Small Angle Scattering in RICH

Scattering in C4F10

• Properties of C4F10
  • Density: 24.61kg/m**3 (at 20deg Celsius, 2.28bar, gas phase)
  • Density: 1516kg/m**3 (at 20deg Celsius, liquid phase)
  • Radiation Length X0 = 34.52g/cm**2 = 3200cm in the gas phase at atmospheric pressure

Dependance of the length of the radiator on the emmision angle:

Small angle scattering as a function of momentum and emmision angle:

Momentum dependance of the small scattering angle for different emmision angles:

Momentum dependance of the small scattering angle for emmision angle Theta = 50deg:

Scattering in the carbon shell

• Properites of CFK
  • Mean thickness = 2.1mm
  • Radiation length X0 = 30cm

Dependance of the small scattering ang le on momentum:

Eliptic vs rectangular matching cut

Area difference between these two cuts is:

• Rectangular cut: (2*D_phi)*(2*D_theta) = 4*D_theta*D_phi
• Eliptic cut: pi * D_theta * D_phi
• Difference = 22%

Conversion / Signal from PLUTO simulation

I have compared the 1D distribution for (theta_rich - theta_RK) (in phi it looks similar) for electrons comming from conversion and the electrons comming from all other sources. the conversion signal I have chosen according to the following condition: "pid.genInfo1==7001 || pid.genInfo1==17001 || pid.genInfo1==52001", the "real" signal is negation of the previous condition. the determination of the mean and sigma of the distribution was done with the "standard" 2-gaussian fit for momentum bins (0,150>; (150,350> and (350,1000>

in the picture "compareSim.png" you can see mean and sigma of the delta_theta distributions for the 3 momenta bins. the upper two pictures are done for electrons and positrons separately (red color "real" signal, blue conversion signal). in the lowest picture the comparision between electrons and positrons for the "real" signal is done.

as one can see, the differences in the simulation are only minor. the yields for signal and conversion are comparable (almost 1:1) for momenta (0,150>, it drops to 2:1 for momenta (350,1000> (see thetaNeg.jpg)

The sigma of the delta_theta distributions for negative tracks is:

• Signal: 0.96, 0.74, 0.54
• Conversion: 1.01, 0.81, 0.62

The sigma of the delta_theta distributions for positive tracks is:

• Signal: 1.18, 0.79, 0.60
• Conversion: 1.12, 0.88, 0.60

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in phi are the distributions much more narrower:

The sigma of the delta_phi distributions for negative tracks is:

• Signal: 0.55, 0.47, 0.47
• Conversion: 0.40, 0.53, 0.56

The sigma of the delta_phi distributions for positive tracks is:

• Signal: 0.57, 0.49, 0.50
• Conversion: 0.46, 0.51, 0.40

At this point i have to add, that i set following limits for the fit parameters: for signal is sigma in the range (0.4; 2.0) and for the background (2.0; infinity), which you can see in the fits not very well describing the distributions. in the most cases, the background had sigma of 2.0 in few cases just a touch higher than 2.0! (not a very good model :-(...), since for experimental data this limits worked very well, i decided not to introduce new limits for the fits.

I hope, the selection of the conversion was done properly (according to the documentation i hope i have not overseen something...)

-- MartinJurkovic - 29 May 2007

• Comparision delta theta (RICH - MDC) distribution of signal and conversion leptons:
  

• Phi correlation for positive leptons (signal left, conversion right):
  

• Theta correlation for positive leptons (signal left, conversion right):