Cosmic Background suppression for a NuMI electron-neutrino cross- section measurement in MicroBooNE Colton Hill on behalf of the MicroBooNE Collaboration New Perspectives 5 June 2017
Motivation - Why do we care about ν e ? MiniBooNE “Low Energy Excess” • Two key motivations: - LSND/MiniBooNE ν e -like excess - MiniBooNE was limited by the π 0 backgrounds. - We have limited data on ν e interactions around 1 GeV. • ν e cross section also critical for DUNE. 2 Colton Hill - University of Manchester
Minerva ν e Cross Section Measurements arXiv:1509.05729 • The few measurements of ν e CC cross-section were made by the Gargamelle, Minerva and T2K experiments. • MicroBooNE is also well-equipped to measure T2K the ν e CC cross section given its excellent arXiv:1407.7389 spatial resolution and calorimetric capabilities. • MicroBooNE’s energy range is around 1 GeV. 3 Colton Hill - University of Manchester
MicroBooNE Detector Wilson Hall • MicroBooNE sits along the BNB and about 8° off-axis from the center of MicroBooNE Neutrino Main Injector (NuMI). •TPC is “slow” so PMTs behind wire planes are used for triggering. BNB Beam NuMI Beam NuMI Beam BNB Beam 4 Colton Hill - University of Manchester
NuMI Beam at MicroBooNE NuMI Absorber MicroBooNE The GENIE generated ν e angles tell us from where along the NuMI beamline most of our neutrinos originate. Absorber Angular Distribution of NuMI Nue Theta [Degrees] BNB Beam NuMI Beam Φ Φ = 0 BNB Beam z z y BNB Work In-progress θ = 0 θ Beam Phi [Degrees] Phi [degrees] Target Hall z x 5 Colton Hill - University of Manchester
12 10 POT ν µ NuMI Beam at MicroBooNE 11 ν 10 20 µ / 6x10 ν e 10 10 ν e 2 ) / 50 MeV / cm Off-axis NuMI Flux 9 at MicroBooNE 10 •Measurement from NuMI gives result Neutrino Mode independent of BNB “low-energy excess”. 8 10 7 ν 10 ( • ν e fraction is larger for NuMI (~5%) vs BNB Φ 0 1 2 3 4 5 6 (~0.6%). Neutrino Energy [GeV] NuMI Nue Flux at MicroBooNE BNB Flux GENIE Parent (Neutrino Mode) K + 57.1% K 0L 41.2% μ + 1.6% π + 0.01% 6 Colton Hill - University of Manchester
Sample Topology NuMI DATA: RUN 10811, EVENT 2549. APRIL 9, 2017. 7 Colton Hill - University of Manchester
True Deposited Shower Energy QE Events Res 1400 Work In-progress DIS •For a cross section measurement MC Truth - GENIE v2.10.10 Coh 1200 we want to measure the shower 1000 energy. 800 •QE events deposit on-average the 600 most energy per shower. 400 •Other mode’s average deposited 200 shower energy peaks below ~200 0 MeV. 0 0.5 1 1.5 2 2.5 3 True Deposited Shower Energy [GeV] 8 Colton Hill - University of Manchester
Cosmic Rejection and ν e Selection • MicroBooNE sits on the surface - as such cosmic rays are a significant background. • For every neutrino interaction we expect around 300 cosmic only events. • Some of these will produce showers, looking like lone ν e interactions. • Selection cuts focus on rejecting cosmics: - Optical Cuts - Topological Cuts 9 Colton Hill - University of Manchester
Optical Filter 1 . 5 •The optical filter checks for two Measured Cosmic Rate (Beam-Off) things: NuMI Trigger Data (Beam-On) [4.83E18 POT] Fractional Flash Count per 0.5 µ s with respect to Cosmic Background 1 . 4 “Beam Spill” - A flash within the beam spill (the 1 . 3 time we expect neutrinos to arrive). 1 . 2 - One flash of at-least 50 photoelectrons. 1 . 1 •This removes cosmic events which 1 . 0 are “out of time”. 0 . 9 5 10 15 20 Time with respect to the NuMI Trigger Time [ µ s] 10 Colton Hill - University of Manchester
Reco Nue-like Vtx ZY Reco Nue-like Vtx ZY Cosmic - Nue Candidate Reconstructed Vertex ZY Fiducial Volume Cut 40 y [cm] 100 35 30 50 25 •As expected for the cosmic background, 0 20 their vertices are concentrated in the top 30 15 50 − cm of the detector. Cosmics Simulation 10 Work In-progress 5 100 − 0 0 200 400 600 800 1000 •Fiducial Volume: 10 cm from all sides, 30 cm z [cm] from top. Reco Nue-like Vtx ZY Reco Nue-like Vtx ZY Nues - Nue Candidate Reconstructed Vertex ZY 7 y [cm] 100 6 5 50 4 0 3 50 − 2 ν e CC Simulation Work In-progress 1 100 − 0 0 200 400 600 800 1000 z [cm] 11 Colton Hill - University of Manchester
Counts 30 Cosmic Simulation Vertex-to-Flash Work In-progress 25 20 • We can combine optical and topological information to place a cut: 15 10 - 2D distance between ν e shower-vertex and largest flash center - cut at 100 cm. 5 0 - Edge in ν e spectrum at 100 cm results from PMT 0 20 40 60 80 100 120 140 160 180 200 Nue shwr vtx to Flash Center [cm] Counts coverage granularity, and uncorrelated cosmic ν e CC Simulation 500 events w.r.t. beam flash position. Work In-progress 400 • This removes events where the shower is reconstructed far away from the largest flash in the event. 300 200 100 0 0 20 40 60 80 100 120 140 160 180 200 Nue shwr vtx to Flash Center [cm] ν e Shower-vertex to Flash Center [cm] 12 Colton Hill - University of Manchester
Pandora - MICROBOONE-NOTE-1015-PUB ν e -like Topology • This analysis makes use of automated reconstruction algorithms (Pandora). • Classification of a ν e -like topology requires: - At minimum one reconstructed shower. - A shower object associated to a neutrino vertex candidate with the greatest amount of TPC activity. arXiv:1506.05348 13 Colton Hill - University of Manchester
Cosmic Proximity Cut • This cut attempts to remove showers which result from a cosmic track (gamma / delta rays) Reco Nue-like Shwr Vtx to Reco Cosmic-like Reco Nue-like Shwr Vtx to Reco Cosmic-like y [cm] 16 100 • If a ν e shower vertex is within a 5 cm 14 radius cylinder, the event is cut. 50 12 10 0 8 6 50 − 4 Cosmic Simulation 2 Work In-progress 100 − 0 0 20 40 60 80 100 120 Distance to nearest cosmic track [cm] 14 Colton Hill - University of Manchester
Conclusion and Summary •We demonstrate that the open cosmic background can be reduced by 4 orders of magnitude. •With these cuts we retain an efficiency of over 60%. •A number of important backgrounds will soon be included in the analysis (such as NC and muon neutrinos). •A fully-developed ν e selection will be In Progress useful for further investigating the LSND/ MiniBooNE anomaly and future measurements on DUNE. 15 Colton Hill - University of Manchester
Backup Slides 16 Colton Hill - University of Manchester
T2K Differential Cross Section arXiv:1407.7389 17 Colton Hill - University of Manchester
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