Kaon Monitoring in MiniBooNE:
The LMC Detector
E. D. Zimmerman
University of Colorado
NBI 2003
KEK, Tsukuba
November 10, 2003

Kaon Monitoring at MiniBooNE
1) K-decay νe background at BooNE
K production estimates2) Decay kinematics
3) The “Little Muon Counter” (LMC)
Concept/Placement
Civil construction/infrastructure
Collimator
Fiber Tracker
Temporary detector
StatusK-decay νe background
MiniBooNE will see ~200-400 νe from K+ and K0L
decays each year -- comparable to the yield fromoscillation physics if LSND is correct.

Goal is a systematic error of <10% on Kdecay νe.
Information on these decays will come from:Monte Carlo (GEANT4, MARS, GFLUKA)

50%
disagreements!

Production measurements (BNL E910, HARP, plus other,older data)
In-situ measurement: LMC

Decay Kinematics
In the downstream part of the secondary beam, high-pT
mesons have generally been removed by collimation.

High-pT particles come primarily from decays.
For muons:High-pT muons come almost exclusively from K decays.

pT separation becomes |p| separation when specific decay
angle selected.
Exploit by measuring µ momentum distribution at aparticular angle; infer parent particles.

2 GeV π->µνµdecay

Muons kinematically limitedto θ<1.1˚ (20 mrad)

350 MeV π->µνµdecay
Threshold for 7˚ µ emission ispπ ≅ 350 MeV/c.
Decay muon momentum is only
230 MeV/c.

+2 GeV K ->µνdecay
Muons can be emitted atangles up to 0.6 rad (~34°)
Muons at 7° have E=1.6GeVDecay muon energies versus parent kaonenergy for different decay angles:

Muons from K decay in BooNE GEANT MC

Arc pattern: Kµ2
Infill from Kµ3

Muons at 7° from pion, kaon decay:
Clear separation
between π and Kdecays.
High apparent K/πparentage ratio:
most π in beam
too high energy
to produce 7°muon
Low-energy π
more likely tohave decayed
upstream

The LMC“Little Muon Counter”
Concept: allow decaymuons to enter anevacuated drift pipe 7°off the beam axis.
A magnetic
spectrometer measuresthe muon momentum
spectrum at the end of
the drift pipe.

LMC GroupA subset of the BooNE collaboration
University of Colorado:
T. L. Hart, H. A. Koepke, R. H. Nelson, E. D. Zimmerman

Columbia University:
J. Formaggio (now at Univ. of Washington)

Princeton University:
A. O. Bazarko, J. Hunt, P. D. Meyers

LMC Components
Drift pipe
Collimator
Veto

Fiber Tracler
Dipole Magnet
Muon Filter

GEANT model of LMC region

Civil Construction for LMC

Prefabricatedcylindrical steel
enclosure for LMC
detector equipment.
Diameter 14 feet (4.2meters); floor level 20
feet (6 meters) below
grade.
Enclosure built byUSEMCO, Inc. inTomah, Wisconsin anddelivered directly tosite at FNAL.

Exterior and interior of LMC
enclosure vault at USEMCO(February 2001)

BooNE decay pipe and LMC drift pipe, November 2000

LMC enclosure being positioned

Drift pipe connection

NovemberDecember 2001

Backfilling -- only access shaft visibleMI-13A service building

Later addition to project; houses front-end readout electronics, DAQCollimator motivation: background from “dirt muons”

Spectrum of muons out of drift pipe
Unmanageable rate:
thousands of muons
per RF bucket (19 ns)
Dirt muons dominate
Solution to bothissues: narrowcollimatorCollimator designedand machined atPrinceton in 2001

Clean muons dominate above 1.2 GeV after collimator.

Veto
Veto consists of four scintillator panels
between the collimator and the fiber
tracker, with a circular central aperture,radius 0.5 cm. Veto hole is aligned to thecollimator hole and will be used inreconstruction to define the limitingaperture.

Fiber Tracker
Bicron 1mm scint. fibers; dry interface to light-guide fibers;
6-stage Hamamatsu R1666 PMTs with custom active bases
Upstream 2 detectors:
1.5x1.5 cm2, x and yviews
Magnet: permanent(ferrite), 2.7 kG, field
length 22.5 cm.
Downstream:
2x12 cm2, only x view
(for post-bend slope)Design rendering of fiber tracker frameJune 2002 beam test of fiber plane and PMT base prototypes at
Indiana University Cyclotron Facility: Charged particle inefficiency
measured to be ~10-4.

Fiber planes
Downstream plane(X view only, 12 cm wide)

Upstream plane (without fibers)(X and Y views, 1.5 cm square)

Staggered double fiber layer
removes inefficiency from cracks

Fiber placement and aluminizationScintillating fibers were laid in the detector frames andmounted with epoxy, then the ends were polished in
the frames. The non-interface ends of the fibers werealuminized.
Aluminization wasperformed by acompany which
failed to provide
enough cooling. Allfibers were destroyed!
Detector completion
delayed several weeks.

Light guide fibers and interfaces
Fibers weremounted inframes, epoxiedin place, and theinterface ends
polished.
Interfaces were mounted on thedetector frame in nominal position,and routed through acrylic cookies
which were placed on “cookie sheets”
with holes at the future positions ofPMT faces. Fibers were then clippedin place to exact length and epoxied
into cookies; cookies were thenpolished with fibers in them.

PMTs and bases
Tracker uses 160
Hamamatsu R1666 3/4
inch PMTs, previously
used in FNAL E872.
New active “quadbases” with 4 PMTs
and onboard preamp,postamp (total gain400). Each HV channel
serves 4 PMTs.

Road Trip!

EDZ drove the detector across the country to FNAL in a
rented van in March 2003.

Spectrometer dipole magnet

2.7 kG permanent dipole
1 in. x 9 in. gap
Magnet based on Recycler
ring designs

Final assembly of fiber tracker at FNAL
Placing cookies
on tubes

Magnet installation and final alignmentOctober2003

Muon filter
20 inch long, 8 inch squaretungsten/scintillator range
stack behind fiber tracker will
identify muons.
Expect µ/π ratio of order 2-4;
most π are from Kl3 decay.

Data acquisition
CAMAC-based data acquisition(DAQ) read through SCSI interface
into rack-mounted Linux PC.
LeCroy 3377 500 ps multihit ECL
TDCs are triggered by beam arrival
signal and read each fiber tracker,
veto, and muon filter channel.
GPS module time-stamps eacheach event.
Data stream is read into main
MiniBooNE DAQ and events are
merged with beamline and neutrino
detector data based on GPS timestamp.
High voltage supplied by LeCroy
3402 HV mainframes.

Temporary detector
After the aluminization accident
we decided to place a temporary
steel/scintillator range stackbehind the collimator, to make arough check of rates.

Result: 19 ns RF beam structure easily visible.
Low E rates difficult to measure with unsegmented detector (highoccupancy) but rate of muons with E>1.3 GeV is within MC
expectations of 1-3 per spill.

Status of the LMC
Major installation work during current
accelerator shutdown
Fiber tracker is operating -- expect first beam
signals any day!
Working on analysis code infrastructure
Expect first LMC analysis in a few months.