Exotic Searches at CDF in Run II Tracey

Exotic Searches at CDF in Run II Tracey Pratt University of Liverpool Motivation for Exotic Searches Introduction to the Tevatron and CDF “Signature-Based” Model Searches - dielectron, dimuon, dijet, diphoton “Model-Based” Signature Searches - leptoquarks, excited e Conclusions and Outlook Tracey Pratt Durham Exotics Workshop April 2004

“Exotic” Physics : Why ? The SM describes experimental measurement very well, but raises crucial questions In the SM, EW symmetry breaking is responsible for giving rise to massive particles. The broken symmetry arises from a Higgs scalar field. Where/what is the Higgs boson ? Is it a fundamental scalar field? Or is the symmetry broken through a dynamical interaction ? technicolor (H→ q. T), topcolor Hierarchy problem MEW << MPl ? Supersymmetry Extra-dimensions Questions which the SM (or SM + SUSY) does not answer : • “Replication” of three families ? Compositeness ? Superstrings ? • Particle masses & their hierarchy ? Extra-dimensions ? Tracey Pratt Durham Exotics Workshop

Tevatron pp collider Highest energy collider operating in the world! CDF p p D 0 Run I (1992 -1996) s 1. 8 Te. V, 110/pb Run II (2001 -2009) s 1. 96 Te. V, Ldelivered ~400/pb Physics Analyses use ~ 200/pb taken between 03/02 and 09/03 Expect 2 /fb by 2006 and 4. 4 -8. 6 /fb by 2009 sensitivity to New Physics improved by>5 compared to Run 1 Tracey Pratt Durham Exotics Workshop

CDF at the Tevatron New for Run 2 Retained from Run 1 • Tracking System • Solenoidal magnet (1. 4 Tesla) • Silicon Vertex detector (SVX II) • Intermediate silicon layers (ISL) • Central Calorimeters • Central Outer tracker (COT) • Central Muon Detectors • Scintillating tile forward calorimeter • Intermediate muon detectors Muon System • Time-Of-Flight system • Front-end electronics (132 ns) Central • Trigger System (pipelined) Calorimeters • DAQ system Plug Calorimeter Solenoid Time-of-Flight COT Silicon Tracker Tracey Pratt Durham Exotics Workshop

“Signature-Based” Exotic Searches Why? How? initial signature motivated by some model apply same search results to several models • search for a particular signature • understand backgrounds • provide cross section limits: try to be as generic/model-independent as possible - study acceptance as a function of spin • interpret in context of specific models applicable to future models! Signatures? Tracey Pratt ee jj + ET Durham Exotics Workshop

Di-electron Production @ High Mass Search selection 2 opposite sign leptons: ee 2 central e (CC) 1 central and 1 forward e (CP) NEW: 2 forward e’s (PP) Good agreement with SM prediction Central Calorimeters Plug Calorimeter Tracey Pratt Durham Exotics Workshop

Model Independence Spin-dependent efficiency times acceptance To obtain cross-section limits: need efficiency times acceptance of detecting a particle decaying into a electron-positron pair as function of the mass. Angular distribution of decay particles depends on the spin of the particle. spin-0 Tracey Pratt spin-1 Durham Exotics Workshop spin-2

Model Independent σx. BR limits: spin-0, spin-1 and spin-2 particles spin-1 spin-0 spin-2 1 sigma error and 2 sigma error on the expected limit • Observed limit consistent with expectation • Applicable to any new possible future theory Tracey Pratt Durham Exotics Workshop

Interpretation of results: Specific Models • Observed limit consistent with SM expectation • Therefore set limits on new physics – Z' bosons – Little Higgs Z' – Technicolor – Randall-Sundrum graviton – Large Extra Dimensions Tracey Pratt Durham Exotics Workshop

Z' bosons Z' occurs naturally in extensions of SM towards GUT scale, e. g. “E 6” models – M(Z')>570 Ge. V for E 6 models (depends on exact model: couplings to quarks and leptons) – M(Z')>750 Ge. V for SM coupling (D 0 M(Z')>719 Ge. V, 122 pb-1) Z' Tracey Pratt Durham Exotics Workshop

Little Higgs Z` Tracey Pratt Durham Exotics Workshop

Technicolor q T , T q l+ l- Use Z` limit Tracey Pratt Durham Exotics Workshop

Randall-Sundrum graviton Extra Dimensional Model - 1 highly curved extra dimension - gravity localised in the ED q /Z l+ q l+ KKn l- q q ll+ g KKn g Planck Te. V brane Dilepton channel 10 -2 d /d. M (pb/Ge. V) 10 -4 10– 6 Tevatron 700 10 -8 Ge. V KK graviton Tracey Pratt l- 400 600 800 1000 K/MPl 1 0. 7 0. 5 0. 3 0. 2 0. 1 Ge. V Durham Exotics Workshop 500 Ge. V

Large Extra Dimensions Set a limit on the effective Planck scale in ADD type models Parameterise the cross section in terms of = / Ms 4 s = s. SM + s. INT + 2 s. KK Tracey Pratt Durham Exotics Workshop

Searches for New Physics in High Mass Dimuon Channel Search selection 2 isolated PT>20 Ge. V/c, | |<1 Cosmic ray rejection cuts Good agreement with SM prediction being updated with 200 pb-1 Tracey Pratt Durham Exotics Workshop

Dilepton: ee + 126 pb-1 results being updated with 200 pb-1 Tracey Pratt Durham Exotics Workshop

