Nearly all mass gathering events worldwide were banned at the beginning of the COVID-19 pandemic, as they were suspected of presenting a considerable risk for the transmission of SARS-CoV-2. We ...investigated the risk of transmitting SARS-CoV-2 by droplets and aerosols during an experimental indoor mass gathering event under three different hygiene practices, and used the data in a simulation study to estimate the resulting burden of disease under conditions of controlled epidemics. Our results show that the mean number of measured direct contacts per visitor was nine persons and this can be reduced substantially by appropriate hygiene practices. A comparison of two versions of ventilation with different air exchange rates and different airflows found that the system which performed worst allowed a ten-fold increase in the number of individuals exposed to infectious aerosols. The overall burden of infections resulting from indoor mass gatherings depends largely on the quality of the ventilation system and the hygiene practices. Presuming an effective ventilation system, indoor mass gathering events with suitable hygiene practices have a very small, if any, effect on epidemic spread.
Abstract
The long-term prospect of building a hadron collider around the circumference of a great circle of the Moon is sketched. A circular collider on the Moon (CCM) of ∼11 000 km in circumference ...could reach a proton–proton center-of-mass collision energy of 14 PeV—a thousand times higher than the Large Hadron Collider at CERN—optimistically assuming a dipole magnetic field of 20 T. Several aspects of such a project are presented, including siting, construction, availability of necessary materials on the Moon, and powering, as well as a discussion of future studies and further information needed to determine the more concrete feasibility of each. Machine parameters and vacuum requirements are explored, and an injection scheme is delineated. Other unknowns are set down. Due to the strong interest from multiple organizations in establishing a permanent Moon presence, a CCM could be the (next-to-) next-to-next-generation discovery machine for high-energy particle physics and a natural successor to next-generation machines, such as the proposed future circular collider at CERN or a super proton–proton collider in China, and other future machines, such as a collider in the Sea, in the Gulf of Mexico. A CCM would serve as an important stepping stone toward a Planck-scale collider sited in our Solar System.
Towards future circular colliders Benedikt, Michael; Zimmermann, Frank
Journal of the Korean Physical Society,
09/2016, Letnik:
69, Številka:
6
Journal Article
Recenzirano
Odprti dostop
The Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN) presently provides proton-proton collisions at a center-of-mass (c.m.) energy of 13 TeV. The LHC design was ...started more than 30 years ago, and its physics program will extend through the second half of the 2030’s. The global Future Circular Collider (FCC) study is now preparing for a post-LHC project. The FCC study focuses on the design of a 100-TeV hadron collider (FCC-hh) in a new ∼100 km tunnel. It also includes the design of a high-luminosity electron-positron collider (FCCee) as a potential intermediate step, and a lepton-hadron collider option (FCC-he). The scope of the FCC study comprises accelerators, technology, infrastructure, detectors, physics, concepts for worldwide data services, international governance models, and implementation scenarios. Among the FCC core technologies figure 16-T dipole magnets, based on Nb
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superconductor, for the FCC-hh hadron collider, and a highly-efficient superconducting radiofrequency system for the FCC-ee lepton collider. Following the FCC concept, the Institute of High Energy Physics (IHEP) in Beijing has initiated a parallel design study for an
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Higgs factory in China (CEPC), which is to be succeeded by a high-energy hadron collider (SPPC). At present a tunnel circumference of 54 km and a hadron collider c.m. energy of about 70 TeV are being considered. After a brief look at the LHC, this article reports the motivation and the present status of the FCC study, some of the primary design challenges and R&D subjects, as well as the emerging global collaboration.
Accelerators in the 21st Century Zimmermann, Frank
EPJ Web of Conferences,
01/2018, Letnik:
182
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
More than 30,000 accelerators are in operation worldwide. Of these less than 1% are devoted to basic research. Prominent among the latter are high-energy particle colliders - powerful engines of ...discovery and precision measurement, which have played an essential role in establishing the standard model of particle physics. Technological innovation has allowed building colliders for ever higher energy and better performance, at decreasing specific cost. New concepts will allow reaching even higher luminosities and energies throughout the coming century. One cost-effective strategy for future collider implementation is staging. For example, a future circular collider could first provide electron-positron collisions, then hadron collisions (proton-proton and heavy-ion), and, finally, the collision of muons. Indeed, cooling-free muon colliders, realizable in a number of ways, promise an attractive and energy-efficient path towards lepton collisions at tens of TeV. While plasma accelerators and dielectric accelerators offer unprecedented gradients, the construction of a high-energy collider based on these advanced technologies still faces a number of challenges. Pushing the accelerating gradients or bending fields ever further, the breakdown of the QED vacuum may, or may not, set an ultimate limit to electromagnetic acceleration.
