The Li C Detector Toy LDT Tracking detector

The Li. C Detector Toy (LDT) Tracking detector optimization with fast simulation VERTEX 2011, Rust M. Valentan, R. Frühwirth, M. Regler, M. Mitaroff

Li. C Detector Toy (LDT) In a nutshell • The “Li. C Detector Toy” (short “LDT”) allows investigation of the track parameter resolution via Monte Carlo, for optimizing a detector setup • Simulation of particle tracks through the track sensitive part of a collider detector with a solenoid magnetic field, including material effects • Support of measurements by semiconductor pixel and strip detectors, and a TPC • Track reconstruction by a Kalman filter, including tests of goodness of the fits • Written in Mat. Lab® (a language and IDE by Math. Works) • Version 2. 0 available for GNU Octave June 22, 2011 M. Valentan (HEPHY Vienna) 2

Li. C Detector Toy (LDT) Motivation • Compare track parameter resolutions of various detector setups, for both barrel and forward/backward regions • Optimize size and position of the track sensitive devices, and of the detector material budgets • A simple tool – easy to understand, handle and modify • Can easily be adapted to meet individual needs • Can be installed on a desktop or laptop PC • Quick results by “shorter than a coffee break” • Ideal tool for investigating the effect of local variations June 22, 2011 M. Valentan (HEPHY Vienna) 3

Li. C Detector Toy (LDT) General features • Single or double Si strip layers, pixel layers, TPC • Passive material possible • Homogeneous magnetic field (by a solenoid), rotational symmetry w. r. t. the z-axis of the detector setup • Start parameters for simulated tracks are userdefined: – Vertex position range, transverse momentum range, range of polar angle θ, number of tracks from the vertex. – Latest custom version reads start parameter from file • Output: – Track parameter resolutions – Impact parameter resolutions – Test quantities June 22, 2011 M. Valentan (HEPHY Vienna) 4

Li. C Detector Toy (LDT) Graphic User Interface (GUI) Simulation parameters Choose and display detector geometry June 22, 2011 View output M. Valentan (HEPHY Vienna) Save and load results 5

Li. C Detector Toy (LDT) Detector model • Human readable text file • Coaxial cylinder layers of arbitrary length and position • Circular plane layers, perpendicular to z-axis • Passive layers • 2 D measurement – Barrel: RΦ and z – Forward: u and v • Resolution in TPC may depend on z. June 22, 2011 M. Valentan (HEPHY Vienna) y δ 1 δ 2 v x 6

Li. C Detector Toy (LDT) 2 D and 3 D Detector Display June 22, 2011 M. Valentan (HEPHY Vienna) 7

Li. C Detector Toy (LDT) Track simulation • Exact helix track model • Data corruption by measurement errors, multiple scattering and detector inefficiencies only • Gaussian (e. g. for TPC) or uniformly distributed measurement errors • Material budget assumed to be concentrated in “thin” layers, no special treatment of electrons: – Multiple scattering: |p| conserved, correct path length traversed; – Thickness of scatterers given in radiation lengths; – Scattering angles Gaussian distributed (Rossi-Greisen-Highland’s formula); – No energy loss (by ionisation or bremsstrahlung) simulated. June 22, 2011 M. Valentan (HEPHY Vienna) 8

Li. C Detector Toy (LDT) Complex intermediate region • Arbitrary sequence of cylindric and plane detector layers June 22, 2011 M. Valentan (HEPHY Vienna) 9

Li. C Detector Toy (LDT) Track reconstruction • • No pattern recognition Single track fit by an exact Kalman filter Linear track model: Expansion point is a “reference track” Fitted parameters defined at the inside of the innermost layer: – { Φ, z, θ, β = φ-Φ, κ = ± 1/r. H } with sign(κ) = sign(dφ/ds), and corresponding 5 x 5 covariance matrix • Goodness of the fit monitored by pull quantities and χ² June 22, 2011 M. Valentan (HEPHY Vienna) 10

Li. C Detector Toy (LDT) Automatic loops Compare detector setups as function of – momentum – polar angle Several pairs of barrel and forward detector setups June 22, 2011 Several different start values for e. g. the transverse momentum M. Valentan (HEPHY Vienna) 11

Li. C Detector Toy (LDT) Automatic loops rms of Δpt/pt 2 • blue: • green: • red: June 22, 2011 ILD without SIT ILD without SET σ of projected impact These plots are direct outputs of the program! M. Valentan (HEPHY Vienna) 12

Li. C Detector Toy (LDT) Fine grained simulation mode • Normal: – Simulate many tracks – track parameter resolution from distribution • Quick & dirty: quite clean – simulate one track – track parameter resolutions from covariance matrix – enables fine scanning of detector setup June 22, 2011 M. Valentan (HEPHY Vienna) 13

Li. C Detector Toy (LDT) LDT 2. 0 for GNU Octave • Octave is free • Command line based (no GUI) • All features except for 3 D detector display • Factor 10 slower June 22, 2011 M. Valentan (HEPHY Vienna) 14

Li. C Detector Toy (LDT) LDT and other software • Successful validation against – Fullsim: Mokka/Marlin (ILD) – Fastsim: SGV (ILD) • External list of start parameters – Instead of simulating internally – Connection with event generators • Output as csv file for further analysis – Successfully tested with RAVE vertex fitting toolkit June 22, 2011 M. Valentan (HEPHY Vienna) 15

Li. C Detector Toy (LDT) Wishlist • Conical detector surfaces – > e. g. slanted part of Belle II SVD • Segmentation in RΦ – > Simulation of ladders • Simulation of e-/e+energy loss by bremsstrahlung; • Continuous multiple scattering (e. g. in front of muon detectors). June 22, 2011 M. Valentan (HEPHY Vienna) 16

Li. C Detector Toy (LDT) June 22, 2011 M. Valentan (HEPHY Vienna) 17

Li. C Detector Toy (LDT) Updated TPC resolution • TPC resolution as commented by Ron Settles: • Includes: – Constant point resolution of endplates – Term dependent on angle β between track and normal vector of detector layer – Term dependent on polar angle θ and charge spreading June 22, 2011 M. Valentan (HEPHY Vienna) 18