Parameters list

NuWro uses by default settings from the params.txt file located in $PWD directory. If the file does not exist, the one from nuwro/data folder is loaded. If both files are missing or some of the parameters are not set in the file, default values are used.

General settings¶

Parameter name	Possible arguments	Default value	Description
number_of_events	positive integer	1e5	The number of equally weighted events to be saved in the output ROOT file
number_of_test_events	positive integer	1e6	The number of events used to calculate cross sections (not saved by default)
user_events	0, 1	0	Used to turn on the fitting procedure: 0 - Run NuWro 1 - Fit axial mass to MiniBooNE data for CCQE
user_params (for user_events 1)	x y z	-	Parameters for the axial mass extraction procedure: x - the minimum axial mass value y - the maximum axial mass value z - the axial mass step
random_seed	positive integer	0	Controls the random seed persistence: 0 - use time(NULL) as a seed for the random number generator 1 - read state from “random seed” file or use seed=time(NULL), if the file was not found n - use n as the seed for the random number generator
mixed_order	0, 1	0	If 1, events are saved to the output file in random order
save_test_events	0-2	0	Turn on to use test events in the analysis: 0 - test events are not saved 1 - test events are finalized and stored in weight.eventsout.root file, the average weight is equal to the total cross section 2 - test events of nonzero weights are finalized and stored in weight.eventsout.root file, the weights are respectively scaled, so the average weight is equal to the total cross section

Beam settings¶

Parameter name	Possible arguments	Default value	Description
beam_direction	x y z	0 0 1	The direction of the neutrino momentum in xyz coordinates
beam_type	0-4	0	Types of beams: 0 - a single neutrino flavor beam 1 - a mixed flavor beam 2 - a beam loaded from a ROOT file 3 - a beam loaded from the histogram (histout.txt) 4 - create histout.txt file based on a ROOT file (than use beam type 3 to run NuWro)
beam_particle (for beam_type 0)	+/- 12, 14, 16	14	PDG number of the incident neutrino
beam_energy (for beam_type 0)	explained below	1000	The energy profile
beam_content (for beam_type 1)	explained below	-	The mixed beam definition
beam_folder (for beam_type 2, 4)	path	../flux	The path to the directory with ROOT files
beam_file_first (for beam_type 2, 4)	positive integer	1	The number of the first file in the folder to be read
beam_file_limit (for beam_type 2, 4)	positive integer	0	The number of files to be loaded (0 - read files to the last one in the directory)
beam_offset	x y z	0 0 0	The offset of the position of the interaction in xyz coordinates
beam_placement (in cascade mode only)	0-2	0	The starting position of the particle: 0 - the propagation starts at the center of the nucleus 1 - the propagation starts at a random place inside the nucleus 2 - the propagation starts just under the surface of the nucleus

Defining energy profile for a single flavor beam¶

For a single flavor neutrino beam you need to set up beam_type = 0 and specify neutrino PDG using beam_particle = [PDG code].

The energy profile is set using beam_energy:

for a mono-energetic beam use:
```
beam_energy = E
```
where E is neutrino energy in MeV
for a uniform beam with energy range from E0 to E1 use:
```
beam_energy = E0 E1
```
for a non-uniform beam with energy range from E0 to E1 given by histogram a1, a2, ..., an use:
```
beam_energy = E0 E1 a0 a1 ... an
```

Hint

The histogram does not have to be normalized. The probability of finding neutrino energy in i-th bin is defined as follows:

$P_i = \frac{a_i}{\sum\limits_{i=0}^n a_j}$

Example

The following code:

beam_energy = 1000 2000 1 2 3 4

defines the following beam:

^
|
|                       |-----|
|                       |     |
|                 |-----|     |
|                 |     |     |
|           |-----|     | 40% |
|           |     | 30% |     |
|     |-----| 20% |     |     |
|     | 10% |     |     |     |   
|-----|-----|-----|-----|-----|-----> E [MeV]   
    1000  1250  1500  1750  2000

Defining energy profile for a mixed flavor beam¶

For a mixed flavor neutrino beam you need to set up beam_type = 1.

Instead of using beam_particle and beam_energy you should define a beam with:

beam_content = [PDG code] [fraction]% [beam energy]

where [beam energy] is defined as for a single flavor beam.

Example

The following code:

beam_content = 14 80% 1000

defines mono-energetic muon neutrino beam, which constitutes 80% of the whole flux.

You may add as many beam contents as you want in the following way:

beam_content += [PDG code] [fraction]% [beam energy]

Please note +=. Using = would clear the previous content.

In general, a mixed flavor beam definition would look like this:

beam_content = [PDG code 1] [fraction 1]% [beam energy 1]
beam_content += [PDG code 2] [fraction 2]% [beam energy 2]
beam_content += [PDG code 3] [fraction 3]% [beam energy 3]
...

