Introduction to pixel track isolation • The purpose of track isolation algorithm is an additional improvement of level-1 pixel trigger performance. • Procedure of pixel track isolation • Reconstructed pixel tracks using kinematic parameters step 0 : Finding z vertex ( 𝑨 𝑤𝑢𝑦 ) of L1 EG based on the level-1 pixel trigger algorithm step 1 : Select pixel cluster (cl) satisfying Δ𝑆 < 0.3 cone step 2 : Measure a distance ( Δ𝑨 ) from 𝑨 𝑤𝑢𝑦 to z intercept calculated from two pixel clusters step 3 : Measure ∆𝜃 𝑑𝑚1,𝑑𝑚2 of pixel track segments step 4 : Measure ∆𝜃 𝑤𝑓𝑠𝑢𝑓𝑦, 𝑑𝑚 of pixel track segments step 5 : Measure ∆𝜚 difference of pixel track segments • Estimation of pixel track 𝑞 𝑈 using ∆𝜚 • Calculation of isolation based on the estimated 𝑞 𝑈 1 Jongho Lee (KNU) KPS, 24 - 26 Oct 2018
Simulation framework • Phase 2 simulation framework CMSSW_10_1_7 : the same as the level-1 pixel trigger algorithm • Sample used for track isolation studies Signal windows for pixel track reconstruction in step 0 ~ step 5 SingleMuon without pile-up /SingleMu_Pt2t200_Eta3p0_NOPU_93X_upgrade2023-realistic_v5_D17/GEN-SIM-DIGI-RAW Efficiency of pixel track isolation algorithm SingleElectron with <PU>=200 /SingleE_FlatPt-2to100/PhaseIIFall17D-L1TPU200_93X_upgrade2023_realistic_v5-v1/GEN-SIM-DIGI-RAW Rate reduction factor calculation for pixel track isolation algorithm Minimum Bias sample with <PU>=200 /SingleNeutrino/PhaseIIFall17D-L1TPU200_93X_upgrade2023_realistic_v5-v1/GEN-SIM-DIGI-RAW 2 Jongho Lee (KNU) KPS, 24 - 26 Oct 2018
Finding vertex of L1 𝒇/𝜹 object with pixel clusters • Almost one pixel track from electron candidate found by the level-1 pixel based track trigger algorithm • The z vertex of L1 EG ( 𝑨 𝑤𝑢𝑦 ) is reconstructed by extrapolation of straight line to beam axis using two pixel clusters on the pixel track from the level-1 pixel trigger algorithm 𝑨 𝑤𝑢𝑦 t ested with gen level 𝑨 𝑓𝑜−𝑚𝑓𝑤𝑓𝑚 ∶ 𝑨 𝑤𝑢𝑦 − 𝑨 𝑓𝑜−𝑚𝑓𝑤𝑓𝑚 Sample: SingleElectron + <PU>=200 Region 1 ( 𝟏 < 𝜽 < 𝟏. 𝟗 ) Region 3 ( 𝟐. 𝟓 < 𝜽 < 𝟐. 𝟖 ) Region 6 ( 𝟑. 𝟖 < 𝜽 < 𝟒. 𝟏 ) 25 𝝂𝒏 58 𝝂𝒏 472 𝝂𝒏 3 Jongho Lee (KNU) KPS, 24 - 26 Oct 2018
Track isolation: step 1 & 2 ( ∆𝑺, ∆𝒜 ) • Required ∆𝑆 < 0.3 to every pixel clusters in each pixel layer for electron direction. • Pixel clusters along L1 𝑓/𝛿 direction are selected with 2 + Δ𝜃 𝑀1 𝑓/𝛿, 𝑞𝑗𝑦𝑓𝑚 2 < 0.3 ∆𝑆 = Δ𝜚 𝑀1 𝑓/𝛿, 𝑞𝑗𝑦𝑓𝑚 r-axis • Measuring Δ𝑨 which is distance electron between L1 𝑓/𝛿 vertex ( 𝑨 𝑤𝑢𝑦 ) and z-intercept of pixel track segments. ∆𝑨 Layer2 Δ𝑨 = 𝑨 𝑤𝑢𝑦 − 𝑨 𝑑𝑚 1 , 𝑑𝑚 2 Layer 1 z-axis 𝑨 𝑑𝑚 1 , 𝑑𝑚 2 𝑨 𝑤𝑢𝑦 4 Jongho Lee (KNU) KPS, 24 - 26 Oct 2018
