boosts because it is built exclusively from transverse quantities. A disadvantage of $\delta$, however, is that it requires the inputs to have been ordered in some way, as in (\[eq:ptordering\]). It is by no means a requirement that non-standard parity violating effects should come together with an ordering requirement on momenta. It may also be useful, therefore, to consider completely symmetric pseudoscalars. These are pseudoscalars which (unlike $\delta$) do not change their value if their input momenta are re-ordered. Examples include the four completely symmetric pseudoscalars $S_1$, $S_2$, $S_3$ and $S_4$ defined by $$\begin{aligned}
S_1(p(1),p(2),p(3),p(4)) &= 
   \sum_{i,j,k,l=1}^3 
    [i,j,k,l]
   (i \cdot j)
   (i \cdot j)
      (i \cdot k)
         ,
\\
S_2(p(1),p(2),p(3),p(4)) &= 
   \sum_{i,j,k,l=1}^3 
    [i,j,k,l]
   (i\cdot j)
(i \cdot k)
   (j \cdot l)
     ,
\\
S_3(p(1),p(2),p(3),p(4)) &= 
   \sum_{i,j,k,l=1}^3 
    [i,j,k,l]
 (i \cdot i)
(j \cdot j)
(i \cdot k)
   \qquad\text{and}
\\
S_4(p(1),p(2),p(3),p(4)) &= 
   \sum_{i,j,k,l=1}^3 
    [i,j,k,l]
 (i \cdot i)
(j \cdot k)
(i \cdot j),
\label{eq:sfour}\end{aligned}$$ in which $(a\cdot b)$ stands for $p^\mu(a)p_\mu(b)$ and $[a,b,c,d]$ stands for $\epsilon_{\mu\nu\sigma\tau} p^\mu(a) p^\nu(b) p^\sigma(c) p^\tau(d)$. $S_1$ to $S_4$ are not dimensionless, but they could easily be made so in the same way as $\delta$ in (\[eq:delta\]).[^11]

The CMS Detector and Reconstructed Objects,\[Sec:CMS\]
======================================================

The data used in 