Page 1
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Measurement of the p/p ratio
using the Moon shadow with the L3 detector
Jean-Francois PARRIAUDon behalf of the L3 collaboration
☛ L3+Cosmics: experimental setup and topics
☛ Principle of the Moon shadow technique
☛ Observation of the Moon shadow in L3+Cosmics
☛ p/p ratio: measurement and limits
☛ Conclusion
L3+C
– 38 –
Fig. 10.— The p /p ratio at the top of the atmosphere obtained in this work compared with
previous measurements (Buffington, Schindler, & Pennypacker 1981; Golden et al. 1984;
Bogomolov et al. 1987, 1990; Salomon et al. 1990; Stochaj et al. 1990; Mitchell et al. 1996;
100 1000
0.01
CAPRICE
1.0
0.1
Ant
ipro
ton/
prot
on r
atio
10-5
10-4
Caprice
10
Kinetic energy (GeV)
-3
10-6
1 10
June 19 2002 Measurement of the p/p ratio using the Moon shadow with the L3 detector (page 1) Jean-Francois PARRIAUD
on behalf of the L3 collaboration
Page 2
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L3+
Cosm
ics:
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Page 3
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L3+Cosmics: topics
2 years running: 1999-2000
Statistics: 12x109 muon events
Topics:
✦ Muon momentum spectrum in the 20-2000
GeV/c range at the % level
✦ Primary composition around the “knee”
✦ Gamma-Ray Bursts, point sources
✦ Moon shadow
✦ . . . 0
2000
4000
6000
0 50 100 150 200
time (days)
Eve
nts
/ 10
6
Year 2000 Year 1999
June 19 2002 Measurement of the p/p ratio using the Moon shadow with the L3 detector (page 3) Jean-Francois PARRIAUD
on behalf of the L3 collaboration
Page 4
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Moon shadow
Cosmic rays are blocked by the Moon.
(Clark 1957)
=⇒ Deficit of cosmic rays in the direction
of the Moon.
☛ Size of the deficit → angular resolution
of the experiment.
☛ Position of the deficit → pointing error.
Observed in the 90’s (SOUDAN, MACRO,
CASA . . .)
N
W
E
Moon
Earth
June 19 2002 Measurement of the p/p ratio using the Moon shadow with the L3 detector (page 4) Jean-Francois PARRIAUD
on behalf of the L3 collaboration
Page 5
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Moon shadow
Geomagnetic field: positively charged par-
ticles deflected to the East
=⇒ Deficit appears shifted to the West.
=⇒ If present, antimatter in cosmic rays
will induce a deficit on the opposite side.
☛ Earth-Moon = ion spectrometer (Urban
et al., ARTEMIS experiment)
Deflection � 1◦E(TeV/c)
GENEVA (6.02◦N, 46.25◦E)
Earth
Moonshadow
E
for protons
W
N
p
p
pB
Moonshadow for anti-protons
Moon
June 19 2002 Measurement of the p/p ratio using the Moon shadow with the L3 detector (page 5) Jean-Francois PARRIAUD
on behalf of the L3 collaboration
Page 6
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Moon shadow
Sky seen by L3+C:
1 pixel = 1 direction
Moon trajectory:
Deflection = f(Moon location)
sin(θz).sin(αz)
sin(
θ z).c
os(α
z)
June 19 2002 Measurement of the p/p ratio using the Moon shadow with the L3 detector (page 6) Jean-Francois PARRIAUD
on behalf of the L3 collaboration
Page 7
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Observation of the Moon shadow in L3+Cosmics
f(θ) = λ · (1 − ε · R2Moon
2·σ2 · e− θ2
2·σ2 )
600
610
620
630
640
650
660
670
680
690
0 0.5 1 1.5 2 2.5 3 3.5 4
17.18 / 17λ 662. ±2.σ 0.54 ±0.10ε 0.72 ±0.21
Angle with deficit centre (°)
Eve
nt d
ensi
ty (e
vt .moo
n-1)
375
400
425
450
475
500
525
550
575
0 0.5 1 1.5 2 2.5 3 3.5 4
16.75 / 17λ 536. ±2.σ 0.35 ±0.06ε 0.83 ±0.19
Angle with deficit centre (°)
Eve
nt d
ensi
ty (e
vt .moo
n-1)
Experimental angular resolution:
✦ Angle between muon and primary particle
✦ Multiple scattering in molasse
✦ Detector angular resolution
+ Moon shadow elongation by geomagnetic field
June 19 2002 Measurement of the p/p ratio using the Moon shadow with the L3 detector (page 7) Jean-Francois PARRIAUD
on behalf of the L3 collaboration
Page 8
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Determination of the pointing error
|pµ| > 100 GeV/c, use of the local coordinates system Zenith vs Azimuth
Background: Moon’s path in the sky, delayed in time.
