Explore the vast range of titles available.

January 10, 3:30-4:15 PM EST Distinguished Lecturer Sally C. Seidel is a faculty member of the University of New Mexico's Collider Physics Group, whose primary goal is an improved understanding of heavy quark bound states.

Saunders interviews Sally C. Seidel, faculty member of the University of New Mexico's Collider Physics Group about her research focuses on improving the understanding of heavy quark bound states, which in turn can help to elucidate the strong force, one of the four fundamental forces of nature. Seidel said the fundamental particles, as far as people know, are typically pointlike objects. They might have mass, but sometimes they don't have any physical dimension. The particles that are like protons are physically extended and when they collide them in colliders like the Large Hadron Collider, they can determine that they actually have structure. She added the purpose of a particle collider is to collect a lot of energy at a very small point, and they do that by colliding two particles that are carrying a lot of energy.

We measured the radiation tolerance of commercially available diamonds grown by the Chemical Vapor Deposition process by measuring the charge created by a 120 GeV hadron beam in a 50 μm pitch strip detector fabricated on each diamond sample before and after irradiation. We irradiated one group of samples with 70 MeV protons, a second group of samples with fast reactor neutrons (defined as energy greater than 0.1 MeV), and a third group of samples with 200 MeV pions, in steps, to (8.8±0.9) × 1015 protons/cm2, (1.43 ± 0.14) × 1016 neutrons/cm2, and (6.5 ± 1.4) × 1014 pions/cm2, respectively. By observing the charge induced due to the separation of electron–hole pairs created by the passage of the hadron beam through each sample, on an event-by-event basis, as a function of irradiation fluence, we conclude all datasets can be described by a first-order damage equation and independently calculate the damage constant for 70 MeV protons, fast reactor neutrons, and 200 MeV pions. We find the damage constant for diamond irradiated with 70 MeV protons to be 1.62 ± 0.07(stat) ± 0.16(syst) × 10–18 cm2/(p μm), the damage constant for diamond irradiated with fast reactor neutrons to be 2.65 ± 0.13(stat) ± 0.18(syst) × 10–18 cm2/(n μm), and the damage constant for diamond irradiated with 200 MeV pions to be 2.0 ± 0.2(stat) ± 0.5(syst) × 10–18 cm2/(π μm). The damage constants from this measurement were analyzed together with our previously published 24 GeV proton irradiation and 800 MeV proton irradiation damage constant data to derive the first comprehensive set of relative damage constants for Chemical Vapor Deposition diamond. We find 70 MeV protons are 2.60 ± 0.29 times more damaging than 24 GeV protons, fast reactor neutrons are 4.3 ± 0.4 times more damaging than 24 GeV protons, and 200 MeV pions are 3.2 ± 0.8 more damaging than 24 GeV protons. We also observe the measured data can be described by a universal damage curve for all proton, neutron, and pion irradiations we performed of Chemical Vapor Deposition diamond. Finally, we confirm the spatial uniformity of the collected charge increases with fluence for polycrystalline Chemical Vapor Deposition diamond, and this effect can also be described by a universal curve.

Silicon detection is a mature technology for registering the passage of charged particles. At the same time it continues to evolve toward increasing radiation tolerance as well as precision and adaptability. For these reasons it is likely to remain a critical element of detection systems associated with extra-terrestrial exploration. Silicon sensor leakage current and depletion voltage depend upon the integrated fluence received by the sensor, and upon its thermal history during and after the irradiation process. For minimal assumptions on shielding and hence on particle energy spectrum, and using published data on Martian ground temperature, we predict the leakage current density and the depletion voltage, as a function of time, of silicon sensors deployed continuously on the Mars surface for a duration of up to 28 Earth-years, for several sensor geometries and a worst-case temperature scenario.

