TPC status Marian Ivanov

Outlook TPC performance ExB correction Alignment Nonlinearities and edge effects Drift velocity calibration

TPC - report June (2008)‏

TPC - DCA resolution  TPC resolution for fully aligned and calibrated TPC  The systematic effect  Dash line – full miscalibration  Full line Day 0  Expected Day 0 mis- calibration on the level comparable to intrinsic TPC resolution up to 3 GeV Day 0:  z ~ 1mm  y ~ 0.3 mm Full mis-calibration  z ~ 5 cm  y ~ 3 mm

TPC - DCA resolution - rphi - Cosmic  TPC local y resolution for aligned and calibrated TPC  Status –  Rectangle A side, triangle C side  Sigma – fitter sigma of residuals between tracks from upper part and lover part  In case the error uncorrelated to be divided by sqrt(2.)‏  Systematic effects estimate  A side cm  C side cm

TPC - DCA resolution - z - Cosmic  TPC local z resolution for aligned and calibrated TPC  Status –  Rectangle A side, triangle C side  Sigma – fitter sigma of residuals between tracks from upper part and lover part  In case the error uncorrelated to be divided by sqrt(2.)‏  Tracks crossing CE ~ 0.3 cm

TPC - curvature resolution Day 0:  C ~ /GeV Full mis-calibration  C ~ 0.01 (1/GeV)‏  TPC resolution for fully aligned and calibrated TPC  The systematic effect  Dash line – full miscalibration (mainly ExB)‏  Full line Day 0  Expected Day 0 mis- calibration on the level order of magnitude bellow intrinsic resolution

TPC – 1/pt resolution - Cosmic  TPC 1/pt resolution for aligned and calibrated TPC  Status –  Rectangle A side, triangle C side  Sigma – fitter sigma of residuals between tracks from upper part and lover part  In case the error uncorrelated to be divided by sqrt(2.)‏

Laser beam example  Delta rfi and delta fi (direction vector) as function of the magnetic field The interpolated value to field 0 – removed later from the ExB global fit – assumed misalignment error

ExB correction – Taylor expansion  Left side - ExB correction – Taylor expansion Ltr.fP[1]/250 – normalized z position – (z^3-1) and (z-1)‏ Ltr.fP[2] – local inclination angle – sin(fi) and cos(fi)‏ bz – magnetic field  Different color for different fi laser positions

ExB correction  Left side - ExB correction versus measurement  Right side – residuals  Implemented ExB correction map – good agreement of correction factor for symmetrized magnetic field map (after adjustment of omega-tau factor)‏

Alignment and Non-linearities  Alignment coefficients  Study of the cosmic production  events with magnetic field 5T  Y, Z misalignment on the level of microns  Correction for un-linearities necessary  Combine with Central electron plane study  Combine with laser tracks

Alignment - y  Residuals between tracklets from inner and outer sectors  sigma ~ 150 microns – shift ~ 260 microns

Alignment - z  Residuals between tracklets from inner and outer sectors  sigma ~ 220 microns – shift ~ 0.5 mm (distance to wire)‏

Alignment - phi  Residuals between tracklets from inner and outer sectors  sigma ~ 0.38 mrad – shift ~ 0.2 mrad

Alignment - theta  Residuals between tracklets from inner and outer sectors  sigma ~ 0.7 mrad – shift ~ 0.7 mrad

Laser scan – Non-linearities and Edge effect Laser beams emitted from the sector boundaries in OROC to sector boundaries in IROC ==> Difficult to disentangle edge effect in r (local x) and in r-phi )local y  Work in progress

Non-linearities study using laser tracks - Parameters to monitor The fitted curvature – global effect – (Parabola fit)‏ Edge effect

Non-linearities - Gate/skirt voltage scan – Tuning of operational conditions  The step +-20 V, drift voltage (400 V/cm)=>Effective shift 0.05cm – comparable to missalignemnt

Edge effect -Outer sectors Residuals between clusters y position and the linear extrapolation as function of the distance to the chamber edge  Left (50 V setting) – Right (90 V setting)‏

Edge gain calibration / results Fit function: f(x) = 1 - exp(-[0]*(x-[1]))‏

Edge effect - Inner sectors Residuals between clusters y position and the linear extrapolation as function of the distance to the chamber edge  Left (50 V setting) – Right (90 V setting)‏

Parabolic term Y – Nominal voltage (70 V GG)‏ Parabolic distortion from ideal line ~ 300 microns The track position resolution ~ 150 microns for infinite pt tracks Inclination angle dependent dY (cm)‏

Parabolic term Z – Nominal voltage (70 V GG)‏ Parabolic distortion form ideal line ~ 300 microns Inclination angle dependent dZ (cm)‏ dZ (cm):z (cm)‏

Z position calibration,Drift velocity and alignment

Drift velocity – calibration strategy Options: Goofie calibration + DCS values (T, P) - (ONLINE)‏ Time dependence (Goofie) - to be corrected for the T and P at TPC Space dependence DCS values (T,P) – linear fit Relative precision 0.05% (1 mm at vertex)‏ Laser Central electrode - (ONLINE)‏ Space and time dependence of drift velocity Relative precision ~ 0.01 cm/250cm ~ % Calibration using tracks – (OFFLINE)‏ Track crossing central electrode Reconstructed primary vertex position using the tracks from A and C side of the TPC Relative precision ~ 2 mm / sqrt(Nevents)‏

Drift calibration using laser tracks  Histogram of the fitted correction parameters – Delta z offset, and the drift velocity correction

Drift calibration using laser tracks - stability  Graph of the fitted correction parameters – Delta z offset, and the drift velocity correction  For some runs offset splitted by (shift by time bin) – Similar effect in CE studiies

Drift calibration using laser tracks  Histogram of the fitted correction parameters – global y correction up-middle at CE position

Drift calibration - P/T  The drift velocity depends in gas density  N/V ~ P/T  The relative change of the P ~ 2 %, in temperature ~ 0.1 K /293 K ~ 10^-4

Drift calibration - P/T resolution  Relative resolution ~ 10^-5 – 10^-4 => 250 microns  Day-night variation (TOF switching ON/OFF)‏  Depends

Drift correction Laser - P/T correction  The drift velocity correction as function of time  The drift velocity correction versus P/T relative change

Drift correction Cosmic - P/T correction  The delta Z (cm) (A-C side) form cosmic as function of time  Red color – SPD trigger, Black – ACORDE  Delta z as function of the normalized P/T

Drift velocity - Open points The time 0 offset – trigger dependent  The current implementation – only one L1 delay  Array of L1 delays (for trigger types) to be added P/T correction ~ microns precision The gas composition change in time  Information from the GOOFIE not (yet) reliable  Necessary to refit the v drift versus P/T run by run (optimally only offset)‏  Vd ~ Vdnom*corr(P/T)*corr(GC)‏

ROC temperatures

Skirt temperatures

Drift calibration - CE  CE arrival time (in mm) as function of the global y  Smaller effect as before – Smaller temperature gradient  Some non-linearities visible

Drift calibration - CE  CE arrival time (in mm) as function of the global lx (after global y subtraction)‏

Drift calibration - CE  CE arrival time (in mm) as function of the pad phi position (after global y and local x subtraction)‏  Used as time 0 correction – z alignment in the current reconstruction

- the status of overlaps in the case of ideal, residual and full misalignment ; - the status of survey, in particular the availability of alignment objects generated from survey and if they have been tested (e.g. they are reliable enough to be loaded into the OCDB for official use)... and concerning this I think you have only the alignment for the full TPC, which has already been loaded into OCDBs.