Rochester Physics Analysis Activities on CMS

1. Rochester Physics Analysis Activities on CMS Henning Flächer for the Rochester CMS Group • Outline: • Physics Analysis Activities • Jet and METCommissioning • Dijet Resonances • Dijet Centrality Ratio • SUSY Multi-jet + MET Searches • Conclusions DOE Site Visit - 2nd Sep. 2010

2. Overview of Group Activities • Group Members • Analysis Preparation • Jet and Missing Energy (MET) Commissioning • Profit from groups hardware and detector commissioning experience • Hadron Calorimeter & Silicon Tracker • Calorimeter Noise Studies • Jet Reconstruction Performance and comparison of Jet algorithms • Jet Quality (Jet ID) • Jet based missing energy Studies (MHT) • Physics Analyses (early discovery) • Dijet Resonances • Dijet Centrality Ratio • Susy Multi-Jet and Missing Energy Search Henning Flaecher DOE Site Visit

3. CMS Physics Analysis Group • Teaching Faculty: • Demina (PI) • Bodek (PI) • Slattery (PI) • Melissinos (PI) • Garcia-Bellido • Postdocs: • Cammin ???(until Feb 09) • Chung • Flaecher • Gotra • Harel • Han • Goldenzweig • Senior Scientists: • Zielinski • de Barbaro • Sakumoto • Budd • Graduate students: • Miner • Orbaker??? • Betchart • Vishnevsky • Eshaq • Undergraduates: • Qi • Pedro • Moolekamp Henning Flaecher DOE Site Visit

4. Jet Commissioning: Algorithms • CMS Jet Algorithms group -- Zielinskia co-convener since 2007 • Jet algorithms define the procedure to cluster input objects: partons, particles, calo towers, tracks • We led algorithmic studies of jet performance and validation • Based on this work, in 2009 CMS adopted Anti-KT algorithm as the default jet reconstruction for LHC data • Hareldeveloped jet quality criteria for calorimeter jets • Reconstructing jets in calorimeter: • Cells contribute to tower energy if they pass energy thresholds • Current thresholds (Scheme 6) for CMS software developed with strong Rochester contributions (Zielinski,Qi) based on measurements of HCAL performance in Global Runs(Miner,de Barbaro, Vishnevsky) • New thresholds significantly improve performance of calorimeter jets with respect to old Scheme B • Implemented in RECO in fall of 2009, and in High Level Trigger in spring 2010 • Jet reconstruction using tracks under development(Garcia-Bellido, Eshaq) CMS AN-2010/024 CMS AN-2010/067, AN-2009/087, PAS JME-08-008 Henning Flaecher DOE Site Visit

5. Jet Performance at 7 TeV CMS AN-2010/121 PAS JME-10-003 • JME-10-003: “Jet Performance in pp Collisions at √s= 7 TeV” • Public CMS document for ICHEP • Based on Lint~75 nb-1 of 7 TeV data • Co-edited by Zielinski • Very broad range of jet performance studies • Jet energy corrections • MC-truth JEC • In-situ calibration: • Offset correction • Relative response • Absolute response • Jet resolutions • MC-truth Jet pT resolutions • Data-driven jet pT resolutions • Jet position resolutions • Relative jet responses and resolutions (Zielinski, Pedro, Garcia-Bellido) CMS AN-2010/134 PAS JME-10-003 Henning Flaecher DOE Site Visit

6. Jet Quality Criteria:Jet ID Harel • Brought JetID studies to publication as CMS Physics Analysis Papers: • Jet ID studies for early physics – PAS JME-09-008 • Jet commissioning note – PAS JME-10-001 • New study: Developed detailed Jet ID for the forward region • Only calorimetry information available • Noise samples collected with LHC operating, in empty bunch crossings • Adopted by analysers of forward jet production, e.g., CMS DP-2010/026 • Fully integrated with CMS reconstruction and analysis frameworks • Recommended by JetMET as CMS standard Simulated physical jets effective noise sample Analogue of EM fraction Loose Tight Selection Data from empty bunch crossings Optimized at each energy: entries normalized in each “x” slice Henning Flaecher DOE Site Visit

