Jets and Missing at the LHC Jay Wacker SLAC BSM: Results from the 7 TeV LHC Nov. 9, 2011 w/ E. Izaguire D. Alves R. Essig J.Kaplan A. Hook M. Lisanti
Outline Simplified Models Two Examples Light Flavored Models Heavy Flavored Models Future Directions Stops High Multiplicity Searches Quark/Gluon Tagging
All started a few years back... Had an MSSM model that predicted a spectrum ... ˜ B q 140 GeV � W ¯ q ˜ q ∗ ˜ 80 GeV g 70 GeV ˜ B ˜ g
All started a few years back... Had an MSSM model that predicted a spectrum ... ˜ B q 140 GeV � W ¯ q ˜ q ∗ ˜ 80 GeV g 70 GeV ˜ B ˜ g Surely this must be excluded! The production cross section at the Tevatron is σ ( p ¯ p � ˜ g ˜ g ) � 2 nb
I went through the 25 years of squark and gluino searches They all came back to versions of this: -1 DØ Preliminary, 0.96 fb 600 mSUGRA Squark Mass (GeV) tan =3, A =0, <0 ! µ 0 (Five parameters to rule them all) CDF II 500 m 1 2 , m 0 , A 0 , tan β , sign µ m 1 2 → m ˜ 400 g DØ IA UA1 UA2 CDF IB no mSUGRA m 0 → m ˜ q solution 300 DØ IB 200 but where is B ? 100 m ˜ LEP 0 0 100 200 300 400 500 600 Gluino Mass (GeV)
mSugra has “Gaugino Mass Unification” g : m ˜ W : m ˜ B = α 3 : α 2 : α 1 � 6 : 2 : 1 m ˜ Most models look like this ˜ q ˜ g H ˜ H ˜ � � W ˜ B h A shocking lack of diversity (see the pMSSM)
Jets + MET Solution to Hierarchy Problem If the symmetry commutes with SU(3) C , new colored top partners (note twin Higgs exception) Dark Matter Wimp Miracle: DM a thermal relic if mass is 100 GeV to 1 TeV Usually requires a dark sector, frequently contains new colored particles Fewest requirements on spectroscopy Doesn’t require squeezing in additional states to decay chains
Spectrum in Different Theories Universal Extra Dimensions MSSM High Cut-Off Low Cut-Off Large Mass Splittings Small Mass Splittings g 2 Λ 2 g 2 δ m = δ m = 16 π 2 m log Λ 16 π 2 m g 1 ˜ g w 1 b 1 ˜ w ˜ b
Radiative Corrections to Kaluza-Klein Masses Cheng, Matchev, Schmaltz (2002)
Radiative Corrections to Kaluza-Klein Masses Cheng, Matchev, Schmaltz (2002)
Simplified Models Effective Field Theories for Collider Physics Limits of specific theories Only keep particles and couplings relevant for searches Still a full Lagrangian description Removes superfluous model parameters Masses, Cross Sections, Branching Ratios ( e.g. MARMOSET) Add in relevant modification to models ( e.g. singlets) Not fully model independent, but greatly reduce model dependence Captures specific models Including ones that aren’t explicitly proposed Easy to notice & explore kinematic limits
Simplified Models When an anomaly appears, we want evidence of discovery for each particle We want to know that we need χ ± , χ 0 g, ˜ ˜ but nothing else to explain the anomaly Then design searches to piece together the rest of the spectrum
Simplified Models Direct Decays MASS ˜ g color octet majorana THREE-BODY fermion (“Gluino”) q ¯ q χ 0 ˜ g 1 ˜ q ˜ χ neutral majorana fermion (“LSP”)
Tevatron Reach g > ∼ 120 GeV m ˜ Simplified Models showed a gap in Tevatron coverage 4 fb -1 2 σ sensitivity 150 Bino Mass � GeV ⇥ g → ˜ Bjj ˜ 100 X 50 g → � Wjj → ( ˜ ˜ Bjj ) jj 0 100 200 300 400 500 Gluino Mass � GeV ⇥ Alwall, Le, Lisanti, Wacker 2008
Important to keep the cross section free All searches at LHC are model dependent Easy to dilute signal with small branching ratios g → X )) 2 Rate ~ σ × (Br(˜ g → X ) ∼ 1 If Br(˜ 3 the rate drops by an order of magnitude If is a scalar, drops by ~1/6 ˜ g σ Dropping S/B by an order of magnitude dramatically changes discovery prospects
