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 ISVHECRI6-12 Sept. 2004

Pylos, Greece

13 ISVHECRI

6 – 12 Sept. 2004

Pylos, Greece

Two possible explanations of the knee in measured Ne 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 = Epr EEAS

EASenergy

primaryenergy

E 2 E 1

missingenergy

E

knee

N

E 0

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

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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(Ne) and decreasing Xmax(Ne) dependencies, which are explained now as the heaving of composition.

13 ISVHECRI

6 – 12 Sept. 2004

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 Z0-bosons, which in their turn decay intohadrons (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. 2004

Pylos, Greece

Calculations show that at decays of new particles with PeV energies (directly or through W , Z0-bosons), leptons will get very large energies.

Consequences for EAS spectrum

Production of three types of VHE neutrinos (νe, νµ, ντ) 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. 2004

Pylos, Greece

Centauros – (hadron cascades without electromagnetic ones) violate isotopic invariance in strong interaction. But in week interaction at decays W and Z0-bosons isospin is not conserved.

Consequences for VHE interaction – 1

Secondary particle multiplicity (nh) Production of secondary particles through W and Z0-bosons can change multiplicity, increase fluctuations in EAS development and imitate young showers at decreasing nh and showers from nuclei at increasing nh.

VHE muons (> 100 TeV) which are produced in decays of W and Z0-bosons can explain:

– all experiments in which excess of VHE muons was observed;

– some unusual results in hadron experiments (penetrating cascades, Anti-Centauros, etc.).

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Pylos, Greece

Hadron-muon cascade

h h

I

X

In thick detectors muons can

– imitate long-flying and penetrating particles

– increase measured absorption length of hadron cascades

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Pylos, Greece

If Mx 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 thereare no limitations for Chew-Frautschi diagram application .

Mx ~ 1 TeV correspond to J ~ 106

A resonance state with so large spin can be considered as a quasi-classical object.

1236

1950

2420

?2455

?2250

2350?

2030 2100

18301765

1385 1520

1115

2 4 1086M 2, GeV2

32

72

152

192

J

2850

3230

?

?

Positive parity

Negative parity

106

106 Mx

Chew – Frautschidiagram

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Pylos, Greece

Decays of resonance states with very large moment

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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 m2; T > 500 r. l.; Nlayers ~ several tens.

Cherenkov Water Detectors:

Baikal, AMANDA, ANTARES, NEMOThe 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

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Pylos, Greece

VHE muon detection in CWD

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Pylos, Greece

cosmic ray particle(proton with 1016 eV energy)

14N (nucleus of atmospheric atom)

first interactionnew particles,new state of matter

EAS(extensive air shower)

"Andyrchi"shower array

BUST(Baksan

UndergroundScintillationTelescope)

usual muons high-energy muon

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Pylos, Greece

cosmic ray particle(proton with 1016 eV energy)

14N (nucleus of atmospheric atom)

first interactionnew particles,

new state of matter

EAS(extensive air shower)

BARS (Big liquid-ARgonSpectrometer)

shower array

high-energy muon

usual muons

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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).