What superstring or brane phenomenology can be observed in heavy ion collisions at the LHC energy densities. Of course, I am aware that LHC experiments can constrain the conclusions from the superstring theory, e.g. by validating particle spectra of MSSM, so, my question is about effects that more directly hints to the strings or branes themselves and some peculiar nature they have?
You seem to misunderstand the possibilities of ion collisions at LHC.
The aim of the experiments is to create and study the quark gluon plasma, many body state studied by the jets produced:
Jets are “hard probes”, by nature strongly interacting but moving so fast and with so much energy that they are often not completely absorbed by the surrounding quarks and gluons in the quark-gluon plasma. The degree of jet quenching – a figure that emerges in data from millions of collision events – plus the jets' orientation, directionality, composition, and how they transfer energy and momentum to the medium, reveal what’s inside the fireball and thus the properties of the quark-gluon plasma.
Supersymmetry is sought in exchanges in proton proton collisions, sifting through the data to find elementary interactions possible to generate supersymmetric particles. A review of limits of the 7 Tev run is here. There are more data and still there are only limits.