Progress update on muon combinatorial background [ - PowerPoint PPT Presentation

Progress update on muon combinatorial background [ oliver.lantwin@cern.ch ] 11th SHiP Collaboration Meeting, cern 8th June 2017 Oliver Lantwin , Kostas Petridis

Introduction Update of combinatorial background studies with Oliver Lantwin (icl) 11th SHiP Collaboration Meeting, cern Introduction 2/19 ◮ New detector geometry and shield ◮ Updated kinematics for toy generator

Introduction Muons from Muon Background Study of muon kinematics at the tracking stations Toy-mc Results Conclusion

Simulation procedure NB: Closely following Kostas’s procedure used for tp with some recent departures (see later slides) Oliver Lantwin (icl) 11th SHiP Collaboration Meeting, cern Introduction 4/19 ◮ Use muons with well-reconstructed tracks from muon background ◮ Form all possible combinations ◮ Use distributions of position, momenta to seed a fast simulation ◮ Use data-driven methods to estimate kinematics ◮ Generate according to these kinematics

Muons pairs used as seed Oliver Lantwin (icl) 11th SHiP Collaboration Meeting, cern Muons from Muon Background 5/19 ◮ Updated to 10 × the full muon sample ( 9 × with randomised φ ) ◮ 29 muons → 406 combinations ◮ Current geometry ◮ Current reconstruction

Hit distribution of muons (used as seed) 8000 62.98 Mean y -24.99 Mean x 29 Entries CombMuXYstate 9000 7000 115 6000 5000 4000 3000 2000 1000 0 0 0 Std Dev x Std Dev y 0 127452 Muons from Muon Background 11th SHiP Collaboration Meeting, cern Oliver Lantwin (icl) XY 0 0 0 0 0 170.9 0 0 0 0.03767 Skewness y 0.04238 Skewness x 1.275e+05 Integral 0 127452 X 1st state (cm) 500 100 0 -100 -200 -300 -400 -500 Y 1st state (cm) 400 300 300 200 100 0 -100 -200 -300 -400 -500 200 400 0 170.9 0 0 0 0.03767 Skewness y 0.04238 Skewness x 1.275e+05 Integral Std Dev y 500 115 Std Dev x 62.98 Mean y -24.99 Mean x 29 Entries CombMuXYstate 6/19

7/19 20000 29 Entries CombMuPtPstate 70000 60000 50000 40000 30000 10000 0.2509 0 p2 p3 p3 p2 using something more realistic now? p1 4.602e+08 / 997 Oliver Lantwin (icl) Mean x Mean y 0 0 0 0 0 0 127452 0 0 0 2.701 10.01 Skewness y 1.382 Skewness x 1.275e+05 Integral 14.78 Std Dev y 0.2518 Std Dev x 11th SHiP Collaboration Meeting, cern 0 4.602e+08 / 997 5 300 250 200 150 100 50 0 Muons from Muon Background 4.5 Entries 4 3.5 3 2.5 2 1.5 1 0.5 0 CombMuPtPstate 29 0 1.382 0 127452 0 0 0 0 2.701 Skewness y Skewness x Mean x 1.275e+05 Integral 14.78 Std Dev y 0.2518 Std Dev x 10.01 Mean y 0.2509 p1 p t – p distribution of muons (used as seed) p T p p [ GeV ] χ 2 / nd χ 2 / nd f f − 4 . 068 ± 0 . 0119 − 4 . 068 ± 0 . 0119 − 0 . 09252 ± 0 . 0002628 − 0 . 09252 ± 0 . 0002628 11 . 24 ± 0 . 005143 11 . 24 ± 0 . 005143 p T [ GeV ] ◮ Simple 2D Exponential fjt (no cross-terms, assume p , p t uncorrelated) ◮ Fit function chosen for tp because of lack of statistics → investigate

The toy-mc justifjed? Oliver Lantwin (icl) 11th SHiP Collaboration Meeting, cern Muons from Muon Background 8/19 ◮ Sample muon positions from histogram of seed muons ◮ Sample muon momenta from fjt ◮ Randomise φ of muon direction → Uniform distribution? Assumption → Study kinematics more closely!

