Probing the Geometry of Warped String Compactifications at the Large Hadron Collider

Warped string compactifications, characterized by the nonsingular behavior of the metric in the infrared (IR), feature departures from the usual anti–de Sitter warped extra dimensions. We study the implications of the smooth IR cutoff for Randall-Sundrum- (RS-)type models. We find that the phenomenology of the Kaluza-Klein gravitons (including their masses and couplings) depends sensitively on the precise shape of the warp factor in the IR. In particular, we analyze the warped deformed conifold, find that the spectrum differs significantly from that of RS, and present a simple prescription (a mass-gap ansatz) that can be used to study the phenomenology of IR modifications to 5D warped extra dimensions.

Figure 1

KS (solid blue line) and RS (dashed black line) warp factors $f(r)$ as a function of the radial coordinate $r$.

Figure 2

Normalized KK graviton wave functions for the zero mode (solid red line) and for the first KK mode of the AdS (dashed black line) and KS (solid blue line) geometries. Inset: The second KK modes for RS (dashed black line) and KS (solid blue line).

Figure 3

${\ell }^{+}{\ell }^{-}$ (left) and $t\overline{t}$ (right) invariant mass distributions for KS (black solid line) with hierarchy $r_{\mathrm{tip}}=2\times {10}^{-14}$ (masses and couplings given in Table ) and RS (dashed red line) with hierarchy $r_{\mathrm{tip}}=8\times {10}^{-16}$ (masses given in Table , with ${\Lambda }_{\mathrm{KK}}=2\mathrm{TeV}$). The SM backgound (dot-dashed green line) is $Z$, $\gamma \to {\ell }^{+}{\ell }^{-}$, and gluon $\to t\overline{t}$, respectively. In generating these plots, we have assumed that all standard model fields are confined to the IR brane.