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IRC and SAC inefficiency simulation

IRC and SAC inefficiency simulation. Spasimir Balev /CERN/ 14.12.2010. Simulation of IRC. Simulation of SAC. 20 mrad. Simulation of LKr /CHOD/RICH/STRAW. LKr simulation: very slow, so only events with interesting topology are fully simulated: p + with 15 < E < 35 GeV

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IRC and SAC inefficiency simulation

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  1. IRC and SAC inefficiency simulation Spasimir Balev /CERN/ 14.12.2010

  2. Simulation of IRC

  3. Simulation of SAC 20 mrad

  4. Simulation of LKr/CHOD/RICH/STRAW • LKr simulation: • very slow, so only events with interesting topology are fully simulated: • p+ with 15 < E < 35 GeV • at least 1 g with R<200 cm at IRC • otherwise kill the event • CHOD simulation: • NA48 charged HOD • beam pipe added as it is in front of IRC (1 mm thick Al tube with outer radius of 70 mm) • no fins • RICH simulation: • Use Giuseppe’s beam pipe inside the RICH according to the new design (thanks!) • STRAW simulation: • Use Giuseppe’s private version with proper positioning wrt. the beam (thanks!) • LAV simulation: • Not used • The beam pipe in LAV12 responsibility region missing

  5. Energy and multiplicity thresholds • SAC and IRC • total deposited energy in Scintillator layers • EIRC > 40 MeV • ESAC > 40 MeV (double the MIP deposit) • LKr • total energy deposit (ELKR) by cells which: • are 10 cm away from the other photon • are 20 cm away from p+ • are with energy Ecell>300 MeV • Photon is seen if ELKR> 500 MeV • RICH • Number of PMTs with hits • NRICH > 25 • CHOD • count number of slabs with total energy deposit > 2 MeV • NCHOD > 8 • STRAWS • count the number of straw hits outside 5 mm radius from impact point of p+ from K decay • NSTRAW > 15

  6. CHOD multiplicity pnn pnn efficiency NCHOD 4 6 8 10 12 14 16 18 20 22 no interactions interactions pp0 IRC inefficiency NCHOD 4 6 8 10 12 14 16 18 20 22

  7. RICH multiplicity pnn pnn efficiency NRICH 20 22 24 26 28 30 32 34 36 38 no interactions interactions pp0 IRC inefficiency NRICH 20 22 24 26 28 30 32 34 36 38

  8. STRAW multiplicity pnn pnn efficiency NSTRAW 10 12 14 16 18 20 22 24 28 30 pp0 IRC inefficiency no interactions interactions NSTRAW 10 12 14 16 18 20 22 24 28 30

  9. Selection and SAV zones • 114 < ZVTX < 174 m • 15 < Ep+ < 35 GeV • p+ in CHOD acceptance • Rp+IRC > 150 mm • no p+  m+ decay • at least one photon with RIRC < 200 mm • 336340 pp0 events generated • It is required the other photon to be with RIRC>250 mm • The event is classified according to the impact photon’s impact point  OUTER RING IRC INNER RING SAC y 150 145 61 59 x 12

  10. Comparisons Giuseppe’s selection [as close as possible] • The photon is not detected if all of the following is fulfilled: • ELKR<1 GeV (with Ecell>500 MeV) • ESAC<50 MeV • EIRC<50 MeV • NCHOD≤8 • NRICH ≤25 • Inefficiency of shashlyk IRC: (3.7 ± 0.5) x 10-4 • Giuseppe’s inefficiency: (4.6 ± 0.6) x 10-4 [lead glass; not taking into account the contribution from grazing photons] • Efficiency of pnn: 94.65% “Optimized” cuts (or optimistic?) • The photon is not detected if all of the following is fulfilled: • ELKR<500 GeV (with Ecell>300 MeV) • ESAC<40 MeV • EIRC<40 MeV [double the MIP deposit] • NCHOD ≤ 8 • NRICH ≤ 25 • NSTRAW ≤ 15 • Inefficiency of IRC: (1.5 ± 0.3)x10-4 • Efficiency on pnn: 92.91%

  11. Outer Ring (145 < R < 150 mm) ELKR, MeV x, mm event display y, mm p,g,m,e,others z, mm x, mm y, mm 2 out of 12494 events are inefficient Both due to PhotoNuclear interactions in RICH. Difficult to recover (rings in RICH? LAV12?) LKr efficiency for photons interacting with RICH with R>150 mm? z, mm Inefficiency: 1.6 x 10-4

