1. Tau Jet Identification in Charged Higgs Search Monoranjan Guchait TIFR, Mumbai India-CMS collaboration meeting 27-28 th March,2009 University of Delhi M.Guchait, R.Kinnunen, M.Kortelainen, Sami Lehti A. Nikitenko, L. Wendland CMS AN 09/036

2. Motivation MSSM: 5 Higgs h, H, A, H +, H - Standard model: one Higgs, mass is not predictable Predictable in terms of Parameters Two parameters: M A and tanβ Signature of Charged Higgs carry unambiguous Signal of NEW Physics

3. Charged Higgs Production Coupling High tanβ

4. Charged Higgs Decay H → t b is dominant for Higher higgs, but huge contamination H→ tau + nu is Sub-dominant, useful to find the Higgs signal

5. Tau decay and Helicity Correlations ~ 2/3

6. Tau polarization Angular distributions ~

7. Helicity Correlations Fast simulations Guchait,Kinunnen,Lehti, CMS IN 2008/008 1 prong 3 prong

8. Event Samples CMSSW 1_6_12 + TAUOLA for tau decays Signal for MH=200,300,400, tanβ=30 250 K events QCD(PYTHIA) Pt_hat=80-230 GeV 3.4 M events tt + 0/1 jets(ALPGEN) 1.8 M events W+3/4 jets Peak sample:MW<150 GeV, 1.3 M events Tail sample: MW>150 GeV, BW, 76 K events Signal QCD ttbar W+3/4 jets

9. Jet and Track Reconstruction Calorimeter tau jets(Calotau)are used MC based jet energy corrections are used CMS IN 2007/029 Iterative tracking used for tracks Tracks down to pt>0.3 GeV are used CMS IN 2007/035 Jet energy resolution for MC matched calorimeter tau jets (CaloTau) for m H+ =300 GeV/c 2

10. Why to Optimize against QCD BG [P-TDR II]: The transverse mass (m T ) of the H + is reconstructed from the tagged tau and the MET –H +   events acquire m T values mainly up to m H+ –W   events acquire m T values mainly up to m W –QCD multi-jet events may fake tau jet and MET; o can contaminate the signal region o very large cross-section –also off-shell W   events can contaminate the m T signal regio –but relatively low cross- section  Optimize against QCD multi-jet background and use helicity correlations to suppress W   decays

11. Selection Strategy for 1 prong Jet E T > 119 GeV, jet eta: |  |<1.7 Leading track p T >20 GeV/c –through R  cut, p T >95 GeV/c 1 isolated charged track –isolation cone  R=0.50; min. track p T >1.0 GeV/c Standard track quality cuts –N hits >=8, normalized track  2 <10, IP T <300  m, |  IP z |<1 mm

12. Selection Strategy for 1 prong Isolated electromagnetical energy deposition –isolation annulus  R=0.10-0.50, allowed energy E T isol <1.8 GeV Matching of track momentum to hadronic energy deposition –to reject electrons; E T HCAL / p T track - 1 > -0.90 Helicity correlations, R  =p track /E vis.  jet > 0.8 –to suppress taus from W   decays –suppresses further also hadronic jets with neutral particles

13. Jet Et threshold Jet Et threshold of 119 GeV was found to be optimal against QCD multi-jet events in the 1-prong final state The high jet E T threshold viable also for signal with m H+ ~m t Efficiency of the jet E T threshold for MC matched H +   decays PAS Figure 2 after all other cuts

14. Electromagnetic Isolation Due to the boost effect, the  0 ’s are contained within a narrow cone in tau decays; the ECAL energy deposition is calculated in an isolation annulus around this signal cone [CMS Note 2006/028] Optimum cut for 1-prong: E T isol. <1.8 GeV in an annulus of  R=0.10-0.5

15. Electron rejection Main sources of electrons are –W  e e and W     e e  decays These electrons can be effectively suppressed by matching the HCAL energy deposition to the momentum carried by the track, i.e. E T HCAL /p T track -1 = R e –the HCAL energy is summed in a cone of  R=0.50 around the leading track axis Optimum cut was found to be given by R e > -0.90

