Cosmic Ray Data Analysis

1
Cosmic Ray Data Analysis
M. Ivanov M. Kowalski
2
Experimental setup
3

• Run configuration
• Ne-CO2 (90/10)
• 1024 equipped channels
• Sampling frequency 10 MHz
• Statistics 2316 cosmic events
• Anode voltage 1245 V, drift field 400 V/cm
• O2 content 50-65 ppm

Raw data, processed then by the ALTRO offline
code (thanks to Roland Bramm)
4
Data processing ALTRO applied to 10 MHz
data, then, every second signal was taken to get
5 MHz data
5
Average occupancy ? 2
This is channel occupancy, not the event one.
6
Multiplicity
Simple cluster-finder and tracking (parabola)
7
Systematics
No significant systematics in pad (r?) direction
8
Restriction to rows 10-55
9
Test data vs. simulations, physics validation -
examples
In simulations - most probable Qmax 20 ADC
(MIP) (TDR for IROC)
Diffusion and electron capture
Average ionzation is ? 1.4 MIP , but the anode
voltage lower than the GARFIELD-based
estimate (1450 V).
10
In simulations, electronics response to a single
charge is a Gaussian with a FWHM 190 ns
Drift lt 5 cm, angles close to 0
Not far from reality
11
Single-cluster analysis

• Cuts
• Number of points per track gt 20
• Number of tracks lt 5
• ? or ? lt ? 10 deg
• ?2T,P lt 0.5 (time and pad units)

• Data analyzed in six drift-length intervals
• 0 - 22.4 cm
• 22.4 - 44.8 cm
• 44.8 67.2 cm
• 67.2 89.6 cm
• 89.6 112 cm
• 112 134.4 cm

12
Space-point resolution in r?

• Extrapolation
• to 0
• to 250 cm

Diffusion over 250 cm gives 640 ?m
13
Space-point resolution in z

• Extrapolation
• to 0
• to 250 cm

Diffusion 640 ?m
14
Cluster size in pad units
The most frequent clusters are 3-pad ones
COG method is O.K.
15
Cluster size in time units
Asymmetric (2-time bin) clusters for shorth drift
COG method gives poor results
16
Why it is so?

• Design of the ROC for the real ALICE TPC took
  into
• account following facts
• There are tracks with short drift and small
  angle in pad
• direction
• There are no tracks with short drift and small
  angle in drift
• direction small diffusion means a larger
  angle and
• vice versa

In the cosmic data we register tracks with short
drift and small angle in drift direction (not
ALICE-like) for them the time response is too
narrow.
17
Conclusions

• The ROC performance is close to the designed
• The further work on the time signal
  symetrization
• is required (Marian)
• The test beam runs would be useful (details
  Joachim)
• E-field quality should be improved (on the way)
• Oxygent content should be minimized
• Temperature and preasure should be monitored