Studies of the Time over Threshold Gamma-ray Large Area Space Telescope Studies of the Time over Threshold Monica Brigida Fabio Gargano Nicola Giglietto Francesco Giordano Francesco Loparco Nicola Mazziotta Silvia Rainò INFN - Bari Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

Overview Study of the redundances in readout electronics (M . Brigida et al.) (2towers data only) no update Study of the ToT in track layers (F. Loparco et al.) (6towers update): Analysis of the ToT distributions Dependence of the ToT on the track parameters (θ,φ) ToT in X-view and Y-view SSD planes Study of the ToT overflows Study of the ToT in triggering layers Evaluation of the hit capture efficiency Study of ToT saturating events (N.Giglietto et al.)(2 tw no update) Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

Study of the redudancy in the TKR readout: 2 towers analysis Gamma-ray Large Area Space Telescope Study of the redudancy in the TKR readout: 2 towers analysis Monica Brigida Nico Giglietto Silvia Rainò INFN- Bari Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

Redudancy in the TKR readout Outline Data samples: 2 tower runs Event Selection Hit maps per layer Comparison of Angular distributions, Hit multiplicity and ToTs for runs readout by LEFT/RIGHT cables only with those read out from both cables Conclusions Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

Event selection and definitions Trigger from 3 consecutive layers: GemConditionWord = 2 Single tower events: GemTkrVector[tower] ≠ 0 for only one tower Single muon tracks in the TKR: TkrNumTracks = 1 Track Layers = Layers from Tkr1FirstLayer (First layer in the track) to Tkr1LastLayer (Last layer in the track) Triggering Layers = The set of 3 layers in a row issuing the trigger request Actually, we assume that Triggering Layers correspond to the ones from GltLayer to GltLayer+2 Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

Average ToTs vs layers (3) Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

ToT map (Layer 15 Tower 0) ToTs from the right side of the layer (strip 768-1535) seem to be lower than the left one Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

Conclusions No anomalies in data readout when comparing left-right and baseline run (but has to check again using calibrated ToTs) Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

Study of the Time over Threshold in the 6 towers data samples Gamma-ray Large Area Space Telescope Study of the Time over Threshold in the 6 towers data samples Fabio Gargano Francesco Loparco Nicola Mazziotta INFN - Bari Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

Muon cosθ distribution Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

Muon φ distribution Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

Raw ToT distributions in track layers Events with ToT=0 have been ruled out The ToT distributions can be fitted by Landau functions: ToT peak value  5.8μs → qmp  4 fC ? Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

ToT vs cosθ in track layers The ToT is minimum for vertical tracks and increases with θ Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

6towers update Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

Track length and projected track length z z μ μ x y ToT is proportional to maximum strip pulse amplitude Pulse amplitudes on strips are proportional to the fraction of track length belonging to their sensitive volume ToT depends on the track length projected along the strip view Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

ToT vs 1/cosθ for track layers ToT increases linearly with 1/cosθ ToT increases linearly with track length Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

ToT vs 1/cosθ for track layers (updated 6tws) ToT increases linearly with 1/cosθ ToT increases linearly with track length Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

ToT vs φ for track layers Average ToT exhibits a periodic dependence on φ (180° period) X-view layers: maxima at 90° and 270° Y-view layers: maxima at 0° and 180° Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

ToT vs φ for track layers 6tws Average ToT exhibits a periodic dependence on φ (180° period) X-view layers: maxima at 90° and 270° Y-view layers: maxima at 0° and 180° Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

ToT, track length and projected track length Study of the dependence of the ToT on cos The ToT is a function of the track length Study of the dependence of the ToT on  The ToT is a function of the projection of the track length in the SSD plane We have introduced a new variable: the ratio l/l’ Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

ToT vs l/l’ in track layers The ToT depends linearly on l/l’ and increases with the same rate Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

ToT vs l/l’ in track layers (6tws) The ToT depends linearly on l/l’ and increases with the same rate Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

ToT vs projected track length: X and Y views No significant differences in ToT vs l/l’ between X and Y view layers Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

ToT vs projected track length: X and Y views (6tw) No significant differences in ToT vs l/l’ between X and Y view layers Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

