Ryan Heller

The detector ARGUS has been designed as a universal tool to investigate final states from e+e− annihilation processes in the energy range of the ϒ resonances. ARGUS started operation in October 1982 and has since successfully taken data at the ϒ(1S), ϒ(2S) and ϒ(4S) energies, and in the nearby continuum. The detector combines excellent charged particle identification and good photon energy resolution over more than 90% of the full solid angle. A particle originating from the interaction vertex and leaving the beam tube traverses the following components: the vertex drift chamber, the main drift chamber which determines its momentum and specific ionization, the time-of-flight system through which its velocity is determined, and the electromagnetic calorimeter. Muons pass through the magnet coils and the flux return yoke and finally hit the muon chamber system which surrounds the detector. The momentum resolution of ARGUS is σ(pT)PT = (0.012 + (0.009pT[GeV/c])2)12, the photon energy resolution in the barrel shower counters is σ(E)E = (0.0722+0.0652E[GeV])12. Combining the information from all p devices, more than 80% of all charged hadrons can be recognized unambiguously. The electron-hadron and muon-hadron rejection rates are 1:200 and 1:50 respectively.

This paper presents the principles of operation of Resistive AC-Coupled Silicon Detectors (RSDs) and measurements of the temporal and spatial resolutions using a combined analysis of laser and beam test data. RSDs are a new type of n-in-p silicon sensor based on the Low-Gain Avalanche Diode (LGAD) technology, where the n+ implant has been designed to be resistive, and the read-out is obtained via AC-coupling. The truly innovative feature of RSD is that the signal generated by an impinging particle is shared isotropically among multiple read-out pads without the need for floating electrodes or an external magnetic field. Careful tuning of the coupling oxide thickness and the n+ doping profile is at the basis of the successful functioning of this device. Several RSD matrices with different pad width-pitch geometries have been extensively tested with a laser setup in the Laboratory for Innovative Silicon Sensors in Torino, while a smaller set of devices have been tested at the Fermilab Test Beam Facility with a 120 GeV/c proton beam. The measured spatial resolution ranges between 2.5μm for 70–100 pad-pitch geometry and 17μm with 200–500 matrices, a factor of 10 better than what is achievable in binary read-out (binsize∕12). Beam test data show a temporal resolution of ∼40ps for 200 μm pitch devices, in line with the best performances of LGAD sensors at the same gain.

In order to extend the tracking acceptance, to improve the primary and secondary vertex reconstruction and thus enhancing the tagging capabilities for short lived particles, the ZEUS experiment at the HERA Collider at DESY installed a silicon strip vertex detector. The barrel part of the detector is a 63 cm long cylinder with silicon sensors arranged around an elliptical beampipe. The forward part consists of four circular shaped disks. In total just over 200k channels are read out using 2.9m2 of silicon. In this report a detailed overview of the design and construction of the detector is given and the performance of the completed system is reviewed.

The reaction e+e− → ϒ′ → ϒπ+π−, with ϒ → anything, has been measured using the ARGUS detector at DORIS . We obtain a mass difference M(ϒ′) − M(ϒ) = (562 ± 3) MeV and a decay branching ratio BR(ϒ′→ϒπ+π−)=(17.9±0.9±2.1)%. The invariant mass spectrum of the π+π− system differs from phase space, but is well described by a matrix element of the form (Mππ2−λMπ2) with λ=2.6±0.5. We also report preliminary results on the exclusive decay ϒ′ → ϒπ+π−, with ϒ → e+e−, and obtain BR(ϒ → e+e−) = (2.8 ± 0.4 ± 04±0.3)%.

We report on a search for elementary particles with charges much smaller than the electron charge using a data sample of proton-proton collisions provided by the CERN Large Hadron Collider in 2018, corresponding to an integrated luminosity of 37.5 fb$^{-1}$ at a center-of-mass energy of 13 TeV. A prototype scintillator-based detector is deployed to conduct the first search at a hadron collider sensitive to particles with charges ${\leq}0.1e$. The existence of new particles with masses between 20 and 4700 MeV is excluded at 95% confidence level for charges between $0.006e$ and $0.3e$, depending on their mass. New sensitivity is achieved for masses larger than $700$ MeV.

