A. Fernández

ACORDE a Cosmic Ray Detector for ALICE

ACORDE is one of the ALICE detectors, presently under construction at CERN. It consists of an array of plastic scintillator counters placed on the three upper faces of the ALICE magnet. It will act as a cosmic ray trigger, and, together with other ALICE sub-detectors, will provide precise information on cosmic rays with primary energies around 1015–1017eV. Here we describe the design of ACORDE along with the present status and integration into ALICE.

Calibration and monitoring of water Cherenkov detectors with stopping and crossing muons

Abstract The Auger Observatory water Cherenkov detectors (WCD) will require that the initial calibration and subsequent monitoring of each of the WCDs be done in a remote way. We present a method to perform these tasks based on the detection of muons decaying inside the detectors and the application of adequate selection cuts. This technique may be complemented with another based on muons crossing the WCDs. Samples of decaying and crossing muon events were obtained with a WCD prototype to demonstrate the viability of the techniques. Three clear peaks of PMT charge distributions were identified. All of them are useful for calibration and monitoring of WCDs: one for stopping muons, one for decay electrons and one for crossing muons. The mean value of the peak found in the decay-electron charge distribution is 0.18 times the corresponding value for vertically crossing muons; likewise, the mean value of the peak in the charge distribution of crossing muons (excluding corner clipping muons) is 6.1 times the value for decay electrons in a tank of our dimensions; finally, the mean value of the peak in the charge distribution of stopping muons is 0.55 times the value for decay electrons. The techniques described can be applied equally well to unsegmented or segmented Auger tanks as each of the three PMTs of an Auger WCD can be self-triggered independently. The experimental data are well reproduced by numerical simulations.

Cosmic Ray Physics at CERN

In recent decades, cosmic ray air showers initiated by high‐energy proton or nucleus collisions in the atmosphere have been studied with large area experiments on the surface of the Earth or with muon measurements deep underground. In principle, these cosmic ray experiments explore two completely different realms of physics, particle astrophysics and particle interaction physics, which are, however, intimately related by the interpretation of the data. In this paper we briefly review the cosmic ray physics activities developed at CERN in the last years. In particular we present some results from a small underground cosmic ray experiment and we discuss the capabilities of ALICE to detect high multiplicity muon events arising from cosmic ray air showers and some other astroparticle phenomena.

Geomagnetic effects on the PMT tubes of the Pierre Auger surface detectors

In this paper we report the geomagnetic field effect on three photomultiplier tube (PMT) candidates for their massive use in the Pierre Auger Observatory surface detector array. The geomagnetic field effect could be manifest in the variation of the response of the PMT after this has been rotated with respect to its own axis on top of the surface detector. We measured the signal given by secondary cosmic rays and by a LED installed in the interior of the tank with one PMT. Data were digitized using a digital oscilloscope and an ADC-CAMAC module. We found no significant variation of the PMT response when the dynode axis direction changes with respect to the geomagnetic field orientation.

Recent results on the operation of a Cherenkov detector prototype for the Pierre Auger observatory

A full-sized water Cherenkov detector (WCD) prototype (cylinder 3.57 m diameter filled with purified water up to a height of 1.2 m) was used to obtain experimental results that validate the concept of remote calibration and monitoring of WCDs based on the use of the natural flux of cosmic ray muons. Two types of events can be used to monitor and to calibrate each of the WCDs: through-going muons (i.e., isolated muons) and decay electrons from muons stopped inside each detector. The different triggers that will be used to obtain these events and the on-line calibration and monitoring histograms are discussed along with the way these data can be used to diagnose component failures of any of the surface stations of the Auger Observatory.

Stability and calibration of a water Čerenkov detector prototype

We present results of studies made with a reduced-scale water Cerenkov detector (WCD) prototype for the Pierre Auger Observatory . This detector is made of high-density polyethylene and was operated continuously for four months. We studied time variations in the amplitude and shape of Cerenkov pulses due to cosmic ray muons and studied the correlation of these parameters with the bacterial population of the water. We also developed and tested a new technique to calibrate and monitor WCDs remotely, based on muons stopping and decaying inside the tank. We conclude that high-density polyethylene tanks fulfill the requirements for use in the water Cerenkov detectors of the Pierre Auger Observatory .

The Mexican participation at the Pierre Auger Observatory: Recent results

I11 this work we present the participations of the Mexican group at development of tile Pierre Auger Observatory. We have been working in both parts of the hybrid proposed for the Auger detector, the fluorescence and the surface detectors. In the part of fluorescence, we have analyzed the resolution of the Hi-Res optical design of the fluorescence detector observatory. We have found a heterogeneus image resolution. We propose to use a lensless Schmidt camera (with spherical image surface) to duplicate the field of view to 30x30 degrees and simultaneously guarantee a resolution of one degree over of the whole field of view. By the Surface Detector, a water Cerenkov detector (WCD) prototype of reduced dimensions (cylinder 1.54 diameter filled with purified water up to 1.20 m high) is used to obtain preliminary experimental results that. validate the concept of remote calibration and monitoring of WCDs.We use muons that stop and decay inside the WCD and, in a complementary way, muons that croos the WCD. We used a moun telescope trigger in order to study the charge distribution of vertical muons, their pulse amplitude decay and the Cerenkov light attenuation lenght of those secondary cosmic muons we include the bacteria population content for the four months of operation to validate the monitoring method.