Dortmund 2021 – scientific programme
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T: Fachverband Teilchenphysik
T 36: Search for Supersymmetry II
T 36.2: Talk
Tuesday, March 16, 2021, 16:15–16:30, Tk
Search for compressed mass-spectrum long-lived particles using short disappearing tracks with the ATLAS experiment — •Paul Gessinger and Stefan Tapprogge — Johannes Gutenberg-Universität Mainz
In certain Supersymmetry scenarios, the lightest neutralino χ10 and charginos χ1± can become nearly degenerate in mass. At mass splittings as low as Δ m( χ1±, χ10)≈100 MeV, the chargino obtains lifetimes of O(1 ns), which allows it to reach sensitive parts of the ATLAS experiment, before decaying, mostly to a neutralino leaving the detector without interacting, and a low momentum charged pion that is difficult to detect. This causes the chargino track to disappear.
The tracking systems and reconstruction algorithms of the ATLAS detector are designed to efficiently detect and reconstruct charged particles crossing all silicon sensor layers. Using specialized reconstruction techniques, it is possible to reconstruct short tracklets, which arise only from hits in the silicon Pixel detector. Previous ATLAS analyses used tracklets consisting of at least 4 Pixel hits and no hits in the silicon strip detector as disappearing track signatures to search for the aforementioned scenarios in LHC pp-collisions at 13 TeV.
This talk presents first results from the inclusion of short tracklets with only 3 hits. The analysis carried out in the context of a pure-higgsino signal scenario, featuring very short lifetimes. Background characteristics of this new tracklet type are evaluated, and signal efficiency is discussed. Expected sensitivity in the form of upper signal strength limits and mass exclusion limits is shown.