| 1. |
- Beal, Jacob, et al.
(författare)
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Robust estimation of bacterial cell count from optical density
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 2. |
- Abele, H., et al.
(författare)
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Particle physics at the European Spallation Source
- 2023
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Ingår i: Physics reports. - : Elsevier. - 0370-1573 .- 1873-6270. ; 1023, s. 1-84
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Forskningsöversikt (refereegranskat)abstract
- Presently under construction in Lund, Sweden, the European Spallation Source (ESS) will be the world’s brightest neutron source. As such, it has the potential for a particle physics program with a unique reach and which is complementary to that available at other facilities. This paper describes proposed particle physics activities for the ESS. These encompass the exploitation of both the neutrons and neutrinos produced at the ESS for high precision (sensitivity) measurements (searches).
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| 3. |
- Addazi, A., et al.
(författare)
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New high-sensitivity searches for neutrons converting into antineutrons and/or sterile neutrons at the HIBEAM/NNBAR experiment at the European Spallation Source
- 2021
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Ingår i: Journal of Physics G. - : Institute of Physics Publishing (IOPP). - 0954-3899 .- 1361-6471. ; 48:7
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Tidskriftsartikel (refereegranskat)abstract
- The violation of baryon number, , is an essential ingredient for the preferential creation of matter over antimatter needed to account for the observed baryon asymmetry in the Universe. However, such a process has yet to be experimentally observed. The HIBEAM/NNBAR program is a proposed two-stage experiment at the European Spallation Source to search for baryon number violation. The program will include high-sensitivity searches for processes that violate baryon number by one or two units: free neutron–antineutron oscillation () via mixing, neutron–antineutron oscillation via regeneration from a sterile neutron state (), and neutron disappearance (n → n'); the effective process of neutron regeneration () is also possible. The program can be used to discover and characterize mixing in the neutron, antineutron and sterile neutron sectors. The experiment addresses topical open questions such as the origins of baryogenesis and the nature of dark matter, and is sensitive to scales of new physics substantially in excess of those available at colliders. A goal of the program is to open a discovery window to neutron conversion probabilities (sensitivities) by up to three orders of magnitude compared with previous searches. The opportunity to make such a leap in sensitivity tests should not be squandered. The experiment pulls together a diverse international team of physicists from the particle (collider and low energy) and nuclear physics communities, while also including specialists in neutronics and magnetics.
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| 4. |
- Backman, Filip, 1991-, et al.
(författare)
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The development of the NNBAR experiment
- 2022
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Ingår i: Journal of Instrumentation. - : Institute of Physics (IOP). - 1748-0221. ; 17:10
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Tidskriftsartikel (refereegranskat)abstract
- The NNBAR experiment for the European Spallation Source will search for free neutrons converting to antineutrons with a sensitivity improvement of three orders of magnitude compared to the last such search. This paper describes progress towards a conceptual design report for NNBAR. The design of a moderator, neutron reflector, beamline, shielding and annihilation detector is reported. The simulations used form part of a model which will be used for optimisation of the experiment design and quantification of its sensitivity.
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| 5. |
- Barrow, Joshua, et al.
(författare)
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Computing and Detector Simulation Framework for the HIBEAM/NNBAR Experimental Program at the ESS
- 2021
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Ingår i: 25<sup>th</sup> International Conference on Computing in High Energy and Nuclear Physics (CHEP 2021). - : EDP Sciences.
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Konferensbidrag (refereegranskat)abstract
- The HIBEAM/NNBAR program is a proposed two-stage experiment at the European Spallation Source focusing on searches for baryon number violation via processes in which neutrons convert to antineutrons. This paper outlines the computing and detector simulation framework for the HIBEAM/NNBAR program. The simulation is based on predictions of neutron flux and neutronics together with signal and background generation. A range of diverse simulation packages are incorporated, including Monte Carlo transport codes, neutron ray-tracing simulation packages, and detector simulation software. The common simulation package in which these elements are interfaced together is discussed. Data management plans and triggers are also described.
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| 6. |
- Dunne, Katherine, et al.
(författare)
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The HIBEAM/NNBAR Calorimeter Prototype
- 2022
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 2374:1
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Tidskriftsartikel (refereegranskat)abstract
- The HIBEAM/NNBAR experiment is a free-neutron search for n → sterile n and n → n¯ oscillations planned to be installed at the European Spallation Source under construction in Lund, Sweden. A key component in the experiment is the detector to identify n - n¯ annihilation events, which will produce on average four pions with a final state invariant mass of two nucleons, around 1.9 GeV. The beamline and experiment are shielded from magnetic fields which would suppress n → n¯ transitions, thus no momentum measurement will be possible. Additionally, calorimetry for particles with kinetic energies below 600 MeV is challenging, as traditional sampling calorimeters used in HEP would suffer from poor shower statistics. A design study is underway to use a novel approach of a hadronic range measurement in multiple plastic scintillator layers, followed by EM calorimetery with lead glass. A prototype calorimeter system is being built, and will eventually be installed at an ESS test beam line for in situ neutron background studies.
