F Riggi The telescopes of the EEE Project

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 (’ 30 s) 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, ~ cos 2 θ

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 ● Need for an extended array over a large area, ~106 km 2 ● Large number of telescopes, in the order of 100 ● Reasonable cost ● Long term operation required ● Efficiency close to 100% ● Reconstruction of muon orientation ● Optimal time resolution CHOICE: Telescopes based on Multigap Resistive Plate Chambers

The MRPC telescopes ● Each telescope made by 3 MRPC modules, ~ 160 x 80 cm ● Gas mixture of Freon+SF 6 ● Special FE cards for readout and trigger ● DC/DC converters for HV (± 10 k. V) to chambers ● GPS time-stamp of the collected events ● VME-based data acquisition ● Each module provides a two-dimensional position information ● Efficiency close to 100% and excellent time resolution ● 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 The induced signal on ext. electrodes is the sum over all the gaps Cathode -10 k. V (-8 k. V) (-6 glass Carbon layer Mylar Pick-up electrode k. V) (-4 k. V) Gas gaps ~ 300 mm (-2 k. V) 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 Event. Time_1: Year, Day, s, ns Nanoseconds Event. Time_2: Year, Day, s, ns

Track reconstruction in the telescopes ● 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 ● Presently installed about 40 telescopes in ~20 sites ● Most of the telescopes continuosly running ● Several telescopes take data since several years ● Data storage and analysis started ● Full involvement of school teams in the construction, operation and monitoring of the telescopes ● 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 ● Effect of atmospheric pressure and temperature ● Survey of cosmic ray flux over large areas and extended periods ● Correlation to atmospheric weather (clouds) ● Daily and long term variations ● Correlation to solar events ● High-precision angular distributions, effects of building structure ● 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/5 min Atm. Press. (mm. Hg) Tempo (s) ~ 26 days ~10 days

Angular distributions of cosmic muons d. N/dθ ~ sinθ (d. N/dΩ) ~ sinθ cos 2θ

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 e. V 1014 e. V COSMOS simulations of the muon density at various distances from the shower axis , for proton-induced air showers 1015 e. V 1016 e. V

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… day 160 Coincidences per 140 Take into account: ● Geometrical acceptance 120 100 ● Telescope efficiency 80 ● Different locations and shielding conditions 60 40 20 Predictions from CORSIKA 0 0 100 200 300 400 500 600 700 for proton-induced showersbetween the Telescopes (m) Distance under way Eprimary = 1 -108 Ge. V Θ = 0 -70° Eμ > 0. 5 Ge. V 800 900 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? ● No firm evidence up to now for such effects ● 4 time and orientation coincident events found at 6 km distance in 110 days running time from ALEPH-L 3 detectors ● A few (4) events observed in 1998 -2001 by LAAS Collaboration (Japan) at 150 and 800 km with small angular deviations (<10°) and small time differences (1 -100 μs) 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 (θ, φ) orientation and relative location of the sites AQ AQ BO CA CER CT Fra LE RE SA TO Distribution of EEE site-to-site distances 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 ● 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 ● 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 ● Select specific incoming shower orientations ● 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