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Forward Spectator Detector for CBM

Radim Dvorak

TL;DR

The Forward Spectator Detector (FSD) is developed for the CBM experiment at FAIR to enable measurement of the reaction plane and collision centrality at very high rates. The design uses two scintillator planes (14 and 17 m downstream) with 4×4 cm pads (150×140 cm active area) read out by DiRICH+TRB electronics to detect primary protons and fragments. Flow is quantified via a Fourier decomposition of the azimuthal distribution and reconstructed using the Q_n analysis framework, employing a data-driven 3-subevent (and optionally 4-subevent) method to determine the event-plane resolution and to extract $v_n$ from correlations with measured particles. Performance studies using DCM-QGSM-SMM and Geant4 cbmroot show event-plane resolutions up to ~70% in both directions, with modest degradation from detector acceptance and some sensitivity to the magnetic field; the detector can reproduce directed flow $v_1$ for pions in forward rapidity with good accuracy, validating its use for high-rate flow measurements and centrality determinations at SIS-100 energies.

Abstract

The development of the Forward Spectator Detector (FSD) for the CBM experiment represents a crucial step toward successful realization of the CBM physics program - understanding of highly compressed nuclear matter at the forthcoming FAIR facility. Designed for detecting collision participants at high collision rates at the SIS-100 accelerator, the FSD employs scintillator-based detector technology to accurately reconstruct the reaction plane and to determine the centrality of the collision. Overview of the technical design and performance studies conducted for the FSD is provided.

Forward Spectator Detector for CBM

TL;DR

The Forward Spectator Detector (FSD) is developed for the CBM experiment at FAIR to enable measurement of the reaction plane and collision centrality at very high rates. The design uses two scintillator planes (14 and 17 m downstream) with 4×4 cm pads (150×140 cm active area) read out by DiRICH+TRB electronics to detect primary protons and fragments. Flow is quantified via a Fourier decomposition of the azimuthal distribution and reconstructed using the Q_n analysis framework, employing a data-driven 3-subevent (and optionally 4-subevent) method to determine the event-plane resolution and to extract from correlations with measured particles. Performance studies using DCM-QGSM-SMM and Geant4 cbmroot show event-plane resolutions up to ~70% in both directions, with modest degradation from detector acceptance and some sensitivity to the magnetic field; the detector can reproduce directed flow for pions in forward rapidity with good accuracy, validating its use for high-rate flow measurements and centrality determinations at SIS-100 energies.

Abstract

The development of the Forward Spectator Detector (FSD) for the CBM experiment represents a crucial step toward successful realization of the CBM physics program - understanding of highly compressed nuclear matter at the forthcoming FAIR facility. Designed for detecting collision participants at high collision rates at the SIS-100 accelerator, the FSD employs scintillator-based detector technology to accurately reconstruct the reaction plane and to determine the centrality of the collision. Overview of the technical design and performance studies conducted for the FSD is provided.
Paper Structure (3 sections, 7 equations, 3 figures)

This paper contains 3 sections, 7 equations, 3 figures.

Table of Contents

  1. Forward Spectator Detector for CBM experiment
  2. Measurement of the flow
  3. Performance studies

Figures (3)

  • Figure 1: \ref{['fig:cbm_model']} CBM experiment, \ref{['fig:proton_xy']} Distribution of hits from primary protons in rapidity $2.8<y<3.6$ in FSD. Red circle shows the subevents regions. IN: $r=[0,30]$ cm, MID: $r=[30,50]$ cm, OUT: $r=[50,70]$ cm.
  • Figure 2: Comparison of event-plane resolution calculated from primary protons and FSD hits dependent on the impact parameter $b$.
  • Figure 3: $v_1$ of pions in rapidity $2.2<y<2.4$ calculated using 4-subevent method. Symbols are calculated using FSD hits (y component - full symbols, x component - open symbols). The lines are obtained directly from the DCM-QGSM-SMM model.