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Jets and Missing Energy at CDF

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Information about Jets and Missing Energy at CDF

Published on January 17, 2009

Author: jgwacker

Source: slideshare.net

Description

Presentation for the CDF exotics group as a proposal to widen their Jets and Missing Energy searches
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Model Independent Searches for Jets + MET or Discovering Gluinos in an Uncertain Universe Jay Wacker SLAC CDF Exotics July 17, 2008 0803.0019 & work in progress with J. Alwall, M-P. Le, M. Lisanti

Outline Introduction Modules vs Models Model Independent Searches Projected Sensitivity Two Miscellaneous Items

High Energy Frontier No “sure thing” theory to discover Tevatron, Flavor, Precision EW, Higgs LHC may not burst into a superfire Many BSM possibilities to search for Supersymmetric Standard Model Universal Extra Dimensions Randall-Sundrum Little Higgs Different TeV scale physics, but similar signals Inverse problem hard Discovery first

Jets plus Missing Energy A common signature New Colored Particle Decays to WIMP Existing searches based upon MSSM ˜˜ ˜˜ ˜˜ gg qg qq Very general template to start from Can find SSM, UED, RS/LH w/ T-parity

Jets + Missing Energy Cuts at D0 1fb-1 analysis ˜˜ ˜˜ ˜˜ qg qq gg Gg 1j + ET 2j + ET 3j + ET 4j + ET ≥ 150 ≥ 35 ≥ 35 ≥ 35 ET j1 ≥ 35 ≥ 35 ≥ 35 ET j2 < 35 ≥ 35 ≥ 35 ET j3 < 35 < 35 ≥ 20 ET j4 < 20 < 20 < 20 ≥ 150 ≥ 225 ≥ 150 ≥ 100 ET ≥ 150 ≥ 300 ≥ 400 ≥ 300 HT (Not exclusive searches) T= HTable 1: Summary of the cuts used by DO ET j Will these discover anything visible in these channels? cascade into Standard Model particles plus some particles th

What a theorist knows about gluino limits DØ Preliminary, 0.96 fb-1 600 Squark Mass (GeV) Slepton & Chargino tan!=3, A =0, µ <0 0 CDF II limits 500 400 DØ IA UA1 UA2 CDF IB no mSUGRA solution 300 DØ IB 200 100 LEP 0 0 100 200 300 400 500 600 Gluino Mass (GeV)

mSugra is not representative of the MSSM mg : mB = 6 : 1 ˜ ˜ Anomaly Mediation Mirage Mediation non-Minimal Gauge Mediation Never varies decay kinematics Want a model independent search But first, a brief survey of models...

Outline Introduction Modules vs Models Model Independent Searches Projected Sensitivity Two Miscellaneous Items

˜˜ Examining g g more carefully “Modules” Minimal set of particles and interactions necessary to do a search over a class of models

˜˜ Examining g g more carefully “Modules” Minimal set of particles and interactions necessary to do a search over a class of models The minimal “gluino” module ˜ ¯˜ Turn on one decay mode g → q q χ0 Keep masses and total cross section free ˜˜ σ(p¯ → g g X) mg mχ p ˜ ˜

˜˜ Examining g g more carefully “Modules” Minimal set of particles and interactions necessary to do a search over a class of models The minimal “gluino” module ˜ ¯˜ Turn on one decay mode g → q q χ0 Keep masses and total cross section free ˜˜ σ(p¯ → g g X) mg mχ p ˜ ˜ Captures many models (MSSM, UED, etc) Misses heavy flavor and cascades

Where has the Tevatron probed “gluinos”? mSugra has focused on one mass ratio Q = mg − mχ ˜ ˜ Q=0 ˜ χ m = Q = mχ ˜ g ˜ m mχ ˜ mSugra mg ˜

Degenerate Search j1 j3 ˜ g ˜ ˜ B B ˜ g ET j2 j4 Useful when not phase space limited Q = mg − mB > mB ˜ ˜ ˜ If Q < mB ˜ Bino carries away energy but not momentum 1 As gluinos get boosted, jets become ∆Φ j ET ∼ collinear and ET aligned with jets γg ˜

