hep-ex updates on arXiv.org


The Forward Physics Facility: Sites, Experiments, and Physics Potential. (arXiv:2109.10905v1 [hep-ph])

The Forward Physics Facility (FPF) is a proposal to create a cavern with the space and infrastructure to support a suite of far-forward experiments at the Large Hadron Collider during the High Luminosity era. Located along the beam collision axis and shielded from the interaction point by at least 100 m of concrete and rock, the FPF will house experiments that will detect particles outside the acceptance of the existing large LHC experiments and will observe rare and exotic processes in an extremely low-background environment. In this work, we summarize the current status of plans for the FPF, including recent progress in civil engineering in identifying promising sites for the FPF and the experiments currently envisioned to realize the FPF's physics potential. We then review the many Standard Model and new physics topics that will be advanced by the FPF, including searches for long-lived particles, probes of dark matter and dark sectors, high-statistics studies of TeV neutrinos of all three flavors, aspects of perturbative and non-perturbative QCD, and high-energy astroparticle physics.

Measurement of Charge and Light Yields for $^{127}$Xe L-Shell Electron Captures in Liquid Xenon. (arXiv:2109.11487v1 [physics.ins-det])

Dark matter searches using dual-phase xenon time-projection chambers (LXe-TPCs) rely on their ability to reject background electron recoils (ERs) while searching for signal-like nuclear recoils (NRs). ER response is typically calibrated using $\beta$-decay sources, such as tritium, but these calibrations do not characterize events accompanied by an atomic vacancy, as in solar neutrino scatters off inner shell electrons. Such events lead to emission of X-rays and Auger electrons, resulting in higher electron-ion recombination and thus a more NR-like response than inferred from $\beta$-decay calibration. We present a cross-calibration of tritium $\beta$-decays and $^{127}$Xe electron-capture decays (which produce inner-shell vacancies) in a small-scale LXe-TPC and give the most precise measurements to date of light and charge yields for the $^{127}$Xe L-shell electron-capture in liquid xenon. We observe a 6.9$\sigma$ (9.2$\sigma$) discrepancy in the L-shell capture response relative to tritium $\beta$-decays, measured at a drift field of 363 $\pm$ 14 V/cm (258 $\pm$ 13 V/cm), when compared to simulations tuned to reproduce the correct $\beta$-decay response. In dark matter searches, use of a background model that neglects this effect leads to overcoverage (higher limits) for background-only multi-kiloton-year exposures, but at a level much less than the 1-$\sigma$ experiment-to-experiment variation of the 90\% C.L. upper limit on the interaction rate of a 50 GeV/$c^2$ dark matter particle.

Design, construction and operation of the ProtoDUNE-SP Liquid Argon TPC. (arXiv:2108.01902v3 [physics.ins-det] UPDATED)

The ProtoDUNE-SP detector is a single-phase liquid argon time projection chamber (LArTPC) that was constructed and operated in the CERN North Area at the end of the H4 beamline. This detector is a prototype for the first far detector module of the Deep Underground Neutrino Experiment (DUNE), which will be constructed at the Sandford Underground Research Facility (SURF) in Lead, South Dakota, USA. The ProtoDUNE-SP detector incorporates full-size components as designed for DUNE and has an active volume of $7\times 6\times 7.2$~m$^3$. The H4 beam delivers incident particles with well-measured momenta and high-purity particle identification. ProtoDUNE-SP's successful operation between 2018 and 2020 demonstrates the effectiveness of the single-phase far detector design. This paper describes the design, construction, assembly and operation of the detector components.