We report on the expected sensitivity of dedicated scintillator-based detectors at the LHC for elementary particles with charges much smaller than the electron charge. The dataset provided by a prototype scintillator-based detector is used to characterize the performance of the detector and provide an accurate background projection. Detector designs, including a novel slab detector configuration, are considered for the data taking period of the LHC to start in 2022 (Run 3) and for the high luminosity LHC. With the Run 3 dataset, the existence of new particles with masses between 10 MeV and 45 GeV could be excluded at 95% confidence level for charges between 0.003 e and 0.3 e, depending on their mass. With the high luminosity LHC dataset, the expected limits would reach between 10 MeV and 80 GeV for charges between 0.0018 e and 0.3 e, depending on their mass.Received 14 April 2021Accepted 12 July 2021DOI:https://doi.org/10.1103/PhysRevD.104.032002Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasHypothetical particle physics modelsParticle dark matterTechniquesScintillatorsGeneral PhysicsParticles & Fields

The development of detectors that provide high resolution in four dimensions has attracted wide-spread interest in the scientific community for several applications in high-energy physics, nuclear physics, medical imaging, mass spectroscopy as well as quantum information. In addition to high time resolution and thanks to the AC-coupling of the electrodes, LGAD silicon sensors can provide high resolution in the measurement of spatial coordinates of an incident minimum ionizing particle. Such AC-coupled LGADs, also known as AC-LGADs, are therefore considered as candidates for future detectors to provide 4-dimensional measurements in a single sensing device with 100$\%$ fill factor. This article presents the first characterization of an AC-LGAD sensor with a proton beam of 120 GeV momentum at Fermilab. The sensor consists of strips with 80 $\mu$m width, fabricated at Brookhaven National Laboratory. The signal properties, efficiency, spatial, and time resolution are presented. The experimental results show that the time resolution of such an AC-LGAD is compatible to standard LGADs with similar gain, and that AC-LGADs can be segmented with fine pitches as standard strip or pixel detectors.

Abstract We present measurements of AC-LGADs performed at the Fermilab's test beam facility using 120 GeV protons. We studied the performance of various strip and pad AC-LGAD sensors that were produced by BNL and HPK. The measurements are performed with our upgraded test beam setup that utilizes a high precision telescope tracker, and a simultaneous readout of up to 7 channels per sensor, which allows detailed studies of signal sharing characteristics. These measurements allow us to assess the differences in designs between different manufacturers, and optimize them based on experimental performance. We then study several reconstruction algorithms to optimize position and time resolutions that utilize the signal sharing properties of each sensor. We present a world's first demonstration of silicon sensors in a test beam that simultaneously achieve better than 6–10 μm position and 30 ps time resolution. This represents a substantial improvement to the spatial resolution than would be obtained with binary readout of sensors with similar pitch.

Using the ARGUS detector at DORIS we have observed the prediction of the charged D∗ meson in e+e− annihilation at a center of mass energy of 10 GeV. The D∗ fragmentation function has been measured using the decay channels D∗+ → D0π+ and D0 → K−π+ and K−π+π+π−. We find σ·Br for the channels D0 → K−π+ and D0 → K−π+π+π− to be (23.6 ± 2.2 ± 4.7) pb and (51.0 ± 4.6 ± 15.5) pb respectively, and the ratio of branching ratios Br(D0 → K−π+π+π−)/Br(D0 → K−π+) = 2.17 ± 0.28 ± 0.23. In addition we measure the mass difference M(D∗+) − M(D0) to be (145.46 ± 0.07 ± 0.03) MeV, and set an upper limit for D0 − D̄0 mixing of 0.11.

The e+e−-storage ring DORIS II provides polarized beams with polarizations up to 80% in the energy range of the ϒ′ meson. The method of resonance depolarization allows the average beam energy to be determined to a precision of ±0.1 MeV. An energy scan of the hadronic cross section over the resonance range with the detectors ARGUS and Crystal Ball determines the ϒ′ mass to be (10023.1 ± 0.4) MeV.

