Neutron Analysis PNPI, July 2009 n/g discrimination analysis μH neutron data analysis μH/Ar neutron data analysis

n/g discrimination

Pulse shape discrimination - integral method (n) and fitting method (n') Gamma Neutron time bins time bins

Pulse shape discrimination - fit method 𝐴 𝑒 −𝑡− 𝑡 𝑜   𝑟 − 𝑒 −𝑡− 𝑡 𝑜   𝑓1 𝑎 𝑒 −𝑡− 𝑡 𝑜   𝑟 − 𝑒 −𝑡− 𝑡 𝑜   𝑓2 𝑃 𝑡 𝑜 −𝑝𝑢𝑙𝑠𝑒𝑡𝑖𝑚𝑒  𝑟 ,  𝑓1 ,  𝑓2 −𝑟𝑖𝑠𝑒,𝑓𝑎𝑠𝑡,𝑠𝑙𝑜𝑤𝑡𝑖𝑚𝑒𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡𝑠 𝐴,𝑎−𝑓𝑎𝑠𝑡,𝑠𝑙𝑜𝑤𝑎𝑚𝑝𝑙𝑖𝑡𝑢𝑑𝑒𝑠 𝑃−𝑝𝑒𝑑𝑒𝑠𝑡𝑎𝑙 Do neutron fit with ( A,, to ) varied and a = 0.018 to determine χ2n and gamma fit with ( A,, to ) varied and a = 0.00 to determine χ2g

Pulse shape discrimination - fit method red – integral method gammas blue – integral method gammas

Pulse shape discrimination - integral method 𝑖= 𝑡 𝑜 − 𝑡 𝑠 ′... 𝑡 𝑜 − 𝑡 𝑒 ′  𝑆 𝑖 −𝑃 𝑖= 𝑡 𝑜 − 𝑡 𝑠 ... 𝑡 𝑜 − 𝑡 𝑒  𝑆 𝑖 −𝑃 𝑡 𝑜 −𝑝𝑢𝑙𝑠𝑒𝑐𝑒𝑛𝑡𝑒𝑟 𝑡 𝑠 𝑡 𝑒 , 𝑡 𝑠 ′ 𝑡 𝑒 ′−𝑓𝑢𝑙𝑙,𝑠𝑙𝑜𝑤𝑡𝑖𝑚𝑒𝑤𝑖𝑛𝑑𝑜𝑤𝑠 𝑆 𝑖 −𝑝𝑢𝑙𝑠𝑒𝑠𝑎𝑚𝑝𝑙𝑒𝑠 𝑃−𝑝𝑒𝑑𝑒𝑠𝑡𝑎𝑙 Fix pedestal from pre-samples, fix to from fit or spline, and optimize the full, slow time windows

Pulse shape discrimination - integral method blue – fit method neutrons red – fit method gammas

(using 2.23x109 good muon stops) μ-p data (using 2.23x109 good muon stops)

Pure H2 kinetics dN1 = -N1Λ1dt dN2 = +N1Λppμdt-N2Λ2dt dN3 = +N2Λopdt-N3Λ3dt where Λ1= Λo+Λs+Λppμ Λ2= Λo+Λom+Λop Λ3= Λo+Λpm singlet Λppμ Λo+Λs 2 ortho Λop Λo+Λom 3 para Λo+Λpm neutron time dependence, Nn(t) = ΛsN1(t) + ΛomN2(t) + ΛpmN3(t) electron time dependence, Ne(t) = Λo(N1(t) + N2(t) + N3(t))

Pure H2 kinetics previous work Λppμ = ( 2.5 ± 0.5 ) x104 s-1 Λop = 0 s-1, Λop = 5x104 s-1, Λop = 10x104 s-1, Λop = 15x104 s-1

Sources of neutron signals and neutron backgrounds GOND µPC TPC µSC 1 2 3 4 1 – µp capture signal, τ ~ 2.2 µs 2 – µZ capture bkd, τ < 2.2 µs 3 – sneaky µ, time dependent 4 – room background

muon stops and gondola hits

Neutron Energy Spectra

µp signal Requirements: good muSC/muPC entrance, good muSc/kicker timing, good TPC stop, delayed electron upstream neutron counter downstream neutron counters note sneaky µ background is larger in upstream neutron counters compared to downstream neutron counters whereas room background is roughly uniformly distributed.

µZ signal Requirements: good muSC/muPC entrance, good muSc/kicker timing, good TPC stop, delayed electron upstream neutron counter downstream neutron counters note µZ background is roughly uniformly distributed across neutron counters.