Example

The following code:

beam content = 12 75% 1000
beam content += -12 20% 1000 2000
beam content += 14 5% 1000 1500 1 5 10 15 5 1

defines the following beam:

75% of mono-energetic electron neutrinos
20% of electron anti-neutrinos with uniformly distributed energy
5% of muon neutrinos with some energy distribution in range 1-1.5 GeV

Predefined beams¶

One can also use predefined beam specifications instead of the above parameters. The list of beams can be found in nuwro/data/beam directory. To use one of those beams, one must use the following line:

@beam/beamfile.txt

where beamfile.txt is the name of the file from nuwro/data/beam directory.

Target settings¶

Parameter name	Possible arguments	Default value	Description
target_type	0-2	0	Types of targets: 0 - a single nucleus 1 - a target composed from
some nuclei 2 - a detector geometry loaded from a ROOT file
nucleus_p (for target_type 0)	positive integer	6	The number of protons in a target nucleus
nucleus_n (for target_type 0)	positive integer	6	The number of neutrons in a target nucleus
nucleus_E_b (for target_type 0)	positive integer	34	The binding potential (sum of binding and Fermi energies)
nucleus_kf (for target_type 0)	positive integer	220	The Fermi momentum
nucleus_target	0-5	2	Nucleus models used in a primary interaction: 0 - free nucleon 1 - Fermi gas 2 - local Fermi gas 3 - Bodek-Ritchie model 4 - spectral function 5 - deuterium
nucleus_model	0, 1	1	Nucleus density profiles for FSI: 0 - constant density 1 - realistic density profile
target_content(for target_type 1)	explained below	-	The composed target definition
geo_file (for target_type 2)	filename	target/ND280v9r7p5.root	The path to the file with the detector geometry
geo_name (for target_type 2)	geometry name	ND280Geometry v9r7p5	The name of the geometry in the file
geo_o (for target_type 2)	x y z	0 0 0	The coordinates of the center of the box
geo_d (for target_type 2)	x y z	2000 5000 2000	The half dimension of the box
geo_volumne (for target_type 2)	master volume name	-	The name of the master volume in the detector file

Defining a single nucleus target¶

In order to define a single nucleus target you need to set up target_type = 0. Then, define the number of nucleons using:

nucleus_p = [#protons]
nucleus_n = [#neutrons]

You may set up other nucleus properties using parameters listed in the table above.

Example

To define Carbon target use:

target_type = 0
nucleus_p = 6
nucleus_n = 6

Defining a composed target¶

In order to define a multi-nuclei target you need to set up target_type = 1.

Instead of using nucleus_p, nucleus_n and other nucleus related parameters you should define your target with:

target_content = [#protons] [#neutrons] [#nuclei] x [binding energy] [Fermi momentum] [nucleus target]

where only first three arguments are required.

When using local Fermi gas model binding energy and Fermi momentum are taken from tables anyway.

You may add as many nuclei as you want in the following way:

target_content += [#protons] [#neutrons] [#nuclei] x [binding energy] [Fermi momentum] [nucleus target]

Please note +=. Using = would clear the previous content.

In general, a multi-nuclei target definition would look like this:

target_content = [#protons 1] [#neutrons 1] [#nuclei 1] x
target_content += [#protons 2] [#neutrons 2] [#nuclei 2] x
target_content += [#protons 3] [#neutrons 3] [#nuclei 3] x

Example

To define $C_2H_6O$ use the following code:

target_type = 1
target content = 6 6 2 x
target content += 1 0 6 x
target content += 8 8 1 x

Predefined targets¶

One can also use predefined target specifications instead of the above parameters. The list of targets can be found in nuwro/data/target directory. To use one of those beams, one must use the following line:

@target/targetfile.txt

where targetfile.txt is the name of the file from nuwro/data/target directory.

Please note that many predefined targets use slightly different syntax for composed targets. The syntax without space after [#nuclei] will not work on MacOS.

