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Diagnostics with Beamstrahlung Electrons and Photons

This workshop presentation discusses beam diagnostics in the very forward region using beamstrahlung electrons and photons. It includes an overview of forward calorimetry, analysis of electron/photon pairs, and analysis of photons. The presentation also covers the analysis concept, results, and outlook for future research.

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Diagnostics with Beamstrahlung Electrons and Photons

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  1. Diagnostics with Beamstrahlung Electrons and Photons Christian Grah WORKSHOP Machine-Detector Interface at the International Linear Collider SLAC, January 6-8, 2005, Session 5: Very Forward Region

  2. Outline • Overview: Very Forward Calorimetry • Beam diagnostics from beamstrahlung • analyzing pairs (BeamCal) • analyzing photons (PhotoCal) • Summary & outlook Ch.Grah: Beamdiagnostics

  3. Very Forward Region • BeamCal: • detection of electrons/photons at low angle • beam diagnostics from beamstrahlung electrons/positron pairs • shielding of Inner Detector • Photocal (not drawn ~ downstream) • beam diagnostics from beamstrahlung photons (LumiCal: 26 < q < 82 mrad) BeamCal: 4 < q < 28 mrad PhotoCal: 100 < q < 400 μrad(recent idea, not mentioned in TESLA TDR, distance to IP > 100m) Ch.Grah: Beamdiagnostics

  4. Beamstrahlung: Fast Beam Diagnostics e+ e- • e+e-pairs from beamstrahlung are deflected into the BeamCal • 15000 e+e- per BX 10 – 20 TeV • 10 MGy per year • “fast” => O(μs) • direct photons forq< 400 mrad Ch.Grah: Beamdiagnostics

  5. Beamstrahlung Pairs • Observables (examples): • total energy • first radial moment • thrust value • angular spread • E(ring ≥ 4) / Etot • E / N • left/right, up/down, forward/backward asymmetries GeV/mm2 detector: realistic segmentation, ideal resolution bunch by bunch resolution Ch.Grah: Beamdiagnostics

  6. Analysis Concept Taylor Matrix Observables Observables Δ BeamPar nom • Beam Parameters • determine collision • creation of beamstr. • creation of e+e- pairs • guinea-pig • Observables • characterize energy distributions in detectors • analysis program 1st order Taylor-Exp. Solve by matrix inversion (Moore-Penrose Inverse) = + * Ch.Grah: Beamdiagnostics

  7. Slopes parametrization (polynomial) 1 point = 1 bunch crossing by guinea-pig slope at nom. value  taylor coefficient i,j observable j [au] beam parameter i [au] Ch.Grah: Beamdiagnostics

  8. Results of 1-Parameter Analysis Ch.Grah: Beamdiagnostics

  9. Analysis Test with non-nominal bunches: e- e+ nom. bunch size x: 575nm 575nm 553nm bunch size y: 5nm 7nm 5nm bunch size z: 290μm 320μm 300μm Ch.Grah: Beamdiagnostics

  10. Photons from Beamstrahlung • Report on analysis done by Andrei Rybin (Protvino) • Beam parameters under investigation: • beam size σx, σy, σz • beam offset x,y • waist shift x,y • Observables • Eγ (left – right) along x • Eγ (up – down) along y • Eγ (forward – backward) along z Every beam parameter analyzed separately, all others were fixed to nominal value. Ch.Grah: Beamdiagnostics

  11. Photon Distribution and Selection • Photon selection:|angle x| > 0.2 mrad|angle y| > 0.1 mrad Etot=3366.83 TeV nominal setting (550 nm x 5 nm) Ch.Grah: Beamdiagnostics

  12. Vertical Beam Waist Variation vert. waist shift > 0 vert. waist shift < 0 nominell beam parameters Ch.Grah: Beamdiagnostics

  13. Results of Analysis Parameter nom. in phot. pairs • σx 553 nm 4.2 1.5 • σy 5.0 nm 0.1 0.2 • σz 300 μm 7.5 4.3 • beam offset x 0 nm 4.0 6.0 • beam offset y 0 nm 0.16 0.4 • vertical waist shift 360 μm 14 24 Ch.Grah: Beamdiagnostics

  14. Summary • Analyzing beamstrahlung grants access to many beam parameters. • Investigating the possibility of measuring the distribution of pairs from beamstrahlung with BeamCal. • Started to analyze photon distribution at lowest angles (~100 μrad) with PhotoCal. • Started to analyze impact of small crossing angle on photon distribution. • Started comparison CAIN & GuineaPIG and saw only minor differences. Ch.Grah: Beamdiagnostics

  15. Outlook • Closer look at realistic beam simulation (started). • Analyze impact of/on the detector: • energy resolution • precision of the position measurement. Ch.Grah: Beamdiagnostics

  16. Backup Slides Ch.Grah: Beamdiagnostics

  17. Multi Parameter Analysis σx Δσx σy Δσy σz Δσz 0.3 % 0.4 % 3.4 % 9.5 % 1.4 % 0.8 % 1.5 % 0.9 % 0.3 % 0.4 % 3.5 % 11 % 0.9 % 1.0 % 11 % 24 % 5.7 % 24 % 1.6 % 1.9 % 1.8 % 1.1 % 16 % 27 % 3.2 % 2.1 % Ch.Grah: Beamdiagnostics

  18. Full Analysis Ch.Grah: Beamdiagnostics

  19. Neural Network for Photon Analysis In use: Multi layer perceptron feed-forward network 2 input nodes 1 hidden layer with 5 nodes 1 output node 200 Epochs for learning hybrid linear BFGS learning method Ch.Grah: Beamdiagnostics

  20. Example: Reconstruction of σy • Reconstruction done by Neural Network: • training vs. error • Single bunch crossing: σ(σy)= 0.113 nm Ch.Grah: Beamdiagnostics

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