Transcript Sling effect: its implications in UHECR phenomena

Sling effect in AA-interactions
Erlykin A.D.
P.N.Lebedev Physical Institute,
Moscow, Russia
Wolfendale A.W.
University of Durham,
Durham, UK
Contents
* Need for the improvement
of the interaction model
* Direction of improvements
* Sling effect in AA interactions
* Implications for UHECR
phenomena
Sling effect
Sling effect is connected with rotation and deformation
of the nuclear fragment emerged after the peripheral
nucleus-nucleus ( AA ) interaction
Sling effect is used for the formation
of polarized nuclear beams of low intensity
at sub-GeV energies
face-on view
edge-on view
Geometric approach
for AA-interactions
Cross-section
A
B
1
3
1
3
   ( RA  RB  )2
Mean number of wounded nucleons
 pB
Soverlap
SB S A
n A
A
A
 AB
 ABS A
SA
 pA
Soverlap
S ASB
B
nw  B
B
B
 AB
 ABSB
SB
A
w
A
B
A bit of geometry
4
3
R
3
=
Ellipticity  
a 
R
1-  
2
1
6

; c  R 1- 
for
2

1
3
4 2
a c
3
c2
1- 2
a
( definition
)

    R 1 
  0.9   0.76 geom
2
2

1
6
Overlap area for deformed nuclei depends
on the impact parameter b
and the orientation angle a
b
a
non-deformed spherical
nucleus
b
deformed nucleus
int

Sc-N as a function of
the orientation angle
mean for   0.5
a
mean for   0.9
The number of
wounded nucleons
varies with the
orientation angle a
stronger for deformed
nuclei
The mean number of wounded nucleons
as a function of the impact parameter b
The distribution of the
number of wounded
nucleons nw is wider
for deformed nuclei
both in the range of nw
and in the range of
impact parameters b
Fluctuations of the number
of wounded nucleons

The distribution of
the number of
wounded nucleons
for deformed
nuclear fragments
becomes wider
Interaction rate of deformed nuclear fragments
compared with that for spherical fragments



Attenuation of
deformed fragments is
not exponential
Non-exponentiality
increases with the
ellipticity
There is an excess of
fragments at the large
depth of absorber
Correlation of the cross-section  and
the number of wounded nucleons nw
=0.9
=0.5
=0
Consequences of the geometric approach
* Mean cross-section of the spinning and
polarized nuclear fragment is smaller than
that of non-deformed spherical fragment
* There are fluctuations of the overlap
( interaction ) area even for the fixed
impact parameter
Longitudinal development of nucleons in
56
the cascade, induced by Fe , fragmented
45
into Sc and nucleons
Change in the longitudinal
profile of Fe-induced cascade
E0 = 1 PeV
* The maximum of the
EAS development Xmax
is shifted to the deeper
atmosphere, but no
more than by 1 gcm-2
at E0 = 1 PeV;
* Although the shift of
Xmax is small, the size Ne
of the EAS below the
maximum increases
Possible consequences for high energies
( if the ellipticity of the nuclear fragment
increases with energy )




higher elongation rate
heavier primary mass composition
shift of the GZK-cutoff to higher
energies
higher isotropy of arrival directions
Depth of the EAS maximum
That is what
can be expected
(ER = 71 gcm-2)
Could sling effect
give such an increase
of the elongation rate
?
Conclusions


Sling effect slows down the development of
the atmospheric cascade and makes it more
penetrative
Apparently the shift of the nucleus-induced
cascade at the PeV energy due to a sling
effect is small for moderate spins of the
nuclear fragments
Conclusions


At the moment it is not possible to make
accurate estimates of the sling effect due to
the lack of experimental data. If the spin of
the fragment increases with energy this effect
can be important at ultra-high energies
Hadrons are also composite objects and the
sling effect can be important for their
attenuation at ultra-high energies
Excited nuclear fragment has
a different shape…
Correlation between the number of wounded
nucleons and the interaction cross-section

0.9
0.5
There is the strong
correlation between
the number of
wounded nucleons
in the projectile
fragment and the
interaction crosssection
Inconsistencies in the results

Primary energy specta and mass
compositions derived from different
EAS components
m ,h

<lnA>
m,e
Muon and hadron trigger rates in
KASCADE
<lnA> from different
EAS components
<lnA> from different
EAS components
<lnA> from Cherenkov
measurements is lower
than from on-ground
measurements
New phenomena




Alignment in gamma-hadron families
Elliptic flow in AA-collisions
Quark-gluon plasma
Centauro events
Muons and electrons in Proton
and Iron induced EAS
Comparison of P and Fe induced showers
at the fixed primary energy

P induced showers

Fe induced showers
have more e and h
have less e and h
and less m
and more m
The lighter mass composition for e,m-based analysis and the
heavier mass composition for h,m-based analysis means that
observed showers have more e, less m and even less h than
the models predict.
Longitudinal development
of 1 PeV atmospheric cascades
Longitudinal profile of the
EAS electron size
Triangle diagram
Eeg+ Emn + Eh = Eobs
deg  dmn  dh  1
dm
dg
P
Fe
dh
Triangle diagram
for 1 PeV EAS
Recommedations to modify
the interaction model



To increase ( by a few percent ) the energy
transfer to the EAS electromagnetic component
To slow down the cascade development at its
initial stages in order to shift ( by 20-30 gcm-2)
Xmax into the deeper atmosphere
The most promising way to introduce these
changes is to make a more sophisticated
AA-interaction model
Theoretical arguments

Central AA-collisions
* multiple e+e--production
A1

Peripheral AA-collisions
* electromagnetic radiation
of excited nuclear fragments
A2
* electromagnetic radiation
of QGP
‘Sling’