Interactions settings¶

Parameter name	Possible arguments	Default value	Description
dyn_qel_cc	0, 1	1	Turn on/off charge current quasielastic process
dyn_qel_nc	0, 1	1	Turn on/off neutral current quasielastic process
dyn_res_cc	0, 1	1	Turn on/off charge current resonance pion production
dyn_res_nc	0, 1	1	Turn on/off neutral current resonance pion production
dyn_dis_cc	0, 1	1	Turn on/off charge current deep inelastic scattering
dyn_dis_nc	0, 1	1	Turn on/off neutral current deep inelastic scattering
dyn_coh_cc	0, 1	1	Turn on/off charge current coherent pion production
dyn_coh_nc	0, 1	1	Turn on/off neutral current coherent pion production
dyn_mec_cc	0, 1	1	Turn on/off charge current meson exchange current process
dyn_mec_nc	0, 1	1	Turn on/off neutral current meson exchange current process

Quasi-elastic¶

Parameter name	Possible arguments	Default value	Description
qel_vector_ff_set	1-6	2	Electromagnetic form factors parametrization: 1 - dipole form 2 - BBBA05 (Ref. [1]) 3 - BBA03 (Ref. [2]) 4 - JLab (Ref. [3]) 5 - NN10 with two photon exchange effect (Ref. [4])
qel_axial_ff_set	1-4	1	Axial form factors parametrization: 1 - dipole form 2 - 2-fold parabolic modification 3 - 3-fold parabolic modification 4 - 4-fold parabolic modification
qel_strange	0, 1	0	Turn on/off the strange quark contribution to the NC axial form factors
qel_strangeEM	0, 1	0	Turn on/off the strange quark contribution to the NC vector form factors
delta_s	any number	-0.15	Strangeness contribution
qel_cc_axial_mass	positive number	1200	The axial mass value for charge current form factors
qel_nc_axial_mass	positive number	1350	The axial mass value for neutral current form factors
qel_s_axial_mass	positive number	1200	The axial mass value used in the dipole strange form factor
qel_rpa	0-3	0	RPA settings: 0 - do not use RPA 1 - use RPA without effective mass of nucleon 2 - use effective mass of nucleon without RPA (test only) 3 - use RPA with effective mass of nucleon (test only)
flux_correction	0, 1	1	Turn on/off flux correction
sf_method	0-3	0	Spectral function settings (for CCQE): 0 - do not use spectral function 1 - use grid spectral function (for 12C, 16O, 40Ar, 40Ca, 56Fe) 2 - use factorized spectral function (for 16O, 40Ar, 40Ca)
cc_smoothing	0, 1	1	If 1, the impossible quasi-elastic reaction (like CC nu scattering off proton) are skipped

Pion production¶

Parameter name	Possible arguments	Default value	Description
delta_FF_set	1-7	1	Delta production form factors: 1 - dipole form [5] 2 - Paschos and Lalakulich, 2.12 MA = 1.05GeV BNL fit (Ref. [6]) 3 - Paschos and Lalakulich, 2.12 MA = 0.84GeV ANL fit (Ref. [6]) 4 - Paschos and Lalakulich, page 4, bottom right (Ref. [6]) 5 - Paschos and Lalakulich, page 5, top left (Ref. [6]) 6 - Eq. 13 from Ref. [7] 7 - based on chiral quark model from Ref. [8]
pion_axial_mass (for delta_FF_set 1)	positive number	0.94	The axial mass value used in dipole parametrization of the resonance pion production form factor
pion_C5A (for delta_FF_set 1)	positive number	1.19	The C5A value used in dipole parametrization of the resonance pion production form factor
spp_precision	positive number	500	Controls the precision in RESDIS boundary region; should not be changed
red_dis_cut	positive number	1600	Boundary of RES-DIS transition; should not be changed
coh_mass_correction	0, 1	1	Turn on/off Rein Sehgal correction to charge current coherent pion production
coh_new	0, 1	1	Change between old (0) and improved (1) implementation of coherent pion production

Two-body current¶

Parameter name	Possible arguments	Default value	Description
mec_kind	1-4	1	Two-body current models: 1 - Transverse Enhancement model (Ref. [9]) 2 - based on Marteau model (Ref. [10, 12]) 3 - Nieves et al. model (Ref. [11])
mec_ratio_pp	[0,1]	0.6	The fraction of mixed initial nucleon pairs for charge current interaction. For neutral current the fraction is calculated as 1/(2*mec ratio pp + 1)

Final state interactions¶

Parameter name	Possible arguments	Default value	Description
kaskada_on	0, 1	1	Turn on (1) / off (0) final state interactions
kaskada_w	positive number	7	The value of the effective potential subtracted from the nucleons energy leaving the nucleus
kaskada_redo	0, 1	0	If on, given output file (eventsout.root by default) is loaded, the primary vertex is copied and only final state interactions are simulated. New output file with .fsi.root suffix is created
kaskada_writeall	0, 1	0	If on, all particles created during final state interactions are saved in all vector
step	positive number	0.2	Length of max step in the cascade in fm
xsec	0, 1	1	Cross section models for pion-nucleon interactions: 0 - based on Ref. [13] 1 - based on Ref. [14]
pauli_blocking	0, 1	1	Turn on/off Pauli blocking
formation_length (for formation_zone const)	positive number	1	Formation length in fm
tau	positive number	8	The parameter control the formation length for ranft and rl models
first_step	0, 1	0	If off, the formation zone is applied only for the particles created during final state interactions
formation_zone	explained below	fz	explained below