Substracted to source map → Moon effect.
Smoothing: uniform distribution.
Result in standard deviations from normal distribution.
x = Azev - Azmoon (°)
y =
θzev
- θz
moo
n (°
)
x = Azev - Azmoon (°)
y =
θzev
- θz
moo
n (°
)
Comparison Data-MC: pointing error � 0.1◦.
June 19 2002 Measurement of the p/p ratio using the Moon shadow with the L3 detector (page 8) Jean-Francois PARRIAUD
on behalf of the L3 collaboration
Page 9
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Observation of the geomagnetic field effect
Deflection = ∆θ · −−−→udefl
∆θ = f(Az, θz, pproton(unknown))Simulation: −−−→udefl = g(Az, θz)
Horizontal axis = - −−−→udefl
=⇒ Deficit along this axis.
65 − 100 GeV/c: ∆x = 0.8◦
> 100 GeV/c: ∆x = 0.25◦
Parallel to deflection (°)
Ort
hogo
nal
to d
efle
ctio
n (°
)
Parallel to deflection (°)
Ort
hogo
nal t
o de
flec
tion
(°)
Parallel to deflection (°)
Ort
hogo
nal t
o de
flec
tion
(°)
Parallel to deflection (°)
Ort
hogo
nal
to d
efle
ctio
n (°
)
June 19 2002 Measurement of the p/p ratio using the Moon shadow with the L3 detector (page 9) Jean-Francois PARRIAUD
on behalf of the L3 collaboration
Page 10
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Determination of the angular resolution
Geomagnetic field → horizontal axis.=⇒ Projection on vertical axis: angular resolution only.
-50
0
50
100
150
-3 -2 -1 0 1 2 3
87.32 / 67
Angle from Moon centre (°)
Num
ber
of e
vent
s
λ 122. ±26.resolution 0.39 ±0.10x0 -0.22 ±0.11
-100
-50
0
50
100
150
-3 -2 -1 0 1 2 3
92.07 / 67
Angle from Moon centre (°)
Num
ber
of e
vent
s
λ 100. ±16.resolution 0.18 ±0.05x0 -0.04 ±0.04
Difference with previous estimates due to geomagnetic field.
June 19 2002 Measurement of the p/p ratio using the Moon shadow with the L3 detector (page 10) Jean-Francois PARRIAUD
on behalf of the L3 collaboration
Page 11
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Search for antimatter
Simulation: “anti-shadow” symmetric to Moon shadow.
|pµ| > 100 GeV/c.
Parallel to deflection (°)
Ort
hogo
nal t
o de
flec
tion
(°)
Parallel to deflection (°)
Ort
hogo
nal t
o de
flec
tion
(°)
June 19 2002 Measurement of the p/p ratio using the Moon shadow with the L3 detector (page 11) Jean-Francois PARRIAUD
on behalf of the L3 collaboration
Page 12
L3L 3L3L3L3L3L3L 3L 3L3L3L3L3L3L3L 3L3L 3L3L3L 3L3L3L3L3L 3L3L3L3L3L3L3L 3L3L3L3L 3L3L3L3L 3L3L3L3L3L3L3L3L3L3L3L3L3L3L3L3L3L3L3L3L3L3L 3L3L3L3L3L3L3L3L3L3L3L3L3L 3L3L3L3L 3L 3L 3�
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Measurement of the p/p ratio
|pµ| > 65 GeV/c, deflection coordinates system.