Putting it all together There could have been discoveries! LHC 70 nb -1 g → χ q ¯ ˜ q ! prod = 3 ! " NLO-QCD 100 pb ! prod = ! " NLO-QCD 200 pb ! prod = 0.3 ! " NLO-QCD 300 pb ! prod = 0.1 ! " NLO-QCD 500 pb Sample theory 1 nb Tevatron 2 nb mSUGRA
Much easier to interpret! m χ 0 = 50 GeV g = 800 GeV σ × Br ≤ 20 fb m ˜ m χ 0 = 600 GeV g = 800 GeV σ × Br ≤ 2 pb m ˜
Outline Simplified Models Two Examples Light Flavored Models Heavy Flavored Models Future Directions Stops High Multiplicity Searches Quark/Gluon Tagging
Light Flavored Simplified Models 4 Topologies Studied Based On Gluino Pair Production Light Flavored Squark Pair Production Not Studied Yet Squark Gluino Associated Production Not Studied Yet m ˜ q m ˜ g m ˜ γ m ˜ g m ˜ q q † ˜ ˜ ˜ ˜ ˜ ˜ ˜ ˜ ˜ ˜ q q g g g g g q q q g g g g g g q q g
Simplified Models Direct Decays MASS TWO-BODY ˜ g color octet majorana g fermion (“Gluino”) χ 0 ˜ g 1 THREE-BODY q ¯ q ˜ χ 0 χ ˜ g neutral majorana 1 ˜ q fermion (“LSP”)
Simplified Models One-Step Cascade Decays MASS q ¯ q ˜ W ( ∗ ) g color octet majorana fermion (“Gluino”) χ 0 ˜ g 1 ˜ χ 2 q χ ± ˜ electroweak majorana fermion (“Wino”) ( m ˜ g + m ˜ χ ) χ ± = m ˜ χ + r m ˜ ˜ χ r = 1 4 , 1 2 , 3 neutral majorana fermion (“LSP”) 4
Simplified Models Two-Step Cascade Decays MASS q ¯ W ( ∗ ) W ( ∗ ) q ˜ g color octet majorana fermion (“Gluino”) χ 0 ˜ g 1 ˜ χ 2 χ 3 q χ ± ˜ electroweak majorana fermion (“Wino”) χ � 1 ˜ neutral majorana ( m ˜ g + m ˜ χ ) χ ± = m ˜ χ + m ˜ fermion (“Higgsino”) 2 ˜ χ 1 neutral majorana ( m ˜ χ ± + m ˜ χ ) χ � = m ˜ χ + m ˜ fermion (“LSP”) 2
Hunting for Optimal Cuts Want to have good coverage for all these models for all kinematic ranges σ lim (cut) Want to minimize: σ optimal lim QUESTION : Is there a single cut whose sensitivity is close to optimal for all masses and decay modes? ANSWER : No
Hunting for Optimal Cuts TASK : Find the minimum set of cuts on MET and H T whose combined reach is close to optimal (within a given accuracy) for all models. σ lim cut 2 cut 1 σ opt 1 . 3 model space cut space 1 model space
⇥ Hunting for Optimal Cuts 47, MET > 150, H T > 750, 4j 47, MET > 150, H T > 750, 4j ˜ ˜ 2-body 3-body g g 800 800 E.g. , reach of the search region 600 600 m c H GeV L m c H GeV L ˜ ˜ � 150 GeV E T χ χ 400 400 & H T ≥ 750 GeV 200 200 0 0 200 400 600 800 200 400 600 800 443, MET > 150, H T > 750, 4 j 47, MET > 150, H T > 750, 4j é H GeV L m g é H GeV L m g ˜ g ˜ within 10% of optimal 800 800 g within 20% of optimal 600 600 m c H GeV L m c H GeV L ˜ ˜ χ χ within 30% of optimal 400 400 200 200 0 0 200 400 600 800 200 400 600 800 é H GeV L é H GeV L m g m g
Multiple Search Regions • minimal set of cuts ( multiple search regions ) whose combined reach is within optimal to a given accuracy for all masses and decay modes Set up a genetic algorithm to optimize search strategies • size of the set depends on the optimal accuracy ✦ 5% O ( 30 cuts ) ✦ 10% O ( 16 cuts ) ✦ 30% O ( 6 cuts ) ✦ 50% O ( 4 cuts ) • not sensitive to exact values of the cuts • only comprehensive when combined
combined reach � � � � � � within 30% of optimal Multiple Search Regions • 6 search regions necessary: Dijet high MET E T > 500 GeV , H T > 750 GeV E T > 450 GeV , H T > 500 GeV Trijet high MET E T > 100 GeV , H T > 450 GeV Multijet low MET E T > 150 GeV , H T > 950 GeV Multijet very high H T E T > 250 GeV , H T > 300 GeV Multijet moderate MET Multijet high MET E T > 350 GeV , H T > 600 GeV
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