title: Opening Up the Compressed Region of Top Squark Searches at 13 TeV LHC.
abstract: Light top superpartners play a key role in stabilizing the electroweak scale in supersymmetric theories. For R-parity conserved supersymmetric models, traditional searches are not sensitive to the compressed regions. In this Letter, we propose a new method targeting this region, with top squark and neutralino mass splitting ranging from m_{t[over ˜]}-m_{χ}≳m_{t} to about 20 GeV. In particular, we focus on the signal process in which a pair of top squarks are produced in association with a hard jet, and we define a new observable R_{M} whose distribution has a peak in this compressed region. The position of the peak is closely correlated with m_{t[over ˜]}. We show that for the 13 TeV LHC with a luminosity of 3000  fb^{-1}, this analysis can extend the reach of the top squark in the compressed region to m_{t[over ˜]} around 800 GeV.
authors.affiliation: Walter Burke Institute for Theoretical Physics, California Institute of Technology, Pasadena, California 91125, USA.
authors.forename: Haipeng
authors.initials: H
authors.lastname: An
authors.affiliation: Enrico Fermi Institute and Department of Physics, University of Chicago, 5620 South Ellis Avenue, Chicago, Illinois 60637, USA.|Kavli Institute for Cosmological Physics, University of Chicago, 933 East 56th Street, Chicago, Illinois 60637, USA.
authors.forename: Lian-Tao
authors.initials: LT
authors.lastname: Wang