6.2.7.2. UsineFit@FreePars

Enable fit/nuisance params for minimization runs, whose syntax is name:X,Y,[min,max],init,sigma

• name is the name of the parameter (see table below)

• X = FIT, FIXED, or NUISANCE:

  • FIT: use the parameter name as a fit parameter. If the minimizer allows it, for instance Minuit, sets initial value to init, initial error to sigma, and lower and upper values of the parameter limited to [min,max] (use [-,-], or [-,max], or [min,-] for no lower/upper limits).
  • FIXED: use the parameter name as a fixed parameter (if the minimizer allows it), set to init. The parameters sigma and [min,max] are unused.
  • NUISANCE: assumes a Gaussian distributed parameter \({\cal N}(\mu =\) init, \(\sigma =\) sigma), which contributes to the global \(\chi^2\) as

  \[\chi^2_{\rm nuisance} = (\frac{{\rm val}-{\rm init}}{\sigma})^2\]

  where val is the value tested in the fit. Not that we strongly penalize values outside [min,max] (they are excluded in practice).

• Y = LIN or LOG: enables to sample the parameter as name or \(\log_{10}\) (name).

Warning

All @ParNames parameters can be in principle declared as fit parameters. However, a subtlety arises because of the possibility to have universal vs per CR source parameters: for universal parameters, USINE directly uses the parameter name, otherwise it builds NCR parameters X_Y with X=parameter name and Y=CR name (e.g., for q, generates q_1H, q_2H, q_3HE… which can all be left as free parameters). In addition, modulation parameters can be declared as free/nuisance parameters for all data periods used in FitTOAData (see below), and data error uncertainties can also be added as nuisance parameters: in both cases, the name of the parameter is built internally from the experiment name (removing special characters ([*%@)]... by _). Run ./bin/usine_run -m1  inputs/your.init.file (with your.init.file you initialisation file) to list what parameters can be left free for your initialisation file.

Table 6.11 List/examples of enabled parameters (fit or nuisance parameters).

Group@subgroup@parameter	Description
UsineFit@FreePars@CRs (M=1)	Half-life of all unstable CRs are enabled as nuisance parameters, e.g. HalfLifeBETA_10Be:NUISANCE,LIN,[1.3,1.5],1.387,0.012 (use EC instead of BETA if EC-unstable nucleus).
UsineFit@FreePars@DataErr (M=1)	If @FitTOAData@ErrType parameter set to kERRCOV for CR quantity (see next subgroup), its systematics are enabled as centred nuisance parameters, e.g., SCALE_AMS02_201105201605__BC:NUISANCE,LIN,[-10,10],0.,1.. - If a systematics not set as nuisance parameter, it is accounted for in covariance matrix (see Section 5.5); - if systematics set as nuisance parameter, amounts to a model bias: for \(N_s\) types of systematics set as nuisance for a quantity Q , the model calculation read \({\rm model}^Q(R_k) = {\rm model}^Q_{\rm true}(R_k) \times {\rm bias}^Q(R_k) =\) \({\rm model}^Q_{\rm true}(R_k) \times \Pi_{l=0\dots n} (1+\nu^Q_l \times \sigma^Q_l(R_k))\), with \(\nu^Q_l\) the nuisance parameter (centred on 0, variance 1) and \(\sigma^Q_l(R_k)\) the relative error for the calculated point \(R_k\) (read from the diagonal of the covariance matrix for simplicity). In that case, the systematics is not in \(\chi^2_{\rm cov}\), but as a standard \(\chi^2_{\rm nuis}\) (see above).
UsineFit@FreePars@Geometry (M=1)	Any parameter in Model…@Geometry@ParNames.
UsineFit@FreePars@ISM (M=1)	Any parameter in Model…@ISM@ParNames.
UsineFit@FreePars@Modulation (M=1)	Run ./bin/usine with option -m1 to get enabled names for data and modulation levels, e.g. phi_AMS02_201105201605_:NUISANCE,LIN,[0.3,,1.1],0.73,0.2 ( Force-Field approx.).
Run@FitFreePars@SrcSteadyState (M=1)	Any source parameter, e.g. q_4HE:FIT,LOG,[-5.,-3],-4.,0.1 or alpha:NUISANCE,LIN,[1.7.,2.5],2.3,0.1
Run@FitFreePars@Transport (M=1)	Any parameter in Model…@Transport@ParNames, e.g. delta:FIT,LIN,[0.2,0.9],0.6,0.02, or Va:FIT,LIN,[1.,120],70.,0.1, etc.
UsineFit@FreePars@XSection (M=1)	XS parameters format are PREFIX_REACTION (see examples in inputs/init.TEST.par): - ‘PREFIX’ enabled: - for standard bias of XS: - Norm → normalisation parameter (all E) - EAxisScale → \(\sigma(E_{k/n}^{\rm new})=\sigma(E_{k/n} \times {\rm EAxisScale})\) - EnhancePowHE → (TUXSections::XS_EnhancementHE)^(EnhancePowHE) - EThresh and SlopeLE → below threshold \(\sigma(E_{k/n}) = (E_{k/n}/{\rm EThresh})^{\rm SlopeLE} \times \sigma(E_{k/n})\), with \({\rm EThresh}=5~{\rm GeV/n}\) if not set as nuisance. - for linear combination of XS (\(\sigma_{\rm LC} = \sum_i C_i \times \sigma_i\)): - LCInelBar94, LCInelTri99, LCInelWeb03, LCInelWel97 for inelastic XS, - LCProdGal17, LCProdSou01, LCProdWeb03, LCProdWKS98 for production XS. - enabled ‘REACTION’ keywords - Total inelastic XS: - 12C+H → specific reaction - ANY+H → any CR on given target - 12C+ANY → 12C on all ISM targets - Production XS: - 12C+H->10Be → specific reaction - ANY+H->10Be → any CRs - 12C+ANY->10Be → any target - 12C+H->ANY → any fragment - Tertiary XS (tot. and diff. similarly biased): - 1H-BAR+H->1H-BAR → specific reaction - 1H-BAR+ANY->1H-BAR → any target - ALL → if not linear combination of XS, applies to all XS (inel, prod, and tertiary); otherwise, can be applied for all linear combination of inelastic and/or production XS applies to all XS (inel, prod, and tertiary)! Note that it is not allowed to have the same prefix used for overlapping reactions (e.g., 12C+ANY has overlapping reactions with 12C+H).