Study of ToT overflows in track layers We have studied the ToT overflows as a function of: tower planes to look for eventual noisy planes track parameters (θ, φ) to search for eventual anomalies Experimental data show that: The fraction of overflows fluctuates among the planes As expected, the fraction of overflows increases with increasing track length The fraction of overflow shows a small dependence on the φ angle for the Tower 0 data sample small difference between the average response of X-view and Y-view layers Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

ToT overflows in SSD layers The average behavior of the 4 towers is the same. The number of overflows fluctuates among the planes Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

ToT overflows in SSD layers (6tw) The average behavior of the 4 towers is the same. The number of overflows fluctuates among the planes Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

ToT overflows vs cosθ All towers exhibit the same behavior The fraction of ToT overflows increases with increasing track length Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

ToT overflows vs cosθ (6tws) All towers exhibit the same behavior The fraction of ToT overflows increases with increasing track length Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

ToT overflows vs φ Fraction of overflows in Tower 0 seems to depend on φ with a period of 90° . This effect could be caused by small differences between the average behavior of SSDs in X-view and Y-view layers Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

ToT overflows vs φ (6tws) Fraction of overflows in Tower 0 seems to depend on φ with a period of 90° . This effect could be caused by small differences between the average behavior of SSDs in X-view and Y-view layers Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

ToT in triggering layers Why studying ToT in triggering layers? To generate a trigger, a coincidence among 3 layers (6 planes) in a row is requested the probability of a noisy plane being involved in the trigger is negligible The study of hit distributions in triggering layers allows to get an estimate of the SSD hit capture efficiency Which are the triggering layers? Actually, we assume that triggering layers are the ones from GltLayer to GltLayer+2 we know that GltLayer corresponds to the first layer of the lowest “3 in a row” possible combination Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

ToT distributions in triggering layers In this case events with ToT = 0 have been included! Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

Estimate of hit capture efficiency Tower 0: 1-ε = 3.0×10-3 Tower 1: 1-ε = 0.7×10-3 Tower 2: 1-ε = 0.6×10-3 Tower 3: 1-ε = 0.5×10-3 Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

Conclusions The ToT distributions can be fitted with Landau functions The dependence of ToT on the track parameters θ and φ has been investigated The ToT increases linearly with 1/cosθ (as expected) The ToT increases linearly with l/l’ An analysis of the ToT overflows has been performed The ToT in triggering layers has been studied Hit capture efficiencies of all LAT Towers are > 99% Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

Requests & future plans ToT conversion in charge units (fC) to provide an absolute measurement of energy deposited in SSDs for all strips as a feedback for the simulations Information, in the digi files, about the hit positions (a pair of xz or yz coordinates related to each hit) to study single strip efficiencies to perform further studies: analysis of spurious hits search for stopping muons … Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

ToT saturated events: a preliminary study N.Giglietto-M. Brigida F.Giordano Science Verification, Analysis and Calibrations Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

A study on the events saturating ToTs Question: ToT values in saturation are really high energy deposit? Answer: probably yes, but has to be checked Strategy to understand this simple situation: 1) define a clean class of event (i.e low energy muons and high energy events) 2) look to the ToT distribution and compare with the whole distribution 3) event display to verify Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

Muon and shower definition We define as muon the event with the following characteristics: Single track 1 Mip deposit in calorimeter (0.6<CALMIP<1.3) Moreover we use almost vertical event (Zdir <-0.95) We define as shower a showering event characterized by: >1 Mip deposit in calorimeter or Many hits (total or outside the track) in tracker Many tracks Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

What are the keys to select shower? Showers should be characterized by many hits or many tracks or bad chi^2 in the reconstruction Here shower is defined as TRACK>1 or event with CALMIP>1.3 Showers are characterized by Many hits out of track (>40-60) or bad chi^2 in the first track or many total hits (>70?) Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

ToTs All ToTs in all active layers Fraction of ToT saturations: 0.21 % all events 0.05 % muons 0.31 % showers Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005

ToT saturations indicate really Conclusions Muons have fewer fractions of ToT saturations Showers (defined looking only hits or CAL) have a larger fraction of ToT saturations ToT saturations indicate really large energy deposits Instrument Analysis Workshop 5 – SLAC, Aug 29, 2005