7. Demina, Flaecher, Betchart Missing Energy Commissioning • Missing energy performance in MinBias and dijet events • Co-edited by Flaecher • Rochester contribution • Commission missing energy inferred from jet measurements • Redundancy by comparing different approaches to jet reconstruction • HT and MHT distribution well behaved – no long tails • CMS approved documents: • JME-10-002 (0.9 & 2.36 TeV) JME-10-004 (7 TeV) Henning Flaecher DOE Site Visit

8. Phenomenology Connections: LPC and CTEQ • We are involved in CTEQ and LPC • LPC is a major USCMS center for analysis • We have trained many students at LPC (Demina, Zielinski) • CTEQ aims to provide guidance to LHC collaborations concerning Standard Model issues and backgrounds to searches for New Physics • Zielinskiis CTEQ member since 2006 and active at LPC since 2004 • On Organizing Committee for the first CTEQ Workshop on LHC Physics 2007 • Lecturing on jet issues at CTEQ Summer School 2007 • CTEQ-LPC liaison for the joint Workshop on Higgs Physics at LHC and Tevatron, 2009 • Co-organizer of the visit of several CTEQ members at LPC as part of the “Experimentalist/Theorist of the Week” program in March 2010 • On Organizing Committee for the workshop on “Standard Model Benchmarks at the Tevatron and LHC” – joint venue between the three CMS LPC’s, Argonne, and Fermilab in Nov 2010 Henning Flaecher DOE Site Visit

9. New Physics Searches at LHC Ratio of LHC/TeV Parton-Parton Lumi in pb • Rochester is involved in early discovery analyses • Dijet Resonances • Dijet Centrality Ratio • Susy Multi-Jet and Missing Energy Search • Jet Pairs and SUSY particles are expected to be produced via strong interaction in LHC • Production rates are large • Quickly surpass Tevatron sensitivity gg gq qq Henning Flaecher DOE Site Visit

10. Search for Dijet Resonances in Mjj • Heavy particles decaying to dijets could be observed as resonant peaks in the dijet mass spectrum • Such resonances are predicted by various theory models of physics beyond Standard Model • This approach complements the searches using the Dijet Centrality Ratio • Using the luminosity of836nb-1 CMS has established upper limits on the production of several resonance types at 7 TeV • In particular, we exclude a string resonance with mass M < 2.1 TeV at 95% CL – currently the best limit • We expect to exceed the Tevatron limits for other resonances with several pb-1 of data (Zielinski) CMS AN-2010/108 PAS EXO-10-010 Henning Flaecher DOE Site Visit

11. Dijet centrality ratio Harel, Miner Dijet angular distributions distinguish between: • Observable: • Measure as a function of dijet invariant mass • Simple measure of angular distribution • Robust with respect to systematic uncertainties t-channel s-channel production • Discovery observable for hadronic contact interactions • Sensitive to resonant dijetproduction Henning Flaecher DOE Site Visit

12. Harel, Miner Dijet centrality ratio measurement • Developed tools for the statistical analysis. • Test of QCD models • p-value of our consistency test statistic is 0.8 for corrected NLO and 0.7 for PythiaNLO/LO • Set CLS limits with an LLR observable • We exclude Λ<1.86TeV at 95% CL • Expected exclusion ~1.3TeV • Tevatron exclusion 2.8TeV • Will reach Tevatron limit with ~4pb-1 • Exclusion for a 500GeV q* resonance still only at ~90% CL PAS EXO-10-002 Henning Flaecher DOE Site Visit

13. Commissioning for SUperSYmmetry • SUSY signatures are challenging and involve multiple objects (jets, leptons, photons) accompanied by missing energy • SUSY events come from a variety of triggers • Good understanding of the detector and data flow is crucial for SUSY searches • SUSY Commissioning group was organized with this goal in mind • Demina was asked to co-lead this effort • Flaecher leading SUSY Prompt Validation Team. • Responsibilities involve: • Verification of the key variables (e.g. missing energy) using cosmic and early collision data • Defining triggers and data sets, ensuring efficient access to data • Prompt monitoring of variables relevant for SUSY searches • Established close coordination with detector performance and physics objects groups TRENDPLOT MET 95% Quantile Demina, Flaecher,Betchart Henning Flaecher DOE Site Visit

