Hadronic Exotica Searches At CMS - INDICO-FNAL (Indico)

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Hadronic Exotica Searchesat CMSDinko FerenčekRutgers, The State University of New JerseyOn behalf of the CMS CollaborationSEARCH2012 WorkshopMarch 19, 2012College Park, Maryland

Introduction and Overview Hadronic final states are sensitive to many extensions of the standard modelAlthough experimentally challenging at hadron colliders, because of the strongproduction, hadronic final states provide an early discovery potentialI will talk about the following hadronic Exotica searches at CMS (I will presentthe latest publicly available results) Search for dijet resonances Search for dijet resonances with the dijet angular ratio Search for pair-produced dijet resonances Search for three-jet resonances Search for quark compositeness in dijet angular distributionsAll of the above searches dominated by a single source of background, the SM jet production I will not talk about Search for boosted tops in fully hadronic final state (presented by Petar) Search for black holes (presented by Alexey)SEARCH2012 - March 19, 2012Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)2

Search for Dijet Resonances(EXO-11-015) Ldt 1 fb-1Paper: Phys.Lett. B704 (2011) 123Preprint: arXiv:1107.4771Public TWiki: sicsResultsEXO11015SEARCH2012 - March 19, 2012Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)3

Dijet Resonances QCD predicts a smooth, steeply falling dijet mass spectrumMany extensions of the SM predict new massive objects producing resonantstructures (“bumps”) in the dijet mass spectrumThe following specific models of s-channel resonances considered: String resonances (S), E6 diquarks (D), excited quarks (q*), axigluons (A), colorons (C), heavygauge bosons (W' and Z'), RS gravitons (G)The main background for this search is the SM jet productionSEARCH2012 - March 19, 2012Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)4

Dijet Resonances (cont'd) Trigger: Using multijet HT trigger (HT ΣipT,i for all jets with pT 40 GeV) Requiring HT 550 GeV (99.9% efficient for Mjj 838 GeV)Jet reconstruction: Anti-kT (R 0.5 and R 0.7) particle-flow jets (calorimeterjets used as a cross-check)Energy-corrected AK5 PF jets combined into “wide jets”which are used to measure the dijet mass spectrumWide jets formed by adding all other AK5 jets withpT 10 GeV and η 2.5 to the closest leading jet if withinΔR 1.1Wide jets collect more of the final-stateradiation and improve the mass resolutionSEARCH2012 - March 19, 2012Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)5

Dijet Resonances (cont'd) Event selection: Two leading wide jets required to have η 2.5 and pseudorapidity separation Δη 1.3 Maximizes signal sensitivity for isotropic resonance decays in the presence of QCDbackgroundMjj 838 GeV (region with trigger efficiency 99.9%)Background modeling: A smooth function is fitted to the data No need for background Monte CarloFit function:χ2/ndf 27.5/28Inclusive dijet mass spectrum for pp 2 wide jets X,where X can be anything. Bin widths approximatelyequal dijet mass resolutionSmoothly falling distribution.No evidence for new particle productionSEARCH2012 - March 19, 2012Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)6

Dijet Resonances (cont'd) Signal modeling: Narrow resonances with the natural resonance width smallcompared to the CMS dijet mass resolutionSeparate resonance shapes for 3 different parton pairings: qq (or qq) (from PYTHIA6 G qq) qg (from PYTHIA6 q* qg) gg (from PYTHIA6 G gg)These shapes together with the data and the background fitused to set limitsDominant sources of systematic uncertainty: Jet energy scale Jet energy resolution Integrated luminosity Statistical uncertainty on the background fitSEARCH2012 - March 19, 2012Gaussian core from jet energyresolution and low mass tail fromQCD radiationHadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)7

Dijet Resonances (cont'd) Generic 95% CL upper limits are set on σ BR A Acceptance A refers to kinematic requirements η 2.5and Δη 1.3 (for isotropic decays, A 0.6)These limits can be compared to predictions ofσ BR A at the parton level of any model of dijetresonance productionMass limits for some of thebenchmark models consideredHighest dijet mass eventSEARCH2012 - March 19, 2012Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)8

