Missing B-tracks in L1 trigger 13 April 2019 Federica Legger

Summary Motivations Method used L1 flow and main failures Breakdown for some representative channels Results A case study: Bd  p+ p- L1 failures correlation Origin of the decision tracks Status and plans 13 April 2019

Motivations Post-TDR study to better understand L1 behaviour LHCb trigger TDR (September 2003) TDR L1 efficiencies… or inefficiencies: why do we lose 37.3% of the events for Bd  p+ p- (easy channel)?? Some bugs corrected after TDR Post-TDR study to better understand L1 behaviour 13 April 2019

What I did…(I) Take some representative channels, and select events which pass L0 and the offline selection ( reconstructible), but that are rejected by L1 Hadronic Muon Electro magnetic 13 April 2019

…what I did… (II) Look for signal decay tree (MC Truth); Consider B daughter which is more likely to trigger: In the cases where there are more than one particle with the same probability to trigger (Bd  p+ p-), I consider the one with the highest Pt; Bd  p+ p- Bs  Ds k Bd  F Ks Bs  J/ (m+ m-) F Bs  J/ (e+ e-) F Bd  K* g 13 April 2019

…what I did (III) Associate MC particle to L1 2D and 3D tracks; Look what happened to signal track and see why it didn’t trigger; Classify events according to trigger failures; Study of L1 failures correlations in Bd  p+ p- (both pions taken in account). 13 April 2019

L1 flow (I) r z (r,z) plane Match L0 m to 2D tracks (2<16) VELO hits (r,z) plane z r NO 2D Reco YES 2D PV, IP2D Match L0 m to 2D tracks (2<16) IP2D cut .15 <IP2D< 3 mm NO NO Muon YES YES 3D Reco NO YES Track rejected 3D PV, IP3D 13 April 2019

L1 flow (II) m match to retrieve tracks for dimuon mass bonus (out of scope) Backward, Weird IP (-2<IP3D<5mm), IP3D cut (.15<IP3D<2mm) NO YES Match to TT or m (Pt) If not assign default 400 MeV/c PT, IPS One of the two highest Pt track (PT1 and PT2) Decision track NO YES Track rejected L1 Plane cut D > L1 equivalent 4% min. bias ret. D YES NO L1 YES L1 NO 13 April 2019

L1 code TDR baseline version + some bugs fixed (PVZ @ 100mm) No bonus system (dimuon mass, electron and g transverse energies) No multiple PV treatment (implemented in new L1 code) TDR now PVZ PVZ 13 April 2019

L1 flow (I) Main failures Lost@2D Lost@3D 1 2 VELO hits 2D Reco 2D PV, NO 2D Reco YES 2D PV, IP2D Lost@2D 1 IP2D cut .15 <IP2D< 3 mm NO NO Muon YES YES 3D Reco NO YES Lost@3D 2 Track rejected 3D PV, IP3D 13 April 2019

L1 flow (II) Main failures Lost@3D Low PT Small D 3 4 Backward, Weird IP (-2<IP3D<5mm), IP3D cut (.15<IP3D<2mm) NO YES Main failures PT, IPS Low PT 3 Decision track NO YES Track rejected L1 Plane cut D > L1 equivalent 4% min. bias ret. Small D 4 YES NO L1 YES L1 NO 13 April 2019

Main failures To be treated separately Main loss (~60%) ~10% ~10% ~15% Bd  p+ p- Bs  Ds K Bd  F Ks Bs  J/ (e+e-) F Bd  K* g 13 April 2019

2. Tracks lost at 2D B daughter MC truth Lost@2D IP2D cut Or Muon 2D track Correct Wrong 2. Tracks lost at 2D 13 April 2019

Tracks lost at 2D Absolute Relative Main loss ~20% OK Bd  p+ p- Bs  Ds K Bd  F Ks Bs  J/ (e+e-) F Bd  K* g 13 April 2019

3. Tracks lost at 3D B daughter MC truth Lost@2D IP2D cut Or Muon 2D track Correct Wrong Lost@3D IP3D cut 3D track 3. Tracks lost at 3D Correct Wrong 13 April 2019

