Investigating light NMSSM pseudoscalar states with boosted ditau tagging

We study a class of realizations of the Next-to-Minimal Supersymmetric Standard Model that is motivated by dark matter and Higgs data, and in which the lightest pseudoscalar Higgs boson mass is smaller than twice the bottom quark mass and greater than twice the tau lepton mass. In such scenarios, the lightest pseudoscalar Higgs boson can be copiously produced at the LHC from the decay of heavier superpartners and will dominantly further decay into a pair of tau leptons that is generally boosted. We make use of a boosted object tagging technique designed to tag such a ditau jet, and estimate the sensitivity of the LHC to the considered supersymmetric scenarios with 20 to 50~fb$^{-1}$ of proton-proton collisions at a center-of-mass energy of 13~TeV.


Outline
Light pseudoscalar in NMSSM Di-τ jet tagging Benchmark Conclusion

NMSSM parameter space
Scanning the NMSSM parameter space in the following range: H 2 is identified as the H SM , consistent with LHC observation We focus on the scenarios in which the lightest pseudoscalar state A 1 is mostly singlet-like and Without miracle cancellation in (M 2 P ) 33 , the mass of the lightest singlet-like scalar state in the absence of a too large mixing will be smaller than 125 GeV.
Small λ and κ values are generally favored.
An important A 1 production rate can be achieved in the region where the spectrum is compressed. Branching Ratio    Strategy of di-τ jet tagging BDT with following variables: N track : Number of tracks in the τ (di-τ ) jet candidate.
fcent: Fraction of energy deposited in the ∆R < 0.1 with respect to energy deposited in the ∆R < 0.2 around the τ (di-τ ) jet candidate.
f track : The transverse momentum of the highest-p T track in ∆R < 0.2 around the τ (di-τ ) jet candidate divided by the p T of the jet.
R track : p t weighted distance of all tracks to the τ (di-τ ) jet candidate direction.
∆R Max : The maximum ∆R between a track in the ∆R < 0.2 around the τ (di-τ ) jet candidate and the jet direction.
Track mass (m track ): Invariant mass calculated from the sum of the four-momentum of all tracks.
p T /m: Ratio between transverse momentum and mass of the τ (di-τ ) jet candidate.
Eem/E had : The energy of the τ (di-τ ) jet candidate deposit in electromagnetic calorimeter divided by that in hadronic calorimeter.
Light pseudoscalar in NMSSM Di-τ jet tagging Benchmark Conclusion Strategy of di-τ jet tagging τ /di-τ jet has more centered energy distribuion. f cent : Fraction of energy deposited in the ∆R < 0.1 with respect to energy deposited in the ∆R < 0.2 around the τ (di-τ ) jet candidate. Di-τ tagging with BDT method Jets issued from the fragmentation of light quarks are always harder to distinguish. The corresponding rejection power is increased when the jet energy is higher.

Kinematic properties
For the benchmark point, E(A 1 ) 50 GeV is in general much larger than the A 1 mass, the pseudoscalar decay products (two tau leptons) turn out to be highly collimated.

Kinematic properties
The bulk of the signal events features at most two jets, while the leading jet is in general the boosted ditau object (in 70% of the cases for the benchmark point). The BDT discrimination ∆φ(l, / p T ): The BDT discrimination An signal efficiency of about one percent can be obtained together with a background rejection rate of 10 4 ( 10 5 ) when the ditau tagging is ignored (included). A 3σ hint for the class of NMSSM scenarios considered in this work could be observed at the early stage of the LHC Run-II, while a 5σ discovery could be expected with an integrated luminosity of at least 50 fb −1 .
The light higgsinos can have large production rate at LHC, which in turn means large production rate of A 1 .
The background rejection can be improved by more than one order of magnitude with the help of di-τ tagging. 3σ hint for the signal is expected within the first 13 TeV data, and that a 5σ discovery could be envisaged for a luminosity of more than about 50 fb −1 .