Mass reconstruction with M 2 under constraint in semi-invisible production at a hadron collider

We investigate the solvability of the event kinematics in missing energy events at hadron colliders, as a function of the particle mass ansatz. To be specific, we reconstruct the neutrino momenta in dilepton tt-like events, without assuming any prior knowledge of the mass spectrum. We identify a class of events, which we call extreme events, with the property that the kinematic boundary of their allowed region in mass parameter space

Section: Introductionmentioning

confidence: 99%

Kinematic focus point method for particle mass measurements in missing energy events

Kim

Matchev

Shyamsundar

2019

“…1 contained an additional two-body decay to a visible particle, just 5 events are sufficient for solving the event kinematics [22,27]. 3 Transversality is not strictly necessary, in fact it may even be beneficial to work with 3 + 1-dimensional variants of those variables [36][37][38][39][40][41][42][43][44][45][46][47].…”

Section: Introductionmentioning

confidence: 99%

Detecting kinematic boundary surfaces in phase space: particle mass measurements in SUSY-like events

Debnath

Gainer

Kılıç

et al. 2017

We critically examine the classic endpoint method for particle mass determination, focusing on difficult corners of parameter space, where some of the measurements are not independent, while others are adversely affected by the experimental resolution. In such scenarios, mass differences can be measured relatively well, but the overall mass scale remains poorly constrained. Using the example of the standard SUSY decay chaiñ q →χ 0 2 →˜ →χ 0 1 , we demonstrate that sensitivity to the remaining mass scale parameter can be recovered by measuring the two-dimensional kinematical boundary in the relevant three-dimensional phase space of invariant masses squared. We develop an algorithm for detecting this boundary, which uses the geometric properties of the Voronoi tessellation of the data, and in particular, the relative standard deviation (RSD) of the volumes of the neighbors for each Voronoi cell in the tessellation. We propose a new observable,Σ, which is the average RSD per unit area, calculated over the hypothesized boundary. We show that the location of theΣ maximum correlates very well with the true values of the new particle masses. Our approach represents the natural extension of the one-dimensional kinematic endpoint method to the relevant three dimensions of invariant mass phase space.

“…1(d) and 1(e). The latter is known as the "antler" topology [81] and has been previously discussed in the context of both hadron colliders [12,[81][82][83][84][85][86][87][88][89][90] and lepton colliders [91,92]. At the same time, the diagram of Fig.…”

Section: Two Decay Chains Each With One Two-body Decaymentioning

confidence: 93%

Singularity variables for missing energy event kinematics

Matchev

Shyamsundar

2020

We discuss singularity variables which are properly suited for analyzing the kinematics of events with missing transverse energy at the LHC. We consider six of the simplest event topologies encountered in studies of leptonic W -bosons and top quarks, as well as in SUSY-like searches for new physics with dark matter particles. In each case, we illustrate the general prescription for finding the relevant singularity variable, which in turn helps delineate the visible parameter subspace on which the singularities are located. Our results can be used in two different ways -first, as a guide for targeting the signal-rich regions of parameter space during the stage of discovery, and second, as a sensitive focus point method for measuring the particle mass spectrum after the initial discovery. 4 The only exception being an invisibly decaying Z-boson, or a leptonically decaying W -boson where the lepton is lost [26].5 For reviews of the large variety of mass measurement methods proposed for SUSY-like events with MET, see [27,28] and references therein.