Observable

class Observable : public madspace::FunctionGenerator

Kinematic observable evaluated for a selection of outgoing particles.

Selects particles by PDG id (pids), optionally groups them into tuples (select_pids) and sums the momenta of each tuple, then evaluates one ObservableOption for every selection [1]. Several PDG types may be combined, for example all jet flavours. The available observables are single-momentum functions (e, px, py, pz, mass, pt, p_mag, phi, theta, y, y_abs, eta, eta_abs), pair functions (delta_eta, delta_phi, delta_r, pair_mass, sfos_pair_mass), and the event-level sqrt_s. sfos_pair_mass is pair_mass restricted to same-flavour opposite-sign pairs, i.e. pairs whose PDG ids are id and -id (the l+ l- pairs of MadEvent’s mmll); it needs the signed PDG ids of the actual flavours in pids and cannot be combined with ordering. The same mechanism defines the observables used by Cuts and ObservableHistograms.

batch is the leading batch dimension. n is the number of selected particles and k the number of selections.

Arguments

  • momenta – float, shape (batch, n, 4) – the selected four-momenta.

Returns

  • observable – float, shape (batch,) or (batch, k) – the observable value, one per selection unless sum_observable collapses them.

References

Public Types

enum ObservableOption

Kinematic quantity computed by an Observable.

Values:

enumerator obs_e
enumerator obs_px
enumerator obs_py
enumerator obs_pz
enumerator obs_mass
enumerator obs_pt
enumerator obs_p_mag
enumerator obs_phi
enumerator obs_theta
enumerator obs_y
enumerator obs_y_abs
enumerator obs_eta
enumerator obs_eta_abs
enumerator obs_delta_eta
enumerator obs_delta_phi
enumerator obs_delta_r
enumerator obs_pair_mass
enumerator obs_sqrt_s
enumerator obs_sfos_pair_mass

Public Functions

Observable(const std::vector<int> &pids, ObservableOption observable, const nested_vector2<int> &select_pids, bool sum_momenta = false, bool sum_observable = false, const std::optional<ObservableOption> &order_observable = std::nullopt, const std::vector<int> &order_indices = {}, bool ignore_incoming = true, const std::string &name = "")
Parameters:

  • pids – PDG ids selecting the outgoing particles.

  • observable – Which ObservableOption to compute.

  • select_pids – Groups of PDG ids forming the tuples the pair / summed observables act on; empty selects every matching particle individually.

  • sum_momenta – Sum the four-momenta within each tuple before evaluating the observable.

  • sum_observable – Sum the computed observable over all selections.

  • order_observable – Optional observable used to sort the selections before order_indices is applied.

  • order_indices – After sorting by order_observable, keep only these positions.

  • ignore_incoming – Exclude the two incoming partons from the selection.

  • name – Label for the returned value.

inline ObservableOption observable() const

The kinematic quantity this observable computes.

inline const nested_vector2<me_int_t> &indices() const

Per-selection lists of particle indices the observable is evaluated on.

inline bool sum_momenta() const

Whether the tuple momenta are summed before evaluation.

inline bool ordered() const

Whether the selection is sorted first (e.g.

the leading jet). The entries of indices() are then positions in the sorted list, not particle indices.

inline std::vector<std::size_t> simple_observable_indices() const

Flat particle-index list for a single ungrouped, unsummed selection; empty otherwise.

inline std::string name() const

The label passed to the constructor.

bool not_found() const

True when no particle in the event matches the requested pids.

Public Static Attributes

static const std::vector<int> jet_pids

PDG ids commonly grouped as a jet.

static const std::vector<int> bottom_pids

PDG ids of the b quark.

static const std::vector<int> lepton_pids

PDG ids of the charged leptons.

static const std::vector<int> missing_pids

PDG ids treated as missing energy (neutrinos).

static const std::vector<int> photon_pids

PDG id of the photon.