The impact of the ARGUS experiment to elementary particle physics is reviewed. More than ten years of data taking has allowed ARGUS to contribute significantly to our understanding of beauty and charmed hadrons, τ Leptons, ϒ mesons, ϒϒ interactions and fragmentation processes. In particular the ARGUS measurements of CKM matrix elements opened up a new window on the Standard Model.

AC-LGADs, also referred to as resistive silicon detectors, are a recent development of low-gain avalanche detectors (LGADs), based on a sensor design where the multiplication layer and n+ contact are continuous, and only the metal layer is patterned. In AC-LGADs, the signal is capacitively coupled from the continuous, resistive n+ layer over a dielectric to the metal electrodes. Therefore, the spatial resolution is not only influenced by the electrode pitch, but also the relative size of the metal electrodes. Signal propagation between the metallized areas and charge sharing between electrodes plays a larger role in these detectors than in conventional silicon sensors read out in DC mode. AC-LGADs from two manufacturers were studied in beam tests and with infrared laser scans. The impact of n+ layer resistivity and metal electrode pitch on the charge sharing and achievable position resolution is shown. For strips with 100 μm pitch, a resolution of ¡ 5 μm can be reached. The charge sharing between neighboring strips is investigated in more detail, indicating the induction of signal charge and subsequent re-sharing over the n+ layer. Furthermore, an approach to identify signal sharing over large distances is presented.

Abstract We present the first beam test results with centimeter-scale AC-LGAD strip sensors, using the Fermilab Test Beam Facility and sensors manufactured by the Brookhaven National Laboratory. Sensors of this type are envisioned for applications that require large-area precision 4D tracking coverage with economical channel counts, including timing layers for the Electron Ion Collider (EIC), and space-based particle experiments. A survey of sensor designs is presented, with the aim of optimizing the electrode geometry for spatial resolution and timing performance. Several design considerations are discussed towards maintaining desirable signal characteristics with increasingly larger electrodes. The resolutions obtained with several prototypes are presented, reaching simultaneous 18 μm and 32 ps resolutions from strips of 1 cm length and 500 μm pitch. With only slight modifications, these sensors would be ideal candidates for a 4D timing layer at the EIC.

We describe the two gamma detectors built for the European Hybrid Spectrometer (EHS). Their monitoring system is presented in detail. Results from tests and the performance obtained during the first EHS experiment are given.

Using the ARGUS detector at DORIS, we have observed the production of F± mesons in e+e− annihilation at a centre of mass energy of 10 GeV through their subsequent decays into φπ± and φπ+π−π±. The values obtained for [R(e+e−→FX). Branching Ratio] are (1.47 ± 0.32 ± 0.20)% and (1.63 ± 0.42 ± 0.41)% respectively. The observed mass is (1973.6 ± 2.6 ± 3.0)MeVc2. The F momentum spectrum is as expected for the fragmentation of c quarks into charmed mesons, but is somewhat softer than for fragmentation into D∗ mesons. The relevant angular distributions are consistent with a spin-zero assignment of the F meson.

The time-of-flight system of the ARGUS detector at the DORIS e+e− storage ring consists of 64 barrel scintillation counters covering 75% of 4π, and 2 × 48 end cap counters, covering 17% of 4π. The barrel counters are viewed by two phototubes each, while the end cap counters have one tube only. The time-of-flight system serves as a part of the fast trigger and identifies charged particles. The time resolution achieved during the first year of ARGUS operation is 210 ps for Bhabhas (which are used for the off-line monitoring of the system), and 220 ps for hadrons, both in barrel and end cap counters. This converts into a three standard deviation mass separation up to 700 MeV/c between pions and kaons and 1200 MeV/c between kaons and protons. Electrons can be separated from heavier particles up to 230 MeV/c.

The upgrades of the CMS and ATLAS experiments for the high luminosity phase of the Large Hadron Collider will employ precision timing detectors based on Low Gain Avalanche Detectors (LGADs). We present a suite of results combining measurements from the Fermilab Test Beam Facility, a beta source telescope, and a probe station, allowing full characterization of the HPK type 3.1 production of LGAD prototypes developed for these detectors. We demonstrate that the LGAD response to high energy test beam particles is accurately reproduced with a beta source. We further establish that probe station measurements of the gain implant accurately predict the particle response and operating parameters of each sensor, and conclude that the uniformity of the gain implant in this production is sufficient to produce full-sized sensors for the ATLAS and CMS timing detectors.

