file DecayBit/MSSM_H.hpp
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Namespaces
| Name |
|---|
| Gambit TODO: see if we can use this one: |
| Gambit::DecayBit |
| Gambit::DecayBit::MSSM_H |
Detailed Description
Higgs boson decays to supersymmetric particles at tree-level from
The Anatomy of Electro-Weak Symmetry Breaking. II: The Higgs bosons in the Minimal Supersymmetric Model Abdelhak Djouadi arXiv:hep-ph/0503173
I refer to equations in v2 (https://arxiv.org/abs/hep-ph/0503173v2).
Source code
// GAMBIT: Global and Modular BSM Inference Tool
// *********************************************
/// \file
///
/// Higgs boson decays to supersymmetric particles at tree-level from
///
/// The Anatomy of Electro-Weak Symmetry Breaking. II:
/// The Higgs bosons in the Minimal Supersymmetric Model
/// Abdelhak Djouadi
/// arXiv:hep-ph/0503173
///
/// I refer to equations in v2 (https://arxiv.org/abs/hep-ph/0503173v2).
///
/// \example MSSM_H.cpp
///
/// *********************************************
///
/// Authors (add name and date if you modify):
///
/// \author Andrew Fowlie
/// (andrew.fowlie@monash.edu)
/// \date 2018 May
///
/// *********************************************
#ifndef DECAYBIT_INCLUDE_GAMBIT_DECAYBIT_MSSM_H_HPP_
#define DECAYBIT_INCLUDE_GAMBIT_DECAYBIT_MSSM_H_HPP_
#include <cmath>
#include <array>
#include <stdexcept>
namespace Gambit {
namespace DecayBit {
namespace MSSM_H {
double lambda(double x, double y, double z) {
/**
@brief Phase-space function (similar to Kallen function)
\f[
\lambda(x, y; z) = (1 - x / z - y / z)^2 - 4 x y / z^2
\f]
*/
if (z == 0.) {
throw std::invalid_argument("z must be greater than zero");
}
return pow(1. - x / z - y / z, 2) - 4. * x * y / pow(z, 2);
}
double gamma_h_chi_gL(std::array<double, 2> m,
double gL,
double mh = 125.,
double mw = 80.385,
double GF = 1.1663787e-5) {
/**
@brief Eq. 2.56 for charginos or neutralinos
@returns \f$\Gamma(h \to \chi_i \chi_j)\f$ in GeV
@param m Masses of final state particles
@param gL Coupling \f$g_L\f$ in Eq. 1.112
@param mh Lightest Higgs mass, \f$m_h\f$
@param mw W-boson mass, \f$M_W\f$
@param GF Fermi constant, \f$G_F\f$
*/
const double eps_2 = 1.;
const double gR = gL * eps_2;
// Phase-space
if (std::fabs(m[0]) + std::fabs(m[1]) >= mh) {
return 0.;
}
const double l = lambda(pow(m[0], 2), pow(m[1], 2), pow(mh, 2));
if (l <= 0.) {
return 0.;
}
// Eq. 2.56 without common factor (without f$\sin\theta_W\f$ which cancels)
const double gamma_no_prefactor = std::sqrt(l) * ((
pow(gL, 2) + pow(gR, 2)) * (1. - (pow(m[0], 2) + pow(m[1], 2)) / pow(mh, 2))
-4. * gL * gR * m[0] * m[1] / pow(mh, 2));
// Eq. 2.56 with common factor
return GF * pow(mw, 2) / (2. * M_SQRT2 * M_PI) * mh * gamma_no_prefactor;
}
double gamma_h_chi_0(int i,
int j,
std::array<double, 4> m,
std::array<std::array<double, 4>, 4> Z,
double alpha,
double mh = 125.,
double mw = 80.385,
double GF = 1.1663787e-5,
double sw2 = 0.22) {
/**
@brief Lightest Higgs boson decay to neutralinos at tree-level in GeV
@warning Arguments \f$i\f$ and \f$j\f$ are zero-based
@warning Tree-level formula
@returns \f$\Gamma(h \to \chi_i \chi_j)\f$ in GeV
@param i Neutralino \f$\chi_i\f$ in final state
@param j Neutralino \f$\chi_j\f$ in final state
@param m Neutralino mases with phases
