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First of its kind, the barrel section of the MIP Timing Detector is a large area timing detector based on LYSO:Ce crystals and SiPMs which are required to operate in an unprecedentedly harsh radiation environment (up to an integrated fluence of \\(2\\times10^{14}\\) 1 MeV \\(n_{eq}/cm^2\\)). It is designed as a key element of the upgrade of the existing CMS detector to provide a time resolution for minimum ionizing particles in the range between 30-60 ps throughout the entire operation at the High Luminosity LHC. A thorough optimization of its components has led to the final detector module layout which exploits 25 \\(\\rm \\mu m\\) cell size SiPMs and 3.75 mm thick crystals. This design achieved the target performance in a series of test beam campaigns. In this paper we present test beam results which demonstrate the desired performance of detector modules in terms of radiation tolerance, time resolution and response uniformity.

The barrel section of the novel MIP Timing Detector (MTD) will be constructed as part of the upgrade of the CMS experiment to provide a time resolution for single charged tracks in the range of \\(30-60\\) ps using LYSO:Ce crystal arrays read out with Silicon Photomultipliers (SiPMs). A major challenge for the operation of such a detector is the extremely high radiation level, of about \\(2\\times10^{14}\\) 1 MeV(Si) Eqv. n/cm\\(^2\\), that will be integrated over a decade of operation of the High Luminosity Large Hadron Collider (HL-LHC). Silicon Photomultipliers exposed to this level of radiation have shown a strong increase in dark count rate and radiation damage effects that also impact their gain and photon detection efficiency. For this reason during operations the whole detector is cooled down to about \\(-35^{\\circ}\\)C. In this paper we illustrate an innovative and cost-effective solution to mitigate the impact of radiation damage on the timing performance of the detector, by integrating small thermo-electric coolers (TECs) on the back of the SiPM package. This additional feature, fully integrated as part of the SiPM array, enables a further decrease in operating temperature down to about \\(-45^{\\circ}\\)C. This leads to a reduction by a factor of about two in the dark count rate without requiring additional power budget, since the power required by the TEC is almost entirely offset by a decrease in the power required for the SiPM operation due to leakage current. In addition, the operation of the TECs with reversed polarity during technical stops of the accelerator can raise the temperature of the SiPMs up to \\(60^{\\circ}\\)C (about \\(50^{\\circ}\\)C higher than the rest of the detector), thus accelerating the annealing of radiation damage effects and partly recovering the SiPM performance.

Cerium-doped Lutetium-Yttrium Oxyorthosilicate (LYSO:Ce)is one of the most widely used Cerium-doped Lutetium based scintillation crystals. Initially developed for medical detectors it rapidly became attractive for High Energy Particle Physics (HEP) applications, especially in the frame of high luminosity particle colliders. In this paper, a comprehensive and systematic study of LYSO:Ce (\\([Lu_{(1-x)}Y_x]_2SiO_5\\):\\(Ce\\)) crystals is presented. It involves for the first time a large number of crystal samples (180) of the same size from a dozen of producers.The study consists of a comparative characterization of LYSO:Ce crystal products available on the market by mechanical, optical and scintillation measurements and aims specifically, to investigate key parameters of timing applications for HEP.

We report on the separation of Cherenkov and scintillation light in BGO and BSO crystals read out with silicon photomultipliers (SiPMs). The two light components are disentangled on an event-by-event basis by combining optical filtering with waveform template fitting, exploiting their distinct spectral and temporal characteristics. Measurements were carried out using high-energy muon and positron beams at the CERN SPS North Area, demonstrating Cherenkov yields of up to \\(\\)150 ph.e./GeV in electromagnetic showers. This work provides the first demonstration of Cherenkov-scintillation separation in BGO and BSO crystals with SiPM readout, supporting the use of this technology as a building block for a dual-readout electromagnetic calorimeter, as foreseen in the IDEA detector concept for a future \\(e^+e^-\\) Higgs factory.

For the High-Luminosity (HL-LHC) phase, the upgrade of the Compact Muon Solenoid (CMS) experiment at CERN will include a novel MIP Timing Detector (MTD). The central part of MTD, the barrel timing layer (BTL), is designed to provide a measurement of the time of arrival of charged particles with a precision of 30 ps at the beginning of HL-LHC, progressively degrading to 60 ps while operating in an extremely harsh radiation environment for over a decade. In this paper we present a comparative analysis of the time resolution of BTL module prototypes made of LYSO:Ce crystal bars read out by silicon photo-multipliers (SiPMs). The timing performance measured in beam test campaigns is presented for prototypes with different construction and operation parameters, such as different SiPM cell sizes (15, 20, 25 and 30 \\( m\\)), SiPM manufacturers and crystal bar thicknesses. The evolution of time resolution as a function of the irradiation level has been studied using non-irradiated SiPMs as well as SiPMs exposed up to \\(2 10^14~n_eq/cm^2\\) fluence. The key parameters defining the module time resolution such as SiPM characteristics (gain, photon detection efficiency, radiation induced dark count rate) and crystal properties (light output and dimensions) are discussed. These results have informed the final choice of the MTD barrel sensor configuration and offer a unique starting point for the design of future large-area scintillator-based timing detectors in either low or high radiation environments.

