2016

Gas Gain R&D
triple mesh amplification: one camera
images 2x 25 cm drift regions

gap size
triple-mesh prototype(H. Tomita, PhD thesis 2010)

m3
goal

demonstrated high gain insmall prototypes, 50-200k
optimizing gap size, pitch tomaximize pixel signal:noise,•10x gain with 2x gap size
price: 25% amplification
region diffusion tails increase

4Shooter
10L prototype

H. Tomita, PhD thesis (2010)

RHUL Jocelyn Monroe

Dec. 9, 2016

DMTPCino: Gas Gain Calibration

higher gain = lower
energy threshold.
Fe-55 source (5.9keV) deployed tomeasure absolutegas gain vs. anodevoltage, at 30 Torr
operating pressure.

2nd gaincampaign

result: gain>250,000 can beachieved = factor of 4x higher
than previous operating point of
65,000 (in 20L prototype),
25x 10L prototype operating point.
RHUL Jocelyn Monroe

1st m3 gain campaign
10L prototype
started here

Dec. 9, 2016

DMTPCino: Integration of Readout Channels

PMT dΩ
0.4% atanode,
1% atcathodeOptical: CCD + PMT

PMT
V(t)

CCD
M. Leyton, G. Druitt, N. Guerrero

Charge:Anode +
Mesh @
500 MHz
readout

Anode V(t)RHUL Jocelyn Monroe

σV=0.1 mV

Mesh
V(t)

Dec. 9, 2016

DMTPCino: Direction Calibration with AmBe Neutron Source•Stable operation at 150k gain for 4 weeks. Coincident signals in all readout channels!
n dataangle)•Clear excess in n source direction in high energy events (qrecoil = recoil-source
example neutron
calibration event

m3 AmBeraw data

Preliminary

CCD
CCD
data

PMT
data
RHUL Jocelyn Monroe

mesh
data

cos(qrecoil)
J. Battat, et al., Physics Reports(2016) 1-46
alpha662
data

Dec. 9, 2016

Full Microphysics Simulation(C. Deaconu CYGNUS’15)

Generated Ionization:(TRIM simulation)

RHUL Jocelyn Monroe

Dec. 9, 2016

Full Microphysics Simulation(C. Deaconu CYGNUS’15)

Generated Ionization:
TRIM simulation+ HEED cluster generation+ MagBoltz

RHUL Jocelyn Monroe

Dec. 9, 2016

Full Microphysics Simulation(C. Deaconu CYGNUS’15)

Generated Ionization:
TRIM simulation+ HEED cluster generation+ MagBoltz+ GARFIELDRHUL Jocelyn Monroe

Dec. 9, 2016

Full Microphysics Simulation(C. Deaconu CYGNUS’15)

Generated Ionization:
TRIM simulation+ HEED cluster generation+ MagBoltz+ GARFIELD+ readout model

RHUL Jocelyn Monroe

Dec. 9, 2016

Full Microphysics Simulation(C. Deaconu CYGNUS’15)

Generated Ionization:
TRIM simulation+ HEED cluster generation+ MagBoltz+ GARFIELD+ readout model+ cluster finding+ 2D likelihood+ track reconstruction

RHUL Jocelyn Monroe

Dec. 9, 2016

Full Microphysics Simulation(C. Deaconu CYGNUS’15)

validated with comparison to d-d n calibration data, in high-gain small prototype
Generated at Primary:

DMTPC n calibration data,
50 keVr

Reconstructed:

DMTPC n calibration data,
150 keVr

Angular Resolution:

DMTPC n calibration data,
150 keVr

C. Deaconu, PhD thesis (2015)

Bottom lines:• we are reconstructing direction (including head-tail) at ~physics limit fromstraggling of primary F ion. Need to reduce ion straggling! Lower Z gas, i.e. He?
• axial resolution is ~40 degrees (FWHM) at 50 keVr
• TRIM predicts ~50% larger angular spread than observed (measure straggling!)
RHUL Jocelyn Monroe