Setup 1e+07 Std Dev y 114.9 Std Dev x 3.972 Mean y 201 Mean x Entries Integral htemp 10 1 0 0 0 0 1e+07 6.1 1e+07 0 0 Study of muon kinematics at the tracking stations 11th SHiP Collaboration Meeting, cern Oliver Lantwin (icl) muon spectrum, beyond kinematic limit Figure: Generated momentum distribution 0 0 0 Skewness x 1e+07 0 0 0 0 2.424 Skewness y -0.000686 0 0 0 0 2.424 30 25 20 15 10 5 400 htemp 350 300 250 200 150 100 50 0 40 35 Entries 114.9 Skewness y -0.000686 Skewness x 1e+07 Integral 1e+07 Std Dev y 6.1 9/19 3.972 Mean x 201 Mean y Std Dev x ◮ Generate 10 000 000 muons with particle gun, uniform in 3 < η < 8 and 2 GeV < p < 400 GeV and − π < φ < π ◮ Hans’s shield confjguration ◮ Study φ as a function of p , p T for muons hitting the tracker µ ± P T [ GeV ] 10 5 10 4 10 3 10 2 P [ GeV ] ◮ NB: signifjcantly higher momenta and transverse momenta than in actual

10/19 -0.4358 Std Dev x 78.58 Std Dev y 2.577 Integral 4.038e+05 Skewness x Skewness y Mean y 0.9441 0 0 0 0 403850 0 0 4.193 200.4 0 8 250 300 350 0 2 4 6 10 Mean x 12 14 16 18 20 p_pt Entries 403850 0 0 100 403850 -0.4358 Skewness y 0.9441 0 0 0 0 0 4.038e+05 0 0 0 Figure: Momentum and transverse momentum of muons creating hits in the tracking station: left: at generation; right: at the tracking station Oliver Lantwin (icl) 11th SHiP Collaboration Meeting, cern Study of muon kinematics at the tracking stations Skewness x Integral 50 p_pt 100 150 200 250 300 350 400 450 Entries 2.577 403850 Mean x 200.4 Mean y 4.193 Std Dev x 78.58 Std Dev y 200 150 50 2.886 Mean x 286.1 Mean y 5.728 Std Dev x 88.39 Std Dev y Integral Entries 8.073e+05 Skewness x -0.7555 Skewness y 1.034 0 33 0 807288 18 0 350 0 50 100 150 200 250 300 400 16 0 2 4 6 8 10 12 14 0 807255 0 Skewness y 2.886 0 Integral 8.073e+05 Skewness x -0.7555 1.034 88.39 0 33 0 0 0 807255 0 Std Dev y Std Dev x 0 400 0 0 0 100 200 300 500 5.728 600 mu_ppt_original Entries 807288 Mean x 286.1 Mean y 0 p - p T distribution before and after shield µ ± µ − 20 mu_ppt_original P T [ GeV ] P T [ GeV ] P [ GeV ] P [ GeV ]

11/19 403850 Study of muon kinematics at the tracking stations 11th SHiP Collaboration Meeting, cern Oliver Lantwin (icl) 0.01347 Skewness 4.038e+05 Integral 0 Overfmow 0 Underfmow 1.983 Std Dev Mean -0.0212 Entries 3 -3 -2 -1 0 1 phi 2 2000 3000 4000 5000 6000 7000 φ distribution µ − φ φ ◮ Results for muons, for anti-muons results are virtually the same with φ shifted by π ◮ φ distribution clearly not uniform

