Transcript The MINOS Far Detector

NuMI
MINOS
The MINOS Far Detector
Cosmic Rays and their neutrinos are
being collected now.
How does this work, and of what use is
this data?
Alec Habig, Univ. of Minnesota Duluth,
for the MINOS collaboration
NuMI
The MINOS
Experiment
MINOS
• Main Injector Neutrino
Oscillation Search
– Will utilize NuMI beam from
Fermilab
• Front-to-back nm oscillation study
– Produce well-studied nm beam
– Measure nm spectrum just after
production with “Near Detector”
– Measure again 735 km later with
“Far Detector”
735 km
Neutrino 2002, May
25-30, 2002, Munich
• Beam goes from Fermilab to the
Soudan Mine Underground Lab
Alec Habig
Page 2
NuMI
The Far Detector
MINOS
• Steel/Scintillator sampling
calorimeter
– 5.4 kt, 8m diameter, 31m long
– 486 layers, each made of:
T
o
F
e
r
m
i
l
a
b
• 1” steel
• 1 cm plastic scintillator
8m
– Magnetized to ~1.5 T
• Design goals
15m
½ of the Far Detector
Neutrino 2002, May
25-30, 2002, Munich
– ne/nm/p discrimination
– Good energy resolution
• For both m and showers
– Good timing, both hit-to-hit and
absolute
• For particle direction and
synching with Fermilab beam
Alec Habig
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NuMI
Far Detector Progress
MINOS
• Construction began
August 2001
• Now up to about plane
#225
– Almost halfway done!
– First half complete in
July when it will be
magnetized
• Taking Cosmic Ray
data as it is built
– Each plane
independently
instrumented
Plane #200, May 3, 2002
Neutrino 2002, May
25-30, 2002, Munich
Alec Habig
Page 4
NuMI
Particle Detection
MINOS
• 4.1 cm x 8m scint strips
bundled into “modules”
– Light channeled out via 2ended fiber
• Each plane’s strips are
90o from the last
– “U” and “V” views
• 17 GeV MC m shown
below from side, in U,V
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20
20
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From FNAL
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Neutrino 2002, May
25-30, 2002, Munich
28
Alec Habig
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NuMI
Multiplexing
MINOS
• Light detected by 16
pixel PMTs
• 8 fibers per pixel,
ganged together with:
– Maximal physical strip
separation
– Minimal in-PMT crosstalk
Fiber Layout
One of 3 Ham. M16
PMTs in this “Mux Box”
Neutrino 2002, May
25-30, 2002, Munich
16 mm
Alec Habig
M16 PMT
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NuMI
Front End Electronics
MINOS
• Fibers from each strip end are multiplexed onto PMT pixels
• Signals amplified, shaped, and tracked+held by “VA” chips
– Calibration charge can also be injected in the same place as PMT
charge for functionality check and calibration of full electronics path
• Timing information sent upstream from this “Front End” rack
Neutrino 2002, May
25-30, 2002, Munich
Alec Habig
Page 7
NuMI
Data Gathering
MINOS
• VME “Master” crate
– VA Readout Controllers
“VARC”s
• Charge from PMTs digitized
by 14-bit ADCs
• Time stamped to 1.6ns by
internal clock
– 2/6 or 2/36 pre-trigger applied
– Hits given absolute GPS time
• Data read out over PVIC
bus to computer room
– 4/5 plane software trigger
applied, hits time ordered
– Data formatted in ROOT
1 of 16 VME crates
Digitizes 72 mux boxes
Each w/3 16-pixel PMTs
Neutrino 2002, May
25-30, 2002, Munich
Alec Habig
Page 8
NuMI
De-multiplexing
MINOS
• Scintillator strip ends are multiplexed 8-1 per
electronics channel
• How to figure out which strip a particle really went
through?
• Matching hits on both ends of a strip helps in the
simplest track case
• For multiple hits on a plane and showers:
– All the different possible “hypotheses” of which strip was really
hit tested against the possible real physics
– Best fitting hypotheses saved
• Reconstructing close multiple muons very difficult!
Neutrino 2002, May
25-30, 2002, Munich
Alec Habig
Page 9
NuMI
MINOS
A Cosmic Ray
De-multiplexed
• Success rate for Cosmic Rays:
– 94% of hits correctly associated with their strips
– 97% of CR events successfully sorted out
CR m after De-multiplexing
CR m before De-multiplexing
Neutrino 2002, May
25-30, 2002, Munich
Alec Habig
Page 10
NuMI
Light Injection
MINOS
• Calibration using controlled light:
– LEDs illuminate 8-10 calibration fiber ends each
– Fibers carry light from LED to shine on ends of scint strip fibers
• Varying light levels used to map out detector and
phototube response
• Regular pulsing at a constant light level during normal
operations
– Tracks changing detector response
– Flags problems with optical path
Neutrino 2002, May
25-30, 2002, Munich
Alec Habig
Light from calibration
fibers illuminating
ends of fibers
from the scintillator
where they are
bundled Page 11
NuMI
Cosmic Rays
MINOS
• As planes are added to the
detector, they contribute to
the data acquisition
• Currently taking Cosmic Ray
data
– CR rate: 1000 m/strip/month,
2% stop in detector
• Excellent “beam” for detector
commissioning
– Real particle data provide endto-end test of all hardware,
software systems
CR-m light output with expectations
~10 pe at mid-strip (sum of both ends)
Neutrino 2002, May
25-30, 2002, Munich
• Good calibration source
– Geometry, gain, timing,
reconstruction software
Alec Habig
Page 12
NuMI
CR Calibrations
MINOS
• Physical plane locations are surveyed as the planes
are raised
– CR m draw nice straight lines
– Residuals to the m fits are not bad with nominal plane
geometry, excellent with survey-corrected data
• Timing calibrations
– CR m are nice straight lines moving at b=1
– Use this physics to find and fit absolute timing offsets
Timing offsets (ns) vs. channel.
Different delays in different
electronics paths are
clearly seen, as is the few (2.6)
nanosecond resolution
Need t0 fit plot
Neutrino 2002, May
25-30, 2002, Munich
Alec Habig
Page 13
NuMI
Initial n Searches
MINOS
• Atmospheric n are
present in the data
– Contained vertex search
being refined
– Up-going m search
underway as part of CR
timing calibrations
• Reconstruct timing of m
tracks
An up-m!
– Down-going CR’s have
b=1
– Up-going n-induced m
have b=-1
Neutrino 2002, May
25-30, 2002, Munich
Alec Habig
Page 14
NuMI
Summary
MINOS
• The MINOS Far
Detector construction is
nearing the ½ way point
• Data being taken as the
detector grows is used
to validate and calibrate
both hardware and
software
• Will be ready for beam
– Plus atmospheric n work
can be done with
magnetic field!
• n/n separation
First n! An up-going m seen on the evening
Neutrino 2002, May
Alec Habig
of March
22,
2002
–
MINOS
works!
25-30, 2002, Munich
The presenter gratefully acknowledges support
Page 15
for this poster from the National Science
Foundation via its RUI grant #0098579