14. Demina Flaecher Betchart SUSY: Jets + Missing Energy Search • CMS SUSY group is organised based on signatures • Reference Analyses based on jets, leptons, photons • Rochester group’s focus is on: • Search for a missing energy signature in multi-jet events • Large sensitivity due to high cross section • Signal is evidence for a Dark Matter candidate (WIMP) • Production of WIMP in cascade decays of heavy new particles • WIMP escapes the detector and remains undetected => missing energy signature • WIMP candidate in many models: • SuperSymmetry, Extra Dimensions, Little Higgs, Technicolor • New approach to Jets + MET searches using kinematic variable αT • Fordijets: • ForMultijets: recombine jets to form dijet system • Main background: QCD events • For ideal QCD dijets: αT = 0.5 • For mismeasured QCD: αT < 0.5 • Approved CMS studies: • PAS-SUS-08/005, SUS-09-001, SUS-10-001 • Extension of PTRD-II studies to dijet topology • Analysis does not rely on calorimetric MET • MHT inferred from measured jets • well suited for early data Henning Flaecher DOE Site Visit

15. Demina Flaecher Betchart αT analysis with multi-jets • CMS SUSY Reference Analysis • Require and αT > 0.55 • Still clear separation of QCD from signal after jet recombination • αT cut value motivated by underlying physics • Expected event yields for selected benchmark signal points for 10 pb-1 @ 7 TeV • LM0/LM1: mSugra points beyond Tevatron reach • Signal/Background ~ 4 - 7 • Negligible contribution from QCD • αT edge stable under systematic variations (e.g. severe jet mismeasurements) • Improve on Tevatron with ~10pb-1, publication in 2010 dijet >=3 jets Henning Flaecher DOE Site Visit

16. Outlook on Sensitivity • αT Analysis: exceed Tevatron limits with 10pb-1 • Constraining Parameter Space of New Physics Models, e.g. SUSY • Simultaneous fit of CMSSM parameters m0, m1/2, A0, tanβ (μ>0) to more than 30 collider and cosmology data • Low energy data → Flavour physics, g-2 • High energy data → Precision EW Obs., MW, Mtop • Cosmology and Astroparticle data → relic density • Probe squark masses of ~600 GeV and gluino masses of > 500 GeV with 100 pb-1 • Probe squark masses of ~850-1000 GeV and gluino masses of ~600-900 GeV with 1 fb-1 • 1fb-1 by end of 2011 run • Complementary to direct Dark Matter Searches 5σ discovery 0% systematic 25% systematic 50% systematic L=10pb-1 1fb-1 100pb-1 MasterCode Collaboration – Flaecher et al. Henning Flaecher DOE Site Visit

17. More u quarks than d quarks in the proton. W asymmetry measures the d/u ratio at small x W/Z physics – W asymmetry Pt>10 GeVExpected error with 25 pb-1 Pt>20 GeV With 25 pb-1 our expected W asymmetry errors match PDF errors (4000 W’s per pb-1 ) Current CMS data as of July 21,2010: 78 nb-1 [Aug. 31, 2010 we have ~ 3 pb-1] So with 100 pb-1 (expected mid 2011), we can constrain d/u at small x and reduce PDF uncertainties at the LHC

18. Z/Drell-Yann Physics Z/DY physics : 340 Z dimuon events as of Aug.15, 2010. Z Mass distribution. W Transverse Mass distribution. We now have 340 Zs in 1 pb-1 of data (mu-mu channel) Note: Z cross section is factor of 10 smaller than W cross section. So need a factor of 10 more luminosity. For 1 fb-1 (end of 2011) we expect ~0.4 Million Z’s and ~4 Million W’s. 18

19. Z/DY Physics with 1fb-1(end of 2011) 2. Measure Z angular coefficients. We will have similar statistics as the Tevatron, so compare to theory and to CDF measurements at the Tevatron, and determine fraction of Compton vsq-qbar processes. Dilution for A4=3/8(Afb) different for different QCD Monte Carlos. ( 0.4 Million DY/Z’s and 4 Million W’s). 1. Compare Afb and dN/dM to SM expectation (y>1). LHC not yet competitive with Tevatron

