Base class for digitizers. More...

#include <FMD/AliFMDDigitizer>

Inheritance diagram for AliFMDBaseDigitizer:

Public Member Functions
	AliFMDBaseDigitizer ()

	AliFMDBaseDigitizer (AliDigitizationInput *digInp)

	AliFMDBaseDigitizer (const Char_t name, const Char_t title)

virtual	~AliFMDBaseDigitizer ()

virtual Bool_t	Init ()

void	SetShapingTime (Float_t B=10)

Float_t	GetShapingTime () const

void	SetStoreTrackRefs (Bool_t store=kTRUE)

Bool_t	IsStoreTrackRefs () const

Public Member Functions inherited from AliDigitizer
	AliDigitizer (const Text_t name="AliDigitizer", const Text_t title="AliDigitizer")

	AliDigitizer (AliDigitizationInput manager, const Text_t name="AliDigitizer", const Text_t *title="AliDigitizer")

	AliDigitizer (const AliDigitizer &dig)

AliDigitizer &	operator= (const AliDigitizer &dig)

virtual	~AliDigitizer ()

virtual void	Digitize (Option_t *option)=0

Bool_t	GetRegionOfInterest () const

Protected Member Functions
virtual void	DigitizeHits () const

virtual void	ConvertToCount (Float_t edep, Float_t last, UShort_t detector, Char_t ring, UShort_t sector, UShort_t strip, TArrayI &counts) const

virtual UShort_t	MakePedestal (UShort_t detector, Char_t ring, UShort_t sector, UShort_t strip) const

virtual void	AddNoise (TArrayI &) const

virtual void	AddContribution (UShort_t detector, Char_t ring, UShort_t sector, UShort_t strip, Float_t edep, Bool_t isPrimary, Int_t nTrackno, Int_t *tracknos, Int_t offset=0)

virtual void	AddDigit (UShort_t detector, Char_t ring, UShort_t sector, UShort_t strip, Float_t edep, UShort_t count1, Short_t count2, Short_t count3, Short_t count4, UShort_t ntot, UShort_t nprim, const TArrayI &refs) const

virtual TTree *	MakeOutputTree (AliLoader *loader)

virtual void	StoreDigits (const AliLoader *loader)

	AliFMDBaseDigitizer (const AliFMDBaseDigitizer &o)
	Number of labels not assigned. More...

AliFMDBaseDigitizer &	operator= (const AliFMDBaseDigitizer &o)

Protected Member Functions inherited from AliDigitizer
Int_t	GetNInputStreams () const

void	Copy (TObject &dig) const

Protected Attributes
AliFMD *	fFMD

AliRunLoader *	fRunLoader

AliFMDEdepMap	fEdep
	Run loader. More...

Float_t	fShapingTime

Bool_t	fStoreTrackRefs

Int_t	fIgnoredLabels

Protected Attributes inherited from AliDigitizer
AliDigitizationInput *	fDigInput

Detailed Description

Base class for digitizers.

This class contains the procedures simulation ADC signal for the Forward Multiplicity detector : Hits->Digits and Hits->SDigits

Digits consists of

Detector #
Ring ID
Sector #
Strip #
ADC count in this channel

Summable digits consists of

Detector #
Ring ID
Sector #
Strip #
Total energy deposited in the strip
ADC count in this channel

As the Digits and SDigits have so much in common, the classes AliFMDDigitizer and AliFMDSDigitizer are implemented via a base class AliFMDBaseDigitizer.

                +---------------------+
                | AliFMDBaseDigitizer |
                +---------------------+
                          ^
                          |
               +----------+---------+
               |                    |
     +-----------------+     +------------------+
     | AliFMDDigitizer |  | AliFMDSDigitizer |
     +-----------------+  +------------------+

These classes uses parameters fetched from the AliFMDParameters manager.

The shaping function of the VA1 is generally given by

\[ f(x) = A(1 - \exp(-Bx)) \]

where A is the total charge collected in the pre-amp., and B is a paramter that depends on the shaping time of the VA1 circut.

When simulating the shaping function of the VA1 pre-amp. chip, we have to take into account, that the shaping function depends on the previous value of read from the pre-amp.

