Experimental particle physics seeks to understand the universe by probing its fundamental particles and forces and exploring how they govern the large-scale processes that shape cosmic evolution. This whitepaper presents a vision for how Artificial Intelligence (AI) can accelerate discovery in this field. We outline grand challenges that must be addressed to enable transformative breakthroughs and describe how current and planned experimental facilities can implement this vision to advance our understanding of the vast and complex physical world from the smallest to the largest scales. We show how facilities currently under construction, such as the HL-LHC, DUNE and soon EIC, can both benefit from and serve as proving grounds for this vision, while also enabling a longer-term goal for how future experiments – like FCC-ee at CERN, IceCube-Gen2, a Muon Collider in the U.S., and smaller to mid-scale projects – can be fully AI-native. We describe how a truly national-scale collaboration, jointly managed across large funding partners, and involving both DOE laboratories and universities, can make this happen.

Resistive Plate Chambers (RPCs) are essential active media of large-scale experiments as part of the muon systems and (semi-)digital hadron calorimeters. Among the several outstanding issues associated with the RPCs, the loss of efficiency for the detection of particles when subjected to high particle fluxes, and the limitations associated with the common RPC gases can be listed. In order to address the latter issue, we developed novel RPC designs with special anode plates coated with high secondary electron emission yield materials such as Al$_2$O$_3$ and TiO$_2$. The proof of principle was obtained for various designs and is in progress for the rest. The idea was initiated following the achievements on the development of the novel 1-glass RPCs. Here we report on the construction of various different RPC designs, and their performance measurements in laboratory tests and with particle beams; and discuss the future test plans.

The majority of future large-scale neutrino and dark matter experiments are based on liquid argon detectors. Since liquid argon is also a very effective scintillator, these experiments also have light detection systems. The liquid argon scintillation wavelength of 127 nm is most commonly shifted to the visible range by special wavelength shifters or read out by the 127 nm sensitive photodetectors that are under development. The effective calibration and quality control of these active media is still a persisting problem. In order to respond to this need, we developed an argon light source which is based on plasma generation and light transfer across a MgF2 window. The light source was designed as a small, portable and easy-to-operate device to enable the acquisition of performance characteristics of several square meters of light detectors. Here, we report on the development of the light source and its performance characteristics.

The radiation damage in optical materials mostly manifests itself as the loss of optical transmission. The optical materials recover from radiation damage to some extent in the presence of natural light, and at a faster rate in the presence of stimulating light. On the other hand, the systematic study of the dynamics of the recovery as a function of the stimulating light parameters such as its wavelength, intensity and exposure duration and method has not been performed in detail. We established an LED recovery station which provides pulsed and continuous light at various wavelengths at custom geometries. The study starts with the irradiation of optical samples at various gamma doses at a rate of 87.5 Gy/min. The optical transmittance of the samples are then measured in 200 nm - 1500 nm range for an extended period of time. Here we report on the details of the irradiation and recovery setups, and the results of recovery from radiation damage under different light exposure mechanisms.

Resistive Plate Chambers (RPCs) are a key active media of the muon systems of current and future collider experiments as well as the CALICE (semi-)digital hadron calorimeter. The outstanding issues with RPCs can be listed as the loss of efficiency for the detection of particles when subjected to high particle fluxes and the limitations associated with the common RPC gases. We developed novel RPC designs with: low resistivity glass plates; a single resistive plate; and a single resistive plate and a special anode plate coated with high secondary electron emission yield material. The cosmic and beam tests confirmed the viability of these new approaches for calorimetric applications. The chambers also have improved single-particle response, such as a pad multiplicity close to unity. Here, we report on the construction of various different glass RPC designs and their performance measurements in laboratory tests and with particle beams. We also discuss future test plans, which include the long-term performance tests of the newly developed RPCs, investigation of minimal gas flow chambers, and feasibility study for the large-size chambers.

The International Linear Collider (ILC) is on the table now as a new global energy-frontier accelerator laboratory taking data in the 2030s. The ILC addresses key questions for our current understanding of particle physics. It is based on a proven accelerator technology. Its experiments will challenge the Standard Model of particle physics and will provide a new window to look beyond it. This document brings the story of the ILC up to date, emphasizing its strong physics motivation, its readiness for construction, and the opportunity it presents to the US and the global particle physics community.

Future circular and linear colliders including FCC, as well as the Large Hadron Collider in the High-Luminosity era have been imposing unprecedented challenges on the radiation hardness of particle detectors that will be used for specific purposes e.g. forward calorimeters, beam and luminosity monitors. We performed research on the radiation-hard active media for such detectors, particularly calorimeters, by exploring intrinsically radiation-hard materials and their mixtures. The initial samples that we probed were thin plates of Polyethylene Naphthalate (PEN) and Polyethylene Terephthalate (PET) and thin sheets of HEM. The previous studies indicate towards promising performance under high radiation conditions. We report on the necessary process of mixing PEN and PET for optimized scintillation and signal timing properties preserving the high radiation resistance. Recently we developed a new plastic scintillator material, tested it in particle beams and obtained promising results. In recent studies, we investigated the radiation damage to plastic scintillators, various special glasses and scintillating fibers together with their recovery mechanisms. Here we report on the development of radiation-hard scintillators and the irradiation studies together with the investigation of the recovery mechanisms.

