On-shell constrained $M_2$ variables with applications to mass measurements and topology disambiguation

Abstract

We consider a class of on-shell constrained mass variables that are 3+1 dimensional generalizations of the Cambridge $M_{T2}$ variable and that automatically incorporate various assumptions about the underlying event topology. The presence of additional on-shell constraints causes their kinematic distributions to exhibit sharper endpoints than the usual $M_{T2}$ distribution. We study the mathematical properties of these new variables, e.g., the uniqueness of the solution selected by the minimization over the invisible particle 4-momenta. We then use this solution to reconstruct the masses of various particles along the decay chain. We propose several tests for validating the assumed event topology in missing energy events from new physics. The tests are able to determine: 1) whether the decays in the event are two-body or three-body, 2) if the decay is two-body, whether the intermediate resonances in the two decay chains are the same, and 3) the exact sequence in which the visible particles are emitted from each decay chain.

44pages, 17 figures. revised version, published in JHEP. Minor addition: a paragraph discussing the effect on the background at the end of section 5.1

References in corpus (18)

• Gluino Stransverse Mass
• Measuring superparticle masses at hadron collider using the transverse mass kink
• Using Subsystem MT2 for Complete Mass Determinations in Decay Chains with Missing Energy at Hadron Colliders
• Minimal Kinematic Constraints and MT2
• On measuring the masses of pair-produced semi-invisibly decaying particles at hadron colliders
• Accurate Mass Determinations in Decay Chains with Missing Energy
• A Review of the Mass Measurement Techniques proposed for the Large Hadron Collider
• Transverse Observables and Mass Determination at Hadron Colliders
• Mass Determination of New States at Hadron Colliders
• \sqrt{s}_min: a global inclusive variable for determining the mass scale of new physics in events with missing energy at hadron colliders
• Precise reconstruction of sparticle masses without ambiguities
• A Review of Spin Determination at the LHC
• RECO level \sqrt{s}_{min} and subsystem \sqrt{s}_{min}: improved global inclusive variables for measuring the new physics mass scale in missing energy events at hadron colliders
• A short comparison between m_T2 and m_CT
• A hybrid method for determining particle masses at the Large Hadron Collider with fully identified cascade decays
• A New Method for Resolving Combinatorial Ambiguities at Hadron Colliders
• Extracting the Dark Matter Mass from Single Stage Cascade Decays at the LHC
• Missing Momentum Reconstruction and Spin Measurements at Hadron Colliders

Cited by in corpus (34)

• Recursive Jigsaw Reconstruction: HEP event analysis in the presence of kinematic and combinatoric ambiguities
• Probing the Top-Higgs Yukawa CP Structure in dileptonic $t\bar{t}h$ with $M_2$-Assisted Reconstruction
• LHC Signals from Cascade Decays of Warped Vector Resonances
• Portraying Double Higgs at the Large Hadron Collider
• Probe Higgs boson pair production via the $3\ell 2j$ + missing $E_T$ mode
• Direct Higgs-top CP-phase measurement with $t\bar{t}h$ at the 14 TeV LHC and 100 TeV FCC
• New Physics in multi-Higgs boson final states
• Gluino reach and mass extraction at the LHC in radiatively-driven natural SUSY
• Improving the sensitivity of stop searches with on-shell constrained invariant mass variables
• OPTIMASS: A Package for the Minimization of Kinematic Mass Functions with Constraints
• Mass reconstruction with $M_2$ under constraint in semi-invisible production at a hadron collider
• Resolving Combinatorial Ambiguities in Dilepton $t\bar{t}$ Event Topologies with Constrained $M_2$ Variables
• Detecting kinematic boundary surfaces in phase space: particle mass measurements in SUSY-like events
• Testing Invisible Momentum Ansatze in Missing Energy Events at the LHC
• Constrained $\sqrt{{\hat{S}}_{min}}$ and reconstructing with semi-invisible production at hadron colliders
• Is the Machine Smarter than the Theorist: Deriving Formulas for Particle Kinematics with Symbolic Regression
• Identifying Phase Space Boundaries with Voronoi Tessellations
• Portraying Double Higgs at the Large Hadron Collider II
• Invisible dark gauge boson search in top decays using a kinematic method
• Singularity Variables for Missing Energy Event Kinematics
• Enhancing the discovery prospects for SUSY-like decays with a forgotten kinematic variable
• YAM2: Yet another library for the $M_2$ variables using sequential quadratic programming
• Multi-Dimensional Phase Space Methods for Mass Measurements and Decay Topology Determination
• Measuring Masses in Semi-Invisible Final States at Electron-Positron Colliders
• Resolving Combinatorial Ambiguities in Dilepton $t\bar{t}$ Event Topologies with Neural Networks
• Kinematic Focus Point Method for Particle Mass Measurements in Missing Energy Events
• Energy spectra of massive two-body decay products and mass measurement
• Dreaming Awake: Disentangling the Underlying Physics in Case of a SUSY-like Discovery at the LHC
• Identifying the production process of new physics at colliders; symmetric or asymmetric?
• A singular way to search for heavy resonances in missing energy events
• $M_{TN}$ is all you need: production of multiple semi-invisible resonances at hadron colliders
• DeeLeMa: Missing information search with Deep Learning for Mass estimation
• A new approach to semi-leptonic tags in $B$-meson semi-invisible decays
• Could $M_{T2}$ be a singularity variable?