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

2. n/g discrimination

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

4. 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 = to determine χ2n and
gamma fit with ( A,, to ) varied and a = 0.00 to determine χ2g

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

6. 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

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

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

9. 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))

10. 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

11. 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

12. muon stops and gondola hits

13. Neutron Energy Spectra

14. 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.

15. 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.

16. 5.2 MeV neutron time-fit procedure

17. Start Time Dependence

18. Stop Time Dependence

19. Low Energy Bin Dependence

20. High Energy Bin Dependence

21. Detector Dependence
χpdf = 1.1
High Energy Bin Dependence

22. Dataset Dependence
χpdf = 0.3
High Energy Bin Dependence

23. Cuts/Methods Dependence

24. 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

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

26. 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) )

27. 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).

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

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

30. 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.

31. 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.

32. 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

33. 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

34. 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

35. 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).

36. 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

37. 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

38. 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).

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

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

41. Systematics of stop definition on Λ1

42. Systematics of stop definition on Λ2

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

44. Other neutron analyses

45. 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)

46. 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.

47. Status
H/Ar data: prelim. neutron determination Λ1 = ± (stat) ± ? (syst) μs-1
and prelim. electron determination Λ1 = ± (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 = ± 0.017(stat) ± ? (syst) μs-1
and prelim. electron determination Λ2 = ± (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.