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String theory predictions for future accelerators

E. Dudas, J. Mourad

TL;DR

Addressing low-string-scale Type I string models with large extra dimensions, the paper analyzes gravitational KK exchange and graviton-emission signatures at future accelerators. It develops a UV-finite framework by a mixed open-closed channel regularization with cutoffs satisfying $\Lambda_o \Lambda_c = M_s^2$, and computes the leading string corrections to the field-theory amplitude for virtual gravitational exchange in $D=4$, as well as exact string tree amplitudes for processes with two or three gauge bosons and a winding/massive graviton, including a universal off-shell graviton form factor $g(p^2)$. The off-shell generalizations and the detailed pole/zero structure from winding/open-string states are presented, linking to brane-bulk couplings and brane-thickness interpretations; the results reduce to field theory in the low-energy limit and provide concrete, testable predictions for collider searches of stringy gravity effects. Together, these findings clarify how string corrections modify gravity-mediated processes at energies below the string scale and illuminate the distinctive signatures (resonances, zeros, and form factors) expected in future accelerator experiments.

Abstract

We consider, in a string theory framework, physical processes of phenomenological interest in models with a low string scale. The amplitudes we study involve tree-level virtual gravitational exchange, divergent in a field-theoretical treatment, and massive gravitons emission, which are the main signatures of this class of models. First, we discuss the regularization of summations appearing in virtual gravitational (closed string) Kaluza-Klein exchanges in Type I strings. We argue that a convenient manifestly ultraviolet convergent low energy limit of type I string theory is given by an effective field theory with an arbitrary cutoff $Λ$ in the closed (gravitational) channel and a related cutoff $M_s^2/Λ$ in the open (Yang-Mills) channel. We find the leading string corrections to the field theory results. Second, we calculate exactly string tree-level three and four-point amplitudes with gauge bosons and one massive graviton and examine string deviations from the field-theory result.

String theory predictions for future accelerators

TL;DR

Addressing low-string-scale Type I string models with large extra dimensions, the paper analyzes gravitational KK exchange and graviton-emission signatures at future accelerators. It develops a UV-finite framework by a mixed open-closed channel regularization with cutoffs satisfying , and computes the leading string corrections to the field-theory amplitude for virtual gravitational exchange in , as well as exact string tree amplitudes for processes with two or three gauge bosons and a winding/massive graviton, including a universal off-shell graviton form factor . The off-shell generalizations and the detailed pole/zero structure from winding/open-string states are presented, linking to brane-bulk couplings and brane-thickness interpretations; the results reduce to field theory in the low-energy limit and provide concrete, testable predictions for collider searches of stringy gravity effects. Together, these findings clarify how string corrections modify gravity-mediated processes at energies below the string scale and illuminate the distinctive signatures (resonances, zeros, and form factors) expected in future accelerator experiments.

Abstract

We consider, in a string theory framework, physical processes of phenomenological interest in models with a low string scale. The amplitudes we study involve tree-level virtual gravitational exchange, divergent in a field-theoretical treatment, and massive gravitons emission, which are the main signatures of this class of models. First, we discuss the regularization of summations appearing in virtual gravitational (closed string) Kaluza-Klein exchanges in Type I strings. We argue that a convenient manifestly ultraviolet convergent low energy limit of type I string theory is given by an effective field theory with an arbitrary cutoff in the closed (gravitational) channel and a related cutoff in the open (Yang-Mills) channel. We find the leading string corrections to the field theory results. Second, we calculate exactly string tree-level three and four-point amplitudes with gauge bosons and one massive graviton and examine string deviations from the field-theory result.

Paper Structure

This paper contains 14 sections, 128 equations, 8 figures.

Table of Contents

  1. Introduction and Summary of the results.
  2. Coupling constants
  3. Virtual gravitational exchange amplitude
  4. One loop type I amplitudes
  5. The one loop amplitude as a sum of box diagrams
  6. The nonplanar amplitude as exchange of closed string modes
  7. Type I ultraviolet regularisation of 10D field theory
  8. Type I ultraviolet regularisation of winding modes in 4D
  9. Couplings of brane states to bulk states
  10. Two gauge bosons - one winding graviton amplitude
  11. Three gauge bosons - one winding graviton amplitude
  12. Jacobi functions and their properties
  13. Box diagrams in 4D
  14. The type I disk amplitude

Figures (8)

  • Figure 1: Tree-level gravitational virtual exchange.
  • Figure 2: The string nonplanar amplitude.
  • Figure 3: The closed channel representation of the amplitude.
  • Figure 4: The open channel representation of the amplitude.
  • Figure 5: The mixed representation of the amplitude where the tree diagrams have a cutoff $\Lambda$ and the box diagrams a cutoff $M_s^2/\Lambda$.
  • ...and 3 more figures