The three jewels in the crown of the LHC

Abstract

The ATLAS and CMS experiments have made three major discoveries: The discovery of an elementary spin-zero particle, the discovery of the mechanism that makes the weak interactions short-range, and the discovery of the mechanism that gives the third generation fermions their masses. I explain how this progress in our understanding of the basic laws of Nature was achieved.It is often stated that the Higgs discovery is "the jewel in the crown" of the ATLAS/CMS research. We would like to argue that ATLAS/CMS made (at least) three major discoveries, each of deep significance to our understanding of the basic laws of Nature:1. The discovery of an elementary spin-0 particle, the first and only particle of this type to have been discovered.2. The discovery of the mechanism that makes the weak interactions short-ranged, in contrast to the other (electromagnetic and strong) interactions mediated by spin-1 particles.3. The discovery of the mechanism that gives masses to the three heaviest matter (spin-1/2) particles, through a unique type of interactions.These three breakthrough discoveries can be related, in one-to-one correspondence, to three distinct classes of measurements:1. The Higgs boson decay into two photons.2. The Higgs boson decay into a W -or a Z-boson and a fermion pair, and the Higgs production via vector boson (W W or ZZ) fusion.3. The Higgs boson decay into fermion pairs, and the Higgs boson production in association with top-antitop pair.

Lessons from ATLAS and CMS measurements of Higgs boson decays to second generation fermions

“…The ATLAS and CMS collaborations measured the decays of the Higgs boson into a tau-lepton pair, h → τ + τ − , and into bottom-quark pair, h → b b, and the Higgs boson production in association with top-quark pair, pp → t th [1,2]. These measurements constitute a discovery of the mechanism that gives masses to the third generation fermions, as well as the discovery of Yukawa interactions among elementary particles [3]. More recently, the ATLAS and CMS experiments searched for the Higgs boson decays into second generation fermions.…”