Search for SUSY at CMS in lepton or photon final states. PANIC 2011 K. Theofilatos (on behalf of CMS)

Transcription

1 Search for SUSY at CMS in lepton or photon final states

2 CMS in one slide Optimal design for reconstructing leptons & photons Compact & precisely aligned detector with B=3.8 T Calorimeters operating inside the CMS Magnet Photon, Electron & Muon reconstruction: outstanding performance

3 SM re-discovery Good understanding of the detector performance already at 36 pb CMS simulation is better than expected Plethora of SM measurements already published by CMS In this talk, we are going to focus on SUSY search analyses searching for new physics beyond the SM 3

4 SUSY searches No need to motivate SUSY here, in simple words : We search for experimental evidence of an excess of events in the tail of the MET distribution Analysis challenge minimize B and its uncertainty while retaining high signal efficiency for a given event selection Leptonic SUSY searches: Less B and δβ BUT less inclusive compared to full-hadronic Might be capable to characterize a possible excess by probing the sparticles mass spectrum (SUSY spectroscopy) SUS1-011 beautiful CMS analysis 4

5 Snapshot of some analyses... single lepton multi lepton jets + MET Number of Events CMS preliminary 36 pb, s = 7 TeV tt + Jets W + Jets QCD single Top DY + Jets LM0 LM1 Data Events / 40 GeV 3 CMS Preliminary s=7 TeV! L dt = 35 pb HAD BOX DATA Total SM QCD W+jets Z+jets Top+X LM0 LM S MET opposite sign di-leptons Z+MET M R [GeV] γγ + MET updated with 1 fb updated with 1 fb Number of Events 4 CMS 36 pb 3 s = 7 TeV Data: γ γ (With Jet Requirement) Total BG (QCD shape from Z) Electroweak Background GGM: γ γ (With Jet Requirement) >0 GeV miss T Integral E (GeV) miss E T complete list at 5

6 Searching for an excess in the l + γ + ΜΕΤ final state SUS1-00

7 Search in l + γ + MET l+γ+met final state has very low background, predominantly SM Wγ production, a process which is well studied [1] Here we are interested in the MET tails of the Wγ background j j G g g q W 0 γ g example signal g q j W j W G l ν This kind of diagrams are predicted in general gauge mediated SUSY, where the Gravitino plays the role of the LSP, leaving the detector unseen [1] Measurement of Wγ and Zγ production in pp collisions at s = 7 TeV (EWK--008 accepted by PLB) 7

8 Background Estimation Wγ estimation: Madgraph interfaced Pythia NLO/LO WGRAD generator CTEQ6.6 NLO PDFs good agreement of the DATA with NLO predictions Events / 5 GeV miss-id lepton/γ estimation: control samples (DATA) MET modeling: Z ee (DATA) 1 CMS, 35 pb, s=7 TeV data expectation for GMC total bkg uncertainty W! MC l jet " l! l e " l! QCD Background uncertainties: Wγ cross section ~0% NLO in agreement with CMS cross section measurement PDF ~% (PDF4LHC procedure) Luminosity ~4% miss E T A benchmark signal is overlaid in the plot, but it s evident that DATA doesn t support its existence analysis set limits of GGM SUSY models (GeV) 8

9 Searching for an excess in the Z + Jets + ΜΕΤ final state SUS1-01 SUS--0

10 The Jet-Z-Balance Method Z+Jets+MET is a clean signature for discovering new physics events control region m(l l ) - 91 <0 GeV && njets CMS MC simulation s=7tev, L = 34 pb ZJets ttbar signal x 0 signal region SM Z+Jets: no genuine MET (rare mis-measurements) x σewk may give you sizable signal-like tails that we need to quantify JZB = Σ pt - pt (Z 0 ) jets JZB is ~equivalent with a signed ± MET for Z+jets events; the sign carries additional info! JZB [GeV] Signal is mostly positive, kinematic consequence (Z,LSP) common mother Z+Jets evenly populates JZB<0 and JZB>0 regions, JZB<0 region flipped gives a conservative estimate of the Z+Jets. The TTbar (W + W - ) background is estimated independently using an eµ pair data control sample.

