What is the difference between string that make phontons and proton?

[Abidal Sala]

according to the string theory, what is the difference between the strings that make the photons and the strings that make the protons? photons don't have mass and protons do, does it all ultimately rely on simply how the strings vibrate, or what? do photons' strings have lowest energy possible, or they have very few strings, so that's why they are massless??

 

[mfb]

Protons are not elementary particles, they consist of quarks (with mass) and gluons (massless). In the Standard Model, this mass comes from the interaction with the Higgs field, the particles itself are introduced as massless. String theory should reproduce that, so no particles (apart from the Higgs boson) have an intrinsic mass, that just emerges from the interactions.