1 LumiCal Optimization Simulations Iftach Sadeh Tel Aviv University Collaboration High precision design May 6 th 2008 2 Performance requirements 1.Required precision is: 2.Measure luminosity by counting the number of Bhabha events (N): 3 Design parameters 3. Layers: Number of layers - 30 Tungsten Thickness mm Silicon Thickness mm Elec. Space mm Support Thickness mm 1. Placement: 2270 mm from the IP Inner Radius - 80 mm Outer Radius mm 2. Segmentation: 48 azimuthal & 64 radial divisions: Azimuthal Cell Size mrad Radial Cell Size mrad 4 E res ( max ) E res ( min ) Choose constant which minimizes the resolution, (), but does not necessarily minimizes the bias as well. Define minimal and maximal polar angles for a shower. () Energy resolution (E res ) / Polar resolution and bias ((), ) Min{} Min{()} 5 MIP (muon) Detection Many physics studies demand the ability to detect muons (or the lack thereof) in the Forward Region. Example: Discrimination between super-symmetry (SUSY) and the universal extra dimensions (UED) theories may be done by measuring the smuon-pair production process. The observable in the figure, , denotes the scattering angle of the two final state muons. Contrasting Supersymmetry and Universal Extra Dimensions at Colliders M. Battaglia et al. (http://arxiv.org/pdf/hep-ph/ ) 6 MIP (muon) Detection Multiple hits for the same radius (non-zero cell size). After averaging and fitting, an extrapolation to the IP (z = 0) can be performed. 7 Induced charge in a single cell Energy/Charge conversion: Distribution of the deposited energy spectrum of a MIP (using 250 GeV muons): MPV = 89 keV ~ 3.9 fC. Distributions of the charge in a single cell for 250 GeV electron showers, and of the corresponding maximal cell signal (for 96 and 64 radial divisions). 8 Digitization () E res 9 Number of radial divisions () Dependence of the polar resolution, bias and subsequent error in the luminosity measurement on the angular cell-size, l . 10 Inner and outer radii Beamstrahlung spectrum on the face of LumiCal: For the preferable antiDID case R min must be larger than 7cm. ( Shown by C.Grah at the Oct 2007 FCAL meeting ) 11 Thickness of the tungsten layers () E res ( The cut matters! ) 12 Clustering - Event Sample Bhabha scattering with s = 500 GeV Energy Separation between photons and leptons: -As a function of the energy of the low- energy-particle (angular distance). -Distribution of the distance (on the face of LumiCal). 13 Clustering - Algorithm Phase I: Near-neighbor clustering in a single layer. Phase II: Cluster-merging in a single layer. 14 Clustering - Algorithm Phase III: Global-clustering. 15 Clustering - Results Merging-cuts: 16 Clustering - Geometry dependence 17 Summary Optimal parameters for the present detector- concept: 1.[R min R max ] = [80 190] mm B = 1.23 nb radial divisions (0.8 mrad radial cell-size) = 3.210 -3, = 2.210 -2 mrad L/L = 1.5 azimuthal enough for clustering, but shouldnt be lower 4.Tungsten thickness of 3.5 mm 30 layers are enough for stabilizing the energy resolution at E res 0.21 GeV. 18 Auxiliary Slides 19 Leakage through the back layers (normalized) energy deposited per layer for a 90-layer LumiCal. Distribution of the total energy for a LumiCal of 30 or 90 layers. 20 Effective layer-radius, r eff (l) / Moliere Radius, R M Shower profile - R M is indicated by the red circle. Dependence of the layer- radius on the layer number, l. R M (layer-gap) RMRM r(l) 21 Clustering - Energy density corrections Event-by-event comparison of the energy of showers (GEN) and clusters (REC). BeforeAfter 22 Clustering - Results (relative errors) Dependence on the merging-cuts of the errors in counting the number of single showers which were reconstructed as two clusters (N 12 ), and the number of showers pairs which were reconstructed as single clusters, (N 21 ). 23 Clustering - Results (event-by-event) Event-by-event comparison of the energy and position of showers (GEN) and clusters (REC). Energy 24 Clustering - Results (measurable distributions) Energy high high low Energy low high,low Energy and of high and low-energy clusters/showers. Difference in between the high and low-energy clusters/showers.