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Backgrounds at FP420. IHEP/Protvino Group: Igor Azhgirey Igor Bayshev Igor Kurochkin + one post-graduate student Tools: STRUCT for particles tracking around LHC ring; MARS/IHEP for cascades simulations.. Backgrounds at FP420. Distant BG - protons only; - PowerPoint PPT Presentation
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15.07.2008 IHEP/Protvino for FP420 R&D Collaboration
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• IHEP/Protvino Group:Igor Azhgirey
Igor Bayshev
Igor Kurochkin
+ one post-graduate student
• Tools:– STRUCT for particles tracking around LHC ring;– MARS/IHEP for cascades simulations.
Backgrounds at FP420
15.07.2008 IHEP/Protvino for FP420 R&D Collaboration
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• Distant BG - protons only;- well-collimated with strong gradient on X; - mostly coincides in time with signal.
• Local BG - all particles, mostly products of electromagnetic showers;- wide angular distribution;- has a low-E fraction that may overlap several bunch crossings.
• We do not take into account particles generated in the FP420 setup material.
Backgrounds at FP420
15.07.2008 IHEP/Protvino for FP420 R&D Collaboration
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• PU – pile-up – minibias protons from IP
• DGas – protons from distant beam-gas interactions
• MC – tails of momentum cleaning halo
• LPU – “late” pile-up (2nd turn pile-up protons or protons from alien IP)
Distant Background at 420 m
15.07.2008 IHEP/Protvino for FP420 R&D Collaboration
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Background to forward detectors: FP420 Point 1Background to forward detectors: FP420 Point 1
Beam 1Beam 1 Beam 2Beam 2
Horizontal distribution of hits at FP420 for the different background sources.
Here IP1 – pile-up, IP5 – “alien” IP, MC – momentum cleaning, BG – distant beam-gas.
15.07.2008 IHEP/Protvino for FP420 R&D Collaboration
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Background to forward detectors: FP420 Point 5Background to forward detectors: FP420 Point 5
Beam 1Beam 1 Beam 2Beam 2
Horizontal distribution of hits at FP420 for the different background sources
15.07.2008 IHEP/Protvino for FP420 R&D Collaboration
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• Source – DPMJET III• Nominal LHC conditions, L = 1034
• Tracking – STRUCT code (I.Bayshev)• Beam-gas beam lifetime = 100 h• Momentum cleaning beam lifetime = 200 h• MC intensity here was suppressed with factor 0.033 (equal to the bunch length / bunch spacing ratio,
supposing uniform time distribution for MC halo)• Number of hits calculated for detector acceptance:
-27 mm < x < -dxmin
-3 mm < y < 3 mm
Distant BG Simulations
15.07.2008 IHEP/Protvino for FP420 R&D Collaboration
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Distance dx (in mm) from detector edge to the beam.
Normalization:
σinel = 84 mb27 inelastic interactions per 1 bunch crossing
Beam 1 Beam 2
10 σx 2.6 2.4
15 σx 3.9 3.6
20 σx 5.2 4.8
Detector positioning
15.07.2008 IHEP/Protvino for FP420 R&D Collaboration
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Distant BG in IP1 detectors
Beam 1 Beam 2dx>10σx dx>15σx dx>20σx dx>10σx dx>15σx dx>20σx
PU 0.445 0.372 0.318 0.441 0.372 0.321
DGas 0.017 0.008 0.005 0.028 0.011 0.006
MC* 0.922 0.002 0 0.992 0.017 0
LPU 0.145 0.035 0.002 0.075 0.002 0
Σ 1.53 0.42 0.33 1.54 0.40 0.33
Number of hits produced by distant background protons in FP420 detectors per 1 bunch crossing depending on minimal distance from the beam
15.07.2008 IHEP/Protvino for FP420 R&D Collaboration
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Distant BG in IP5 detectors
Beam 1 Beam 2dx>10σx dx>15σx dx>20σx dx>10σx dx>15σx dx>20σx
PU 0.446 0.374 0.320 0.441 0.371 0.320
DGas 0.025 0.010 0.005 0.027 0.013 0.008
MC* 0.909 0 0 0.985 0.009 0
LPU 0.014 0 0 0.263 0.090 0.039
Σ 1.39 0.38 0.33 1.72 0.48 0.37
Number of hits produced by distant background protons in FP420 detectors per 1 bunch crossing depending on minimal distance from the beam
15.07.2008 IHEP/Protvino for FP420 R&D Collaboration
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• Showers from B11B dipole magnet, caused by losses of the protons, generated in IP.
• Showers from the local beam-gas interactions.
• Secondary particles from first 2 sources, scattered on the machine equipment and tunnel walls, including low-E neutrons and photons from thermal neutrons capture.
Local Background at 420 m
15.07.2008 IHEP/Protvino for FP420 R&D Collaboration
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B11B Background
- PL/BC – average number of protons, lost on B11B, per 1 bunch crossing;
- BC/PL – average number of bunch crossings per 1 proton lost on the B11B dipole.
▼B11B BG is a rare event, but probably catastrophical for associated
bunch crossing registration (and maybe for several subsequent bunch crossings too due to slow low energy tails of cascades)
PL / BC BC / PL
IP1 Beam 1 0.0022 455
IP1 Beam 2 0.0215 47
IP5 Beam 1 0.0265 38
IP5 Beam 2 0.0485 21
15.07.2008 IHEP/Protvino for FP420 R&D Collaboration
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Background due to losses upstream FP420Background due to losses upstream FP420
15.07.2008 IHEP/Protvino for FP420 R&D Collaboration
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B11B Background
Average multiplicity of background particles crossing the acceptance of detector at 420 m (-27 mm < x < -20 σx; -3 mm < y < 3 mm) per one lost proton.
Most of the lost protons will be absorbed in B11B (14 m long) without any leakage; therefore average multiplicity for “irradiating losses” will be several times higher.
IP1 IP5
Beam 1 Beam 2 Beam 1 Beam 2
Protons 0.08 0.04 0.03 0.02
Neutrons 0.10 0.07 0.06 0.03
Pions 1.8 0.81 0.68 0.38
Photons 260 159 141 82
Electrons 9.1 3.7 3.1 2.0
15.07.2008 IHEP/Protvino for FP420 R&D Collaboration
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B11B Background
Simple estimation of the average number of B11B BG tracks in the 1st plane of the FP420 detector per one lost proton.
Fast charged hadrons (with E > 5 GeV) and electrons (with E > 10 MeV) were counted with 100% efficiency, photons (with E > 1 GeV) were taken into account with 0.75% efficiency (equal to the probability to generate e+e- pair in 1 mm of Si for 1 GeV photon).
Again, average multiplicity of hits for “irradiating losses” will be several times higher.
IP1 IP5
Beam 1 Beam 2 Beam 1 Beam 2
B11B BG Hits 8.5 3.5 2.9 1.7
15.07.2008 IHEP/Protvino for FP420 R&D Collaboration
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• To continue with B11B BG multiplicity distribution (together with Manchester);
• To produce local beam-gas BG distributions;• To prepare model of FP420 region (equipment +
tunnel) and make simulations of the low-E BG and irradiation levels for FP420 electronics e.t.c.;
• To prepare algorithm of the background sources mixing for full simulation package.
Plans