Using the ARGUS detector at DORIS we have obtained evidence for a resonance which decays into an F meson and a photon. The observed mass is 2109 ± 9 ± 7 MeV, which is 144 ± 9 ± 7 MeV greater than the F meson mass. Its properties are consistent with those of the F∗ meson with JP = 1−.

We present the design and performance characterization results of the novel Fermilab Constant Fraction Discriminator ASIC (FCFD) developed to readout low gain avalanche detector (LGAD) signals by directly using a constant fraction discriminator (CFD) to measure signal arrival time. Silicon detectors with time resolutions less than 30 ps will play a critical role in future collider experiments, and LGADs have been demonstrated to provide the required time resolution and radiation tolerance for many such applications. The FCFD has a specially designed discriminator that is robust against amplitude variations of the signal from the LGAD that normally requires an additional correction step when using a traditional leading edge discriminator. The application of the CFD directly in the ASIC promises to be more reliable and reduces the complication of evolving time-walk corrections throughout the operational lifetime of the detector system. We will present a summary of the measured performance of the FCFD for input signals generated by internal charge injection, LGAD signals from an infrared laser, and LGAD signals from minimum-ionizing particles. The mean time response for LGAD signals with charge ranging between 5 and 26 fC has been measured to vary no more than 10 ps, orders of magnitude more stable than an uncorrected leading edge discriminator based measurement, and effectively removes the need for any additional time-walk correction. The measured contribution to the time resolution from the FCFD ASIC is found to be 10 ps for signals with charge above 20 fC.

The 1760 shower counter modules of the detector ARGUS at DORIS II are monitored by a laser as the central light source. A lead glass counter, which also detects cosmic muons, and a photodiode serve as reference systems. The paper describes the technical layout, performance and stability of the monitoring system. Algorithms and corrections applied in the calibration procedure are discussed in detail. The monitoring system serves also to control the time-of-flight counter performance and to calibrate their TDCs.

We have investigated the ϒ→γττ using tagged ϒ mesons from the decay ϒ'→π+π−ϒ. The photon spectrum exhibits no monochromatic line corresponding to a narrow object decaying into a τ pair and is fully compatible with the expected background contributions. The branching ratio Br(ϒ→τ+τ− is determined to be (3.07±0.46±0.22)%.

A search has been made for particles with charge Q = 13, Q = 23 and Q = 43 produced in e+e− annihilation using the ARGUS detector at the e+e− storage ring DORIS, operating at a centre of mass energy around 10 GeV. No candidate events were found in 84.5 pb−1 of collected data. Upper limits are established for the cross section for the production of fractionally charged particles with masses up to 4 GeVc2, improving on previously obtained limits.

The planned luminosity increase at the Large Hadron Collider in the coming years has triggered interest in the use of the particles' time of arrival as additional information in specialized detectors to mitigate the impact of pile-up. The required time resolution is of the order of tens of picoseconds, with a spatial granularity of the order of 1 mm. A time measurement at this precision level will also be of interest beyond the LHC and beyond high energy particle physics. We present in this paper the first developments towards a radiation hard Depleted Monolithic Active Pixel Sensor (DMAPS), with high-resolution time measurement capability. The technology chosen is a standard high voltage CMOS process, in conjunction with a high resistivity detector material, which has already proven to efficiently detect particles in tracking applications after several hundred of Mrad of irradiation.

The production of antideuterons has been observed in electron-positron annihilations at center-of-mass energies around 10 GeV. Antideuterons have been identified unambiguously by their energy loss in the drift chamber, their time-of-flight and the pattern of their energy deposition in the shower counters of the ARGUS detector. The production rate in the momentum range (0.6−1.8) GeV/c is (1.6−0.7+1.0) × 10−5 per hadronic event.

