Production of light stringy states

Abstract

Abstract:We discuss the direct production of light stringy states. Those states correspond to the lightest stringy excitations localized at the intersection of two D-brane stacks and their mass can be parametrically smaller than the string scale. Thus in a low string scale scenario one may observe stringy signatures at LHC even in the absence of the usual string resonances. We compute the tree level string scattering amplitude involving two gauge bosons and two such light stringy states. We give the squared amplitude summed over all polarization and gauge configuration and eventually apply the result to the quark sector of a D-brane realization of the Standard Model.

Revisiting light stringy states in view of the 750 GeV diphoton excess

“…We have further investigated light massive string states that appear at D-brane intersections [62][63][64][65]. For small angles they can be parametrically lighter than standard Regge excitations.…”

“…In this paper, our attention goes towards a different direction. At the intersection of two D-brane stacks there exists a whole tower of stringy excitations with the same quantum numbers [62][63][64][65]. The lowest state can be massless (for a specific value of the intersecting angles) and the rest are massive with masses proportional to the angle of the intersection in which they live (see fig.…”

Yukawas of light stringy states (at D-brane intersections)

“…If the string scale M s is at a few TeV range and some angles between the branes are very small, these copies can be very light (light stringy states) and they might be visible in future experiments [66][67][68][69]. Even though the tower of massive stringy states looks like KK towers, there are differences.…”

Yukawa couplings for light stringy states

“…As a consequence, semi-realistic D-brane configurations predict massive copies for all matter fields of the Standard Model. If the string scale M s is at a few TeV range, these copies can be very light (light stringy states) and they might be visible at LHC [66][67][68][69]. In [1] we compute Yukawa couplings between light stringy states and massless ones.…”