Searches for SUSY in events with di-leptons at CMS

Transcription

1 Searches for SUSY in events with di-leptons at CMS SUSY 22, Beijing Daniel Sprenger. Physikalisches Institut B RWH Aachen University

2 SUSY Searches in Di-lepton Events at CMS Why di-leptonic final states? CMS SUSY searches cover wide range of final states Leptons (especially e and µ) provide handle to control QCD and other SM backgrounds Di-leptonic final states represent good compromise between background control and production rate CMS di-lepton SUSY searches Selection of analyses performed on 5 fb of 7 ev data (2) and 4 fb of 8 ev data (22) wo leptons, jet activity and ing transverse energy ( E ) required Mainly data-driven methods for background estimation D. Sprenger Searches for SUSY in events with di-leptons at CMS 2/4

3 Introduction Opposite-sign Di-lepton Searches Same-sign Di-lepton Searches Summary he Compact Muon Solenoid D. Sprenger Searches for SUSY in events with di-leptons at CMS 3/4

4 Generic Opposite-Sign Di-lepton Search at 7 ev Various signal regions defined in E -H plane Prediction of SM background using similarities of E distribution and dilepton-p distribution Search includes hadronically decaying tau leptons (GeV) MISS E CMS s = 7 ev, Ldt = 4.98 fb 6 8 H (GeV) eτ µτ ττ low H high H MISS high E tight H = jets p ee, eµ, µµ event yields eτ, µτ, ττ event yields D. Sprenger Searches for SUSY in events with di-leptons at CMS 4/4

5 Generic Opposite-Sign Di-lepton Search at 7 ev No deviations from SM observed Limits on new-physics event yields in various signal regions set Interpretation of combined limits in CMSSM Events CMS, s = 7 ev, L dt = 4.98 fb Light leptons channels hadronic-τ (eτ/µτ/ττ) Light leptons channels hadronic-τ (eτ/µτ/ττ) H > H > 6 E > 275 E > All units in GeV Light leptons Observed MC irreducible p (ll) prediction L prediction otal Uncertay channels hadronic-τ (eτ/µτ/ττ) H > 6 E > 275 Light leptons Predicted and observed event yields channels hadronic-τ (eτ/µτ) > H > 25 E > 275 (GeV) m / = LSP τ tan(β)= A = GeV µ > m t = 73.2 GeV q ) = g ) = CMS q) = observed observed (±σ theory) expected expected (±σ stat) observed 2 s = 7 ev, LEP2 LEP2 2 m (GeV) q ) = ± l ± χ L dt 4.98 fb g ) = q ) = 2 LM LM3 LM6 LM3 Non-Convergent RGE's No EWSB D. Sprenger Searches for SUSY in events with di-leptons at CMS 5/4

6 Opposite-Sign Di-lepton Mass-Edge Search at 7 ev Search for kinematic edges in the lepton-pair invariant-mass spectrum, as can be produced by neutralino decays Perform fit to di-lepton mass distribution Fit components Component for flavour-symmetric background, fitted to eµ channel Z lineshape for DY contribution riangular mass-edge signal shape Events /. GeV 45 CMS Simulation s = 7 ev, 4 L dt = 4.98 fb H >, E Simulation > 5 (SM +.2 x LM) m max = 78 GeV N S = 7.3 ± 5. N B = 23.7 ± 5.2 N Z = 3.9 ± m ll [GeV] Fit Signal DY eµ-shape Uncertay Fit example on simulated signal D. Sprenger Searches for SUSY in events with di-leptons at CMS 6/4

