SUSY searches with the Jet Gamma Balance method in CMS

1. SUSY searches with the Jet Gamma Balance method in CMS Theodoros Geralis Institute of Nuclear and Particle Physics NCSR Demokritos, HEP2013, EESFYE, Chios Eleni Ntomari (PhD Thesis work), T.G., Kostas Theofilatos (ETH Zurich) 26 April 2013

2. Why SUperSYmmetry • Standard Model weknesses: • Hierarchy problem: large contributions to W, Z and Higgs masses from new physics at the Planck scale. • Distinct coupling constants:for Electromagnetic, Weak and Strong interactions • Non Unification of interactions • Too many papameters (19) - SUSY solves the hierarchy problem • One-loop quantum corrections in Higgs (mH2) mass from a Dirac Fermion (left) and from a scalar (right) from new physics at the Planck scale(ΛUV ~ Planck scale)

3. Why SUperSYmmetry • Solves the hierarchy problem by introducing a symmetry between fermions and bosons and doubling the number of particles fermion  boson • Possible unification of coupling constants at ~1016GeV H

4. Gauge Mediating SUSY breaking • Gauge mediation is used for the soft SUSY symmetry breaking in the MSSM (arXiv:0801.3278v3) • Gravitino is the LSP →experimental signature: Missing transverse energy (MET) • Neutralino is the NLSP • Work hypothesis is the R-parity conservation: two LSP's per event • Challenge: understanding the background 4

5. Whyγ+jets+ΜΕΤ; • Bino-like NLSP → decays to gravitinoκαι γ/Z • χ10 → γ+Gorχ10 → Z0+G J.T. Ruderman, D. Shlh ArXiV:1103.6083v1 ~ ~ ~ ~ Typical Feynman diagrmas for final states with (a) one or (b) two photons, as they are provided by GGM for the bino-like neutralino case 5 5 5

6. Whyγ+jets+ΜΕΤ; • Wino-like (co-)NLSP • Neutral winos: • χ10 → Z0+G ήχ10 → γ+G • Chargedwinos: • χ1±→ W±+G ~ ~ ~ ~ J.T. Ruderman, D. Shlh ArXiV:1103.6083v1 ~ ~ Typical Feynman diagrmas for final states with one photon as they are provided by GGM for the bino-like neutralino case Eleni Ntomari - NCSR Demokritos 6 6 6

7. Whyγ+jets+ΜΕΤ; • Photons are important ingredients in SUSY final states • We would like to exploit our sensitivity to detect Photons(Excellent detection, reconstruction efficiency and Energy resolution of the CMS ECAL detector: O(0.5%)) → clean experimental signature 7

8. ET γ e+ Tracker Strips Pixel detector pT Reconstruction of EM objects • Combine information from the Calorimeters and the tracking detectors • Superclusters of energy deposition in ECAL • Photons: equivalently low energy in HCAL • Tracks are reconstructed from their trace at the Si CMS tracker (pixel + strips) • Combines superclusters with tracks • Existence of track → electron • NO track → photon

9. Jet reconstruction • The Particle Flow algorithm is used for the evaluation of the missing transverse energy • It combines information from all the CMS subdetectors • It creates a list of Particle Flow objects • Photons, electrons, muons, charged & neutral hadrons • This list is used as input to jet algorithms (jet clustering) anti-kT • It provides the direction of the invisible particles like neutrinos and the lightest supersymmetric particles. →

10. Event selection • Photon (electron) selection criteria • At least one tight photon • pT > 80 GeV, for the most energetic photon • pT > 35 GeV, for the rest of the photons • |η|<1.4442 • Selection criteria ΗΤ • ΗΤ>460 GeV • ΗΤ:scalar sum of calo jets (CaloJets) withpT> 40 GeV, |η|≤3.0 • Jets selection criteria • At least 3 PF jets : • pT > 100 GeV, for the 3 most energetic jets • pT> 30 GeV, for the rest • |η| < 2.6 • Cut on the minimum distance between the selected photon and the jets ΔR=(Δη2+Δφ2)1/2<0.4 • *CombIso=EcalIso+HcalIso+TrackIso • Corrected for the pileup Seed crystal Ei: Energy of ith crystal Ε: Total energy in 5x5 crystals

