Direct production of lightest Regge resonances

Abstract

We discuss direct production of Regge excitations in the collisions of massless four-dimensional superstring states, focusing on the first excited level of open strings ending on D-branes extending into higher dimensions. We construct covariant vertex operators and identify "universal" Regge states with the internal parts either trivial or determined by the world-sheet SCFT describing superstrings propagating on an arbitrary Calabi-Yau manifold. We evaluate the amplitudes involving one such massive state and up to three massless ones and express them in the helicity basis. The most important phenomenological applications of our results are in the context of low-mass string (and large extra dimensions) scenarios in which excited string states are expected to be produced at the LHC as soon as the string mass threshold is reached in the center-of-mass energies of the colliding partons. In order to facilitate the use of partonic cross sections, we evaluate them and tabulate for all production processes: gluon fusion, quark absorbing a gluon, quark-antiquark annihilation and quark-quark scattering.

Refined partition functions for open superstrings with 4, 8 and 16 supercharges

“…U(1) R neutrality of the latter forbids an s dependence at this point and sets the second argument of the χ SO (3) NS,R characters to unity.…”

“…2 As a result, the partition functions we are considering in this paper do not exhibit a modular invariant property. 3 Open string states also carry Chan-Paton factors. The massless states and their massive excitations that arise from open strings with both endpoints attached to a stack of D branes transform in the adjoint representation of the Chan-Paton gauge group.…”

“…If we had included the grading with a minus sign for spacetime fermions into the trace, we would have a zero here. 3 To illustrate this point, we compare the unrefined partition functions presented in (5.3.37) of [25] and (9.1.14), (9.1.15) of [26]. The former is the partition function we are interested in and it is clear that such a partition function does not possess a modular invariant property.…”

“…The pairing of supermultiplets with opposite (non-zero) U(1) R charges combines Majorana fermions as they the common practice that supermultiplets are referred to through the highest spin therein. The supercharacter J3, [3], for instance, describes U(1) R neutral bosons of spin two and one, and two massive gravitinos of opposite U(1) R charges. 19 The formula for the GSO projected R sector is reliable for positive powers q 1 only and inaccurate at the massless…”

“…[2] for a stable low energy open string vacuum, the Standard Model ++ with two Higgs fields). In addition to the light states, the knowledge of the universal massive string spectrum is also important in order to compute string scattering amplitudes of massive open string states in N 4d = 1 string compactifications [3]. This task is particularly relevant, if the string scale is low compared to the Planck mass, as it is true in compactifications with large extra dimensions [4]: Both the exchange and the production of the lightest string resonances will leave measurable signatures at the LHC if the string scale is sufficiently close to the TeV range [5,6].…”