PowerPointesitys

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EMMA-experiment
(Experiment with MultiMuon Array)
Juho Sarkamo Centre for Underground Physics in
Pyhäsalmi University of Oulu Finland cupp.oulu.fi
Baksan School April 21, 2007
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Outline Introduction Pyhäsalmi Mine and
EMMA Hardware Composition reconstruction
simulations
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• Introduction Pyhäsalmi Mine
• An active zinc and copper mine situated in
  Pyhäsalmi in central Finland.
• Owned by company Inmet Mining.
• Extends down to 1440 metres.
• Spiralling driveway down.
• Several measurements done
• MUG (muon flux at 0m, 90m, 210m, SGO)
• MUD (muon background flux measurements,
  0m-1400m)
• INM-2 (Khlopin Radium Institute)
• Fast neutron background measurements (INR)
• ...
• Available space in several depths (from 85 to
  1440 meters) for room-sized experiments or
  prototypes. These include caverns, repairing
  halls, old lunch room... Plans for a laboratory
  at 1400m.

EMMA at 85 m low-cost pioneer experiment in the
mine
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• Introduction EMMA-experiment
• The goal of EMMA (Experiment with MultiMuon
  Array) is to measure the chemical composition of
  primary cosmic-rays at the 'knee' region.
• The idea of EMMA-experiment is to measure the
  multiplicity and lateral distribution of
  high-energy muons which originate from
  high-energy cosmic-ray collisions in the air.
• Other goals
• muon multiplicity measurements (hadronic
  interaction model testing)
• angular and temporal correlations of cosmic rays
• The experiment will be built in the Pyhäsalmi
  Mine to a depth of 85 m.
• the rock overburden filters out the hadronic and
  electromagnetic component of the air shower
• the depth corresponds to an approximative muon
  energy cutoff of 50 GeV.

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• The knee region of cosmic rays
• The knee
• cosmic-rays of energies 1015 - 1016 eV.
• energy spectrum steepens above the knee
• An explanation of the knee
• cosmic-ray acceleration mechanisms
• cosmic-ray propagation
• unknown high-energy interactions
• Several experiments (KASCADE, EAS-TOPMACRO, ...)
  report a composition change around the knee
  region.
• EMMA employs a new method for composition
  measurement. High statistics muon multiplicity
  experiment at shallow depths.

Cosmic-ray energy spectrum

The knee region
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• Detector setup
• EMMA employs former DELPHI Barrel Muon Chambers
  (MUB)
• position sensitive drift chambers (365?20?1.6
  cm3)
• operable in self-trig mode, position resolution
• 1 cm in drift direction, 3 cm in delay
  line
• non-flammable gas mixture Ar CO2 ( 928 )
• sensitive area of one detector (7 chambers)
• is 2.9 m2
• one-layer units 5 detectors 15 m2
• two-layer units 55 detectors in two layers
  allows track reconstruction
• Detector testing and calibration ongoing in
  Pyhäsalmi.
• Overall detector area of 135 m2 planned.
• Scintillators provided in participation with INR,
  Moscow
• exact design and usage still under investigation.

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The layout
(a view from top)
The array is planned to consist of 6 one-layer
and 3 two-layer units
The experiment will be built on existing caverns
at 85 m
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The layout
(a view from top)
First cabin built Drift chamber tests start in
the summer
The array is planned to consist of 6 one-layer
and 3 two-layer units
The experiment will be built on existing caverns
at 85 m
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Atmosphere inside tent T ? 15C, H ? 65-70, P
lt 1 kW
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SIMULATIONS
Composition reconstruction two-component
description The average lateral
density distribution of gt 50 GeV muons
CORSIKA QGSJET01- simulation by Tomi Räihä
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Composition reconstruction two-component
description The average lateral
density distribution of gt 50 GeV muons
1st Locate the shower axis position
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Composition reconstruction two-component
description The average lateral
density distribution of gt 50 GeV muons
2nd Associate the muon density at the shower
axis to the primary cosmic-ray energy
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Composition reconstruction two-component
description The average lateral
density distribution of gt 50 GeV muons.
3rd Associate the muon density gradient to the
primary cosmic-ray mass
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• Composition reconstruction two-component
  description
• In the following analysis some simplifications
  were made
• all showers assumed vertical
• detector response assumed to be 100
• rock overburden simple muon energy cutoff of 50
  GeV
• The following, yet simplified, includes the
  effects of air shower systematics and realistic
  detector geometry and therefore implies the
  shower reconstruction and the composition
  reconstruction capabilities of EMMA.