Health care workers are at increased risk for mental health issues due to high psychological and physical job demands. According to a recent study, stress beliefs (i.e., believing stress to be ...detrimental to one's health) might influence physicians' mental health in response to a naturalistic stressor (COVID‐19 hospital working conditions). Due to a small sample size and high alpha error inflation, the suggested association needs to be interpreted with caution. The current study aims to replicate those findings in a larger sample. A cross‐sectional survey among N = 418 (64.1% female; Median age = 30–39 years) physicians and nurses of a large German medical centre was conducted during the COVID‐19 pandemic (May/June 2021). Perception of pandemic related increase of work stress was assessed via self‐report. Stress beliefs were assessed with the Beliefs About Stress Scale, and mental health symptoms were assessed with the 21‐item Depression Anxiety Stress Scale. Stress beliefs moderated the association between increased work stress and mental health symptoms. Increased work stress was associated with increased depressive, anxiety and distress symptoms only in health care workers with medium (simple slope = 2.22, p < .001; simple slope = 1.27, p < .001; simple slope = 3.19, p < .001) and high (simple slope = 3.13; p < .001; simple slope = 1.66, p < .05; simple slope = 4.33, p < .001) negative stress beliefs. Among health care workers with low negative stress beliefs increased work stress was not associated with increased depressive, anxiety and distress symptoms. This confirms negative stress beliefs as variable of interest in research on the impact of stress on mental health in health care workers.
The integrated luminosity, a key figure of merit for any particle-physics collider, is closely linked to the peak luminosity and to the beam lifetime. The instantaneous peak luminosity of a collider ...is constrained by a number of boundary conditions, such as the available beam current, the maximum beam-beam tune shift with acceptable beam stability and reasonable luminosity lifetime (i.e., the empirical “beam-beam limit”), or the event pileup in the physics detectors. The beam lifetime at high-luminosity hadron colliders is largely determined by particle burn off in the collisions. In future highest-energy circular colliders synchrotron radiation provides a natural damping mechanism, which can be exploited for maximizing the integrated luminosity. In this article, we derive analytical expressions describing the optimized integrated luminosity, the corresponding optimum store length, and the time evolution of relevant beam parameters, without or with radiation damping, while respecting a fixed maximum value for the total beam-beam tune shift or for the event pileup in the detector. Our results are illustrated by examples for the proton-proton luminosity of the existing Large Hadron Collider (LHC) at its design parameters, of the High-Luminosity Large Hadron Collider (HL-LHC), and of the Future Circular Collider (FCC-hh).
Future colliders for particle physics—“Big and small” Zimmermann, Frank
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2018, Letnik:
909
Journal Article
Recenzirano
Odprti dostop
Discoveries at high-energy particle colliders have established the standard model of particle physics. Technological innovation has helped to increase the collider energy at a much faster pace than ...the corresponding costs. New concepts will allow reaching ever higher luminosities and energies throughout the coming century. Cost-effective strategies for the collider implementation include staging. For example, a future circular collider could first provide electron–positron collisions, then hadron collisions (proton–proton and heavy-ion), and finally the collision of muons. Cooling-free muon colliders, realizable in a number of ways, promise an attractive and energy-efficient path towards lepton collisions at tens of TeV. While plasma accelerators and dielectric accelerators offer unprecedented gradients, the construction of a high-energy collider based on these new technologies still calls for significant improvements in cost and performance. Pushing the accelerating gradients or bending fields ever further, the breakdown of the QED vacuum may set an ultimate limit to electromagnetic acceleration. Finally, some ideas are sketched for reaching, or exceeding, the Planck energy.
•Particle accelerators, especially colliders, are outstanding engines of discovery.•Technology advances enabled higher energy and performance at lower cost.•One cost-effective strategy for future collider implementation is staging.•Cooling-free muon colliders offer an attractive path towards tens of TeV.•QED vacuum breakdown and Planck energy may, or may not, be ultimate limits.
The Future Circular Collider (FCC) Integrated Project foresees, in a first stage, a high-luminosity high-energy electron-positron collider, serving as Higgs, top and electroweak factory, and, in a ...second stage, an energy frontier hadron collider, with a centre-of-mass energy of at least 100 TeV. This programme well matches the highest priority future requests issued by the 2020 Update of the European Strategy for Particle Physics. In 2021, with the support of the CERN Council, a five-year FCC Feasibility Study was launched. In this article, we present the FCC integrated project and the preparations for the FCC Feasibility Study.
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