Search for Resonances withthe Dijet Angular Ratio(EXO-11-026) Ldt 2.2 fb-1Public PAS: -026-pas.pdfPublic TWiki: /PhysicsResultsEXO11026SEARCH2012 - March 19, 2012Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)9

Dijet Angular Ratio Angular distribution of the two jets with the largest pT is sensitive to dijetresonances QCD jets tend to be produced at forward angles (due to the t-channel pole in the scatteringamplitude)Most models predicting new massive resonances decaying into dijets give essentially isotropicangular distributionsThis search uses the dijet angular ratioin different dijet mass bins to search for dijet resonances Complementary to searches using only the dijet mass spectrumThe main background is the SM jet productionSEARCH2012 - March 19, 2012Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)10

Dijet Angular Ratio (cont'd) Trigger: For each trigger threshold, a value of the dijet mass at which the trigger becomes fullyefficient is determinedJet reconstruction: Using single-jet triggers with varying thresholds on the jet pTAnti-kT (R 0.7) calorimeter jets with energy corrections appliedEvent selection: Two leading jets required to have η 2.5Selected event are classified as inner ifthe pseudorapidity separation of the twoleading jets Δη 1.3, and outer if1.3 Δη 3.0SEARCH2012 - March 19, 2012Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)11

Dijet Angular Ratio (cont'd) Signal and background modeling: Both signal and background modeled byPYTHIA6Background prediction normalized to data in a lowdijet mass sideband (500–600 GeV)Dominant sources of systematic uncertainty: Jet energy scale (in particular relative jet energyscale), integrated luminosity, backgroundmodelingData consistent with background expectationResults: SEARCH2012 - March 19, 2012Excited quarks with mass less than 3.2 TeV(2.85 TeV expected) excluded at 95% CLHadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)12

Search for Pair-ProducedDijet Resonances(EXO-11-016) Ldt 2.2 fb-1Public PAS: 016-pas.pdfPublic TWiki: sicsResultsEXO11016SEARCH2012 - March 19, 2012Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)13

Pair-Produced Dijet Resonances Dijet resonance searches generally more sensitive to singly-produced newparticlesThis search focuses on narrow colored resonances produced strongly in pairsand each decaying into a pair of jets Search performed in a paired dijet mass spectrum in events with at least 4 jets Paired dijet mass defined as the average of the two dijet masses Search results compared with a specific coloron model As with the dijet resonances, the main background is the SM multijet productionSEARCH2012 - March 19, 2012Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)14

Pair-Produced Dijet Resonances (cont'd) Trigger: Trigger fully efficient for events with 4 leading jets with pT 140 GeVJet reconstruction: HT 200 GeV (for 2010 data) and quadruple-jet trigger (for 2011 data) which requires4 jets with pT 70 GeVAnti-kT (R 0.5) particle-flow jets with energy corrections appliedEvent selection: 4 jets with η 2.5 and pT 150 GeV Create dijet combinations from the 4 leading jets by considering jet pairs with ΔRjj 0.7 Choose combination with the smallest Δm/mavg To additionally suppress QCD multijet background, require Δm/mavg 0.15 To ensure a smoothly-falling paired dijet mass spectrum, require Δ 25 GeV (see nextslide)SEARCH2012 - March 19, 2012Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)15

Pair-Produced Dijet Resonances (cont'd) Event selection (cont'd):Broad structure caused bythe applied selection cutsAcceptance varies from 3% for M(C) 300GeV to 13% for M(C) 1000 GeVSEARCH2012 - March 19, 2012Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)16

Pair-Produced Dijet Resonances (cont'd) Signal and background modeling: Signal samples produced using MadGraph withcolorons modeled as narrow dijet resonancesSignal shape modeled by a double GaussianBackground modeled by the same smooth function asin the dijet resonance searchDominant sources of systematic uncertainty: Jet energy scale, jet energy resolution, integratedluminosity, statistical uncertainty on the background fitSmoothly falling distribution.No evidence for new particle productionResults: SEARCH2012 - March 19, 2012Pair production of colorons with 320 M(C) 580 GeV(320 M(C) 650 GeV expected) excluded at 95% CLHadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)17

