Study of highly excited string states at the Large Hadron Collider

In TeV-scale gravity scenarios with large extra dimensions, black holes may be produced at future colliders. Good arguments have been made for why general relativistic black holes may be just out of reach of the Large Hadron Collider (LHC). However, in weakly coupled string theory, highly excited string states—string balls—could be produced at the LHC with high rates and decay thermally, not unlike general relativistic black holes. In this paper, we simulate and study string ball production and decay at the LHC. We specifically emphasize the experimentally detectable similarities and differences between string balls and general relativistic black holes at a TeV scale.

Figure 1

Energy scales for black holes and string balls in the context of the LHC energy. Not shown are the compactification scale or the ultraviolet cutoff scale.

Figure 2

Ratio of emission into a single bulk mode to a single brane mode for highly excited strings. The ratio decreases with increasing $n$.

Figure 3

Total proton-proton cross section versus Planck scale for the production of black holes (solid curves) and string balls plus black holes (dashed curves) for various numbers of extra dimensions $n$. The black hole cross section increases with increasing $n$. The string ball cross section decreases with increasing $n$.

Figure 4

Total proton-proton cross section versus string scale for the production of black holes (solid curves) and string balls plus black holes (dashed curves) for various numbers of extra dimensions $n$. The black hole cross section increases with increasing $n$.

Figure 5

Integrated proton-proton cross section versus minimum mass threshold for the production of black holes and string balls plus black holes for three extra dimensions.

Figure 6

Multiplicity distribution of visible primary particles emitted from a) black holes with $7.5<M<14\mathrm{TeV}$ and b) string balls and black holes with $3<M<14\mathrm{TeV}$, for $n=3$, $M_{\mathrm{s}}=1\mathrm{TeV}$, $M_D=1.5\mathrm{TeV}$, and $g_{\mathrm{s}}=0.37$.

Figure 7

Scalar sum of transverse momentum of all the visible particles from a) black holes with $7.5<M<14\mathrm{TeV}$ and b) string balls and black holes with $3<M<14\mathrm{TeV}$, for $n=3$, $M_{\mathrm{s}}=1\mathrm{TeV}$, $M_D=1.5\mathrm{TeV}$, and $g_{\mathrm{s}}=0.37$.

Figure 8

Missing transverse momentum in a) black holes events with $7.5<M<14\mathrm{TeV}$ and b) string balls and black holes events with $3<M<14\mathrm{TeV}$, for $n=3$, $M_{\mathrm{s}}=1\mathrm{TeV}$, $M_D=1.5\mathrm{TeV}$, and $g_{\mathrm{s}}=0.37$.

Figure 9

Distribution of the highest transverse momentum jet from the decays of a) black holes with $7.5<M<14\mathrm{TeV}$ and b) string balls and black holes with $3<M<14\mathrm{TeV}$, for $n=3$, $M_{\mathrm{s}}=1\mathrm{TeV}$, $M_D=1.5\mathrm{TeV}$, and $g_{\mathrm{s}}=0.37$.

Figure 10

Distribution of the highest transverse momentum lepton from the decays of a) black holes with $7.5<M<14\mathrm{TeV}$ and b) string balls and black holes with $3<M<14\mathrm{TeV}$, for $n=3$, $M_{\mathrm{s}}=1\mathrm{TeV}$, $M_D=1.5\mathrm{TeV}$, and $g_{\mathrm{s}}=0.37$.