NEVOD-DECOR experiment: results and future A.A.Petrukhin for Russian-Italian Collaboration Contents MSU, May 16, New method of EAS investigations 2. Experimental complex NEVOD-DECOR 3. Results of muon bundle investigations 4. EAS muon energy measurements 5. Proposal of NEVOD-DECOR-EAS experiment National Research Nuclear University MEPhI, Russia Istituto di Fisica dello Spazio Interplanetario, INAF, Torino, Italy Dipartimento di Fisica Generale dell’ Universita di Torino, Italy

Question: Why relatively small experimental complex NEVOD-DECOR is included in the list of 1 square km arrays? Answer: New method of EAS investigations is used. Introduction Introduction

New method of EAS investigations

Methods of EAS investigations Methods of EAS investigations Number of electrons N e (in fact, mixture of charged particles) Number of muons, N  Energy deposit of EAS core, E h Cherenkov radiation flux, F ch Fluorescence radiation flux, F f Local muon density, D  Muon bundle energy, E  New!

EAS particle measurements Absorber

Contribution of different distances to total number of muons in EAS and to local muon density spectrum Enhanced sensitivity to the central part of the shower (forward interaction region) !

Inclined EAS detection

μ-EAS transverse section VS zenith angle Number of detected EAS depends on: shower array dimensionsshower dimensions only

Traditional EAS detection technique (E ~ eV) EAS counters (~ 1 m 2 ) ~ 500 m

E ~ eV, θ=80º ~ 10 km Muon detector Local muon density spectra detection technique

Contribution of primary energies at different zenith angles Wide angular interval – very wide range of primary energies !

Experimental complex NEVOD-DECOR

General view of NEVOD-DECOR complex Side SM:8.4 m 2 each σ x  1 cm; σ ψ  1° Coordinate-tracking detector DECOR (~115 m 2 ) Cherenkov water detector NEVOD (2000 m 3 )

A typical muon bundle event in Side DECOR ( 9 muons, 78 degrees) X-projection Y-projection

Muon bundle event (geometry reconstruction)

A “record” muon bundle event X-projection Y-projection

Muon bundle event (geometry reconstruction)

Results of muon bundle investigations

DECOR data. Muon bundle statistics Muon multiplicity Zenith angle range (*) Live time, (hour) Number of events  330 – 60   530 – 60   1030 – 60   3  60   5  60   10  60   10  75  (*) For zenith angles < 60°, only events in two sectors of azimuth angle (with DECOR shielded by the water tank) are selected.

DECOR data. Distribution in multiplicity

DECOR data. Distribution in zenith angle

Effective primary energy range Lower limit ~ eV (limited by DECOR area). Upper limit ~ eV (limited by statistics).

Comparison with calculations Primary “all-particle” spectrum: Power type “all-particle” spectrum with the knee at 4 PeV Below the knee: dN/dE = 5.0 (E, GeV)  2.7 cm -2 s -1 sr -1 GeV -1 ; Above the knee: steepening to (   1) = 3.1. CORSIKA simulation of 2D muon LDF: CORSIKA – QGSJET 01c + GHEISHA 2002; SIBYLL FLUKA b Primary protons and iron nuclei EMF was taken into account.

Low angles: around the “knee” θ = 50 º : – eV θ = 65 º : – eV Large angles: around eV

Conclusion-1 A new method of EAS investigations, based on local muon density spectrum measurements, allows investigate cosmic ray energy spectrum in very wide interval from to eV and even higher. The following results were obtained: detection of the knee (this can be considered as energy scale calibration), observation of the second knee, some excess of muon bundles in comparison with predictions, which increases with energy.

Possible explanations The excess of local muon density with the increase of energy in the interval – eV can be explained by three reasons: progressively heavier CR mass composition; progressive deficit of muons in simulated EAS; inclusion of new processes of muon generation. In the last case, muons with very high energy may appear. Therefore measurements of energy deposit of EAS muon component can give information about such muons.

EAS muon energy measurements

Existing approach to EAS analysis

New approach to EAS analysis

Response of NEVOD for muon bundles

Energy deposit of muon bundles

Dependence of muon energy deposit on zenith angle

Dependence of muon energy deposit on local muon density

Average energy of EAS muons in dependence on zenith angle and local muon density

Proposal of NEVOD-DECOR-EAS experiment

Calibration Telescope System (CTS)

CTS response for EAS with energy eV

CTS response for EAS with energy eV

Proposal of EAS array around NEVOD-DECOR

Cluster on the roof of one building

NEVOD EAS Results of EAS simulation (10 16 eV)

Conclusions-2 Measurements of local muon density spectra with coordinate detector DECOR and muon bundle energy deposit with Cherenkov water detector NEVOD compose a new promising method of the search of new processes of muon generation. The addition of a traditional shower array to NEVOD- DECOR complex will open new possibilities, since it allows observe EAS axes. Of course, construction of one more shower array is scarcely expedient. But the use of existing shower array (f.e., from completed KASCADE-GRANDE experiment) is many times preferable.

Thank you for attention!