GAS TARGET BACKGROUND SUBTRACTION FOR TRITIUM/ARGON CONFIGURATION SHUJIE LI HALL A/C ANALYSIS WORKSHOP JUNE, 2017

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1 GAS TARGET BACKGROUND SUBTRACTION FOR TRITIUM/ARGON CONFIGURATION SHUJIE LI HALL A/C ANALYSIS WORKSHOP JUNE, 2017

2 GAS TARGET CELL 2017 FALL E MARATHON E x>1 SRC E (e,e p) SRC 2017 SPRING E ARGON 2

3 GAS TARGET CELL exit window 0.279mm side wall 0.5mm Length 251mm Diameter 12.5mm entrance window 0.254mm 3

4 GAS TARGET CELL * 20% density reduction at 25 ua Gas in Cell Total Window Thickness Gas Thickness Gas Rad Length Tritium 0.16 g/cm g/cm g/cm 2 Helium g/cm g/cm g/cm 2 Deuterium 0.16 g/cm g/cm g/cm 2 Argon 0.16 g/cm g/cm g/cm 2 Dummy Target: Al7075 foil x 2 Thickness: Foil 1: ± g/cm 2 Foil 2: ± g/cm 2 10 times thicker than target windows for better statistics

5 BACKGROUND SUBTRACTION 5 Goal: use dummy target data to remove the window contamination in gas target cells

6 BACKGROUND SUBTRACTION Use left-arm delta scan runs from the Ar40 experiment. Run # target Ebeam (GeV) P0 (GeV) Scattering angle 733 dummy Argon cell Cuts: trigger PID Acceptance Tracking (DR.evtypebits>>3)&1 L.cer.asum_c >500 && (L.prl1.e+L.prl2.e)>1600 abs(l.tr.tg_ph)<0.04 && abs(l.tr.tg_th)<0.06 && abs(l.tr.tg_dp)<0.05 L.tr.n==1 6

7 yield RUN 733, DUMMY RUN 734, GAS CELL target z (meter)

8 Run # target Total Window Thickness (g/cm 2 ) Gas thickness (g/cm 2 ) Prescale 733 dummy Argon cell yield RUN 733, DUMMY target z (meter) RUN 734, GAS CELL To use dummy as target windows:!! Align dummy and window positions! Check peak width! Scale by luminosity and prescale factor!

9 ENDCAP SUBTRACTION RESULTS ENDCAP SUBTRACTION yield RUN 733, DUMMY RUN 734, GAS CELL ENDCAP REMOVED target z (meter) 9

10 GAS TARGET CELL IN MONTE-CARLO SIMULATION Simulate two foils (and gas fillings) separately with FULL target and chamber configuration. Then combine results with necessary normalization. 10

11 - Plot ztar, ztari - To combine *.rzdat : call hmerge(nfile,infiles[],outfile) in Fortran - To combine *.root : hadd outfile infile1 infilen in command line 11

12 CHECK PEAK WIDTH IN MONTE-CARLO SIMULATION VDC resolution Optics resolution Single-arm SIMC as the phasespace generator Energy loss distribution Multiple scattering XEMC as the radiative cross section model 12

13 VDC RESOLUTION IN SIMULATION VDC time resolution from 5-cell events χ 2 / ndf / 12 Constant 4057 ± Mean 2.137e-10 ± 7.402e-11 Sigma 1.23e-08 ± 6.98e FWHM = σ = 29 ns 1500 resolution = 29/sqrt(5)/sqrt(4) = 6.5 ns t 12 - t 45 (sec) -6 VDC position resolution = 6.5 ns * 50 um/ns = 325 um 13

14 ELECTRON ENERGY LOSS IN SIMULATION Ionization energy loss + radiative energy loss (Collisions with atomic electrons) (Collisions with atomic nuclei) NOT in phase-space generator yet Ionization energy loss straggling follows Landau distribution Mean given by bethe-bloch Eq. 5 from Y. Mejaddem, NIM B 173 (2001)

15 MULTIPLE SCATTERING IN SIMULATION z1, z2 are two independent Gaussian distributions Deflection in two planes are independent and identically distributed 15

16 ENDCAPS IN SIMULATION Less than 2% difference in peak width (negligible) Don t need to change the shape of dummy yield distribution for target windows 16

17 DATA TO MC COMPARISON The width of downstream foil does not match DATA TO MC COMPARISON yield MC, = 6.467e-03 DATA, = 9.776e RUN 733, DUMMY MC is shifted and scaled to match DATA target z (meter) 17

18 DATA TO MC COMPARISON The 2 nd Gaussian (non-gaussian) tail is missing in simulation!!! yield 10 4 DATA TO MC COMPARISON MC DATA MC can t provide window contamination information, need dummy run target z (meter) 18

19 THANKS Barak Schmookler Douglas Higinbotham Eric Christy All Tritium students 19

20 TARGET CELL IN SIMULATION - Randomly generate N tot = vertices in each windows/gas within Ω tot = 8(10%* P 0 )(100mr)(100mr) - Include multiple scattering for entire target cell - Not include energy loss (TBD) - Only good event recorded in ntuples 20

21 TARGET CELL IN SIMULATION 21

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23 Show rootfile 23

24 RATE ESTIMATION rate = I ρ l / A Atomic mass Ωeff dσ dω dω = I ρ l / A Ωtot dσ dω ε(ω)dω # of scattering centers per area = g/cm 2 / (g/mol) * 6.02e23 atoms/mol # of electron /sec = ua / (1.602e-19 C per e - ) 24

25 RATE ESTIMATION rate = I ρ l / A Ωeff dσ dω dω = I ρ l / A Ωtot dσ dω ε(ω)dω Ωtot Ωeff ε(ω) = 0 if 1. Events generated in that phase space area can not arrive the focal plane 2. Events in that area is unphysical (i.e. w 2 <0) 25

26 RATE ESTIMATION rate = I ρ l / A Ωeff dσ dω dω = I ρ l / A Ωtot dσ dω ε(ω)dω Ωtot Ωeff rate MC = I ρ l / A N tot dσ dω ε(ω) Ω tot N tot 26

27 RATE ESTIMATION 20 ua rate MC = I ρ l / A N tot dσ dω ε(ω) Good events in simulation and XEMC Ω tot N tot efficiency # of trials in simulation (!! The single arm simulation will only record good events) Cross section tables generated from XEMC model: - from Zhihong - Included bremsstrahlung radiation - y-scaling. Use He3 fitting parameter for H3 27