Session CG: Mini-Symposium on the Future of Physics at RHIC I

Future Studies at RHIC

The previous decade at the Relativistic Heavy Ion Collider has been characterized by prolific and informative results illuminating the true nature of the quark-gluon plasma. Some of this data, in combination with recent results from the Large Hadron Collider, has indicated that there are a number of unexplained phenomena still requiring a detailed scientific dissection. In this talk, I will review the future heavy ion program at RHIC, including near-term plans focusing on heavy flavor physics and the geometry of smaller collision systems. Longer-term plans will also be discussed, including the phase II beam energy scan, and designs for a major detector upgrade in the form of sPHENIX.   

Prototype sPHENIX Calorimeters

The central barrel electromagnetic and hadronic calorimeters are a critical part of the upgrade plans for the evolution of the PHENIX detector at RHIC to the sPHENIX detector later in this decade. A robust program of jet physics in heavy ion collisions is enabled by uniform calorimetric coverage over the full azimuth and 2 units of pseudorapidity. The electromagnetic calorimeter is envisioned to be a compact tungsten-scintillating fiber sandwich, and the hadronic calorimeter is steel interspersed with scintillating plates with embedded fiber. Both calorimeters are planned to be read out with silicon photomultipliers. The design of the calorimeters will be described, and the status of prototype calorimeters being prepared for testing in a test beam will be reported.   

The forward sPHENIX detector design and its physics program

The PHENIX detector at RHIC is planing a complete new design to respond some of the physics questions which emerged after the recent discoveries at RHIC and LHC, namely how jets lose energy in a hot and dense medium with minimal share viscosity. Studies have been carried out also in designing a set of forward detectors (fsPHENIX) including high momentum resolution tracking, calorimetry and particle identification covering the pseudo-rapidity region of 1$<\eta<$4. The fsPHENIX can extends the heavy ion program performed by PHOBOS and BRAHMS in $p$+A and A+A collisions, deeply studying the initial state in such collisions and covering a broad baryon density phase space. Long range correlation can also be measured at RHIC for the first time. The forward region is also crucial for the spin program. Transverse spin asymmetries from Collins and Sivers effects in jets and Drell Yan yields in the unexplored large Feynman momentum $x_F$ region, where these effects are larger, would be accessible as well as small momentum fraction gluon contribution to the proton spin ($\Delta G$). Ultimately, fsPHENIX will be the hadron detector of the future ePHENIX in the eIC RHIC era. This presentation will briefly report the physics, the design and the performance in simulations of fsPHENIX.   

The sPHENIX Upgrade

Over the past decade the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory has undergone a number of upgrades to explore the properties of the Quark-Gluon Plasma (QGP). The next phase, called sPHENIX, replaces the current central arm spectrometer with a compact superconducting solenoid, electromagnetic and hadronic calorimetry optimized to study jets produced in p+p, p+A and A+A collisions at RHIC, and will be the first step in upgrading PHENIX for the eRHIC era. In this paper we will present the design of the sPHENIX detector, the physics capabilities of the sPHENIX detector and a path forward to ePHENIX, a detector for the eRHIC era.   

The STAR Heavy Flavor Tracker

The Heavy Flavor Tracker (HFT) is an on-going upgrade for the STAR detector at RHIC that aim to study heavy quark production. In relativistic heavy-ion collisions at RHIC, heavy quarks are primarily created from initial hard scatterings. Since their large masses are not easily affected by the strong interaction with QCD medium they may carry information from the system at early stage. The interaction between heavy quarks and the medium is sensitive to the medium dynamics; therefore heavy quarks are suggested as an ideal probe to quantify the properties of the strongly interacting QCD matter. The HFT detectors will study this via the topological reconstruction of open charm hadrons. The HFT that consists of a thin two layer inner Pixel vertex detector, and two outer concentric layers of silicon, the Silicon Strip Detector, and the Intermediate Silicon Tracker. We will show how this detector system can assess heavy flavor physics with great precision. An overview of the HFT that will be completed for the upcoming RHIC run-14, its expected performance, and current status will be presented.   

Run13 commissioning status of the STAR HFT prototype

The STAR experiment has installed a prototype of the Heavy Flavor Tracker (HFT) during RHIC run 13. The motivation of the HFT is to enhance STAR physics capability in measuring heavy quark production with the use of direct topological reconstruction of charmed hadrons. The Pixel detector, a sub-system of the HFT, was installed at $30\%$ of its full coverage. It utilizes active pixel sensors technology allowing high precision measurements. Located near the interaction point, hits from the HFT are associated with the tracks reconstructed in the Time Projection Chamber (TPC) in order to improve the track pointing resolution (DCA) by about two orders of magnitude. In this talk we will discuss the results of the engineering run, focusing on offline software and initial results.   

Calibration/Survey/Alignment studies of STAR HFT Pixel Detector

As a critical component of the STAR inner tracking detector -- Heavy Flavor Tracker (HFT), the pixel detector consists of 10 sectors with 400 million 20x20-micrometer pixels forming the two innermost layers of the HFT at radii of 2.5 and 8 cm, respectively. In Run-13, a three-sector prototype was installed and successfully integrated into STAR. To achieve physics goals of HFT, the alignment calibration of pixel detector to a high precision of $\sim$10 microns is essential. The precision alignment to map out each pixel position within the sector is carried out via a survey measurement utilizing a Coordinate Measurement Machine with a repeatability of a few micrometers. The global position parameters of the pixel sectors with respect to the STAR TPC will be obtained via a track-based alignment method with beam collisions. Particularly, the sensitive area of the pixel detector is designed to have some overlaps in order to complete the relative alignment between sectors using tracks passing through the overlap region. In this presentation, we will present the alignment calibration procedure for the HFT pixel detector. Status of the alignment calibration for the pixel detector prototype in Run-13 will be discussed.