The correspondence principle says that an ensemble of highly excited string states is equivalent to a black hole at a certain threshold. I will discuss its theoretical basis and will show our results on the correspondence between a production cross section of rotating black holes and that of string states with fixed angular momentum. I will show that such a black hole/string ball can be possibly produced at LHC and will present how it will be experimentally observed. Following is a part of related references:

T. Matsuo and K. Oda, ``Geometric cross sections of rotating strings and black holes," Phys.Rev.D79, 026003 (2009).

D. Ida, K. Oda and S. C. Park, ``Rotating black holes at future colliders. III. Determination of black hole evolution," Phys.Rev.D73, 124022 (2006);

``Rotating black holes at future colliders: Greybody factors for brane fields," Phys.Rev.D67,064025 (2003).