Validation of excited tau-lepton signal samples

This page describes basic steps made towards production of the Monte Carlo (MC) samples for excited tau-lepton signal. This analysis searches for excited tau-leptons in proton-proton collisions at a center-of-mass energy of 13 TeV.

Benchmark model

The excited lepton production by contact interaction described by four-fermion Lagrangian as introduced by U. Baur, M. Spira, and P. M. Zerwas (Phys.Rev. D42(1990) 815, Excited-quark and -lepton production at hadron colliders).

MC Generator

The MC generator of use is Pythia 8 with the version 8.243p and EvtGen (v.1.7.0) using the NNPDF23LO PDF set and the A14 underlying event tune. This Pythia 8 version includes correct mass suppression for excited fermion three-body decays F* -> F Fbar f, primarily for excited lepton decays with top-quarks in the final state (F = t).

Excited tau-lepton production

The single production of excited tau-leptons via four-fermion contact interaction (CI) is considered.

Strength of the SU(2), U(1) coupling, and SU(3) couplings are supposed to be unity (1.).

Excited tau-lepton decay

Generated excited tau-leptons decay via CI to a SM tau-lepton and a quark-antiquark pair.

Exclusive mode "tau* -> tau + b + bbar" might be added to the analysis later on.

Mass range and scan points

For the compositeness scale Lambda = 5 TeV, excited tau-lepton mass was assumed to lay in the range [250, 5000] GeV with a step 250 GeV.

For the compositeness scale Lambda = 7 TeV, excited tau-lepton mass was assumed to be one of the following values {1000, 3000, 5000, 5500, 6000, 6500, 7000} GeV.

Additionally, samples at m_tau* = Lambda for {1000, 2000, 3000, 4000} GeV were produced.

Cross section, BR, effective luminosity

Athena commands

EVNT containers were produced with Athena branch 21.6 intended purposefully for event generation:

asetup AthGeneration, 21.6.12,here

An example if the command is given below:

Generate_tf.py --ecmEnergy=13000 --maxEvents=200000 --firstEvent=1 --randomSeed=0897557 --localPath=/afs/cern.ch/work/k/kpetukho/ExcTau/Generators/MC15JobOptions --jobConfig=421111/mc.Py8_A14_NNPDF23LO_excited_tau_CI_mtau_250_lam5000.py --runNumber=08973427 --outputEVNTFile=CI_tau_250_5000_200000evt.pool.root > log_CI_1000_5000_50000evt.generate

EVNT files were converted into xAOD for an analysis at truth level with Athena release 21.2:

asetup 21.2.86.0,AthDerivation

To check performance limitations, several samples are going to be checked at RECO level (ATLFastIISimulation and AOD derivation is being performed).

An example of the command is given below:

Reco_tf.py --inputEVNTFile evnt.pool.root --outputDAODFile test.pool.root --reductionConf TRUTH3

Spreadsheet

MC production spreadsheet can be found at Google Docs.

Plots with kinematic distributions

DSIS to be set after MC request approval.

DSID	m_tau* [GeV]	Lambda [TeV]	N_events	BR	Cross section [pb]	Luminosity [inv. fb]	Job option	Supporting plots
	250	5000	200,000	0.0193439	1.85E-02	1.081081E+04	JO example on gitlab	Validation plots
	500	5000	200,000	0.066282	3.955E-02	5.05689E+03	JO example on gitlab	Validation plots
	750	5000	200,000	0.1378238	5.271E-02	5.352685E+02	JO example on gitlab
	1000	5000	50,000	0.217389	5.441E-02	9.189487E+02	JO example on gitlab	Validation plots
	1250	5000	50,000	0.2930013	4.812E-02	5.305278E+02	JO example on gitlab
	1500	5000	50,000	0.3594063	3.969E-02	6.452255E+02	JO example on gitlab
	1750	5000	50,000	0.4153779	3.033E-02	1.648532E+03	JO example on gitlab
	2000	5000	50,000	0.4616152	2.26E-02	1.739071E+03	JO example on gitlab	Validation plots
	2250	5000	50,000	0.4995065	1.633E-02	1.575628E+03	JO example on gitlab
	2500	5000	50,000	0.5305279	1.151E-02	2.164466E+03	JO example on gitlab
	2750	5000	50,000	0.5560033	8.027E-03	3.431793E+03	JO example on gitlab
	3000	5000	50,000	0.5770356	5.58E-03	6.079032E+03	JO example on gitlab
	3250	5000	50,000	0.5945127	3.821E-03	1.12324E+04	JO example on gitlab
	3500	5000	50,000	0.6091368	2.609E-03	1.277041E+04	JO example on gitlab
	3750	5000	50,000	0.6214611	1.765E-03	1.925836E+04	JO example on gitlab
	4000	5000	50,000	0.6319198	1.214E-03	4.119944E+04	JO example on gitlab	Validation plots
	4250	5000	50,000	0.6408556	8.348E-04	6.008717E+04	JO example on gitlab
	4500	5000	50,000	0.6485395	5.89E-04	8.62735E+04	JO example on gitlab	Validation plots
	4750	5000	50,000	0.6551873	4.214E-04	1.242164E+05	JO example on gitlab
	5000	5000	50,000	0.6609715	3.12E-04	1.76481E+05	JO example on gitlab
	1000	7000	50,000	0.1305925	8.523E-03	5.866479E+03	JO example on gitlab	Validation plots
	3000	7000	50,000	0.4854073	1.218E-03	4.10509E+04	JO example on gitlab
	5000	7000	50,000	0.6131864	5.765E-05	8.7063E+05	JO example on gitlab
	5500	7000	50,000	0.6293402	2.869E-05	1.83739E+06	JO example on gitlab
	6000	7000	50,000	0.6422108	1.619E-05	3.436359E+06	JO example on gitlab
	6500	7000	50,000	0.6526012	1.059E-05	6.129468E+06	JO example on gitlab
	7000	7000	50,000	0.6610913	8.041E-06	1.148319E+07	JO example on gitlab
	1000	1000	50,000	0.6482211	9.622E+01	5.196425E-01	JO example on gitlab
	2000	2000	50,000	0.6581329	1.194E+00	4.187605E+01	JO example on gitlab
	3000	3000	50,000	0.6601056	4.922E-02	1.015988E+03	JO example on gitlab
	4000	4000	50,000	0.660733	3.343E-03	1.512976E+04	JO example on gitlab

Analysis milestones

The kick-off meeting 06.07.2020 Weekly meeting of the Exotics: Lepton + X subgroup