12/19 0.01347 Std Dev x 1.983 Std Dev y 2.577 Integral 4.038e+05 Skewness x Skewness y Mean y 0.9441 0 0 0 0 403850 0 4.193 -0.0212 0 8 1 2 3 0 2 4 6 10 Mean x 12 14 16 18 20 phi_pt Entries 403850 0 0 -2 0 4.038e+05 Skewness x 0.01347 Skewness y 0.9441 0 0 0 2.577 403850 0 0 0 0 Oliver Lantwin (icl) 11th SHiP Collaboration Meeting, cern Study of muon kinematics at the tracking stations Integral Std Dev y 0 400 50 100 150 200 250 300 350 450 1.983 phi_pt Entries 403850 Mean x -0.0212 Mean y 4.193 Std Dev x 0 -1 -3 Skewness x 200.4 Std Dev x 1.983 Std Dev y 78.58 Integral 4.038e+05 0.01347 -0.0212 Skewness y -0.4358 0 0 0 0 403850 Mean y Mean x 0 0 -3 -2 -1 0 1 2 3 50 403850 100 150 200 250 300 350 phi_p Entries 0 0 0 0 0 Integral 4.038e+05 Skewness x 0.01347 Skewness y -0.4358 0 1.983 0 0 403850 0 0 0 0 Std Dev y 78.58 Std Dev x 140 20 40 60 80 200.4 120 100 160 180 phi_p Entries 403850 Mean x -0.0212 Mean y φ - p T and φ - P distributions µ − φ − P µ − φ − P P [ GeV ] P T [ GeV ] φ φ ◮ Some clear hotspots visible.

The toy-mc Oliver Lantwin (icl) 11th SHiP Collaboration Meeting, cern Toy-mc 13/19 ◮ Sample muon positions from histogram of seed muons ◮ Sample muon momenta from fjt ◮ Sample φ from p - p t - φ histogram in slice corresponding to generated p - p t → further studies into implicit assumptions ongoing ◮ Generate 1958 * muons → 1915903 pairs * 2 events are discarded because their p t > p

14/19 CombGenMuPtPstate Std Dev x 11.49 Mean y 0.282 Mean x 1953 Entries 400 Std Dev y 350 300 250 200 150 100 50 0 0.2354 11.37 0 1953 Results 11th SHiP Collaboration Meeting, cern Oliver Lantwin (icl) 100 GeV 0 0 0 0 0 Integral 0 0 0 2.261 Skewness y 1.829 Skewness x 1953 0 0 0 4.5 250 200 150 100 50 0 5 4 Entries 3.5 3 2.5 2 1.5 1 0.5 0 300 CombGenMuPtPstate 1953 Mean x 1953 0 0 0 0 2.261 Skewness y 1.829 Skewness x 1953 Integral 11.37 Std Dev y 0.2354 Std Dev x 11.49 Mean y 0.282 Generated p t – p distribution of muons (from toy-mc) p T p p [ GeV ] p T [ GeV ] ◮ Note: Sample muon momenta from fjt (i.e. interpolate histogram) up to

15/19 0.06746 Results 11th SHiP Collaboration Meeting, cern Oliver Lantwin (icl) -0.05129 Skewness 1953 Integral 0 Overfmow 0 Underfmow 1.772 Std Dev Mean 1953 2 -3 -2 -1 0 1 3 10 20 30 40 50 CombGenMuPhi Entries Generated φ distribution of muons (from toy-mc) µ − φ φ

Comparison of seed muons vs. toy-mc muons 2.177e+04 Mean 377.6 Std Dev 412.8 Underfmow 0 Overfmow Integral Entries 1.884e+06 Skewness 1.42 IPtar Oliver Lantwin (icl) 11th SHiP Collaboration Meeting, cern Results 1906128 CombGenMuTargIP IP to target (cm) 1400 0 200 400 600 800 1000 1200 1600 0.0025 1800 2000 Entries 0 0.0005 0.001 0.0015 0.002 16/19

Comparison of seed muons vs. toy-mc muons 6.411e+05 Mean 161.4 Std Dev 122.2 Underfmow 0 Overfmow Integral Entries 1.265e+06 Skewness -0.3702 Doca Oliver Lantwin (icl) 11th SHiP Collaboration Meeting, cern Results 1906128 CombGenMuDoca 17/19 140 0 20 40 60 80 100 120 160 0.01 180 200 Entries 0.002 0.004 0.006 0.008 doca ( µ, µ )( cm )