A General Method for Model-Independent Measurements of Particle Spins, Couplings and Mixing Angles in Cascade Decays with Missing Energy at Hadron Colliders

Abstract

We outline a general strategy for measuring spins, couplings and mixing angles in the case of a heavy partner decay chain terminating in an invisible particle. We consider the common example of a new scalar or fermion D decaying sequentially to other new particles C, B and A by emitting a quark jet j and two leptons ln and lf. We derive analytic formulas for the dilepton {ln,lf} and the two jet-lepton ({j,ln} and {j,lf}) invariant mass distributions for most general couplings and mixing angles of the new partners. We then consider various spin assignments for the particles A, B, C and D, and derive the relevant functional basis for the invariant mass distributions which contains the intrinsic spin information and does not depend on the couplings and mixing angles. We propose a new method for determining the spins of the new partners, using the three experimentally observable distributions {l+,l-}, {j,l+}+{j,l-} and {j,l+}-{j,l-}. We show that the former two only depend on a single model-dependent parameter alpha, while the latter may depend on two other parameters beta and gamma. By fitting these distributions to our set of basis functions, we are able to do a pure measurement of the spins per se. Our method is also applicable at a pp-bar collider such as the Tevatron, for which the previously proposed lepton charge asymmetry is identically zero and does not contain any spin information. In the process of determining the spins, we also obtain an independent measurement of the parameters alpha, beta and gamma, which represent certain combinations of the couplings and the mixing angles of the heavy partners A, B, C and D.

arXiv comment67 pages, 29 figures, typeset in JHEP style

Cited by in corpus (47)

• Using Subsystem MT2 for Complete Mass Determinations in Decay Chains with Missing Energy at Hadron Colliders
• The Hunt for New Physics at the Large Hadron Collider
• Physics searches at the LHC
• Higgs look-alikes at the LHC
• Dark Matter Particle Spectroscopy at the LHC: Generalizing MT2 to Asymmetric Event Topologies
• A Review of the Mass Measurement Techniques proposed for the Large Hadron Collider
• M_T2-assisted on-shell reconstruction of missing momenta and its application to spin measurement at the LHC
• The 750 GeV Diphoton Excess May Not Imply a 750 GeV Resonance
• \sqrt{s}_min: a global inclusive variable for determining the mass scale of new physics in events with missing energy at hadron colliders
• A model independent spin analysis of fundamental particles using azimuthal asymmetries
• Using kinematic boundary lines for particle mass measurements and disambiguation in SUSY-like events with missing energy
• Precise reconstruction of sparticle masses without ambiguities
• Minimal Universal Extra Dimensions in CalcHEP/CompHEP
• 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
• Shedding Light on the Dark Sector with Direct WIMP Production
• Prospects for top-prime quark discovery at the Tevatron
• The Footprint of F-theory at the LHC
• Probing resonance decays to two visible and multiple invisible particles
• Using M_T2 to Distinguish Dark Matter Stabilization Symmetries
• LHC Collider Phenomenology of Minimal Universal Extra Dimensions
• Exploring Theory Space with Monte Carlo Reweighting
• Search for Higgs bosons of the Universal Extra Dimensions at the Large Hadron Collider
• OPTIMASS: A Package for the Minimization of Kinematic Mass Functions with Constraints
• Early spin determination at the LHC?
• Determination of the CMSSM Parameters using Neural Networks
• Missing Momentum Reconstruction and Spin Measurements at Hadron Colliders
• Spin effects in the antler event topology at hadron colliders
• Distinguishing spins at the LHC using bound state signals
• Spin Determination via Third Generation Cascade Decays
• Measuring Invisible Particle Masses Using a Single Short Decay Chain
• Distinguishing spins in decay chains with photons at the Large Hadron Collider
• Boost-invariant Leptonic Observables and Reconstruction of Parent Particle Mass
• Probing Supersymmetry With Third-Generation Cascade Decays
• Singularity Variables for Missing Energy Event Kinematics
• Characterizing dark matter at the LHC in Drell-Yan events
• Spin Discrimination in Three-Body Decays
• Two jets and missing $E_T$ signature to determine the spins of the new particles
• Model Discrimination at the LHC: a Case Study
• Measuring Masses in Semi-Invisible Final States at Electron-Positron Colliders
• Mitigation of the LHC Inverse Problem
• The impossibility of heavy neutrino dark matter in the Littlest Higgs Model with T-parity: constraints from direct search
• A New Method for the Spin Determination of Dark Matter
• General analysis of decay chains with three-body decays involving missing energy
• Spin and Chirality Effects in Antler-Topology Processes at High Energy $e^{+}{e}^{-}$ Colliders
• How to prove that the LHC did not discover dark matter
• Momentum asymmetries as CP violating observables
• Measuring the mass, width, and couplings of semi-invisible resonances with the Matrix Element Method