7 ) s Opposite-Sign Di-lepton Mass-Edge Search at 7 ev 3. SMS Construction Events /. GeV 25 CMS s = 7 ev, L dt = 4.98 fb Data m ll (GeV) Fit Signal DY eµ-shape Uncertay Fit to inv. mass distribution No significant kinematic edge observed Limit on new physics determined depending on mass-edge position (m max ) Interpretation of limits using simplified model signal 95% CL Upper Limit on n the neutralino would then subsequently decay o a decay including the LSP. he SMS with cascade decays are eresting to study the LSP is reduced, for a fixed mother mass, as wh undergo cascade decays, the number of jets per even decays, and the spectrum of jet energies will depe presence of cascade decays may be a benefit or detrim l + 9 CMS CLs observed limit χ l 2 8 LM x.2 s = 7 ev, L dt = 4.98 fb χ Expected ± σ Expected ± 2 σ 7 χ Shape variation 6 P 4 Results with Simplifiedq Models 6 q q)>>g + pp g g, g q q χ, g q q χ, χ l l χ ; ) pp g Figure g, g q q χ3:, g Diagrams q q χ, χ l l - χof ; the q)>>g dilepton ) mod.4 CMS Preliminary CMS Preliminary 4 s = 7 ev, Ldt=4.98 fb.35 s = 7 ev, Ldt=4.98 fb 3 OS e/µ edge OS e/µ edge q.3 NLO-QCD σ NLO-QCD 2 /3 σ 8 P2 q.25 8 NLO-QCD 3 σ W ± χ ± χ m max (GeV) χ. q P -2 Limit depending on mass-edge position.5 q gluino mass [GeV] gluino Figure mass 4: Diagrams [GeV] of 3w ( LSP mass [GeV] χ ) =.5 χ ) +.5 g ) 2 A ε D. Sprenger CMS Preliminary Searches for SUSY in he events masswith of the CMS di-leptons ermediate Preliminary atparticle CMSfor cascade 7/4dec ev] pp g g, g q q χ, g q q χ, χ + l l - χ ; q)>>g ) ε LSP mass [GeV] P2 χ ) =.5 χ ) +.5 g ) 2 ev] pp g g, g q q χ, g q q χ, χ + - l l χ q q ; q)>>g ) ) s σ [pb] (CL 95% CL upper limit on L

8 Opposite-Sign Di-lepton Search on Z Peak at 7 ev 7 een the observed and predicted distributions is shown in Fig. 2. he ed yields in the signal regions are summarized in able 2, along with (CL) upper limits on the yields of any non-sm process. Upper limits are t this paper using a modified frequentist method (CLS) [43, 44]. he nuicribed in Section 6) are modeled with a lognormal distribution. able 2 nd LM8 yields, determined using NLO production cross sections. hese account for the contribution of signal to the background control regions, ess the apparent yield of signal in the signal region. he correction is ng the signal samples to the same procedures as the data and subtracting n from the signal yield in the signal region. he expected LM4 and LM8 er limits on the non-sm contributions to the yields in the high JZB signal Search in Z + jets and E final states JZB variable describes balance of Z and jets Expect JZB symmetric around zero for SM Z, and positive for signal (real E ) No significant excess observed Interpretation of limits using simplified model 5 events / GeV data/pred CMS, s = 7 ev, L Data = 4.98 fb otal background JZB< (data) Sidebands/eµ LM4 LM8 (data) JZB [GeV] mass [GeV]! 8 6 CMS, s = 7 ev, L = 4.98 fb pp % g g, g % 2j +!,! % Z! 2 2 q) >> g), x =.5 JZB > 5 GeV n jets " JZB [GeV] gluino mass [GeV] gluino mass [GeV] between the measured JZB distribution in the JZB Figure > region 5: Limits andon that the SMS topology described in the text, based on the JZB method: (left) signal efficiency times control samples. he distribution from the LM4 acceptance MC is overlaid. normalized heto the number of events with at least one Z decay for the JZB > 5 GeV region; (right) e ratio between the observed and predicted distributions. 95% CLhe upperd. error limits Sprenger bars on the total Searches gluino pair-production for SUSYcross in events section. he withregion di-leptons to the leftat ofcms the solid contour 8/ (" Z(ll)) A $ # mass [GeV]! 8 6 CMS, s = 7 ev, L = 4.98 fb pp % g g, g % 2j +!,! % Z! 2 2 q) >> g), x =.5 n jets # 3 " NLO-QCD 3 $ " NLO-QCD /3 $ " NLO-QCD JZB -2 95% CL upper limit on " [pb]

