Search for Supersymmetry at CMS in all-hadronic final states

Transcription

1 Search for Supersymmetry at CMS in all-hadronic final states The 9th Particles and Nuclei International Conference, MIT Matthias Schröder (Universität Hamburg) on behalf of the CMS Collaboration 5 July Matthias Schröder (Universität Hamburg) PANIC, MIT 5 July / 4

2 Introduction Supersymmetry SUSY Is Great Hierarchy problem F. Wilczek, Nature 433, Unification of gauge couplings NASA/WMAP Science Team Dark Matter candidates Supersymmetric particles not observed yet Unknown breaking mechanism Generic, topology-driven searches Matthias Schröder (Universität Hamburg) PANIC, MIT 5 July / 4

3 Introduction All-Hadronic Experimental Signature All-Hadronic Experimental Signature SUSY production at the LHC Strongly interacting sparticles dominate Heavy squarks and gluinos Long decay chains and high p T objects R-parity conservation Pair-production and stable LSP Several high-p T jets Large missing transverse momentum No leptons Matthias Schröder (Universität Hamburg) PANIC, MIT 5 July 3 / 4

4 Introduction Outline Outline: All-Hadronic Searches at CMS Large signal cross section for all-hadronic final states Huge background from Standard Model processes t t, W /Z +jets (same signature) QCD (mis-measurements) Several complementary analysis approaches Each with robust data-driven background estimates Inclusive jets+missing momentum method Precise understanding of backgrounds Razor method Characterises kinematics of pair-production α T method Drastic QCD reduction cut-and-count analyses (36 pb ) } shape analysis (. fb ) Detailed references in the backup Matthias Schröder (Universität Hamburg) PANIC, MIT 5 July 4 / 4

5 Jets + /H T : Overview All-Hadronic Searches Jets + /H T Submitted to JHEP, arxiv:6.453v Precise understanding of backgrounds with minimal model dependence Sensitive variables HT = jets i p T,i /HT = jets p T,i i Baseline selection 3 central jets, p T > 5 GeV /HT not-aligned to jet Suppression of QCD Signal regions H T > 3 GeV, /H T > 5 GeV (GeV) H T > 5 GeV, /H T > 5 GeV Events / GeV CMS s = 7 TeV - L = 36 pb H T Data Z ν ν QCD W t t LM Low-mass SUSY point Matthias Schröder (Universität Hamburg) PANIC, MIT 5 July 5 / 4

6 All-Hadronic Searches Jets + /H T : QCD Background Jets + /H T Submitted to JHEP, arxiv:6.453v /H T from mis-measured jets Prediction using jet resolution (from photon+jet and di-jet events) Adjustment of measured momenta /HT = constraint Consistent with jet resolution Rebalanced momenta smeared by full response function /H T prediction Matthias Schröder (Universität Hamburg) PANIC, MIT 5 July 6 / 4

7 All-Hadronic Searches Jets + /H T : QCD Background Jets + /H T Submitted to JHEP, arxiv:6.453v /H T from mis-measured jets Prediction using jet resolution (from photon+jet and di-jet events) Events /(5 GeV) H T 3, φ.5, φ 3.3 CMS Simulation s = 7 TeV - L = 36 pb Adjustment of measured momenta R + S /HT = constraint MC truth Consistent with jet resolution H T (GeV) Rebalanced momenta smeared by full response function /H T prediction Closure of 35% at high /H T Matthias Schröder (Universität Hamburg) PANIC, MIT 5 July 6 / 4

8 All-Hadronic Searches Razor Razor: Overview Submitted to PRD, arxiv:7.79 R Characterises kinematics of heavy particle pair-production q q jjχ χ pseudo-jets QCD CMS Simulation s=7 TeV - L dt = 35 pb 5 5 M R [GeV] Events / bin R tt+jets M R = (E p z, E p z, ) (p z, p z, ) (E E ) estimator of M = M q M χ M q MT R = /E T (p T, +p T, ) / E T ( p T, + p T, ) edge at M Razor R = M R M R T CMS Simulation s=7 TeV - L dt = 35 pb 5 5 M R [GeV] Events / bin R >.5 R SUSY LM CMS Simulation s=7 TeV - L dt = 35 pb Signal region 5 5 M M [GeV] R> 5 GeV R Matthias Schröder (Universität Hamburg) PANIC, MIT 5 July 7 /

