Last Update: October 2000

EAS-TOP

Laboratory: Laboratori Nazionali del Gran Sasso (Campo Imperatore)

The Collaboration:

M. Aglietta, B. Alessandro, P. Antonioli, F. Arneodo, L. Bergamasco, M. Bertaina, C. Castagnoli, A. Castellina, A. Chiavassa, G. Cini Castagnoli, B. D’Ettorre Piazzoli, G. Di Sciascio, W. Fulgione, P. Galeotti, P.L. Ghia, M. Iacovacci, G. Mannocchi, C. Morello, G. Navarra, O. Saavedra, G.C. Trinchero, P. Vallania, S. Vernetto, C. Vigorito, S. Valchierotti

INFN Torino, INFN Napoli, INFN Bologna, INFN LNGS, ICG CNR Torino, DFG Universita’ Torino, DSF Universita’ Napoli

+ Collaboration with MACRO and LVD for the coincidences with the underground detectors

- Goal of the experiment
  Study of: cosmic ray primary spectrum and composition in the energy range 1013-1016 eV (i.e. around the "knee" of the primary spectrum, connecting the direct measurements performed through satellite and balloon experiments to the giant arrays energy range), g -ray astronomy, c.r. anisotropies, hadronic interaction models. This is performed through detectors of different components of Extensive Air Showers: electromagnetic (35 modules of scintillators 10 m2 each, distributed over 105 m 2), GeV muons and TeV hadrons (9 layer tracking calorimeter 120 m2), Cerenkov light (8 steering telescopes), and the coincidences with the underground TeV muon detectors (MACRO, LVD). The array is located at Campo Imperatore (2000 m a.s.l.), 30 degrees with respect to the vertical of the underground LNGS laboratories which makes possible the coincidence experiment, and provide the ground level information to interpret the deep underground data.
- Physics achievements

> Main physics results reported on different items are summarized in the following, in connection to the related publications. g-ray astronomy: upper limits from candidate sources (Astrop. Phys., 1994, 3, 1), diffuse radiation (Ap. J., 1992, 397, 148; Astrop. Phys., 1996, 6, 71), detection of the burst from the Crab Nebula on February 23, 1989 (Europhysics Letters, 1990, 15, 81), g-ray bursts (Ap. J., 1996, 469, 305). The explanation of horizontal air showers, and the limit to the UHE extraterrestrial neutrino flux at neutrino energy E n = 105 – 107 GeV (Physics Letters B, 1994, 333, 555). The measurement of cosmic ray anisotropy at Eo ~ 1014 eV, and of the anisotropy effect in solar time due to the motion of revolution of the Earth (Ap.J., 1996, 470, 501). The measurement of the attenuation length of the EAS shower size at the knee, the observation of the knee in the GeV muon component (Nuclear Physics B, 1998, 60B, 105), and of the relative connections; primary composition (Phys. Lett., 1994, 337, 376; Nuovo Cim., 1997, 112B, 139).

- Physics achievements in 1999-2000

> The experiment has been running in full configuration.
> In 1999 main achievements have been obtained on the study of the EAS size spectrum and the cosmic ray energy spectrum in the region 1015-1016 eV (Astrop. Phys., 1999, 10, 1), on some features of hadronic interactions relevant to the understanding of the EAS data: the cross section for large pt jet production in p-N interactions at sqrt(s) ~ 500 GeV in multicore events (Physics Letters B, 1999, 460, 474), the proton attenuation length and the p-air inelastic cross section at sqrt(s) ~ 2 TeV (Nucl. Phys. B, 1999, 75A, 222), the c.r. primary composition and interactions at Eo = 10-100 TeV from the observation of HE muons and atmospheric Cerenkov light in EAS (Nucl. Phys. B, 1999, 75A, 259).
> In year 2000 the relation between the electron and muon sizes around the knee has been studied in detail (Nuclear Phys. B, 2000, 85, 318, SIF Conference Proc., 2000, 68, 3), the final data on the single hadron energy spectrum have been obtained (SIF Conf. Proc., 2000, 68, 11), a new technique for searching for gamma-ray bursts at ~ 10 TeV has been developed (SIF Conference Proc., 2000, 68, 7), and new data have been reported in the search for possible gamma-ray transients through a correlated study of the EAS-TOP and Baksan array (Astrop. Phys., 2000, 14, 189). Some of such results, resulting from very recent analysis, have been published in SIF Conference Proceeding; final papers are under preparation.

- INFN contribution in terms of manpower and financial support:

> 5 INFN Researchers have taken part to different phases of the experiment, the total INFN funding has been 18.177 GL; the experiment has been running under different configurations from 1989 to 2000 and has been dismounted in the summer of 2000.

- Number of publications in refereed journals: 46 (2 in 2000)

- Number of talks to international conferences: 63

- Number of invited talks in international conferences: 7

- Number of undergraduate and doctoral thesis on the experiment:

> - n. 7 Ph. D

> - n. 13 Laurea diplomas.

> - Number of foreigners having holded guest positions in INFN to partecipate to some phases of the experiment: 11

- Leadership role in the experiment

> The experiment is of full italian (INFN-CNR) responsability.
> Spokesperson is G. Navarra from Dipartimento di Fisica Generale of Torino University.

- Innovative instruments

> The experiment has been operating for 10 years with high stability in the difficult ambiental conditions of Campo Imperatore with remote checking and data acquisition, and has thus been planned with the adeguate technology.

- Competing experiments

> KASCADE in Karlsruhe (similar, at sea level, without Cerenkov detectors, with results compatible with respect to EAS-TOP, and interesting for comparing the data at two different atmospheric depths);
> CASA-MIA in Utah (similar mostly devoted to g-ray astronomy);
> Coincidences with high energy muons (i.e. a secondary HE component) represent a unique property of EAS-TOP and the LNGS configuration.

- International committee which has reviewed the experiment:

> The Scientific Committee of the Gran Sasso Laboratories has discussed and reviewed the experiment in the annual meetings of 1993, 1994, 1995, 1996, 1998 (see the meeting minutes).