Basic Syntax Rules

• Particle names (see Particle names) are separaged by space
• Use a ">" to separate the initial state particles from the final state ones.
• Use " x x > z > y y y " form to require particle z to appear in a s-channel intermediate state.
• Use " x x > y y y /z" form to exclude particle z to appear in any diagram.
• Use " x x > y6 z1 z3, (z1 > y1 z2, z2 > y2 y3), z3 > y4 y5" form to select only diagrams compatible with generation of y6 z1 z3 and with the decay of z1 into y1 and z2, z2 into y2 and y3, and z3 into y4 and y5. Note that specified intermediate particles are restricted to be close to the mass shell. Multi-labels (see below) can appear only for initial- and final-state particles, not for intermediate particles.
• Use the multi-label "p" to indicate a proton or an anti-proton.
  The symbol "p~" does not exist.
  The type of initial state (pp or ppbar or parton-parton fixed energy) is specified later, during the run, in the input-card.dat.
• Use the multi-label "j" to indicate a jet.
• If no coupling orders are given, MadGraph will minimize the number of QED couplings and maximize number of QCD couplings, to remove negligible but time-consuming contributions.

Process Examples

PROCESS	Sample Diagram	Notes
u u~ > d d~		The maximum number of QED couplings is automatically set to zero so only QCD is on. The QED  contributions (W,photon,Z) are now off.
u u~ > d d~ QED=2		Diagrams with two QED couplings are allowed, besides the default QCD couplings. This entails that all the possible contributions (W,gluon,photon,Z) appear. In total 4 diagrams appear.
u u~ > d d~ / w+ QCD=0		The maximum number of QCD couplings is set to zero, and the contribution from an internal W+ (or W-) are eliminated. As a result only the contributions from the exchange of a photon and a Z appear.
u u~ > z > d d~ a QCD=0		The maximum number of QCD couplings is set to zero, and the presence of a Z in an s-channel diagram is requested. As a result possible contributions from the exchange of a W in the t-channel or a photon in the s-channel are excluded.
g g > t t~ > b b~ e+ e- ve~ ve		This is t tbar production with semileptonic decays for both tops. Automatically, the maximum number of QCD couplings is set to 2 and the QED is set to 4. The requirement of having the two top on-shell, avoids the generation of non resonant contributions such as gg>bb~ZZ with the subsequent decays of the Z's, giving in total 203 diagrams instead of just 3. Note that in general, the decay chain syntax below is better for decay processes.
u u > ul ul, ul > u n1, (ul > u n2, (n2 > e+ el-, el- > e- n1))		SUSY u squark pair production, with different decay of the two squarks. Only diagrams compatible with the chosen decay chain are generated, and the ul, n2, and el- are required to be within the Breit-Wigner in the following event generation.

Process Input Examples using Protons and Jets  

PROCESS	Directories	Subprocesses		Notes
p p > e+ ve	Pdxu_e+ve Pudx_e+ve	d~ u -> e+ ve u d~ -> e+ ve	s~ c -> e+ ve c s~ -> e+ ve	The special codes p and j, sum over gluon, and n light quark flavors and their anti_particles, as specified by the option. MadGraph is able to identify and combine explicitly identical subprocesses.
p p > W+ j j, W+ > l+vl	Puxu_e+veuxd Puu_e+veud ...	u~ u -> e+ ve u~ d g g -> mu+ vm s c~ ...	u~ u -> mu+ vm u~ d g g -> e+ ve s c~ ...	In this example, W + jets production is requested, with the subsequent leptonic decay of the W+. If l = e , mu is chosen in the options, then both possibilities are included. MadGraph is able to identify and combine explicitly identical subprocesses.