A feast of physics to tide us over until Moriond…

Feb 27, 2018

While awaiting the annual tartiflette of physics that is the Moriond conference, at the forefront of which will be the results of the LHC’s 13-TeV runs, it’s refreshing to take a look at some of the other research that has been going on around the Laboratory. We have a very rich and diverse programme and there have been some very interesting developments over recent months.

The LHC is becoming a dab hand at resolving decades-old enigmas. Following on from the Higgs boson and pentaquarks, we may soon be able to welcome the odderon to the collection of LHC physics results.

The TOTEM experiment studies what happens when LHC protons glance off each other and remain intact, rather than breaking up in the collision. In this so-called elastic scattering, there is nevertheless an interaction between the two protons, and it’s here that the odderon comes in. Back in the 1970s, Isaak Pomeranchuk proposed that elastic proton-proton scattering was mediated by a kind of quasi-particle carrying the strong interaction. This was duly named the pomeron in his honour.

The pomeron has even CP quantum numbers, but it later became clear that a CP-odd exchange could also be at work, and the term odderon was duly coined. In modern physics language, we associate these exchange processes with an even or odd number of gluons. What TOTEM has seen is not a direct observation, but a hint that the odderon might be there. A dedicated 900-GeV LHC run later this year, during which ATLAS’s ALFA detector will join the search, should clarify the behaviour of the cross-section observed by TOTEM that leads to the putative odderon. The crème fraîche on the tartiflette remains, however, that of a resonant enhancement, which has yet to be observed.

Meanwhile, the AD is enjoying a particularly productive and engaging period. The ALPHA experiment recently performed its first precision spectroscopic measurements on antihydrogen, launching a new era of precision antimatter physics. BASE has vastly improved the precision of the measurement of the antiproton’s magnetic moment. ALPHA-g and GBAR are preparing to measure the influence of gravity on antimatter. And the ELENA ring will soon come online to slow down antiprotons even further and vastly increase the trapping efficiency.

One of the more intriguing proposals to come to both the SPSC and INTC at their last meetings also involves the AD. We received a letter of intent to load antiprotons onto a truck and drive them to ISOLDE, where they could be used to study the exotic behaviour of unstable nuclei, in particular their outer skin. It’s a sign of the maturity of antimatter research at CERN that antiprotons have evolved from being a subject for research in their own right to a tool enabling other forms of research to be carried out. If a mobile antiproton trap does indeed prove to be feasible, combined AD-ISOLDE experiments could be shedding light on astrophysical processes by 2022.

The final thing I’d like to mention is the activities at the CERN neutrino platform, where work is progressing well on two prototype detectors that we are building to establish the technology for the Deep Underground Neutrino Experiment (DUNE), hosted by Fermilab in South Dakota. A smaller device has already provided nice tracks. ProtoDUNE-SP is being prepared for beam before the long shutdown at the end of the year, and both protoDUNEs will continue recording data with cosmic rays. With such a variety of work going on across CERN’s diverse range of facilities, there’s plenty to feast on at any time of the year, tiding us over until the next round of conferences. Bon appétit.

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