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

11/16/2005Ch.Grah: Analysis of Beamstrahlung Pairs2 Outline  Very Forward Calorimetry  Fast luminosity monitoring  Analyzing pairs from beamstrahlung with BeamCal  Pair distributions in different geometries and magnetic field configurations  Summary & outlook

11/16/2005Ch.Grah: Analysis of Beamstrahlung Pairs3 Very Forward Region LumiCal: 26 < θ < 82 mrad BeamCal: 4 < θ < 28 mrad PhotoCal: 100 < θ < 400 μrad

11/16/2005Ch.Grah: Analysis of Beamstrahlung Pairs4 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.

11/16/2005Ch.Grah: Analysis of Beamstrahlung Pairs5 BeamCal: Beam Diagnostics and Fast Luminosity Monitoring  e + e - per BX => 10 – 20 TeV  ~ 10 MGy per year  “fast” => O(μs)  Direct photons for  < 400  rad (PhotoCal) e + e - pairs from beamstrahlung are deflected into the BeamCal e+e+ e-e- Deposited energy from pairs at z = +365 (no B-field, TESLA parameters)

11/16/2005Ch.Grah: Analysis of Beamstrahlung Pairs6 BeamCal: W-Diamond Sandwich Length = 30 X 0 (3.5mm W +.5mm diamond sensor) ~ channels ~1.5/2 cm < R < ~10(+2) cm Space for electronics

11/16/2005Ch.Grah: Analysis of Beamstrahlung Pairs7 Fast Luminosity Monitoring  Pair signal included into the fast feedback system. Luminosity development during first 600 bunches of a bunch-train. L total = L(1-600) + L(550600)*( )/50 G.White QMUL/SLAC RHUL & Snowmass presentation position and angle scan L improvement for 500 GeV

11/16/2005Ch.Grah: Analysis of Beamstrahlung Pairs8 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 detector: realistic segmentation, ideal resolution, bunch by bunch resolution  Beam parameters  σ x, σ y, σ z and Δσ x, Δσ y, Δσ z  x offset  y offset  Δx offset  Δy offset  x-waist shift  y-waist shift  Bunch rotation  N particles/bunch  (Banana shape)

11/16/2005Ch.Grah: Analysis of Beamstrahlung Pairs9 Analysis Concept Observables Δ BeamPar Taylor Matrix nom = + * Beam Parameters determine collision creation of beamstr. creation of e + e - pairsguinea-pig(D.Schulte) Observables characterize energy distributions in detectorsFORTRAN analysis program (A.Stahl) 1 st order Taylor- Exp. Solve by matrix inversion (Moore-Penrose Inverse)

11/16/2005Ch.Grah: Analysis of Beamstrahlung Pairs10 beam parameter i [au] observable j [au] parametrization (polynomial) Slopes 1 point = 1 bunch crossing by guinea-pig slope at nom. value  taylor coefficient i,j

11/16/2005Ch.Grah: Analysis of Beamstrahlung Pairs11 σxσx σyσy σzσz Δσ x Δσ y Δσ z 0.3 %0.4 %3.4 %9.5 %1.4 %0.8 % 0.3 % 0.4 %3.5 % 11 % 1.5 % 0.9 % 0.9 % 1.0 % 11 % 24 % 5.7 % 24 % 1.6 % 1.9 % 1.8 % 1.1 % 16 % 27 % 3.2 % 2.1 % Multi Parameter Analysis

11/16/2005Ch.Grah: Analysis of Beamstrahlung Pairs12 Moving to 20mrad crossing angle with DID  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) Coordinate system

11/16/2005Ch.Grah: Analysis of Beamstrahlung Pairs13 Old Geometry for 20mrad QuantityNominal ValuePrecision xx 553 nm4.8nm xx 3.9nm yy 5.0 nm0.1 nm yy zz 300  m8.5  m zz 6.7  m yy 02.0nm PRELIMINARY! Multi Parameter Analysis has also been done. Applied the algorithm to the old 20mrad geometry, using TESLA parameters.

11/16/2005Ch.Grah: Analysis of Beamstrahlung Pairs14 20mrad crossing angle – old geometry Here: ILC nom. beam parameters Sketch of BeamCal geometry. Projection of LumiCal‘s inner radius. Energy deposited in LumiCal from pairs.

11/16/2005Ch.Grah: Analysis of Beamstrahlung Pairs15 Backgrounds 20mrad solenoid 20mrad DID  backscattering from pairs hitting the LumiCal edge Background simulations by Karsten Buesser.

11/16/2005Ch.Grah: Analysis of Beamstrahlung Pairs16 First try to fix  Changed geometry:  increased aperture of LumiCal by 3 cm  increased outer radius of BeamCal by 3 cm  increased apertures in between accordingly 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. Hits in TPC

11/16/2005Ch.Grah: Analysis of Beamstrahlung Pairs17 Options for 20mrad under investigation DID, small aperture DID, large aperture (R i (LumiCal) > 13cm) 20mrad AntiDID 14mrad AntiDID

11/16/2005Ch.Grah: Analysis of Beamstrahlung Pairs18 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).

11/16/2005Ch.Grah: Analysis of Beamstrahlung Pairs19 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.