Dec. 9, 2016

DMTPCino Sensitivity Projection

Number of events required toobserve the dark matter wind?
Analysis assumptions• Use physics model tuned
on data, assume 100k gain
• simulate n experiments,
compute forward fraction
and axial spread per bin• calculate p of obtaining thesevalues from isotropic
distribution, and combine
bins using Fisher’s method

C. Deaconu et al., sub. Phys.Rev.D (2016)
RHUL Jocelyn Monroe• Result: need 450 events
to measure anisotropy at
3σ in >50% of experiments.
Dec. 9, 2016

DMTPCino Sensitivity Projection• Result: need 450 events
to measure anisotropy at
3σ in >50% of experiments.
= 500 [300] m3-years for
100 (1000) GeV/c2 DM at
1 fb SD xsec on F(=25 kg-years exposure)

C. Deaconu et al., sub. Phys.Rev.D (2016)
RHUL Jocelyn Monroee.g. DEAP veto: 200 m3
Dec. 9, 2016

Outline
Physics Motivation
Detector Development-Experimental Considerations for Dark Matter Searches-Direction Measurement Progress in DMTPC
Outlook for Large Exposure-Geo-Neutrino Sensitivity-HPTPC for Neutrino Physics

RHUL Jocelyn Monroe

Dec. 9, 2016

Low Background Frontier

Horowitz et al,astro-ph/0302071

1012
10
10

pp

11

7

Be
N
15
O
17
F
8
B
hep

10

13

109
108
107
106
105
4

10

3

10

102
10

-1

1
10
Neutrino Energy (MeV)

neutrino-nucleus coherent
elastic scattering of solar
neutrinos JM, P. Fisher, PRD76:033007

Supernova
neutrinos in NC, flux and spectrumwith direction measurement:
Geo ν Flux (cm-2 s-1)

Solar ν Flux (cm-2 s-1 bin-1)

tonne scale, keV threshold,low background detectors
with directionality have potential
for first observations of...

105

238

104

U

235

U

3

10

232

Th

102

40

40K geo-neutrinos

K

10
1
10-1
10-2
0.5

1

1.5

2

2.5

3

3.5

4

4.5

Anti-Neutrino Energy (MeV)

RHUL Jocelyn Monroe

Leyton, Dye, JM, sub. Nature (2016)

Dec. 9, 2016

U, Th geo-nus first observed by KamLAND,
then Borexino using inverse beta decayrate ~4 events/100 ton-year
2.5x rate from BSE-based model (KamLAND),
1.6x (Borexino) Mantovani et al., PRD69:013001 (2004)

Geo ν Flux (cm-2 s-1)

Geo-Neutrinos

105
238

U

4

10

235

U

103

232
40

102

Th

K

10
1
10-1

40K geo-nus could contribute10-2

significantly to the 44 TW
radiogenic heat of the earth, buthave never been measured, since
endpoint <1.8 MeV threshold for IBD

0.5

1

1.5

2

2.5

3

3.5

4

4.5

Anti-Neutrino Energy (MeV)

elastic scattering has no threshold, + direction of
the out-going e- is correlated with the incident nu,
can discriminate backgrounds from sun, reactors
Large, direction-sensitive detectors have potential
to make the first observation of the 40K flux, andperhaps to separate crust vs. mantle composition.
RHUL Jocelyn Monroe

Dec. 9, 2016

Geo-Neutrinos and Direction
Measure the recoil e- direction to infer the nu direction.
Example) MUNU measured e- from reactor nu-e scattering,with 50% efficiency, 12o-15o resolution above 200 keV,in CF4 gas at 1 bar pressure, using MWPC + PMTs
Daraktchieva et al., PLB 615, 153 (2005)

for DMTPC study, assume similar performance and thresholdwith detailed geo-nu flux modelx-yfrom PREM and CRUST 1.0
MUNU data
0.5 MeV electron

x-z

RHUL Jocelyn Monroe

Dec. 9, 2016

Incident Neutrino Flux

based on Bergstrom et al., JHEP 03, 132 (2016)

RHUL Jocelyn Monroe

Leyton, Dye, JM, sub. Nature (2016)

based on Baldoncini et al., PRD91 065002 (2015)