11 MC Closure test SM B Analysis idea was tested for the first time with collision data in 0 (34pb ) events CMS MC simulation m(l l ) - 91 <0 GeV && njets s=7tev, L = 34 pb MC true B data-driven B JZB [GeV] Observed/Predicted CMS MC simulation MC closure test mean =0.97 ± m(l l ) - 91 <0 GeV && njets s=7tev, L = 34 pb +0% sys envelope ratio = 1 fit in [0,30] GeV -40% sys envelope JZB [GeV] MC of much higher equivalent luminosity was scaled down at 34 pb to assess the systematics via a complete SM MC closure test 11

12 MC Closure test S+B For data-driven analyses, it is of equal importance to perform a S+B hypothesis MC closure to demonstrate the loss of discovery potential events m(l l ) - 91 <0 GeV && njets CMS MC simulation s=7tev, L = 34 pb MC B + S signal 0 MC B data-driven B JZB [GeV] Observed/Predicted CMS MC simulation MC B+S closure test mean =0.97 ± m(l l ) - 91 <0 GeV && njets s=7tev, L = 34 pb +0% sys envelope ratio = 1 fit in [0,30] GeV -40% sys envelope JZB [GeV] A scaled msugra benchmark was used for this test: effect of signal contamination, compare red vs black dotted MC truth B 1

13 Application on the DATA Analysis successfully commissioned in 34 pb CMS data (SUS--0), here we show the update with 191 pb (SUS1-01) events 1 CMS preliminary 011 s=7tev, L = 191 pb observed (data) predicted (data) predicted fit (data) stat. uncert JZB (GeV) Observed/Predicted mean =0.99 ± 0.07 CMS preliminary 011 s=7tev, L = 191 pb +0% sys envelope ratio = 1 fit in [0,30] GeV -40% sys envelope JZB (GeV) The differential B prediction is in agreement (shape & absolute scale) with the observed event yield within stat and sys uncertainties. Null result was reported by this 191 pb 13

14 Searching for an excess in the Same Sign Di-Leptons channel SUS1-0

15 Same Sign Di-Leptons Very rare final state for Standard Model processes Low expected backgrounds Experimental backgrounds dominated by fake leptons (fake=non-prompt) from t-tbar, W+jets and QCD Many models including SUSY predict an increase of the Same Sign Di-Leptons event yield (e.g. UED, T5/3) Depending on model, expect hadronic activity and/or missing transverse energy in events This physics search uses all flavors of leptons including τ ± 15

16 Selection and Yields Select events with two isolated leptons of same charge Define signal regions with HT (scalar sum of Jet PT) and MET Depending on the trigger, different parts of phase space are covered, 0.98 fb of 7 TeV data analyzed (GeV) miss E T CMS Preliminary p (l /l ) > 0/ GeV T 1 = 976 pb L int. µµ ee eµ (GeV) miss E T CMS Preliminary p (µ/e/!) > 5//15 GeV T = 976 pb L int. µ! e!!! Search Region Search Region 1 Search Region Search Region 3 Search Region (GeV) Leptonic Triggers H T (GeV) H T Hadronic Triggers 16

17 B predictions (Baseline Sel) Fake leptons background is difficult to model in MC estimated with the Tight-To-Loose (TL) ratio method in DATA Probability for a Loose lepton (relaxed isolation, id) to pass the Tight selection is estimated in a control sample Charge mis-reco is controlled from Z->l ± l ± DATA with l=e,τ Events 0 80 CMS preliminary Data bkg prompt-fake bkg fake-fake bkg SS prompt-prompt bkg OS prompt-prompt s= 7 TeV, L =976 pb int Events CMS preliminary Data bkg prompt-fake bkg fake-fake bkg SS prompt-prompt bkg OS prompt-prompt s= 7 TeV, L =976 pb int ee µ µ eµ Total 0 e! µ!!! Total Leptonic Triggers Hadronic Triggers 17

