Search for electroweakinos in compressed-spectrum scenarios with low-momentum isolated tracks in proton-proton collisions at $\sqrt{s}$ = 13 TeV

TL;DR

This paper searches for nearly mass-degenerate higgsino-like electroweakinos in proton-proton collisions at 13 TeV, using low-momentum isolated tracks and neural networks to distinguish signal from background, but finds no significant excess.

Contribution

It introduces a novel search strategy employing a parameterized neural network to identify soft, potentially displaced tracks from higgsino decays in compressed-spectrum scenarios.

Findings

Excluded higgsino models with mass splittings 0.28-1.15 GeV

Excluded chargino masses up to 185 GeV

Set constraints on natural supersymmetry scenarios

Abstract

A search for supersymmetric electroweakinos is performed using events with a low-momentum (soft) isolated track and large missing transverse momentum, targeting nearly mass-degenerate higgsino-like charginos and neutralinos. For mass splittings of 0.3$-$1 GeV, the chargino decays to the lightest neutralino and a low-momentum pion, which can produce a soft, potentially displaced track. A parameterized neural network separates signal from background using kinematic and impact parameter information. The analysis uses 138 fb$^{-1}$ of proton$-$proton collision data at a center-of-mass energy of 13 TeV recorded with the CMS detector. No significant excess above the standard model expectation is observed. At 95% confidence level, the considered higgsino model is excluded for mass splittings in the range 0.28$-$1.15 GeV and for chargino masses up to 185 GeV, setting stringent constraints on natural supersymmetry scenarios.