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sPHENIX is a new experiment under construction for the Relativistic Heavy Ion Collider at Brookhaven National Laboratory which will study the quark-gluon plasma to further the understanding of QCD matter and interactions. A prototype of the sPHENIX electromagnetic calorimeter (EMCal) was tested at the Fermilab Test Beam Facility in Spring 2018 as experiment T-1044. The EMCal prototype corresponds to a solid angle of $ \Delta \eta \times \Delta \phi = 0.2 \times 0.2$ centered at pseudo-rapidity $\eta = 1$. The prototype consists of scintillating fibers embedded in a mix of tungsten powder and epoxy. The fibers project back approximately to the center of the sPHENIX detector, giving 2D projectivity. The energy response of the EMCal prototype was studied as a function of position and input energy. The energy resolution of the EMCal prototype was obtained after applying a position dependent energy correction and a beam profile correction. Two separate position dependent corrections were considered. The EMCal energy resolution was found to be $\sigma(E)/\langle E\rangle = 3.5(0.1) \oplus 13.3(0.2)/\sqrt{E}$ based on the hodoscope position dependent correction, and $\sigma(E)/\langle E\rangle = 3.0(0.1) \oplus 15.4(0.3)/\sqrt{E}$ based on the cluster position dependent correction. These energy resolution results meet the requirements of the sPHENIX physics program., Comment: 9 pages, 9 figures, 3 tables. Published in IEEE Transactions on Nuclear Science (vol. 68, no. 2, pp. 173-181, Feb. 2021). Revisions over previous version in response to referee and editor comments

The super Pioneering High Energy Nuclear Interaction eXperiment (sPHENIX) at the Relativistic Heavy Ion Collider (RHIC) will perform high precision measurements of jets and heavy flavor observables for a wide selection of nuclear collision systems, elucidating the microscopic nature of strongly interacting matter ranging from nucleons to the strongly coupled quark-gluon plasma. A prototype of the sPHENIX calorimeter system was tested at the Fermilab Test Beam Facility as experiment T-1044 in the spring of 2016. The electromagnetic calorimeter (EMCal) prototype is composed of scintillating fibers embedded in a mixture of tungsten powder and epoxy. The hadronic calorimeter (HCal) prototype is composed of tilted steel plates alternating with plastic scintillator. Results of the test beam reveal the energy resolution for electrons in the EMCal is $2.8\%\oplus~15.5\%/\sqrt{E}$ and the energy resolution for hadrons in the combined EMCal plus HCal system is $13.5\%\oplus 64.9\%/\sqrt{E}$. These results demonstrate that the performance of the proposed calorimeter system satisfies the sPHENIX specifications., Comment: 19 pages, 31 figures, 3 tables. Published in IEEE Transactions on Nuclear Science (Volume: 65 , Issue: 12 , Dec. 2018 ). Revisions over previous version in response to referee and editor comments, plus updating of references and acknowledgement

A new silicon detector has been developed to provide the PHENIX experiment with precise charged particle tracking at forward and backward rapidity. The Forward Silicon Vertex Tracker (FVTX) was installed in PHENIX prior to the 2012 run period of the Relativistic Heavy Ion Collider (RHIC). The FVTX is composed of two annular endcaps, each with four stations of silicon mini-strip sensors, covering a rapidity range of $1.2<|\eta|<2.2$ that closely matches the two existing PHENIX muon arms. Each station consists of 48 individual silicon sensors, each of which contains two columns of mini-strips with 75 $\mu$m pitch in the radial direction and lengths in the $\phi$ direction varying from 3.4 mm at the inner radius to 11.5 mm at the outer radius. The FVTX has approximately 0.54 million strips in each endcap. These are read out with FPHX chips, developed in collaboration with Fermilab, which are wire bonded directly to the mini-strips. The maximum strip occupancy reached in central Au-Au collisions is approximately 2.8%. The precision tracking provided by this device makes the identification of muons from secondary vertices away from the primary event vertex possible. The expected distance of closest approach (DCA) resolution of 200 $\mu$m or better for particles with a transverse momentum of 5 GeV/$c$ will allow identification of muons from relatively long-lived particles, such as $D$ and $B$ mesons, through their broader DCA distributions., Comment: version submitted to NIM