May 17th -Thursday- 12:10

"Alternative search strategies for supersymmetry at the LHC"

Ernesto Arganda

(Instituto de Física de La Plata, IFLP-CONICET/UNLP, Buenos Aires, Argentina)

In this seminar, alternative search strategies at the LHC for heavy neutral Higgs bosons and supersymmetric tau-lepton partners (staus), within the context of the MSSM, are presented. In the first part, we will discuss a search strategy for heavy Higgs bosons decaying invisibly at the LHC, focusing on the pair production of a heavy scalar $H$ together with a pseudoscalar $A$, through the production mode $q \bar q \to Z^\ast \to HA$. We identify as the most promising signal the final state made up of $4b + E_T^\text{miss}$, coming from the heavy scalar decay mode $H \to hh \to b \bar b b \bar b$, with $h$ being the discovered SM-like Higgs boson with $m_h=125$ GeV, together with the invisible channel of the pseudoscalar. This search strategy, for a LHC center-of-mass energy of $\sqrt{s} =$ 14 TeV, allows us to obtain statistical significances of the signal over the SM backgrounds with values up to $\sim$ 1.6$\sigma$ and $\sim$ 3$\sigma$, for total integrated luminosities of 300 fb$^{-1}$ and 1000 fb$^{-1}$, respectively. In a second part of the seminar we will develop another search strategy for the discovery of staus at the LHC. The search profits from the large s-channel $b$-quark annihilation production of the heavy Higgs bosons $H/A$ which can be attained in regions of $\tan\beta\gg 1$ that avoid the stringent $H/A\to \tau\bar{\tau}$ searches via decays into stau pairs. We also focus on regions where the staus branching ratios are dominated by the decays into a tau lepton and the lightest neutralino. Thus the experimental signature consists of final states made up of two tau leptons plus large missing transverse energy. We take advantage of the large stau-pair production cross sections via heavy Higgs boson decays, which are between one or two orders or magnitude larger than the usual electroweak cross sections productions for staus. Basic cuts imposed through a sequential cut-optimization algorithm allow us to obtain significances of the signal over the SM backgrounds at the discovery level (5 standard deviations) in the next LHC run with a center-of-mass energy of 14 TeV and a total integrated luminosity of only 100 fb$^{-1}$.

Facultad de Ciencias

Seminario de Física Teórica

Universidad de Zaragoza