A.A.Petrukhin, A.G.Bogdanov, R.P.KokoulinA.A.Petrukhin, A.G.Bogdanov, R.P.Kokoulin

National Research Nuclear University MEPhI, RussiaNational Research Nuclear University MEPhI, Russia

Muon problem in UHECR investigationsMuon problem in UHECR investigations

Contents:

1. Introduction

2.Muon number measurements

3.Muon energy measurements

4.Possible explanation of results

5.Conclusion

23rd ECRS, 3 – 7 July 2012

Introduction Introduction

Muon problem – the excess of muon number in UHECR experiments compared to calculations – in many talks at International Symposium on Future Detections in UHECR Physics (13 – 16 February, CERN) was discussed:

But really this problem begins at lower energies.

A.Yushkov (Auger): “Deficit of muons in simulations, harder muon spectra in data”.

P.Sokolsky: “Muon content of showers in HiRes/MIA higher than expected”.

P.Lipary: “The muon problem”.

M.Fukushima: “esp. muon (hard) sector is un-healthy”.

etc.

Primary Cosmic Ray Energy < 10Primary Cosmic Ray Energy < 101515 eV eV

This PCR energies correspond to muon energies < 100 TeV At these energies no serious deviations from predictions.

PCR energies in the interval 10PCR energies in the interval 101515 – 10 – 101717 eV eV

In this interval the increasing N/Ne - ratio in EAS experiments compared to calculations is observed.

This increasing can be explained by changing the mass composition in favor of heavy nuclei.

This change is in a good agreement with galactic model of GR origin which is dominating model for these energies.

PCR above 10PCR above 101717 eV eV

At transition from compact EAS arrays to giant ones some difficulties of comparison of experimental data obtained at different arrays appear. Of course, the best approach is to obtain necessary data in one experiment.

Experiment NEVOD-DECOR (Oscar Saavedra talk at today session) gives such possibility, since the results in the interval 1015 – 3 1018 eV were obtained at a single array by the same methods of data treatment.

Low angles: around the “knee” θ = 50º : 1016 – 1017 eV

θ = 65º : 1016 – 1018 eV Large angles: around 1018 eV

17.5 18.0 18.5 19.0 19.5

1

10

Q1

S

E1.6E1.9

Q2

Q1

S

E1.6

E1.9Q2

> 80 o

Onlyiron

AGASA HiRes-1 HiRes-2 Auger-2011 (combined spectrum) TA-2011 (surface detectors)

E 3

dN

/dE

/ 1

0 24 , e

V 2 m

-2 s

-1 s

r -1

log 10

(E, eV)

Onlyprotons

DECOR-2010 > 75 o

Comparison with other data Comparison with other data

Muons inMuons in AugerAuger

Results Results of muon energy measurementsof muon energy measurements

above 100 TeVabove 100 TeV

BaksanBaksan underground scintillation telescopeunderground scintillation telescope

103 104 105 106

0.01

0.1

Frejus, 1994 MACRO, 1995 LVD, 1998 Artyomovsk, 1988 Baksan, 1992 MSU, 1994 Baksan (pair meter), 2009 model 1 usual from , K

model 2 usual + prompt (R = 10-3)

model 3 usual + prompt (R = 3*10-3) model 4 usual + VHE

E3 dN

/dE

, c

m-2 s

-1 s

r-1 G

eV2

E, GeV

1

2

3

4

BUST dataBUST data

IceCube data – 2009 IceCube data – 2009

IceCube data – 2011 IceCube data – 2011

Possible decision of muon problemPossible decision of muon problem

Apparently it is possible to develop some interaction model which can explain the excess of total number of muons.

But for explanation of excess of muons with energy > 100 TeV new process of muon generation is required. Since 1999 we develop a new approach to explanation of various results of cosmic ray investigations, in which production of new massive (~ TeV) state of matter in nuclei-nuclei interaction (e.g., a blob of QGM) is considered.

This approach can explain excess of both total muon number and muon number with energy > 100 TeV.

- spectrum- spectrum

S. Yoshida, Neutrino Conference, 2012

ConclusionConclusion

Of course available statistics is not too big to announce that new physics in cosmic rays is discovered.

But the increasing amount of new experimental data which appeared during last years gives hope that, may be, in the 2nd century the CR investigations at energies > 1015 eV will be performed on a new basis.

Thank you for your attention!Thank you for your attention!