The MIP Timing Detector will provide additional timing capabilities for detection of minimum ionizing particles (MIPs) at CMS during the High Luminosity LHC era, improving event reconstruction and pileup rejection. The central portion of the detector, the Barrel Timing Layer (BTL), will be instrumented with LYSO:Ce crystals and Silicon Photomultipliers (SiPMs) providing a time resolution of about 30 ps at the beginning of operation, and degrading to 50-60 ps at the end of the detector lifetime as a result of radiation damage. In this work, we present the results obtained using a 120 GeV proton beam at the Fermilab Test Beam Facility to measure the time resolution of unirradiated sensors. A proof-of-concept of the sensor layout proposed for the barrel region of the MTD, consisting of elongated crystal bars with dimensions of about 3 x 3 x 57 mm$^3$ and with double-ended SiPM readout, is demonstrated. This design provides a robust time measurement independent of the impact point of the MIP along the crystal bar. We tested LYSO:Ce bars of different thickness (2, 3, 4 mm) with a geometry close to the reference design and coupled to SiPMs manufactured by Hamamatsu and Fondazione Bruno Kessler. The various aspects influencing the timing performance such as the crystal thickness, properties of the SiPMs (e.g. photon detection efficiency), and impact angle of the MIP are studied. A time resolution of about 28 ps is measured for MIPs crossing a 3 mm thick crystal bar, corresponding to an MPV energy deposition of 2.6 MeV, and of 22 ps for the 4.2 MeV MPV energy deposition expected in the BTL, matching the detector performance target for unirradiated devices.

We present the design and measurements of a proton detection system built using a single photon counting hybrid pixel array detector. The system uses the UFXC detector designed for operating with very high photon fluxes. We demonstrate, that with appropriately modified data acquisition firmware, the UFXC detector is capable of operating in the frame-triggered zero dead-time mode, which captures every frame containing desired information, at a rate of up to 50 kfps. The detector consists of a 128 x 256 matrix of square-shaped pixels with a pitch of 75 μm, which makes it suitable for particle tracking applications in test beam environments. We estimate the position resolution achieved with a single layer of the UFXC detector to be around 40 μm.

We present the design and performance characterization results of the novel Fermilab Constant Fraction Discriminator ASIC (FCFD) developed to readout low gain avalanche detector (LGAD) signals by directly using a constant fraction discriminator (CFD) to measure signal arrival time. Silicon detectors with time resolutions less than 30 ps will play a critical role in future collider experiments, and LGADs have been demonstrated to provide the required time resolution and radiation tolerance for many such applications. The FCFD has a specially designed discriminator that is robust against amplitude variations of the signal from the LGAD that normally requires an additional correction step when using a traditional leading edge discriminator based measurement. The application of the CFD directly in the ASIC promises to be more reliable and reduces the complication of timing detectors during their operation. We will present a summary of the measured performance of the FCFD for input signals generated by internal charge injection, LGAD signals from an infrared laser, and LGAD signals from minimum-ionizing particles. The mean time response for a wide range of LGAD signal amplitudes has been measured to vary no more than 15 ps, orders of magnitude more stable than an uncorrected leading edge discriminator based measurement, and effectively removes the need for any additional time-walk correction. The measured contribution to the time resolution from the FCFD ASIC is also found to be 10 ps for signals with charge above 20 fC.

We present the results of studies aimed at developing 4D tracking technology for a wide range of physics experiments, including the Electron Ion Collider (EIC) and future Lepton Colliders. The studies focused on evaluating the performance of centimeter-scale AC-LGAD (AC-Low Gain Avalanche Detector) sensors and a new ASIC (Application-Specific Integrated Circuit) called the Fermilab Constant Fraction Discriminator (FCFD). For the AC-LGADs, we present the resolutions obtained with several prototypes, which reach simultaneous resolutions of 18 microns and 32 ps from strips of 1 cm length and 500 micron pitch. Regarding the FCFD, the mean time response for a wide range of signal amplitudes has been measured to be no more than 15 ps. This is orders of magnitude more precise than an uncorrected leading-edge discriminator-based measurement and effectively eliminates the need for a signal amplitude-based correction. Furthermore, the measured contribution to the time resolution from the FCFD ASIC is found to be 10 ps for signals with charges above 20 fC.

