# Missing-mass spectroscopy of the ${}^{12}{\rm C}(p,d)$ reaction near the $\eta^\prime$-meson production threshold

## TL;DR

This study used missing-mass spectroscopy to search for $ ext{η'}$-mesic states in $^{11}$C nuclei near the production threshold, setting upper limits on their formation cross sections and constraining the $ ext{η'}$-nucleus interaction.

## Contribution

First experimental search for $ ext{η'}$-mesic states in $^{11}$C using missing-mass spectroscopy near the production threshold.

## Key findings

- No clear signals of $ ext{η'}$-mesic states observed.
- Upper limits on formation cross sections established.
- Constraints on $ ext{η'}$-nucleus interaction derived.

## Abstract

Excitation-energy spectra of $^{11}$C nuclei near the $\eta^\prime$-meson production threshold have been measured by missing-mass spectroscopy using the $^{12}$C($p$,$d$) reaction. A carbon target has been irradiated with a 2.5 GeV proton beam supplied by the synchrotron SIS-18 at GSI to produce $\eta^\prime$ meson bound states in $^{11}$C nuclei. Deuterons emitted at $0^\circ$ in the reaction have been momentum-analyzed by the fragment separator (FRS) used as a high-resolution spectrometer. No distinct structure due to the formation of $\eta^\prime$-mesic states is observed although a high statistical sensitivity is achieved in the experimental spectra. Upper limits on the formation cross sections of $\eta^\prime$-mesic states are determined, and thereby a constraint imposed on the $\eta^\prime$-nucleus interaction is discussed.