A Luminosity Detector for the Future Linear Collider Ronen Ingbir Prague Workshop HEP Tel Aviv University

Approach : Going back to ‘pure electron’ simulation A. Analyses of detector + background MC B. Cross checks in Geant 4 C. Energy and Angular resolution improvement. Tel Aviv University High Energy Physics Experimental Group Next Steps….. Bhabha Beamstrahlung Beam spread R&D progress report HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider

Detector Design 0.34 cm Tungsten 0.31 cm Silicon Cell Size 1.3cm*2cm> 1.3cm*6cm< ~1 Radiation length ~1 Radius Moliere HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider 15 cylinders * 24 sectors * 30 rings = cells R L 8 cm 28 cm 6.10 m

HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider Reconstruction Algorithm Events Num. We explored two reconstruction algorithms: The log. weight fun. was designed to reduce steps in a granulated detector : 1. Selection of significant cells. 2. Log. smoothing. Log. weight. E weight.

HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider Logarithmic Constant Constant value After selecting: We explored a more systematic approach. The first step is finding the best constant to use under two criteria: 1. Best resolution. 2. Minimum bias. 400 GeV

HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider Energy dependent constant The goal is to find a global weight function. Is the the log. weight constant really a constant ? Constant value

HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider Shower reconstruction Num. of Cells Num. of Sectors Num. of Cylinders Energy portion (%) En>90% What happens when we select the best log. weight constant ? Shower size Log. Weight selection Most of the information is in the selected cells.

HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider Detector optimization Num. rings 24 sectors48 sectors Comparing new results : Improvement without changing the detectors granularity.

HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider Detector optimization

HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider Beam Energy (GeV) Angular resolution Results using ‘pure electron’ simulation Can we maintain same detector properties using a more ‘real’ MC ?

HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider Azimuthal resolution Events Num. E weight. Log. weight.

HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider Log. constant Constant value 400 GeV Best constant value for is bigger then the one. Meaning: in this case best results are obtained by using ‘all the detector information’. Fixed non zero bias under investigation.

HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider Log. weight Const function 100% 33% E weight. Fixed constant dependent const Different cell size requires different weight function. Low angle small cell size smaller constant value (like in rec)

HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider Num. of Cells Num. of Sectors Num. of Cylinders Energy portion (%) En>98% Shower reconstruction What happens when we select the best log. weight constant ? Shower size Log. Weight selection Cell size determines selection mechanism

HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider Azimuthal resolution Beam Energy (GeV) Results using ‘pure electron’ simulation

HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider Energy resolution Beam Energy (GeV) Energy Resolution Acceptance cut Results using ‘pure electron’ simulation

HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider Bhabha scattering BHWIDE MC Simulation Barbie -Geant 3.21 which includes detector description for Tesla detector The MC of physical process is the output of bhabha scattering The Barbie program was given to us by Leszek Suszycki Electron energy (GeV) Bhabha Pure electrons Bhabha

HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider 250GeV 26 mrad Events selection - old approach Gaussian fit and energy calibration based tail cut Acceptance cut was based on the leakage Detector signal

HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider 33 mrad New Acceptance More systematic analyses results with new acceptance cut and improved resolution. Energy Resolution

HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider Energy balance R L Simulation distribution Distribution after acceptance and energy balance event selection Right side detector signal Left side detector signal Right signal - Left signal New approach in this study : Selecting events using information from both sides of the detector.

HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider Angular-azimuthal symmetry New approach : Selecting events which are back to back. The band cut must be wider than the relevant resolution. 1 2

HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider Events selection Acceptance cut Energy balance cut Detector signal

HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider Energy resolution - Bhabha

HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider Angular resolution - Bhabha

HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider Background studies we included in the BHWIDE a background simulation routine called CIRCE. This was suggested to us by K. Moenig Beamspread Boogert & Miller note (0.05%) (hep-ex/ ) Moenig talk in Zeuthen (0.1%) Barbie Detector simulation

HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider Background studies

HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider Selecting events in background MC CutValueResolutionRelative to Resolution Acceptance Energy balance~85% Angular symmetry ~14% Azimuthal symmetry <20%

HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider Energy resolution Ntuple No cuts With cuts Pure electrons 31 % 29%29% Bhabha 42 % 24 % Bhabha + Beamstrahlung 45 % 24 % Bhabha + Beamstrahlung + Beam spread (0.05%) 46 % 25 % Bhabha + Beamstrahlung + Beam spread (0.5%) 49 % 29 %

HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider Angular resolution

HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider Event rate: Luminosity: R&D approach: Future linear collider precision goal: Measurement approach : taking a known process – Bhabha scattering. Luminosity R&D status :

Working with both sides of the detector and looking at the difference between the reconstructed properties: (In real life we don’t have generated properties) HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider Conceptual experiment & real life algorithm In real life we have a MC to help us understand our measurements. We want to improve by a factor of 10, but maybe a 10% disagreement between data and MC is exactly the 10th factor we need. The question is how well does our MC will describe the future data ?

HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider How far are we ? How well will our MC describe the future DATA ? 11% 35% 1.’DATA’ = Reality MC 2. Real life algorithm

HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider Summary and future goals Using a more systematic approach results with improved reconstruction algorithms and improved resolutions. Our next step will be to explore further the ‘real life’ approach. Final detector design recommendation.

HEP Tel Aviv UniversityA Luminosity Detector for the Future Linear Collider