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SoLID Background Update

SoLID Background Update. Zhiwen Zhao UVa 2013/11/08. Outline. Intro Estimation Method PVDIS Baffle update SIDIS target collimator, target widow, etc Todo list. Estimation. Method. EM background

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SoLID Background Update

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  1. SoLID Background Update Zhiwen Zhao UVa 2013/11/08

  2. Outline • Intro • Estimation • Method • PVDIS • Baffle update • SIDIS • target collimator, target widow, etc • Todo list

  3. Estimation

  4. Method • EM background • Build all parts with realistic material in GEMC, turn on general Geant4 physics list “QGSP_BERT_HP”, throw electrons into SoLID targets • Results dominated by low energy photons and electrons. EM process should be fairly accurate • Hadrons produced also, but not used for later study because Geant4 doesn’t have all necessary crosssections • Neutrons including low energy ones produced also, hasn’t been used for study yet. (Lorenzo showed Geant4 has similar results with FLUKA)

  5. Method • Hadron background • pi/K/p generated from Wiser fit, more accurate at DIS region, but extends to low energy region also • With a distribution according to crossectionand no “weight” factor (by YuxiangZhao’s modified “eicRate” code), they are thrown into SoLID from their simulated vertices • SoLID has realistic material in GEMC and physics list “QGSP_BERT_HP” is turned on. It’s the same condition like in EM background study. • A lot of secondary hadrons are produced. Also many low energy photons, electrons and neutrons • The primary particle “kind” always dominates unless it decays like pi0 or Ks where decay products donimates

  6. Method • e(DIS) and e(ES) • e(DIS) generated from CTEQ fit by code “eicRate” • e(ES) generated from formula by code “eicRate” • Only have even distribution with a “weight” factor. Doesn’t have distribution same as crosssection and no “weight” factor yet • Don’t expect it as a big source of background • But it’s need for energy loss and radiation correction study

  7. Code and Result • Code • https://hallaweb.jlab.org/wiki/index.php/Solid_Background • Result • http://hallaweb.jlab.org/12GeV/SoLID/download/sim/background

  8. PVDIS, baffle design • What we have learned • It’s not easy to have code automatically optimize to let high x e(DIS) pass, block position pions and straight photons at same time • 6 baffle planes is not enough to reduce secondary pion background to the level trigger can take, 11+1 planes works • 1st baffle inner radius needs to be large to reduce background like moller electron. We use 5cm now • Beamline at downstream should have as large opening angle as position

  9. Baffle Design Method 1. Study phi turning from eDIS events at every baffle plate front face. Allow 96% (2-98% of phi change) of rate weighted events with 0.55<x<0.8 and p>1.5GeV to pass through. This define the opening for a very narrow phi slice of eDIS events from the target Rate VS phi turning At 20 blocks of 1st baffle plane

  10. Baffle Design Method 2. Enlarge this opening by 5o where positive leaks start to appear, expect 40%=5/12 acceptance for these eDIS events Example of 11 baffle planes

  11. Baffle Design Method 3. Further block photons (pi0) by adding more blocking At the last (11th) baffle, negative and neutral mixes with each other at low phi where high x and high P events are. Block photon here will harm eDIS acceptance at high x At EC, negative and neutral split well from each other due to the additional flight path. Photon block at EC works better.

  12. EC photon block • EC coverage R(110,265)cm • EC photon block • 30 of them • R(105-200)cm • 5cm(8*X0) thick lead, reduce photon energy by 1 order • We have 19cm in Z between Cherenkov and EC for the photon block and 2 GEM planes Illustration only

  13. Assume 50uA, 40cm LD2 Pol_beam 85%, 120 days EC R(110,250)cm nominal acceptance Err_Apv(%) No trig cut • New baffle 0.55x 5deg 5cm,5555baffle • Background needs to be re-evaluated • Similarlevel is expected from its blocking ability

  14. SIDIS He3 • A pair of Tungsten collimators are optimized to block hadrons from target windows into forward angle detectors • The acceptance shown with and without the collimator is similar to the SIDIS proposal • A full background study is done • EC performance is under study. Single trigger rate will be checked

  15. SIDIS He3, pi-/e- ratio at detector No backgroud (HGCC) No backgroud (FAEC) Full backgroud (FAEC) Full backgroud (HGCC)

  16. Todo list Next iteration of • PVDIS: background with new baffle • SIDIS He3: figure of merit check to further optimize the target collimator • SIDIS proton: study sheet of flame and its impact on detectors • JPsi: full background study

  17. backup

  18. Acceptance, Baffle 0.55x5degblock negative source Z(-10,30)cm R(0,3.536)mm for 5x5mm raster neutral • EC module R(110,265)cm • EC photon block (“baffle 3.5degblock”) • 30 of them • R(105-205)cm • Start from 2.8 degree and width 4 degree. • 5cm(8*X0) thick lead, hope to reduce photon energy by 1 order positive

  19. eDIS acceptance comparison at EC “0.55x 5deg” and “0.55x 5deg block” has best acceptance at high x

  20. eDIS rate comparison at EC “0.55x 5deg” and “0.55x 5deg block” has no low mom leak which could leads to high trig rate

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