ND workshop: From here to there

DUNE held a Near Detector Workshop at Fermilab on March 27-29 to launch the Near Detector Concept Study. During his introduction, Mark Thomson welcomed everyone, both DUNE collaborators and interested scientists who are not yet members of DUNE, emphasizing the broad international partnership that is required for this effort.

Starting from the Near Detector Task Force Report (see Near Detector Task Force achieves goal), the Concept Study will develop a proposal for the Near Detector (ND) conceptual design that meets DUNE’s primary scientific goals, along with a plausible funding model, by the end of 2017.

The detector technology options studied by the Task Force include a low-density tracker (for example, the fine-grained tracker proposed at CD-1 in 2015), a high-pressure TPC, and a LArTPC. The Concept Study will look at these individually, in various combinations with each other, and with additional detector elements, such as a magnet or an electromagnetic calorimeter.

The collaboration expects to narrow the options to two or three detector concepts by the May collaboration meeting, and document the pros and cons of each by June. Representatives from the Concept Study will present the options at the August collaboration meeting, at which time the collaboration may downselect.

“We have a number of tools in place, we are not starting from zero,” said Thomson. “It is important to base our choices on the identification of key measurements, VALOR-style fits, and experience – keeping in mind likely contributors and funding levels.”

Dan Dwyer of LBNL offered “a modest proposal” for arriving at a ND that will provide the necessary systematic constraint to the CP violation measurement. It involves making a set of critical measurements in both a low-density tracker and in a LArTPC, and thus requires a combined-technology ND.

“There seems to be some consensus on a LArTPC forming at least part of the ND,” said James Sinclair of the University of Bern. “If the LBNL simulations are correct (see last month’s article) then the amount of LAr required is, pleasingly, not far from what is already being prototyped.”

Event pileup – i.e., too many events – is likely, however, given the slow drift in the TPC. It is possible that development of a scalable pixel readout could mitigate this problem, and the effort in this area by LBNL and Bern is promising.

“Well, Herr Mozart! An excellent effort! But there are simply too many notes, that’s all.” Special thanks to Gerald Gugliemo of Fermilab for the artwork.

“The need to magnetize remains an open and interesting question,” added Sinclair. “From Justo Martín-Albo’s simulations, it is clear that the magnet would need to be relatively low-mass; large return yokes simply cause too many background events in ND environments.”

Kam-Biu Luk, the Near Detector Coordinator, concluded the workshop by offering a near-term plan of action to get “from here to there.” He proposed forming interest groups to address four areas: scientific requirements, capabilities of detector subsystems, exploring technology combinations, and investigating tools for fast turnaround studies.

“We need to meet the schedule and keep everyone informed as this effort proceeds,” he said. “But as we focus on the key parameters that we must measure well, let’s also try to allow for new physics processes that may become important in the next 20-30 years.”

(Images that included Dr. Seuss images were removed 22 May 2017.)