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Backgrounds at FP420

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;

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Backgrounds at FP420

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  1. 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. 15.07.2008 IHEP/Protvino for FP420 R&D Collaboration

  2. Backgrounds at FP420 • 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. 15.07.2008 IHEP/Protvino for FP420 R&D Collaboration

  3. Distant Background at 420 m • 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) 15.07.2008 IHEP/Protvino for FP420 R&D Collaboration

  4. Background to forward detectors: FP420 Point 1 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. Beam 1 Beam 2 15.07.2008 IHEP/Protvino for FP420 R&D Collaboration

  5. Background to forward detectors: FP420 Point 5 Horizontal distribution of hits at FP420 for the different background sources Beam 2 Beam 1 15.07.2008 IHEP/Protvino for FP420 R&D Collaboration

  6. Distant BG Simulations • 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 15.07.2008 IHEP/Protvino for FP420 R&D Collaboration

  7. Detector positioning Distance dx (in mm) from detector edge to the beam. Normalization: σinel = 84 mb 27 inelastic interactions per 1 bunch crossing 15.07.2008 IHEP/Protvino for FP420 R&D Collaboration

  8. Distant BG in IP1 detectors 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

  9. Distant BG in IP5 detectors 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

  10. Local Background at 420 m • 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. 15.07.2008 IHEP/Protvino for FP420 R&D Collaboration

  11. 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) 15.07.2008 IHEP/Protvino for FP420 R&D Collaboration

  12. Background due to losses upstream FP420 15.07.2008 IHEP/Protvino for FP420 R&D Collaboration

  13. 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. 15.07.2008 IHEP/Protvino for FP420 R&D Collaboration

  14. 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. 15.07.2008 IHEP/Protvino for FP420 R&D Collaboration

  15. Plans • 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. 15.07.2008 IHEP/Protvino for FP420 R&D Collaboration

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