Transcript Document

23rd ECRS, 3 – 7 July 2012
Muon problem in UHECR investigations
A.A.Petrukhin, A.G.Bogdanov, R.P.Kokoulin
National Research Nuclear University MEPhI, Russia
Contents:
1. Introduction
2. Muon number measurements
3. Muon energy measurements
4. Possible explanation of results
5. Conclusion
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:
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”.
M.Fukushima: “esp. muon (hard) sector is un-healthy”.
P.Lipary: “The muon problem”.
etc.
But really this problem begins at lower energies.
Primary Cosmic Ray Energy < 1015 eV
This PCR energies correspond to muon energies < 100 TeV
At these energies no serious deviations from predictions.
PCR energies in the interval 1015 – 1017 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 1017 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 = 65º : 1016 – 1018 eV
θ = 50º : 1016 – 1017 eV
Large angles: around 1018 eV
Comparison with other data
 > 75
10
-2
-1
E dN/dE / 10 , eV m s sr
-1
Only
protons
o
S
Q2
Q1
E1.9
E1.6
 > 80
o
DECOR-2010
S
Q2
E1.9
Q1
E1.6
3
24
2
Only
iron
AGASA
HiRes-1
HiRes-2
Auger-2011 (combined spectrum)
TA-2011 (surface detectors)
1
17.5
18.0
18.5
19.0
log 10 (E, eV)
19.5
Muons in Auger
Results
of muon energy measurements
above 100 TeV
Baksan underground scintillation telescope
0.1
4
-1
-1
E dN/dE, cm s sr GeV
2
BUST data
-2
3
Frejus, 1994
MACRO, 1995
LVD, 1998
Artyomovsk, 1988
Baksan, 1992
MSU, 1994
Baksan (pair meter), 2009
model 1 usual  from , K
-3
model 2 usual  + prompt (R = 10 )
-3
model 3 usual  + prompt (R = 3*10 )
model 4 usual  + VHE
3
0.01
3
10
4
2
1
5
10
10
E, GeV
6
10
IceCube data – 2009
IceCube data – 2011
Possible 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
S. Yoshida, Neutrino Conference, 2012
Conclusion
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!