20. Conclusions • Coherent physics programme building on hardware and algorithm expertise • Covering different aspects of early LHC physics: • Dijet Mass Distribution • Improved limit on String resonances with 120nb-1, excited quarks to follow soon • Dijet ratio • Sensitivity to Contact Interactions and Excited Quarks • Limit with 120nb-1, expect to surpass Tevatron limit with 4pb-1 • Electroweak Physics • test and constrain Parton Distribution Functions • Start to improve PDFs with >25pb-1 • Leading SUSY Commissioning Activities • developed good understanding of detector and Jet/MET quantities • Prompt monitoring of quantities relevant for SUSY searches • Leading role in multi-jet SUSY analysis • New approach using αT variable • “SUSY Reference Analysis” – targeted as first CMS SUSY publication with ~10pb-1 • Surpass Tevatron limits for many searches with O(10) pb-1 • Group is fully involved in 7 TeV data analysis! Henning Flaecher DOE Site Visit

21. BACKUP Henning Flaecher DOE Site Visit

22. Jet Studies for SUSY PAS JME-10-003 • One of the major backgrounds to SUSY searches in hadronic channels comes from mismeasured jets in QCD multi-jet events • Jet response distributions exhibit non-Gaussian tails due to detector effects and heavy flavor decays • This can lead to a large fake Missing ET • We are involved in • Determination of jet response distributions from CMS simulation • Development of data-driven method to measure response shapes from photon+jet events • Studies of various contributions to jet resolutions and their tails • Studies of the impact of jet resolution tails on Missing ET (Zielinski, Pedro, Garcia-Bellido) CMS AN-2010/151 Henning Flaecher DOE Site Visit

23. Search for Dijet Resonances in Mjj • Heavy particles decaying to dijets could be observed as resonant peaks in the dijet mass spectrum • Such resonances are predicted by various theory models of physics beyond Standard Model • This approach complements the searches using the Dijet Centrality Ratio • Using the luminosity of 120 nb-1 CMS has established upper limits on the production of several resonance types at 7 TeV • In particular, we exclude a string resonance with mass M < 1.67 TeV at 95% CL – currently the best limit • We expect to exceed the Tevatron limits for other resonances with several pb-1 of data (Zielinski) CMS AN-2010/108 PAS EXO-10-001 Henning Flaecher DOE Site Visit

24. A first look at systematics • To get a rough idea: • Jet energy scale variation by +- 10% for QCD MC • Data-MC agree within these uncertainties • More detailed studies to follow >=3 jets Henning Flaecher DOE Site Visit

25. Outlook on Sensitivity • Exceed Tevatron limits with 10pb-1 • 0% systematic • 25% systematic • 50% systematic L=10pb-1 • Probesquark masses of ~600 GeV and gluino masses of > 500 GeV with 100 pb-1 • Probe squark masses of ~850-1000 GeV and gluino masses of ~600-900 GeV with 1 fb-1 • 1fb-1 by end of 2011 run Henning Flaecher DOE Site Visit

26. Phenomenology:Constraining parameter spaceof MSSM JHEP 0809:117(2008), Eur.Phys.J.C64:391-415(2009), Phys.Rev.D 81,035009(2010) O.Buchmueller, R.Cavanaugh, A.DeRoeck, J.R.Ellis, H.F.,S.Heinemeyer, G.Isidori, K.A.Olive, P.Paradisi, F.J.Ronga, G.Weiglein • Combine as much experimental information as possible to constrain New Physics models! • Famous example: SM fit to electroweak precision data • Extend it to include New Physics models • Minimal SuperSymmetric Standard Model (MSSM) • What observables are used to constrain the model? • Low energy (precision) data → Flavour physics, g-2 • High energy (precision) data → Precision EW Obs. • Cosmology and Astroparticle data → relic density • Simultaneous fit of CMSSM parameters m0, m1/2, A0, tanβ (μ>0) to more than 30 collider and cosmology data • e.g. MW, Mtop, g-2, BR(B→Xγ), relic density σpSI: spin-independent dark matter - WIMP elastic scattering cross section on a free proton. 68% CL 95% CL “CMSSM fit clearly favors low-mass SUSY” WIMP Mass [GeV] Henning Flaecher DOE Site Visit