Fermilab research associates Kevin Pedro and Nadja Strobbe from the CMS group both presented talks on LHC physics result. Pedro spoke on searches for new physics with unconventional signatures at both the ATLAS and CMS experiments. The interest in unusual signatures is driven by the fact that many researchers have already searched for more commonly accepted physical processes. Looking for the unconventional opens up the possibility of unanticipated discoveries. Pedro covered long-lived particles emerging from a complex dark matter sector. The signature for this possible physics result is a jet that originates far from the interaction vertex. He also covered long-lived particles that disappear in the detector. This is a signature for a form of supersymmetry.
Strobbe presented a thorough overview of searches for strong-force-produced signatures of supersymmetry. She covered both ATLAS and CMS results, covering a broad range of signatures, including the associated production of b quarks and Higgs bosons, diphotons, several stop squark analyses, and the associated production of three bottom quarks and missing transverse momentum. In total, she presented 12 distinct analyses. The phenomenology of strong-force-produced supersymmetry is diverse, and it provides a rich source for the possible discovery of new physics. This is Strobbe’s last Moriond presentation as a Fermilab research associate, as she has recently accepted a faculty position at the University of Minnesota, where she will be starting in the fall.
Strobbe and Pedro were not the only people associated with the LHC Physics Center presenting or involved at Moriond. Fermilab Senior Scientist Boaz Klima has long been a member of the organizing committee. Meng Xiao (Johns Hopkins) and Greg Landsberg (Brown) also presented.
More broadly, many interesting physics topics were covered at the conference. The LHCb experiment announced the discovery of new pentaquarks containing charm quarks. They also reported that a peak in the data that was previously thought to be a single pentaquark was actually two distinct particles. Studies of mesons containing both bottom and charm quarks were very well-represented, with ATLAS, CMS and LHCb all making presentations. In the first week of the Moriond conference, both ATLAS and LHCb announced studies in the matter-antimatter asymmetry in decays of mesons containing both bottom and strange quarks. And in an example of very quick inter-collaboration cooperation, the experiments presented a combined result in the second week.
While the LHC is best known for colliding two beams of protons (studies of which were well represented at Moriond), the LHC also collides lead ions to study the behavior of superhot quark matter – what is called quark-gluon plasma. ALICE presented studies of charmed mesons called J/psi, which showed that charm quarks are affected in quark-gluon plasmas, just like lighter quarks. The ALICE experiment presented data gathered in a special run of proton-proton collisions at an energy unusual for the LHC an observation of charmed baryons in LHC collisions. These particles occur more often in proton-proton collisions than in electron-positron ones.
The Moriond conference is a fascinating one. It is small and cozy and allows for conversations and collaboration between researchers, with a storied history of over half a century. In its 53rd year, researchers are showing that its second half century will be just as exciting.
Don Lincoln is a Fermilab scientist on the CMS experiment.