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Analysis of Beamstrahlung Pairs

This analysis focuses on the Very Forward Calorimetry and fast luminosity monitoring of beamstrahlung pairs at the ECFA Workshop in Vienna. It covers pair distributions in different geometries and magnetic field configurations. The analysis also includes the detection of electrons/photons at low angles and the shielding of the inner detector. Additionally, it explores the observables and parameters of the beamstrahlung pairs.

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Analysis of Beamstrahlung Pairs

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  1. Analysis of Beamstrahlung Pairs Christian Grah ECFA Workshop Vienna, November 14-17, 2005

  2. Outline • Very Forward Calorimetry • Fast luminosity monitoring • Analyzing pairs from beamstrahlung with BeamCal • Pair distributions in different geometries and magnetic field configurations • Summary & outlook Ch.Grah: Analysis of Beamstrahlung Pairs

  3. Very Forward Region LumiCal: 26 < θ < 82 mrad BeamCal: 4 < θ < 28 mrad PhotoCal: 100 < θ < 400 μrad Ch.Grah: Analysis of Beamstrahlung Pairs

  4. Very Forward Calorimeters • LumiCal: • Precise measurement of the luminosity by using Bhabha events (very high mechanical precision needed). • Extend coverage of the ILC detector. • Photocal • Beam diagnostics from beamstrahlung photons. • BeamCal: • Detection of electrons/photons at low angle. • Beam diagnostics from beamstrahlung electrons/positron pairs. • Shielding of Inner Detector. Ch.Grah: Analysis of Beamstrahlung Pairs

  5. BeamCal: Beam Diagnosticsand Fast Luminosity Monitoring e+ e- e+e-pairs from beamstrahlung are deflected into the BeamCal Deposited energy from pairs at z = +365 (no B-field, TESLA parameters) • 15000 e+e- per BX => 10 – 20 TeV • ~ 10 MGy per year • “fast” => O(μs) • Direct photons for q< 400 mrad (PhotoCal) Ch.Grah: Analysis of Beamstrahlung Pairs

  6. BeamCal: W-Diamond Sandwich Space for electronics Length = 30 X0 (3.5mm W + .5mm diamond sensor) ~ 15 000 channels ~1.5/2 cm < R < ~10(+2) cm Ch.Grah: Analysis of Beamstrahlung Pairs

  7. Fast Luminosity Monitoring • Pair signal included into the fast feedback system. Luminosity development during first 600 bunches of a bunch-train. Ltotal = L(1-600) + L(550600)*(2820-600)/50 L improvement for 500 GeV G.White QMUL/SLAC RHUL & Snowmass presentation position and angle scan Ch.Grah: Analysis of Beamstrahlung Pairs

  8. Beamstrahlung Pairs • Observables (examples): • total energy • first radial moment • thrust value • angular spread • E(ring ≥ 4) / Etot • E / N • l/r, u/d, f/b asymmetries • Beam parameters • σx, σy, σz and Δσx, Δσy, Δσz • xoffset • yoffset • Δx offset • Δy offset • x-waist shift • y-waist shift • Bunch rotation • N particles/bunch • (Banana shape) detector: realistic segmentation, ideal resolution, bunch by bunch resolution Ch.Grah: Analysis of Beamstrahlung Pairs

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

  10. 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: Analysis of Beamstrahlung Pairs

  11. 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: Analysis of Beamstrahlung Pairs

  12. Moving to 20mrad crossing anglewith DID Coordinate system • Boost the generated pairs (GuineaPig) according to crossing angle. • Shift center of detector to the outgoing beam. • New segmentation of the detector and blind area for the incoming beam. • Use a simplified implementation of DID field. (B.Parker & A.Seryi) Ch.Grah: Analysis of Beamstrahlung Pairs

  13. Old Geometry for 20mrad Applied the algorithm to the old 20mrad geometry, using TESLA parameters. Multi Parameter Analysis has also been done. PRELIMINARY! Ch.Grah: Analysis of Beamstrahlung Pairs

  14. 20mrad crossing angle – old geometry Sketch of BeamCal geometry. Projection of LumiCal‘s inner radius. Energy deposited in LumiCal from pairs. Here: ILC nom. beam parameters Ch.Grah: Analysis of Beamstrahlung Pairs

  15. Backgrounds • 20mrad DID • backscattering from pairs hitting the LumiCal edge Background simulations by Karsten Buesser. 20mrad solenoid Ch.Grah: Analysis of Beamstrahlung Pairs

  16. First try to fix Situation improved but still a factor of ~5 worse than in the 2mrad case. Larger increase of the aperture is necessary, which will increase the background from backscattering from the BeamCal... Study is ongoing. • Changed geometry: • increased aperture of LumiCal by 3 cm • increased outer radius of BeamCal by 3 cm • increased apertures in between accordingly Hits in TPC Ch.Grah: Analysis of Beamstrahlung Pairs

  17. Options for 20mrad under investigation 20mrad AntiDID 14mrad AntiDID DID, large aperture (Ri(LumiCal) > 13cm) DID, small aperture Ch.Grah: Analysis of Beamstrahlung Pairs

  18. Summary • A fast luminosity signal can significantly increase the luminosity. • Analyzing beamstrahlung grants access to many beam parameters. • Promising results also for 20mrad case. • Single and Multiparameter analysis is feasible. • The Very Forward region design for large crossing angles needs: • The AntiDID field configuration OR • A massively increased aperture (LumiCal’s inner radius). Ch.Grah: Analysis of Beamstrahlung Pairs

  19. Outlook • The beam diagnostics, which was based upon a FORTRAN/HBOOK code is now being ported to a GEANT4 based simulation, including: • Usage of b field map files. • Realistic detector response. • Fast shower parameterization. • Optimization of observables. • Studies on the new 20mrad geometry are ongoing. Ch.Grah: Analysis of Beamstrahlung Pairs

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