Teruki Kamon Collaboration with Bhaskar Dutta, Nikolay Kolev, Kuver Sinha, and Kechen Wang

Transcription

1 Stopping at with the LHC M3 Teruki Kamon Collaboration with Bhaskar Dutta, Nikolay Kolev, Kuver Sinha, and Kechen Wang Mitchell Institute for Fundamental Physics and Astronomy Texas A&M University & Department of Physics Kyungpook National University HEP Seminar University of Hamburg/DESY June 15, 2012 June 2012 Stopping at the LHC with M3 1

2 Prologue Pheno Projects Light Higgs and Heavy 1 st /2 nd Generation Squarks Light Stop and Light Stau Pheno Project #10: Light Stop Summary OUTLINE 2

3 Pheno Projects at A Glance Phys. Lett. B 505 (2001) 161 (Tevatron) Phys. Lett. B 538 (2002) 121 (Tevatron) Phys. Lett. B 611 (2005) 223 (ILC) Phys. Lett. B 618 (2005) 182 (ILC) B s µµ: CDF PRL 107 (2011) Eur. Phys. J. C46 (2006) 43 (LHC+ILC) Supersymmetry Parameter Analysis: SPA Convention and Project Phys. Lett. B 639 (2006) 46 (LHC14) Phys. Lett. B 649 (2007) 73 (LHC14) Phys. Rev. Lett. 100 (2008) (LHC14) Phys. Rev. D 79 (2009) (LHC14) Phys. Rev. D 82 (2010) (LHC14) Focus Point (unpublished) attempted to reconstruct two tops Phys. Lett. B 703 (2011) 475 ( BEST at LHC7) arxiv: accepted in PRD (Mirage at LHC14) arxiv: accepted in PRD (LFV at LHC14) arxiv:12**.???? Stops via Tops (LHC8) SUSY Jets+MET+Taus at LHC7 CMS SUS PAS CMS SUS / Paper (in preparation) Bhaskar Dutta, Teruki Kamon, Nikolay Kolev, Kuver Sinha, Kechen Wang 3

4 Exciting Time! LEP + Tevatron LEP + Tevatron + LHC Narrowing down the Higgs boson mass! The current SM Higgs mass region allowedby LHC+Tevatron+LEP is quite SUSY-friendly 4

5 But, Keep in mind they are preliminary results; Keep in mind they are small numbers; Keep in mind we will run in the next year. Dec. 13,

6 CMS 2011 Physics Precision measurements Very rare decays Searches for new physics with MET No signs of new physics (yet) 6

7 But, The maximum squark and gluino masses excluded by current LHC limits are ~ 1 TeV 7

8 My Daughter s View I need ~ t I need χ 1, χ 2, Uh Oh! The hosts are in 8

9 Benchmark Point 9

10 Benchmark Point 10

11 Stop Searches in Market Stop searches in 2012 Tilman Plehn, Michael Spannowsky, Michihisa Takeuchi, Stop searches in Stop degenerate case Daniele S.M. Alves, Matthew R. Buckley, Patrick J. Fox, Joseph D. Lykken, and Chiu-Tien Yu, Stops and MET: the shape of things to come Spin correlation for stop Zhenyu Han, Andrey Katz, David Krohn, and Matthew Reece, (Light) Stop Signs "FatJet" to tag top David E. Kaplan, Keith Rehermann, Daniel Stolarski, Searching for Direct Stop Production in Hadronic Top Data at the LHC 11

12 Snapshot of Stop Searches Final States Dilepton+Jets+MET 1L+Jets+MET Jets+MET 4 tops Techniques mt2 Razor TopTag (boosted top) M3 12

13 TTbar + jets Single stop production W + jets Z + jets QCD SM Backgrounds s = 7 TeV Two tops along with MET. Challenging, but we need all hadronic channel t jjb tag in one side, W+b tag in other 13

14 TTbar Once we require large MET, a surviving decay mode of TTbar events is Lepton+Jets+MET 6 jets (2 loose b s) + MET + Lepton veto pt(e) > 10, Iso < 5 GeV pt(µ) > 10, Iso < 5 GeV pt(τ h ) > 20, ε= 60%, f = 2% Lost Lepton TTbar Still a major surviving decay mode is Lost Lepton + Jets + MET mode 14

15 Baseline Selection Cuts /E T > 50 ~ 0 t (450) & ~ χ 1 (100) tt + 3jets Baseline Selection: 4 non b-jets (>100, >30 s) + 2 loose b s (>30 s) + MET (>200) S B(top) S/B S/ (S+B) tt + 4jets 15

16 M(top) in Market Kinematical fit (χ 2 ) mt2 M3 FatJet/ TopTagger/ Cambrige-Aachen Algorithm Bi-Event Subtraction Technique (BEST) 16

17 CMS TOP PAS kinematica l fits pt > 60,60,60,60,50,40 (at least 2b jets) Teruki Kamon Stopping at the LHC with M3 17

18 CMS TOP PAS kinematica l fits in µ + jets 18

19 M(TTbar) using mt

20 M3 (TOP PAS) b e,µ,τ ν W t j W t j q q b M 3 M 2 M 20

21 Cambrige-Aacgen Algorithm EXO PAS Z tt q q W t b W t Teruki Kamon b Stopping at the LHC with M3 21

22 HEPTopTagger Michihisa Takeuchi (Uni Heidelberg), Top Reconstruction for New Physics Search (Feb 17, 2012) R C/A < 1.5 FatJet Tagged Teruki Kamon Stopping at the LHC with M3 22