That results in the following algorithm:

last = 0;
for (i=0; i < n_pre_amp_charge; i++) {
  charge = GetCharge(i);
  if (last < charge) 
    f(t) = (charge - last) * (1 - exp(-B * t)) + last
  else
    f(t) = (last - charge) * exp(-B * t) + charge)
  for (j=0; j < sample_rate; j++) 
    adc[j] = f(i / (# samples))
  last = charge
}

Here, the first loop is over all charges collected by the VA1 chip, and the sample_rate is how many times the ALTRO ADC samples each of the 128 charges from the pre-amp.

The charge is the total charge \( Q\) collected by the VA1 pre-amplifier for a strip. \( Q\) is then given by

\[ Q = \frac{E}{e}\frac{S}{r} \]

where \( E\) is the total energy deposited in a silicon strip, \( R\) is the dynamic range of the VA1 pre-amp, \( e\) is the energy deposited by a single MIP, and \( S\) ALTRO channel size in each time step.

The energy deposited per MIP is given by \( e = M \rho w \) where \( M\) is the universal number \( 1.664 \mbox{keV}\mbox{cm}^{2}\mbox{g}^{-1}\), \( \rho\) is the density of silicon, and \( w\) is the depth of the silicon sensor.

The final ADC count is given by

\[ C' = C + P \]

where \( P\) is the (randomized) pedestal.

This class uses the class template AliFMDEdepMap to make an internal cache of the energy deposted of the hits. The class template is instantasized as

The first member of the values is the summed energy deposition in a given strip, while the second member of the values is the number of hits in a given strip. Using the second member, it's possible to do some checks on just how many times a strip got hit, and what kind of error we get in our reconstructed hits. Note, that this information is currently not written to the digits tree. I think a QA (Quality Assurance) digit tree is better suited for that task. However, the information is there to be used in the future.

Definition at line 156 of file AliFMDBaseDigitizer.h.

Constructor & Destructor Documentation

AliFMDBaseDigitizer::AliFMDBaseDigitizer ( )

CTOR

Definition at line 226 of file AliFMDBaseDigitizer.cxx.

AliFMDBaseDigitizer::AliFMDBaseDigitizer ( AliDigitizationInput * digInp )

Normal CTOR

Parameters

manager Manager of digitization

Definition at line 242 of file AliFMDBaseDigitizer.cxx.

AliFMDBaseDigitizer::AliFMDBaseDigitizer	(	const Char_t *	name,
		const Char_t *	title
	)

Normal ctor

Parameters

name	Name
title	Title

Definition at line 257 of file AliFMDBaseDigitizer.cxx.

AliFMDBaseDigitizer::~AliFMDBaseDigitizer ( )

virtual

DTOR

Definition at line 273 of file AliFMDBaseDigitizer.cxx.

AliFMDBaseDigitizer::AliFMDBaseDigitizer ( const AliFMDBaseDigitizer & o )

inlineprotected

Number of labels not assigned.

Copy CTOR

Parameters

o	object to copy from

Definition at line 266 of file AliFMDBaseDigitizer.h.

Member Function Documentation

void AliFMDBaseDigitizer::AddContribution	(	UShort_t	detector,
		Char_t	ring,
		UShort_t	sector,
		UShort_t	strip,
		Float_t	edep,
		Bool_t	isPrimary,
		Int_t	nTrackno,
		Int_t *	tracknos,
		Int_t	offset = `0`
	)

protectedvirtual

Add edep contribution from (detector,ring,sector,strip) to cache

Definition at line 328 of file AliFMDBaseDigitizer.cxx.

Referenced by AddNoise(), AliFMDDigitizer::SumContributions(), and AliFMDHitDigitizer::SumContributions().

void AliFMDBaseDigitizer::AddDigit	(	UShort_t	detector,
		Char_t	ring,
		UShort_t	sector,
		UShort_t	strip,
		Float_t	edep,
		UShort_t	count1,
		Short_t	count2,
		Short_t	count3,
		Short_t	count4,
		UShort_t	ntot,
		UShort_t	nprim,
		const TArrayI &	refs
	)		const

protectedvirtual

Add a digit to output

Reimplemented in AliFMDHitDigitizer.

Definition at line 583 of file AliFMDBaseDigitizer.cxx.