  12. IRC ELKR, MeV x, mm event display y, mm z, mm y, mm x, mm z, mm Inefficiency: 1.5 x 10-4 143922 in IRC of them: 17 inefficient due to PhotoNuclear interactions in RICH 2 inefficient due to conversions in RICH 3 inefficient due to conversions before STRAW 3

  13. Inner Ring (2 mm) ESAC, MeV x, mm event display y, mm z, mm y, mm x, mm z, mm Inefficiency: 1.26% 1905 in the Inner Ring of them: 1 inefficient due to Photonuclear interactions in RICH 23 inefficient due to conversions IRC beam pipe

  14. Inner Ring inefficient events EIRC (MeV) ESAC (MeV)

  15. SAC 27748 in SAC acceptance all of them inefficient due to conversions in: IRC  12 STRAW3  15 STRAW4  7 Note: The inefficient events in IRC are always very close to the “inner ring” Effect of G4 stepping? x, mm event display z, mm y, mm Inefficiency: 1.23 x 10-3 z, mm

  16. SAC inefficient events ESAC, MeV NSTRAW

  17. Summary

  18. IRC in vacuum Stainless steel vessel Vessel windows Drawing by Ferdinand IRC not centered (12 mm shift on X) Mylar

  19. 1g in LAV and 1g in IRC • New MC generation • In addition to the requirements on slide 4 one of the photon should be with RLKR>1400 mm • The distribution of the photons going in IRC is very asymmetric. • The photons are with E>50 GeV Photon position @ LKR

  20. IRC/SAC inefficiencies IRC – new design IRC – new design in vacuum Outer ring: < 6 x 10-5 IRC: 6.3 x 10-6 Inner ring: 0.3% SAC: 1.2 x 10-3 Total SAV inefficiency: 6.5 x 10-5 • Outer ring: < 8 x 10-5 • IRC: <10-5 • Inner ring: 1.9% • SAC: 4.6 x 10-3 • Total SAV inefficiency: 2.6 x 10-4

  21. pp0 background reevaluation

  22. Photon acceptance Applied cuts: 114 < ZVTX < 174 m 15 < Ep+ < 35 GeV p+ in CHOD acceptance p+ outside radius 15 cm at IRC no pm decays Selected events: 2.06 x 107 • 1g in IRC & 1g missed: • 1 pnn1.22 x 109pp0 • Probability (1g in IRC & 1 missed in LAVs) •  7.8 x 10-5 • Inefficiency of IRC  3 x 10-4 • Missing mass rejection factor  2 x 10-4 • pp0 background of such topology: 0.6%

  23. Calculation of pp0 background • Generated pp0 events in 114 < Z < 174 m: 7.68 x 107 • Selected (see previous slide): 2.062 x 107 • Apply weight to each photon = inefficiency of the corresponding subdetector • Total sum of the weights: 4.12 • Generated pnn events in 114 < Z < 174 m: 78533 • Selected pnn: 25859 • Missing mass cut rejection according to TD: 2x10-4 • BR(Kpnn) = 1.7 x 10-10 • Background 3.96% (we quote ~4.3%) Inefficiencies [from Giuseppe’s presentation, 11.11.10] • LAV: • E < 0.2 GeV 1 • 0.2 < E < 0.5 GeV  10-4 • E > 0.5 GeV 10-5 • LKr: • E<1 GeV 1 • 1 < E < 5.5 GeV  10-4 to 10-4 • 5.5 < E < 7.5 GeV 10-4 to 5x10-5 • 7.5 < E < 10 GeV  5x10-5 to 10-5 • E > 10 GeV  0.8 x 10-5 • SAC/IRC: • 2.9 x 10-5

  24. pp0 background breakdown [in %] Total: 3.96%

  25. BG = f(SAC and IRC inefficiency) Total pp0 background % Total pp0 background % SAC ineff. IRC ineff. 10-5 5x10-5 10-4 5x10-4 10-3 5x10-3 10-5 5x10-5 10-4 5x10-4 10-3 5x10-3 In a very pessimistic scenario: ineff(IRC) ~ 4 x 10-4 ineff(SAC) ~ 1.2 x 10-3 We get 6.3% total background from pp0 (instead of 4%)

  26. Conclusions • Still work in progress • IRC and SAC inefficiencies estimated with the new design: • inefficiency of IRC  2.6 x 10-4 • inefficiency of SAC  1.2 x 10-3 • Preliminary checks with IRC in vacuum • Possibility to refine the rejection factor by using STRAW and RICH reconstructions, and LAV • Detecting energies/cell ~300 MeV in LKr is very helpful to reduce the inefficiency at small angles • SAC and IRC performance for low energetic particles? • The pp0 background with the above inefficiencies is ~6% (wrt. ~4% with the intrinsic ones from the SAC prototype test)

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