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IRC and SAC inefficiency simulation Spasimir Balev /CERN/ 14.12.2010

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Page 1: Spasimir Balev /CERN/ 14.12.2010. 2 20 mrad 3 LKr simulation: – very slow, so only events with interesting topology are fully simulated: –  + with

IRC and SAC inefficiency simulation

Spasimir Balev/CERN/

14.12.2010

Page 2: Spasimir Balev /CERN/ 14.12.2010. 2 20 mrad 3 LKr simulation: – very slow, so only events with interesting topology are fully simulated: –  + with

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Simulation of IRC

Page 3: Spasimir Balev /CERN/ 14.12.2010. 2 20 mrad 3 LKr simulation: – very slow, so only events with interesting topology are fully simulated: –  + with

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Simulation of SAC

20 mrad

Page 4: Spasimir Balev /CERN/ 14.12.2010. 2 20 mrad 3 LKr simulation: – very slow, so only events with interesting topology are fully simulated: –  + with

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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

Page 5: Spasimir Balev /CERN/ 14.12.2010. 2 20 mrad 3 LKr simulation: – very slow, so only events with interesting topology are fully simulated: –  + with

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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

Page 6: Spasimir Balev /CERN/ 14.12.2010. 2 20 mrad 3 LKr simulation: – very slow, so only events with interesting topology are fully simulated: –  + with

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CHOD multiplicity

NCHOD

NCHOD

pnn

pp0 no interactionsinteractions

4 6 8 10 12 14 16 18 20 22

4 6 8 10 12 14 16 18 20 22

pnn efficiency

IRC inefficiency

Page 7: Spasimir Balev /CERN/ 14.12.2010. 2 20 mrad 3 LKr simulation: – very slow, so only events with interesting topology are fully simulated: –  + with

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RICH multiplicity

NRICH

NRICH

pnn

pp0 no interactionsinteractions

20 22 24 26 28 30 32 34 36 38

20 22 24 26 28 30 32 34 36 38

pnn efficiency

IRC inefficiency

Page 8: Spasimir Balev /CERN/ 14.12.2010. 2 20 mrad 3 LKr simulation: – very slow, so only events with interesting topology are fully simulated: –  + with

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STRAW multiplicity

10 12 14 16 18 20 22 24 28 30

10 12 14 16 18 20 22 24 28 30

NSTRAW

NSTRAW

pnn

pp0no interactionsinteractions

pnn efficiency

IRC inefficiency

Page 9: Spasimir Balev /CERN/ 14.12.2010. 2 20 mrad 3 LKr simulation: – very slow, so only events with interesting topology are fully simulated: –  + with

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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

150

14561

59

12x

y

OUTER RINGIRCINNER RINGSAC

Page 10: Spasimir Balev /CERN/ 14.12.2010. 2 20 mrad 3 LKr simulation: – very slow, so only events with interesting topology are fully simulated: –  + with

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ComparisonsGiuseppe’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%

Page 11: Spasimir Balev /CERN/ 14.12.2010. 2 20 mrad 3 LKr simulation: – very slow, so only events with interesting topology are fully simulated: –  + with

Outer Ring (145 < R < 150 mm)

2 out of 12494 events are inefficientBoth due to PhotoNuclear interactions in RICH.Difficult to recover (rings in RICH? LAV12?)LKr efficiency for photons interacting with RICHwith R>150 mm? Inefficiency: 1.6 x 10-

4 11

event displayx, mm

y, mm

z, mm

z, mm

x, mm

y, mmELKR, MeV

p,g,m,e,others

Page 12: Spasimir Balev /CERN/ 14.12.2010. 2 20 mrad 3 LKr simulation: – very slow, so only events with interesting topology are fully simulated: –  + with

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IRC

143922 in IRC of them:17 inefficient due to PhotoNuclear interactions in RICH2 inefficient due to conversions in RICH3 inefficient due to conversions before STRAW 3

Inefficiency: 1.5 x 10-4

event displayx, mm

y, mm

z, mm

z, mm

x, mm

y, mm

ELKR, MeV

Page 13: Spasimir Balev /CERN/ 14.12.2010. 2 20 mrad 3 LKr simulation: – very slow, so only events with interesting topology are fully simulated: –  + with

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Inner Ring (2 mm)

1905 in the Inner Ring of them:1 inefficient due to Photonuclear interactions in RICH23 inefficient due to conversions IRC beam pipe

Inefficiency: 1.26%

event displayx, mm

y, mm

z, mm

z, mm

x, mm

y, mm

ESAC, MeV

Page 14: Spasimir Balev /CERN/ 14.12.2010. 2 20 mrad 3 LKr simulation: – very slow, so only events with interesting topology are fully simulated: –  + with

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Inner Ring inefficient events

EIRC (MeV)

ESAC (MeV)

Page 15: Spasimir Balev /CERN/ 14.12.2010. 2 20 mrad 3 LKr simulation: – very slow, so only events with interesting topology are fully simulated: –  + with

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SAC

27748 in SAC acceptance all of theminefficient due to conversions in:

IRC 12STRAW3 15STRAW4 7

Note:The inefficient events in IRC are always very close to the “inner ring”Effect of G4 stepping?

