---++!! Abstract

This document describes the performance of the CMS Level-1 calorimeter trigger for τ leptons using 11.1 fb^-1 of 2018.

Details of the Level-1 trigger algorithms can be found in <a href="https://cds.cern.ch/record/2018400/?ln=es" target="_blank">CMS-DP-2015-009</a>.

The previous Level-1 τ performance report can be found in <a href="https://cds.cern.ch/record/2305547?ln=es" target="_blank">CMS-DP-2018-006</a>.

---++ DPS note

The DPS note ID is CMS DPidPLACEHOLDER. The link to the DPS note in CDS can be found here LINK PLACEHOLDER.

---++ Performance Plots

---+++ Efficiency of Level-1 τ seeds

* The Level-1 trigger efficiency is evaluated for hadronically-decaying τ’s used to seed the di-τ High Level Trigger.
* The efficiency is computed per single-τ-leg through the tag-and-probe method, as a function of the offline-reconstructed τ transverse momentum.
* Hadronically-decaying τ’s from the Z→τ_μ τ_h process are selected in events that fired single μ High Level Trigger and fulfill the baseline H→ττ requirements of well identified and isolated μτ_h pairs, as well as m(E_T^miss,μ) < 30 GeV and 40 GeV < m_vis(τ,μ) < 80 GeV.
* An η restriction of |η| < 2.1 is applied to the τ_h Level-1 objects.
* Passing Level-1 τ’s probes must geometrically match selected offline τ’s.
* The results are based on 40.9 fb^-1 of 2017 data.
* In the following, p_T^τ,offline refers to the transverse momentum of the offline τ candidate.

| Inclusive seeds |||
| <p><img alt="efficiency_pT_inclusive.png" height="438" src="https://twiki.cern.ch/twiki/pub/Sandbox/L1TauPerformance2018/efficiency_pT_inclusive.png" title="efficiency_pT_inclusive.png" width="453" /></p> <p> PDF version</p> | <p><img alt="efficiency_pT_inclusive_120GeV.png" height="438" src="https://twiki.cern.ch/twiki/pub/Sandbox/L1TauPerformance2018/efficiency_pT_inclusive_120GeV.png" title="efficiency_pT_inclusive_120GeV.png" width="453" /></p> <p> PDF version</p> |
| Level-1 trigger efficiency of inclusive τ-seeds (i.e. without any requirement on the isolation at Level-1) as a function of the offline τ transverse momentum. | <p>Level-1 trigger efficiency of inclusive τ-seeds (i.e. without any requirement on the isolation at Level-1) as a function of the offline τ transverse momentum. The L1 τ E_T threshold here corresponds to the one used in the lowest single-τ unprescaled seed in 2017 (L1_SingleTau120er).</p> <p>For this efficiency estimate, the tag-and-probe offline selection method described before is used, except the m(E_T^miss,μ) and visible m(τ,μ) requirements are not applied. This approach is taken to increase the statistics available to the measurement. However, this leads to a τ sample dominated by jet →τ fakes.</p> |

| Isolated seeds |||
| <p><img alt="efficiency_pT_isolated.png" height="438" src="https://twiki.cern.ch/twiki/pub/Sandbox/L1TauPerformance2018/efficiency_pT_isolated.png" title="efficiency_pT_isolated.png" width="453" /></p> <p> PDF version</p> |
| Level-1 trigger efficiency of isolated τ-seeds (i.e. requiring the Level-1 τ candidate to pass a cut on its isolation transverse energy) as a function of the offline τ transverse momentum. |

-- CristinaMartinPerez - 2018-02-20

-- CristinaMartinPerez - 2018-06-27