NPL News Now

April 24, 2017
COMPASS publishes first hint of sign change in Drell-Yan Sivers function

The COMPASS collaboration at CERN submitted their 2015 measurement for publication in Physical Review Letters. The Sivers amplitude from the 2015 COMPASS spin-dependent Drell-Yan data provides the first hint of a sign change of the Sivers function measured in Drell-Yan (DY) as compared to measured in Semi-Inclusive Deep-Inelastic scattering (SIDIS). This sign change is a fundamental prediction of Quantum Chromo Dynamics, or QCD, the underlying theory of the strong interaction between quarks in the proton. The sign change is a milestone of the Nuclear Science Advisory Committee (NSAC). The Sivers function is one of the proton's Transverse-Momentum Dependent parton distributions (TMDs) and describes the correlation between the transverse spin of the parent proton and the transverse momentum of the probed quark. COMPASS has previously measured the Sivers amplitude in SIDIS and is therefore in the unique situation to conclude on the sign change without involving uncertainties related to TMD evolution.
The UIUC COMPASS group has significantly contributed to the success of the measurement in terms of instrumentation, coordination and data analysis. The Illinois authors are: Vincent Andrieux, Ihn-Jea Choi, Francesca Giordano, Robert Heitz, Jaakko Koivuniemi, Yakov Kulinich, Alain Magnon, Naomi Makins, Marco Meyer, Jen-Chieh Peng, Matthias Grosse Perdekamp, and Caroline Riedl. The arXiv version of the paper is available here: https://arxiv.org/abs/1704.00488.
A second COMPASS run of spin-dependent DY in 2018 will enhance the statistical significance of the measurement.

April 6, 2017
sPHENIX 2016 Test Beam Paper submitted

The sPHENIX combined calorimeter test beam paper from the 2016 Fermilab test has been submitted to the IEEE Transaction of Nuclear Science. The electromagnetic calorimeter was built half at the NPL and half at Tungsten Heavy Powder with finishing work done at the NPL. The Illinois group also led the analysis of the electromagnetic calorimeter performance. Facilities at the MRL were used by to characterize the properties of the tungsten powder used in the calorimeter. The Illinois contribution (over 20% of the authors) was the largest of any institution except for Brookhaven’s. The Illinois authors are: Virginia Bailey, John Blackburn, Michael Higdon, Simon Li, Vera Loggins, Mike Phipps, Anne Sickles, Peter Sobel, and Eric Thorsland. The tested calorimeters were found to meet the sPHENIX physics requirements. The paper is available here: https://arxiv.org/abs/1704.01461

March 16, 2017
4th year of CCD funding approved for nEDM project

On Mar. 15 we received word from NSF that the final year of funding for the Critical Component Demonstration phase of the neutron electric dipole moment experiment (nEDM) is approved for release. The Illinois group (Beck, Peng, Williamson, Koivuniemi, Thorsland, Blackburn, Sobel, Rao, Sharma) is responsible for the so-called helium-3 services subsystem of the experiment. These funds will allow us to complete the dilution refrigerator, under construction at NPL, and used to cool the subsystem, as well as to make progress on components of both its injection and purification assemblies. The NSF also re-stated its commitment to provide $5.8M for the Large Subsystem Integration activities to follow the CCD phase of the experiment and to be shared between Illinois and Caltech.

February 21, 2017
Testing cryogenic electronics for nEXO

As a next-generation tonne scale double beta decay experiment, nEXO requires new development in detector technology. One key area is the development of low noise front-end electronics that can operate directly in liquid xenon (~170 K). In collaboration with the Brookhaven National Lab, students Shaolei Li and Xuanying Li are testing the performance of prototype boards built with custom ASICs. In the coming weeks, they will develop codes to readout all channels of the board and analyze the noise correlation between different channels. The board will later be used in liquid xenon test setups by the collaboration.

February 17, 2017
Caroline Riedl as next Technical Coordinator of the COMPASS experiment at CERN

Caroline Riedl was elected by the COMPASS collaboration board as next Technical Coordinator of the COMPASS experiment at CERN. Her term will start in July 2017. It will cover the no-beam period of "change-over" in fall / winter 2017/2018 during that the experiment's target region will be entirely modified to prepare for the second COMPASS Drell-Yan run in 2018 with a negatively charged pion beam: a transversely polarized ammonia target employing dynamic nuclear polarization, and a hadron absorber to stop all particles except for muons. In 2017, COMPASS is running with negatively or positively charged polarized muon beams and an unpolarized long liquid hydrogen target.

February 17, 2017
Caroline Riedl awarded Blue-Waters Campus Allocation for COMPASS data production

On November 27, 2016, Caroline Riedl was awarded an Illinois Blue Waters allocation for the duration of one year and 200,000 node hours to continue the evaluation of COMPASS data production on the Blue-Waters supercomputer. The UIUC team consisting of PI Riedl, postdoctoral researcher Vincent Andrieux, graduate students Marco Meyer and Robert Heitz, and Professor Matthias Grosse Perdekamp together with collaborators from other COMPASS institutions launch mass productions of COMPASS experimental and simulated data on Blue Waters. Per year of data taking, the COMPASS experiment at CERN accumulates more than 2.5 petabytes of experimental and simulated data. In a previous exploratory phase on Blue Waters in 2016, Dr. Riedl and her UIUC team had successfully tested data transfers between CERN and Blue Waters and mass productions on Blue Waters and had demonstrated that Blue Waters can significantly speed up (in the case of experimental data "tracking") and improve (in the case of simulated Monte-Carlo data) COMPASS data production.

February 16, 2017
Professor Yang Awarded NSF Career Award

We are excited to announce that Prof. Liang Yang has been awarded an NSF Career Award for the period 2017-2021 in the amount of $750k. This is a very competitive NSF-wide program that “offers the National Science Foundation's most prestigious awards in support of early-career faculty who have the potential to serve as academic role models in research and education and to lead advances in the mission of their department or organization.” Prof. Yang will use the support primarily for work associated with EXO-200, the ground-breaking Xe-136 neutrinoless double beta decay experiment for which he serves as co-spokesperson. The focus will be on data-taking and analysis over the next few years as the collaboration works to improve, in particular, the energy resolution of the experiment. In addition to providing one of the most stringent constraints on the existence of so-called Majorana neutrinos (neutrino is its own anti-particle), EXO-200 also serves as a test bed for a possible tonne-scale experiment currently being planned by the community. Congratulations Liang!

January 26, 2017
New Arrivals at NPL

Over the past week, we have taken delivery of two precious shipments with materials from opposite ends of the periodic table. About 200 standard liters of helium-3, valued at something like $200k, arrived on loan from ORNL. It will be used for the nEDM dilution refrigerator and will enable us to reach temperatures of about 0.25 K above absolute zero with the relatively high cooling power of 75 mW. The 3He is used because when it evaporates from a mixture with ordinary helium, it cools the remaining liquid. We also received the first half of a shipment of about half a ton of tungsten powder for the next round of prototypes for the sPHENIX calorimeter. Tungsten, a dense metal, is used because it can stop particles, especially photons, in relatively short distances. The powder will be combined with scintillating fibers to construct the 96 elements of a single ‘module’ for the full detector. Both the dilution refrigerator and the calorimeter prototype will be built and tested at NPL in the coming few months.