PHENO 2010 Symposium — May 11, 2010 Isolated leptons from heavy flavor decays Theory and Data µ - /e - e - / µ - j µ - /e - W - P B P P Z b e + / µ + ν µ + /e + e + / µ + c e/ µ P b B P D P b B Zack Sullivan Illinois Institute of Technology Based on Z.S., E. Berger, hep-ph:1003.4997; and PRD 74 , 033008 (06); PRD 78 034030 (08). Zack Sullivan, Illinois Institute of Technology – p.1/14
Outline 1. The Motive • Dileptons: H → WW vs. leptons from heavy flavors at the LHC (ATLAS) • Trileptons: � χ ± χ 0 2 (The “Golden” SUSY channel) 1 � vs. leptons from heavy flavors at LHC (CMS) 2. The Physics • The underlying physics of isolated leptons from heavy flavors ( b/c ) ⇒ isolation is a band pass filter 3. The Evidence • Measurement of b ¯ b to isolated muons (CDF) 4. The Verdict • A new rule-of-thumb: 1 / 200 of all b/c look like µ or e Zack Sullivan, Illinois Institute of Technology – p.2/14
Dileptons and trileptons at LHC: Foil: H → WW Foil: χ ± 1 χ 0 2 Z.S., E. Berger, PRD 74, 033008 (2006); and PRD 78, 034030 (2008) Zack Sullivan, Illinois Institute of Technology – p.3/14
Higgs and SUSY — the main LHC searches! H → WW ∗ → l + l − / Common thread: E T Trilepton SUSY multi-leptons + / E T χ 0 ν 1 P W ν e + / µ + χ +- H P 1 W e - / µ - µ /e W P W e - / µ - ν Z P χ 0 2 e + / µ + Tevatron Run II Preliminary, L=2.0-5.4 fb -1 χ 0 95% CL Limit/SM 1 LEP Exclusion Tevatron Exclusion Expected Observed 10 10 ± 1 σ Expected ± 2 σ Expected 1 1 SM=1 November 6, 2009 100 110 120 130 140 150 160 170 180 190 200 m H (GeV/c 2 ) W. Vandelli, thesis CDF & D 0 / , hep-ex/0911.3930, 1001.4162 Experimentalist RULE of THUMB: All jet signals fake leptons at 10 − 4 . Is this really true? The real physical processes below do not matter? µ - /e - j e - / µ - µ - /e - W - P b B P P Z e + / µ + ν µ + /e + e + / µ + c P b B P D e/ µ P b B Zack Sullivan, Illinois Institute of Technology – p.4/14
Raise ut on additional leptons to p > 20 GeV T 2.5 H (160 GeV) W Z =� W W � t t CMS j � 2.0 W bX + W X + min. b b X bZ =� A TLAS 1.5 1.0 ll M for B redu ed 20 � T 0.5 H , W W � 2 = 3 original (fb/GeV) 0.0 60 80 100 120 140 160 180 200 ll M (GeV) T E = T T ll T E =d= =dM d� d� Isolated leptons from heavy flavors ( b/c ) Missing ba kgrounds for H ! W W at A TLAS in Higgs and SUSY at LHC 50 H (160 GeV) W Z =� 45 W W ( bZ =� )/5 � 40 Lo w er limit W bX + W X + min. b b X of missing B 1.0 35 H → WW ∗ → l + l − / 0.8 30 E T Trilepton SUSY 0.6 25 0.4 20 1.0 0.2 15 SUSY LM9 0.0 60 80 100 120 140 160 180 200 10 Z peak ll 0.8 M (GeV) T 5 ll (fb/GeV) (fb/GeV) (fb/GeV) 0 0.6 60 80 100 120 140 160 180 200 ll M (GeV) M T ll (GeV) =dM ll ll T T 0.4 =dM =dM d� d� d� 0.2 cut 0.0 0 20 40 60 80 100 120 Isolated leptons from b/c decay 10–50 × other backgrounds. Zack Sullivan, Illinois Institute of Technology – p.5/14
Isolated leptons from heavy flavors ( b/c ) Missing ba kgrounds for H ! W W at A TLAS in Higgs and SUSY at LHC 50 H (160 GeV) W Z =� 45 W W ( bZ =� )/5 � 40 Lo w er limit W bX + W X + min. b b X of missing B 1.0 35 H → WW ∗ → l + l − / 0.8 30 E T Trilepton SUSY 0.6 25 0.4 20 1.0 0.2 15 SUSY LM9 0.0 60 80 100 120 140 160 180 200 10 Z peak ll 0.8 M (GeV) T 5 ll (fb/GeV) (fb/GeV) (fb/GeV) 0 0.6 60 80 100 120 140 160 180 200 ll M (GeV) M T ll (GeV) =dM ll ll T T 0.4 =dM =dM d� d� d� 0.2 cut Raise ut on additional leptons to p > 20 GeV T 0.0 2.5 0 20 40 60 80 100 120 H (160 GeV) W Z =� W W � Isolated leptons from b/c decay 10–50 × other backgrounds. t t CMS j � 2.0 W bX + W X + min. b b X bZ =� A TLAS 1.5 Solutions 1.0 1.0 ll SUSY LM9 M for B redu ed 20 � T 0.5 H , W W � 2 = 3 original 0.8 (fb/GeV) T (fb/GeV) 0.0 60 80 100 120 140 160 180 200 0.6 ll M (GeV) T E = T (GeV) ll T E =d= =dM 0.4 d� d� 0.2 0.0 0 20 40 60 80 100 p T l 2 > 10 GeV ⇒ p T l 2 > 20 GeV Add / E T > 30 – 40 GeV, angular cuts b ¯ b → b ¯ b/ 30 ; S/B ∼ 1 ! bZ/γ → bZ/γ/ 40 ; S/B ∼ 1 / 2 ! Z.S., E. Berger, PRD 74, 033008 (06) Z.S., E. Berger, PRD 78, 034030 (08) Zack Sullivan, Illinois Institute of Technology – p.5/14
