 The knee problem The knee and unusual events at PeV energies  Unusual events at PeV energies  Possible explanation  Consequences for EAS spectrum  Consequences for VHE interactions  How to check new approach  Conclusions Contents A.A.Petrukhin Moscow Engineering Physics Institute 13 ISVHECRI 6-12 Sept Pylos, Greece

13 ISVHECRI 6 – 12 Sept Pylos, Greece  Two possible explanations of the knee in measured N e distribution (primary spectrum or interaction change) in the first paper (Khristiansen & Kulikov, 1958) were discussed. The knee problem  For the second version, it is necessary to explain where is the difference between primary and EAS energies  The inclusion of new physical processes is limited by large cross section, which is necessary to change energy spectrum slope.  Therefore the cosmophysical models of the knee appearance dominate.  E = E pr  E EAS Missing energy definition.  However many unusual phenomena had been detected at PeV energies during the last tens years which can evidence for new physics.

13 ISVHECRI 6 – 12 Sept Pylos, Greece  In hadron experiments: Unusual phenomena at PeV energies  In EAS investigations: It is important: Unusual events appear at PeV energies of primary particles. Since these phenomena are well-known, list them only  halos, alignment, penetrating cascades, centauros (Pamir-Chacaltaya);  long-flying component, anti-centauros (Tien-Shan).  In muon experiments:  excess of VHE (~ 100 TeV) single (MSU) and multiple (LVD) muons;  observation of VHE muons (Japan, NUSEX), the probability to detect which is very small.  the increasing N  (N e ) and decreasing X max (N e ) dependencies, which are explained now as the heaving of composition.

13 ISVHECRI 6 – 12 Sept Pylos, Greece Possible explanation  Let us suppose that massive short-lived particles (as resonance states of matter) are produced in PeV cosmic ray interactions. These particles will decay with production of W  and Z 0 -bosons, which in their turn decay into hadrons (on average 20 hadrons, mainly pions)  70% and leptons (e, e ), ( ,  ), ( ,  )  30%. (Analogy  the "island of stability" which is expected in transuranium physics around Z = 114).  This idea can explain many unusual phenomena in cosmic rays.

13 ISVHECRI 6 – 12 Sept Pylos, Greece Calculations show that at decays of new particles with PeV energies (directly or through W , Z 0 -bosons), leptons will get very large energies. Consequences for EAS spectrum Production of three types of VHE neutrinos (ν e, ν µ, ν τ ) and muons gives a missing energy, since the energy of these particles is not measured by existing EAS arrays. This missing energy can explain the knee appearance in EAS spectrum.

13 ISVHECRI 6 – 12 Sept Pylos, Greece  Centauros – (hadron cascades without electromagnetic ones) violate isotopic invariance in strong interaction. But in week interaction at decays W  and Z 0 -bosons isospin is not conserved. Consequences for VHE interaction – 1  Secondary particle multiplicity (n h ) Production of secondary particles through W  and Z 0 -bosons can change multiplicity, increase fluctuations in EAS development and imitate young showers at decreasing n h and showers from nuclei at increasing n h.  VHE muons (> 100 TeV) which are produced in decays of W  and Z 0 -bosons can explain: – all experiments in which excess of VHE muons was observed; – some unusual results in hadron experiments (penetrating cascades, Anti-Centauros, etc.).

13 ISVHECRI 6 – 12 Sept Pylos, Greece Hadron-muon cascade In thick detectors muons can – imitate long-flying and penetrating particles – increase measured absorption length of hadron cascades

13 ISVHECRI 6 – 12 Sept Pylos, Greece If M x is a resonance state of hadron matter, Chew – Frautschi diagram allows to evaluate its spin J Consequences for VHE interaction – 2 This is very unusual value, but there are no limitations for Chew-Frautschi diagram application. M x ~ 1 TeV correspond to J ~ 10 6 A resonance state with so large spin can be considered as a quasi-classical object. Chew – Frautschi diagram

13 ISVHECRI 6 – 12 Sept Pylos, Greece Decays of resonance states with very large moment

13 ISVHECRI 6 – 12 Sept Pylos, Greece The only way – to find excess of VHE muons. There are the following possibilities for that: How to check this hypothesis? S > 1000 m 2 ; T > 500 r. l.; N layers ~ several tens.  Cherenkov Water Detectors: Baikal, AMANDA, ANTARES, NEMO The best is NESTOR, since one half of PMs will be directed upward. 1. Direct measurements of muon energy spectrum by means of Pair meter technique. 2. Investigations of correlations between spatial-energy distributions of muons, generated in EAS with energies below and above the knee.  Possible experiments: BUST + Andyrchi; BARS + EAS; NEVOD + DECOR + EAS

13 ISVHECRI 6 – 12 Sept Pylos, Greece VHE muon detection in CWD

13 ISVHECRI 6 – 12 Sept Pylos, Greece

13 ISVHECRI 6 – 12 Sept Pylos, Greece

13 ISVHECRI 6 – 12 Sept Pylos, Greece Apparently investigations in cosmic rays evidence for a new physics existence at PeV energies of cosmic rays (TeV energies in the center-of-mass system). Conclusion  To carry out the detailed analysis of available experimental data from single point of view in order to obtain characteristics of new physics, which can be checked in future LHC experiments (NEEDS-2). What is necessary?  To get independent proof of production of new physical objects at energies above the knee by means of VHE muon detection. or  To wait for LHC results (not so interesting and even pessimistic perspective for cosmic ray physics).