spasimir balev /cern/ 14.12.2010. 2 20 mrad 3 lkr simulation: – very slow, so only events with...
TRANSCRIPT
IRC and SAC inefficiency simulation
Spasimir Balev/CERN/
14.12.2010
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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
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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
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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
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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
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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
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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
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12x
y
OUTER RINGIRCINNER RINGSAC
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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%
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
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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
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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
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Inner Ring inefficient events
EIRC (MeV)
ESAC (MeV)
15
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
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SAC inefficient events
NSTRA
W
ESAC, MeV
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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
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IRC in vacuum
Drawing by Ferdinand
IRC not centered (12 mm shift on X)
Stainless steel vessel
Vessel windows
Mylar
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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
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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
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pp0 background reevaluation
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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%
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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
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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%
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BG = f(SAC and IRC inefficiency)
0 1 2 3 4 5 6 73
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5
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0 1 2 3 4 5 6 70
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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%)
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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)