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Diapositiva 1 - Centro Fermi

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F.Riggi
The telescopes of the EEE
Project
II Conferenza dei Progetti del Centro Fermi
Roma, 19-20 Aprile 2012
Old experiments in cosmic rays
Most old experiments on cosmic rays carried out with
small gas counters (Geiger, ionization chambers,…)
An historical example: the world survey by
H.A. Compton and collaborators (’30s)
Results from 8 expeditions at 69 stations
worldwide
Educational experiments with cosmic rays/1
Still today, many educational experiments in cosmic rays
physics male use of simple detectors, with nice results
A few examples with portable Geiger counters..
The same counter, during a
commercial flight, up to
11000 m altitude..
A school “expedition” to
Mount Etna with a small
Geiger counter, to measure the
altitude dependence of the
muon flux
Two Geiger operated in
coincidence allow to measure
the angular distribution of
cosmics, ~ cos2 Оё
Educational experiments with cosmic rays/2
.. or with small scintillation detectors
Two scintillator tiles arranged
in a telescope configuration or
at some distance apart
Measurement of the East/West asimmetry
Coincidence rate vs distance
Professional experiments make use of large arrays
Correlated events in far detectors allow
to reconstruct extensive air showers
The EEE Project: requirements and solutions
в—Џ Need for an extended array over a large area, ~106 km2
в—Џ Large number of telescopes, in the order of 100
в—Џ Reasonable cost
в—Џ Long term operation required
в—Џ Efficiency close to 100%
в—Џ Reconstruction of muon orientation
в—Џ Optimal time resolution
CHOICE:
Telescopes based on Multigap Resistive Plate Chambers
The MRPC telescopes
в—Џ Each telescope made by 3 MRPC modules, ~ 160 x 80 cm
в—Џ Gas mixture of Freon+SF6
в—Џ Special FE cards for readout and trigger
в—Џ DC/DC converters for HV (В±10 kV) to chambers
в—Џ GPS time-stamp of the collected events
в—Џ VME-based data acquisition
в—Џ Each module provides a two-dimensional
position information
в—Џ Efficiency close to 100% and excellent
time resolution
в—Џ Good reconstruction of the muon orientation
First chambers under test@CERN
MRPC chambers: basic working principles
Each MRPC is a stack of resistive plates,
transparent to the avalanches generated
inside the gas gaps.
Pick-up electrode
Mylar
Carbon layer
glass
glass
The induced signal on ext.electrodes
is the sum over all the gaps
Cathode -10 kV
(-8 kV)
(-6 kV)
glass
glass
glass
glass
Carbon layer
Mylar
Pick-up electrode
(-4 kV)
Gas gaps ~
300 mm
(-2 kV)
Anode 0 V
Developed by the ALICE TOF
group, to achieve excellent time
resolution (40 ps) and efficiency
Building the chambers at CERN..
Construction of chambers started in 2005
at CERN by teams including high-school
teachers and students
All schools have a collection of
similar pictures…
Test beam results at the CERN PS
Exp. setup
Time resolution
Position resolution
Trigger and data acquisition
Trigger
unit
MRPC
Telescope
6-fold
coincidence
GPS Unit
TDCs (144
channels)
USB
connection to
PC
from FE cards
Acquisition and control software based
on Labview
GPS time stamping of the events
Distant telescopes will be
synchronized through GPS time
stamping of individual events
2012
127
Year Day
Seconds
EventTime_1: Year, Day, s, ns
Nanoseconds
EventTime_2: Year, Day, s, ns
Track reconstruction in the telescopes
в—Џ Problems similar as in big experiments, although with reduced multiplicity
Hits in the detector
From hits to clusters
Tracking algorithms
Evaluation of track quality
Geometrical
acceptance
Muon speed
Track length-TOF
Status of the installations
в—Џ Presently installed about 40
telescopes in ~20 sites
в—Џ Most of the telescopes continuosly
running
в—Џ Several telescopes take data since
several years
в—Џ Data storage and analysis started
в—Џ Full involvement of school teams
in the construction, operation and
monitoring of the telescopes
в—Џ A lot of different educational
activities in progress in all the EEE
sites
Possible investigations with a single telescope
Local measurements, with a single telescope, give
several types of information
в—Џ Effect of atmospheric pressure and temperature
в—Џ Survey of cosmic ray flux over large areas and extended periods
в—Џ Correlation to atmospheric weather (clouds)
в—Џ Daily and long term variations
в—Џ Correlation to solar events
в—Џ High-precision angular distributions, effects of building structure
в—Џ Study of multi-muon events
…
Anticorrelation with the atmopsheric pressure
Diurnal and long term variation of the atmospheric pressure
result in a variation of the measured local cosmic ray flux
Counts/5min
Atm.
