Ultra High Energy Cosmic Rays

1
Ultra High Energy Cosmic Rays New Approach

• A.A.Petrukhin
• Moscow Engineering Physics Institute

C o n t e n t s

1. Problems of UHECR
2. Possible solution
3. Some consequences

2
UHECR spectrum
3
Some remarks

1. From experimental point of view UHECR spectrum is
   the EAS spectrum, but not the primary CR
   spectrum!
2. There are no models which can explain the slopes
   of spectrum unambiguously.
3. All models of CR origin have upper limitations of
   accelerated energies.
4. 16 years ago very interesting model was presented
   at International conference on plasma physics in
   New Delhi, 1989.

4
Model of CR acceleration in plasma pinches 1
B.A.Trubnikov, V.P.Vlasov, S.K.Zhdanov Kurchatov
Institute, Moscow Int. Conf. on Plasma Physics,
New Delhi, India, 1989, v.1, p.257.
The main idea of this model is the following.
In cosmic plasma (of any origin) electrical
discharges "cosmic lightnings" can occur, at
which cylindrical pinches are formed, similar to
laboratory ones.
Two basic instabilities of plasma pinches are
known snaky and neck.
5
Model of CR acceleration in plasma pinches 2
Plasma jets are squeezed out of pinch neck.
These jets are accelerated particle beams.
6
Model of CR acceleration in plasma pinches 3
It was shown that energy distribution of
particles in jets has the following form
which does not depend on pinch sizes, currents in
pinches and other parameters.
These parameters determine a proportionality
coefficient only.
7
Model of CR acceleration in plasma pinches 4

• In the model the well-known equations of plasma
  physics are used only.

• Model has no free parameters except for absolute
  intensity.

• Model predicts for the energy spectrum slope the
  unambiguous value ? 2.73

• Model has no limitation for accelerated particle
  energy since in plasma pinch neck

density ? ? ?, when its radius r ? 0
8
Correlation between contribution of pinch and
other models into CR spectrum 1
Two possible limiting cases

• The pinch mechanism dominates. For example, even
  at SN explosion particles are accelerated mainly
  in plasma pinches.
• 2. The contribution of pinch mechanism is
  small at low energies (below the knee), but can
  be remarkable at higher energies (f.e. above the
  ankle).

9
Pinch mechanism dominates above the ankle only
10
Cut-off influence 1
11
Pinch mechanism dominates
12
Possible explanation
One can suppose that massive short-lived
particles (as resonance states of matter) are
produced in PeV cosmic ray interactions (TeV
energies in the center-of-mass system).
(Analogy ? the "island of stability" which is
expected in transuranium physics around Z 114).
These particles will decay with production of
W? and Z-bosons, which in their turn decay into
hadrons (on average 20 hadrons, mainly pions) ?
70 and leptons (e, ?e ), (?, ?? ), (?, ?? ) ?
30.
13
Consequences for CR energy spectrum
Calculations show that at decays of W, Z0-bosons
with PeV energies, leptons must have very large
energies
Production of three types of VHE neutrinos ?e,
?µ, ?t and VHE 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.
14
Missing energy
15
How to explain the ankle appearance?

• If to explain the knee by inclusion of new
  particles (states of matter) which decay into
  leptons (directly or through W ? and Z 0-bosons),
  
• then the ankle will correspond to critical energy
  for new particles at which probabilities of
  interaction and decay are equal. At higher
  energies, new particles mostly interact and
  missing energy disappears.

16
Cut-off influence-2
?
17
Conclusions

1. Of course the best way for solving of UHECR
   spectrum problem is the solution of the knee
   problem.
2. Independently on the knee problem the detailed
   measurements of UHECR spectrum in a wide interval
   (at least beginning below the ankle) with a
   single EAS array are required.
3. In particular it would be very good to construct
   the central part of North site of Auger
   observatory with smaller distance between
   Cherenkov water tanks.

18
(No Transcript)
19
Other interesting consequences

• The composition of accelerated particles will be
  the same as composition of cosmic plasma, which
  consists mainly of hydrogen.

• Model explains the absence of point sources of
  cosmic rays since pinches, f.e. near Supernova,
  can be oriented in any direction.

• At the same time, generation of particles in
  narrow jets in cylindrical pinches can explain
  the appearance of correlated particles.