ongoing work to establish more realistic
simulations (muon energy loss fluctuations,
electromagnetic sub-showers, detector
efficiencies...)
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Composition reconstruction shower
reconstruction, an example
4 PeV proton initiated air shower hitting close
to the center of the array
a parametrized form of the lateral density
distribution is fitted to the muon hit data

• shower axis position x, y
• shower axis muon density r(1)
• gradient-sensitive parameter R0

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Composition reconstruction shower
reconstruction, an example
4 PeV proton initiated air shower hitting close
to the center of the array
a parametrized form of the lateral density
distribution is fitted to the muon hit data

• shower axis position x, y
• shower axis muon density r(1)
• gradient-sensitive parameter R0

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Composition reconstruction shower
reconstruction, an example
r(1) 2.2 m-2 R0 47.4 m
r(r) m-2
r m
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Composition reconstruction shower axis
uncertainties
4.0 PeV proton initiated shower Average shower
axis reconstruction uncertainties (sizes) vs.
shower axis positions (circles) Typical
accuracies of 3-5 metres in the central part
of the layout for knee energy showers
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Composition reconstruction
Simulated showers of given energies, shower axis
positions distributed uniformly around the
array gt make shower reconstructions gt apply
cuts to select data for composition analysis
For example 1st cut at least one unit has Nm gt
10 (to ensure statistics) 2nd cut Select
showers which have the reconstructed shower axis
position inside a selected area (to select the
best events). Note specific cuts constitute a
bias for composition measurements.
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Composition reconstruction
Responses FEM(r(1),R0)
E 1.0 PeV red, proton blue, iron
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Composition reconstruction
Responses FEM(r(1),R0)
E 1.6 PeV red, proton blue, iron
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Composition reconstruction
Responses FEM(r(1),R0)
E 2.5 PeV red, proton blue, iron
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Composition reconstruction
Responses FEM(r(1),R0)
E 4.0 PeV red, proton blue, iron
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Composition reconstruction
Responses FEM(r(1),R0)
E 6.3 PeV red, proton blue, iron
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Composition reconstruction
Responses FEM(r(1),R0)
E 10.0 PeV red, proton blue, iron
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Composition reconstruction
Responses FEM(r(1),R0)
E 15.8 PeV red, proton blue, iron
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Composition reconstruction a numerical
example Example of spectrum reconstruction,
specific cuts and 1 year steradian of data
with spectral index -2.7 True spectrum (lines)
assumed to be 80-20 proton-iron below 3 PeV
and 20-80 proton-iron above 3 PeV
Data(r(1),R0) SE,M REM FEM(r(1),R0)
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Personnel and Collaborators T. Enqvist, J.
Joutsenvaara, P. Kuusiniemi, J. Narkilahti, J.
Peltoniemi, A. Pennanen, T. Räihä, J. Sarkamo, C.
Shen, P. Keränen, W. Trzaska, T. Jämsén, I.
Usoskin, ... CUPP / University of Oulu (Finland)
, Department of Physics, University of Jyväskylä
(Finland), SGO / University of Oulu (Finland) D.
Linkai, Z. Qingql Institute of High Energy
Physics, Chinese Academy of Sciences, Beijing
(China) L. Bezrukov, I. Dzaparova, S. Karpov, A.
Kurenya, V. Petkov, A. Yanin, ... INR, Russian
Academy of Sciences, Moscow (Russia) H.
Fynbo Department of Physics and Astronomy,
University of Aarhus (Denmark)
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BACKUP SLIDES
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Average shower axis reconstruction uncertainties
vs. shower axis position
4.0 PeV Fe
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Separation of 4 PeV showers in R0
counts
R0
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Muon number separation of proton and iron vs.
distance from shower axis 45 m2
( ltN(p)gt - ltN(Fe)gt ) / s
R / m
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Pyhäsalmi Mine Aerial view
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(r(1), R0) - parametrisation and air shower
systematics
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Muon multiplicity anomaly DELPHI (J. Ridky et
al., Nucl. Phys. (Proc. Suppl.) 138, 295-298,
2005) ALEPH (V. Avati et al., Astropart. Phys.
19, 513, 2003)
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Statistics
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Statistics
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