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| 7. |
- Gudkov, Vladimir, et al.
(författare)
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A Possible Neutron-Antineutron Oscillation Experiment at PF1B at the Institut Laue Langevin
- 2021
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Ingår i: Symmetry. - : MDPI AG. - 2073-8994. ; 13:12
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Tidskriftsartikel (refereegranskat)abstract
- We consider a possible neutron–antineutron (n−n¯) oscillation experiment at the PF1B instrument at Institut Laue Langevin. It can improve the best existing constraint on the transition rate and also allow the testing of the methods and instrumentation which would be needed for a later larger-scale experiment at ESS. The main gain factors over the most competitive experiment, performed earlier at PF1 instrument at ILL, are: a more intense neutron beam and a new operating mode based on coherent n and n¯ mirror reflections. The installation of such an experiment would need a temporary replacement of the existing ballistic neutron guide by a specially designed n/n¯ guide with a gradually increasing cross section and a specially selected coating as well as the development and construction of an advanced n¯ annihilation detector with a high efficiency and low background. The overall gain factor could reach up to an order of magnitude and depends on the chosen experiment configuration.
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| 8. |
- Wagner, R., et al.
(författare)
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Design of an optimized nested-mirror neutron reflector for a NNBAR experiment
- 2023
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 1051
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Tidskriftsartikel (refereegranskat)abstract
- The NNBAR experiment for the European Spallation Source will search for free neutrons converting to antineutrons with an expected sensitivity improvement of three orders of magnitude compared to the last such search. This paper describes both the simulations of a key component for the experiment, the neutron optical reflector and the expected gains in sensitivity.
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| 9. |
- Yiu, Sze-Chun
(författare)
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HIBEAM/NNBAR annihilation detectordevelopment
- 2024
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The observed matter-antimatter asymmetry in the universe implies a fundamental creation of matter overantimatter, a process linked to baryon number violation. Yet, experimental evidence for such a violationremains elusive. The HIBEAM/NNBAR programme, proposed at the European Spallation Source, seeksto probe baryon number violation through a comprehensive two-stage experiment. This includes investigatingneutron-antineutron oscillation, neutron-antineutron regeneration from a sterile state, and neutrondisappearance and regeneration. The program’s objective is to enhance the sensitivity of neutron conversionprobability measurements by up to three orders of magnitude beyond previous efforts, potentially unravellingkey mysteries in baryogenesis, dark matter, and new physics beyond the current collider research.This thesis focuses on the development of the design of the annihilation detector for the HIBEAM/NNBARprogramme, with a particular emphasis on the NNBAR annihilation detector. It investigates the multiplepionstate resulting from neutron-antineutron annihilations, which approximately release energy equivalentto two neutron masses. The detector’s design integrates various technologies, including a Time ProjectionChamber, plastic scintillators for hadronic range calorimetry, and lead glass for Electromagnetic calorimetry.A detailed GEANT4-based simulation study is conducted to analyze various event types, including annihilation,cosmic ray background, and neutron beam background. The study also involves examining the uniquesignatures these events leave in the detector and systematically refining the detector’s optimization.This thesis delves into the techniques of object reconstruction, which involves combining data from variouscomponents of the GEANT4-based detector simulation. The crucial task in this process is the identificationof these reconstructed objects. A detailed discussion and computation of event variables, derived from thedetector information, are presented. These variables are instrumental in differentiating between annihilationsignal events and cosmic ray background events. A preliminary event selection scheme is introduced,based on these variables, to differentiate between annihilation signal events and cosmic ray backgrounds.Preliminary results, with limited statistical data, indicate that this cut-based selection scheme can achieve approximately70% efficiency in signal acceptance while completely rejecting cosmic ray background.
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| 10. |
- Yiu, Sze-Chun, et al.
(författare)
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Status of the Design of an Annihilation Detector to Observe Neutron-Antineutron Conversions at the European Spallation Source
- 2022
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Ingår i: Symmetry. - : MDPI AG. - 2073-8994. ; 14:1
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Tidskriftsartikel (refereegranskat)abstract
- The goal of the HIBEAM/NNBAR program is to search for baryon number violation via the conversion or oscillation of neutrons into sterile neutrons and/or antineutrons at the European Spallation Source. A key experimental component of the program is the construction of an annihilation detector to directly observe the production of an antineutron following the oscillation. Design studies for the annihilation detector are presented. The predicted response of the detector models are studied using GEANT4 simulations made with Monte Carlo simulations of the annihilation signal topology and cosmic ray backgrounds. Particle identification and sensitive discriminating observables, such as invariant mass and sphericity, are shown.
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