Fast and Precise Luminosity Measurement at the ILC Ch.Grah LCWS 2006 Bangalore

LCWS2006, Bangalore Ch.Grah: Luminosity Measurement 2 Overview  The forward region  Luminosity measurement using LumiCal  Requirements  Systematics  Physics background  Fast luminosity monitor – BeamCal  Using the pair background signal  Beam parameter reconstruction  Summary and outlook

LCWS2006, Bangalore Ch.Grah: Luminosity Measurement 3 Forward Region – New Geometry 20mrad geometry (LDC)

LCWS2006, Bangalore Ch.Grah: Luminosity Measurement 4 Forward Region - Tasks  LumiCal (26 (43) mrad < θ < 153 mrad)  Detection of low p T em interacting particles  Measure bhahba particles with high precision  BeamCal (5.6 mrad < θ < 28 (46) mrad)  Detection of low p T em interacting particles  Measure and analyse the deposition from pairs originating from beamstrahlung.  LHCal (new idea)  Low angle hadron calorimeter  PhotoCal (not drawn on this picture)  Analyse beamstrahlung photons in the range of ~100μrad  Minimize background from backscattering from pairs. 20mrad 2mrad

LCWS2006, Bangalore Ch.Grah: Luminosity Measurement 5 Backgrounds (Old 20mrad Geometry) 20mrad DID  backscattering from pairs hitting the LumiCal edge (K.Büsser) Sketch of old BeamCal geometry. Projection of LumiCal‘s inner radius. Energy deposited in LumiCal from pairs.

LCWS2006, Bangalore Ch.Grah: Luminosity Measurement 6 LumiCal  Requirements: Events θ (rad) Bhabha scattering Energy (GeV) Events BHWIDE generated events precision by:

LCWS2006, Bangalore Ch.Grah: Luminosity Measurement 7 Detector Performance Detector performance can be included into MC. How well we have to know? R.Ingbir

LCWS2006, Bangalore Ch.Grah: Luminosity Measurement 8 Systematic Effects  Changing the detector position without Including bias & resolution Headon, 14,20 mrad X-angle outgoing beam 14 mrad X-angle detector axis 20 mrad X-angle detector axis

LCWS2006, Bangalore Ch.Grah: Luminosity Measurement 9 Compensating Systematic Effects by MC X (cm) Y (cm) 20mrad X-angle Detector axis Before correction after correction ΔL/L~10 -2 ΔL/L~10 -3 This is assuming knowing in perfect precision many parameters ! So far these effects are all considered individually, so be careful!

LCWS2006, Bangalore Ch.Grah: Luminosity Measurement 10 Physics Background  Four-lepton processes are the main source of physics background for luminosity measurement  Simulation of e + e - -> e + e - l + l - (l=e, μ, τ) background with WHIZARD  and Bhabha signal with BHLUMI  detector simulation BARBIE for track hitting detector frontface (generated track information was used) M.Pandurović/I. Božović-Jelisavčić Energy [Gev]  [deg] Energy and polar angle of background ≈10 -3 tracks/BX LUMICAL BEAMCAL LUMICAL BEAMCAL

LCWS2006, Bangalore Ch.Grah: Luminosity Measurement 11 Background Suppression  background can be effectively surpressed x [cm] y [cm] signal/background before (top) and after applying the selection cuts (bottom)

LCWS2006, Bangalore Ch.Grah: Luminosity Measurement 12 BeamCal BeamCal: 4 < θ < 28 mrad (headon)  e + e - per BX => 10 – 20 TeV  ~ 10 MGy per year  “fast” => O(μs)  Direct photons for θ < 400 μrad (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)

LCWS2006, Bangalore Ch.Grah: Luminosity Measurement 13 New Geometry 20mrad DID (R i (LumiCal) = 10.0cm at z=2270mm) (R o (BeamCal) = 16.5cm) 20mrad AntiDID (14mrad seems necessary for AntiDID) An AntiDID configuration is close to the headon/2mrad design. BUT better be prepared for both possibilities.

LCWS2006, Bangalore Ch.Grah: Luminosity Measurement 14 Fast Luminosity Monitoring  Why we need a fast signal from the BeamCal?  We can significantly improve L!  e.g. include number of pairs hitting BeamCal in the 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 Improves L by more than 12% (500GeV)!

LCWS2006, Bangalore Ch.Grah: Luminosity Measurement 15 Beamstrahlung Pair Analysis  A lot of information is stored in the energy distribution of beamstrahlung pairs hitting BeamCal.  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)

LCWS2006, Bangalore Ch.Grah: Luminosity Measurement 16 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) and/orGEANT4 1 st order Taylor- Exp. Solve by matrix inversion (Moore-Penrose Inverse)

LCWS2006, Bangalore Ch.Grah: Luminosity Measurement 17 Coefficients of the Taylor-Matrix beam parameter i [au] observable j [au] parametrization (polynomial) 1 point = 1 bunch crossing by guinea-pig slope at nom. value  taylor coefficient i,j

LCWS2006, Bangalore Ch.Grah: Luminosity Measurement 18 Analysis for nominal ILC Parameters ILCNOM, 20mrad DID Quantity Nominal Value Precision oldnew xx 553 nm xx yy 5.0 nm yy zz 300  m8.5 zz yy single parameter analysis

LCWS2006, Bangalore Ch.Grah: Luminosity Measurement 19 2mrad and 20mrad Analysis Quantity Nominal Value Precision 2mrad20mrad20mrad (2par) xx 553 nm xx yy 5.0 nm yy zz 300  m zz εyεy 40x10 -9 mrad εyεy xx yy N2x NN

LCWS2006, Bangalore Ch.Grah: Luminosity Measurement 20 BeamCal Geant4 Simulation  Need precise simulation for showering/realistic bfield map. Includes:  flexible geometry (beam crossing angle, layer thickness, variable segmentation, calorimeter tilt)  simplified DiD/antiDiD magnetic field  input – GP generated e+e- pairs  output – root tree with energy distribution in segments  1 BX ~ 2.4 GHz CPU Shower visualization Energy/Layer distribution A.Sapronov

LCWS2006, Bangalore Ch.Grah: Luminosity Measurement 21 G4 Simulation with simplified B-field σ z, μm 20mrad DID 20mrad AntiDID Deposited energy in sensor layer all layers layer8

LCWS2006, Bangalore Ch.Grah: Luminosity Measurement 22 Using Bfield Map All layers Layer 8 Energy deposited in the sensors of the forward BeamCal.

LCWS2006, Bangalore Ch.Grah: Luminosity Measurement 23 Summary  Redesign of the forward region has been done to cope with 20mrad DID (worst case).  LumiCal  Investigated physics and selection cuts to effectively reduce background.  Investigated systematic effects (displacement, resolution, bias....)...and recommend LumiCal to be centered around outgoing beam.  A luminosity measurement of ΔL/L ≈ is feasible so far.  BeamCal  Intratrain feedback of BeamCal has the potential to increase the luminosity significantly.  A fast beamdiagnostics has potential to access many beam parameters (intratrain).  This is also feasible for 20mrad.  Have set up a G4 simulation of BeamCal for realistic shower development and for realistic b-field map.

LCWS2006, Bangalore Ch.Grah: Luminosity Measurement 24 Outlook  LumiCal: extend background study by detector simulation, crossing angle  LumiCal Geant4 simulation for both design, pad and strip version, are in work  Use the BeamCal G4 simulation for the beamdiagnostics  Choose a subset of the detector information for the analysis  Detector & Readout R&D => talk by W.Wierba (DAQ session)  Find more details at: