What does the star mean in $\rightarrow ZZ^{(∗)}$? Z boson can neither be positive nor negative. &quot;For masses above 130 GeV, Higgs-boson decays, H $\rightarrow ZZ^{(∗)}$, where each Z decays to a pair of oppositely charged leptons, would provide the experimentally cleanest channel to study the properties of the Higgs boson.&quot; Quoted from &quot;The ATLAS Experiment at the CERN Large Hadron Collider&quot;  page 2 or 3
I can always find that in some articles the production of higgs decay written as &quot;$\rm H\to {ZZ}^*\to 4l$&quot;, &quot;$\rm H\to ZZ\to 4l$&quot;, &quot;$\rm H\to Z\gamma^*\to\ldots$” What dose it mean when some particles with a superscript *? Such as “$\rm Z^*, W^*, \gamma^*, \ldots$&quot;. What’s the difference between them and &quot;$\rm Z, W, \gamma$&quot;?
How do we show that equality holds in the triangle inequality $|a+b|=|a|+|b|$ iff both numbers are positive, both are negative or one is zero? I already showed that equality holds when one of the three conditions happens.