[Paper Review] 3- and 2-body supersymmetric processes: predictions, challenges and prospectives

Francesca Borzumati, Jae Sik Lee+1 more|ArXiv.org|Jun 25, 2002

Particle physics theoretical and experimental studies65 references3 citations

TL;DR

This paper investigates 3- and 2-body supersymmetric processes in R-parity-violating models, focusing on charged Higgs and slepton production at hadron colliders. It shows that neutrino mass constraints from one- and two-loop diagrams strongly limit lepton-number-violating couplings, reducing slepton production cross sections to sub-percent levels, while still allowing detectable signals under specific parameter choices at the LHC.

ABSTRACT

The processes subject of this talk are: 1) the 2 --> 3 processes contributing, together with the 2 --> 2 one to the hadron-collider production of a charged Higgs boson in association with a t-quark; 2) the 2 --> 2 and 2 --> 3 processes giving rise to the hadron-collider strahlung of a charged slepton from a t-quark in R_p-violating models in which lepton-number-violating trilinear couplings largely dominate over bilinear ones; 3) 3-body neutralino and chargino decays in similar R_p-violating scenarios. The significance of the R_p-violating processes is critically assessed against implications from neutrino physics. Contributions to neutrino masses arising at the tree level, at the one- and two-loop levels are reviewed. Comments are also made on the production of sneutrinos via gluon fusion and on the decay of sneutrinos into photons pairs, and on the influence that constraints from neutrino physics have on these processes.

Motivation & Objective

• To assess the viability of 2→2 and 2→3 processes for producing charged Higgs bosons and charged sleptons in R_p-violating supersymmetric models at hadron colliders.
• To evaluate the impact of neutrino physics constraints—particularly from one- and two-loop contributions to neutrino masses—on the allowed parameter space of R_p-violating couplings.
• To determine whether slepton signals can be distinguished from charged Higgs signals in final states, especially in multi-b-jet and leptonically decaying topologies.
• To explore the production mechanisms of sneutrinos via gluon fusion and their decay into photon pairs, and to assess their detectability under current constraints.
• To examine the role of flavor-violating couplings λ′_i3j and λ_i3j in slepton production and their potential to mimic charged Higgs signatures.

Proposed method

• Analyzes 2→2 and 2→3 elementary processes such as gb→tH⁻ and gg,qq→tH⁻b̄ for charged Higgs production, and gq̄→t~ℓ_i for slepton strahlung in R_p-violating models.
• Evaluates production cross sections using leading-order QCD calculations, incorporating top-quark Yukawa coupling y_t and tanβ as large parameters.
• Applies one-loop and two-loop diagrams to compute neutrino mass contributions from trilinear R_p-violating couplings λ′_i33, λ_i33, and A′_i33.
• Derives model-independent bounds on λ′_i33 and λ_i33 from neutrino mass constraints, showing that two-loop contributions can impose stronger limits than one-loop ones.
• Compares final-state topologies—especially multi-b-jet and τν final states—between charged Higgs and slepton decays to assess signal distinguishability.
• Assesses the potential for sneutrino production via gluon fusion and decay into γγ, considering parameter space constraints from neutrino physics.

Experimental results

Research questions

• RQ1 To what extent do one- and two-loop contributions to neutrino masses constrain the R_p-violating couplings λ′_i33 and λ_i33 in supersymmetric models?
• RQ2 Can charged slepton signals at the LHC be distinguished from charged Higgs signals, especially when both decay into τν final states?
• RQ3 How do neutrino physics constraints affect the production cross sections of sneutrinos via gluon fusion and their decay into photon pairs?
• RQ4 What is the impact of flavor-violating couplings λ′_i3j on slepton production cross sections, and how do they compare to those from λ′_i33?
• RQ5 Can two-loop contributions to neutrino masses evade the constraints from one-loop diagrams, and what are the resulting bounds on the couplings?

Key findings

• One-loop contributions to neutrino masses constrain λ′_i33 and λ_i33 to be at most 10⁻⁴–10⁻³, but these bounds can be evaded by fine-tuning other parameters.
• Two-loop contributions to neutrino masses, though suppressed, can impose stronger constraints than one-loop diagrams due to different parameter dependencies, leading to bounds of a few percent on λ′_i33 and λ_i33.
• The coupling A′_i33 is constrained to be at most of order 10 GeV to avoid excessive neutrino masses.
• Slepton production cross sections at the LHC remain non-negligible even with these constraints, particularly for λ′_i33 at the percent level, though significantly smaller than for a charged Higgs of equal mass.
• Charged sleptons with masses close to the charged Higgs can mimic its decay signatures (e.g., τν), complicating direct searches unless mass splitting is large.
• Sneutrino production via gluon fusion and decay into γγ remain viable but require detailed study, as their distinguishability from Higgs bosons is not yet established under current constraints.