Inefficiency: 1.23 x 10-3

event displayx, mm

y, mm

z, mm

z, mm

Page 16: Spasimir Balev /CERN/ 14.12.2010. 2 20 mrad 3 LKr simulation: – very slow, so only events with interesting topology are fully simulated: –  + with

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SAC inefficient events

NSTRA

W

ESAC, MeV

Page 17: Spasimir Balev /CERN/ 14.12.2010. 2 20 mrad 3 LKr simulation: – very slow, so only events with interesting topology are fully simulated: –  + with

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SummaryOuter ring IRC Inner ring SAC

Photons 12494 143922 1905 27748Inefficient photons 2 22 24 34Photonuclear in RICH 2 17 1Conv. before STRAW3 2Conv. in RICH 3Conv. in IRC 23 12Conv. in STRAW3 15Conv. in STRAW4 7

Inefficiency1.6 x 10-4 1.5 x 10-4 1.3%

1.2 x 10-3

3.0 x 10-4

Total SAV efficiency 4.4 x 10-4

Page 18: Spasimir Balev /CERN/ 14.12.2010. 2 20 mrad 3 LKr simulation: – very slow, so only events with interesting topology are fully simulated: –  + with

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IRC in vacuum

Drawing by Ferdinand

IRC not centered (12 mm shift on X)

Stainless steel vessel

Vessel windows

Mylar

Page 19: Spasimir Balev /CERN/ 14.12.2010. 2 20 mrad 3 LKr simulation: – very slow, so only events with interesting topology are fully simulated: –  + with

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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

Page 20: Spasimir Balev /CERN/ 14.12.2010. 2 20 mrad 3 LKr simulation: – very slow, so only events with interesting topology are fully simulated: –  + with

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Page 21: Spasimir Balev /CERN/ 14.12.2010. 2 20 mrad 3 LKr simulation: – very slow, so only events with interesting topology are fully simulated: –  + with

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IRC/SAC inefficiencies

IRC – new design

• 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

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

Page 22: Spasimir Balev /CERN/ 14.12.2010. 2 20 mrad 3 LKr simulation: – very slow, so only events with interesting topology are fully simulated: –  + with

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pp0 background reevaluation

Page 23: Spasimir Balev /CERN/ 14.12.2010. 2 20 mrad 3 LKr simulation: – very slow, so only events with interesting topology are fully simulated: –  + with

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Photon acceptance

1 g / 2 g

SAC IRC LKR LAV MISS

SAC 1.07 x 10-6 1.16 x 10-5 2.02 x 10-2 2.45 x 10-4 6.98 x 10-6

IRC 3.20 x 10-5 9.93 x 10-2 4.67 x 10-3 7.18 x 10-5

LKR 0.72 0.15 9.51 x 10-4

LAV 2.40 x 10-4 7.13 x 10-6

MISS 0

Applied cuts:114 < ZVTX < 174 m15 < Ep+ < 35 GeVp+ in CHOD acceptancep+ outside radius 15 cm at IRCno pm decaysSelected events: 2.06 x 107

1g in IRC & 1g missed:• 1 pnn 1.22 x 109 pp0

• 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%

Page 24: Spasimir Balev /CERN/ 14.12.2010. 2 20 mrad 3 LKr simulation: – very slow, so only events with interesting topology are fully simulated: –  + with

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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(Kpnn) = 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

Page 25: Spasimir Balev /CERN/ 14.12.2010. 2 20 mrad 3 LKr simulation: – very slow, so only events with interesting topology are fully simulated: –  + with

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pp0 background breakdown [in %]

1 g / 2 g SAC IRC LKR LAV MISS

SAC 1.8 x 10-8 1.9 x 10-7 6.5 x 10-4 5.9 x 10-3 4.0 x 10-3

IRC 5.3 x 10-7 5.1 x 10-3 0.11 4.1 x 10-2

LKR 4.3 x 10-2 0.62 0.25

LAV 0.96 1.92

MISS 0

Total: 3.96%

Page 26: Spasimir Balev /CERN/ 14.12.2010. 2 20 mrad 3 LKr simulation: – very slow, so only events with interesting topology are fully simulated: –  + with

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BG = f(SAC and IRC inefficiency)

0 1 2 3 4 5 6 73

4

5

6

0 1 2 3 4 5 6 70

5

10

15

20

25

30

35

10-5 5x10-5 10-4 5x10-4 10-3 5x10-3 10-5 5x10-5 10-4 5x10-4 10-3 5x10-3

Total pp0 background % Total pp0 background %

SAC ineff. IRC ineff.

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%)

Page 27: Spasimir Balev /CERN/ 14.12.2010. 2 20 mrad 3 LKr simulation: – very slow, so only events with interesting topology are fully simulated: –  + with

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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)