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String Photini at the LHC

Asimina Arvanitaki, Nathaniel Craig, Savas Dimopoulos, Sergei Dubovsky, John March-Russell

TL;DR

This paper explores how string theory’s rich extra-dimensional topology naturally yields many unbroken RR U(1)s whose photini mix with the MSSM bino in low-energy SUSY. This mixing expands the neutralino sector and generates a broad range of LHC signatures, including LOSP decays to photini, inter-photini transitions, displaced vertices, and potentially multiple invisible masses, depending on mixing and mass splittings. It also analyzes collider bounds, cosmological constraints, and scenarios with gravity or gauge mediation, highlighting how photini can be used as indirect evidence for a string vacuum with topologically complex compactifications. The work underscores the need for novel mass-determination techniques and collider analyses to distinguish photini scenarios from other multi-neutralino models like NMSSM.

Abstract

String theories with topologically complex compactification manifolds suggest the simultaneous presence of many unbroken U(1)'s without any light matter charged under them. The gauge bosons associated with these U(1)'s do not have direct observational consequences. However, in the presence of low energy supersymmetry the gauge fermions associated with these U(1)'s, the "photini", mix with the Bino and extend the MSSM neutralino sector. This leads to novel signatures at the LHC. The lightest ordinary supersymmetric particle (LOSP) can decay to any one of these photini. In turn, photini may transition into each other, leading to high lepton and jet multiplicities. Both the LOSP decays and inter-photini transitions can lead to displaced vertices. When the interphotini decays happen outside the detector, the cascades can result in different photini escaping the detector leading to multiple reconstructed masses for the invisible particle. If the LOSP is charged, it stops in the detector and decays out-of-time to photini, with the possibility that the produced final photini vary from event to event. Observation of a plenitude of photini at the LHC would be evidence that we live in a string vacuum with a topologically rich compactification manifold.

String Photini at the LHC

TL;DR

This paper explores how string theory’s rich extra-dimensional topology naturally yields many unbroken RR U(1)s whose photini mix with the MSSM bino in low-energy SUSY. This mixing expands the neutralino sector and generates a broad range of LHC signatures, including LOSP decays to photini, inter-photini transitions, displaced vertices, and potentially multiple invisible masses, depending on mixing and mass splittings. It also analyzes collider bounds, cosmological constraints, and scenarios with gravity or gauge mediation, highlighting how photini can be used as indirect evidence for a string vacuum with topologically complex compactifications. The work underscores the need for novel mass-determination techniques and collider analyses to distinguish photini scenarios from other multi-neutralino models like NMSSM.

Abstract

String theories with topologically complex compactification manifolds suggest the simultaneous presence of many unbroken U(1)'s without any light matter charged under them. The gauge bosons associated with these U(1)'s do not have direct observational consequences. However, in the presence of low energy supersymmetry the gauge fermions associated with these U(1)'s, the "photini", mix with the Bino and extend the MSSM neutralino sector. This leads to novel signatures at the LHC. The lightest ordinary supersymmetric particle (LOSP) can decay to any one of these photini. In turn, photini may transition into each other, leading to high lepton and jet multiplicities. Both the LOSP decays and inter-photini transitions can lead to displaced vertices. When the interphotini decays happen outside the detector, the cascades can result in different photini escaping the detector leading to multiple reconstructed masses for the invisible particle. If the LOSP is charged, it stops in the detector and decays out-of-time to photini, with the possibility that the produced final photini vary from event to event. Observation of a plenitude of photini at the LHC would be evidence that we live in a string vacuum with a topologically rich compactification manifold.

Paper Structure

This paper contains 15 sections, 23 equations, 3 figures.

Table of Contents

  1. Introduction and Summary
  2. Phenomenology
  3. The photino lagrangian
  4. Photini signatures at the LHC
  5. Collider Bounds on String Photini
  6. Cosmology of String Photini
  7. Photino qua LSP
  8. Photino decay into a nonthermal sector
  9. Photino decay into a thermal sector
  10. Light Photini from Gauge Mediation
  11. Astrophysical signatures of light photini
  12. Discussion
  13. Origin of mixing
  14. The scale of SUSY breaking
  15. Conclusions

Figures (3)

  • Figure 1: Different decay channels for both the LOSP decay into photini and interphotini transitions: via $Z$, Higgs, and sfermion.
  • Figure 2: The existence of multiple photini states lighter than the bino -- and mixing with MSSM neutralinos via the bino -- may modify MSSM cascade decay chains to the LSP.
  • Figure 3: The LHC signatures of multiple photini states at the LHC as a function of the photino-bino mixing $\epsilon_i$ and mass splittings $\delta m_i$.