Preliminary measurement of the all-particle cosmic-ray energy
spectrum with AIROBICC (0.5 - 5 PeV),
by J. Cortina, A. Moralejo and F. Arqueros
(postscript file).
Monte Carlo Simulation of the HEGRA Cosmic Ray Detector Performance
by S. Martinez, F. Arqueros et al. [in Nucl. Instr. Meth. A, 357 (1995)
pp. 567-579]
Models of the scintillator and wide-angle air Cherenkov (AIROBICC) arrays of the HEGRA experiment are described here. Their response to extensive air showers generated by cosmic rays in the 10 to 1000 TeV range has been assessed using a detailed Monte Carlo simulation of air shower development and associated Cherenkov emission. Protons, gamma-rays and oxygen and iron nuclei have been considered as primary particles. For both arrays, the angular resolution as determined from the Monte Carlo simulation is compared with experimental data. Shower size N_e can be reconstructed from the scintillator signals with an error ranging from 10% (N_e=2x10^5) to 35% (N_e=3x10^3). The energy threshold of AIROBICC is 14 TeV for primary gammas and 27 TeV for protons and an angular resolution of 0.25 degrees can be obtained. The measurement of the Cherenkov light at 90 m from the shower core provides an accurate determination of primary energy E_0 as far as the nature of the primary particle is known. For gammas an error in the energy prediction ranging from 8% (E_0 = 500 TeV) to 15% (E_0 = 20 TeV) is achieved. This detector is therefore a powerful tool for gamma-ray astronomy.
Click HERE to get the postscript file.
Preliminary measurement of the all-particle cosmic-ray energy
spectrum with AIROBICC (0.5 - 5 PeV),
by J. Cortina, A. Moralejo and F. Arqueros
(postscript file).
Determination of the Depth of Maximum Development and Primary Energy
of Cosmic Ray Showers with AIROBICC
by J. Cortina et al (HEGRA Collaboration)
[Contribution to ICRC Rome Sept 1995]
The array AIROBICC samples the Cherenkov light produced by a cosmic ray shower at core distances r < 150m. According to a detailed simulation of cosmic ray showers in the range 10 - 1000 TeV, the lateral distribution of the Cherenkov light allows us to measure the depth of maximum development with an error lower than 30 g/cm2 and the electromagnetic energy of the shower with an error of about 7 % for 100 TeV incident particles. By using an appropiate correction based on the height of maximum development, an accurate measure of the primary hadron energy can be achieved independently of the nucleus nature. We predict an energy resolution of about 20 % at 100 TeV.
Click HERE to get the postscript file.
The Wide Angle Air Cerenkov Detector AIROBICC at La Palma
[Contribution to ICRC Rome Sept 1995]
The actual status of the wide angle air-Cerenkov detector AIROBICC located at the HEGRA experiment (La Palma, Canary islands, Spain) is presented. The AIROBICC detector is designed to perform studies on VHE/UHE gamma-ray astronomy and on the chemical composition of the cosmic rays based on its excellent angular resolution and low energy threshold. Future developments are oriented to considerably lower the energy threshold and to improve the gamma/hadron separation.
Click HERE to get the postscript file.
Status of the HEGRA Experiment at La Palma
[Contribution to ICRC Rome Sept 1995]
A status report of the HEGRA experiment at La Palma is presented. A brief description of its several subarrays aimed to make combined measurements of the different components of the extended air showers in the energy range 1 TeV - 10 PeV is given.
Click HERE to get the postscript file.
A Search for Gamma Ray Bursts in the UHE Range Above 25 TeV
with the HEGRA Detector in the 92/93 Data
[Contribution to ICRC Rome Sept 1995]
The HEGRA Collaboration has searched for gamma emission above 25 TeV from potencial gamma ray bursters falling in the acceptance window of the wide angle air Cerenkov detector AIROBICC, which is a part of the HEGRA experiment. Data from March 1992 to March 1993 were analyzed with special interest in those data coincident with CGRO/BATSE gamma ray burst detection.
Click HERE to get the postscript file.
An Improved Search for Gamma Radiation from Cosmic Point Sources
Using a gamma/hadron Separation Procedure on the AIROBICC 92/93 Data
[Contribution to ICRC Rome Sept 1995]
The HEGRA Collaboration has searched for gamma-ray emission above 65 TeV from cosmic point sources with the wide angle Cherenkov detector AIROBICC which is a part of the HEGRA cosmic ray detector complex on La Palma. The threshold of the studied sample is much higher than the pure trigger threshold of AIROBICC because a good reconstruction of the shower parameters is needed to allow for gamma/hadron separation, which has not yet been done. The analysis procedure is described and results will be presented at the conference.
Click HERE to get the postscript file.
Separation of Gamma and Proton Showers using the Lateral Distribution
of Cherenkov Light at several Observatory Depths
by C. Portocarrero, S. Martinez and F. Arqueros
[Contribution to ICRC Rome Sept 1995]
A simulation of the development of gamma and hadron showers in the energy range 1-10000 TeV has been carried out. Radial distributions of the Cherenkov light detected at observatory depths ranging from 500 to 1000 g/cm2 have been studied. Capabilities of the angle-integrating Cherenkov technique for separation of gamma and proton initiated showers as a function of the observation altitude are discussed.