9 All-Hadronic Searches Razor Razor: QCD Background Submitted to PRD, arxiv:7.79 / GeV N evt 4 3 CMS s=7 TeV - L dt = 35 pb [GeV] M R R >.5 R >. R >.5 R >.3 R >.35 R >.4 R >.45 R >.5 Slope Parameter [/GeV] CMS s=7 TeV - L dt = 35 pb QCD data: M R falls exponentially Slope scales linearly with (cut on R) QCD prediction in signal region M R > 5 GeV, R > (R threshold) Matthias Schröder (Universität Hamburg) PANIC, MIT 5 July 8 / 4

10 All-Hadronic Searches Razor Razor: QCD Background Submitted to PRD, arxiv:7.79 / GeV N evt 4 3 CMS s=7 TeV - L dt = 35 pb [GeV] M R R >.5 R >. R >.5 R >.3 R >.35 R >.4 R >.45 R >.5 Slope Parameter [/GeV] CMS s=7 TeV - L dt = 35 pb QCD data: M R falls exponentially Slope scales linearly with (cut on R) QCD prediction in signal region M R > 5 GeV, R > L dt = 35 pb! (R threshold) M R in data and predicted [GeV] M R Events / 5 GeV 4 CMS s=7 TeV - HAD BOX DATA Total SM QCD W+jets Z+jets Top+X LM LM Matthias Schröder (Universität Hamburg) PANIC, MIT 5 July 8 / 4

11 α T : Overview All-Hadronic Searches α T CMS Preliminary CMS PAS-SUS--3 Drastic QCD background reduction Momenta of QCD multi-jets balance in transverse plane For di-jets: α T = pt, /p T, ( cos φ) Events / L dt =. fb, s = 7 TeV Data Standard Model QCD MultiJet tt, W, Z + Jets LM4 LM α T QCD di-jets: α T =.5 (.5 due to jet resolution) Processes with genuine /E T : α T also >.5 Generalised to multi-jet events by combination into two pseudo-jets Matthias Schröder (Universität Hamburg) PANIC, MIT 5 July 9 / 4

12 T All-Hadronic Searches α T : Background Estimation Rα T = N(α T>.55) N(α T <.55) R α CMS Preliminary -. fb Data (hadronic sample) SM (QCD + EWK) EWK QCD s = 7 TeV α T H T (GeV) Background yields from control samples t t, W +jets yields from W µν+jets Z+jets yield from γ+jets CMS PAS-SUS--3 t t, W /Z: real /E T Constant R αt QCD: /E T from jet mis-measurements Better resolution for larger H T Expect falling R αt Signal sample QCD free Signal and control samples fitted simultaneously Constant RαT (H T ) for t t, W /Z Exponentially decreasing R αt (H T ) for QCD Matthias Schröder (Universität Hamburg) PANIC, MIT 5 July / 4

13 Results Predicted and Observed Event Yields Results: Predicted and Observed Event Yields all-hadronic analyses (36 pb ) α T analysis (. fb ) CMS Preliminary -. fb s = 7 TeV Pred. Obs. Sig. Acc. Jets+/H T High /H T 8.8 ± % High H T 43.8 ± % Razor 5.5 ±.4 7 5% counts / bin 3 Data (hadronic sample) SM (QCD + EWK) EWK (tt + W + Z νν) Z νν LM6 (LO) H T (GeV) No excess observed w. r. t. SM prediction Matthias Schröder (Universität Hamburg) PANIC, MIT 5 July / 4

14 Results Limits On The Constrained MSSM Results: Limits On The Constrained MSSM all-hadronic analyses (36 pb ) (GeV) m / τ = LSP 5 5 CMS preliminary α T LM Razor q~(5)gev q~(8)gev q~(65)gev OS Dilepton SS Dilepton α T +b-tag L Lepton+MET int - = 36 pb, tanβ =, A s = 7 TeV CDF g ~, ~ q, tanβ=5, µ< D ± LEP χ ~ g ~ ± (8)GeV LEP l Jets+MHT g ~, q ~, tanβ=3, µ< =, µ > g ~ (65)GeV g ~ (5)GeV (GeV) 95% C. L. exclusion limit Significant extension of excluded region over previous experiments Matthias Schröder (Universität Hamburg) PANIC, MIT 5 July / 4 m

