ATLAS Heavy Flavour production Looking towards Run 2 Heavy - PowerPoint PPT Presentation

ATLAS Heavy Flavour production 
 Looking towards Run 2 � � � Heavy Flavour at the LHC 
 IPPP Durham 21/4/2016 Josh McFayden

ATLAS Heavy Flavour production 
 Looking towards Run 2 into � � Heavy Flavour at the LHC 
 IPPP Durham 21/4/2016 Josh McFayden

Overview � Chiara already showed some of the Run 1 results and 
 HF-related issues that were discovered. � � I will show a few more recent results and prospects as we get further into Run 2: � � A new Run 1 measurement on inclusive di-bjet production � � MC generator setups for Run 2 � � Some early Run 2 results that are a ff ected by HF production � � Prospects for better HF production measurements in the future 3 Josh McFayden | HF @ LHC | 21/4/2016

Hot o ff the press 4 Josh McFayden | MC performance | 21/05/2015 Josh McFayden | HF @ LHC | 21/4/2016

7 TeV bb di-jet cross section � New 7 TeV ATLAS result on di-b-jet production. � One jet with p T > 270 GeV required due to trigger. � b-jets with p T > 20 GeV and ∆ R = 0.4. � Template fit used to extract true b-b contribution. � m bb step at ~500 GeV due to “turn-on” of flavour creation. STDM-2013-03 5 Josh McFayden | HF @ LHC | 21/4/2016

7 TeV bb di-jet cross section � New 7 TeV ATLAS result on di-b-jet production. � One jet with p T > 270 GeV required due to trigger. � b-jets with p T > 20 GeV and ∆ R = 0.4. � Template fit used to extract true b-b contribution. � Large ΔΦ region is dominated by flavour creation and underestimated by NLO predictions. STDM-2013-03 6 Josh McFayden | HF @ LHC | 21/4/2016

What does it tell us? � These results use the same dataset… � How much do we learn about V+HF from inclusive di-b-jets? � Seems like trends might be di ff erent? � Is the large leading jet requirement good/bad? 0.3 [pb] Data ATLAS Z+ ≥ 2 b-jets a -1 s = 7 TeV, 4.6 fb R(b,b) MCFM (Zbb) 0.25 aMC@NLO 5FNS aMC@NLO 4FNS ALPGEN+HJ σ ∆ 0.2 SHERPA d d 0.15 0.1 0.05 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 Data NLO 1 0.5 LO multileg 1.2 1 Data 0.8 0.6 0.4 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 R(b,b) ∆ 7 Josh McFayden | HF @ LHC | 21/4/2016

Generator setups for Run 2 8 Josh McFayden | MC performance | 21/05/2015 Josh McFayden | HF @ LHC | 21/4/2016

Generators for Run 2 Flavour Matrix Slicing/ Generator number Comments Element filtering scheme NLO@2j Known mismodelling Sherpa2.1 5fl pT(V) & HF LO@4j of low pT large η jets NLO@2j Improvement in low Sherpa2.2 5fl pT(V) & HF LO@4j pT large η jets Mismodelling of jet pT MG+Py8 A LO@4j 5fl N-parton (too hard) NLO PDF, di fg erent MG+Py8 B LO@4j 5fl HT & HF shower settings. (still too hard) MG5_aMC+Py8 Very promising - some NLO@2j 5fl TBD FxFx N-jets mismodelling N-parton & 
 The new old! HFOR Alpgen LO@5j 4fl b/c/light can be problematic. 9 Josh McFayden | HF @ LHC | 21/4/2016

7TeV vs 13TeV | Z+jets � What appears to be ~small slope at 7 TeV seems to becomes much more significant at 13 TeV. � Important to make new measurements at 13 TeV. 7 TeV - ratio wrt data 13 TeV - ratio wrt Sherpa2.1 Transverse momentum of 1 st jet 10 1 Transverse momentum of 1 st jet d σ /d p ⊥ [pb/GeV] d σ /d p ⊥ [pb/GeV] ATLAS data, √ s = 7 TeV Sherpa 2 . 1 1 Sherpa 2 . 1 MG+Py 8 A 1 Sherpa 2 . 2 MG+Py 8 B 10 − 1 ATLAS simulation preliminary, √ s = 13 TeV MG+Py 8 A 10 − 1 MG+Py 8 B 10 − 2 aMC@NLO FxFx 10 − 2 10 − 3 10 − 3 10 − 4 Ratio to Sherpa 2 . 1 1 . 4 1 . 4 MC/Data 1 . 2 1 . 2 1 1 0 . 8 0 . 8 0 . 6 0 . 6 100 200 300 400 500 600 700 100 200 300 400 500 600 700 p ⊥ ( 1 st jet) [GeV] p ⊥ ( 1 st jet) [GeV] ATL-PHYS-PUB-2016-003 10 Josh McFayden | HF @ LHC | 21/4/2016

