Equation 2 · Part 8 · From Origins to Frontier: A History of Particle Physics Beyond the Standard Model

Symbol Lambda^4

\mathcal{L}_{\text{SMEFT}} = \mathcal{L}_{\text{SM}} + \sum_i \frac{c_i}{\Lambda^{2}} \mathcal{O}_i^{(6)} + \mathcal{O}\!\left(\frac{1}{\Lambda^{4}}\right)

\Lambda^{4}

What this part means

Lambd $a^4$ occurs below the fraction bar. The quantity above the bar is divided by this expression; zero is excluded as a denominator.

Its job in the formula

Lambd $a^4$ occurs below the fraction bar. The quantity above the bar is divided by this expression; zero is excluded as a denominator.

Full expressionSymbol Lambda^4Article meaning

The passage around this formula

The extended silence from direct searches for new particles pushed much of the theoretical community toward a different strategy: rather than assuming a specific new particle and calculating its signature, treat any new physics as too heavy to produce directly, and parametrize its indirect effects on Standard Model processes using an effective field theory (EFT). The Standard Model Effective Field Theory (SMEFT) adds higher-dimension operators, suppressed by inverse powers of some new physics scale $\Lambda$ , to the ordinary Standard Model Lagrangian: $\mathcal{L}_{\text{SMEFT}} = \mathcal{L}_{\text{SM}} + \sum_i \frac{c_i}{\Lambda^{2}} \mathcal{O}_i^{(6)} + \mathcal{O}\!\left(\frac{1}{\Lambda^{4}}\right)$ . Here each $\mathcal{O}_i^{(6)}$ is a dimension-six operator built from Standard Model fields respecting its gauge…

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Learn the underlying idea

An exponent tells how a base is used in multiplication. In x³, x is the base and 3 is the exponent: x³ = x × x × x.

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