Producing Degenerate Gluinos ˜ B ˜ j2 g j1 ET ˜ g j3 ˜ B Need additional hard jets Want the spectrum as well ET > 150 GeV j1 PT > 150 GeV D0 j2 PT < 50 GeV ∆ΦjET > 30◦ j1 PT > 150 GeV ET > 120 GeV CDF j2 PT < 60 GeV ∆Φj2ET > 0.3 j3 PT < 20 GeV

Searches useful in gluino searches Q=0 ˜ j ISR + ET χ m = Q = mχ ˜ g ˜ m mχ ˜ n j + ET mSugra mg ˜

Other modules ˜ ˜ q q → qχ 3 parameters ˜˜ ˜ ˜ ¯ qg q → qχ, g → q q χ 4 parameters ˜ g ˜ ¯ ¯ 5 parameters g → qqχ , χ → qqχ ˜ ˜ ˜ mSUGRA-like g→W →B ˜ g ˜ ¯ ¯ ¯ 9 parameters g → qqχ , χ → qqχ , χ → qqχ ˜ ˜ ˜ ˜ NMSSM-like g→W →B→S ...

For one cascade this is tractable 2 additional parameters from the minimal module mW Br(˜ → W ) g ˜ Know the results in the following limits Br(˜ → W ) → 0 g mW → mB ˜ ˜ mW → mg ˜ ˜ Ask “when does the cascade hurt the search the most?”

Outline Introduction Modules vs Models Model Independent Searches Projected Sensitivity Two Miscellaneous Items

Should be a better way of searching Don’t want to miss a visible signal Jets plus MET Searches are effectively: Jet classification criterion Visible Energy and Missing Energy Cuts As parameters in a module vary, visible and missing energy change dramatically

Exclusive Jets + MET Search 4 Separate Searches, Individually Optimized 1j + ET 2j + ET 3j + ET 4j + ET ≥ 150 ≥ 35 ≥ 35 ≥ 35 ET j1 ≥ 35 ≥ 35 ≥ 35 ET j2 < 35 ≥ 35 ≥ 35 ET j3 < 35 < 35 ≥ 20 ET j4 < 20 < 20 < 20 ≥ 150 ≥ 225 ≥ 150 ≥ 100 ET ≥ 150 ≥ 300 ≥ 400 ≥ 300 HT Table 1: Summary of the cuts used by DO Leave Free

One Proposal For each jet multiplicity d2 σ ∆HT ∆ET Set a limit on dHT dET e.g. 4 jets 800 < 5fb 5−2 fb < 2fb +2 600 10−3 fb +3 < 3fb HT < 10fb 400 < 20fb 10+8 fb < 5fb −8 200 100 200 300 400 ET

Backgrounds Want to vary cuts to maximize discovery potential Generate SM events and compare to D0 → → PGS Madgraph Pythia

Backgrounds Want to vary cuts to maximize discovery potential Generate SM events and compare to D0 → → PGS Madgraph Pythia Three Dominant Backgrounds W/Z + jets t tbar QCD Subdominant Backgrounds Diboson Single top

W/Z + jets Backgrounds Hit Z+jets to within QCD K-factors W+jets need a ~30% MET-independent scaling probably PGS efficiency at losing a lepton Top Background Worked at ~30% MET -independent level QCD Background No attempt to simulate ET > 100 GeV

Before HT ET cuts Very useful plot for theorists 2 jet analysis DØ Preliminary 4 10 Events / 20 Events / 5 Data W quot; l ! + jets 300 Z quot; !! + jets tt 103 WW,WZ,ZZ - Z quot; l + l + jets 250 single-t Signal 200 102 150 10 100 1 50 0 0 50 100 150 200 250 300 350 400 450 500 0 ET (GeV)

fb 4 fb−1 No QCD included

Outline Introduction Modules vs Models Model Independent Searches Projected Sensitivity Two Miscellaneous Items

Calculating Additional Jets Need additional radiation for signal Parton Showering Matrix Elements QCD Bremstrahlung Necessary for well-separated jets Soft/Collinear Approximation Includes quantum interference Resums large logs Fixed order calculation Computationally Cheap Computationally expensive Unlimited number of partons Limited number of partons Matching merges best of both worlds Necessary to avoid double counting

