Update on the Color Transparency Experiment e' p 16 July 2020 e - PowerPoint PPT Presentation

Update on the Color Transparency Experiment e' p 16 July 2020 e e’ John Matter p p' e 1

Summary • CT definition Complete transparency 1.0 • Optics CT onset • Target Boiling Glauber • Proton Absorption • PID e ffi ciency Q 2 ➝ Q 02 • Livetime e' • Tracking • Luminosity Scan (carbon "boiling") e • Systematic Uncertainty p • Results p' 2

Color Transparency • Color Transparency - Vanishing of final/initial state interactions in exclusive processes at large momentum transfer • Squeezing - Scattering of point-like configurations - Small transverse size ⇒ attenuated strong interaction; color-neutral singlet • Freezing - Small size maintained as the hadron passes through nucleus 3

Color Transparency • Define transparency T as the ratio Complete transparency 1.0 of the cross section for a given CT onset process on a bound nucleon to Glauber the cross section for the same process on a free nucleon Q 2 ➝ Q 02 • Glauber predicts constant T CT Experiments • CT predicts a rise in T Meson Baryon • CT onset observed in meson u u u ū d production; baryon results are ambiguous. A( 𝝆 ,di-jet): FNAL A(p,2p): BNL A(e,e’p): SLAC, JLab A( 𝛅 , 𝝆 - p): Jlab • Where is the onset? A(e, e’ 𝝆 + ): JLab A(e, e’ 𝛓 0 ): DESY & JLab 4

Previous Measurements A(e,e’p) No onset… yet? PRL 72, 1986 (1994) PRB 351, 87 (1995) PRL 80, 5072 (1998) Solid points = JLab PRC 66, 044613 (2002) Open points = other PRC 72, 054602 (2005) PRC 45, 780 (1992) 5

E12-06-107 • First 12 GeV era Hall C experiment in early 2018 • Coincidence trigger p • SHMS = proton e’ • HMS = electron • Targets • 10 cm LH 2 (Hee’p check) • 6% 12 C (production) e • Al dummy (LH 2 background) 6

E12-06-107 SHMS 12 C(e,e’p) ● E12-06-107 Q 2 SHMS central HMS angle HMS central angle [GeV 2 ] P [GeV/c] [deg] P [GeV/c] [deg] V e G 4 . 6 m a e 8.0 17.1 5.122 45.1 2.131 b 9.5 21.6 5.925 23.2 5.539 10.6 GeV beam 11.5 17.8 7.001 28.5 4.478 14.3 12.8 8.505 39.3 2.982 7

Blue = data Optics (Holly Szumila-Vance) Green = MC w/o radiative e ff ects Red = MC w/ radiative e ff ects E miss C12, Q 2 =8 GeV 2 W P miss C12, Q 2 =8 GeV 2 160 140 120 100 80 E miss [Gev] 60 40 20 0 0.3 0.2 0.1 0 0.1 0.2 0.3 − − − P miss [Gev] 8

Optics (Holly Szumila-Vance & Deepak Bhetuwal) LH2 data Missing momentum is one of our most sensitive parameters, as it depends on momentum and angle in both spectrometers 9

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 y = m ∗ I beam + b ⇒ y b = m b ∗ I beam + 1 to re-normalize data to unity y Fit slope represents ‘fractional yield loss per uA’ https://hallcweb.jlab.org/DocDB/0010/001023/001/April2018_BoilingStudies.pdf 10

SHMS Proton Absorption A = 1 − exp { − ∑ • Based on the materials in the proton’s path, I λ i } x i estimate absorption to be 8.9%* • From CT data, I estimate 8.5 ± 0.5% 1. Place tight SHMS acceptance cuts on good ep coincidences 2. Pick tight HMS-only cuts that produce the same distributions y 3. Calculate yields from ep coincidence and HMS A = 1 − Y coin singles data Y singles • For comparison, Carlos estimates 4.66 ± 0.47% in the HMS • https://hallcweb.jlab.org/DocDB/ 0010/001020/002/ProtonAbsorption_slides.pdf * https://docs.google.com/spreadsheets/d/1LeaFrQjKTuOeliKTEN8QAHqDkFCYzW18bMMjTKu1ejQ 11

