# Prospects for the Discovery of the SM Higgs Boson using the H->γγ decay

**This page contains approved plots and results in the order as they appear in the CSC note. Only the CSC note contains all the relevant information and should thus be consulted if one of the plots is used.**

**Figure 1:** Efficiency of single-track and double-track conversion reconstruction as a function of the conversion radius.

**Figure 2:** p_{T} /E_{T} ratio for conversions where both tracks were reconstructed in different event samples.

**Figure 3:** Difference between the reconstructed primary vertex position and the true position obtained from calorimetric pointing and conversion track information (when available) without/with the reconstructed primary vertex (left/right plot), for events without pile-up (black plots) and with pile-up evaluated for 1×10^{33} and 2×10^{33} cm^{-2} s^{-1} (red, green plots). The narrow peak on top of the broader one is due to events in which at least one photon has a reconstructed conversion vertex. In the right plots, the non-Gaussian shape is due to the overlap of barrel-barrel, barrel-endcap and endcap-endcap topologies, which have different resolutions.

**Figure 4:** Invariant mass distributions for photons pairs from Higgs boson decays with m

_{H} = 120

GeV after trigger and identification cuts; on the left the invariant mass distribution obtained using the nominal geometry simulation is reported while on the right plot the same invariant mass distribution is reported when additional dead material is included in the simulation. The shaded histograms correspond to events with at least one converted photon.

**Figure 5:** Diphoton candidates invariant mass distribution for γ j (left) and Drell-Yan e^{+} e^{-} (right) events after photon identification and analysis cuts with and without trigger selection.

**Figure 6:** Diphoton invariant mass spectrum after the application of cuts of the inclusive analysis. Results are presented in terms of the cross-sections in fb. The contribution from various signal and background processes are presented in stacked histograms (see text).

**Figure 7:** Diphoton invariant mass spectrum in fb obtained with the Higgs boson plus one jet analysis (see Section 5.2). The same procedure as in Fig. 6 in Section 5.1 is used to obtain the histograms in Fig. 7. The same codes for signal and backgrounds are used as in Fig. 6.

**Figure 8:** Diphoton invariant mass spectrum obtained with the Higgs boson plus two jet analysis (see Section 5.3).

**Figure 9:** Expected distribution of the invariant mass of the two photons for the signals and main backgrounds after applying the analysis cuts for events having one lepton reconstructed in the final state. Due to a lack of MC statistics for the diphoton and the W γ backgrounds, their expected distribution is approximated by showing an average of the number of events passing the analysis cuts in the m_{γγ} mass range shown.

**Figure 10:** Expected distribution of the invariant mass of the two photons for the signals and main backgrounds after applying all the diphoton and E_{T}^{miss} analysis cuts. Due to a lack of statistics for the diphoton and the Wγ backgrounds, their expected distribution is approximated by showing an average of the number of events passing the analysis cuts in the m_{γγ} mass range shown.

**Figure 12:** Regions of photon pseudorapidities with different invariant mass resolutions for unconverted photons (left) and at least one converted photon (right). The text per box denotes the region number, the percentage of events occurring in the region and the RMS of the diphoton invariant mass for H->γγ events. To simplify the likelihood model, events with photons in regions (1) and (8) are merged and represent category 'good' (signal fraction 24%), events in regions (2), (3), (4) and (6) correspond to category 'medium' (60%), and regions (5) and (7) are 'bad' (15%).

**Figure 13:** Expected signal significance for a Higgs boson using the H->γγ decay for 10 fb^{-1} of inte grated luminosity as a function of the mass. The solid circles correspond to the sensitivity of the inclusive analysis reported in Section 5.1 using event counting. The open circles display the event counting significance when the Higgs boson plus jet analyses (see Sections 5.2 and 5.3) are included. The solid triangles linked with solid and dashed lines correspond to the sensitivity of the inclusive analysis by means of one dimensional fits, with a fixed and floating Higgs boson mass, respectively. The solid squares linked with solid and dashed lines correspond to the maximum sensitivity that can be attained with a combined analysis (see text and Table 19).

**Major updates**:

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WolfgangMader - 27 Jan 2009

Responsible: WolfgangMader

Last reviewed by: **Never reviewed**