@param Z Real neutralino mixing matrix
@param alpha \f$\alpha\f$, Higgs mixing angle
@param mh Lightest Higgs mass, \f$m_h\f$
@param mw W-boson mass, \f$M_W\f$
@param GF Fermi constant, \f$G_F\f$
@param sw2 Weinberg angle, \f$\sin^2\theta_W\f$
*/
// Weinberg angle
const double tw = std::sqrt(sw2) / std::sqrt(1. - sw2);
// Eq. 1.113
const double e2 = -std::sin(alpha);
const double d2 = -std::cos(alpha);
// Eq. 1.112 (without \f$\sin\theta_W\f$ which cancels)
const double gL = 0.5 * (
(Z[j][1] - tw * Z[j][0]) * (e2 * Z[i][2] + d2 * Z[i][3]) +
(Z[i][1] - tw * Z[i][0]) * (e2 * Z[j][2] + d2 * Z[j][3]));
std::array<double, 2> mf{{m[i], m[j]}};
double gamma = gamma_h_chi_gL(mf, gL, mh, mw, GF);
if (i == j) {
gamma *= 0.5;
}
return gamma;
}
double gamma_h_chi_pm(int i,
int j,
std::array<double, 2> m,
std::array<std::array<double, 2>, 2> U,
std::array<std::array<double, 2>, 2> V,
double alpha,
double mh = 125.,
double mw = 80.385,
double GF = 1.1663787e-5) {
/**
@brief Lightest Higgs boson decay to charginos at tree-level in GeV
@warning Arguments \f$i\f$ and \f$j\f$ are zero-based
@warning Tree-level formula
@returns \f$\Gamma(h \to \chi^-_i \chi^+_j)\f$ in GeV
@param i Negative chargino \f$\chi^-_i\f$ in final state
@param j Positive chargino \f$\chi^+_j\f$ in final state
@param m Chargino masses
@param U Real chargino mixing matrix
@param V Real chargino mixing matrix
@param alpha \f$\alpha\f$, Higgs mixing angle
@param mh Lightest Higgs mass, \f$m_h\f$
@param mw W-boson mass, \f$M_W\f$
@param GF Fermi constant, \f$G_F\f$
*/
// Eq. 1.113
const double e2 = -std::sin(alpha);
const double d2 = -std::cos(alpha);
// Eq. 1.111 (without \f$\sin\theta_W\f$ which cancels)
const double gL = M_SQRT1_2 *
(e2 * V[j][0] * U[i][1] - d2 * V[j][1] * U[i][0]);
std::array<double, 2> mf{{m[i], m[j]}};
return gamma_h_chi_gL(mf, gL, mh, mw, GF);
}
double gamma_h_chi(std::array<double, 2> m_pm,
std::array<double, 4> m_0,
std::array<std::array<double, 2>, 2> U,
std::array<std::array<double, 2>, 2> V,
std::array<std::array<double, 4>, 4> Z,
double alpha,
double mh = 125.,
double mw = 80.385,
double GF = 1.1663787e-5,
double sw2 = 0.22) {
/**
@brief Lightest Higgs boson decay to neutralinos and charginos at
tree-level in GeV
@warning Tree-level formula
@returns \f$\Gamma(h \to \chi\chi)\f$ in GeV
@param m_pm Chargino masses
@param m_0 Neutralino mases with phases
@param U Real chargino mixing matrix
@param V Real chargino mixing matrix
@param Z Real neutralino mixing matrix
@param alpha \f$\alpha\f$, Higgs mixing angle
@param mh Lightest Higgs mass, \f$m_h\f$
@param mw W-boson mass, \f$M_W\f$
@param GF Fermi constant, \f$G_F\f$
@param sw2 Weinberg angle, \f$\sin^2\theta_W\f$
*/
double gamma = 0.;
for (int i = 0; i <= 3; i += 1) {
// Do not double count e.g. 12 and 21 - they are not distinct
for (int j = i; j <= 3; j += 1) {
gamma += MSSM_H::gamma_h_chi_0(i, j, m_0, Z, alpha, mh, mw, GF, sw2);
}
}
for (int i = 0; i <= 1; i += 1) {
// Do count e.g. 12 and 21 - they are distinct
for (int j = 0; j <= 1; j += 1) {
gamma += MSSM_H::gamma_h_chi_pm(i, j, m_pm, U, V, alpha, mh, mw, GF);
}
}
return gamma;
}
} // namespace MSSM_H
} // namespace DecayBit
} // namespace Gambit
#endif // DECAYBIT_INCLUDE_GAMBIT_DECAYBIT_MSSM_H_HPP_
Updated on 2024-07-18 at 13:53:34 +0000