Looking back… � 7 TeV VH( → bb) analysis saw large mismodelling of Δφ (j,j) and discrepancies between generators in m(j,j). � Di ff erence between Sherpa and Alpgen � Are in a better position with our Run 2 generators setups? Events / 5 GeV rad 80000 ATLAS ATLAS Data 2012 -2 VH(bb) ( =1.0) 25000 s = 8 TeV µ s = 8 TeV 70000 x10 ∫ Diboson ∫ -1 -1 L dt = 20.3 fb L dt = 20.3 fb t t π 60000 Single top Events / 20000 Data 2012 VH(bb) ( =1.0) µ Multijet 50000 Diboson t t W+hf Single top Multijet W+cl 15000 40000 W+hf W+cl W+l W+l Z+hf Z+hf Z+cl Z+l 30000 Z+cl 10000 Z+l 20000 5000 10000 Data / Pred Data / Pred 0 50 100 150 200 250 0 0.5 1 1.5 2 2.5 3 1.1 1.1 1 1 0.9 0.9 0 50 100 150 200 250 0 0.5 1 1.5 2 2.5 3 W p [GeV] (jet ,jet ) ∆ φ 1 2 T JHEP01(2015)069 11 Josh McFayden | HF @ LHC | 21/4/2016

7TeV vs 13TeV | Z+jets � Some systematic di ff erence between Sherpa and MG5_aMC+Py8 CKKW-L � The data sits between the two. � The modelling seems to be improved but much less data. 7 TeV - ratio wrt data 13 TeV - ratio wrt Sherpa2.1 Azimuthal distance of leading jets d σ /d | ∆ φ | [pb] d σ /d | ∆ φ | [pb] ATLAS data, √ s =7 TeV Sherpa 2 . 1 Sherpa 2.1 MG+Py 8 A 10 1 Sherpa 2.2 MG+Py 8 B ATLAS simulation preliminary, √ s = 13 TeV MG5 aMC+Py8 CKKW-L A MG5 aMC+Py8 CKKW-L B MG5 aMC+Py8 FxFx 10 1 1 Ratio to Sherpa 2 . 1 1.4 1 . 4 1.2 1 . 2 MC/Data 1 1 0.8 0 . 8 0.6 0 . 6 0 0.5 1 1.5 2 2.5 3 0 0 . 5 1 1 . 5 2 2 . 5 3 | ∆ φ | (1st jet, 2nd jet) | ∆ φ | ( 1 st jet, 2 nd jet) ATL-PHYS-PUB-2016-003 12 Josh McFayden | HF @ LHC | 21/4/2016

7TeV vs 13TeV | Z+jets � Some systematic di ff erence between Sherpa and MG5_aMC+Py8 CKKW-L � The data seems to prefer the MG5_aMC+Py8 CKKW-L shape. 7 TeV - ratio wrt data 13 TeV - ratio wrt Sherpa2.1 Invariant mass of leading jets d σ /d m [pb/GeV] d σ /d m [pb/GeV] 10 − 1 ATLAS data, √ s =7 TeV Sherpa 2 . 1 Sherpa 2.1 MG+Py 8 A 10 − 1 Sherpa 2.2 MG+Py 8 B ATLAS simulation preliminary, √ s = 13 TeV MG5 aMC+Py8 CKKW-L A 10 − 2 MG5 aMC+Py8 CKKW-L B MG5 aMC+Py8 FxFx 10 − 2 10 − 3 Ratio to Sherpa 2 . 1 1.4 1 . 4 1.2 1 . 2 MC/Data 1 1 0.8 0 . 8 0.6 0 . 6 0 200 400 600 800 1000 0 200 400 600 800 1000 m (1st jet, 2nd jet) [GeV] m ( 1 st jet, 2 nd jet) [GeV] ATL-PHYS-PUB-2016-003 13 Josh McFayden | HF @ LHC | 21/4/2016

7TeV vs 13TeV | Z+b(b) � Main di ff erence between Sherpa2.1 and MG5_aMC CKKW-L is in the rate � From early analyses we see that the data seems to prefer the higher rate. � Shape deviations are more important. 7 TeV - ratio wrt data 13 TeV - ratio wrt Sherpa2.1 Z + ≥ 1 b-jet 1 d σ ( Zb ) / d p T /N b -jets [pb/GeV] d σ ( Zb ) /d p T / N b -jets [pb/GeV] ATLAS data, √ s =7 TeV 10 − 1 Sherpa 2.1 Sherpa 2.2 10 − 1 MG5 aMC+Py8 CKKW-L A 10 − 2 MG5 aMC+Py8 CKKW-L B MG5 aMC+Py8 FxFx 10 − 2 10 − 3 Sherpa 2 . 1 MG+Py 8 A MG+Py 8 B 10 − 4 10 − 3 ATLAS simulation preliminary, √ s = 13 TeV Ratio to Sherpa 2 . 1 1.4 1 . 4 1.2 1 . 2 MC/Data 1 1 0.8 0 . 8 0.6 0 . 6 10 2 10 2 b -jet p T b -jet p T ATL-PHYS-PUB-2016-003 14 Josh McFayden | HF @ LHC | 21/4/2016

