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A novel design of general-purpose spectrometer with nucleon polarimeter function

Chuang-Xin Lin, Xiao-Rong Lv, Boxing Gou, Ai-Qiang Guo, Yu-Tie Liang

TL;DR

The paper proposes integrating a nucleon polarimeter into a general-purpose spectrometer to access final-state proton polarization without compromising four-momentum measurements. It details a HIAF-based Hyperon–Nucleon Spectrometer (H-NS) with a carbon polarimeter target and MAPS/LGAD detectors, optimized by MC studies to achieve ~70% signal efficiency and strong background rejection. Polarization is extracted from the azimuthal distribution of proton–carbon elastic scattering, using the average analyzing power and a self-calibration strategy with polarized protons from hyperon decays to extend measurements to higher energies. This design provides a benchmark for future experiments and links final-state polarization to four-momentum data, enabling deeper insight into spin dynamics, with considerations for high-multiplicity environments.

Abstract

The spin polarization of hadrons is a key observable for probing the details of particle and nuclear interactions, offering information not available from other measurements. Currently, general-purpose spectrometers lack the capability to access final-state polarization. A novel technique to measure nucleon polarization within such a spectrometer has been proposed. Using this technique, a new design based on the proposed hyperon-nucleon spectrometer is developed. Systematic optimization confirms that the nucleon polarimeter functions effectively without impairing the detector's conventional performance. This successful integration, the first attempt of the general-purpose spectrometer, sets a valuable benchmark for future experiments. Ultimately, correlating spin polarization with four-momentum data will lead to a more profound understanding of the underlying physics.

A novel design of general-purpose spectrometer with nucleon polarimeter function

TL;DR

The paper proposes integrating a nucleon polarimeter into a general-purpose spectrometer to access final-state proton polarization without compromising four-momentum measurements. It details a HIAF-based Hyperon–Nucleon Spectrometer (H-NS) with a carbon polarimeter target and MAPS/LGAD detectors, optimized by MC studies to achieve ~70% signal efficiency and strong background rejection. Polarization is extracted from the azimuthal distribution of proton–carbon elastic scattering, using the average analyzing power and a self-calibration strategy with polarized protons from hyperon decays to extend measurements to higher energies. This design provides a benchmark for future experiments and links final-state polarization to four-momentum data, enabling deeper insight into spin dynamics, with considerations for high-multiplicity environments.

Abstract

The spin polarization of hadrons is a key observable for probing the details of particle and nuclear interactions, offering information not available from other measurements. Currently, general-purpose spectrometers lack the capability to access final-state polarization. A novel technique to measure nucleon polarization within such a spectrometer has been proposed. Using this technique, a new design based on the proposed hyperon-nucleon spectrometer is developed. Systematic optimization confirms that the nucleon polarimeter functions effectively without impairing the detector's conventional performance. This successful integration, the first attempt of the general-purpose spectrometer, sets a valuable benchmark for future experiments. Ultimately, correlating spin polarization with four-momentum data will lead to a more profound understanding of the underlying physics.

Paper Structure

This paper contains 8 sections, 4 equations, 15 figures, 1 table.

Table of Contents

  1. Introduction
  2. General principle of nucleon polarimeter
  3. H-NS at HIAF
  4. Impact on the conventional detector performance
  5. Event selection
  6. Probability of $p\textrm{C}$ elastic scattering
  7. Polarization extraction
  8. Summary

Figures (15)

  • Figure 1: Illustration of proton polarization measurement with $pp$ or $p\textrm{C}$ elastic scattering.
  • Figure 2: Layout of the HIAF complex. H-NS is located in the high energy nuclear physcis terminal.
  • Figure 3: H-NS detector with proton polarimetry.
  • Figure 4: The material budget as a function of pseudorapidity for H-NS. The different colors show the contribution from the pixel sensor barrel (dark blue), pixel sensor disk (light blue), the LGAD detector (brown), and the carbon scattering layer (light green).
  • Figure 5: Momentum resolution at different carbon thickness.
  • ...and 10 more figures