TMDlib Interface
NeoPDF provides an interface to the TMDlib library which allows users for example
to interpolate TMD PDFs from the CLI. Most importantly, it is used to convert TMDlib
sets into NeoPDF formats.
Installing the interface
To install the TMDlib interface, first clone the repository and run the following
command:
Note that this requires TMDlib and its dependencies to be installed and available
in the environment paths.
Interpolating TMDlib sets
To interpolate TMDlib sets from the CLI, the command is similar to the one used for
regular sets:
neopdf compute xfx_q2_kt --pdf-name MAP22_grids_FF_Km_N3LL --member 0 --pid 2 0.00010000000000000009 1.00000e-1 4.14987e3
For more details on the required arguments, refer to the helper:
> neopdf compute xfx_q2_kt --help ─╯
Evaluate TMD PDF for a given set, member, and input values
Usage: neopdf compute xfx_q2_kt --pdf-name <PDF_NAME> --member <MEMBER> --pid <PID> <INPUTS>...
Arguments:
<INPUTS>... Input values (kt, x, Q2)
Options:
-p, --pdf-name <PDF_NAME> Name of the TMD PDF set
-m, --member <MEMBER> Member index (0-based)
-i, --pid <PID> PDG flavor ID
-h, --help Print help
Converting TMDlib sets into NeoPDF
To convert a TMDlib set into the NeoPDF format, one needs to write a configuration file
in the .toml format. This configuration file should contain all the information about the
metadata and the grid configurations. The following is an example:
set_name = "MAP22_grids_FF_Km_N3LL"
set_desc = "MAP22 TMDs for K- fragmentation, converted to NeoPDF"
set_index = 0
n_members = 2
# Inner edges for the subgrids. Leave empty for no subgrids.
x_inner_edges = [0.2]
q_inner_edges = [] # Q, not Q2
kt_inner_edges = [1e-2, 1.0]
# Number of points for (subg)grids.
n_x = [5, 5]
n_q = [6]
n_kt = [5, 5, 4]
# Grid axes that are not part of the TMD interpolation
nucleons = [0.0] # dummy value
alphas = [0.118] # alpha_s(M_Z)
# Metadata
pids = [-3, -2, -1, 21, 1, 2, 3]
polarised = false
set_type = "TimeLike"
interpolator_type = "LogChebyshev" # or LogTricubic
error_type = "replicas"
hadron_pid = 321 # Kaon
alphas_qs = [91.1876] # dummy values
alphas_vals = [0.118] # dummy values
# Physics Parameters
flavor_scheme = "fixed"
order_qcd = 2
alphas_order_qcd = 2
m_w = 80.352
m_z = 91.1876
m_up = 0.0
m_down = 0.0
m_strange = 0.0
m_charm = 1.51
m_bottom = 4.92
m_top = 172.5
alphas_type = "ipol"
number_flavors = 4
We can now convert the MAP22_grids_FF_Km_N3LL set by running the following command:
Once the conversion has been performed successfully (and the converted NeoPDF set
available in the $NEOPDF_DATA_PATH), we can inspect the content of the subgrids to make
sure that everything is correct.
> neopdf read subgrid --pdf-name MAP22.neopdf.lz4 --member 0 --subgrid-index 0 --pid 2 --kt-index 0 ─╯
Displaying grid for kT = 0.00010000000000000009
[x | Q2] 1.00000e0 2.40972e0 2.40972e1 4.14987e2 4.14987e3 1.00000e4
1.00000e-1 -6.70867e-1 -4.80573e-1 -1.53370e-1 -1.26831e-2 1.49324e-2 0.00000e0
1.10684e-1 -7.26434e-1 -4.81932e-1 -1.40332e-1 -7.62762e-3 1.61799e-2 0.00000e0
1.41421e-1 -7.37791e-1 -3.84220e-1 -8.14145e-2 8.54183e-3 1.92982e-2 0.00000e0
1.80695e-1 -5.23889e-1 -1.84548e-1 -1.28827e-2 2.17623e-2 1.98305e-2 0.00000e0
2.00000e-1 -3.89947e-1 -1.06392e-1 7.02618e-3 2.38316e-2 1.86428e-2 0.00000e0
We can verify that the contents of the subgrids are correct by checking one of the entries: