tracking/alignment status

29 Mar 2007 Tracking - Paul Dauncey 1

Tracking/Alignment Status

Paul Dauncey, Michele Faucci Giannelli, Mike Green, Anne-Marie Magnan, George Mavromanolakis, Fabrizio Salvatore, Hakan Yilmaz


Track finding/fitting changes• Checks all hits for consistent track combinations

• Previously only used first hit in each chamber

• Allows more (or less) than one track per event• Previously always one (unless a chamber had zero hits)

• Allows for missing hits on track• Previously only had four-hit tracks

• Allows for non-perfect alignment• Previously assumed all chamber placement was ideal

• Same code for CERN and DESY• Different constants but algorithm is identical• Missing layer in CERN just appears inefficient


Constants status• Have first version of tracking constants for Run 230101

• Michele has checked drift velocity against other runs• Sees values are mostly stable to ~0.0006mm/ns ~ 2%

Run Energy DC1 DC2 DC3 DC4

230097 3 0,0305 0,0284 0,0346 0,303

230098 1 0,031 0,0282 0,0386 0,0292

230099 2 0,0305 0,0284 0,035 0,0303

230100 4 0,0305 0,0282 0,0345 0,0302

230101 6 0,0303 0,0282 0,0342 0,0301

230104 5 0,0301 0,0278 0,034 0,0299

230255 1,5 0,0299 0,0278 0,0339 0,0294

• Scattering matrices found for all DESY energies• CERN runs put to zero scattering until calculated


Mokka changes• X and Y gas drift volumes physically separated

• Displaced in z by 44mm at DESY, 29mm at CERN• Split sensitive volumes into two parts• Removes correlation in energy deposits

• All SimTrackerHits in one collection• Labeled by CellID; similar to calorimeters

• Chamber numbering made more uniform• DESY was (from ECAL) DC2, DC1, DC3, DC4• CERN was (from ECAL) DC3, DC2, DC1

• Small effect on tracking• X/Y split only at 1% level

• Big effect on digitisation code and book-keeping• DESY and CERN look much more similar• Debug most of digitisation code only once


N.B. Neighbouring chambers placed 1100mm centre-to-centre

Fabrizio


Fabrizio


Digitisation changes• Seed digitisation for every event from event number

• Repeatable if debugging event in middle of run• Using ROOT gRandom; is this the standard?

• Allow more than one TDC hit per event• Previously only first SimTrackerHit per layer used

• Incorporate SimTrackerHit times• Some hits from preshowers significantly later• Can overlap with real track in space but sometimes not in time

• Add TDC noise hits• Currently flat distribution with rate matched to DESY data• Check rate of random hits picked up by tracking

• Simulate efficiency < 1• Simply drops hits randomly

• Tune hit smearing to agree better with data


Need to cross check against efficiency for track to have hits

Michele


Simulation request• Add Fabrizio’s changes before big Mokka production run

• Otherwise need to maintain many different versions• Change of coordinate system also means “fresh start” would be good

• Need high statistics samples for all DESY energies• Also electrons and pions for all CERN energies (at lower priority)

• Need to smear beam position and angle to duplicate data better• Many distributions look quite different otherwise


Want to align ECAL to beam separately• Decouples systematics of each detector

• Allows clean comparison of tracking to ECAL for position measurement

• Problem is determining average beam position = 0• Barycentre distorted by ECAL pad granularity• Difference in x and y due to x layer staggering


Hakan

Corrected using smoothing (integral) function; assumed Gaussian

Mean shifted by 1mm


Code organisation


Code status• Code structure now effectively defined

• Sent to Roman; he will try it out• If it works in his set-up, then load to cvs

• Remaining issue is database access• Working with faked up version currently• Not all runs will work until true database interface

• RunHeader: request for LCParameters information• Need run number set for MC• Also generally need

• Data or MC flag• Run start/end times• Nominal beam energy• Location (DESY, CERN, FNAL later)

• Do these exist? Can missing items be added as part of reconstruction?


Next steps• Need to reprocess at least one run of each DESY energy

• E.g. 230097 - 230104• Best done centrally to check for interference• Cross check all alignment and constants including ECAL changes

• If time, then repeat for CERN runs• Need MC to evaluate scattering matrices for every energy• Most of code is directly usable• Need to re-evaluate (carefully) alignment, drift velocity• Need to re-evaluate (roughly) efficiency, noise rate• May not converge for LCWS…

• Must ensure DESY results are available first• Minimum for LCWS; must take priority

tracking/alignment status

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