The physics of isolated leptons from heavy-flavor decays Z.S., E. Berger, PRD 78, 034030 (2008); and now arXiv:1003.4997 Zack Sullivan, Illinois Institute of Technology – p.6/14
b ! � p > 10 T � b ! � iso 6 p 10 T b b T =dp d� � iso � > 10 b � > 10 iso p T b Physics of isolated muons from b decay � > 10 GeV b Normalized Probability p T b (GeV) 10 15 20 25 30 35 40 45 50 Zack Sullivan, Illinois Institute of Technology – p.7/14
b ! � p > 10 T � b ! � iso 6 p 10 T b b T =dp d� Physics of isolated muons from b decay � iso � > 10 GeV b Normalized Probability � > 10 GeV iso p T b (GeV) 10 15 20 25 30 35 40 45 50 Prob. isolated muon = Prob. producing muon × Prob. B remnants missed • Muons that pass isolation take large fraction of p T • Many isolated muons point back to primary vertex. C. Wolfe, CDF internal • Isolation leaves ∼ 7 . 5 × 10 − 3 µ/b ≫ 10 − 4 per light jet Zack Sullivan, Illinois Institute of Technology – p.7/14
b ! � Physics of isolated muons from b decay p > 10 GeV T � � iso � > 10 GeV b b ! � iso 6 5 Normalized Probability 6 pb/GeV) � > 10 GeV iso 4 p p T b (GeV) b ( 10 T b (GeV) 3 T =dp 2 d� 1 0 10 15 20 25 30 35 40 45 50 10 15 20 25 30 35 40 45 50 Fold in b ¯ Prob. isolated muon b production. = Prob. producing muon Old focus: 1 / 2 of all 10 GeV × Prob. B remnants missed isolated µ come from threshold, • Muons that pass isolation take b with p T b < 20 GeV . large fraction of p T It is common for analyses to start simulations with p T b > 20 GeV . • Many isolated muons point New focus: Isolation acts as back to primary vertex. a narrow band-pass filter ! C. Wolfe, CDF internal • Isolation leaves ∼ 7 . 5 × 10 − 3 µ/b Isolated muons of a given energy ≫ 10 − 4 per light jet come from b s of barely more energy. Zack Sullivan, Illinois Institute of Technology – p.7/14
H W W ll M T ll T =dM d� Effect of isolation on H → WW → l + l − / E T Missing ba kgrounds for H ! W W at A TLAS 50 H (160 GeV) 45 Why does this new background have a hard right edge? W W � 40 Lo w er limit W bX + W X + min. b b X W j ! ( ej ) � of missing B 1.0 35 0.8 30 Why this? Why NOT this? 0.6 25 0.4 20 4 0.2 15 0.0 3.5 60 80 100 120 140 160 180 200 10 ll M (GeV) 3 T 5 T (pb/GeV) (fb/GeV) (fb/GeV) 2.5 0 lj 60 80 100 120 140 160 180 200 M 2 ll T (GeV) M (GeV) lj T =dM 1.5 ll T ll T =dM =dM d� 1 d� d� 0.5 0 60 80 100 120 140 160 180 200 Zack Sullivan, Illinois Institute of Technology – p.8/14
Effect of isolation on H → WW → l + l − / E T Missing ba kgrounds for H ! W W at A TLAS 50 H (160 GeV) 45 Why does this new background have a hard right edge? W W � 40 Lo w er limit W bX + W X + min. b b X W j ! ( ej ) � of missing B 1.0 35 0.8 30 Why this? Why NOT this? 0.6 25 0.4 20 4 0.2 15 0.0 3.5 60 80 100 120 140 160 180 200 10 ll M (GeV) 3 T 5 T (pb/GeV) (fb/GeV) (fb/GeV) 2.5 0 lj 60 80 100 120 140 160 180 200 M 2 ll T (GeV) M (GeV) lj T =dM 1.5 ll T ll T =dM =dM d� 1 d� d� 0.5 0 60 80 100 120 140 160 180 200 Answer: This is a direct consequence of the band-pass filter of isolation H (160 GeV) cutting off the high- p T leptons. W W Without the filter of isolation, the critical transverse mass distribution would be swamped by QCD background! 2.5 With isolation, the background to isolated µ (and e ) Heavy-flavor leptons 2.0 T (fb/GeV) from heavy flavor ( b and c ) decays is much softer. 1.5 ll M T (GeV) ll =dM The less well-modeled high- M T tail of the 1.0 d� background is suppressed. 0.5 0.0 60 80 100 120 140 160 180 200 Zack Sullivan, Illinois Institute of Technology – p.8/14
Dimuons from b ¯ b decays in the CDF data The foil: A Trilepton search at CDF , PRD 79, 052004 (09) Z.S., E. Berger, arXiv:1003.4997 Zack Sullivan, Illinois Institute of Technology – p.9/14
Searching the data — is this real? In our dilepton study (PRD 74 , 033008 (06)) we recommended measuring the production of isolated muons from b ¯ b production by varying isolation cuts to extract the µ iso fraction. Zack Sullivan, Illinois Institute of Technology – p.10/14
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