SEARCHES FOR SUPERSYMMETRY IN EVENTS CONTAINING A Z BOSON, JETS AND MISSING TRANSVERSE MOMENTUM

Transcription

1 SEARCHES FOR SUPERSYMMETRY IN EVENTS CONTAINING A Z BOSON, JETS AND MISSING TRANSVERSE MOMENTUM NExT Workhop 9 April 05 Emma Kuwertz on behalf of the Collaboration Univerity of Victoria

2 Overview Preenting a earch for SUSY in final tate with a leptonically decaying Z boon, at leat two jet and miing tranvere energy (MET). R-parity conervation MET from ecaping LSP INTRODUCTION Quark from gluino and quark decay jet in the final tate tot [pb]: pp SUSY S = 8 TeV Recent reult from : earche wa fb - p, =8TeV - q g q q q q * - o + o g t t * g g Recent reult from CMS: earche wa p fb -, =8TeV -3 e e* l el e* m average 9/04/05

3 SUSY ignal cenario Analyi i optimied toward general gauge mediated SUSY model (GGM) Gravitino LSP Prompt higgino NLSP SIGNAL MODELS Max NLSP decay length mm g ) 0 GGM: higgino-like χ ; tan(β)=.5, M = M = TeV, q)=.5 TeV ZG ) BR(χ 0 g ) 0 GGM: higgino-like χ ; tan(β)=30, M = M = TeV, q)=.5 TeV ZG ) BR(χ µ µ 0.5 9/04/05 3

4 Event election At leat iolated lepton At leat jet ame-flavour oppoite-ign (SFOS) lepton with 8<m ll < GeV Scalar um of jet and lepton p T p T >35 GeV SIGNAL SELECTION On-Z ET mi H T n jet m`` SF/DF Region Signal region SR-Z > 5 > <m`` < SF Control region Seed region - > <m`` < SF CReµ > 5 > <m`` < DF CRT > 5 > 600 m`` / [8, ] SF Control region are ued for background etimation Validation region VRZ < 50 > <m`` < SF 50 5 > 500 m`` / [8, ] SF Z 50 5 > <m`` < SF Validation region are ued to check background etimate 9/04/05 4

5 Event election Check extrapolation Validation region Control region Signal region Meaure background SIGNAL SELECTION On-Z ET mi H T n jet m`` SF/DF Region Signal region SR-Z > 5 > <m`` < SF Control region Seed region - > <m`` < SF CReµ > 5 > <m`` < DF CRT > 5 > 600 m`` / [8, ] SF Validation region VRZ < 50 > <m`` < SF 50 5 > 500 m`` / [8, ] SF Z 50 5 > <m`` < SF 9/04/05 5

6 Background etimation overview Intrumental MET Dominant background Background Etimation method Generator Fake lepton: Multi-jet W lnu Z nunu Single top Matrix method - Matrix method - Matrix Method - DY/Z ll Jet mearing Sherpa ttbar Flavour-ymmetry Powheg+Pythia Powheg+Jimmy Alpgen Single top (Wt) Flavour-ymmetry Powheg+Pythia WW Flavour-ymmetry Powheg WZ MC Powheg+Pythia8 ZZ MC Powheg+Pythia8 tt+w, tt+ww, tt+z, t+z MC MadGraph+Pythia driven background MC background BACKGROUND ESTIMATION 9/04/05 6

7 Etimation trategy ttbar, Wt, WW, Z tautau Flavour ymmetric tt : µµ : µ = : : Z! tt µ µµ Electron-muon channel! ame-flavour channel : µµ : µ = : : Etimate in SF channel kee e-mu channel µµ = 9/04/05, = Neµ kee kee, kµµ = Neµ kµµ Recontruction efficiency cale factor kµµ = Almot excluively datadriven method Trigger efficiency cale factor Neµ kee = Neµ kµµ = kee =, kµµ = q 7 FLAVOUR-SYMMETRIC BACKGROUNDS Flavour-ymmetric background Z!