Run II dijet search at CDF Inclusive Jet samples 2 highest ET jets selected Highest mass event 1364 Ge. V/c 2 ET=633 Ge. V (corr) 546 Ge. V (raw) =-0. 30 (detector) =-0. 19 (correct z) ET=666 Ge. V (corr) 583 Ge. V (raw) =0. 31 (detector) =0. 43 (correct z) z z vertex = - 25 cm Tracey Pratt Durham Exotics Workshop

Dijet Limits 75 pb-1 • Fit the mass spectrum with a simple background parameterization and • Search for bumps comparable with our mass resolution. No significant evidence for a new particle Tracey Pratt Durham Exotics Workshop

Dijet Limits 75 pb-1 95% CL CDF Run I 200 and 980 Ge. V 200 and 570 Ge. V and 580 and 760 Ge. V 260 and 480 Ge. V 300 and 420 Ge. V 290 and 420 Ge. V Tracey Pratt Durham Exotics Workshop

Dijets Limits 75 pb-1 In Run 2 exclude Randall-Sundrum Gravitons with coupling k/Mpl=0. 3 between 220 and 840 Ge. V. The Randall-Sundrum model did not exist in Run 1. Tracey Pratt Durham Exotics Workshop

Run II diphoton search Search selection Isolated with ET > 13 Ge. V, | | < 0. 9 No 3 D tracks pointing to em cluster Main backgrounds fakes from -jet and jet-jet, where jet fragments into a hard 0 Results Highest mass event is: 168 Ge. V/c 2 Above 150 Ge. V/c 2: Observed 2 events Expected 3. 3 events No excess observed at high invariant mass Tracey Pratt Durham Exotics Workshop

Run II diphoton search ? Plan to set limits on new physics models: ADD, generic search… Tracey Pratt Durham Exotics Workshop RS,

E t Search Selection 91 pb-1 - One with ET > 47 Ge. V and | |<1 - Missing ET > 42 Ge. V - No jets with ET > 10 Ge. V - No tracks with p. T > 5 Ge. V Main backgrounds W e (“ “ ) 7. 9 1. 8 Z 0 + 5. 1 0. 5 Cosmic Ray Muons 4. 6 1. 1 1. 2 0. 4 W 1. 0 0. 3 Results Expected background: 19. 8 2. 3 Observed: 18 Tracey Pratt 95 % C. L. of 10. 1 events →A L = 110 fb-1 2. 0 times expected Z signal Durham Exotics Workshop

+ ET qq GKK Intrepret in terms of models predicting qq → X 1) Large Extra Dimensions 2) LSP Tracey Pratt Run I Limits (87 pb-1) n=4 MD > 0. 55 Te. V n=6 MD > 0. 58 Te. V n=8 MD > 0. 60 Te. V Durham Exotics Workshop

“Model-Based” Signature Searches • Perform search for a particular favourite Model • Search for a particular signature/s predicted by the model • excited electrons • leptoquarks Tracey Pratt Durham Exotics Workshop

Excited/exotic e Signature pp→ee*→ee Interpretation of limit Excited electrons are expected in many compositeness models. • Model 1: based on excited fermions coupling to quarks and leptons via contact interaction, described by an effective four-fermion Lagrangian (Baur, U. Phys Rev D 42, 3). • Model 2: excited electrons produced via gauge mediated interaction (Baur, U. Phys Rev D 42, 3). The cross section depends the e* mass and the compositeness scale, . Tracey Pratt Durham Exotics Workshop

Excited/exotic e Signature pp→ee*→ee There is very little background 3 candidate events 344 Ge. V e, 165 Ge. V e, 96 Ge. V , 73 Ge. V Tracey Pratt Durham Exotics Workshop

ee limits Contact Interaction Gauge Mediated Tracey Pratt Durham Exotics Workshop

Lepton + Quark Resonances: Leptoquarks LQs appear in many extensions of SM (compositeness, technicolor…) Additional symmetry/transition between leptons and quarks → Leptoquarks • have both lepton and baryon number • fractional em. charge: +-1/3, +-4/3, etc. • Branching Ratio unknown, convention: β=1 means 100% BR(LQ→l±q) β=0 means 100% BR(LQ→ q) Experimental Signature High pt isolated leptons (and/or ET) + jets Tracey Pratt Production qq → LQ LQ qg → LQ LQ gg → LQ LQ Decay LQ LQ → l+l-qq, l+/- qq, qq Durham Exotics Workshop e, u, d

Leptoquarks: 1 st generation Signature: jj (New in Run II) 2 jets and ET>60 Ge. V Result: 124 events observed 118. 3± 14. 5 events expected exclude LQ masses with 78<M<117 Ge. V β=0 Signature: eejj Result: M(LQ)>230 Ge. V for β=1 (72 pb-1) Signature: e jj Result: M(LQ)>166 Ge. V for β=0. 5 (72 pb-1) Tracey Pratt Durham Exotics Workshop

Leptoquarks: 2 nd generation • Signature – 2 high Pt muons – 2 high Et jets – Main background from /Z→μμ accompanied by jets due to radiation • Suppress Z→μμ background Expect 3± 1 events, observe 2 Exclude LQ’s M(LQ)<240 Ge. V Tracey Pratt Durham Exotics Workshop

Leptoquarks Competition between world’s accelerators: • HERA, LEP and Tevatron • At Tevatron: independent of coupling λ ee Tracey Pratt Durham Exotics Workshop

Conclusion and Outlook • Many Searches for New Physics have started – Now have twice the Run I luminosity – Signature- and Model-based searches being performed – Covering a broad range of possible signals – Many not in talk: monopoles, WIMPS, bb+ … – No signals yet but constraining theoretical models Many New Exciting Results coming soon! Tracey Pratt Durham Exotics Workshop

THE END! Tracey Pratt Durham Exotics Workshop