validphys.photon package

Submodules

validphys.photon.alpha module

Module that implements the alpha running

class validphys.photon.alpha.Alpha(theory, q2max)

Bases: object

Class that solves the RGE for alpha_qed

alpha_em(q)

Compute the value of the running alphaem.

Parameters

q (float) – value in which alphaem is computed

Returns

alpha_em – electromagnetic coupling

Return type

numpy.ndarray

alphaem_fixed_flavor_exa(q, alphaem_ref, qref, nf, nl)

Compute numerically the running alphaem for nf fixed.

Parameters

• q (float) – target scale

• alph_aem_ref (float) – reference value of alpha_em

• qref (float) – reference scale

• nf (int) – number of flavors

• nl (int) – number of leptons

Returns

alpha_em – target value of a

Return type

float

alphaem_fixed_flavor_trn(q, alphaem_ref, qref, nf, nl)

Compute the running alphaem for nf fixed at, at least, NLO, using truncated method. In this case the RGE for alpha_em is solved decoupling it from the RGE for alpha_s (so the mixed terms are removed). alpha_s will just be unused.

Parameters

• q (float) – target scale

• alph_aem_ref (float) – reference value of alpha_em

• qref (float) – reference scale

• nf (int) – number of flavors

• nl (int) – number of leptons

Returns

alpha_em at NLO – target value of a

Return type

float

compute_alphaem_at_thresholds()

Compute and store alphaem at thresholds to speed up the calling to alpha_em inside fiatlux: when q is in a certain range (e.g. thresh_c < q < thresh_b) and qref in a different one (e.g. thresh_b < q < thresh_t) we need to evolve from qref to thresh_b with nf=5 and then from thresh_b to q with nf=4. Given that the value of alpha at thresh_b is always the same we can avoid computing the first step storing the values of alpha in the threshold points. It is done for qref in a generic range (not necessarly qref=91.2).

compute_betas(regions)

Set values of betaQCD and betaQED.

find_region(q)

interpolate_alphaem(q)

Interpolate precomputed values of alpha_em.

Parameters

q (float) – value in which alpha_em is computed

Returns

alpha_em – electromagnetic coupling

Return type

float

validphys.photon.compute module

Module that calls fiatlux to add the photon PDF.

class validphys.photon.compute.Photon(theoryid, lux_params, replicas: list[int], save_to_disk=False, force_computation=False, q_in=100.0)

Bases: object

property error_matrix

Generate error matrix to be used in generate_errors.

property integral

Return the integral values.

property interpolator

Return the interpolator functions.

validphys.photon.compute.compute_photon_to_disk(theoryid, fiatlux, maxcores)

Function to compute the photon PDF set.

validphys.photon.constants module

validphys.photon.structure_functions module

class validphys.photon.structure_functions.F2LO(pdfs, theory)

Bases: StructureFunction

Analytically compute the structure function F2 at leading order.

fxq(x, q)

Analytically compute F2LO.

Parameters

• x (float) – Bjorken x

• q (float) – DIS hard scale

Returns

F_2^{LO} – Structure function F2 at LO

Return type

float

class validphys.photon.structure_functions.FLLO

Bases: StructureFunction

Analytically compute the structure function FL at leading order., i.e. return zero.

fxq(x, q)

FL_LO = 0

class validphys.photon.structure_functions.InterpStructureFunction(path_to_fktable, pdfs)

Bases: StructureFunction

Compute an interpolated structure function convoluting an FKtable with a PDF.

fxq(x, q)

Compute the DIS structure function interpolating the grid.

Parameters

• x (float) – Bjorken x

• q (float) – DIS hard scale

Returns

F_{2,L} – Structure function F2 or FL

Return type

float

class validphys.photon.structure_functions.StructureFunction

Bases: ABC

Abstract class for the DIS structure functions

abstract fxq(x, q)

Abstract method returning the value of a DIS structure functions.

Parameters

• x (float) – Bjorken x

• q (float) – DIS hard scale

Returns

F_{2,L} – Structure function F2 or FL

Return type

float

Module contents