Vertex reconstruction Vertex reconstruction in large liquid - PowerPoint PPT Presentation

Vertex reconstruction Vertex reconstruction in large liquid scintillator detectors in large liquid scintillator detectors David Meyhöfer March 20, 2017 Universität Hamburg 1 / 17

Vertex reconstruction Why a vertex reconstruction? Novel track reconstruction has been developed Holds great potential for any liquid scintillator detector Has a limited number of fundamental assumptions Gain topological energy deposition information Novel track reconstruction needs a reference point Providing vertex to the Novel track reconstruction Currently for LENA(low energy neutrino astronomy) Operation in an energy range of a few MeV to GeV Also works with a start point near the track 2 / 17

Vertex reconstruction MeV range Time of flight Time of flight for photon i t i ˆ = Time of flight for photon i t i = D ( x i ( 0 ) , x i ( t )) v g ˆ = Group velocity v g D ( x i ( 0 ) , x i ( t )) distance x i ( 0 ) to x i ( t ) Not considered Scattering Absorption with reemission Scintillation decay time Figure : Time of flight for a photon. Electronic effects 3 / 17

Vertex reconstruction MeV range Time difference histogram t i , dif ˆ = Difference in time for photon i t i , dif = t i , hit − t i t hit ˆ = Measured time for photon i t i ˆ = Time of flight for photon i -1,0,5 -16,20,511 80 80 [a.u.] [a.u.] Entries 1280 Entries 1280 Mean 18.39 Mean 16.53 70 70 Std Dev 25.88 Std Dev 27.1 60 60 50 50 40 40 30 30 20 20 10 10 0 0 − − − − 100 50 0 50 100 100 50 0 50 100 [ns] [ns] (a) Near the true vertex (b) ∼ 5 m away from true vertex Figure : Examples for time difference histograms at the true vertex and 5 m aside from the true vertex. 4 / 17

Vertex reconstruction MeV range Grid (a) First iteration (b) Following iteration Figure : 2 dimensional example grid to illustrate the vertex finding. 5 / 17

Vertex reconstruction MeV range Angular acceptance of PMTs α incident angle � p · � n � n PMT normal vector cos α = | � p | · | � n | � p incident vector 1 ) α 0.9 ( a P 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 α [rad] 6 / 17

Vertex reconstruction Time reconstruction Time fitting and evaluation algorithm ToE Entries 1280 100 − 100 Mean 3.748 Std Dev 2.79 80 80 60 60 40 40 20 20 0 0 − − − − − − − − − − 10 8 6 4 2 0 2 4 6 8 10 10 8 6 4 2 0 2 4 6 8 10 [ns] [ns] (a) Histogram at determined vertex (b) Fit for (a) The fit considers: t i , dif = t i − t i , hit Scintillation decay time PMT time resolution 7 / 17

Vertex reconstruction GeV range High energy event development (a) A few nanoseconds after the (b) First hit distribution after the event events start Figure : Distribution of first hit information 8 / 17

Results MeV range LEVertex Distance of MCVertex to RecoVertex per Energy 10 Entries Entries 10000 10000 80 Mean x Mean x 14.06 14.06 9 Mean y Mean y 5.354 5.354 70 9.016 9.016 Std Dev x Std Dev x 8 Std Dev y Std Dev y 2.682 2.682 60 0 0 0 0 0 0 7 0 9199 801 0 9199 801 0 0 0 0 0 0 50 Energy [MeV] 6 5 40 4 30 3 20 2 10 1 0 0 0 5 10 15 20 25 30 35 40 45 50 Distance of MCVertex to RecoVertex [cm] Figure 9 / 17

Results MeV range MeV positional reconstruction results 1200 Entries Entries 10000 10000 Std Dev Std Dev 12.95 12.95 Underflow Underflow 225 225 1000 Overflow Overflow 225 225 χ χ 2 2 / ndf / ndf 916.7 / 91 916.7 / 91 Prob Prob 0 0 800 ± ± Constant Constant 984.4 984.4 16.1 16.1 ± ± Mean Mean 0.08323 0.08323 0.07531 0.07531 Entries ± ± Sigma Sigma 6.998 6.998 0.086 0.086 600 400 200 Results for 10k electron 0 − − − − − 100 80 60 40 20 0 20 40 60 80 100 Distance of RecoX from TrueX [cm] events 1200 Entries Entries 10000 10000 Std Dev Std Dev 12.83 12.83 Fit for X,Y and Z direction Underflow Underflow 264 264 1000 Overflow Overflow 220 220 χ χ 2 2 / ndf / ndf 943 / 90 943 / 90 Prob Prob 0 0 800 ± ± Constant Constant 972.1 972.1 16.6 16.6 ± ± Mean Mean 0.04976 0.04976 0.07602 0.07602 0.5 to 10.0 MeV Energy Entries Sigma Sigma 7.036 7.036 ± ± 0.093 0.093 600 400 Random position in the 200 detector 0 − − − − − 100 80 60 40 20 0 20 40 60 80 100 Distance of RecoY from TrueY [cm] σ x , y , z = ± 14 . 34 cm 800 Entries Entries 10000 10000 Std Dev Std Dev 15.28 15.28 Underflow Underflow 143 143 700 Overflow Overflow 163 163 χ χ 2 2 / ndf / ndf 559.2 / 96 559.2 / 96 600 Prob Prob 0 0 ± ± Constant Constant 704.4 704.4 10.4 10.4 500 ± ± Mean Mean 0.03671 0.03671 0.10826 0.10826 Entries Sigma Sigma 10.35 10.35 ± ± 0.11 0.11 400 300 200 100 0 − 100 − 80 − 60 − 40 − 20 0 20 40 60 80 100 Distance of RecoZ from TrueZ [cm] 10 / 17