Track isolation: step 3 ( ∆𝜃 𝑑𝑚1,𝑑𝑚2 ) ∆𝜃 𝑑𝑚 1 , 𝑑𝑚 2 is a longitudinal angle difference in r-z plane between pixel track • segments. • The electron signal track can be selected by ∆𝜃 𝑑𝑚 1 , 𝑑𝑚 2 cut requirements. • Combinatorial background can be removed by the minimum ∆𝜃 𝑑𝑚 1 , 𝑑𝑚 2 requirements. ∆𝜽 𝒅𝒎 𝟐 , 𝒅𝒎 𝟑 = 𝜽 𝑴 𝒋 , 𝑴 𝒌 − 𝜽 𝑴 𝒌 , 𝑴 𝒍 r-axis Electron Combinatorial signal background Example of signal window Layer 4 ∆𝜃 Layer 3 Layer 2 Layer 1 z-axis 5 Jongho Lee (KNU) KPS, 24 - 26 Oct 2018
Track isolation: step 4 ( ∆𝜃 𝑨 𝑤𝑢𝑦 , 𝑑𝑚 ) ∆𝜃 𝑨 𝑤𝑢𝑦 , 𝑑𝑚 is a longitudinal angle difference in r-z plane between vectors • from L1 𝑓/𝛿 vertex to pixel clusters. Δ𝜃 distribution for signal electron track is very narrow. • one of powerful background rejection parameters ∆𝜽 𝒜 𝒘𝒖𝒚 , 𝒅𝒎 = 𝜽 𝒜 𝒘𝒖𝒚 , 𝑴 𝒋 − 𝜽 𝒜 𝒘𝒖𝒚 , 𝑴 𝒌 r-axis Layer 3 Example of signal window 𝜽(𝒜 𝒘𝒖𝒚 , 𝑴𝟒) Layer 2 𝜽 (𝒜 𝒘𝒖𝒚 , 𝑴𝟑) ∆𝜽 = 𝜽 𝒜 𝒘𝒖𝒚 , 𝑴𝟒 − 𝜽 (𝒜 𝒘𝒖𝒚 , 𝑴𝟑) Layer 1 𝜽 (𝒜 𝒘𝒖𝒚 , 𝑴𝟐) z-axis 𝑨 𝑤𝑢𝑦 6 Jongho Lee (KNU) KPS, 24 - 26 Oct 2018
Track isolation: step 5 ( 𝛦𝜚 difference) • 𝛦𝜚 difference ( ∆𝜚 12 − ∆𝜚 23 ) 𝜠𝝔 𝟐𝟑 = 𝝔 𝟐 𝑸𝑾, 𝑴𝟐 − 𝝔 𝟑 (𝑴𝟐, 𝑴𝟑) The signal track has the consistent 𝜠𝝔 𝟑𝟒 = 𝝔 𝟑 𝑴𝟐, 𝑴𝟑 − 𝝔 𝟒 𝑴𝟑, 𝑴𝟒 sign of each ∆𝜚 12 and ∆𝜚 23 . 𝜠𝝔 difference = 𝜠𝝔 𝟑𝟒 − 𝜠𝝔 𝟐𝟑 Also, once the signal track is reconstructed, its 𝛦𝜚 difference have to be small. Example of x-y plane signal window 7 Jongho Lee (KNU) KPS, 24 - 26 Oct 2018
𝑞 𝑈 estimation using 𝛦𝜚 of pixel track segments • 𝑞 𝑈 of the pixel track is estimated with the correlation between the gen- level muon 𝑞 𝑈 and Δ𝜚 ( 𝜚 𝐶𝑇, 𝑀 𝑗 − 𝜚 𝑀 𝑗 , 𝑀 𝑘 ), where BS = beam spot 𝑞 𝑈 = 𝑔 1/Δ𝜚 , 𝑔 : first order polynomial function for fitting • Simulation sample Gen level 𝑞 𝑈 and Δ𝜚 used in singleMuon events without pile-up 2 < 𝑞 𝑈 < 200 𝐻𝑓𝑊 , −3 < 𝜃 < 3 Example Example BSL2 – L2D2 BSD1 – D1D3 8 Jongho Lee (KNU) KPS, 24 - 26 Oct 2018
Track isolation calculation based on the 𝑞 𝑈 • 𝑞 𝑈, 𝑗 : linear sum of 𝑞 𝑈 of other tracks 𝐽𝑡𝑝𝑚𝑏𝑢𝑗𝑝𝑜 except for the highest 𝑞 𝑈 track in ∆𝑆 < 0.3 = 𝑞 𝑈, 𝑗 cone 𝑞 𝑈, 𝑢𝑠𝑙 • 𝑞 𝑈, 𝑢𝑠𝑙 : linear sum of 𝑞 𝑈 of all tracks in ∆𝑆 < 0.3 cone Cut Region 1 ( 𝟏 < 𝜽 < 𝟏. 𝟗 ) • L1 EG 𝑭 𝑼 > 𝟑𝟏 𝑯𝒇𝑾 • • Signal efficiency: 99.5% • Background rejection: 70.6% 0.05 9 Jongho Lee (KNU) KPS, 24 - 26 Oct 2018