23 pp Detection of W jj and t Wb t t + Bi-Event Subtraction Technique Phys. Lett. B 703 (2011); hep-ph/ j ( W b) ( W b ) + j j l ν j pp W + jjjj l ν BEST: jet mixing from two different events (TTbar, TTbar), (TTbar,W), (W,W) = 23

24 Stop Search Strategy 3 1 q q M3, twice 2 b e,µ,τ W t W t j b ν j 24

25 Reference Stop: Final Selection ~ 0 t (450) & ~ χ 1 (100) Stage 1: Tagging top (j 1, j 2, b) using M3(twice) Stage 2: Probing j 1, j 2, b (lost lepton) Stage 3: Clean-up Two Top system 25

26 /E T > 200 Stage 1: Tagging 1 st Top M 3 Two entries / events 200 M(jjb) top M(jjb) stop p T ( jjb) 40 < M(jj) < 120 M(jjb) top M(jjb) stop M( jj ) M 3 26

27 /E T > 200 Stage 1: Tagging 1 st Top M3 twice M3 once ~33% more signal 40 < M(jj) < 120 & 120 < M(jjb) < 220 p ( t T ) 200 M(jjb) top M(jjb) stop p T (top) > 200 GeV S B(top) S/B S/ (S+B) p T( W ) M(jjb) top M(jjb) stop 27

28 Stage 2: Probing 2 nd Top M(jjb) top 1 q q >1.3 M(jjb) stop φ( b,met) 2 b e,µ,τ ν W t j W t j b >170 M(jjb) top M(jjb) stop M T ( b,met) 28

29 Stage 2: Probing 2 nd Top M(jjb) top 1 q q >1.3 M(jjb) stop φ( b,met) 2 b e,µ,τ ν W t j b W t S B(top) S/B S/ (S+B) j >170 M(jjb) top M(jjb) stop M T ( b,met) 29

30 Stage 3: Clean-ups 3 1 j 1 j 2 φ(b, MET) M(jjb) top M(jjb) stop 2 b e,µ,τ ν W t j 1 W t j 2 φ b φ( j 1,MET) M(jjb) top M(jjb) stop 30

31 Stage 4 & 5: Clean-ups Preliminary S B(top) S/B S/ (S+B) Number of Events/20 GeV 2 40 < M(jj) < 120 M( jjb) M(jjb) sum M(jjb) top M(jjb) stop Improving statistics 40 < M(jj) < 120 & 120 < M(jjb) <

32 Analysis Summary (8 TeV, 50 fb -1 ) Baseline selection cuts: 4 jets + 2 loose b s + MET Final selection cuts Stage 1: Tagging leading pt top (j 1, j 2, b) Stage 2: Probing j 1, j 2, b (lost lepton) Stage 3: Clean-up Two Top system Stage 4: W mass cut Stage 5: top mass cut 8 TeV 450 GeV Stop S B(top) S/B S/ (S+B) Baseline selection [1] 1 st Top [2] 2 nd Top [3] Clean-up [4] W mass [5] Top mass

33 Analysis Summary (8 TeV, 50 fb -1 ) arxiv: v1 [hep-ph] Define pre-selection cuts: 6 jets (2 loose b s) + MET Final selection cuts Stage 1: Tagging leading pt top (J1, J2, B) Stage 2: Probing j1, j2, b (lost lepton) Stage 3: Clean-up Two Top system Stage 4: W mass cut Stage 4: top mass cut 8 TeV 450 GeV Stop S B(top) S/B S/ (S+B) Baseline selection [1] 1 st Top [2] 2 nd Top [3] Clean-up [4] W mass [5] Top mass More or less consistent 0.12 fb 0.37 fb 33

34 Stop Searches in 2012 (I) arxiv: v1 [hep-ph] 34

35 Stop Searches in 2012 (II) Decreasing, because of FatJet? 35

36 Summary arxiv: v1 [hep-ph] The dilepton final state is considered as a golden mode to detect an excess beyond the SM process. However, it is not provide an conclusive answer. All-hadronic mode would be a key, but challenging, mode where one requires to detect two top quarks. A simple kinematical selection technique, M3, is used to tag top quarks in 3-jet system (p T > 200 GeV) and shown to be effective as in an analysis using TopTagger. M3 can be a complementary technique to search for stops for masses around GeV. 36

37 Backup Teruki Kamon Tops and Stops 37

38 Properties used to identify b-jets Hard fragmentation functions Relatively large mass Long lifetime Semi-leptonic decays B-Tagging (at CMS) b-tagging Variables 2D and 3D impact parameters (closest approach to primary vertex) Flight distance Invariant mass of tracks at vertex Number of tracks at vertex (~ 5 for b) Likelihood variables based on these parameters ~70% eff. with light mistag rate ~ 2% 38

39 Tau-Tagging (at CMS) Tau leptons decay to hadrons ~ 65% of the time Tau identification to hadronic decays: Reconstruct decay modes using reconstructed PF particles TAU Cut based: mass of the mesons, rejection against e/µ, and isolation 39

40 Any Further Improvements? m LSP =

41 Few assumptions Many assumptions SUSY Mass Techniques Christopher Lester et al., ICHEP2010, arxiv: Missing momentum M eff, Razor, H T shat min M TGEN M T2 / M CT M T2 (with kinks ) M T2 / M CT ( parallel / perp ) M T2 / M CT ( subsystem ) Polynomial constraints Multi-event polynomial constraints Whole dataset variables Max Likelihood / Matrix Element Teruki Kamon Tops and Stops 41