Referenced by AliFMDHitDigitizer::AddDigit(), AddNoise(), and DigitizeHits().

virtual void AliFMDBaseDigitizer::AddNoise ( TArrayI & ) const

inlineprotectedvirtual

Add noise to each sample

Definition at line 224 of file AliFMDBaseDigitizer.h.

void AliFMDBaseDigitizer::ConvertToCount	(	Float_t	edep,
		Float_t	last,
		UShort_t	detector,
		Char_t	ring,
		UShort_t	sector,
		UShort_t	strip,
		TArrayI &	counts
	)		const

protectedvirtual

Convert the total energy deposited to a (set of) ADC count(s). See also the class description for more details.

Parameters

edep	Total energy deposited in detector
last	Last charge collected in previous VA1 channnel
detector	Detector #
ring	Ring ID
sector	Sector #
strip	Strip #
counts	Array holding the counts on return

Definition at line 489 of file AliFMDBaseDigitizer.cxx.

Referenced by DigitizeHits(), and IsStoreTrackRefs().

void AliFMDBaseDigitizer::DigitizeHits ( ) const

protectedvirtual

For the stored energy contributions in the cache, convert the energy signal to ADC counts, and store the created digit in the digits array

Parameters

fmd	Pointer to detector

Definition at line 394 of file AliFMDBaseDigitizer.cxx.

Referenced by AliFMDHitDigitizer::Digitize(), AliFMDDigitizer::Digitize(), and IsStoreTrackRefs().

Float_t AliFMDBaseDigitizer::GetShapingTime ( ) const

inline

Returns: Get the shaping time

Definition at line 186 of file AliFMDBaseDigitizer.h.

Bool_t AliFMDBaseDigitizer::Init ( void )

virtual

Initialize

Reimplemented from AliDigitizer.

Reimplemented in AliFMDDigitizer.

Definition at line 300 of file AliFMDBaseDigitizer.cxx.

Referenced by AliFMD::Hits2Digits(), AliFMD::Hits2SDigits(), and AliFMDDigitizer::Init().

Bool_t AliFMDBaseDigitizer::IsStoreTrackRefs ( ) const

inline

Definition at line 189 of file AliFMDBaseDigitizer.h.

TTree * AliFMDBaseDigitizer::MakeOutputTree ( AliLoader * loader )

protectedvirtual

Make the output tree using the passed loader

Parameters

loader

Returns: The generated tree.

Reimplemented in AliFMDHitDigitizer.

Definition at line 605 of file AliFMDBaseDigitizer.cxx.

Referenced by AddNoise(), AliFMDDigitizer::Digitize(), and AliFMDHitDigitizer::MakeOutputTree().

UShort_t AliFMDBaseDigitizer::MakePedestal	(	UShort_t	detector,
		Char_t	ring,
		UShort_t	sector,
		UShort_t	strip
	)		const

protectedvirtual

Make a pedestal

Parameters

detector	Detector #
ring	Ring ID
sector	Sector #
strip	Strip #

Returns: Pedestal value

Reimplemented in AliFMDHitDigitizer.

Definition at line 312 of file AliFMDBaseDigitizer.cxx.

Referenced by ConvertToCount(), IsStoreTrackRefs(), and AliFMDHitDigitizer::MakePedestal().

AliFMDBaseDigitizer & AliFMDBaseDigitizer::operator= ( const AliFMDBaseDigitizer & o )

protected

Assignment operator

Returns: Reference to this object

Definition at line 280 of file AliFMDBaseDigitizer.cxx.

Referenced by AliFMDBaseDigitizer(), and AliFMDHitDigitizer::operator=().

void AliFMDBaseDigitizer::SetShapingTime ( Float_t B = 10 )

inline

The response shape of the VA1 shaping circuit is approximently given by

\[ f(x) = A(1 - \exp(-Bx)) \]

where \( A\) is the total charge collected by the pre-amp., and \( B\) is parameter that depends on the shaping time of the VA1 pre-amp. This member function sets the parameter \( B\)

Parameters

B

Definition at line 184 of file AliFMDBaseDigitizer.h.

Referenced by AliFMDBaseDigitizer().

void AliFMDBaseDigitizer::SetStoreTrackRefs ( Bool_t store = kTRUE )

inline

Definition at line 188 of file AliFMDBaseDigitizer.h.

void AliFMDBaseDigitizer::StoreDigits ( const AliLoader * loader )

protectedvirtual

Store the data using the loader

Parameters

loader The loader