r6  19 May 2006  14:18  QuirinWeitzel  r5  19 May 2006  07:51  QuirinWeitzel  

Purpose 
Purpose 

Tracking: The TPC is discussed as a solution for the outer tracking within the target spectrometer. The required momentum resolution is ~1%, the required vertex resolution ~150um in the xy plane and < 1cm in z direction. 
Tracking: The TPC is discussed as a solution for the outer tracking within the target spectrometer. The required momentum resolution is ~1%, the required vertex resolution ~150um in the xy plane and < 1cm in z direction. 

PID: In the momentum range below ~1GeV and above ~2GeV the TPC provides information for particle identification within the target spectrometer. Especially for particles with momenta below ~1GeV this is of great help for the overall PID performance and to supplement the information from the barrel DIRC. 
PID: In the momentum range below ~1GeV and above ~2GeV the TPC provides information for particle identification within the target spectrometer. Especially for particles with momenta below ~1GeV this is of great help for the overall PID performance and to supplement the information from the barrel DIRC. 

Working principle (in short) 
Working principle (in short) 

General: 3D tracking device  charged particles ionize detector gas  electric field along cylinder axis separates positive gas ions from electrons  primary electrons drift towards readout anode  gas amplification done by several GEM foils  ungated, continuous operation mode due to HESR beam properties  intrinsic ion feedback suppression by GEM foils  continuous data readout within PANDA DAQ  parallel online data reduction and processing (including tracking) 
General: 3D tracking device  charged particles ionize detector gas  electric field along cylinder axis separates positive gas ions from electrons  primary electrons drift towards readout anode  gas amplification done by several GEM foils  ungated, continuous operation mode due to HESR beam properties  intrinsic ion feedback suppression by GEM foils  continuous data readout within PANDA DAQ  parallel online data reduction and processing (including tracking) 

PID: performed via measurement of mean energy loss per track length (dE/dx), described by BetheBlochformula, in combination with (obligatory) momentum measurement  PANDA TPC offers to do ~50100 (fluctuating) energy loss measurements per track  truncated mean algorithm used to get rid off Landau tail and to calculate mean 
PID: performed via measurement of mean energy loss per track length (dE/dx), described by BetheBlochformula, in combination with (obligatory) momentum measurement  PANDA TPC offers to do ~50100 (fluctuating) energy loss measurements per track  truncated mean algorithm used to get rid off Landau tail and to calculate mean 

Important values 
Important values 

Geometry:inner radius: 15cm, outer radius: 42cm, length: 150cm, gas volume: 700l, 2 separate chambers (due to target pipe) 
Geometry:inner radius: 15cm, outer radius: 42cm, length: 150cm, gas volume: 700l, 2 separate chambers (due to beam pipe) 

Material budget: ~1.5% X/X0 
Material budget: ~1.5% X/X0 

Detector gas: Ne/CO2 (90/10, maybe admixture of CH4), gas gain: several 1000 
Detector gas: Ne/CO2 (90/10, maybe admixture of CH4), gas gain: several 1000 

Operation: drift field: 400V/cm, 2x2mm pads (100000) 
Operation: drift field: 400V/cm, 2x2mm pads (100000) 

First estimates and simulations (obtained from old PANDA framework and preliminary) 
First estimates and simulations (obtained from old PANDA framework and preliminary) 

Data were generated based on an event generator which shoots p, K, pi, mu and e (plus antiparticles) isotropically through the TPC. All tracks come from the IP, with momenta between 0.2 and 4GeV/c. Tracks are divided into 6mm pieces, for each the energy loss is calculated resulting in 50100 measurements depending on track length. Upper 40% are discarded and mean dE/dx calculated (truncated mean). The spread of the these dE/dx values for certain p bins is fitted with a Gaussian and the dE/dx resolution is defined as the corresponding sigma. 
Data were generated based on an event generator which shoots p, K, pi, mu and e (plus antiparticles) isotropically through the TPC. All tracks come from the IP, with momenta between 0.2 and 4GeV/c. Tracks are divided into 6mm pieces, for each the energy loss is calculated resulting in 50100 measurements depending on track length. Upper 40% are discarded and mean dE/dx calculated (truncated mean). The spread of the these dE/dx values for certain p bins is fitted with a Gaussian and the dE/dx resolution is defined as the corresponding sigma. 

The separation power between two particles is defined as: 2*I1  I2 / (sigmaI1/I1 + sigmaI2/I2), where I stands for the dE/dx of the respective particle. A constant dE/dx resolution of 5% was assumed. 
The separation power between two particles is defined as: 2*I1  I2 / (sigmaI1/I1 + sigmaI2/I2), where I stands for the dE/dx of the respective particle. A constant dE/dx resolution was assumed. 

Note: For all the simulation results shown here the gas density value was a factor of 1.5 to high. Therefore we expect the performance to be a bit worse. For example the dE/dx resolution will change from ~5% to ~7%. Simulations will be repeated with the new PANDA framework as soon as possible. 
Note: For all the simulation results shown here the gas density value was a factor of 1.5 to high. Therefore we expect the performance to be a bit worse. For example the dE/dx resolution will change from ~5% to ~7%. Simulations will be repeated with the new PANDA framework as soon as possible. 

 QuirinWeitzel  10 May 2006 
 QuirinWeitzel  10 May 2006 




r6  19 May 2006  14:18  QuirinWeitzel  r5  19 May 2006  07:51  QuirinWeitzel  