Excessive Higgs pair production with little MET from squarks and gluinos in the NMSSM

Ulrich Ellwanger,Ana M Teixeira

doi:10.1007/jhep04(2015)172

Abstract

In the presence of a light singlino-like LSP in the NMSSM, the missing transverse energy - MET - signature of squark/gluino production can be considerably reduced. Instead, a pair of Higgs bosons is produced in each event. We propose benchmark points for such scenarios, which differ in the squark and gluino masses, and in their decay cascades. Events for these points are simulated for the run II of the LHC at 13 TeV centre of mass energy. After cuts on the transverse momenta of at least four jets, and requiring two tau-leptons from one Higgs decay, we find that the invariant mass of two b-jets from the other Higgs decay shows clear peaks above the background. Despite the reduced MET, this search strategy allows to see signals for sufficiently large integrated luminosities, depending on the squark/gluino masses.

Highlights

A possible Standard Model particle X is the 125 GeV Higgs boson, additional non-SM-like Higgs bosons could play that role
The role of the “true” LSP can be played by a light gravitino [9, 11], so-called photini [12], or the singlino of the NMSSM [14]
As described in the Introduction and discussed in more detail in [14], a loss of ETmiss in sparticle decay cascades can occur in the NMSSM if a dominantly singlino-like LSP is light, the mass of the typically mostly bino-like NLSP MNLSP is somewhat above the sum of a Higgs and LSP masses MNLSP MH + MLSP, and practically all sparticle decay cascades terminate by a last step NLSP → H + LSP. (Decays NLSP → Z + LSP occur only if the NLSP has a higgsino component, i.e. if the effective μ parameter μeff of the NMSSM [15] is relatively small, which we do not assume here for simplicity.)

Summary

Scenarios with little MET in the NMSSM

As described in the Introduction and discussed in more detail in [14], a loss of ETmiss (associated to the LSP) in sparticle decay cascades can occur in the NMSSM if a dominantly singlino-like LSP is light, the mass of the typically mostly bino-like NLSP MNLSP is somewhat above the sum of a Higgs and LSP masses MNLSP MH + MLSP, and practically all sparticle decay cascades terminate by a last step NLSP → H + LSP. (Decays NLSP → Z + LSP occur only if the NLSP has a higgsino component, i.e. if the effective μ parameter μeff of the NMSSM [15] is relatively small, which we do not assume here for simplicity.). The benchmark points considered here include scenarios where squarks decay via gluinos, leading to more jets in the final state but with reduced transverse momenta of the (s)particles involved in the last decay step. Instead of varying the stop/sbottom masses, we choose a sufficiently large value, Mt, ̃b = 750 GeV to comply with current LHC limits, but we neglect contributions from stop/sbottom pair production to the signals. (Muons inside such jets are added to the invariant mass of the system.) This simple approach works for all benchmark points; even the ones with large average transverse momenta of Higgs bosons lead to sufficiently many events with less boosted Higgses whose mass can be reconstructed this way. All SM backgrounds get strongly reduced by the combined cuts on 4 hard jets (see above), two hadronically decaying τ ’s, and 2 b-quarks with an invariant mass in the signal region. The sum of all other background contributions to the signal region was found to be below 10−3 fb

Signals for benchmark points

Findings

Summary and conclusions