Low gain avalanche detectors (LGADs) deliver excellent timing resolution, which can mitigate mis-assignment of vertices associated with pileup at the High Luminosity LHC and other future hadron colliders. The most highly irradiated LGADs will be subject to \\(2.5 \\times10^{15} \\mathrm{n}_\\mathrm{eq} \\mathrm{cm}^{-2}\\) of hadronic fluence during HL-LHC operation; their performance must tolerate this. Hamamatsu Photonics K.K. and Fondazione Bruno Kessler LGADs have been irradiated with 400 and 500 MeV protons respectively in several steps up to \\(1.5 \\times10^{15} \\mathrm{n}_\\mathrm{eq} \\mathrm{cm}^{-2}\\). Measurements of the acceptor removal constants of the gain layers, evolution of the timing resolution and charge collection with damage, and inter-channel isolation characteristics, for a variety of design options, are presented here.

Characterization measurements of \\(25~\\mathrm{\\mu m} \\times 25~\\mathrm{\\mu m}\\) pitch 3D silicon sensors are performed, for devices with active thickness of \\(150~\\mu\\)m. Evidence of charge multiplication caused by impact ionization below the breakdown voltage is observed in sensors operated at \\(-45~^\\circ\\mathrm{C}\\). Small-pitch 3D silicon sensors have potential as high precision 4D tracking detectors that are also able to withstand radiation fluences beyond \\(10^{16}\\)~n\\(_{\\rm eq}/\\)cm\\(^2\\). This is applicable for use at future facilities such as the High-Luminosity Large Hadron Collider and the Future Circular Collider. Characteristics of these devices are compared to those of similar sensors of pitch \\(50~\\mathrm{\\mu m}\\times 50~\\mathrm{\\mu m}\\), showing comparable charge collection at low voltage, and acceptable leakage current, depletion voltage, breakdown voltage, and capacitance despite the extremely small cell size. The unirradiated \\(25~\\mathrm{\\mu m} \\times 25~\\mathrm{\\mu m}\\) sensors exhibit charge multiplication above about 90 V reverse bias, while, as predicted, no multiplication is observed in the \\(50~\\mathrm{\\mu m} \\times 50~\\mathrm{\\mu m}\\) sensors below their breakdown voltage. The maximum gain observed below breakdown is 1.33.

This is the report from the 2023 Particle Physics Project Prioritization Panel (P5) approved by High Energy Physics Advisory Panel (HEPAP) on December 8, 2023. The final version was made public on May 8, 2024 and submitted to DOE SC and NSF MPS.

Motivated by the need for fast timing detectors to withstand up to 2 MGy of ionizing dose at the High Luminosity Large Hadron Collider, prototype low gain avalanche detectors (LGADs) have been fabricated in single pad configuration, 2x2 arrays, and related p-i-n diodes, and exposed to Co- 60 sources for study. Devices were fabricated with a range of dopant layer concentrations and, for the arrays, a variety of inter-pad distances and distances from the active area to the edge. Measurements of capacitance versus voltage and leakage current versus voltage have been made to compare pre- and post-irradiation characteristics in gain layer depletion voltage, full bulk depletion voltage, and breakdown voltage. Conclusions are drawn regarding the effects of the gammas both on surface and interface states and on their contribution to acceptor removal through non-ionizing energy loss from Compton electrons or photoelectrons. Comparison of the performances of members of the set of devices can be used to optimize gain layer parameters.

The resistivity of polycrystalline chemical vapor deposition diamond sensors is studied in samples exposed to fluences relevant to the environment of the High Luminosity Large Hadron Collider. We measure the leakage current for a range of bias voltages on samples irradiated with 800 MeV protons up to 1.6\\times 10^{16} p/cm^2. The proton beam at LANSCE, Los Alamos National Laboratory, was applied to irradiate the samples. The devices' resistivity is extracted for temperatures in the -10^\\circC to +20^\\circC range.

Results are presented from four CDF analyses involving heavy quark production in proton-antiproton collisions at center of mass energy 1.96 TeV. The shapes of b-jets are found to be broader than inclusive predictions and broader than both PYTHIA and HERWIG defaults. A measurement of the production cross section for psi(2S) is consistent with Run 1 results and with theoretical predictions associated with parton distribution function energy dependence. The inclusive b-jet production cross section is also consistent with theoretical predictions over six orders of magnitude. The b-bbar differential production cross section is compared to several theoretical models and found to be best described by MC@NLO + JIMMY.