18 Results (Signal Regions) All backgrounds involving fakes estimated from DATA Irreducible SM backgrounds are estimated from MC No excess is observed upper limits on new physics models CMS detector efficiencies are provided to allow testing of new physics models without the need of CMS full-sim software Events 14 1 CMS preliminary Data bkg prompt-fake bkg fake-fake bkg SS prompt-prompt bkg OS prompt-prompt s= 7 TeV, L =976 pb int Events CMS preliminary Data bkg prompt-fake bkg fake-fake bkg SS prompt-prompt bkg OS prompt-prompt s= 7 TeV, L =976 pb int H T >400 E T miss > H T >400 E T miss >50 H T >00 E T miss > Leptonic Triggers H T >80 E T miss >0 H T >400 E T miss > H T >400 E T miss >50 H T >00 E T miss > Hadronic Triggers!, H T >400 E T miss >1 18

19 Summary Detector is commissioned with well modeled performance Standard Model precision measurements are performed CMS is on track searching for new physics Luminosity rapidly increases sensitivity to new signals is enhanced (GeV) m 1/ % $ = LSP CMS preliminary " T LM1 Razor q~(500)gev q~(800)gev q~(650)gev OS Dilepton SS Dilepton " T +b-tag L Lepton+MET int = 36 pb, 36 pb tan! =, A 0 s = 7 TeV Jets+MHT g ~, q ~, tan!=5, µ<0 = 0, µ > 0 g ~ (650)GeV g ~ (500)GeV >1fb CDF D0 g ~, q ~, tan!=3, µ<0 ± LEP $ # 1 ~ g ~ ± (800)GeV LEP l m 0 (GeV) m 0 latest & greatest CMS results: 19

20 Backup Slides

21 Backup: SS and OS Di-Leptons OS Di-Leptons Analysis SS Di-Leptons Analysis 1

22 Backup: l+γ+met event yields e + γ channel µ + γ channel Observed event yields are in good agreement with the estimated background, no evidence of signal

23 Backup: l+γ+met exclusions squark / gluino mass (GeV) excluded by Tevatron CMS, 35 pb, s = 7 TeV observed 95% CL limit expected 95% CL limit GMC gluino NLSP wino mass (GeV) Limits on signal like General Gauge Mediated benchmarks 3

24 Backup:JZB for Signal In signal Z 0 is not produced promptly in the hard scatter LSP and Z 0 have common mother (angular correlation) jets Σ pt pt(z 0 ) MET Z 0 helps LSP to balance the jet system, results in large JZB when p*<pm pm = LAB momentum of Z 0 s mother p* = Z 0 momentum at its mother s rest frame 4

25 Backup: JZB for Background consider the simplest case: events with Z0 + 1 jet Z0 < > J (jet energy over measurement, JZB>0) Z0 <--- --> J (jet energy under measurement, JZB<0) J,Z0 are back-to-back giving MET = JZB JZB probes the jet energy response. Probability for under-measurement is greater due to energy losses Using JZB<0 flipped to model JZB>0 leads to systematic over-prediction in Z jet events (conservative if a discovery is to be claimed) 5

26 Backup:B Extraction (DATA) B prediction formula: events CMS preliminary 011 s=7tev, L = 191 pb Zjets tt WJets DiBosons SingleTop QCD events Same Flavor (SF) ee.or. µµ Opposite Flavor (ΟF) eµ CMS preliminary 011 s=7tev, L = 191 pb Zjets tt WJets DiBosons SingleTop QCD JZB (GeV) JZB (GeV) Di-Leptons (ee,µµ,eµ) pt>0 GeV, ask for the two highest pt leptons to be consistent with Z mass hypothesis and accompanied with 3 Jets (pt>30 GeV, η <3.0) 6

27 Backup: SSDL efficiencies LM6 SUSY benchmark point 7

28 Backup: SSDL efficiencies 8