Hypothesis: p, p spectrums with same index.
Maximum likelihood fit:
f(x, y) = ax + by + c︸ ︷︷ ︸plane
−N [G(x0, y0, σ)︸ ︷︷ ︸p deficit
+ r︸︷︷︸p/p ratio
G(−x0,−y0, σ)︸ ︷︷ ︸p deficit
]
=⇒ Moon shadow observation with 8σ significance.
Simulation → uncertainty on the measured ratio.
Preliminary measurement:r = − 0.1 ± 0.15 → r < 0.25 (90% C.L.)
∆lnL 31. 5
Missing events 944. ±320.
x0 0.41◦± 0.14
y0 - 0.05◦± 0.05
r - 0.1 ± 0.15 0
0.025
0.05
0.075
0.1
0.125
0.15
0.175
0.2
0.225
2 4 6 8 10 12 14 16 18 20Missing events (x103)
unce
rtai
nty
on r
atio
June 19 2002 Measurement of the p/p ratio using the Moon shadow with the L3 detector (page 12) Jean-Francois PARRIAUD
on behalf of the L3 collaboration
Page 13
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Conclusion
☛ The Moon shadow has been observed with 8σ significance.
☛ Preliminary measurement of p/p ratio is − 0.1 ± 0.15 for a primary energy between .5 TeV and 1 Te
(from MC).
90% C.L. upper limit is 0.25At the moment, 33% of events reconstructed.
With full statistics, uncertainty on the ratio could be reduced down to 0.09.
☛ HEP detectors can be used for muon astronomy with success.
implementation relatively unexpensive
continuously monitored
designed for 10 years of running
June 19 2002 Measurement of the p/p ratio using the Moon shadow with the L3 detector (page 13) Jean-Francois PARRIAUD
on behalf of the L3 collaboration
Page 14
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Earth-Moon system simulation
Generate protons around the Moon location
and remove protons hitting the Moon
�Generate protons at the Moon location
From the Moon to the Earth
�From the Earth to the Moon
✦ p spectrum ⇐= data µ spectrum and MC
✦ p generated within 0.27◦ from θMoon −∆θp−−−→udefl
✦ p tracked through geomagnetic field (IGRF
model) up to 5 Earth radii from the Earth
✦ p trajectory prolongated → Earth-Moon distance
✦ Check that p hits the Moon
B
North
Earth
L3
Earth
Moon
June 19 2002 Measurement of the p/p ratio using the Moon shadow with the L3 detector (page 14) Jean-Francois PARRIAUD
on behalf of the L3 collaboration
Page 15
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Deflection coordinates system
Moon
Earth
Obs
Moo
n
Udefl
UdeflMoonobs
June 19 2002 Measurement of the p/p ratio using the Moon shadow with the L3 detector (page 15) Jean-Francois PARRIAUD
on behalf of the L3 collaboration
Page 16
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Muon momentum spectrum
pµ / GeV
P3 Dµ(P
) (cm
-2 s
-1 s
r-1 /G
eV2 )
Nottingham 1967Kiel 1971AMH 1971MARS 1975AMH 1979Nottingham 1983MASS 1993CAPRICE 1994CAPRICE 1997
L3+C preliminary
10
0.1
0.2
0.3
0.4
0.5
0.6
102
103
June 19 2002 Measurement of the p/p ratio using the Moon shadow with the L3 detector (page 16) Jean-Francois PARRIAUD
on behalf of the L3 collaboration
Page 17
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Muon charge ratio
Hayman 1962
Nottingham 1984
Nottingham 1971Durgapur 1972Durham 1975
CAPRICE 1994+1997others
L3+C preliminary
pµ / GeV
R µ
only data points with error smaller than 10% are shown1
1.2
1.4
1.6
1.8
2
10 102
103
June 19 2002 Measurement of the p/p ratio using the Moon shadow with the L3 detector (page 17) Jean-Francois PARRIAUD
on behalf of the L3 collaboration