PID Efficiency 
 Calculated per delta bin, then weighted ∑ i w i ϵ i ϵ = ¯ ∑ j w j n i , did ϵ i = w i = 1/ σ 2 HMS SHMS i n i , should 1.00 ϵ i 0.99 Calorimeter 1 0.98 0.98 0.97 target efficiency 0.96 0.96 C12_thick 1.00 0.94 LH2 y 0.99 Cherenkov 0.92 0.98 0.9 0.97 6 4 2 0 2 4 6 8 − − − δ 0.96 8 9.5 11.5 14.3 8 9.5 11.5 14.3 Q 2 [GeV 2 ] 12

Livetime SHMS CLT A = T pTRIG6 /S pTRIG6 100.0 • Place appropriate BCM cuts as.factor(Q2) 8 • T = number of accepted triggers 9.5 11.5 (T.shms.pTRIG1_tdcTimeRaw!=0) 14.3 CLT A 99.9 • S = scaler counts y target (P .pTRIG1.scaler) C12_thick C12_thin • Prescale factor P=1+2^(ps-1) LH2 • CLT A = P * T / S 99.8 0.003 0.004 0.005 0.006 pTRIG6 Rate [kHz] 13

Livetime SHMS LT E = T EDTM /S EDTM 102 101 as.factor(Q2) • Place appropriate BCM cuts 8 100 • T = number of accepted triggers 9.5 99 11.5 98 (T.coin.pEDTM_tdcTimeRaw!=0) 14.3 LT E 97 • S = scaler counts 96 y target (P .pEDTM.scaler) C12_thick 95 C12_thin 94 LH2 93 • LT E = T / S 92 0 25 50 75 100 pTRIG1 Rate [kHz] 14

Tracking Efficiency • Select events that should form a track HMS SHMS 1.00 (PID cut) && P.hod.betanotrack < 1.2 
 && (fewer than 21 hits per DC) 
 && P.hod.goodscinhit==1 
 0.99 target && P.hod.goodstarttime==1 efficiency Tracking C12_thick • How many did? LH2 0.98 P.dc.ntrack==1 || 
 y (P.dc.ntrack>1 && abs(P.gtr.dp)<15 
 && abs(P.gtr.y)<5 
 0.97 && abs(P.gtr.th)<0.2 
 8 9.5 11.5 14.3 8 9.5 11.5 14.3 Q 2 [GeV 2 ] && abs(P.gtr.ph)<0.2 
 && -10 < P.hod.1x.fptime < 5 
 && P.hod.1x.totNumGoodNegAdcHits<5 
 && (same two cuts for 1y, 2x, 2y)) 15

Luminosity Scan 1 Corrected Yield Charge normalized yield [#/uC] • SHMS runs 1992–2000, each with di ff erent ● 184 steady currents between 2 uA and 65 uA ● ● ● ● ● 182 • C12 0.5% target ● ● • Calculate yields and correct for detector 180 ● e ffi ciency, livetime, and prescale factor • Calculating precent change in yield per uA, we 0 20 40 60 y BCM4A Current [uA] get 0.008 ± 0.010% which is consistent with Y = m * I + b zero m = 0.014 ± 0.019 • Typical currents for CT data are 50 uA, or b = 181.79 ± 0.74 0.4% per uA 16

Luminosity Scan 2 • SHMS runs 3109–3114, each with di ff erent steady currents between 2.5 uA and 60 uA • C12 1.5% target • Calculate yields and correct for detector e ffi ciency, livetime, and prescale factor in progress • I’m still working on this, but Deepak’s result is -0.1%/uA y • Can estimate systematic uncertainty for livetime, PID, and tracking from the di ff erence between the results of these two luminosity scans • Based on Deepak’s results, we expect 0.5% systematic uncertainty due to livetime and e ffi ciency corrections 17

E12-06-107 TABLE II. Systematic Uncertainties Q 2 dependent uncertainty (%) Source 1 Spectrometer acceptance 3.0 2 Event selection 1.5 Tracking e ffi ciency 3 Radiative corrections 1.0 Live time correction Source Normalization uncertainty (%) Free cross section 2.0 Target thickness 0.5 Beam charge 1.0 Proton absorption 0.5 Total 12 0 1. Preliminary number based on agreement between Pm spectra from simc and data 2. See cut study at https://hallcweb.jlab.org/elogs/ Color+Transparency/48 3. Determined from variation in corrections for di ff erent model parameter choices 18