8 µµ = Recontruction = Neµ kµµ efficiency cale factor kee =, kµµ =, kµµ = q Ue the number of event elected in Z dominated event ample in data ee µµ Trigger efficiency = cale factor = q eµ Different channel ue different trigger! need to account for thi in efficiency correction ee µµ eµ MET eta Efficiency calculation checked Lepton pt HT 9/04/05 8 FLAVOUR SYMMETRIC BACKGROUNDS Neµ kee N Flavour-ymmetric background = = Neµ µµ kee Neµ kµµ

9 3 Not reviewed, for internal circulation only 3 CRT (HT > 600 GeV) SR-Z (HT > 600 GeV) SR-Z CRT Normalie ttbar MC(Hin Z ide band (HT > 600 GeV) T > 600 GeV) CRT (HT > 600 GeV) CRT (HT > 600 GeV) Alpgen+Pythia, Powheg+Pythia, Powheg +Jimmy mi mi cal region with intermediate ET (50 < ET < 5 GeV) and lightly looer HT requirement Z (HT > 500 GeV), a illutrated in Fig. 3. Here the (H (H (H T > 500 GeV) T > 500 GeV) T > 500 GeV) Z Cro check thi cro check uing extrapolation the ideband region `` between (HTin> m 500 GeV) (H (HT > 500 GeV) T > 500 GeV) identical region at lower MET () and the on-z region (Z) how conitent reult within approximately between data and the fitted prediction. mi 3 SR-Z ee SR-Z µµ Flavour-ymmetry - =8 TeV, 0.3 fb.8 ± ±.6 Flavour-ymmetry method alo checked! Event Event veru dilepton invariant ma plane of SR-Z, the control region CRT, and the two validation region ( and Z) ued to validate the ideband fit for the on-z earch. mi veru dilepton and Z lower HT threhold than CRT and SR-Z. Diagram indicating the poition in the ET invariant mahave plane of SR-Z, the control CRT, and the two validation region ( and Z) ued to validate the ideband fit for the on-z earch. nd Z have lower HT threhold than CRT and SR-Z. Signal region Fig. 3 Diagram indicating the poition in the ET =8 TeV, 0.3 fb - Sideband fit 4.9 ± ±.9 (Nob - Nexp) / σtot (Nob - Nexp) / σtot 4 ee+µµ ee µµ 0 - CRT - 9/04/05 (high HT) mi (high ET ) Total SM Z/ γ * + jet Other Background Z/ γ * + jet Other Background gion (SR-Z) uing the data-driven method baed on data in CReµ. Thi i compared with the prediction for reult from cro-check, the Conitent 4um of the flavour-ymmetric background (W W ee+µµ tw, Good tt and agreement Z! ) fromina validation ideband fit region to data eein µµ CRT. In each cae the combined tatitical and y0 tematic uncertaintie are indicated. Z-ma ide band Z-ma window Total SM Table 5 The number of event for the flavour ymmetric background etimate in the on-z ignal re- CRT Z-ma ide band Z-ma window 3 Z Z (high HT) Z mi (high ET ) (high HT) mi (high ET ) Z Z (high HT) Z mi (high ET ) Fig. 4 The oberved and expected yield in CRT and the VR in the Z boon ma ideband (left) and the Z boon ma window (right) region. The bottom plot how the di erence in tandard 9 deviation between the oberved and expected yield. The background due to W Z, ZZ or rare top procee, a well a from lepton fake, FLAVOUR SYMMETRIC BACKGROUNDS Side band fit

10 Jet mearing method No real MET in Z ll event Define a eed region well meaured jet low MET Z+JETS BACKGROUND Smear jet p T and phi with jet repone function Bulk tuned to data uing di-jet analyi Non-Gauian tail tuned to data uing 3-jet analyi MET Jet Peudo-data 9/04/05

11 Jet mearing Z+jet background Jet mearing teted on data in Z validation region Event / GeV = 8 TeV, 0.3 fb VRZ ee φ (jet mi,e, T ) > 0.4 Z+jet (Jet Smearing) Other Background Event / GeV = 8 TeV, 0.3 fb VRZ µµ φ (jet mi,e, T ) > 0.4 Z+jet (Jet Smearing) Other Background Z+JETS BACKGROUND MC cloure tet applying jet mearing to Z+jet MC / SM mi E T / SM mi E T Fig. Ditribution of ET mi in the electron (left) and muon (right) channel in VRZ of the on-z analyi following the requirement of (jet,,et mi) > 0.4. Here the Z/ +jet background (olid blue) i modelled uing p T -and -meared peudo-data event. The hatched uncertainty band include the tatitical uncertainty on the imulated event ample and the ytematic uncertainty on the jet-mearing etimate due to the jet repone function and the eed election. The background due to WZ, ZZ or rare top procee, a well a from lepton fake, are included under Other Background. Ue high tatitic Sherpa Z+jet MC to cro check data driven etimate Signal region Jet-mearing 766 which include WZ, ZZ, tz and t t +W (W )/Z Z+jet MC 767 procee, are taken directly from MC imulation. SR-Z ee 0.05 ± 0.04 Thi corrected number, N data,corr 768 eµ, i related to 0.05 ± the expected number in the ame-flavour chan- SR-Z µµ ± 0.05 nel, N et, by the following relation: ee/µµ k Reult are conitent ee = 9/04/05 et = N eµ data,corr = k ee, eµ, (3) trig k µµ = data (VRZ) data (VRZ), data (VRZ) data (VRZ), q ee trig µµ trig