Calculation of Isolation for each region Cut Cut Cut • • • Sig.eff: Sig.eff: Sig.eff: 99.8% 99.4% 98.3% • • • Bkg. rej: Bkg.rej: Bkg.rej: 52.2% 54.0% 73.0% 1) 2) 3) 0.05 0.07 0.03 • • Sig.eff: Sig.eff: 1) Region2 ( 0.8 < 𝜃 < 1.4 ) 94.7% 95.8% 2) Region3 ( 1.4 < 𝜃 < 1.7 ) • • Bkg.rej: Bkg.rej: Cut Cut 63.4% 53.3% 3) Region4 ( 1.7 < 𝜃 < 2.1 ) 4) Region5 ( 2.1 < 𝜃 < 2.7 ) 5) Region6 ( 2.7 < 𝜃 < 3.0 ) • L1 EG 𝑭 𝑼 > 𝟑𝟏 𝑯𝒇𝑾 4) 5) 0.3 0.3 10 Jongho Lee (KNU) KPS, 24 - 26 Oct 2018
Track isolation cut region1 ( 𝟏 < 𝜽 < 𝟏. 𝟗 ) • Isolation cut : 0.05 signal efficiency: 99.5% background rejection: 70.6% - signal efficiency - background rejection 11 Jongho Lee (KNU) KPS, 24 - 26 Oct 2018
Track isolation cut region6 ( 𝟑. 𝟖 < 𝜽 < 𝟒. 𝟏 ) • Isolation cut : 0.3 signal efficiency: 95.8% background rejection: 53.3% - signal efficiency - background rejection 12 Jongho Lee (KNU) KPS, 24 - 26 Oct 2018
Preliminary results of track isolation 13 Jongho Lee (KNU) KPS, 24 - 26 Oct 2018
Preliminary results of track isolation Background Background 𝟏 < 𝜽 < 𝟐. 𝟔 𝟐. 𝟔 < 𝜽 < 𝟑. 𝟔 reduction factor reduction factor L1 EG 336 kHz - 103 kHz - L1 EG + Pixel 37 kHz 9.1 23 kHz 4.5 33 kHz 10 22 kHz 4.7 L1 EG + L1 Track (Iso) 15 kHz 22.4 8.5 kHz 12.1 L1 EG + Pixel + Isolation 14 Jongho Lee (KNU) KPS, 24 - 26 Oct 2018
Preliminary results of track isolation Background Background 𝟏 < 𝜽 < 𝟑. 𝟔 𝟏 < 𝜽 < 𝟒. 𝟏 reduction factor reduction factor L1 EG 436 kHz - 505 kHz - L1 EG + Pixel 59 kHz 7.4 70 kHz 7.2 55 kHz 7.9 Not available Not available L1 EG + L1 Track (Iso) 24 kHz 18.1 29 kHz 17.4 L1 EG + Pixel + Isolation 15 Jongho Lee (KNU) KPS, 24 - 26 Oct 2018
Conclusion • The pixel track isolation was achieved through following process Reconstructed pixel tracks using kinematic parameters Estimation of pixel track 𝑞 𝑈 using ∆𝜚 Calculation of isolation based on the estimated 𝑞 𝑈 • The overall level-1 pixel trigger efficiency including isolation is • average 95% in 𝜽 < 𝟑. 𝟐 • average 90% in 𝜽 < 𝟒. 𝟏 • We improved the performance of level-1 pixel triggers 2.5 times by pixel track isolation while keeping high trigger efficiency • The total background reduction factor is • 18 in 𝜽 < 𝟑. 𝟔 • 17 in 𝜽 < 𝟒. 𝟏 16 Jongho Lee (KNU) KPS, 24 - 26 Oct 2018
Back up 17 Jongho Lee (KNU) KPS, 24 - 26 Oct 2018
Track isolation cut region2 ( 𝟏. 𝟗 < 𝜽 < 𝟐. 𝟓 ) • Isolation cut : 0.05 signal efficiency: 99.8% background rejection: 52.2% - signal efficiency - background rejection 18 Jongho Lee (KNU) KPS, 24 - 26 Oct 2018
Track isolation cut region3 ( 𝟐. 𝟓 < 𝜽 < 𝟐. 𝟖 ) • Isolation cut : 0.03 signal efficiency: 99.4% background rejection: 54.0% - signal efficiency - background rejection 19 Jongho Lee (KNU) KPS, 24 - 26 Oct 2018
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