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QQbar_threshold
options Struct Reference

Options for \(q\bar{q}\) functions. More...

Public Attributes

contribution_factors contributions
 
double alpha_s_mZ = QQbar_threshold::alpha_s_mZ
 
alpha_s_options alpha_s_mu0
 
double m_Higgs = QQbar_threshold::m_Higgs
 
double Yukawa_factor = 1
 
double invariant_mass_cut = std::numeric_limits<double>::quiet_NaN()
 
double ml = 0
 
double r4 = std::numeric_limits<double>::quiet_NaN()
 
double alpha
 
double mu_alpha
 
int resum_poles = 6
 
SM beyond_QCD
 
scheme mass_scheme
 
production_channel production = production_channel::all
 
bool resonant_only
 
bool expand_s
 
bool double_light_insertion = false
 
bool ISR_const = false
 

Detailed Description

Options for \(q\bar{q}\) functions.

The default settings depend on the specific function. Members that are irrelevant to the considered function are ignored.

Member Data Documentation

◆ contributions

contribution_factors contributions

Specifies multiplicative factors for various contributions

Option for cross section, energy level and residue functions

See also
contribution_factors

◆ alpha_s_mZ

double alpha_s_mZ = QQbar_threshold::alpha_s_mZ

Specifies value of the strong coupling at the scale mZ

Option for cross section, energy level and residue functions.

See also
mZ, alpha_s_mu0

◆ alpha_s_mu0

alpha_s_options alpha_s_mu0
Initial value:
= {
std::numeric_limits<double>::quiet_NaN(),
std::numeric_limits<double>::quiet_NaN()
}

alpha_s_mu0 = {mu0, alpha_s} specifies a reference scale mu0 and the value alpha_s of the strong coupling constant at that scale. If set, this option overrides the alpha_s_mZ option.

For bottom-related functions decoupling to the four-flavour theory will be performed if mu0 is above the decoupling scale mu_thr. For lower values of mu0 it is assumed that alpha_s is given in the four-flavour theory.

Option for cross section, energy level and residue functions.

See also
mZ, alpha_s_mZ

◆ m_Higgs

double m_Higgs = QQbar_threshold::m_Higgs

Specifies the value of the Higgs boson mass.

Option for cross section, energy level and residue functions.

◆ Yukawa_factor

double Yukawa_factor = 1

Specifies a multiplier for the quark Yukawa coupling.

Option for cross section, energy level and residue functions.

◆ invariant_mass_cut

double invariant_mass_cut = std::numeric_limits<double>::quiet_NaN()

Specifies an invariant mass cut for the non-resonant contribution

TODO: check The invariant mass of the final-state particles will be restricted to the region between m - invariant_mass_cut and m + invariant_mass_cut. By default, the loosest possible cut invariant_mass_cut = m - mW is taken, which yields the total cross section.

Option for cross section functions.

◆ ml

double ml = 0

Specifies the value of the light (e.g. charm or bottom) quark mass

Option for all bottom- and top-related function. For the cross section functions, the implementation only includes corrections up to order = 1. For other functions also the corrections for order = 2 are included.

See also
double_light_insertion

◆ r4

double r4 = std::numeric_limits<double>::quiet_NaN()

Third-order coefficient for conversion between pole and MS scheme

Specifies the non-logarithmic coefficient in the conversion between the pole and the MS scheme at order == N3LO.

r4 is mostly equivalent to \(c_m^{(4)}(\mu = m(m))\) in [27], but r4 refers to the theory with nl as opposed to nl + 1 active flavours.

Option for cross section, energy level and residue functions.

◆ alpha

double alpha

Specifies the value of the running QED coupling constant.

Option for cross section, energy level and residue functions

◆ mu_alpha

double mu_alpha

Specifies the scale for the running QED coupling constant.

Option for cross section, energy level and residue functions

◆ resum_poles

int resum_poles = 6

Specifies the number of bound states that are resummed into the Green function.

Option for cross section functions.

See also
alpha_s, [Beneke:2014], [11]

◆ beyond_QCD

SM beyond_QCD

Specifies the corrections beyond QCD that should be taken into account.

Option for cross section, energy level and residue functions.

See also
SM

◆ mass_scheme

scheme mass_scheme

Specifies the renormalisation scheme and scale of the quark mass

Option for all bottom- or top-related functions

See also
mass_scheme

◆ production

Specifies which production channels are taken into account

Option for cross section functions.

See also
production_channel

◆ resonant_only

bool resonant_only

Specifies whether only the resonant production should be computed

Option for cross section functions.

◆ expand_s

bool expand_s

Specifies treatment of the global factor 1/s in the polarisation function

If set to true, 1/s is expanded around the threshold center-of-mass energy, i.e. the relation between the polarisation function and the PNRQCD Green function at leading order reads \(\Pi = \frac{N_c}{2m^2} G(E)\). If set to false, the factor is kept in unexpanded form, so that \(\Pi = \frac{2 N_c}{s} G(E)\) ar leading order.

Option for cross section and residue functions.

◆ double_light_insertion

bool double_light_insertion = false

Specifies whether effects from a non-zero light quark mass on double potential insertions are taken into account.

Setting this option to true usually has a small numerical impact on the final result and leads to a considerable slowdown. The current implementation is comparably fast, but not very accurate. Furthermore, it is not thread safe.

Option for energy level and residue functions.

◆ ISR_const

bool ISR_const = false

Specifies whether non-logarithmic initial-state raditation corrections are taken into account.

This should be set to true if and only if the resulting cross section is convoluted with the electron structure functions to resum the logarithmically enhanced ISR contributions.

Option for cross section functions.