Abstract
The LHC searches for light compressed top squarks have resulted in considerable bounds in the case where the top squark decays to a neutralino and a charm quark. However, in the case where the top squark decays to a neutralino, a bottom quark, and two fermions via an off-shell W boson, there is currently a significant unconstrained region in the top-squark-neutralino mass plane, still allowing for top squark masses in the range 90-140 GeV. In this Letter we propose a new monojetlike search for light top squarks, optimized for the four-body decay mode, in which at least one b-tagged jet is required. We show that, by using the existing 8 TeV LHC data set, such a search would cover the entire unconstrained region. Moreover, in the process of validating our tools against an ATLAS monojet search, we show that the existing limit can be extended to exclude also top squark masses below 100 GeV.
Highlights
M1 (ATLAS [42]) M1 þ b tag tt780 Æ 73 307 Æ 57 Zð→ ννÞ17400 Æ 720 261 Æ 22 Wð→ lνÞ14100 Æ 337 144 Æ 7 Dibosons 650 Æ 99 55 Æ 17 Others 565 Æ 301 ÁÁÁ Total
In this Letter we show that, by augmenting an existing monojet search with a b-tag requirement, this unconstrained region could already be covered completely by the existing 8 TeV Large Hadron Collider (LHC) data set
Proposed top squark four-body search.—The search we propose is a simple extension of the ATLAS inclusive monojet search [42] where, in addition, we require the presence of at least one b-tagged jet
Summary
Dipartimento di Fisica e Astronomia, Università di Padova, and INFN Sezione di Padova, Via Marzolo 8, I-35131 Padova, Italy (Received 19 February 2015; published 19 May 2015). Taking a simplified model approach, a key strategy to test R-parity conserving SUSY is to consider only the lightest top squark mass eigenstate ~t1, decaying to the lightest superpartner, the neutralino χ~01, and taking all other superpartners to be sufficiently heavy and effectively decoupled. In the case where the mass difference between the top squark and the neutralino is larger than the top mass, Δm 1⁄4 m~t1 − mχ~01 > mt, each of the pair produced top squarks decays in two-body form via an on-shell top quark, ~t1 → tχ~01 In this case, for neutralino masses below around 250 GeV, the current LHC limits exclude top squark masses below 600–750 GeV [41,50], while for larger neutralino masses there are no bounds.
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