[Paper Review] Comparison of Black Hole Generators for the LHC

D. M. Gingrich|ArXiv.org|Oct 17, 2006

Particle physics theoretical and experimental studies20 references3 citations

TL;DR

This paper compares two Monte Carlo event generators, CHARYBDIS and CATFISH, for simulating black hole production and decay at the LHC in models with extra dimensions. It evaluates their treatment of black hole cross sections, inelastic production, graviton emission, and decay dynamics, concluding that CATFISH offers more comprehensive features—particularly inelastic models and graviton emission—making it better suited for modern LHC studies despite CHARYBDIS's wider adoption.

ABSTRACT

We compare Monte Carlo event generators dedicated to simulating the production and decay of extra-dimensional black holes at the Large Hadron Collider.

Motivation & Objective

• To evaluate and compare the capabilities of two major Monte Carlo event generators, CHARYBDIS and CATFISH, for simulating black hole production and decay at the LHC.
• To identify key differences in their treatment of black hole production cross sections, inelastic effects, and decay dynamics in higher-dimensional models.
• To assess the impact of these differences on simulated observables, particularly missing energy and final-state particle spectra.
• To provide guidance on generator selection for future LHC black hole studies based on physical completeness and technical features.
• To recommend improvements, such as implementing inelastic models and graviton emission in CHARYBDIS, based on CATFISH's more advanced features.

Proposed method

• The comparison is based on analysis of CHARYBDIS v1.003 (24 August 2006) and CATFISH v1.1 (19 October 2006), using documentation and source code for CHARYBDIS and documentation alone for CATFISH.
• Both generators use the black disk approximation for the parton-level cross section, dependent on the Schwarzschild horizon radius and Planck scale in higher dimensions.
• The Les Houches Accord is used as the standard interface for both generators, enabling integration with PYTHIA or HERWIG for parton showering and hadronization.
• CATFISH includes two inelastic gravitational models (Yoshino-Nambu and Yoshino-Rychkov) based on trapped-surface approaches, while CHARYBDIS assumes elastic black hole formation.
• Decay modeling focuses on the Hawking evaporation phase, with both generators treating particles as massless and assigning decay probabilities based on degrees of freedom.
• CATFISH allows for N-body phase-space decay (N = 2 to 18) and includes graviton emission with exact field emissivities, while CHARYBDIS ignores gravitons and limits N to 2–5.

Experimental results

Research questions

• RQ1 How do CHARYBDIS and CATFISH differ in their treatment of black hole production cross sections and Planck scale definitions?
• RQ2 What are the implications of inelastic black hole formation models in CATFISH compared to the elastic assumption in CHARYBDIS?
• RQ3 How do the inclusion of graviton emission and different decay models affect missing energy signatures in simulated events?
• RQ4 To what extent do differences in N-body decay parameters and remnant formation affect final-state distributions?
• RQ5 Which generator provides a more complete and physically consistent simulation of black hole production and decay for LHC phenomenology?

Key findings

• CATFISH supports a wider range of spacetime dimensions (7–11) compared to CHARYBDIS (6–11), and includes two inelastic gravitational models based on trapped-surface approaches.
• CATFISH accounts for energy loss in inelastic collisions by assigning missing energy to beam remnants and allows for graviton emission into the bulk, enhancing missing energy signatures.
• CHARYBDIS does not include gravitons, while CATFISH includes them with exact field emissivities, which become increasingly important at high dimensions.
• CATFISH allows for a variable N-body decay (N = 2 to 18) and supports a black hole remnant model with charge options, whereas CHARYBDIS limits N to 2–5 and offers a boiling remnant model below the Planck scale.
• The Planck scale definition differs: CHARYBDIS offers three definitions (including the Dimopoulos-Landsberg definition), while CATFISH uses only one, matching CHARYBDIS's default (MSSDEF=2).
• The authors recommend using CATFISH’s 'optimal cut' model for inelastic production and suggest that CHARYBDIS should be updated to include similar features for consistency with recent theoretical developments.