First Measurement of the Neutron-Argon Cross Section Between 100 and 800 MeV Scott Locke (for the CAPTAIN Collaboration) University of California, Irvine 09/09/2019 TAUP 2019
DUNE and Liquid Argon (LAr) Experiments • Many current and future experiments look to use a LAr Time Projection Chamber (TPC) for neutrino detection, given its many ideal properties • DUNE (Deep Underground Neutrino Experiment) is one of the future large- scale experiments to help probe some of the unresolved neutrino questions • CP-violation, ν mass hierarchy (MH), other exotic phenomena 09/09/2019 Scott Locke- UC Irvine 2
Detecting (Anti-) Neutrinos • DUNE looks to examine oscillation neutrinos starting at ~500 MeV and up to ~10 GeV • Going through different energy ranges, different modes of interactions dominate • Quasi-elastic • Resonant Production • Deep inelastic scattering • DUNE’s energy ranges covers all three charged Hadronic energy budget current interactions, posing issues for event reconstruction • Accurate energy reconstruction is needed • Small shift in neutrino energy → big changes in oscillation probability • Many of these processes will have neutral particles in the final state • These neutral particles carry away energy, leading to mis- reconstructed energies of the events • How much we underestimate the missing energy greatly affects the best fits for mixing parameters 30% to neutrons Phys. Rev. D 92, 091301 (2015) arXiv:1811.06159 09/09/2019 Scott Locke- UC Irvine 3
Implications of Neutrons on Energy Reconstruction • Neutrons are responsible for a significant amount the energy that escapes detection • Neutrons are a possible product in all three forms of charged current interactions to be seen by LAr experiments • Anti- neutrinos and neutrinos produce different numbers of neutrons → impact on MH and δ cp • Neutrons do not thermalize easily in LAr • Neutrons are not well contained, even in a large detector • Many of the models used to estimate missing energy, have large unconstrained uncertainties Energy carried away by neutrons 09/09/2019 Scott Locke- UC Irvine Plots by J. Chaves 4
Current Data for n on LAr • Not much data at DUNE energies, and existing data is from is from R.R. Winters et al., Phys. Rev. C43, 492 (1991) – www.nndc.bnl.gov 09/09/2019 Scott Locke- UC Irvine 5
mini-CAPTAIN at LANL • 400 kg instrumented hexagonal TPC • 32cm drift, 50 cm apothem • ~1000 channels, 3mm wire pitch, 3 signal planes (+ ground and grid plane) • Same cold electronics and electronics chain as MicroBooNE • Photon detection system (PDS) for Time of Flight (ToF) calculation Y • Run July 2017, at WNR at LANL Walter Sondheim X Beam • Results based on special low intensity run mini-CAPTAIN 09/09/2019 6 Scott Locke- UC Irvine
Basic Analysis Strategy • Find tracks in TPC in time with beam and in beam spot • Match tracks in TPC to hits in PDS • Use timing from PDS to determine neutron energy • For tracks in each kinetic energy bin, fit exponential as function of depth Neutron Flux depleted as function of depth neutron flux neutron scatters proton tracks 09/09/2019 Scott Locke- UC Irvine 7
Bottom PDS Arrangement Top PDS arrangement PDS • Hamamatsu R8520-506 MOD • 1x1 in, 25% QE at LAr temperature, special Bialkali LT • ~11 pe/MeV in Mini-CAPTAIN • 24 PMTs • 21 in actual operation • Calculate event time in TPC using light PMT and base collected by PDS • Charge drift is slow in the detector, use photons from the event for time • Used for correction in Z position of event • Calculate neutron energy from ToF • PDS is triggered on RF signal, and PDS can also self-trigger if enough light is seen by PMTs 09/09/2019 Scott Locke- UC Irvine 8
Energy and PDS Timing • Beam creates a trigger by interacting with a coil to create RF pulse • TPC is triggered off this RF pulse • The RF pulse is composed of 625 μs 200 μ s wide macropulse with 10 ms between macropulses • Macropulses have micropulses 200 μ s apart, normal beam running is 1.8 μ s • Get ~1 neutron / 6 micropulses • Use RF timing and light emitted in TPC to calculate ToF of neutrons, and making energy calculation • Make correction for micropulse in ToF calculation 09/09/2019 Scott Locke- UC Irvine 9
TPC Preliminary cosmic • 3 planes with ~350 wires each • X plane (collection) perpendicular to x-axis, Beam U and V planes 60° with respect to X plane proton candidate Region • Triggered on RF with a 4.75 ms data acquisition window • 1.85 ms pretrigger • 600 μ s beam time Neutron event from low intensity run • 2.3 ms post trigger • Use wire hits and time to reconstruct tracks within the detector • Find 2D clusters in a single plane and build 3D tracks • Detector is slightly rotated with respect Beam Direction to the beam line • Large windows outside beam window used for calibration with cosmics preliminary 09/09/2019 Scott Locke- UC Irvine 10
