Pixel digitization

 

Pixel digitisation is steered by the routine TPH2D, separate routines TPH2D_BAR and TPH2D_FB are used for the barrel and forward pixels.

All parameters used in the pixel digitisation can be adjusted by changing their values in the TITL TZ file (e.g. gtit103.tz for CMSIM103) or in the original pixel.tz file. The digitization parameters are kept under the title card DO DETX. The parameters are initially set to resonable default values. A different set of parameters is used for the barrel pixels and for the forward endcap pixels. There can be several sets of the digitization parameters, they are selected through the SETS input card.

The meaning of the pixel parameters is the following :

 
		2.		     - double sided

		7.		     - words per side

		0.		     - unused

		0.0125		 - pitch size in x

		0.0015		 - sigma in x (smearing only)

		0.		     - unused

		128.		   - number of pixel in x

		1.		     - efficiency (smearing and detailed)

		3.1E-5		 - noise fraction (smearing)

		0.		     - unused

		0.0125		 - pitch in z

		0.0015		 - sigma in z

		-1.		    - unused (emulate orthogonal strips)

		512.		   - number of pixel in z

		1.		     - efficiency (unused)

		3.1E-5		 - noise fraction (unused)

		0.		     - integration time (unsed)

		2.		     - signal gain, count/keV

		270.		   - noise amplitude in electrons (=1keV)

		4.		     - pixel threshold in noise sigma ( 4*1keV = 4keV)

		8.5		    - cluster threshold in noise sigma ( 8.5*1keV = 8.5keV)

		0.		     - cross talk (unused)

		0.		     - signal rise-time (unused)

		0.		     - signal decay-time (unused)

		255.		   - ADC maximum count (8 bit)

		34.		    - Lorentz angle in deg

		0.		     - pixel staggering flag 1=staggered, 0=not

		0.		     - cluster centroid method

		0.0007>  - diffusion charge spread in cm for a 300um Si detector

		0.0		    - depletion depth   (0. defaults to physical depth)

		0.0		    - detector tilt angle (degrees; forward only)  (blade pitch)

The pixel software is controlled by the standard input cards GEOM, SETS, DIGI, RHIT and etc.; e.g. :

 
		GEOM		 'CMSE' 3 'PXLX' 3

		SETS		 'CMSE' 0 'PXLX' 2

		DIGI		 'CMSE' 0 'PXLX' 1

		RHIT		 'CMSE' 0 'TRAK' 1

		DBUG		 'PXLX' 2

		HBOOK		 'CMSE' 1 'PXLX' 2

With the GEOM card one can choose the detector geometry. Since CMSIM version 113 the 'long-barrel' TP pixel geometry is not available any more. The default geometry is the 'short-barrel' version with the 2 sets of endcap disks. The meaning of the GEOM card for the pixel detector is the following :

• 3 - short barrel version, barrel layers at 7.2 and 11.0 cm.
• 23 - low luminosity version, barrel layers at 4.2 and 7.2 cm.
• 33 - three barrel layers.
• 1 - average geometry.
• 2 - simplified geometry.

The endcap disks are the same for versions 3, 23 and 33. The DBUG card controls the amount of debug printout information :

• 0 - no printout, only very serious errors are printed.
• 1 - some printout, warning messages about possible errors.
• 2 - detailed printout.

The HBOOK card controls the histogramming. The meaning is similar to the DBUG card. Histograms are stored in the TRAK subdirectory.