Formation zone models¶

nofz: formation zone is off
skat8: SKAT parametrization (Ref. [15])
cosyn: parametrization based on Color Transparency measurements (Ref. [16])
cohl: coherence length (Ref. [17])
ranft: parametrization based on hadron-hadron and hadron-nucleus collision (Ref. [18])
rl: as ranft but with fixed transverse momentum equal zero
delta: for resonance pion production; based on ∆ lifetime (Ref. [19])
const: constant value (defined by formation_length)
fz (default):
- cohl for quasi-elastic scattering
- delta for resonance pion production
- ranft for deep inelastic scattering
- nofz for meson exchange current
trans: only for nuclear transparency analysis

References¶

[1] R. Bradford et al. “A New parameterization of the nucleon elastic form-factors”. Nucl.Phys.Proc.Suppl. 159 (2006), pp. 127–132.

[2] Howard Scott Budd, A. Bodek, and J. Arrington. “Modeling quasielastic form-factors for electron and neutrino scattering” . arXiv: hep-ex/0308005 (2003).

[3] E.J. Brash et al. “New empirical fits to the proton electromagnetic form-factors”. Phys.Rev. C65 (2002), p. 051001.

[4] Krzysztof M. Graczyk, Piotr Plonski, and Robert Sulej. “Neural Network Parameterizations of Electromagnetic Nucleon Form Factors”. JHEP. 1009 (2010), p. 053.

[5] K.M. Graczyk, D. Kielczewska, P. Przewlocki, and J.T. Sobczyk. "C(5)**A axial form factor from bubble chamber experiments". Phys.Rev. D80 (2009) 093001

[6] Olga Lalakulich and Emmanuel A. Paschos. “Resonance production by neutrinos. I. J = 3/2 resonances”. Phys.Rev. D71 (2005), p. 074003.

[7] L. Alvarez-Ruso, S. K. Singh, and M. J. Vicente Vacas. “Charged current weak electroproduction of the ∆ resonance”. Phys. Rev. C. 57 (5 1998), pp. 2693–2699.

[8] D. Barquilla-Cano, A.J. Buchmann, and E. Hernandez. “Axial N-¿Delta(1232) and N-¿N*(1440) transition form factors”. Phys.Rev. C75 (2007), p. 065203.

[9] A. Bodek, H.S. Budd, and M.E. Christy. “Neutrino Quasielastic Scattering on Nuclear Targets: Parametrizing Transverse Enhancement (Meson Exchange Currents)”. Eur.Phys.J. C71 (2011), p. 1726.

[10] Jan T. Sobczyk. “Modeling nuclear effects in neutrino interactions in 1-GeV region” . arXiv: nucl-th/0307047 (2003).

[11] J. Nieves, I. Ruiz Simo, and M. J. Vicente Vacas. “Inclusive charged-current neutrino-nucleus reactions”. Phys. Rev. C. 83 (4 2011), p. 045501.

[12] M. Martini et al. “Unified approach for nucleon knock-out and coherent and incoherent pion production in neutrino interactions with nuclei”. Phys. Rev. C. 80 (6 2009), p. 065501.

[13] N. Metropolis et al. “Monte Carlo Calculations on Intranuclear Cascades. I. Low-Energy Studies”. Phys.Rev. 110 (1958), pp. 185–203.

[14] L.L. Salcedo et al. “Computer simulation of inclusive pion nuclear reactions”. Nucl.Phys. A484 (1988), p. 557.

[15] D.S. Baranov et al. “An estimate for the formation length of hadrons in neutrino interactions” (1984).

[16] Wim Cosyn. “Exploring the limits of a hadronic picture of nuclei through pion and nucleon removal reactions”. PhD thesis. Ghent University, 2009. url: http://lib.ugent.be/fulltxt/RUG01/001/350/817/RUG01-001350817/_2010/_0001/_AC.pdf1

[17] A. Rubbia G. Battistoni A. Ferrari and P.R. Sala. The FLUKA nuclear cascade model applied to neutrino interactions. talk given at NuInt02. 2002.

[18] J. Ranft. “Hadron production in hadron-nucleus and nucleus-nucleus collisions in a dual parton model modified by a formation zone intranuclear cascade”. Zeitschrift f¨ur Physik C Particles and Fields. 43.3 (1989), pp. 439–446.

[19] Tomasz Golan, Cezary Juszczak, and Jan T. Sobczyk. “Final State Interactions Effects in Neutrino-Nucleus Interactions”. Phys.Rev. C86 (2012), p. 015505.