Hit-Finding Efficiency • Data is from cosmic runs • Hit finding inefficiency seen for large wire numbers Dead wires • Most likely from unresponsive wires → only consider lower wire numbers • Higher wire numbers are upstream with respect to the beam • Fiducial volume: • -400.6 mm < x < 4.6 mm • corrected z: -195mm < z < -145 mm • must be in the 27-mm wide beam 09/09/2019 Scott Locke- UC Irvine 11
Cross section fit • For a given energy bin, the total cross section is proportional to the coefficient of 481-674 MeV the neutron flux depletion rate for a given topology: • Exponential fits with binning based on available statistics Beam • Fits reasonable for given statistics • Systematic uncertainties: • Multi-track from more than 1 n interacting in beam window x (mm) • Impact on cross-section measurement 10% • Uncertainty in track reconstruction, bin placement, track finding (all percent level) 09/09/2019 Scott Locke- UC Irvine 12
Neutron Cross Sections • Exponential fits with binning based on available statistics • Fits reasonable for given statistics • Cross section energy- weighted average is: 0.91±0.10(stat)±0.09(sys) barns • Recently published results: PRL 123, 042502 (2019) 09/09/2019 Scott Locke- UC Irvine 13
CAPTAIN Detector • Cryostat • Capacity: 10 tons • TPC • Hexagonal prism with 1m vertical drift, 1m apothem, 2000 channels, 3mm pitch, 5 instrumented tons • Photon detection system • Laser calibration system • Same cold electronics and electronics chain as MicroBooNE 09/09/2019 Scott Locke- UC Irvine 14
CAPTAIN Physics Program • Low-energy neutrino physics related • Measure the neutrino CC and NC cross-sections on argon in the same energy regime as supernova neutrinos • Measure the correlation between true neutrino energy and visible energy for events of supernova-neutrino energies • Medium-energy neutrino physics related • Measure neutron interactions and event signatures (e.g. pion production) to allow us to constrain number and energy of emitted neutrons in neutrino interactions (at DUNE, mean neutron K.E. from the LBNF beam ~ 400 MeV) • Measure higher-energy neutron-induced processes that could be backgrounds to n e appearance e.g. 40 Ar(n, p 0 ) 40 Ar (*) Low-Energy Neutrino Beam Neutron Beam 09/09/2019 Scott Locke- UC Irvine 15
Summary • We have made the first neutron-argon cross section measurement between 100 and 800 MeV • Cross section energy-weighted average is 0.91±0.10(stat)±0.09(sys) barns • More physics to support other LAr experiments and DUNE • neutron-argon interactions – First measured cross-section in this energy regime, improve the measurement, exclusive channels • Integrate neutron ID and measurements into neutrino energy reconstruction for DUNE and SBN • Moving forward, build CAPTAIN with pixelated readout • Deploy CAPTAIN 09/09/2019 Scott Locke- UC Irvine 16
CAPTAIN Collaboration • Alabama: Ion Stancu • LANL: Elena Guardincerri, Nicholas Kamp, David Lee, William Louis, Geoff Mills, • LBL: Craig Tull Jacqueline Mirabal-Martinez, Jason Medina, • Boston University: Christopher Grant John Ramsey, Keith Rielage, Constantine Sinnis, Walter Sondheim, Charles Taylor, • BNL: Hucheng Chen, Veljko Radeka, Craig Richard Van de Water Thorn • UC Davis: Daine Danielson, Steven Gardiner, • New Mexico: Michael Gold, Alexandre Mills, Emilija Pantic, Robert Svoboda Brad Philipbar • UC Irvine: Jianming Bian, Scott Locke, Michael • New Mexico State: Robert Cooper Smy • University of Pennsylvania: Connor Callahan, • UC Los Angeles: David Cline, Hanguo Wang Jorge Chaves, Shannon Glavin, Avery Karlin, • Hawaii: Jelena Maricic, Marc Rosen, Yujing Christopher Mauger, Keith Wiley Sun • Stony Brook: Neha Dokania, Clark McGrew, • Houston: Lisa Whitehead Sergey Martynenko, Chiaki Yanagisawa Spokesperson: Christopher Mauger; Deputy Spokesperson: Clark McGrew 09/09/2019 Scott Locke- UC Irvine 17
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Backup 09/09/2019 Scott Locke- UC Irvine 19
Cross Section Fit 100-199 MeV 199-296 MeV X position [mm] X position [mm] 09/09/2019 Scott Locke- UC Irvine 20
Cross Section Fit 296-369 MeV 369-481 MeV 674-900 MeV X position [mm] X position [mm] X position [mm] 09/09/2019 Scott Locke- UC Irvine 21
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