The total cross section should not depend on the renormalization and factorization scale. This mean that a cross-section computed at N

Hence it is possible to assess the impact of the neglected terms by studying how much the cross-section changes when varying the scales.

The scales are varied around the reference scale (RS).

The two possible choices "standard" and "conservative" correspond respectively in varying the ren/fact scales in the square

[1/2 RS, 2 RS]x[1/2 RS, 2 RS] (9 points)

and in the square

[1/4 RS, 4 RS]x[1/4 RS, 4 RS] (25 points).

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