Search for Three-Jet Resonances(EXO-11-001) Ldt 35 pb-1Paper: Phys.Rev.Lett. 107 (2011) 101801Preprint: arXiv:1107.3084Public TWiki: sicsResultsEXO11001SEARCH2012 - March 19, 2012Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)18

Three-Jet Resonances New physics could be hiding in final states with more than 4 high-pT jetsThis search focuses on a pair production of massive colored resonances, eachdecaying into 3 jets, resulting in a 6-jet final state (pp QQ 3j 3j)One specific model of 3-jet resonances realized in RPV decays ofsupersymmetric gluinos to 3 quarks Event selection criteria optimized in the context of this model but generic enough to provide arobust model-independent basis for searches for other models of new physics producing similarfinal statesAs in all cases up to now, the main background is the SM multijet productionSEARCH2012 - March 19, 2012Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)19

Three-Jet Resonances (cont'd) Trigger: Jet reconstruction: HT trigger with thresholds varying between 100 and 150 GeV, depending on the runperiodAnti-kT (R 0.5) particle-flow jets with energy corrections appliedEvent selection: 6 jets with HT 425 GeV (this thresholdensures that the trigger is fully efficient)Jet pT 45 GeV and η 3.06 leading jets combined into all possibleunique triplet combinations 20combinationsTo increase signal sensitivity and reducecombinatorial background, requireAcceptance varies from 0.4% for 300 GeVgluino to 5% for 1000 GeV gluinoSEARCH2012 - March 19, 2012Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)20

Three-Jet Resonances (cont'd) Background modeling: Njet 6 triplet mass distribution described by anexponential function with the slope parameter P1constrained by the Njet 4 triplet mass distributionFit function:Signal modeling: Shape of the triplet mass distribution largelyunchanged between events with Njet 4 (or Njet 5) andNjet 6Signal samples simulated using PYTHIA6Gluinos modeled as narrow resonances and set todecay to 3 quarks through the λuds quark RPV couplingwith BR(g qqq) 100%Data consistent with background expectationDominant sources of systematic uncertainty: Jet energy scale, ISR/FSR, pile-up, choice of PDFs,integrated luminosityResults: Gluino masses in the range 200 to 280 GeV (200 to270 GeV expected) excluded at 95% CLSEARCH2012 - March 19, 2012Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)21

Search for Quark Compositeness inDijet Angular Distributions(EXO-11-017) Ldt 2.2 fb-1Preprint: arXiv:1202.5535Public TWiki: sicsResultsEXO11017SEARCH2012 - March 19, 2012Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)22

Dijet Angular Distributions In certain models of BSM physics, quarks are proposed to be composite objectsAt energies well bellow the compositeness scale Λ, compositeness manifested as a fourfermion contact interaction (CI)The following CI scenarios investigated qqΛ q qΛinterferenceΛ etween CI and QCDΛ-- Constructive interferenceΛ betweenConstructiveinterferenceCI and QCDbetween CI and QCDContact interactions resulting from the quark compositeness affect the angular distributionof the scattered partonsqθ*qqFlat for Rutherford scattering,approximately flat for QCD,peaking at low values of χdijet for CI modelsqSEARCH2012 - March 19, 2012Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)23

Dijet Angular Distributions (cont'd) Trigger: Jet reconstruction: Single-jet triggers with different pT thresholds (60, 80, 110, 150, 190, 240, and 300GeV). All except the last one prescaledAnti-kT (R 0.5) particle-flow jets with energy corrections appliedEvent selection: Require 2 jets with χdijet 16 and yboost 1.11 (effectively restricts y1 and y2 to 2.5)Angular distribution measured in multiple dijet mass bins with lower edges chosensuch that the trigger efficiency exceeds 99% (0.4, 0.6, 0.8, 1.0, 1.2, 1.5, 1.9, 2.4, and3.0 TeV) The first 5 bins correspond to 0.77, 5.9, 32, 108, and 371 pb-1. Only the last 4 binscorrespond to the full integrated luminosity of 2.2 fb-1SEARCH2012 - March 19, 2012Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)24