Calculating Additional Jets Matrix Elements g g 0j ˜˜ g g 1j ˜˜ g g 2j ˜˜ Parton Shower ve vet to oi if fp ve pT to T > Q > if cu Qc pT t ut > Qc ut g g 0j ˜˜ g g 1j ˜˜ g g 2j ˜˜ Decay g ∗ g ∗ 0j ˜˜ g ∗ g ∗ 1j ˜˜ g ∗ g ∗ 2j ˜˜

Comparison between Matching and Showering Ptjet1 in pp->gogo+jets by MadGraph/Pythia Matched contributions Cross section (pb/bin) 0-jet sample 1-jet sample 104 2-jet sample 0-jet+Pythia 0+1-jet inclusive 103 102 10 0 50 100 150 200 250 300 350 400 450 500 pT Ptjet1

First can try a cuts based search mg = 210 GeV mB = 100 GeV ˜ ˜ Dijet most effective channel but signal merges with QCD HT ≥ 150 GeV E T ≥ 100 GeV HT ≥ 225 GeV E T ≥ 300 GeV

fb 4 fb−1

Sensitivity plot for minimal gluino module for 4fb-1 250 S/B>0.3 200 Bino Mass GeV 150 mχ S/B>1 ˜ Out[991]= mSugra 100 X 50 0 100 200 300 400 500 Gluino Mass GeV mg ˜

Sensitivity plot for minimal gluino module for 4fb-1 Smaller HT , ET 250 200 Bino Mass GeV 150 mχ ˜ Out[991]= mSugra 100 X 50 0 100 200 300 400 500 Gluino Mass GeV mg Larger HT , ET ˜

Sensitivity plot for minimal gluino module for 4fb-1 250 200 Bino Mass GeV 150 mχ ˜ Out[991]= mSugra 100 X 50 0 100 200 300 400 500 Gluino Mass GeV mg ˜ 3 × σg σg /3 ˜ ˜

Sensitivity plot for minimal gluino module for 4fb-1 mg ∼ 160 GeV mg ∼ 130 GeV ˜ ˜ 250 200 Bino Mass GeV 150 mχ ˜ Out[991]= mSugra 100 X 50 0 100 200 300 400 500 Gluino Mass GeV mg ˜

Single Step Cascade ˜ ˜ ˜ g→W →B Most challenging point

Sensitivity of the Worst Case Scenario mg ∼ 120 GeV mg ∼ 130 GeV ˜ ˜ 150 Bino Mass GeV 100 Out[27]= X 50 0 100 200 300 400 500 Gluino Mass GeV

Outline Introduction Modules vs Models Model Independent Searches Projected Sensitivity Two Miscellaneous Items

Monophotons vs Monojets In degenerate limit ˜ ˜ ˜ ˜ g g g g g γ vs ¯ ¯ q q q q Trend moving to Monophoton searches Monojet rate is much larger for gluinos (gluinos radiate gluons, but not photons) Monojet discovery potential is significantly better

Leptons from Cascade Decays Lepton Rich Cascades ˜ q ˜ g Lots of constraints 2j ˜ from flavour on W squarks and sleptons ˜ ˜ B Leptons + Jets + MET very effective

Leptons from Cascade Decays Lepton Poor Cascades ˜ q ˜ g ˜ 2j ˜ W jj(70%) ν(30%) W± jj(70%) (10%) ˜ Z0 B Leptons + Jets + MET not nearly as effective

Have implicitly been assuming lepton poor cascades But, we’ve seen gluinos can be mg > 120 GeV ˜∼ σg ∼ O(100 pb)! ˜ O(400, 000) gluino pairs could have been produced Even lepton poor spectra can have lots of leptons σg ∼ 10 pb ˜ Lots of Hard Same Sign Dileptons ˜ g 200 GeV ˜ g2 2j ˜ 160 GeV W W + W − Z0 W ±Z 0 ˜ W+ B 80 GeV ˜ g1 W − Z0

We are probing the Energy Frontier Don’t know what we are looking for Models are just motivation Should strip models to their modules Leads to more model-independent searches Worst tragedy is to not discover a visible signal

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