Sling effect in AA-interactions

1. Sling effect in AA-interactions Contents Erlykin A.D. * Need for the improvement of the interaction model P.N.Lebedev Physical Institute, Moscow, Russia * Direction of improvements Wolfendale A.W. * Sling effect in AA interactions University of Durham, Durham, UK * Implications for UHECR phenomena

2. 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

4. face-on view edge-on view

5. Geometric approach for AA-interactions Cross-section A B Mean number of wounded nucleons A B

6. A bit of geometry = Ellipticity ( definition ) ; for

7. Overlap area for deformed nuclei depends on the impact parameter band the orientation angle a a b non-deformed spherical nucleus b deformed nucleus

8. sintSc-Nas a function ofthe orientation anglea mean for e = 0.9 mean for e = 0.5

9. The number of wounded nucleons varies with the orientation angle a stronger for deformed nuclei

10. 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 nwand in the range of impact parameters b

11. Fluctuations of the number of wounded nucleons • The distribution of the number of wounded nucleons for deformed nuclear fragments becomes wider

12. Interaction rate of deformednuclear fragmentscompared 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

13. Correlation of the cross-section sand the number of wounded nucleons nw e=0.9 e=0.5 e=0

14. 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

15. Longitudinal development of nucleons in the cascade, induced by Fe56, fragmented into Sc45and nucleons

16. Change in the longitudinal profile of Fe-induced cascade * The maximum of the EAS development Xmaxis shifted to the deeper atmosphere, but no more than by 1 gcm-2 at E0 = 1 PeV; * Although the shift of Xmaxis small, the size Ne of the EAS below the maximum increases E0 = 1 PeV

17. 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

18. 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 ?

19. 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

20. 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

21. Excited nuclear fragment has a different shape…

22. Correlation between the number of wounded nucleons and the interaction cross-section • There is the strong correlation between the number of wounded nucleons in the projectile fragment and the interaction cross-section e=0.9 e=0.5

23. Inconsistencies in the results • Primary energy specta and mass compositions derived from different EAS components • Muon and hadron trigger rates in KASCADE <lnA> m , e m ,h

24. <lnA> from different EAS components

25. <lnA> from different EAS components <lnA> from Cherenkov measurements is lower than from on-ground measurements

26. New phenomena • Alignment in gamma-hadron families • Elliptic flow in AA-collisions • Quark-gluon plasma • Centauro events

27. Muons and electrons in Proton and Iron induced EAS

28. P induced showers have more e and h and less m Fe induced showers have less e and h and more m Comparison of P and Fe induced showersat the fixed primary energy 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.

29. Longitudinal development of 1 PeV atmospheric cascades

30. Longitudinal profile of the EAS electron size

31. Triangle diagram Ee + Emn + Eh = Eobs de + dmn + dh = 1 g g dm deg P Fe d h

32. Triangle diagram for 1 PeV EAS

33. 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

34. Central AA-collisions * multiple e+e--production Peripheral AA-collisions * electromagnetic radiation of excited nuclear fragments Theoretical arguments A1 A2 * electromagnetic radiation of QGP ‘Sling’