Add CutGaussian distribution type#1312
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cemitch99 wants to merge 11 commits intoBLAST-ImpactX:developmentfrom
Open
Add CutGaussian distribution type#1312cemitch99 wants to merge 11 commits intoBLAST-ImpactX:developmentfrom
cemitch99 wants to merge 11 commits intoBLAST-ImpactX:developmentfrom
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cemitch99
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Feb 20, 2026
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| // factors determined by the first cutoff value: | ||
| f = m_cutX*m_cutX/2.0_prt; | ||
| ef = std::exp(-f); | ||
| r2scale = 1_prt - f*ef/(1_prt - ef); | ||
| r2 = -2_prt * std::log(1_prt - u1*(1_prt - ef)); | ||
| ln1 = std::sqrt(r2 / r2scale); |
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These lines (and the corresponding lines in the code blocks below) define the effect of the cutoff. As cutX -> infinity, this reduces to the Box-Mueller transformation defining the parameter ln1 that appears in Gaussian.H.
for more information, see https://pre-commit.ci
for more information, see https://pre-commit.ci
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This PR adds a new initial particle distribution type,
CutGaussian, that is similar to a 6D Gaussian, but it allows the user to specify an independent cutoff in each phase plane(x,px),(y,py), and(t,pt). The cut is performed in normalized Courant-Snyder variables corresponding to the user-supplied second moments or Twiss functions. As a result, this is equivalent to a cut corresponding to the (linearized) action in each plane.If the user would like to apply a circular or elliptical cut in the
(x,y)plane, this is more appropriately done using theApertureelement, which represents the effect of a transverse mask.The PR addresses Issue #1253