Utilizing recent advances in image recognition, we explore the possibilities of applying deep learning to to the challenging problem of tritium detection and quantification using thick, fully depleted, highly-pixelated, scientific Charge Coupled Devices (CCDs.) We present a simulation framework developed to study signals from both tritium decay products and background radiation. Simulated particle tracks are used to train a Convolutional Neural Network (CNN) to perform track-based particle identification. The importance of thin CCD dead layers are discussed, as 50% of tritium decay particles don't penetrate deeper than 50 nm in silicon.

Deathbed Insomnia, and: Tamarack Cameo Rich Heller (bio) Deathbed Insomnia When I can't sleepI often think with gratitudeof the dead great auntsand uncles who were kindand generous to me and of the living auntsand uncles who still are,though in smaller waysnow that I am middle-aged. When they too are dead,where will the kindnessand generosity for thischildless fool be found? I will continue to givethanks even if I am allalone with deathbedinsomnia because thoseadults who owed this child nothing gave him everythinghe needed to make it to thispoint. In utter abandonment, a child will either be takenin or die. Either way she—for the rest of her life—will toss and turn like a lostopossum baby in an oldrobin's nest waitingfor her mother's return. [End Page 41] Tamarack Cameo Veins of brushed silvershoot through the bluestonesky and smudge tamarackcitrine and maple copperupon the onyx beaver pond edged with antique-finishfrosted dawn grasses. No polished crystalor gemstone, no brilliantcut diamond in a cathedralsetting embellished with accent stones could demand sucha price—the price of our attention rapt as the sun risesand smelts this oreof hoarfrostinto precious dew—alchemy of the ordinary. [End Page 42] Rich Heller rich heller lives on Squirrel Hill above Monongahela River in Pittsburgh. He writes poems and songs (YouTube channel @richheller). Rich also makes and plays wooden flutes and propagates plants indigenous to the Allegheny Plateau. Creating healthy habitat for rich biodiversity—and human diversity—is his major preoccupation. Copyright © 2023 University of North Dakota

Low-Gain Avalanche Diodes (LGADs) are silicon sensors developed for the fast detection of minimum ionizing particles (mips). Characterized by an internal moderate gain that enhances the signal amplitude and built on thin silicon substrates of a few tens of microns, they exhibit excellent timing performance. However, to achieve a spatially uniform multiplication a large pixel pitch is needed, preventing a fine spatial resolution. To overcome this limitation and to create a 4D detector which can simultaneously provide good time and spatial resolution, a few options are under study at Brookhaven National Laboratory in collaboration with national and international partners and abroad. The AC-coupled LGAD approach is one of them, where metal electrodes are placed over an insulator at a fine pitch, and signals are capacitively induced on these electrodes. To enhance the radiation hardness, the gain layer can be buried under a few microns of high-resistivity epitaxial layer. In another device (the Deep-Junction LGAD), both an n and p layers are buried by an epitaxial layer or by a wafer-to-wafer bonding, while standard-implanted electrodes are patterned at the top of the device. The fabrication technology must be tailored for the specific LGAD family, and a fine tuning of a few process parameters needs to be carefully studied before being applied to the silicon wafers being fabricated in clean-room. Also, for the detection of low-penetrating particles, a new structure must be used where, in particular, the sign of the implants is switched. The structure, characteristics, TCAD simulations and laboratory tests carried on during the development of these devices will be presented.

Results are reported from two searches for supersymmetric particles in final states with multiple jets, including several b-tagged jets, with and without large missing transverse momentum.The data sample corresponds to 2.3 fb -1 (2.7 fb -1 without missing transverse momentum) of pp collisions recorded by the CMS experiment at √ s = 13 TeV.The searches focus on processes with massive, high multiplicity final states, such as gluino pair production with the gluino decaying to top quarks and a neutralino, and gluino pair production with R-parity violating gluino decay to top, bottom and strange quarks.Both searches use the quantity M J , the sum of the masses of the large-radius jets, to discriminate between signal and background, establish control regions for other discriminating variables, and as a central piece of the background estimation.The observed event yields are consistent with the standard model expectations, and the results are interpreted in terms of limits on simplified supersymmetric models.Gluinos with mass less than 1600 GeV are excluded for models with g → t t χ 0 1 and light neutralinos, and gluinos with mass less than 1360 GeV are excluded for the decay g → tbs.