7TeV vs 13TeV | Z+b(b) � Perhaps larger di ff erences observed at 7 TeV than 13 TeV. � We have enough data to constrain the MC prediction here. � Improvement by going to NLO. 7 TeV - ratio wrt data 13 TeV - ratio wrt Sherpa2.1 Z + ≥ 1 b-jet, p T ( Z ) > 20 GeV d σ ( Zb ) / d ∆ φ ( Z, b ) /N b -jets [pb] d σ ( Zb ) /d ∆ φ ( Z , b ) / N b -jets [pb] 10 1 ATLAS data, √ s =7 TeV Sherpa 2 . 1 Sherpa 2.1 MG+Py 8 A Sherpa 2.2 MG+Py 8 B ATLAS simulation preliminary, √ s = 13 TeV MG5 aMC+Py8 CKKW-L A 10 1 MG5 aMC+Py8 CKKW-L B MG5 aMC+Py8 FxFx 1 1 Ratio to Sherpa 2 . 1 1.4 1 . 4 1.2 1 . 2 MC/Data 1 1 0.8 0 . 8 0.6 0 . 6 0 0.5 1 1.5 2 2.5 3 0 0 . 5 1 1 . 5 2 2 . 5 3 ∆ φ ( Z, b ) ∆ φ ( Z , b ) ATL-PHYS-PUB-2016-003 15 Josh McFayden | HF @ LHC | 21/4/2016

7TeV vs 13TeV | Z+b(b) � The familiar plot… � Systematic shape di ff erences observed � Sherpa seems to do a better job of modelling the shape of the low Δ R(b,b) region. 7 TeV - ratio wrt data 13 TeV - ratio wrt Sherpa2.1 Z + ≥ 2 b-jets d σ ( Zbb ) / d ∆ R ( b, b ) [pb] d σ ( Zbb ) /d ∆ R ( b , b ) [pb] 0.4 Sherpa 2 . 1 1 ATLAS data, √ s =7 TeV MG+Py 8 A 0.35 Sherpa 2.1 MG+Py 8 B ATLAS simulation preliminary, √ s = 13 TeV Sherpa 2.2 0 . 8 0.3 MG5 aMC+Py8 CKKW-L A 0.25 MG5 aMC+Py8 CKKW-L B 0 . 6 MG5 aMC+Py8 FxFx 0.2 0 . 4 0.15 0.1 0 . 2 0.05 0 0 Ratio to Sherpa 2 . 1 1.4 1 . 4 1.2 1 . 2 MC/Data 1 1 0.8 0 . 8 0.6 0 . 6 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 0 . 5 1 1 . 5 2 2 . 5 3 3 . 5 4 4 . 5 5 ∆ R ( b, b ) ∆ R ( b , b ) ATL-PHYS-PUB-2016-003 16 Josh McFayden | HF @ LHC | 21/4/2016

7TeV vs 13TeV | Z+b(b) � Sherpa ~flat in m(b,b), some shape deviation from other 7 TeV - ratio wrt data 13 TeV - ratio wrt Sherpa2.1 Z + ≥ 2 b-jets 10 − 2 d σ ( Zbb ) / d m ( b, b ) [pb/GeV] d σ ( Zbb ) /d m ( b , b ) [pb/GeV] ATLAS data, √ s =7 TeV Sherpa 2 . 1 Sherpa 2.1 MG+Py 8 A Sherpa 2.2 MG+Py 8 B 10 − 2 ATLAS simulation preliminary, √ s = 13 TeV MG5 aMC+Py8 CKKW-L A MG5 aMC+Py8 CKKW-L B MG5 aMC+Py8 FxFx 10 − 3 10 − 3 Ratio to Sherpa 2 . 1 1.4 1 . 4 1.2 1 . 2 MC/Data 1 1 0.8 0 . 8 0.6 0 . 6 50 100 150 200 250 300 350 50 100 150 200 250 300 350 m ( b, b ) [GeV] m ( b , b ) [GeV] ATL-PHYS-PUB-2016-003 17 Josh McFayden | HF @ LHC | 21/4/2016