1. 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
Baksan School 2007, 21st of April

2. Outline: Introduction: Pyhäsalmi Mine and EMMA Hardware
Composition reconstruction: simulations
Baksan School 2007, 21st of April

3. 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
Baksan School 2007, 21st of April

4. 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.
Baksan School 2007, 21st of April

5. The knee region of cosmic rays:
cosmic-rays of energies 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-TOP+MACRO, ...) 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
Baksan School 2007, 21st of April

6. 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 ( 92:8 )
sensitive area of one detector (7 chambers)
is ~ 2.9 m2
one-layer units: 5 detectors ~ 15 m2
two-layer units: 5+5 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.
Baksan School 2007, 21st of April

7. Baksan School 2007, 21st of April

8. The experiment will be built on existing caverns at 85 m
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
Baksan School 2007, 21st of April

9. The experiment will be built on existing caverns at 85 m
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
Baksan School 2007, 21st of April

10. Baksan School 2007, 21st of April

11. Baksan School 2007, 21st of April

12. Atmosphere inside tent: T  15°C, H  65-70%, P < 1 kW
Baksan School 2007, 21st of April

13. Composition reconstruction: two-component description
SIMULATIONS:
Composition reconstruction: two-component description
The average lateral density distribution of > 50 GeV muons
CORSIKA
QGSJET01-
simulation
by Tomi Räihä
Baksan School 2007, 21st of April

14. Composition reconstruction: two-component description
The average lateral density distribution of > 50 GeV muons
1st: Locate the shower axis position
Baksan School 2007, 21st of April

15. Composition reconstruction: two-component description
The average lateral density distribution of > 50 GeV muons
2nd: Associate the muon density at the shower axis
to the primary cosmic-ray energy
Baksan School 2007, 21st of April

16. Composition reconstruction: two-component description
The average lateral density distribution of > 50 GeV muons.
3rd: Associate the muon density gradient
to the primary cosmic-ray mass
Baksan School 2007, 21st of April

17. 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...)
Baksan School 2007, 21st of April

18. air shower hitting close to the center of the array
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
Baksan School 2007, 21st of April

19. air shower hitting close to the center of the array
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
Baksan School 2007, 21st of April

20. Composition reconstruction: shower reconstruction, an example
r(1) = 2.2 m-2
R0 = 47.4 m
r(r) [m-2]
r [m]
Baksan School 2007, 21st of April

21. 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
Baksan School 2007, 21st of April

22. Composition reconstruction
Simulated showers of given energies, shower axis positions distributed uniformly
around the array
=> make shower reconstructions
=> apply cuts to select data for composition analysis
For example:
1st cut:
at least one unit has Nm > 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.
Baksan School 2007, 21st of April

23. Composition reconstruction Responses FEM(r(1),R0)
E = 1.0 PeV
red, proton
blue, iron
Baksan School 2007, 21st of April

24. Composition reconstruction Responses FEM(r(1),R0)
E = 1.6 PeV
red, proton
blue, iron
Baksan School 2007, 21st of April

25. Composition reconstruction Responses FEM(r(1),R0)
E = 2.5 PeV
red, proton
blue, iron
Baksan School 2007, 21st of April

26. Composition reconstruction Responses FEM(r(1),R0)
E = 4.0 PeV
red, proton
blue, iron
Baksan School 2007, 21st of April

27. Composition reconstruction Responses FEM(r(1),R0)
E = 6.3 PeV
red, proton
blue, iron
Baksan School 2007, 21st of April

28. Composition reconstruction Responses FEM(r(1),R0)
E = 10.0 PeV
red, proton
blue, iron
Baksan School 2007, 21st of April

29. Composition reconstruction Responses FEM(r(1),R0)
E = 15.8 PeV
red, proton
blue, iron
Baksan School 2007, 21st of April

30. 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%
above 3 PeV
Data(r(1),R0) = SE,M REM × FEM(r(1),R0)
Baksan School 2007, 21st of April

31. 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)
Baksan School 2007, 21st of April

32. BACKUP SLIDES
Baksan School 2007, 21st of April

33. Average shower axis reconstruction uncertainties vs
Average shower axis reconstruction uncertainties vs. shower axis position
4.0 PeV Fe
Baksan School 2007, 21st of April

34. Separation of 4 PeV showers in R0
counts R0
Baksan School 2007, 21st of April

35. ( <N(p)> - <N(Fe)> ) / s
Muon number separation of proton and iron vs. distance from shower axis
45 m2
( <N(p)> - <N(Fe)> ) / s
R / m
Baksan School 2007, 21st of April

36. Pyhäsalmi Mine: Aerial view
Baksan School 2007, 21st of April

37. (r(1), R0) - parametrisation and air shower systematics
Baksan School 2007, 21st of April

38. ”Muon multiplicity anomaly”
DELPHI: (J. Ridky et al., Nucl. Phys. (Proc. Suppl.) 138, , 2005)
ALEPH: (V. Avati et al., Astropart. Phys. 19, 513, 2003)
Baksan School 2007, 21st of April

39. Baksan School 2007, 21st of April

40. Baksan School 2007, 21st of April

41. Baksan School 2007, 21st of April

42. Baksan School 2007, 21st of April

43. Statistics
Baksan School 2007, 21st of April

44. Statistics
Baksan School 2007, 21st of April