Jet Mass Calibration

Introduction

This page is a dedicated repository for the distributions and calibration factors derived for both the jet mass response and track-assisted jet mass response calibrations. It is part of ongoing work carried out by the Jet Substructure subgroup of JetEtMiss. The two jet mass response definitions currently being considered in the calibration framework are: 1. The standard definition of jet mass response, R = m_reco/m_truth of the jet; and 2. the track-assisted mass response, R_TA = (p_T,calo/p_T,track)*m_track.

Derivations and Samples

The JETM8_p2425 derivation is currently being used, with four different sample topologies being considered. In total, there is one background topology (JZXW, or QCD multijets) and three signal jet topologies: W' → W/Z-jets, Z' → t-jets, and Randall-Sundrum G → HH → b-jets.

Jet Collections

The calibration factors are extracts for separate jets collections. The large R-jets are obtained from the AntiKt10LCTopoTrimmedPtFrac5SmallR20 jet collected. The small R-jets are obtained from the AntiKt4EMTopo jet collected. As and when analysis groups require it, further R-jet calibrations from other jet collections can also be made available. For example, small-R jet calibrations from the AntiKt4LCTopo jet collections can made made available in the future.

Binning in pT_truth, m_truth and |η_det| is applied to the calibration plots, and, for 3-dimensional binning, the response is given as a function of both m_truth and pT_truth, for different |η_det| bins satisfying the acceptance region of the ATLAS detector. Studying the response behaviour as a function of truth variables give information on the closure achieved before and after calibration has been applied. Also presented here are response plots as a function of pT_reco. Rather than providing closure information, these distributions provide information of the response calibration uncertainty.

Jet Mass Calibration Schedule

Late 2015/early 2016: completion of small and large-R jet collections calibration, using mc15a and mc15b. Calibrations derived using both the standard jet mass response and track-assisted mass response approaches.

Recent JSS Talks

HCW2015_JetMassCalibration_v2.pdf

JMS.pdf

TA_Mass_Uncertainties.pdf

Large-R Jet Calibration (AntiKt10LCTopoTrimmedPtFrac5SmallR20)

Response Plots

The jet mass and track-assisted mass responses as a function of truth momentum, for different truth mass bins. Jet momentum and jet energy responses are included for completeness.

For tracked-assisted mass responses:

ResponseTA.zip

For calorimeter mass responses:

ResponseJMS.zip

Truth Summary Plots

Summary of the mass responses as a function of pT_truth and m_truth, and for different m_truth and |η_det| bins. Summary plots are given for both 2D and 3D binning, and for both the jet mass response and the track-assisted jet mass response. Finally, closure plots are also attached for the responses after jet mass calibration has been applied.

For track-assisted mass responses:

TruthSummaryTA.zip

For calorimeter mass responses:

TruthSummaryJMS.zip

Reco Summary Plots

Summary of the mass response as a function of pT_reco, for the track-assisted mass response definition. This study was conducted to understand the topological uncertainty on the track-assisted mass response. The background sample and three signal jet samples are considered, and the final track-assisted mass uncertainty distribution is also attached. This was a self-contained study, separate to the large-R jet mass calibration. It has been included here since it made direct use of the large-R jet jet collection.

For track-assisted mass response:

RecoSummaryTA.zip

Small-R Jet Calibration (AntiKt4EMTopo)

Calibration Factors

The calibration factors for small-R jets have also been derived, and are available in the latest tag of JetCalibTools. Calibration factors have been derived for both the calorimeter mass and track-assisted mass.

Further Information

For further information on the calibration studies, and background reader, the interested user should consult the two jet mass reconstruction and calibration notes currently available.

CONF Note

Internal Note