The CMS detector will be upgraded for the HL-LHC to include a MIP Timing Detector (MTD). The MTD will consist of barrel and endcap timing layers, BTL and ETL respectively, providing precision timing of charged particles. The BTL sensors are based on LYSO:Ce scintillation crystals coupled to SiPMs with TOFHIR2 ASICs for the front-end readout. A resolution of 30-60 ps for MIP signals at a rate of 2.5 Mhit/s per channel is expected along the HL-LHC lifetime. We present an overview of the TOFHIR2 requirements and design, simulation results and measurements with TOFHIR2 ASICs. The measurements of TOFHIR2 associated to sensor modules were performed in different test setups using internal test pulses or blue and UV laser pulses emulating the signals expected in the experiment. The measurements show a time resolution of 24 ps initially during Beginning of Operation (BoO) and 58 ps at End of Operation (EoO) conditions, matching well the BTL requirements. We also showed that the time resolution is stable up to the highest expected MIP rate. Extensive radiation tests were performed, both with x-rays and heavy ions, showing that TOFHIR2 is not affected by the radiation environment during the experiment lifetime.

In this White Paper for the 2021 Snowmass process, we discuss aspects of precision timing within electromagnetic and hadronic calorimeter systems for high-energy physics collider experiments. Areas of applications include particle identification, event and object reconstruction, and pileup mitigation. Two different system options are considered, namely cell-level timing capabilities covering the full detector volume, and dedicated timing layers integrated in calorimeter systems. A selection of technologies for the different approaches is also discussed.

Until about a decade ago, laser-induced ionization was considered instantaneous. Since then, applications of attosecond laser pulses have shown multiple subtle and complex factors that influence the precise timing of electron ejection from atoms and surfaces. Vos et al. measured the corresponding attosecond dynamics of dissociative photoionization in a diatomic molecule, carbon monoxide. By imaging the charged fragments, the timing could be correlated with the specific spatial portion of the molecule from which the electron wave packet emerged. Science , this issue p. 1326 The precise timing of ionization in CO varies with respect to the portion of the molecule from which the electron emerges. Attosecond metrology of atoms has accessed the time scale of the most fundamental processes in quantum mechanics. Transferring the time-resolved photoelectric effect from atoms to molecules considerably increases experimental and theoretical challenges. Here we show that orientation- and energy-resolved measurements characterize the molecular stereo Wigner time delay. This observable provides direct information on the localization of the excited electron wave packet within the molecular potential. Furthermore, we demonstrate that photoelectrons resulting from the dissociative ionization process of the CO molecule are preferentially emitted from the carbon end for dissociative 2 Σ states and from the center and oxygen end for the 2 Π states of the molecular ion. Supported by comprehensive theoretical calculations, this work constitutes a complete spatially and temporally resolved reconstruction of the molecular photoelectric effect.

The interaction of an extreme-ultraviolet attosecond pulse with a molecular system suddenly removes electrons, which can lead to significant changes in the chemical bonding and hence to rearrangements of the residual molecular cation. The timescales of the electronic and nuclear dynamics are usually very different, thus supporting separate treatment. However, when light nuclei are involved, as in most organic and biological molecules containing atomic hydrogen, the correlation between electronic and nuclear motion cannot be ignored. Using an advanced attosecond pump–probe spectroscopic method, we show that the coupling between electronic and nuclear motion in H2 leaves a clear trace in the phase of the entangled electron–nuclear wave packet. This requires us to re-evaluate the physical meaning of the measured phase, which depends on the energy distribution between electrons and nuclei. The conclusions are supported by ab initio calculations that explicitly account for the coupling between electronic and nuclear dynamics.

During and after the 9/11 rescue and recovery efforts, World Trade Center (WTC) responders were exposed to environmental hazards that may accelerate aging and increase frailty. This study examines the relationship between polypharmacy and frailty among WTC responders to inform strategies that mitigate medication-related risks in high-risk, aging populations. We included WTC responders aged 50 and older who attended at least one clinical monitoring visit at WTC Health Program between 2017-2019. Frailty was assessed using the WTC-specific Clinical Frailty Index, and associations with polypharmacy (concurrent use of 5 or more medications) and fall-risk increasing drugs (FRIDs) use were evaluated through multivariable logistic regression models adjusting for demographic, employment, health, and WTC exposure data. Among 6,966 WTC responders, 55% met the criteria for polypharmacy and 7.6% used FRIDs. Frailty was independently associated with both polypharmacy (OR 1.15, p < 0.001) and FRID use (OR 1.11, p < 0.001). Older age (OR 1.08, p < 0.001), obesity (OR 1.92, p < 0.001 for BMI ≥ 30), protective service occupations (OR 1.30, p = 0.002), and chronic conditions such as gastroesophageal reflux disease (OR 1.71, p < 0.001), obstructive airway disease (OR 2.24, p < 0.001), and upper respiratory disease (OR 1.85, p < 0.001) were associated with higher odds of polypharmacy. In contrast, male sex (OR 0.81, p = 0.018) and construction occupations (OR 0.73, p = 0.001) were associated with lower odds of polypharmacy. Female sex (OR 1.64, p < 0.001), smoking (current: OR 1.55, p = 0.013; former: OR 1.30, p = 0.014), and mental health conditions such as anxiety (OR 1.66, p = 0.004), depression (OR 2.85, p < 0.001), and post-traumatic stress disorder (OR 1.72, p < 0.001) were associated with higher odds of FRID use. We found a high prevalence of polypharmacy and FRID use among aging WTC responders, with frailty significantly associated with both. Our findings underscore the need to optimize medication management for aging WTC responders, which may impact their healthy aging.