Click HERE to get the postscript file.
A Method for Separation of Gamma and Hadron Initiated Air Showers
with Angle-Integrating Cherenkov Arrays
by F. Arqueros, A. Karle, E. Lorenz, S. Martinez, R. Plaga and M. Rozanska
[Contribution to ICRC Rome Sept 1995]
The angle-integrating Cherenkov technique provides a promising new approach to ground-based gamma-ray astronomy in an energy range just above that accesible by air-Cherenkov telescopes. A method for gamma/hadron separation usable in angle-integrating Cherenkov arrays is presented. As an example we apply this method in a full quantitative detail to the existing AIROBICC detector.
Click HERE to get the postscript file.
Present status of the measurement of the all-particle
cosmic-ray energy (HEGRA internal report 11/29/95),
by J. Cortina, A. Moralejo and F. Arqueros
(Click HERE to get the postscript file).
Update of the measurement of the all-particle cosmic ray
differential spectrum (HEGRA internal report 02/23/96)
by J. Cortina, A. Moralejo and F. Arqueros
(Click HERE
to get the postscript file).
Preliminary Moon and Sun Shadows (July 1996)
Reports on the Source Search, (mainly on
nearby AGNs) and related stuff. (July 1996)
Report on the search for TeV gamma emission from 12 nearby AGNs in
the AIROBICC 92/93 data (HEGRA internal report)
by J.L. Contreras, A. Moralejo. Last updated July 2 1996.
Search for gamma emission in the energy range 50 - 100 TeV from 12 nearby AGNs in AIROBICC March 92 - March 93 data. No evidence has been found. A 1.8 sigma excess is observed in a high quality sample with no gamma/hadron separation cut. In a sample with somewhat relaxed quality cuts (although with similar angular resolution) containing 35% more events, the excess is of only 1.6 sigma. The excess vanishes when a gamma/hadron separation cut is applied in the parameter log10(Ns/L90). Flux upper limits on the gamma flux from these sources are presented.
Click HERE to get the postscript file.
Preliminary plots of the GRS1915
analysis with CT2 data. (JJG Beteta July 25th 1996)
Chemical composition studies (July 1996 )
Effect of the scintilation huts saturation on the NKG fit.
report.ps ,
plot1.ps and
plot2.ps
(Jan 1997)
Preliminary results on 95/96 AIR data ( 5 May 97 )
Crab 95/96 .
Methods for determining the primary energy of cosmic ray showers
by J. Cortina, F. Arqueros, E. Lorenz
[J. Phys. G.: Nucl. Part. Phys. 23 (1997) 1733-1749].
Monte Carlo simulations of cosmic rays showers in the atmosphere have been used to develop three new methods for measuring the energy of the primary particles in the 10^13 - 10^16 eV range independently of the cosmic ray nature. Both the electron number and the Cherenkov light density near the hump position (beyond the hump also) are found to accurately measure the primary energy, provided an appropiate correction based on the depth of the shower maximum is applied. The shower maximum can be estimated from the slope of the radial distribution of the Cherenkov light. In addition the simultaneous measure of the muon number and the Cherenkov light also provides a very accurate measure of the primary energy. All these parameters can be determined with the aid of presently existing arrays of particle and light counters. Therefore a very precise measure of the cosmic ray all-particle spectrum independent of the features of the chemical composition is made practicable.
Click HERE to get the postscript file.
Simulación de cascadas de muy alta energía para el proyecto
The MAGIC Telescope., Tesina J.C. González
(fichero ps gzipeado, 432 Kb).
Identificación de emisión gamma de Muy Alta
Energía con telescopios Cherenkov, Tesina J.J. García Beteta
(fichero ps gzipeado, 560 Kb).
Slides of the talk "Estado y
nuevos resultados del experimento HEGRA", JL Contreras,
Las Palmas 1997 (ps.gz file 780 Kb)
Methods for the energy
determination of cosmic ray showers, by J Cortina, F. Arqueros
and E. Lorenz, contribution to the ICRC Durban 1997 (.ps.gz file, 30 kB).
J. Cortina's PhD thesis,
"Medida del Espectro y la Composición Química
de los Rayos Cósmicos en el rango de 300 TeV a 30 PeV"
(Measurement of Cosmic Ray Spectrum and Chemical Composition
in the 300 TeV to 30 PeV Energy Range). Universidad Complutense
de Madrid, December 1997.
(gzipped postcript file, 500 kB).
Draft on the search for GRBs in AIR 1992-93 data
(L. Padilla, Jan 98)
Slides of the talk
"Point Source Search with AIROBICC" .
ECRS Alcalá 1998 ( ps.gz file 250 Kb )
2d plots around the crab for 1994 and
1995 (ps.gz file 37 kB)
Polarization poster
(Contreras, Calle & Cortina) ECRS Alcalá July 1998
(ps.gz file 77 kB)
Cosmic Ray Spectrum and Chemical
Composition in the 300 TeV - 10 PeV with the HEGRA arrays, by
J. Cortina... A. Moralejo et al,
contribution to ECRS Alcalá July 1998
(ps.gz file 78 kB)