Transcript PMijakowski_17April_T2K_COL_MEET_FINAL.ppt

Status of the atmospheric
muon studies
Piotr Mijakowski
OUTLINE:
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Primary muon spectrum at the sea level
Atmospheric muons underground@ND280
location
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Geant4 simulation
NTUPLES with atmospheric muon data
Some results
SMRD Meeting @KEK, 17-18 April 2007
Motivation
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GOAL: determine the requirements for
cosmic ray trigger
SMRD will provide c.r trigger for calibration of
inner ND280 detector components
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No Ecal at the beginning
Calibration data taken between a beam spills
Detector requirements:
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not always clear (more communication needed)
TPC+FGD: various samples – crossing FGD&TPC,
crossing cathode; giving the 20cm transverse length
P0D: horizontal muons, 100k per week per channel
Primary muon spectrum at the sea
level
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So far used the official K2K data file –
Oyama spectrum
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cosmic ray muon simulation
10k events
structure:
event# cos(q)
Momentum
Oyama spectrum
Momentum - zoom
FIT:
- cos(q)>=0.175 by
power factor 2.04
- cos(q)<0.175
linear fit
cos2.04q
zenith
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Oyama - cos2.04q; world publ. data - cos2.16q (*) (different
geomagnetic locations)
(*) http://www.scifun.ed.ac.uk/pages/pp4ss/pp4ss-hodoscope.html 2006
Oyama spectrum – P and cosq
correlation
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for vertical
muons P and
cosq uncorrelated
for large angles:
correlation (LE m
decay before reaching
the surface, HE p decays
mainly contribute)
Simulation of atm. muons
underground
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muons sampled from a square surface and
propagated through the rock
Initial energy, zenith angle - Oyama, azimuthal
angle – isotropic
3 sets of simulations:
suitable only for veritical muon study
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22m x 22m, illumination time = ~36.1 sec.
200m x 200m, illum. time = ~2.2 sec.
400m x 400m, illum. time = ~0.27 sec.
small statistics so far
Geant4 simulation - geometry
Geometry visualization
top view
side view
x
z
d = 17.5m
30cm thick
cement floor
2m of air
below floor
1m cement wall
DETECTOR BOX - shifted 1m along z axis from the pit center:
length (z axis) = 7.723 m, width (x axis) = 5.63 m, height (y axis)= 6.150 m
Zenith angle
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cosq of muons entering the detector box
green – 400m x 400m, 0.27 s
red – 200m x 200m, 2.2 s
blue – 22m x 22m, 36 s
top surface
all det. sides
entries
2255
17242 179348
tot. flux
[m/(m2s)]
39.8
±0.8
38.0
±0.3
23.89
±0.05
mean
0.792
0.801
0.916
entries
1517
11993
152221
tot. flux
[m/(m2s)]
128±4
126±1.5
96.9±0.3
mean
0.849
0.849
0.912
Vertical flux
information!
Energy spectra
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kinetic energy of muons entering the detector box
green – 400m x 400m, 0.27 s
red – 200m x 200m, 2.2 s
blue – 22m x 22m, 36 s
top surface
all det. sides
entries
2255
17242 179348
tot. flux
[m/(m2s)]
39.8
±0.8
38.0
±0.3
23.89
±0.05
mean
[GeV]
12.87
13.05
5.37
entries
1517
11993
152221
tot. flux
[m/(m2s)]
128±4
126±1.5
96.9±0.3
mean [GeV]
7.62
8.56
5.29
Muons@horizontal walls
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y coordinate (height) distribution of muons entering the detector
box from the sides (only 2 instrumented sides)
green – 400m x 400m, 0.27 s
red – 200m x 200m, 2.2 s
blue – 22m x 22m, 36 s
entries
458
tot. flux
[m/(m2s)]
17.7±0.8
mean [m]
0.30
3231
17566
ONLY 2 sides
15.6±0.3 5.12±0.04
0.27
Horizontal flux
information!
0.43
NTUPLES
NTUPLE (ROOT format):
 1 branch „Event”
 11 leaves:
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„no_event” (event number)
„charge” (values = „+1” for m+ or „-1” for m-)*
„cos_theta”
„E_kin”
„x”, „y”, „z”
„px”, „py”, „pz”
„ID” (track ID of muon from G4)
files can be downloaded from:
http://neutrino.fuw.edu.pl/public/samples/t2k/nd280_atm_muons/
- see description of the contents in readme.txt file
- you will also find some example macro files to read the ntuples
(*) implemented mu+/mu- ratio from „Precise Measurements of Atmospheric
Muon Fluxes with the BESS Spectrometer” – meas.@Tsukuba
(arXiv:astro-ph/0205344 )