12 Fake lepton Fake lepton background: lepton from heavy flavour decay, electron from photon converion, muon from meon decaying in flight, mi-identified hadron. The matrix method Analyi elect iolated lepton! remove iolation criteria q q Number of lepton failing iolation Single top W + N fake = N fail (/ real )N pa (/ fake / real ) t, b b l + ν l Only one true lepton Heavy flavour jet Number of lepton paing iolation FAKE LEPTON BACKGROUND Relative identification efficiency for fake lepton Relative identification efficiency for real lepton 9/04/05

13 -- -- Reult 8 Channel SR-Z ee SR-Z µµ SR-Z ame-flavour combined Oberved event Expected background event 4. ± ±..6 ± 3. Flavour-ymmetric background.8 ± ± ±.6 Z/ +jet (jet-mearing) 0.05 ± ± 0.05 Rare top 0.8 ± ± ± 0. WZ/ZZ diboon. ± ± ±.0 Fake lepton igma DOCUMENTATION An exce of event i oberved in the ignal region Table 7 Reult in the on-z SR (SR-Z). The flavour ymmetric, Z/ +jet and fake-lepton background component are all derived uing data-driven etimate decribed in the text. All other background are taken from MC imulation. The diplayed uncertaintie include the tatitical and ytematic uncertainty component combined and above-z region for SR-j-bveto, SR-4j-bveto, and SR-looe are preented in Table 8, 9, and, repectively. Correponding reult for SR-j- SR-Z ee btag and SR-4j-btag are preented in Appendix A. The data are conitent with the expected 8 SM Exce background more inapparent all region. in In the SR-looe re- 6 dielectron gion with 0 channel < m`` < 70 GeV, in which the CMS Collaboration oberved a.6 exce, 4 33 event are oberved, compared to an expectation of 90 ± 40 ± 70 event. Event /.5 GeV = 8 TeV, 0.3 fb - Other Background g),µ=(700,00)gev g),µ=(900,600)gev Event /.5 GeV - = 8 TeV, 0.3 fb SR-Z µµ Other Background g),µ=(700,00)gev g),µ=(900,600)gev m ll m ll / 5 GeV 9/04/05 E. Kuwertz - = 8 TeV, 0.3 fb - Z+jet+MET 3 = 8 TeV, 0.3 fb Other Background / 5 GeV - Other Background

14 Unblinded ditribution H T ditribution Event / 0 GeV = 8 TeV, 0.3 fb SR-Z ee Other Background g),µ=(700,00)gev g),µ=(900,600)gev Event / 0 GeV = 8 TeV, 0.3 fb SR-Z µµ Other Background g),µ=(700,00)gev g),µ=(900,600)gev RESULTS H T H T MET ditribution Event / 5 GeV - = 8 TeV, 0.3 fb 8 6 SR-Z ee Other Background g),µ=(700,00)gev g),µ=(900,600)gev Event / 5 GeV = 8 TeV, 0.3 fb SR-Z µµ Other Background g),µ=(700,00)gev g),µ=(900,600)gev mi E T mi E T 9/04/05 4

15 v CMS CMS earch: - x 3 SR binned in MET - No direct H T cut 0-00 GeV GeV 300+ GeV RESULTS Optimied for imilar ignal model MET CMS 3 CMS CMS H T 9/04/05 5

16 Excluion limit on GGM model Limit et on GGM model are weaker than expected RESULTS Exclude up to gluino) = 900 GeV and mu = 00 GeV Exclude up to gluino) = 850 GeV and mu = 900 GeV 9/04/05 6

17 Concluion and outlook earch for SUSY in final tate with a Z boon, jet and MET preented. A 3 igma deviation from the expectation wa oberved. SUMMARY CMS report good agreement with expectation in the ame final tate but phae pace cut are different. Something to look out for in Run II. Event 3 - =8 TeV, 0.3 fb Z-ma ide band Z-ma window Z/γ* + jet Other Background Total SM - N exp ) / σ tot 4 ee+µ µ ee µ µ 0 ob (N - CRT (high H ) T (high E mi T ) Z Z (high H ) T Z (high E mi T ) SR 9/04/05 7