Liquid Argon - The Future of Neutrino Physics?

Talk delivered February 25, 2010 at the University of Warwick Department of Physics Postgraduate Seminar Series.

Transcript

1. Liquid
Argon:
 The
Future
of
Neutrino
Physics
 Andrew
J.
Bennieston
 University
of
Warwick
‐
February
25,
2010

2. Why
Neutrino
Physics?
 •  Neutrino
oscillaJons
–
possible
explanaJon
 for
maOer‐anJmaOer
asymmetry
of
the
 universe
 •  Neutrino
masses
–
absolute
values,
hierarchy
 •  Majorana
nature
of
neutrino
–
Is
the
neutrino
 its
own
anJparJcle?
Neutrinoless
double
β
 decay
 2

3. Neutrino
OscillaJons
 3
 |νi = i α Uαi |να U =   1 0 0 0 c23 s23 0 −s23 c23     c13 0 s13 e−iδ 0 1 0 −s13 e−iδ 0 c13     c12 s12 0 −s12 c12 0 0 0 1   “Atmospheric”
 “Reactor”
 “Solar”
 Mass
States
 Flavour
States
 PMNS
Matrix

4. Neutrino
DetecJon
Techniques
 •  Detect
charged
parJcles
in
the
final
state
 •  Require
charged‐current
neutrino‐nucleon
 interacJons
of
the
sort:
 •  Neutrino
interacJon
cross‐secJons
are
Jny:
 need
large
volumes
of
dense
maOer
 •  Liquid
targets
provide
large
volumes
of
maOer
 at
low
cost
(SuperK:
H2 O,
SNO:
D2 O,
KamLAND:
Mineral
oil
&
ScinJllator)
 νl + n → l− + p+ 4

5. Liquid
Argon
for
Neutrino
DetecJon
 •  IonisaJon
charge
(tracking
at
mm
granularity)
 •  ScinJllaJon
light:
UV
(λ
=
128
nm)
to
which
Ar
 is
mostly
transparent
(calorimetry)
 •  (Some)
Čerenkov
light
(calorimetry?)
 5

6. Time‐ProjecJon
Chambers
 Readout
in
2D
plane
+
Jme
of
arrival
of
charge
at
plane

3D
imaging
 6

7. Thick
Gas
Electron
MulJpliers
 •  Double‐sided
PCB
with
holes
drilled
through
&
 high
voltage
applied
 •  Charge
mulJplicaJon
of
e‐
driling
through
 TGEM
holes
in
gaseous
Ar
 •  Also
electroluminescence
 •  Charge
mulJplicaJon
not
observed
in
LAr
 •  But
electroluminescence
sJll
happens…
 – OpJcal
readout
concept!
 7

8. Simulated
Hadronic
Event
 8

9. LAr
TPCs
–
Challenges
 •  Need
high
resoluJon
tracking
for
PID
 
 but
 •  Long
signal
tracks
with
lots
of
short‐scale
detail
 – Significant
reconstruc/on
challenge!
 •  Need
large
volume
for
containment
(calorimetry)
 
 but
 •  Ar
must
be
of
high
purity
for
long
dril
lengths
 – Significant
hardware
challenge!
 9

10. LAr
@
Warwick
–
Current
R&D
 SimulaJon
&
 ReconstrucJon
 • GEANT4
 physics
 SimulaJon
 • Track
 ReconstrucJon
 Hardware
 • LAr
purity
&
 handling
 • Readout
&
 control
 electronics
 Physics
 • Charge
 transport
 study
 • Light
 producJon
 study
 10

11. LAr
Test
Stand
&
Purity
Monitor
 •  Temperature,
pressure
&
level
meters
as
well
as
 purity
monitor
 •  Physics
goal
is
to
verify
light
producJon
in
TGEM
 holes
 •  Also
provide
experimental
input
on
modelling
 why
light
is
produced
in
the
holes
–
COMSOL
 simulaJon
suggests
rough
edges
responsible;
 trying
drilled
&
laser
cut
holes
 11

12. LAr
Test
Stand
 12
 Image:
N.
McConkey

13. Track
ReconstrucJon
 13
 “The
challenge
is
significant:
no
bubble
chamber
 event
reconstrucJon
was
ever
fully
 automated”
 
K.
T.
McDonald

 (DUSEL
Workshop,
BNL
2008)

14. Simplifying
the
Problem
 14

15. Comparing
ReconstrucJon
Algorithms
 •  Hough
Transform
–
global
transformaJon
 – Established
technique
 •  “KD
Tree”
–
local
fitng
(c.f.
Kalman
Filter)
 – New
approach
influenced
by
popular
technique
 •  “Track
Road”
–
brute
force
 – Simplest
concept
but
problemaJc
for
large
data
 15

16. Hough
Transform
 •  Relates
each
point
in
a
2D
projecJon
to
a
 sinusoidal
curve
 •  Build
2D
histogram
of
r(θ)
 •  Points
which
form
a
straight
line
have
 sinusoids
which
intersect
at
the
(r,
θ)
 parameters
of
that
line
 •  Reduces
problem
of
finding
lines
to
one
of
 finding
peaks
in
a
histogram!
 16
 r(θ) = xi cos θ + yi sin θ
17. Hough
Transform
 17

18. KD
Tree
 •  IteraJve
nearest‐ neighbour
search
&
 fitng
over
last
N
points
 •  Histograms
of
fit
results
 (direcJon
cosines)
form
 Gaussian
peaks
 •  Parameters
of
lines
 obtained
from
these
 peaks
 event11_segment1_x -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 0 5 10 15 20 25 30 35 40 45 event11_segment1_x event11_segment1_x 18

19. KD
Tree
 19

20. Track
Road
 •  Peter
Piper
picked
a
pair
of
pickled
points
 •  …
then
drew
a
cylinder
centred
on
the
line
 between
them
 •  Any
points
inside
cylinder
considered
part
of
 the
track
 •  Do
this
for
every
pair
of
points
(brute
force)
–
 real
tracks
correspond
to
those
cylinders
 containing
the
most
points
(greatest
charge)
 20

21. The
(Near)
Future
 •  Comparison
of
algorithm
efficiencies
for
several
 geometric
event
classes
–
paper
on
 reconstrucJon
techniques
 •  ConJnue
towards
reconstrucJon
of
data
from
 real
LAr
TPCs
via
GEANT4
simulated
data
 •  Hardware
–
proof
of
concept
for
opJcal
readout,
 followed
by
larger‐scale
LAr
volume
(200
litres?)
 21

22. The
(More
Distant)
Future
 •  Large‐scale
LAr
TPCs
already
planned
/
running
 –  ICARUS
(CERN)
 –  MicroBooNE,
LBNE,
ArgoNeuT
(Fermilab)
 –  MODULAR
(Gran
Sasso)
 •  Possible
future
intermediate
detector
for
the
T2K
 experiment
(Japan)
 •  Good
case
for
LAr
TPCs
as
detectors
for
a
future
neutrino
 factory
 •  Also
have
applicaJons
in
searches
for
dark
maOer,
proton
 decay,
…
 •  Automated
reconstrucJon
will
be
needed
for
all
of
these!
 22

23. Please
keep
your
seatbelts
fastened
unJl
the
 talk
has
come
to
a
complete
stop.
 23