Results MeV range Time reconstruction results Only results within 20 cm of true vertex From fit σ t ± 0 . 33 ns Gaussian distribution around 0 ns expected Shift and excess due to underestimated TOFs Figure : Event time reconstruction results in MeV range 11 / 17

Results GeV range Reconstruction of a GeV muon YZ-projection XZ-projection XY-projection 2000 1000 2000 700 1500 1500 1000 1000 800 600 1000 1000 800 500 500 500 500 600 400 [cm] [cm] [cm] 600 0 0 0 400 300 − − 500 500 400 − 500 − − 200 1000 1000 200 200 − 1000 − − 1500 1500 100 − − 2000 2000 0 0 0 − − − − − − − − − − 2000 1500 1000 500 0 500 1000 1500 2000 2000 1500 1000 500 0 500 1000 1500 2000 1000 500 0 500 1000 [cm] [cm] [cm] Figure : Example muon event 5.8 GeV Simulated event energy 12 / 17

Results GeV range GeV positional reconstruction results Entries Entries 2073 2073 90 Std Dev Std Dev 20.33 20.33 Underflow Underflow 253 253 80 Overflow Overflow 283 283 χ χ 2 2 / ndf / ndf 98.34 / 80 98.34 / 80 70 Prob Prob 0.08022 0.08022 ± ± 60 Constant Constant 79.02 79.02 2.65 2.65 ± ± Mean Mean 0.3173 0.3173 0.3846 0.3846 Entries ± ± 50 Sigma Sigma 14.54 14.54 0.30 0.30 40 30 Results for 2500 muon 20 10 events 0 − − − − − 100 80 60 40 20 0 20 40 60 80 100 Distance of RecoX from TrueX [cm] Entries Entries 2073 2073 80 Std Dev Std Dev 21.08 21.08 Underflow Underflow 289 289 Fit for X,Y and Z direction 70 Overflow Overflow 256 256 χ χ 2 2 / ndf / ndf 116.6 / 82 116.6 / 82 60 Prob Prob 0.00722 0.00722 ± ± Constant Constant 78.27 78.27 2.72 2.72 ± ± 50 Mean Mean 0.5295 0.5295 0.3847 0.3847 Entries Sigma Sigma 14.39 14.39 ± ± 0.32 0.32 40 30 5.0 to 10.0 GeV Energy 20 10 0 − − − − − 100 80 60 40 20 0 20 40 60 80 100 Distance of RecoY from TrueY [cm] Random position in the Entries Entries 2073 2073 80 Std Dev 42.78 Std Dev 42.78 detector 70 Underflow 346 Underflow 346 Overflow Overflow 296 296 60 50 Entries 40 30 20 10 0 − 100 − 80 − 60 − 40 − 20 0 20 40 60 80 100 Distance of RecoZ from TrueZ [cm] 13 / 17

Results GeV range GeV positional reconstruction near track 140 Entries Entries 2500 2500 Std Dev Std Dev 20.97 20.97 Underflow Underflow 13 13 120 Overflow Overflow 14 14 χ χ 2 2 / ndf / ndf 104 / 73 104 / 73 100 Prob Prob 0.009956 0.009956 ± ± Constant Constant 94.99 94.99 2.49 2.49 − − ± ± Mean Mean 0.2498 0.2498 0.4131 0.4131 80 Entries ± ± Sigma Sigma 19.93 19.93 0.33 0.33 60 40 Distance to true track 20 0 − − − − − 100 80 60 40 20 0 20 40 60 80 100 Distance of RecoX from TrackX [cm] Point near track is enough Entries Entries 2500 2500 Std Dev Std Dev 21.08 21.08 120 Underflow Underflow 14 14 for Novel track Overflow Overflow 12 12 χ χ 2 2 / ndf / ndf 100 123.6 / 73 123.6 / 73 Prob Prob 0.0001992 0.0001992 ± ± Constant Constant 94.18 94.18 2.50 2.50 reconstruction 80 − − ± ± Mean Mean 0.4333 0.4333 0.4158 0.4158 Entries Sigma Sigma 19.94 19.94 ± ± 0.34 0.34 60 40 20 Fit for X,Y and Z direction 0 − − − − − 100 80 60 40 20 0 20 40 60 80 100 Distance of RecoY from TrackY [cm] Entries Entries 2500 2500 180 Std Dev Std Dev 16.11 16.11 σ x , y , z = ± 34 . 56 cm Underflow Underflow 2 2 160 0 0 Overflow Overflow χ χ 2 2 140 / ndf / ndf 120.7 / 54 120.7 / 54 − − Prob Prob 5.186e 5.186e 07 07 ± ± Constant Constant 123.8 123.8 3.2 3.2 120 ± ± Mean Mean 0.04114 0.04114 0.31748 0.31748 Entries 100 Sigma Sigma 15.34 15.34 ± ± 0.24 0.24 80 60 40 20 0 − 100 − 80 − 60 − 40 − 20 0 20 40 60 80 100 Distance of RecoZ from TrackZ [cm] 14 / 17

Results GeV range GeV time reconstruction Only results within 20 cm of true vertex From fit σ t ± 0 . 27 ns Gaussian distribution around 0 ns expected Shift due to underestimated TOFs and shift of reconstructed vertex along Figure : Event time reconstruction track results in GeV range 15 / 17