The radiation damage in the optical active media of collider detectors and beamline instrumentation is an outstanding problem. The exposed doses reach unprecedented levels in some current and projected implementations. In order to mitigate this, the development of optical materials with higher radiation resistance is underway. On the other hand, there is a significant lack of in-situ radiation damage recovery systems, whereas such systems have the potential to increase the useful lifetime of the optical materials considerably. Although it is well-known that stimulating the recovery of radiation damage with LED illumination significantly improves the recovery rate and the ultimate damage, a systematic study of the recovery e.g. as a function of the incident LED light spectra, intensity and exposure duration has not been performed. Here we attempt to do this study and present our first results of recovery from radiation damage under different recovery conditions.

We report the scintillation decay constants of polyethylene naphthalate (PEN) and polyethylene terephthalate (PET) determined by excitation of the plastic substrate with an accelerated beam of protons and resulting light yield measured as a function of time with a photomultiplier attached to an oscilloscope. The decay constant of PEN was found to be 35 ns and PET 7 ns.

We report the preliminary results from repeated irradiations of optical scintillating fibers exposed to gamma radiation. Optical fibers degrade in radiation fields, but exhibit some recovery once removed. Study of repeated irradiations are difficult to find in the literature. We find that a UV-blue optical wavelength shifting fiber exhibits permanent degradation, the recovery is incomplete, and an interesting two step damage process that appears to affect which wavelengths are darkened at different rates.

The timing characteristics of scintillators must be understood in order to determine which applications they are appropriate for. Polyethylene naphthalate (PEN) and polyethylene teraphthalate (PET) are common plastics with uncommon scintillation properties. Here, we report the timing characteristics of PEN and PET, determined by exciting them with 120 GeV protons. The test beam was provided by Fermi National Accelerator Laboratory, and the scintillators were tested at the Fermilab Test Beam Facility. PEN and PET are found to have dominant decay constants of 34.91 ns and 6.78 ns, respectively.

We report preliminary results from in situ monitoring of an optical scintillating fiber while being exposed to a cesium-173 gamma radiatior. We measured the degradation of fiber transmittance across the visible spectrum as a function of time. We observed that the region below 500 nm was degraded quickly and thoroughly while wavelengths above 500 nm lost clarity more slowly.

Modern particle physics experiments have unprecedented needs for radiation tolerant components. Particle detectors broadly use scintillators to generate optical signals in proportion to the energy of passing particles. Radiation damages a scintillator, producing color centers which absorb and attenuate light within the scintillator, reducing its performance. There is currently a major effort underway to develop new radiation tolerant scintillators and readout strategies for modern experiments. One strategy is to take advantage of the natural recovery of a moderately damaged scintillator. We investigate whether being exposed to bright light can enhance the recovery of a glass intended to be used as a substrate for producing new glass-based scintillators. We find that UV-LED exposure (365 nm) is the most effective and efficient way to induce optical recovery of the glass cubes produced by AFO Research. White-light exposure only helped recovery in the green-infrared region of the electromagnetic spectrum. UV light exposure induced recovery in the entirety of the cubes transmission spectrum. We also find that UV-A light (365 nm) is effective at speeding up the recovery of plastic scintillating fibers. UV-LED mediated recovery techniques are a possible solution to speed up radiation damage recovery in detectors. A UV-LED calibration system inside a detector could be turned on between experiment runs in order to help the scintillating materials recover their optical properties and, at the same time, allow the detector to calibrate itself, extending the useful life of existing scintillators.

With the discovery of non-zero value of $\theta_{13}$ mixing angle, the next generation of long-baseline neutrino (LBN) experiments offers the possibility of obtaining statistically significant samples of muon and electron neutrinos and anti-neutrinos with large oscillation effects. In this document we intend to highlight the importance of Near Detector facilities in LBN experiments to both constrain the systematic uncertainties affecting oscillation analyses but also to perform, thanks to their close location, measurements of broad benefit for LBN physics goals. A strong European contribution to these efforts is possible.

A search is presented for the production of a pair of Higgs bosons, where one decays into two photons and the other one into a bottom quark-antiquark pair. The analysis is performed using proton-proton collision data at root s = 13 TeV recorded in 2016 by the CMS detector at the LHC, corresponding to an integrated luminosity of 35.9 fb(-1) . The results are in agreement with standard model (SM) predictions. In a search for resonant production, upper limits are set on the cross section for new spin-0 or spin-2 particles. For the SM-like nonresonant production hypothesis, the data exclude a product of cross section and branching fraction larger than 2.0 fb at 95% confidence level (CL), corresponding to about 24 times the SM prediction. Values of the effective Higgs boson self-coupling K X are constrained to be within the range -11 < K-lambda < 17 at 95% CL, assuming all other Higgs boson couplings are at their SM value. The constraints on K-lambda, are the most restrictive to date. (C) 2018 The Author(s). Published by Elsevier B.V.

The Particle Flow Algorithms attempt to measure each particle in a hadronic jet individually, using the detector providing the best energy/momentum resolution. Therefore, the spatial segmentation of the calorimeter plays a crucial role. In this context, the CALICE Collaboration developed the Digital Hadron Calorimeter. The Digital Hadron Calorimeter uses Resistive Plate Chambers as active media and has a 1-bit resolution (digital) readout of 1 × 1 cm2 pads. The calorimeter was tested with steel and tungsten absorber structures, as well as with no absorber structure, at the Fermilab and CERN test beam facilities over several years. In addition to conventional calorimetric measurements, the Digital Hadron Calorimeter offers detailed measurements of event shapes, rigorous tests of simulation models and various tools for improved performance due to its very high spatial granularity. Here we report on the results from the analysis of pion and positron events. Results of comparisons with the Monte Carlo simulations are also discussed. The analysis demonstrates the unique utilization of detailed event topologies.