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Cross sections for production of closed superstrings at high energy colliders in brane world models

Diego Chialva, Roberto Iengo, Jorge G. Russo

TL;DR

The paper tackles missing-energy signatures at high-energy colliders in brane-world string models by computing the total cross section for producing a closed string state from two open strings on a D-brane, exploiting the imaginary part of the forward non-planar open-string amplitude. It provides explicit expressions for the leading ($\sigma_0$) and next-to-leading ($\sigma_1$) contributions up to $\alpha's\le 8$, includes KK graviton and excited string states, and estimates resonance widths to regulate poles. The work translates these string-theory amplitudes into measurable missing-energy cross sections for gluon-gluon and quark-antiquark initial states, derives integrated forms suitable for collider phenomenology, and discusses the impact of extra dimensions and parton distributions. The results offer a quantitative framework to set limits on the string scale $M_s$ and to search for characteristic string-resonance patterns in missing-energy channels at the LHC or future colliders.

Abstract

In brane world string models with large extra dimensions, there are processes where fermion and antifermion (or two gluons) can annihilate producing a light particle (e.g. gluon) carrying transverse momentum and a Kaluza-Klein graviton or an excited closed string that propagates in the extra dimensions. In high energy colliders, this process gives a missing momentum signature. We compute the total cross section for this process within the context of type II superstring theory in the presence of a D brane. This includes all missing energy sources for this string theory model up to s=8M_s^2, and it can be used to put new limits on the string scale M_s.

Cross sections for production of closed superstrings at high energy colliders in brane world models

TL;DR

The paper tackles missing-energy signatures at high-energy colliders in brane-world string models by computing the total cross section for producing a closed string state from two open strings on a D-brane, exploiting the imaginary part of the forward non-planar open-string amplitude. It provides explicit expressions for the leading () and next-to-leading () contributions up to , includes KK graviton and excited string states, and estimates resonance widths to regulate poles. The work translates these string-theory amplitudes into measurable missing-energy cross sections for gluon-gluon and quark-antiquark initial states, derives integrated forms suitable for collider phenomenology, and discusses the impact of extra dimensions and parton distributions. The results offer a quantitative framework to set limits on the string scale and to search for characteristic string-resonance patterns in missing-energy channels at the LHC or future colliders.

Abstract

In brane world string models with large extra dimensions, there are processes where fermion and antifermion (or two gluons) can annihilate producing a light particle (e.g. gluon) carrying transverse momentum and a Kaluza-Klein graviton or an excited closed string that propagates in the extra dimensions. In high energy colliders, this process gives a missing momentum signature. We compute the total cross section for this process within the context of type II superstring theory in the presence of a D brane. This includes all missing energy sources for this string theory model up to s=8M_s^2, and it can be used to put new limits on the string scale M_s.

Paper Structure

This paper contains 8 sections, 73 equations, 3 figures.

Table of Contents

  1. Introduction
  2. Total cross section for open+open to closed string
  3. Limits on cross sections and widths of open string states
  4. The cross-sections.
  5. Cross section for missing energy processes in colliders
  6. Analysis of the parton cross sections
  7. Concluding remarks
  8. Acknowledgements

Figures (3)

  • Figure 1: $t$- and $u$-channels for the process: a+b $\to$ c+C (missing, closed-string state).
  • Figure 2: Process gluon+gluon $\to$ closed-string(missing)+gluon (continuous line) and quark+anti-quark $\to$ closed-string(missing)+gluon (dashed line), cross-section in units of $\alpha '$, as a function of $\alpha ' s$.
  • Figure 3: Process gluon+gluon $\to$ closed-string(missing)+gluon in the case of two large and four small (with radii $R=\sqrt{\alpha '}$) extra dimensions.