1. First results from prototype measurements
Susanna Costanza
Pavia Group & IKP-Jülich
PANDA Collaboration Meeting, GSI – 9 Mar 2010

2. S. Costanza PANDA Collaboration Meeting – GSI, 9/03/2010
Outline
Description of the experimental setup
Aim of this work
TDC spectra analysis
Tracking method steps
Results
Mean residuals distribution
Residuals in dr intervals
Resolution curve
Summary & Outlook
S. Costanza PANDA Collaboration Meeting – GSI, 9/03/2010

3. S. Costanza PANDA Collaboration Meeting – GSI, 9/03/2010
STT FZJ
Designed for COSY-TOF and PANDA (P. Wintz)
ELECTRONICS:
Standard existing electronics
64 channels with CMP16 + F1-TDC
64 channels with Fast QDC (160 MHz, 240 MHz in prep)
from COSY
S. Costanza PANDA Collaboration Meeting – GSI, 9/03/2010
DESIGN
4 x (16 x 2) = 128 straws
(4 self-supporting double-layers, 32 tubes each)
1.5 m long
30 mm wall thickness (aluminised mylar)
20 mm anode wire
Different gas mixtures (ArCO2 (90/10) - ArC2H6 (80/20))
Operating at overpressure

4. STT prototype @ FZJ (III)
Aim:
Measurement of particle energy losses
Construction of dE/dx curves
Experimental check of the achievable energy resolution for the PANDA STT
Hints for optimal selection of the final read-out electronics for STT
Knowledge about “environmental” conditions (noise suppression, pressure stability, …)
Beta particles from Sr source
ArCO2 (90/10)
16 tubes
S. Costanza PANDA Collaboration Meeting – GSI, 9/03/2010
Sr90 radioattivo, decade beta con decay energy = MeV
s < 15 %
K. Pysz, H. Ohm, V. Serdyuk, P. Kulessa, P. Wintz
PANDA Collaboration FZJ – Sept 2009

5. Aim of the present work:
First results for dE/dx are already promising
Deeper investigation of these data
2 different readout information: TDC and QDC
Work packages:
calibration of the straw (position and isochrone parametrization)
reconstruction of cosmic tracks
dE/dx analysis using full QDC information (time signal, signal amplitude and integrated charge)
track length information in the gas
Data sets:
ArCO2 (90/10)
ArC2H6 (80/20)
Comparison between TDC and QDC information
i.e. isochrone parametrization
S. Costanza PANDA Collaboration Meeting – GSI, 9/03/2010
Sr90 radioattivo, decade beta con decay energy = MeV

6. S. Costanza PANDA Collaboration Meeting – GSI, 9/03/2010
Typical TDC spectrum
1 tube with TDC
ArCO2 (90/10)
1 bar overpressure
1700 V
S. Costanza PANDA Collaboration Meeting – GSI, 9/03/2010

7. S. Costanza PANDA Collaboration Meeting – GSI, 9/03/2010
From TDC spectra…
Conversion TDC counts  ns
Fitting of the single spectra
Offset correction for single spectra
Sum of all the spectra
1 ch = ns
ATLAS Coll., NIM A 523 (2004)
P1: uncorrelated noise
P3 & P4: describe the spectrum shape
P5: t0
P6: tmax
P7: slope of the leading edge
P8: slope of the trailing edge
S. Costanza PANDA Collaboration Meeting – GSI, 9/03/2010
fit
t0, tmax
Noise level

8. … to isochrone calibration
r-t relation obtained in the hypotesis of uniform illumination over the tube volume:
3rd order polynomium
p e-01
p e-02
p e-04
p e-07
S. Costanza PANDA Collaboration Meeting – GSI, 9/03/2010

9. Tracking method PREFIT:
minimization of the perpendicular distances of a set of N points
(xi, yi) from the best-fit line
The function to be minimized is:
where
(xi, yi) = centres of the firing tubes
S. Costanza PANDA Collaboration Meeting – GSI, 9/03/2010
Since the absolute value function does not have continuous derivatives, minimizing R is not amenable to analytic solution.
The square of the perpendicular distances is minimized instead:

10. S. Costanza PANDA Collaboration Meeting – GSI, 9/03/2010
Tracking method (II)
FILTERING after the prefit:
Filter for bad events:
Cut on the number of hits (5 minimum required)
Cut on the mean distance of the centres of the firing tubes to the prefit line
Filter for spurious hits: cut on the distance from the prefit
MINUIT FIT:
Fit of the following c2:
where:
are the residuals
are the drift radii obtained from the r-t relation previously derived
S. Costanza PANDA Collaboration Meeting – GSI, 9/03/2010
FILTERING after the Minuit fit:
Filter for spurious hits: cut on the residual value

11. From the eventDisplay…
S. Costanza PANDA Collaboration Meeting – GSI, 9/03/2010

12. Mean residuals distribution
PRELIMINARY RESULTS!!!
Just 1 iteration
m = mm
s = mm
S. Costanza PANDA Collaboration Meeting – GSI, 9/03/2010

13. Residual distributions in single intervals
s = mm
S. Costanza PANDA Collaboration Meeting – GSI, 9/03/2010
s = mm

14. S. Costanza PANDA Collaboration Meeting – GSI, 9/03/2010
Resolution curve
Data
Fit
PRELIMINARY RESULTS!!!
Just 1 iteration
S. Costanza PANDA Collaboration Meeting – GSI, 9/03/2010

15. S. Costanza PANDA Collaboration Meeting – GSI, 9/03/2010
Summary & Outlook
Isochrone calibration from TDC spectra
Track reconstruction implemented
Preliminary mean resolution of ~ 190 mm
already after the first iteration
With non-dedicated time resolution readout (CMP16)
Track length correction to be used in dE/dx analyses
Set up the QDC analyses
Determine the dE/dx resolution
Compare different data sets
Comparison of experimental results with simulations
S. Costanza PANDA Collaboration Meeting – GSI, 9/03/2010
Thank you!