Dec. 9, 2016

Scattering Rates
experiments use IBD because
solar nu-e- elastic scattering
backgrounds are large!
direction-sensitive low-energy
TPCs can exploit angle, time,and energy spectrum differences

0.007
20

0.006
0.005

15

0.004
10

0.003
0.002

5

Event Time (hr)Event Time (hr)(CNO signal today = geo-nu bgnd
tomorrow) Bonvicini et al, NIM A 491 (2002) 402

0.007
20

0.006
0.005

15

0.004
10

0.003
0.002

5

0.001

0.001
0
-1

RHUL Jocelyn Monroe

-0.5

0

0.5

1

Geo-ν Electron Cos(θ)

0

0
-1

-0.5

0

0.5

1

Solar-ν Electron Cos(θ)

0Dec. 9, 2016

Geo-Neutrino Sensitivity
simulate 1000 toy experiments, use
profile likelihood statistic to test
case (i): no 40K signal in “data,”
find 90, 95% CL upper limit on 40K flux
case (ii): yes 40K signal in “data,”
find 40K flux at which null hypothesis
can be excluded at 90, 95% CL
studied signal = 40K, mantle, core, reactor

RHUL Jocelyn Monroe

Dec. 9, 2016

Connection with R&D for Accelerator Neutrino Oscillations
Low Threshold Gas TPC R&D for Neutrino Physics:
goal: reduce neutrino cross section systematics from 8-10% to 1-2% for CP violation
search in long-baseline neutrino oscillation experiments, with 10 MeV threshold• address nuclear model uncertainties with precision measurements of FS p, e, mu
T2K νμ-Ar data event

Liguid Argon

P. Hamilton (Imperial), NuInt14

Gas Argon (1 bar)

RHUL Jocelyn Monroe•higher pressure needed!
Example) 5E4 events for T2KII flux,in 40 m3 detector volume at 5 bar CF4.
Dec. 9, 2016

Proton Range in HPTPC
1 cm track reconstruction threshold gives ~50 MeV/c proton threshold in 5 bar Ar,
sufficient to conclusively measure the problematic region in final state particle
kinematics in neutrino interactions for long baseline oscillations.
1 cm range threshold -> ~1 mm readout pitch (and 102 x S:N for DMTPC)RHUL Jocelyn Monroe

Dec. 9, 2016

HPTPC Prototype
Pressure vessel capable of 5 bar operation with mixtures of CF4, Ar, Ne, CO2, CH4.
Optical readout based on DMTPC (0.5 mm optical plate scale), plan micromegas
amplification structures with T2K TPC electronics (charge readout with ~cm pitch)
Pressure vesseldelivery early ’17.

Simulated 10 MeV p
in 5 bar HPTPC

50 cm drift length
1.2 m TPC diameter(// to beam direction)

UK groups funded to build
prototype for CERN beam test:
ICL,RHUL,Warwick,Lancaster,+ discussions with EU groups
on participation in beam test
RHUL Jocelyn Monroe

We welcome
collaboration andare actively seeking
new partners!
Dec. 9, 2016

Beam Test: Proton-Nucleus Cross Section
no data in most of the relevant region for neutrino
interactions in long baseline oscillation experiments
beam test goal: measure p absorption cross section, andfinal state multiplicity, in p-Ar, p-F interactions < 1 GeV/c

RHUL Jocelyn Monroe

Dec. 9, 2016

Conclusions• Optical TPC readout is a promising technology to get to sub-mm

resolution at reasonable cost per channel in very large detectors.
• DMTPC has demonstrated <40o angular resolution with 25 cm diffusion,

recovering the intrinsic directionality of the recoil to the straggling limit• In the process of moving from small prototypes to ‘physics-scale’detector module. Commissioning of DMTPCino underway...
• demonstrated 4x increase in gas gain
• coincident readout of charge (fast, slow), light (fast, slow) signals
powerful for background rejection.
•main challenge: achieve resolution + head-tail, at lower energy•Exploring applications to neutrino scattering physics,

looks promising for geo- and accelerator- neutrinos,
new collaborators very welcome to get involved!
RHUL Jocelyn Monroe

Dec. 9, 2016