15 Results Limits On The Constrained MSSM Results: Limits On The Constrained MSSM α T analysis (. fb ) (GeV) m / 6 4 CMS preliminary τ = LSP LM6 q ~ (5)GeV q ~ (5)GeV q~()gev q~(75)gev α T 95% C.L. Limits: Observed Limit (NLO), CL s Observed Limit (NLO), PL Median Expected Limit ± σ, PL - Observed Limit (NLO), FC, 35pb Ldt =. fb tanβ =, A - s = 7 TeV CDF g ~, ~ q, tanβ=5, µ< D g ~, ~ q, tanβ=3, µ< g ~ ± LEP (5)GeV χ ~ ± LEP l =, µ > g ~ (5)GeV g ~ ()GeV LM4 q~(5)gev g ~ (75)GeV g ~ (5)GeV 5 5 (GeV) 95% C. L. exclusion limit Exclusion of squark masses. TeV (tan β =, A =, µ > ) m Matthias Schröder (Universität Hamburg) PANIC, MIT 5 July 3 / 4

16 Summary & Conclusions Summary & Conclusions CMS is performing SUSY searches in the all-hadronic final states Several complementary analysis strategies All measure the Standard Model background from data No excess over Standard Model expectation in up to. fb Results constrain the SUSY parameter space m q. TeV excluded at 95% C. L. in CMSSM (tan β =, A =, µ > ) CMS is ready for discoveries Matthias Schröder (Universität Hamburg) PANIC, MIT 5 July 4 / 4

17 Backup Backup Matthias Schröder (Universität Hamburg) PANIC, MIT 5 July 5 / 4

18 Backup References References I CMS Supersymmetry Physics Results PhysicsResultsSUS Inclusive jets+missing momentum analysis Search for New Physics with Jets and Missing Transverse Momentum in pp collisions at s = 7 TeV Submitted to JHEP, arxiv:6.453v CMS-SUS--5, CERN-PH-EP--65 Razor analysis Inclusive search for squarks and gluinos in pp collisions at s = 7 TeV Submitted to PRD, arxiv:7.79 CMS-SUS--9, CERN-PH-EP--99 Further material C. Rogan, Kinematics for new dynamics at the LHC, (). arxiv:6.77. CALT Matthias Schröder (Universität Hamburg) PANIC, MIT 5 July 6 / 4

19 Backup References References II α T analyses Search for Supersymmetry in pp Collisions at 7 TeV in Events with Jets and Missing Transverse Energy Phys. Lett. B 698 () 96, arxiv:.68. doi:.6/j.physletb..3.. Further interpretation: CMS-PAS-SUS-- Search for Supersymmetry in Events with b Jets and Missing Transverse Momentum at the LHC Submitted to JHEP, arxiv:6.37 CMS-SUS--, CERN-PH-EP--67 update CMS PAS-SUS--3 Further material L. Randall and D. Tucker-Smith, Dijet Searches for Supersymmetry at the LHC, Phys. Rev. Lett. (8) 83. doi:.3/physrevlett..83. Matthias Schröder (Universität Hamburg) PANIC, MIT 5 July 7 / 4

20 Backup The CMS Experiment Matthias Schröder (Universität Hamburg) PANIC, MIT 5 July 8 / 4

21 Backup CMSSM Benchmark Points CMSSM Benchmark Points MSUGRA, tanβ =, A =, µ > m / (GeV) 4 τ ~ LSP HM Br( χ ~ ~ l l) >.5 HM m(e ~ L )<m(χ ) HM LM6 4 LM5 LM LM4 LM8 Br( χ ~ Z χ ~ ) >.5 LM LM3 4 m h = 4 GeV LM7 5 6 m χ = 3 GeV LM9 ~ l Teva tron NO EWSB m (GeV) m(u ~ L ) > m(g~ ) Br( χ ~ h χ ~ ) >.5 m h = GeV m h = GeV HM4 9 m(t ~ ) < m(g~ ) 8 6 LM CMS Collaboration, CMS Technical Design Report, Volume II: Physics Performance, J. Phys. G 34 (7) 995. doi:.88/ /34/6/s. Matthias Schröder (Universität Hamburg) PANIC, MIT 5 July 9 / 4