2016 SM H ττ Analysis 26th September 2016

Transcription

1 2016 SM H ττ Analysis 26th September 2016 INSTITUT FÜR EXPERIMENTELLE KERNPHYSIK (EKP) FAKULTÄT FÜR PHYSIK KIT Universität des Landes Baden Württemberg und nationales Forschungszentrum in der Helmholtz Gemeinschaft

2 Higgs? The Higgs mechanism is a way to explain the masses of the W and Z bosons by introducing a field with an energy ground state that is not symmetric under SU (2)L transformations The Higgs coupling is (for force mediating & boson) (for weakly interacting fermions) 2

3 Discovery of a new particle 4th of July

4 Higgs Boson production Gluon fusion Vector boson fusion (VBF) Associated production Electroweak Sector Top Sector Higgs Sector Strong Sector 4

5 Higgs Boson decay modes Higgs boson mean lifetime : s too heavy large backgrounds low mass perfect! 5

6 2ν Tau decays Branching ratio mean τ liftetime: Leptonic s 1-prong W e, e,,d,u 3-prong 6

7 Z τ τ Highest irreducible background contribution Often in boosted Z+Jets topologies 7

8 real or fake? 8

9 Jets faking hadronic τ decays - and some real ones 2ν t t W+Jets, Di-Boson 9

10 Tau reconstruction and identification start with jets with pt > 14 GeV Hadron Plus Strips algorithm Rejection against jets to reach high purity, e.g. Cut-based isolation: MVA based tau-id MVA & cut based anti-electron ID MVA & cut based anti-muon ID 10

11 Reconstruction of the missing energy Missing transverse energy (MET): momentum in plane perpendicular to beam axis, in theory equivalent to neutrino momentum A multivariate regression technique removes biasing effects and gives an estimation of phase space of the neutrinos f (Σ )= MET MET σ x σy

12 Bringing it all together: full reconstruction of the di-tau system di-tau decays result in 2 to 4 neutrinos in the final state -> under-constrained problem 3 free parameters per tau decay fraction of visible energy azimuthal angle invariant neutrino mass Additionally known: MET (2 parameters) Calculate probability of di-tau hypothesis to be true and take the mass with the highest probability π τ a a τ +a ντ MET ν τ νμ μ +a 12

13 Analysis strategy Selection depending on final state Starting the background estimation with simulated Events Applying a reasonable set of selection steps Data-Based background estimation techniques Cross check simulation in control regions 13 μ Run lumi-section 315 fireworks event bilder τ

14 Selection steps inclusive 14

15 Selection steps inclusive opposite charge 15

16 Selection steps inclusive opposite charge muon isolation 16

17 Selection steps inclusive opposite charge muon isolation tau isolation 17

18 Selection steps inclusive opposite charge muon isolation tau isolation b-tag veto 18

19 Selection steps inclusive opposite charge muon isolation tau isolation b-tag veto transverse mass 19

20 Selection steps inclusive opposite charge muon isolation tau isolation b-tag veto transverse mass 20

21 Selection steps inclusive opposite charge muon isolation tau isolation b-tag veto transverse mass 21

22 Selection steps inclusive opposite charge muon isolation tau isolation b-tag veto transverse mass 22

23 Selection steps inclusive opposite charge muon isolation tau isolation b-tag veto transverse mass 23

24 Selection steps inclusive opposite charge muon isolation tau isolation b-tag veto transverse mass 24

25 Selection steps inclusive opposite charge muon isolation tau isolation b-tag veto transverse mass 25

26 Selection steps inclusive opposite charge muon isolation tau isolation b-tag veto transverse mass 26

27 Final selection in all four decay channels bins with significant signal expectation blinded 27

28 Event categorization Gluon fusion No jets in decay, but one in boosted topologies 29 Vector boson fusion Two jets with large gap

29 Categorization in terms of jet multiplicity 0 jets 30 1 jet >1 jet

30 Further signal extraction >1 jet VBF-enriched region 31

31 Expected Significances with 12.9 fb Jet binned combined: 1.8 Categorized combined: Channel μ τ had e τ had τ had τ had eμ Channel μ τ had e τ had τ had τ had eμ 1 0 jets 1 jet > 1jet jets 1jet low 1 jet high > 1jet VBF

32 Thank you for your attention! 35