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

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

3. 15.07.2008 IHEP/Protvino for FP420 R&D Collaboration 3 PU – pile-up – minibias protons from IP DGas – protons from distant beam-gas interactions MC – tails of momentum cleaning halo LPU – “late” pile-up (2 nd turn pile-up protons or protons from alien IP) Distant Background at 420 m

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

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

6. 15.07.2008 IHEP/Protvino for FP420 R&D Collaboration 6 Source – DPMJET III Nominal LHC conditions, L = 10 34 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 < -dx min -3 mm < y < 3 mm Distant BG Simulations

7. 15.07.2008 IHEP/Protvino for FP420 R&D Collaboration 7 Distance dx (in mm) from detector edge to the beam. Normalization: σ inel = 84 mb 27 inelastic interactions per 1 bunch crossing Beam 1Beam 2 10 σ x 2.62.4 15 σ x 3.93.6 20 σ x 5.24.8 Detector positioning

8. 15.07.2008 IHEP/Protvino for FP420 R&D Collaboration 8 Distant BG in IP1 detectors Beam 1Beam 2 dx>10σ x dx>15σ x dx>20σ x dx>10σ x dx>15σ x dx>20σ x PU0.4450.3720.3180.4410.3720.321 DGas0.0170.0080.0050.0280.0110.006 MC * 0.9220.00200.9920.0170 LPU0.1450.0350.0020.0750.0020 Σ1.530.420.331.540.400.33 Number of hits produced by distant background protons in FP420 detectors per 1 bunch crossing depending on minimal distance from the beam

9. 15.07.2008 IHEP/Protvino for FP420 R&D Collaboration 9 Distant BG in IP5 detectors Beam 1Beam 2 dx>10σ x dx>15σ x dx>20σ x dx>10σ x dx>15σ x dx>20σ x PU0.4460.3740.3200.4410.3710.320 DGas0.0250.0100.0050.0270.0130.008 MC * 0.909000.9850.0090 LPU0.014000.2630.0900.039 Σ1.390.380.331.720.480.37 Number of hits produced by distant background protons in FP420 detectors per 1 bunch crossing depending on minimal distance from the beam

10. 15.07.2008 IHEP/Protvino for FP420 R&D Collaboration 10 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

11. 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) PL / BCBC / PL IP1 Beam 10.0022455 IP1 Beam 20.021547 IP5 Beam 10.026538 IP5 Beam 20.048521

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

13. 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 σ x ; -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. IP1IP5 Beam 1Beam 2Beam 1Beam 2 Protons0.080.040.030.02 Neutrons0.100.070.060.03 Pions1.80.810.680.38 Photons26015914182 Electrons9.13.73.12.0

14. 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 1 st 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. IP1IP5 Beam 1Beam 2Beam 1Beam 2 B11B BG Hits8.53.52.91.7

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