Dijet Angular Distributions (cont'd) Background modeling: Predictions at NLO obtained with NLOJET 2.0.1Correction factors applied to account for nonperturbativeeffects (obtained from PYTHIA6 and HERWIG )Signal modeling: Using LO (as implemented in PYTHIA8) and NLOpredictionsCorrection factors applied to account for nonperturbativeeffects Data unfolding: SEARCH2012 - March 19, 2012Data corrected for instrumentaleffectsUnfolding correction factorsobtained from PYTHIA6 andHERWIG Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)25

Dijet Angular Distributions (cont'd) 95% CL limits on Λ:Observed limits slightly higher than theexpected ones because of a downwardfluctuation at low χdijet for Mjj 3.0 TeVSEARCH2012 - March 19, 2012Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)26

Summary and Outlook Hadronic final states proved to be a fertile ground for searches fornew physicsMany results already made public, many new and updated resultsin the pipelineDespite our best efforts, the standard model is still alive and well An exciting year ahead of us Excluded a wide range of mass scales where new physics could have beenhidingHigher center-of-mass energy (8 TeV) sensitivity to higher mass scalesExpect at least 3 times more data than in 2011 more stringent crosssection limitsStay tuned!SEARCH2012 - March 19, 2012Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)27

Backup SlidesSEARCH2012 - March 19, 2012Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)28

CMS DetectorSEARCH2012 - March 19, 2012Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)29

CMS Trigger System CMS has a two-tiered trigger system: DetectorsLevel-1 (L1) trigger: Consists of custom-designed fast electronics Reduces event rate from 40 MHz to 100 kHzL1High-Level Trigger (HLT): Readout buffersConsists of a farm of commercially availableCPUs running reconstruction code optimizedfor fast processingReduces event rate from 100 kHz to O(100) HzSEARCH2012 - March 19, 2012Front end pipelinesSwitching networkHLTHadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)Processor farms30

Particle-flow Reconstruction Particle-flow algorithm reconstructs all stable particles by combining information fromall subdetectorsParticles categorized into the following 5 types: Muons, electrons (with associated bremsstrahlung photons), photons (includingconversion in the tracker volume), charged hadrons, neutral hadronsSEARCH2012 - March 19, 2012Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)31

Noise Cleanup To remove possible instrumental and non-collision backgrounds,events required To have a reconstructed primary vertex within z 24 cm and r 2 cm Jets passing identification criteria that is fully efficient for signal In paired dijet resonance analysis, events also required to pass HCALnoise cleanup criteriaSEARCH2012 - March 19, 2012Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)32

Jet Identification Criteria Calorimeter loose jet ID: Particle-flow loose jet ID:SEARCH2012 - March 19, 2012Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)33

Jet Energy CorrectionsSEARCH2012 - March 19, 2012Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)34

Jet pT ResolutionSEARCH2012 - March 19, 2012Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)35

Dijet ResonancesProperties of some resonance modelsarXiv:1110.5302SEARCH2012 - March 19, 2012Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)36

Dijet Resonances (cont'd)SEARCH2012 - March 19, 2012Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)37

Dijet Angular RatioSEARCH2012 - March 19, 2012Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)38

Pair-Produced Dijet ResonancesEnergetic 4-jet event passing event selectionSEARCH2012 - March 19, 2012Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)39

Dijet Angular DistributionsSEARCH2012 - March 19, 2012Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers)40

SEARCH2012 - March 19, 2012 Hadronic Exotica Searches at CMS (Dinko Ferenček, Rutgers) 2 Introduction and Overview Hadronic final states are sensitive to many extensions of the standard model Although experimentally challenging at hadron colliders, because of the strong production, hadronic final states provide an early discovery potential

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