H(SUSY)->tau+tau->hadron+hadron channel, its advantages and potential instrumental drawbacks

TL;DR

This study evaluates the purely hadronic $ au$ decay channel for $A/H o au au o h^{+}h^{-}+X$ in CMS, focusing on high $m_A$ where triggering on QCD jets is feasible. Using fast CMS simulations, tau jets are identified via tracker-based isolation, and background rejection is enhanced with missing transverse energy cuts and azimuthal correlations, enabling mass reconstruction of the Higgs with improved resolution. The results indicate that this channel offers the best mass reach and resolution among $ au au$ final states for heavy Higgs masses, with QCD background becoming subdominant to irreducible backgrounds after cuts. The work highlights trigger requirements, potential calorimetric/impact-parameter tau tagging improvements, and the importance of forward calorimetry, suggesting substantial discovery potential in the MSSM parameter space, especially for $m_A$ up to ~1 TeV. Further detailed studies are needed to confirm these preliminary findings and to optimize performance at higher luminosities.

Abstract

We present a first study of the channel H, A -> tau+tau -> h+ + h- + X in CMS at high m(A) values where no triggering difficulties are expected with QCD jets. At present the tau selection is based solely on the presence of a hard isolated track in the "tau" jet, but further refinements based on calorimeter collimation or impact parameter selections are obviously possible. The main irreducible background in these conditions is due to QCD jets with hard fragmentations. A large reduction of this background and improvement in the expected signal to background ratio is provided by Etmiss cuts. The expected high-mass reach in the m(A) tan(beta) parameter space for 3 x 10**4pb**-1 is shown. This H -> tau+tau channel provides the highest mass reach and the best mass resolution when compared to tau,tau -> lepton+hadron + Xand tau,tau -> electton + muon + X final states. To the extent that with further calorimetric and impact parameter based selection criteria the QCD background can be kept under control, i.e. below the irreducible Z,gamma* -> tau+tau background, we should strive to have a first level trigger allowing to explore the mass range down to ~ 150 - 200 GeV.

Figures (10)

• Figure 1: a) Distribution of the visible transverse energy of the $\tau$ jet for $A,H$$\;\rightarrow$$~\tau\tau$ at $m_A$=300 GeV (solid histogram) and $m_A$=500 GeV (dashed histogram). b) The same for $A,H$$\;\rightarrow$$~\tau\tau$ at $m_A$=800 GeV. c) Distribution of the transverse energy of the $\tau$ canditate (two hardest jets in the event) in the QCD jet events generated with $p_t^{q,g}>$60 GeV.
• Figure 2: a) Distribution of the transverse momentum of the isolated track in the jet with $E_t >$ 60 GeV for $A,H$$\;\rightarrow$$~\tau\tau$ at $m_A$=300 GeV (solid histogram), $m_A$=500 GeV (dashed histogram) and $m_A$=800 GeV (dotted histogram). b) The same for $Z, \gamma^*$$\;\rightarrow$$~\tau\tau$ with $m_{\tau\tau}>$130 GeV, c) The same for QCD 2-jet events
• Figure 3: Rejection factor for QCD jets as a function of $E_t^{jet}$. $\tau$ selection is performed in the tracker by requiring an isolated track with $p_t >$ 40 GeV within $\Delta R<$ 0.1 from the calorimeter jet axis. The isolation with a $p_t$ threshold of 1 GeV is extented to a larger cone of $\Delta R<$ 0.4.
• Figure 4: a) Distribution of the missing transverse energy for $A,H$$\;\rightarrow$$~\tau\tau$ at $m_A$=300 GeV and $tan\beta$=15 (solid histogram), $m_A$=500 GeV and $tan\beta$=20 (dashed histogram) and $m_A$=800 GeV and $tan\beta$=45(dotted histogram). The detector response is simulated with CMSJET. No pile-up is included. b) The same for QCD jet events in the full $\eta$ range and for the central calorimeters only.
• Figure 5: Distribution of the $\Delta\phi$ angle in the transverse plane between the two $\tau$ jets for $A,H$$\;\rightarrow$$~\tau\tau$ at $m_A$=300 GeV and $tan\beta$=20 (a), $m_A$=500 GeV and $tan\beta$=25 (b), $m_A$=800 GeV and $tan\beta$=45 (c), $Z, \gamma^*$$\;\rightarrow$$~\tau\tau$ with $m_{\tau\tau}>$130 GeV (d), $t\overline{t}$ with $W$$\;\rightarrow$$~\tau\nu$ (e) and QCD jet events (f).