M. Karam Ouharou

In the first millionths of a second after the Big Bang, the universe was a roiling, trillion-degree plasma of quarks and gluons—elementary particles that briefly glommed together in countless combinations before cooling and settling into more stable configurations to make the neutrons and protons of ordinary matter. In the chaos before cooling, a fraction of these quarks and gluons collided randomly to form short-lived "X" particles, so named for their mysterious, unknown structures. Today, X particles are extremely rare, though physicists have theorized that they may be created in particle accelerators through quark coalescence, where high-energy collisions can generate similar flashes of quark-gluon plasma. My team at MIT's Laboratory for Nuclear Science and elsewhere have found evidence of X particles in the quark-gluon plasma produced in the Large Hadron Collider (LHC) at CERN, the European Organization for Nuclear Research, based near Geneva, Switzerland. T...

Atomic nuclei have only two ingredients, protons and neutrons, but the relative number of these ingredients makes a radical difference in their properties. Certain configurations of protons and neutrons, with ‘magic numbers’ of protons or neutrons arranged into filled shells within the nucleus, are more strongly bound than others. The rare nuclei with complete proton and neutron shells, which are termed doubly magic, exhibit particularly enhanced binding energy and are excellent test cases for studies of nuclear properties. The new theoretical calculations and experimental results from the ISOLTRAP team shed light on one of the most iconic doubly magic nuclei: tin-100. With 50 protons and 50 neutrons, tin-100 is of particular interest for studies of nuclear properties because, in addition to being doubly magic, it is the heaviest nucleus comprising protons and neutrons in equal number — a feature that gives it one of the strongest beta decays, in which a positron is em...

T he J/ψ meson (J/psi meson or psion) is a flavor-neutral meson about three times more massive than a proton. This particle consists of a charm and an anti-charm pair held together tightly via the strong force. It was discovered in two experiments unexpectedly in 1974, in the so-called ‘November Revolution’ of particle physics. This, in turn, led to the discovery of the charm quark, a heavier cousin of the up quark. It fetched the pioneers of the experiments — Burton Richter and Samuel Ting — the Physics Nobel prize in 1976, and, importantly, opened a new window in the field of high-energy physics. ATLAS, CMS and LHCb experiments have previously seen one or two J/ψ particles coming out of a single particle collision, but never before have they seen the simultaneous production of three J/ψ particles — until the new CMS analysis. The rarity of this process is reflected in the number of events found, which is a meager 5, out of almost 100 billion proton-proton interactions t...