11. SUSY signal and Standard Model background • SUSY signal : γ + jets + Gravitinos (MET) • Standard Model backgrounds: • Dominant background without missing transverse energy (MET) • QCD: γ + jets (fake MET because of the detector resolution) • Sub-dominant background: processes with true missing transverse energy (MET). • W(→eν) + jets, tt̄ + jets (with fe→γ) • SM Background simulation with MadGraphMonte Carlo samples • All simulated data (signal & SM background) are normalized to the total data integrated luminosity.They are used only for the evaluation of the method (MC Closure Test) Eleni Ntomari - NCSR Demokritos 4 11 11

12. Experimental Data samples • The data were recorded by the CMS detector during 2011, from proton proton collisions provided by the LHC accelerator at 7 TeV: • They correspond to 5.1 ± 0.1 fb-1 • Good quality data were used for this analysis (CMS data quality group) • Photon triggers were used with rather loose criteria • Presence of a photon with Energy above a threshold. • Thresholds are ajusted according to the luminosity in order to keep up with the trigger rates. • ET > 70 GeVandΗΤ>300 GeVfor the first runs (subsequently increased to ΗΤ>400GeV) • Criteria for Photon identification and isolation

13. The Jet Gamma Balance(JGB) variable pfJGB • The JGB method’s essentials: • Standard Model background processes mostly present a symmetric around zero JGB distribution. • Backgrounds: • γ + jets, W + jets, ttbar + jets • DY + jets , γV + jets • Supersymmetric processes with long decay chains tend to present non symmetric JGB distributions, with long tail tail in its positive side.

14. The Jet Gamma Balance(JGB) variable pfJGB • The JGB method’s essentials: • Standard Model background processes mostly present a symmetric around zero JGB distribution. • Backgrounds: • γ + jets, W + jets, ttbar + jets • DY + jets , γV + jets • Supersymmetric processes with long decay chains tend to present non symmetric JGB distributions, with long tail in its positive side. Control region

15. Standard Model background The SM background prediction is performed using real data (data driven), and is based on the Jet Gamma Balance variable distribution. (Jet-Gamma Balance, JGB) • The method is inspired from an equivalent analysis in SUSY final states to Z, jets and missing transverse energy where the balance between Jets and Z is used (Jet-Z Balance, JZB) • CMS Collaboration, “Search for physics beyond the standard model in events with a Z boson, jets, and missing transverse energy in pp collisions at sqrt(s) = 7 TeV” (2011) arXiv:1204.3774 15

16. Background calculation from electron misidentficatione→γ Background due to electron misidentification as a photon in Standard Model processes is estimatied using only data (data driven method). • Use Zee events in which one electron has a tight selection and the second is not required to have pixel hits. We thus estimate the electron identification efficiency.

17. Background calculation from electron misidentficatione→γ Background due to electron misidentification as a photon in Standard Model processes is estimatied using only data (data driven method). • Comparison of data events Z→ee with the corresponding Z→eγ • Misidentification rate is thus estimated To be : fe→γ~ 0.006 ± 0.003 • The background is calculated by reweighting Electron + Jet events by the above factor.

