 absence of a factor 2 in the denominator, unlike the Gaussians 
used to pick <i>(x, y, z)</i>.) 
  

<p/><code>parm&nbsp; </code><strong> Beams:sigmaTime &nbsp;</strong> 
 (<code>default = <strong>0.</strong></code>; <code>minimum = 0.</code>)<br/>
The width of a Gaussian distribution of the collision time (in units of
mm/c). Note that, if the above space parametrization is viewed as the
effect of two incoming beams along the <i>+-z</i> axis, with each beam
having a Gaussian spread, then the spread of the 