Press.(mmHg)
Tempo (s)
~ 26 days
~10 days
Angular distributions of cosmic muons
dN/dОё ~ sinОё (dN/dО©) ~ sinОё cos2Оё
Muon radiography
Shielding around the detector produce
absorption effects and may alter the
observed angular distribution
P-3
P-2
P-1
PT
Effect of the
building structure
Multi-muon events
Muon pairs in the same event
ZY-proj
Muon pairs from event-mixing
ZX-proj
Corrected muon pair distribution
A typical 2-tracks event
Correlation to solar events
Catastrophic solar events (Solar flares,…) produce strong
variations of the cosmic ray flux on Earth
Forbush decreases usually
monitored by neutron stations
worldwide
EEE telescopes were able to observe
the solar flare on Feb.2011 !
.. and the new one in March 2012
(see next talks)
An extensive air shower in the atmosphere
An extensive air shower in the atmosphere
An extensive air shower in the atmosphere
An extensive air shower in the atmosphere
An extensive air shower in the atmosphere
An extensive air shower in the atmosphere
An extensive air shower in the atmosphere
Reconstruction of the shower
Correlation between telescopes located within a few
km distance allow to reconstruct extensive air
showers produced by a high energy primary in the
Earth atmosphere
The EEE telescopes
provide not only the
relative arrival time
(through GPS), but also
muon orientation
Better reconstruction
of the shower axis
A shower may spread out over a metropolitan area
1013 eV
1014 eV
COSMOS simulations of the muon
density at various distances from the
shower axis , for proton-induced air
showers
1015 eV
1016 eV
Correlated events with small detectors aside
At small distances, correlation measurements may be
complemented by the use of additional detectors, also
with the aim of checking GPS synchronization
between different sites
Results from EEE telescopes+scintillators at 0 - 450 m
obtained in different EEE sites (see next talks)
Catania, ~40 m
Cagliari, ~40 m
Correlated events from EEE telescopes
Time and orientation correlated events from EEE
telescopes also observed at 25-600 m distances
CERN, ~ 20 m
L’Aquila, ~200 m
Correlated events from EEE telescopes
Time and orientation correlated events from EEE
telescopes also observed at 25-600 m distances
Cagliari, ~520 m
Frascati, ~600 m
Search in progress at larger
distances…
Small evidence at 3 km?
Coincidence rate vs distance
Putting together results from different sites to arrive
to a set of results as a function of the distance
(decoherence curve). In progress…
Take into account:
в—Џ Geometrical acceptance
в—Џ Telescope efficiency
в—Џ Different locations and shielding conditions
Coincidences per day
160
140
Predictions from CORSIKA
for proton-induced showers
under way
Eprimary = 1-108 GeV
О� = 0-70В°
EОј > 0.5 GeV
120
100
80
60
40
20
0
0
200
400
600
Distance between the Telescopes (m)
800
1000
Search for long baseline time and orientation correlations
Origin still to be clarified, if any
Two correlated primary particles
produce two separate showers in
the Earth atmosphere
A single heavy primary undergoes
photodisintegration in the solar
field, with propagation of the two
fragments in the interplanetary
magnetic field
(GZ effect, 1960)
Any evidence for such events?
в—Џ No firm evidence up to now for such effects
в—Џ 4 time and orientation coincident events found at 6 km distance in
110 days running time from ALEPH-L3 detectors
в—Џ A few (4) events observed in 1998-2001 by LAAS Collaboration
(Japan) at 150 and 800 km with small angular deviations (<10В°) and
small time differences (1-100 Ојs)
The EEE Project has the potential to search for such events
The EEE potential to search for such events
Typical distances between EEE sites: 50-1200 km
Time differences need to be corrected according to (Оё, П†) orientation
and relative location of the sites
AQ
BO
CA
CER
CT
Fra
LE
RE
SA
TO
Distribution of EEE
site-to-site distances
AQ
BO
CA
CER
CT
Fra
LE
RE
SA
TO
-
290
515
720
580
85
470
340
240
545
-
630
450
850
325
740
55
525
295
-
835
560
425
785
640
510
685
-
1240
725
1180
395
900
175
-
535
420
900
355
1065
-
490
370
225
550
-
795
290
1010
-
575
235
-
770
-
To be updated with
the new sites…
Two sites at the largest distance: CERN-Catania correlations
CERN
Approximate distance between
the two sites: 1200 km
Catania
Results from a small dataset
Random coincidences
Exp. observed
Only 3 days data taking,
approximately 107 events
in each telescope
W/o condition
on parallel EAS
With condition
on parallel EAS
Improving the situation in the future
Preliminary analyses carried out only on small datasets
в—Џ Reduce as much as possible the correlation time and angular window
Better knowledge of location and orientation of telescopes
Improving the angular resolution for single and 2-tracks events
Take into account equatorial coordinates for distant sites
в—Џ Trigger on local showers for correlation studies
Identify candidate showers from 2-3 telescopes in the same town
Use small side detectors in coincidence with EEE telescopes
в—Џ Select specific incoming shower orientations
в—Џ Search for multiple correlations between >2 sites
Existing sites and collected events allow to improve by a large
factor (105 )
A lot of analysis work awaiting for us…
Conclusions
Large fraction of the telescopes already installed and taking data
Operation of installations and data monitoring in place
Local analyses started in different sites
On going contributions on upgrades of the hardware and software
Use of small detectors for checking, data quality,… in progress
Data analysis to search for long distance correlations to be extended
A lot of educational activities being carried out
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