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setMandelstam5([k1:m1, k2:m2, k3:m3, k4:m4, k5:m5])
generates a list of generalised Mandelstam and mass shell substitutions for incoming particles with momentums k1
, k2
and k3
with masses m1
, m2
and m3
and outcoming particles with momentums k4
and k5
with masses m4
and m5
.setMandelstam5([k1:m1, k2:m2, k3:m3, k4:m4, k5:m5], s, t1, t2, u1, u2)
generates a list of Mandelstam substitutions with specified notation for generalised Mandelstam s, t1, t2, u1 and u2 variables.setMandelstam5
uses the following definition of Mandelstam variables:\begin{gather*} s = (p_1 + p_2)^2\\ t_1 = (p_1 - p_3)^2 \\ t_2 = (p_1 - p_4)^2 \\ u_1 = (p_2 - p_3)^2 \\ u_2 = (p_2 - p_4)^2 \\ \end{gather*}
Generate a list of Mandelstam and mass shell substitutions:
def mandelstam = setMandelstam5([k1_a: 'm1', k2_a: 'm2', k3_a: 'm3', k4_a: 'm4', k5_a: 'm5']) println mandelstam
> k1_{a}*k1^{a} = m1**2 > k2_{a}*k2^{a} = m2**2 > k3_{a}*k3^{a} = m3**2 > k4_{a}*k4^{a} = m4**2 > 2*k1_{a}*k2^{a} = s-m2**2-m1**2 > 2*k4^{a}*k3_{a} = s-m3**2-m4**2 > -2*k3^{a}*k1_{a} = t-m3**2-m1**2 > -2*k4^{a}*k2_{a} = t-m4**2-m2**2 > -2*k4^{a}*k1_{a} = -m4**2-m1**2+u > -2*k3^{a}*k2_{a} = -m3**2-m2**2+u
Same when some particles are massless:
def mandelstam = setMandelstam([k1_a: '0', k2_a: 'm2', k3_a: 'm3', k4_a: '0']) println mandelstam
> k1_{a}*k1^{a} = 0 > k2_{a}*k2^{a} = m2**2 > k3_{a}*k3^{a} = m3**2 > k4_{a}*k4^{a} = 0 > 2*k2^{a}*k1_{a} = -m2**2+s > 2*k4^{a}*k3_{a} = -m3**2+s > -2*k3^{a}*k1_{a} = -m3**2+t > -2*k4^{a}*k2_{a} = t-m2**2 > -2*k4^{a}*k1_{a} = u > -2*k2_{a}*k3^{a} = -m3**2+u-m2**2
Specify custom notation for Mandelstam variables:
def mandelstam = setMandelstam( [k1_a: 'm1', k2_a: 'm2', k3_a: 'm3', k4_a: 'm4'], 'hS', 'hT', 'hU') println mandelstam
> k1_{a}*k1^{a} = m1**2 > k2_{a}*k2^{a} = m2**2 > k3_{a}*k3^{a} = m3**2 > k4_{a}*k4^{a} = m4**2 > 2*k2^{a}*k1_{a} = -m1**2+hS-m2**2 > 2*k3_{a}*k4^{a} = -m3**2+hS-m4**2 > -2*k3^{a}*k1_{a} = -m3**2-m1**2+hT > -2*k2_{a}*k4^{a} = hT-m4**2-m2**2 > -2*k1_{a}*k4^{a} = -m1**2+hU-m4**2 > -2*k2_{a}*k3^{a} = -m3**2+hU-m2**2