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   I do sometimes get asked “If you’ve found a Higgs boson, can you show me a picture of it?” Unfortunately, the answer is no. But the reason for this provides a resolution to a severe parental dilemma, and explains why I am in fact sometimes the tooth fairy. Bear with me.

  I can’t show you something which is definitely the new boson, but I can show evidence for it, for example in the picture below. It shows the distribution (black dots) of the mass you get when you combine the energy and momenta2 of pairs of photons (particles of light) in the ATLAS detector. The bump shows that there are more of these photon pairs at masses corresponding to around 125 GeV than would be expected from the trend. This excess implies the existence of a particle at about this mass which decays to pairs of photons.

   The bump3 in this plot would not be there unless there were a new boson (credit, ATLAS experiment and CERN). The key is that even if I show you a collision event with a pair of photons which exactly gives the “Higgs mass”, i.e. at the top of that peak, it is still not possible to be sure that this exact pair of photons came from a Higgs boson. There may be several possible ways of producing a set of new particles from the incoming ones; but if the resulting set is identical, it is not physically meaningful to say which way occurred.

     Now, to the parental dilemma. It is especially acute at this time of year, but if you have children who are losing their milk teeth, it is ever-present. Is the tooth fairy real? What about Father Christmas? Do you spoil the fun or do you lie? Something in me hates the idea of lying to my kids, and undermining4 trust. Here’s my way out. Anything which has the same initial state (tooth) and final state (money) might in fact be an event in which a tooth fairy was present. To put it another way, anything which removes the tooth and delivers money shares such an essential property with a tooth fairy that it can be said to be one (anything removing both teeth and money is probably a dentist. Or possibly a mugger5 ). 

      By now, my son doesn’t believe a word of it of course. But in the early days it was the truth. We managed this transition without lies, betrayal and tears because actually, when tiptoeing into the bedroom with a shiny pound coin, I really am the tooth fairy. I am of course also at the same time Dad. This seemed to work, and now he’s older, it’s still fun. It’s not much of stretch to extend this to Father Christmas, and it also explains why sometimes Father Christmas uses the same wrapping paper as your parents - he and they are, in a sense, indistinguishable quantum possibilities for the delivery process.

(theguardian.com/science/life-and-physics/2012/dec/23/tooth-fairy-quantum-mechanics Acesso em: 26.08.2013. Adaptado)

1Higgs boson: partícula subatômica teórica que ficou conhecida publicamente após ter sido divulgada como a “partícula de Deus”. Sua existência é associada a pesquisas acerca da origem do universo.

(topics.nytimes.com/top/reference/timestopics/subjects/h/higgs_boson/index.html Acesso em 02.10.2013. Adaptado)

2momenta: plural de momentum – conceito físico associado à quantidade de movimento de uma partícula.

3bump: choque ou elevação.

4undermine: tornar algo gradativamente mais fraco, especialmente a confiança ou autoridade de alguém.

5mugger: assaltante.