9 Opposite-Sign Di-lepton Search with ANN at 7 ev Search in OS di-lepton events using an artificial neural network Seven input variables ( E, n jets, jet p,...) Sensitivity extends to lower H and E values than generic search No significant excess observed H (GeV) CMS Preliminary L = 4.98 fb Data s = 7 ev ME (GeV) H and E of signal-like events (ANN >.95) Events SMS Low ME/H events SM Background ANN output 2 ANN output for simulated signal and background m [GeV] [GeV] m / = LSP τ tan(β)= A = GeV µ > m t = 73.2 GeV q) = q ) = LEP2 LEP2 ± l ± χ q ) = q) = 2 CMS Preliminary s = 7 ev, Ldt = 4.98 fb g ) = Expected Observed Expected ± Observed ± σ exp.) σ g ) = theor.) g ) = g ) = Non Convergent RGE s No EWSB D. Sprenger Searches for SUSY in events with di-leptons at CMS 9/4

10 Same-Sign Di-lepton Search at 7 ev Search in di-lepton events with same-sign leptons Very low SM background in these final states Various signal regions defined by 3 H and E cuts Hadronically decaying tau leptons included (GeV) E 25 µ µ 5 5 CMS s = 7 ev, L = 4.98 fb Region Region 2 ee eµ µ! e!!! Region 4 Region 3 Region H (GeV). Background determination Fake-lepton background determined using tight-to-loose method Charge-flip background estimated from OS lepton pairs (charge-flip rate determined in Z ee events) Rare SM processes (t tw, t tz, WW, WZ,...) predicted using MC SS dilepton events in the various search regions displayed in the H, D. Sprenger Searches for SUSY in events with di-leptons at CMS /4

11 Same-Sign Di-lepton Search at 7 ev No significant deviations from SM prediction found Limits set and erpreted in CMSSM 6 Events CMS s=7 ev L = 4.98 fb 7 Data Charge Mis-Id High p Low p High p Low p High p Prompt-Prompt(irreducible) Nonprompt-Nonprompt Prompt-Nonprompt Low p High p au channels (e!/µ!/!!) High p Region : Region 2: Region 3: Region 4: Region 5: > 8 GeV > GeV > 45 GeV > 45 GeV > 45 GeV H H H H H E > 2 GeV E > 2 GeV E > 5 GeV E > 2 GeV E > GeV Observed and predicted event yield Figure 3: Exclusion region, below the red curve, in the CMSSM corresponds to t 2 m (GeV) background predictions and observed yields in the various search recays of W, Z, and NP particles are referred to as prompt leptons. he in various signal regions t the total uncertay on the background predictions. (GeV) m /2 CMS L = 4.98 fb = 7 ev, s = LSP " # tan($)= A = GeV µ > m t = 73.2 GeV q) = q ) = LEP2 LEP2 ± l " ±! q) = q) = 2 Observed Limit (NLO+NLL with uncertaies) Expected Limit (NLO+NLL) NLO Obs. Limit (L = 35 pb ) g ) = g ) = g ) = g ) = Non-Convergent RGE's No EWSB upper limits on the number of events from NP. he central observed curve, wh experimental uncertaies, is obtained using high p leptons with H > 45 GeV 2 D. GeV. Sprenger he hatched Searches region for SUSY corresponds in events to the with theoretical di-leptonsuncertaies at CMS on /4 the c