16. Tracker Isolation Low charged track multiplicity and isolated track signature in tau jet Required 1 charged track in isolation cone of 0.50 Counted tracks with p T > p T min to filter out very soft tracks Only tracks from interaction vertex were considered –|  IP z |<1 mm Rejected tracks, which consist of hits belonging to different tracks –IP T <300  m [CMS Note 2006/028] Optimum choice for 1 prongs: –p T min =1.0 GeV/c (same as at trigger level) –could use smaller value (e.g. 0.7 GeV/c), if necessary

17. Tau Helicity Correlation Different polarization effects in tau decay from H and W decay is exploited R  distribution including all 1- prong tau decay modes after all other cuts PAS Figure 7 after all other cuts Signal eff ~ 0.5 Bg ~ 0.2 or less Tracker Calorimeter

18. Selection strategy for 3 prongs Choose a 1 +   +  +  - decays (2/3 of 3-prongs) Jet E T > 100 GeV, jet eta: |  |<1.8 Leading track p T >20 GeV/c (to mimic single tau trigger) 3 isolated charged tracks –isolation annulus  R=0.04-0.50; min. track p T >0.8 GeV/c Standard track quality cuts –N hits >=8, norm. track  2 <10,  Q track = ±1, IP T <300  m, |  IP z |<1 mm Isolated electromagnetical energy deposition –isolation annulus  R=0.15-0.50, allowed energy E T isol <1.8 GeV Matching of energy carried by the tracks to calorimeter energy –  E=  E tracks /E jet -1 > -0.2; to reject neutral hadrons Flight path of the tau lepton and tau invariant mass Helicity correlations, R  =p ldg.track /E vis.  jet > 0.55 –to suppress taus from W   decays –suppresses further also hadronic jets with neutral particles

19. Tau invariant mass tau invariant mass calculated from the tracks (no  0 ’s) –robust method –signal distribution is a distinct peak smeared a little due to the tau neutrino Optimum value of m  <1.5 GeV/c 2 chosen

20. Rejecting Neutral hadrons Energy carried by the tracks is matched to the jet energy to reject jets with considerable neutral particle content –select the a 1  3  + decay for the signal (~2/3 of 3-prongs) Optimum value of  E=  E tracks /E jet -1 > -0.2 chosen

21. Helicity Correlations Can be used R variable More useful is Optimum cut value >0.5 Rejects good fraction from W

22. Summary of Results: 1prong Signal QCD ttbar W+3/4 jets

23. Summary of Results: 3 prong Signal QCD ttbar W+3/4jets

24. Summary of Results:Signal H+ 200 H+ 300 H+ 400 1-prong13.42.711.73 error±0.4±0.09±0.04 Efficiency1.7 %3.2 %4.6 % purity99.5 %98.8 %99.6 % 3-prong2.90.820.37 error±0.2±0.04±0.02 Efficiency0.37 %0.70 %0.98 % purity99.0 %99.7 %99.8 %

25. Summary of Results:QCD QCD 80-120 QCD 120-170 QCD 170-230 <240048001400 ±1400±400 <7.9e-79.7e-61.4e-5 <2400<400220 ±150 <7.9e-7<8.0e-72.2e-6 1 prong Error Eff. 3 prong Error Eff.

26. Summary of Results: ttbar, W+3/4 jets ttbarttbar +1 jet 6227 ±5±4 1.0e-41.5e-4 3813.8 ±4±2.5 6.1e-57.8e-5 1 prong Error Eff. 3 prong Error Eff. W+3j peak W+4j peak W+3j tail W+4j tail 1.60.760.400.07 ±1.2±0.4±0.11±0.02 2.8e-66.2e-63.7e-43.6e-4 1.60.760.200.022 ±1.2±0.44±0.08±0.010 2.8e-66.2e-61.9e-41.1e-5

27. Conclusions Robust tau jet idenfication presented for the H +   channel –The tau jet ID part without helicity correlations is basically a standard tau ID with a high p T cut Tau-identification successful for 1-prong final states –Signal efficiency 1.7-4.6 % with high signal purity –QCD multi-jet background can be reduced by a factor of ~10 5 or better –Also the ttbar and W+jets backgrounds are suppressed strongly, due to hadronic jets suppression and tau polarization effects on W   decay 3-prong final states can be used –21-30 % increase in signal –10-15 % increase in QCD multi-jet events, but ttbar background increases with ~3-4 times and W+jets with ~4-6 times as much as the signal –precise estimation of background events would require factorization (or huge MC production)