Set-up of the dynamics

Several different descriptions for the dynamics of the decay of a resonance are supported. It has to be set-up in the main configuration-file with the option "addDynamics" followed by in general one argument. For specific descriptions more than one argument is needed (e.g. for the Flatte formalism) or even a seperate configuration file (for the generic K-matrix description) is mandatory. The user can speciify between:
  • "addDynamics particleName BreitWigner": a simple Breit-Wigner parametrization
  • "addDynamics particleName BreitWignerRel": a relativistic Breit-Wigner parametrization
  • "addDynamics particleName BreitWignerBlattWRel {qR-factor}": a relativistic Breit-Wigner parametrization with Blatt-Weisskopf centrifugal-barrier factors and optioal an argument for setting th​e qR-barrier constant (default: 0.197)
  • "addDynamics particleName Voigt": a convolution of a Lorentz profile and a Gaussian distribution which is suitable for very narrow resonances
  • "addDynamics particleName Flatte {particle1} {particle2}": a generic Flatte parametrization. The second decay channel has to be defined by the specification of particle1 and particle2.
  • "addDynamics particleName K0star1430Lass ": the LASS parametrization for the K0*(1430)
  • "addDynamics KMatrixParticleName PiPiSWaveAS ": (pi pi)S-wave parametrisation by Anisovich and Sarantsev ("Eur. Phys. J. A16, 229(2013)") for the mass range up to 1900 MeV which contains 5 different poles and 5 decay channels
  • "addDynamics KMatrixParticleName KpiSWaveIso12 ": (K pi)S-wave parametrisation for the isospin 1/2 component used by the FOCUS experiment ("Phys. Lett. B653 (2007) 1-11").
  • "addDynamics particleName KpiSWaveIso32 ": (K pi)S-wave parametrisation for the isospin 3/2 component used by the FOCUS experiment ("Phys. Lett. B653 (2007) 1-11").
  • "addDynamics particleName BlattWBarrier {qR-factor}": simple Blatt-Weisskopf factors without any description of the mass shape; the argument for setting th​e qR-barrier constant is optional (default: 0.197).
  • "addDynamics KMatrixParticleName KMatrix {name of the K-matrix configuation file}": generic K-matrix defined by a separate configuration file. A summary about the options and different arguments are listed below.

Configuration of a generic K-matrix description

The generic K-matrix description has to be done via a separate configuration file. One can define any number of different poles and decay channels. Moreover it is possible to make use of the Adler-zero term and to add any order of backgound terms. All available options with the corresponding arguments are listed in the table below:

Option Arguments Description
keyName {string} name of the K-matrix and suffix for fit parameter
noOfChannels {integer value} number of decay channels
noOfPoles {value1} number of pole positions
gFactor {particle1} {particle2} {value1} {value2} ... {valueN} N different g-factors for each of the N individual channels
pole {name of thepole} {value} name of the pole followed by the pole position
projection {particle1} {particle2} pojection of the particle pair
useBarrierFactors {bool} enable/diable barrier factors
orbitalMomentum {integer value} orbital momentum of the decay
orderKMatrixBackground {integer value}

oder of the background terms. The fit parameters are automatically initialized by 0.

The value "-1" means that no background term are considered.

useAdler0 {bool} enable/diable Adler-zero term
s0Adler {value} starting value for the s0 parameter (only relevant for useAdler0=1)
snormAdler {value} starting value for the snorm parameter (only relevant for useAdler0=1)

Note: the specification of the g-factors, the pole positions and optionally the s0 and snorm Adler terms are required for the initialization of the fit-parameter. The user can fix or release these paramerter during the fit procedure.

-- BertramKopf - 08 Jul 2014
Topic revision: r6 - 27 Jan 2015, BertramKopf
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