Backgrounds at FP420

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


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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


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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


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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.


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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


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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


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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


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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


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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


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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


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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


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Background due to losses upstream FP420Background due to losses upstream FP420


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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


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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


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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

Backgrounds at FP420

Documents

Transcript of Backgrounds at FP420