We report on the design, simulation and test of Low Gain Avalanche Diodes (LGADs) which utilize a buried gain layer. The buried layer is formed by patterned implantation of a 50-micron thick float zone substrate wafer-bonded to a low resistivity carrier. This is then followed by epitaxial deposition of a ≈ 3 micron-thick high resistivity amplification region. The topside is then processed with junction edge termination and guard ring structures and incorporates an AC-coupled cathode implant. This design allows for independent adjustment of gain layer depth and density, increasing design flexibility. A higher gain layer dopant density can also be achieved by controlling the process thermal budget, improving radiation hardness. A first set of demonstration devices has been fabricated, including a variety of test structures. We report on TCAD design and simulation, fabrication process flow, and preliminary measurements of prototype devices.

4-dimensional (4D) trackers with ultra fast timing (10-30 ps) and very fine spatial resolution (O(few $\mu$m)) represent a new avenue in the development of silicon trackers, enabling new physics capabilities beyond the reach of the existing tracking detectors. This paper reviews the impact of integrating 4D tracking capabilities on several physics benchmarks both in potential upgrades of the HL-LHC experiments and in several detectors at future colliders, and summarizes the currently available sensor technologies as well as electronics, along with their limitations and directions for R$\&$D.

We present the first beam test results with centimeter-scale AC-LGAD strip sensors, using the Fermilab Test Beam Facility and sensors manufactured by the Brookhaven National Laboratory. Sensors of this type are envisioned for applications that require large-area precision 4D tracking coverage with economical channel counts, including timing layers for the Electron Ion Collider (EIC), and space-based particle experiments. A survey of sensor designs is presented, with the aim of optimizing the electrode geometry for spatial resolution and timing performance. Several design considerations are discussed towards maintaining desirable signal characteristics with increasingly larger electrodes. The resolutions obtained with several prototypes are presented, reaching simultaneous 18 micron and 32 ps resolutions from strips of 1 cm length and 500 micron pitch. With only slight modifications, these sensors would be ideal candidates for a 4D timing layer at the EIC.

Author(s): Heller, Ryan Edward | Advisor(s): Stuart, David | Abstract: The discovery of the Higgs boson casts new urgency to an old question: the Higgs mass hierarchy problem. Supersymmetry can provide an elegant and natural solution to the hierarchy problem, and would result in many new particles accessible at the TeV scale probed by the LHC.This dissertation describes a search for a classic natural supersymmetry signature, gluino mediated top squark production. The search is performed in the single-lepton final state, relying on the large missing energy and high jet and b-flavor jet multiplicities to separate the gluino signal from the Standard Model backgrounds. The background measurement is centered around the variable MJ, the sum of masses of large radius jets. The search uses a sample of proton-proton collisions at center of mass energy 13 TeV recorded by the CMS detector, corresponding to an integrated luminosity of 35.9 /fb. The observed yields in the signal regions are consistent with the expected Standard Model backgrounds, and the results are interpreted in the context of simplified models of gluino pair production. Scenarios with gluino masses up to approximately 1.9 TeV are excluded at 95% confidence level for neutralino masses less than 1 TeV. This negative result joins a substantial body of evidence disfavoring supersymmetry realized near the electroweak scale.

The upgrades of the CMS and ATLAS experiments for the high luminosity phase of the Large Hadron Collider will employ precision timing detectors based on Low Gain Avalanche Detectors (LGADs). We present a suite of results combining measurements from the Fermilab Test Beam Facility, a beta source telescope, and a probe station, allowing full characterization of the HPK type 3.1 production of LGAD prototypes developed for these detectors. We demonstrate that the LGAD response to high energy test beam particles is accurately reproduced with a beta source. We further establish that probe station measurements of the gain implant accurately predict the particle response and operating parameters of each sensor, and conclude that the uniformity of the gain implant in this production is sufficient to produce full-sized sensors for the ATLAS and CMS timing detectors.