18. The JGB method • Twofold profit from JGB: • Event selection with JGB>0, rejects ~50% of the SM background while retains greatest part of the signal. • Estimation of the total background in the JGB >0 region, without being based in simulation. • Backgrounds with symmetric JGB: • JGB distribution for events with ≥1 photons and ≥3 jets • ”folding” the region with JGB<0 • Backgrounds with asymmetric JGB distribution: • JGB distribution for events with ≥1 electrons and ≥3 jets • Normalized using the electron misidentification rate fe→γ~ 0.006 ± 0.003(for pT>80GeV ) • ”folding” of the region with JGB<0 and subtraction from the region with JGB>0

19. JGB method validation withMC • Background Estimation as stated in the previous slide with MC data Background only hypothesis

20. JGBmethod capability to discover a signal • Repeat the previous exercise by adding a SUSY signal (msquark:750 GeV / mgluino:700 GeV / • mneutralino:225 GeV) in order to test the signal + background hypothesis and to prove the existence • of the signal Signal+Background hypothesis

21. Applying JGB on experimental data • The agreeement between Data and MC simulation events is good even though simulated events are not used for the background calculation. The leading photon Pt spectrum is shown for data and MC for the same integrated luminosity.

22. Applying JGB on experimental data • The JGB distribution for experimental data (black circles) and the corresponding estimated background (red line). The shaded surfaces represent the total uncertainty (left). The ratio of the two Is shown in the right plot.

23. Applying JGB on experimental data

24. Run= 176797, Lumi= 180, Event_Number= 282232912 η = 1.35238 Φ = -1.98983 pfJets #pfJets=5, #γ= 1, pfMET= 303.887, H/E= 0, σiηiη= 0.00759025, R9=0.857648, EcalIsoDR04= 2.695, HcalIsoDR04= 0.3708, TrkIsoDR04= 0 24 24 24 9/15/2014

25. Systematic uncertainties • Major sources of systematic errors are: • Luminosity • ±2.2% • Jet Energy Scale • ± 2% • Photon efficiency • ± 4 % • Acceptance PDF uncertainty • ± 0.03-78% (εξάρτηση από τις μάζες των SUSY σημάτων – αυξάνεται με την ταυτόχρονη αύξηση της μάζας των gluino και squark)

26. Exclusion limits • Eclusion limits at95% CLusing the JGB method and the isolation sideband analysis (SUS-12-001), for thebino-like (left, middle) andwino-like (right) neutralino • The limits estimation was performed using three bins:[80,100), [100,120) and [120,inf)

27. No SUSY signal detected in the final state γ + Jets + MET using the 2011 data at 7 TeV in CMS The measurement is compatible with the Standard Model We have set new more stringent limits on the parameter space More data at 8 TeV are available and are being analyzed The results are public and have been presented in major conferences Conclusions

28. Presentations: HadronCollider Physics Symposium 2012, Kyoto, Japan Invited talk on “Search for SUSY in final states with photons at CMS”, (speaker: Eleni Ntomari on behalf of CMS) LHC Days 2012, Split, Croatia Poster on “SUSY Search in Photon(s)+jets+MET final states with the Jet-Gamma Balance method in CMS”, (speaker: Eleni Ntomari on behalf of CMS) SUSY 2012, 20th International Conference on Supersymmetry and Unification of Fundamental Interactions, Peking, China Invited talk on “Searches for SUSY in final states with photons at CMS”, (speaker: KonstantinosTheofilatos on behalf of CMS) Documentation: [3] Eleni Ntomari, et. al CMS Collaboration, "SUSY Search in Photon(s)+jets+MET final state with the Jet-Gamma Balance method", CMS-PAS-SUS-12-013, (2012) [4] Eleni Ntomari on behalf of the CMS Collaboration, “Search for SUSY in final states with photons at CMS”, EPJ Web of conferences, DOI: TBA [5] Eleni Ntomari, TheodorosGeralis, KostantinosTheofilatos, "SUSY Searches in the Photon(s)+jets+MET final state in 7TeV pp collisions with the JGB method", CMS Internal Note AN/2012-180 Conclusions

29. This research has been co-financed by the European Union (European Social Fund – ESF) and Greek national funds through the Operational Program "Education and Lifelong Learning" of the National Strategic Reference Framework (NSRF) - Research Funding Program: Thales. Investing in knowledge society through the European Social Fund.