12 6 7 Models of new physics ee Same-Sign eµ Di-leptont Search t with b tag at 7 ev µµ 6 H (GeV) Events / GeV P χ χ Same-sign lepton pair and at least two b jets required Similar background χ determination as for generic search t in same-sign final states No significant excess observed CMS Preliminary, s = 7 ev, L = 4.7 fb CMS, s = 7 ev, L = 4.98 fb 6 7 Models of new physics 8 H > 8 GeV Same Sign dileptons with btag selection prod t t 7 Exclusion # = # NLO+NLL ± # t t P Results t erpreted within several simplified models t (one Figure example 3: Diagrams shown) for models A (left) and A2 (right). t t.4.2 # " ) = 5 GeV P P2 8 # " ) = 5 GeV E (GeV) t t t t for theobserved seven events andinpredicted SR; Figure ee events: 3: Diagrams circles; yield for models eµ A (left) and A2 (right). left plot: projection ofvs the Escatter plot on the H CMS, s = 7 ev, L er plot on the E/ axis. For the one-dimensional = 4.98 fb g) GeV g) GeV CMS, s = 7 ev, L = 4.98 fb 8 Same Sign dileptons with btag selection Same Sign dileptons with btag selection ckground predictions, 7 with their Figure prod Exclusion # = # uncertaies. 4: Results NLO+NLL ± # 9 from the 2 prod 7 ev CMS run of Ref. [2]. Left plot: exclusion (95 % CL) in the Exclusion! =! NLO+NLL ±! 8 6 χ ) ) plane for model A (gluino decay via virtual top squarks). Right plot: exclusion 7 (95% CL) in the t 6 ) ) plane for model A2 (gluino decay to on-shell top squarks). he D. Sprenger Searches for SUSY in events with di-leptons at CMS 2/4! " ) GeV P2 ) GeV P! " 6 t ) GeV t χ χ χ t ) GeV P 2 P CMS, s = 7 ev, L = 4.98 fb Same Sign dileptons with btag selection prod Exclusion! =! NLO+NLL ±! t t t χ χ t

13 Introduction eµ Opposite-sign Di-lepton Searches Same-sign Di-lepton Searches Summary µµ Same-Sign Di-lepton Search with b tag at 8 ev New: reload of analysis with 8 ev data 6 (GeV) H Analysis similar to search on 7 ev data Updated object/event selection to account for new beam conditions (pileup, trigger,...) No significant deviations from SM observed 7 CMS Preliminary s = 8 ev L. = 3.95 fb CMS Preliminary, s = 8 ev, L = 3.95 fb 2.5 H > 8 GeV, N! 2 Observed 8 b-jets Fakes Same Sign dileptons with btag selection Irreducible (MC) prod Charge MisID 2 7 Exclusion # = # NLO+NLL ± # otal Uncertay 6.5 Events / GeV! " ) GeV E 9 (GeV) g) GeV Observed and predicted event yield vs E g) GeV s. H for the 3 events in the baseline region (SR). Figure 5: Same as Fig. 4, but for 8 ev data. mplies H > 8 GeV. Bottom left plot: projection of t plot: projection of the scatter plot on the E axis. number of events in each bin is scaled appropriately D. Sprenger Searches for SUSY in events with di-leptons at CMS 3/4 W t ) GeV CMS Preliminary, s = 8 ev, L = 3.95 fb Same Sign dileptons with btag selection prod Exclusion! =! NLO+NLL ±! # " ) = 5 GeV # " ) = 5 GeV

14 Summary and Outlook Summary Various SUSY searches performed by CMS in events with two leptons No signs of new physics observed in 5 fb of 7 ev First results on 4 fb of 8 ev data Results erpreted within CMSSM and various simplified models Outlook Further analysis of 8 ev data in progress For more information, please visit: D. Sprenger Searches for SUSY in events with di-leptons at CMS 4/4

15 Backup D. Sprenger Searches for SUSY in events with di-leptons at CMS 5/4

16 Summary of CMS Exclusion Limits [GeV] m / = LSP τ CMS Preliminary q ) = Jets+MH Razor q ) = SS Dilepton L q ) = = 4.98 fb, g ) = M2 q) = 2 s = 7 ev tan(β)= A = GeV µ > m t = 73.2 GeV ± LEP2 l ± LEP2 χ g ) = g ) = OS Dilepton Multi-Lepton Lepton 2 [GeV] m No EWSB Non-Convergent RGE's D. Sprenger Searches for SUSY in events with di-leptons at CMS 6/4