Synopsis: Explaining a 750 GeV Bump

Theorists try to explain data from the LHC that could be hinting at the existence of new particles.
Synopsis figure
Y. Nakai et al., Phys. Rev. Lett. (2016)

Late last year, two collaborations at the LHC reported hints that proton-proton collisions created more photon pairs (diphotons) than expected with energies of about 750 GeV (in the diphoton’s rest frame). Such a “bump” in the diphoton spectrum is very much like the signal that led to the discovery of the Higgs boson. The difference is that no one was expecting another such bump. If confirmed, it would imply the existence of surprising new particles.

This exciting hint has generated many theory papers (see Physical Review Letters’ Editorial: “Theorists React to the CERN 750 GeV Diphoton Data”). Most of the models proposed contain a new 750 GeV boson—6 times heavier than the Higgs boson—plus some other particles, such as new fermions that would couple the new boson to pairs of photons and to pairs of gluons generated by the LHC’s colliding protons.

Now, a quartet of papers, appearing in the same issue of Physical Review Letters, attempt to explain the origin of the 750 GeV signal. Three papers are centered around some new 750 GeV boson: a pion-like boson associated with a new type of strong force (Y. Nakai, R. Sato, and K. Tobioka), a Higgs-like boson that couples to new kinds of fermions (G. Li et al.), or a boson that is the supersymmetric partner of a hypothetical fermion called the goldstino (C. Petersson and R. Torre). The fourth paper (W. S. Cho et al.) explores the possibility that the diphoton excess is not due to a 750 GeV particle at all, but to some even heavier particles that decay via a cascade to lighter particles along with photon pairs of about 750 GeV.

By the fall of 2016, the LHC should have collected enough data to determine whether the hint is a real signal or a statistical fluctuation. If the former, researchers will eagerly delve into deciphering the new physics behind the signal.

This research is published in Physical Review Letters.

–Robert Garisto


Features

More Features »

Announcements

More Announcements »

Subject Areas

Particles and Fields

Previous Synopsis

Quantum Physics

Exciting Vibrations

Read More »

Next Synopsis

Related Articles

Synopsis: Space Measurements of Secondary Cosmic Rays
Astrophysics

Synopsis: Space Measurements of Secondary Cosmic Rays

New data from the International Space Station shed light on how secondary cosmic rays propagate through space. Read More »

Synopsis: Top Quark in Nuclear Collisions
Particles and Fields

Synopsis: Top Quark in Nuclear Collisions

The top quark—previously seen in proton collisions—has now been identified in collisions between protons and lead nuclei. Read More »

Synopsis: Minimum Mass of Magnetic Monopoles
Particles and Fields

Synopsis: Minimum Mass of Magnetic Monopoles

A new analysis places some of the tightest bounds yet on the mass that magnetic monopoles should have if they exist. Read More »

More Articles