5.2 MeV neutron time-fit procedure

Start Time Dependence

Stop Time Dependence

Low Energy Bin Dependence

High Energy Bin Dependence

Detector Dependence χpdf = 1.1 High Energy Bin Dependence

Dataset Dependence χpdf = 0.3 High Energy Bin Dependence

Cuts/Methods Dependence

μ+p “neutron” time spectrum μ+p yields 6,500 neutrons and μ-p yields 82,000 neutrons for 2.2x109 good muon stops - i.e. ~8% photonuclear background

(using 1.03x109 good muon stops) μ-p/Ar data (using 1.03x109 good muon stops)

argon neutron time dependence, Nn(t) ~ ΛarN2(t) H2+Ar kinetics 1 dN1 = -N1Λ1dt dN2 = +N1ΛpArdt-N2Λ2dt where Λ1= Λo+Λs+Λppμ+ΛpAr Λ2= Λo+ΛAr singlet ΛpAr Λo+Λs+Λppμ 2 argon Λo+ΛAr argon neutron time dependence, Nn(t) ~ ΛarN2(t) Nn (t) ~ ( exp ( -Λ1t) – exp (-Λ2t) )

neutron time distributions showing overlapping stops/captures and separated stops/captures purple = neutron time spectrum, blue = neutron time spectrum for muon stops with HasEVH() true (i.e. convoluted stop/capture), green = neutron time spectrum for muon stops with IsNotAlone() true (i.e. separated stop/capture).

Separation of argon capture and muon stop muon stops with detected neutron in range 1.0 < t < 5.0 μs

Convolution of argon capture and muon stop muon stops with detected neutron in range 0 < t < 0.5 μs

muon stop characteristics for convoluted/separated stop/captures stop and capture separated stop and capture Capture can strongly effect scatter identification, significantly effect chi-squared, and mildly effect head cut, tail cut and continuous EH cuts – potentially introducing a time dependant muon stop definition.

Demo of sensitivity of muon stop definition to tail cut, head cut, ... black = IsTrack(), green = contEH >1 && head <3 && tail > 8, blue = tail > 8 magenta = contEH >0 && head <3, red = contEH >0 shows importance of tail cut in distinguishing between stops and captures and head cut in distinguishing between stops and scatters neutron time spectra tn-tμ difference between IsTrack() time spectrum and other muon stop definition time spectra.

Demo of sensitivity of muon stop definition to continuous EH. black: contEH > 0, green: contEH = 3, magneta: contEH = 4, red: contEH = 5, blue: contEH = 6 shows effect of additional EH's for overlapping stops/captures

Fit to neutron time spectrum for -0.5 < t < 24.0 mus top panel: black = data, red = fit function, green = μp contribution bottom panel: residuals

Fit to neutron time spectrum for -0.5 < t < 24.0 mus top panel: black = data, red = fit function, green = μp contribution bottom panel: residuals includes λppμ includes λAr from Fe x-rays + neutron TOF from instrumental res. + neutron TOF from pure H2 data

Fit to neutron time spectrum for -0.5 < t < 24.0 mus top panel: black = data, red = fit function, green = μp contribution bottom panel: plot of lambda1 versus lambda2 with one sigma uncertainty (red) and two sigma contour (blue).

Fit to neutron time spectrum for 0.6 < t < 24.0 mus top panel: black = data, red = fit function, green = μp contribution bottom panel: residuals

Fit to neutron time spectrum for -0.5 < t < 24.0 mus top panel: black = data, red = fit function, green = μp contribution bottom panel: residuals includes λppμ includes λAr from Fe x-rays + neutron TOF from instrumental res. + neutron TOF from pure H2 data

Fit to neutron time spectrum for 0.6 < t < 24.0 mus top panel: black = data, red = fit function, green = μp contribution bottom panel: plot of lambda1 versus lambda2 with one sigma uncertainty (red) and two sigma contour (blue).

Systematics of n/g cut, fiducial cut, energy cut, detector module, neutron TOF, ...

Systematics of n/g cut, fiducial cut, energy cut, detector module, neutron TOF, ...

Systematics of stop definition on Λ1

Systematics of stop definition on Λ2

start time scan for Λ1 (upper panel) and χ2ndf (lower panel)

Other neutron analyses

Neutron-recoil coincidences in H/Ar dataset (left) and H dataset (right) horizontal axis is recoil time (cm) and vertical axis is neutron time (ns)

Neutron time spectrum for various continuous EH's normalized to t > 5000ns black: nContEH = 1-6, red: nContEH = 1, blue: nContEH = 2, green: nContEH = 3, magenta: nContEH = 4,dash-red: nContEH = 5, dash-blue: nContEH = 6 red curve (nContEH=1) shows short lifetime compoent due to muon scatters.

Status H/Ar data: prelim. neutron determination Λ1 = 0.5237 ± 0.0021(stat) ± ? (syst) μs-1 and prelim. electron determination Λ1 = 0.5212 ± 0.0012(stat) ± ? (syst) μs-1 seem fairly consistent (Λ1 contains Λppμ and ΛpAr ). Working on determinations of systematic errors. H/Ar data: prelim. neutron determination Λ2 = 1.652 ± 0.017(stat) ± ? (syst) μs-1 and prelim. electron determination Λ2 = 1.800 ± 0.0018(stat) ± ? (syst) μs-1 seem inconsistent (Λ2 contains ΛAr ). Working on source of electron/neutron discrepancy. H data: prelim. analysis of 2.2e9 stops yielded Λeff = 0.470± 0.004(stat) ± ? μs-1 is consistent with effects of Λppμ and Λop on Λo. New analysis of data – avoiding large spark cut losses – is now underway. Other analyses: have observed neutron-recoil coincidences in the H/Ar data and the H data and may be useful as alternative determination of effects of N2//H2O contaimination. have observed neutron-μscatter coincidences and may be useful for alternative determination of μ scatter effects.