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SoLID Background Update

Zhiwen ZhaoUVa

2013/11/08

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Outline

• Intro– Estimation– Method

• PVDIS– Baffle update

• SIDIS– target collimator, target

widow, etc• Todo list

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EstimationPVDIS SIDIS He3 JPsi

Beam 50uA 15uA 3uA

Target LD2 40cm 10amg He3 40cm LH2 15cm

Window Al 2*100um Glass 2*120um Al 2*100umRadiation length (target) 5.4e-2 0.8e-3 1.7e-2

Radiation length (window) 2.25e-3 3.4e-3 2.25e-3

Radiation length (total) 5.6e-2 4.2e-3 1.9e-2

Luminosity (target) 1.27e39 3e36 1.2e37Luminosity (window) 1e37 3.7e36 6e35

Luminosity (total) 1.27e39 6.7e36 1.2e37

Comment baffle target window collimator

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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)

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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 crossection and no “weight” factor (by Yuxiang Zhao’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

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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

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Code and Result

• Code– https://hallaweb.jlab.org/wiki/index.php/Solid_Ba

ckground• Result– http://hallaweb.jlab.org/12GeV/SoLID/

download/sim/background

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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

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Baffle Design Method1. 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

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Baffle Design Method2. 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

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3. Further block photons (pi0) by adding more blockingAt 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.

Baffle Design Method

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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

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Err_Apv(%)x 0.20-

0.300.30-0.35

0.35-0.40

0.40-0.45

0.45-0.50

0.50-0.55

0.55-0.60

0.60-0.67

0.67-0.80

Baffle in pCDR 0.290 0.304 0.287 0.294 0.319 0.356 0.427 0.468 0.641

Baffle new 0.311 0.310 0.291 0.289 0.309 0.344 0.398 0.426 0.578

EC R(110,250)cm nominal acceptanceAssume 50uA, 40cm LD2Pol_beam 85%, 120 days

No trig cut

• New baffle 0.55x 5deg 5cm, 5555 baffle• Background needs to be re-evaluated• Similar level is expected from its blocking ability

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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

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SIDIS He3, pi-/e- ratio at detectorNo backgroud (HGCC)

Full backgroud (HGCC)

No backgroud (FAEC)

Full backgroud (FAEC)

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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

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backup

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sourceZ(-10,30)cmR(0,3.536)mmfor 5x5mm raster

neutral

negative

positive

Acceptance, Baffle 0.55x5degblock

EC module R(110,265)cmEC 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

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

acceptance at high x

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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