MRI Consortium: Development of an Event Plane Detector for the sPHENIX Experiment at the Relativistic Heavy Ion Collider

This award will fund the construction, installation, and commissioning of an Event Plane Detector called the sPHENIX Event Plane Detector (sEPD) at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. At RHIC, nuclei are accelerated to nearly the speed of light, and then collided in order to form a droplet of matter so hot that the quarks and gluons which comprise the neutrons and protons of the nuclei are no longer confined.

Understanding this novel form of matter, called the Quark Gluon Plasma (QGP), allows a better understanding of the strong nuclear force and the mechanism by which sub-atomic matter organizes itself. The QGP rapidly expands and cools after its creation, and its properties are investigated through measurements of the resulting particles in the detectors.

The sEPD will allow each collision to be better characterized by measuring charged particles with fine segmentation in a region not covered by other detectors, and will therefore improve the precision of multiple measurements. Understanding how small a droplet of QGP at RHIC can exist is of fundamental interest and can only be determined using the increased precision granted by the sEPD.

The design and construction of the detector will be carried out at the university level, with strong involvement of undergraduate and graduate students, for whom such hands-on opportunities are increasingly rare. Students from underrepresented groups will be recruited in order to increase their participation in particle and nuclear physics detector development, where they have been historically poorly represented compared to physics as a whole.

The sPHENIX detector is currently under construction and will be commissioned for first data taking in 2023 at the Relativistic Heavy Ion Collider at Brookhaven National Laboratory. The sEPD will be a new detector that will be integrated into sPHENIX to deliver unique measurements of jet quenching anisotropy at RHIC. The proposal is to design, build, and install the sEPD in time for data taking in 2023.

The sEPD comprises two sub-detectors, one in each of the forward and backward angle regions. Each sub-detector comprises 12 azimuthal sectors, each with 31 segments. Each segment is a scintillator tile with an optical fiber embedded to extract the light signal, which is then read out via silicon photomultipliers (SiPMs).

The scintillator will be milled by CNC machines, with the optical fiber assemblies glued in by teams of students and post-docs. The electronics read-out chain will largely use electronics already designed for sPHENIX, but the boards for the SiPMs and the amplification circuit they require will be newly designed and assembled for the project. Each finished assembly will be tested using a radioactive strontium source in order to determine the measurement efficiency and to ensure that the internal mapping of the optical fibers is correct. The full sEPD detector will be assembled and installed at Brookhaven National Laboratory.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.