2020 Valencia model available as mec_kind=6

[hprasad2419]

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This version incorporates the 2020 Valencia model from Phys. Rev. C 102 (2020) 024601 within NuWro.
Users can now access the 2020 Valencia model as

mec_kind = 6

in params.txt.

Hadronic Tables

The tables are stored in a new directory named as MEC_data under the src/ directory. The dir MEC_data/ further contains three sub-directories namely C12, O16, and Ca40 which stores the hadronic tables corresponding to $pp, np, pn$ and $3p3h$ for the respective nucleus.

To optimize the performance of NuWro, the hadronic tables are loaded just once while building the information within nucleus. Class Response_function is defined in src/nucleus.h which stores the 4 contributions namely $pp, np, pn$ and $3p3h$ for each component of the tensor $W^{\mu\nu}$. Class nucleus which was already defined in src/nucleus.h now stores the hadronic tables as an object of class Response_function. There are five object of this class each designated to a single component of the tensor. These are W00, W03, W11, W12, and W33.

Code

The code which models the 2020 Valencia model is written in src/mecevent_2020Valencia.h and src/mecevent_2020Valencia.cc.

Nucleon Sampling function

The new nucleon sampling function is defined in the file src/vecrand.h as nucleon_sampling_function( ... ) which takes 4 arguments:

• double cos : Cosine angle between the desired vector with respect to a given vector.
• double par: Value from MEC_cm_direction.
• double n: Value from MEC_cm_strength.
• double cosboundary: Allowed range of cosine of the angle due to Pauli blocking.

To sample a vector from the nucleon sampling function, the function rand_direc2( ... ) is added which takes 4 inputs:

• vec a: The vector which is used as a basis to draw another random vector aligned at a specific polar angle with respect to this vector.
• 'double alpha: Value from MEC_cm_direction`.
• double degree: Value from MEC_cm_strength.
• double kappa: The allowed range of cosine of the angle from which the angle is sampled`.

Updated params.txt

The new degrees of freedom implemented with 2020 Valencia model can be accessed with the update data/params.txt file.

The new parameters are the following

• MEC_3p3h_dynamics: To turn ON(1)/OFF(0) the 3p3h contribution in the MEC event of mec_kind=6.
• MEC_cm_direction_pp: center of mass direction of outgoing $pp$ nucleons in 2020 Valencia model. This is passed as an argument to the nucleon sampling function.Default values is set as MEC_cm_direction_pp=0.77.
• MEC_cm_strenght_pp: Strength of sampling the outgoing $pp$ nucleons in 2020 Valencia model. This is passed as an argument to the nucleon sampling function. Default values is set as MEC_cm_strength_pp = 4.
• MEC_cm_direction_np: center of mass direction of outgoing $np$ nucleons in 2020 Valencia model. This is passed as an argument to the nucleon sampling function.Default values is set as 0.7.
• MEC_cm_strenght_np: Same as MEC_cm_strength_pp but for $np$ outgoing pair. Default value is set as MEC_cm_strength=3.
• MEC_cm_direction_pn: center of mass direction of outgoing $pn$ nucleons in 2020 Valencia model. This is passed as an argument to the nucleon sampling function.Default values is set as 0.8.
• MEC_cm_strength_pn: Same as MEC_cm_strength_pp but for $pn$ outgoing pair. Default value is set as MEC_cm_strength=4.