What we do know about cosmic rays at energies above eV? A.A.Petrukhin Contents 4 th Round Table, December , Introduction. 2. How these CR are investigated. 3. Results and questions. 4. New approach to CR investigations. 5. NEVOD-DÉCOR experiment. 5. Further steps. 6. Conclusion. National Research Nuclear University MEPhI, Russia

Why these energies are interesting? Why these energies are interesting? eV in p-p – interactions corresponds to ~ 1 TeV in the center-of-mass system. Interval – eV corresponds to LHC energies 1.4 – 14 TeV. There are no direct measurements of CR energy spectrum and mass composition above eV. In indirect experiments above eV changes in CR energy spectrum and mass composition have been observed. Introduction

EAS – the single source about PCR at energies above eV. EAS consists of hadrons, muons, electrons, positrons, photons, neutrinos. EAS radiates Cherenkov fluorescent, radio, acoustic radiations. Extensive Air Shower (EAS)

EAS generated of various nuclei

Existing approach to EAS analysis

Results of energy spectrum investigations

1 particle/m 2 s “Knee” “Ankle” Ground based measurements ~ 5  10 4 m 2 KASCADE 0 4km AGASA 100 km 2 Pierre Auger Observatory 50 km 3000 km 2 1 particle/ m 2 year 1 particle/ km 2 year 1 particle/ km 2 century Direct measurements AMS2 Fermi LAT

Peculiarities of CR energy spectrum

Results of mass composition investigations

Energy spectrum of various CR nuclei

CR mass composition at low energies  1.5

Mass composition from N  /N e measurements Mass composition from N  /N e measurements

Jörg R. Hörandel, 2007 Existing explanation of CR spectrum Existing explanation of CR spectrum

Mass composition from X max measurements Mass composition from X max measurements

Conclusion - 1 Satisfactory description of primary CR in the whole measured interval of energies is absent, especially at highest energies. (May be any processes around BH are sources of these CR?) There are contradictions between different mass composition measurements.. One of possible reasons is a short dynamic interval of measured energies (~ 10 2 ) by EAS detectors. Therefore the development of new approaches to CR investigations which can give new information in a wide energy interval is required.

New method of EAS investigations

Inclined EAS detection (local muon density measurements) Advantages: - practically pure muon component; - large area of showers, which increases with energy; - strong dependence of EAS energy on zenith angle.

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

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 !

New technique of Local Muon Density Spectra was realized by means of Experimental complex NEVOD-DECOR Russian-Italian Collaboration National Research Nuclear University MEPhI, Russia Istituto di Fisica dello Spazio Interplanetario, INAF, Torino, Italy Dipartimento di Fisica Generale dell’ Universita di Torino, Italy

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.

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

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

Comparison with other data

Conclusion - 2 A new method of EAS investigations 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. The last result was confirmed in fact in LHC experiment.

Discussion Apparently the change of hadron interaction model at least in multiplicity of secondary particles in nuclei-nuclei collisions has been observed. More interesting is another question: This change of multiplicity is a simple increasing of number of secondary particles (and as the consequence – number of muons) or it is a change of energy distribution in favor of high energies? Muon energy is the single parameter which is not measured at existing EAS arrays. But there are other experimental results which allow get answer this question. They were obtained in BUST and IceCube experiments..

Baksan underground scintillation telescope

Muon energy spectrum

Hermann Kolanoski, 32nd ICRC, 2011, BeijingIceCube

IceCube Collaboration, 32nd ICRC, 2011, Beijing Candidate shower with a high pT muon. The cosmic ray bundle is on the left and the high p T muon is on the right. Muons in IceCube

Patrick Berghaus, 31st ICRC, 2009, Lodz IceCubemuon energy spectrum IceCube muon energy spectrum

Patrick Berghaus, Chen Xu, 32nd ICRC, 2011, Beijing IceCubemuon energy spectrum IceCube muon energy spectrum

Conclusion - 3 New(?) physics in cosmic rays: In CR experiments have been observed: - not only increasing of number of muons in EAS with the increasing of their energies, which has been confirmed in LHC experiments, - but the excess of very high energy muons (>100 TeV)! The excess of very high energy muons (>100 TeV) can be produced in decays of heavy particles (or other states of matter) with mass ~ 1 Tev only. This is a new task for both cosmic ray and LHC experiments and LHC experiments

New approach to EAS investigations

Possibilities of NEVOD-DECOR experiment

Energy deposit of muon bundles

Expected results of muon energy deposit measurements Expected results of muon energy deposit measurements E1E1

Conclusion - 4 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 in cosmic rays. This experiment will start in the beginning of 2012.

Thank you for attention!