Detector (final RHIC configuration, Runs 22–25; STAR coordinates, +z = West): TPC r 0.5–2.0 m, |z| < 2.1 m, 12 sectors per side, inner sectors upgraded (iTPC), |η| < 1.5 (Anderson et al., NIM A 499, 659, 2003; iTPC TDR, STAR Note SN0644). TOF 120 trays at r ≈ 2.16 m, |η| < 0.9. BEMC 4800 towers, Δη×Δφ = 0.05×0.05, r 2.23–2.63 m, |η| < 1, σE/E ≈ 14%/√E ⊕ 1.5% (Beddo et al., NIM A 499, 725, 2003). EEMC 720 towers, 1.086 < η < 2, z = 2.7 m (Allgower et al., NIM A 499, 740, 2003). MTD on the return-yoke backlegs, |η| < 0.5. Solenoid 0.5 T, coil r ≈ 2.64–2.93 m, 30 flux-return bars to r = 3.66 m, length 6.85 m (Bergsma et al., NIM A 499, 633, 2003; Ackermann et al., NIM A 499, 624, 2003).
Forward: EPD at |z| = 3.75 m, 2.14 < |η| < 5.09, 12 supersectors × 16 rows (Adams et al., NIM A 968, 163970, 2020). Forward upgrade (West, 2.5 < η < 4): FST (3 Si disks), FTT (4 sTGC stations), FCS ECal + HCal at z ≈ 7 m (STAR Forward Upgrade, STAR Note SN0648). VPD at |z| = 5.7 m; ZDCs at ±18 m. eTOF (East, −1.6 < η < −1.1; CBM–STAR, arXiv:1609.05102) is optional. Dimensions are approximate (published values), not the GEANT geometry.
Fixed target: 0.25 mm Au foil at z = 200.7 cm, 2 cm below the beam axis; beam travels West→East, so the fireball is boosted by yCM into the TPC (STAR BES-II/FXT, STAR Note SN0598; STAR, PRC 103, 034908, 2021).
Glauber MC: Woods–Saxon Au (R = 6.38, a = 0.535 fm), Cu (4.20, 0.596), Ru (5.085, 0.46), Zr (5.02, 0.52), O (2.608, 0.513); Hulthén deuteron; σNNinel(√s) from 22 mb (3 GeV) to 42 mb (200 GeV) (Miller et al., Ann. Rev. Nucl. Part. Sci. 57, 205, 2007).
Particles: two-component dN/dη of mesons, npp(√s) tuned to ≈ 690 for 0–5% Au+Au at 200 GeV (PHOBOS, PRC 83, 024913, 2011), Gaussian dN/dy with Landau width σ² = ln(√s/2mp). Participant protons with rapidity loss ≈ 2 units (full stopping at BES energies; STAR, PRC 96, 044904, 2017), light-nucleus (d) coalescence at low √s, K⁻/K⁺ and p̄/p rising with √s. v₂ from ε₂ with sign change below ≈ 4 GeV and proton v₁ slope at FXT energies (STAR, PLB 827, 137003, 2022).
Tracking: helices in B = 0.5 T inside the magnet, straight beyond. Hits: TOF, eTOF, FST, FTT, EPD, VPD. Towers: BEMC, EEMC, FCS ECal (22×34 × 5.5 cm per half) and HCal (13×20 × 10 cm per half). Charged hadrons leave MIP or partial EM showers; in the forward region they continue into the HCal (toy σ/E = 70%/√E). Neutral hadrons (participant neutrons, K⁰L) deposit mainly in the HCal; γ from π⁰, η → γγ. FCS ECal towers are drawn rising towards the IP, HCal towers away from it.