Tracks lost at 3D Absolute Relative Main loss ~2% Bd  p+ p- Bs  Ds K Bd  F Ks Bs  J/ (e+e-) F Bd  K* g 13 April 2019

4. Tracks lost because of low Pt MC truth B daughter Lost@2D Low PT IP2D cut Or Muon Default Pt 400 MeV/c Measured low Pt 2D track Correct Wrong Correct Wrong Lost@3D 4. Tracks lost because of low Pt IP3D cut 3D track Correct Wrong 13 April 2019

Tracks lost because of low PT Absolute Relative Main loss (~10%) insignificant Bd  p+ p- Bs  Ds K Bd  F Ks Bs  J/ (e+e-) F Bd  K* g 13 April 2019

5. Tracks lost because of small D MC truth 5. Tracks lost because of small D B daughter Lost@2D Low PT IP2D cut Or Muon Default Pt 400 MeV/c Measured low Pt 2D track Correct Wrong Correct Wrong Lost@3D Small D IP3D cut 3D track PT1 PT2 Correct Wrong Correct Wrong Correct Wrong 13 April 2019

Tracks lost because of small D Correct > Wrong Correct < Wrong Almost 100% no measured Pt 13 April 2019

Tracks lost because of small D B track is more likely to be PT1 Bd  p+ p- Bs  Ds K Bd  F Ks Bs  J/ (e+e-) F Bd  K* g 13 April 2019

Summary for all channels but muons MC truth Summary for all channels but muons 60% B daughter 13% Lost@2D Low PT 12% 3% IP2D cut Or Muon Default Pt 400 MeV/c Measured low Pt 2D track 37% 20% 0% 1% 12% Correct Wrong 15% Correct Wrong Lost@3D Small D 10% IP3D cut 3D track PT1 PT2 1% 1% 10% 2% 2% 1% Correct Wrong Correct Wrong Correct Wrong 13 April 2019

L1 Design vs. Resolution failures (correct boxes) (wrong+failed) Best channel 50%, 50% Enhanced by bonus... Bd  p+ p- Bs  Ds K Bd  F Ks Bs  J/ (m+m-) F Bs  J/ (e+e-) F Bd  K* g 13 April 2019

Results (I) Main failure: Main loss at 3D: IP2D p+ IP2D e+ IP2D cut ~60%, wrong (40%) + correct (~20%) Main loss at 3D: failed 3D reco (~8%), worse than failed 2D reco (~3%), could also be the associator (MCParticle2L1Track) IP cut IP cut IP2D p+ IP2D e+ 13 April 2019

Results (II) IP3D cut not very significative (~2%) No decision track because Pt is too low (~10%): no measured Pt (~100%) failed TT reco Rejected decision tracks (~15%) : if PTMC we would gain ~5% of the evts. IP3D p+ IP3D e+ IP cut 13 April 2019

The muon channel L0 Muons (63%) go to 3D reco even if they do not pass the IP2D cut (73%) 10% evts lost at 2D (3% wrong) Main loss at 3D: IP3D cut (61%) 99% were L0 muons 13% evts wrongly rejected These tracks could be later use for dimuon mass bonus (out of scope) Low Pt tracks: 3% No decision track: 18% Worst design (71% vs. 29%) BONUS system 13 April 2019

A case study: Bd  p+ p- ! L1 failures Consider the two pions to study failures correlation ! L1 failures NO2D No 2D track NO3D No 3D track IP2D doesn’t pass IP2D cut and is not a m PT1 Leading track PT2 2nd leading track LOWPT Not one of the two leading tracks IP3D doesn’t pass IP3D cut 13 April 2019

A case study: Bd  p+ p- IP2D cut  Main loss is Even if other track is PT1!! 13 April 2019

Origin of the decision tracks Bd  p+ p- L0 && !L1 && SEL L0 && L1 && SEL 13 April 2019

PT1 PT2 L0 && !L1 && SEL L0 && L1 && SEL 13 April 2019

Status and plans Study completed; Note with full results almost ready; Write a Tool to automatically flag trigger failures and include it into new L1 code. 13 April 2019