METNet: A combined pTmiss working point using a neural network with the ATLAS detector
ATLAS-PHYS-PUB-2021-025, July 2021
Abstract:
In order to suppress pile-up effects and improve the resolution, ATLAS employs a suite of working points for missing transverse momentum (pTmiss) reconstruction, and each is optimal for different event topologies and different beam conditions. A neural network (NN) can exploit various event properties to combine complementary information from each of the working points on an event-by-event basis. The resulting regressed pTmiss (`METNet') offers improved resolution and pile-up resilience across a number of different topologies compared to the current pTmiss working points. Additionally, by using the NN's confidence in its predictions, a machine learning-based pTmiss significance (`METNetSig') can be defined. This note presents simulation-based studies of the behaviour and performance of METNet and METNetSig for several topologies compared to current ATLAS pTmiss reconstruction methods.
Measuring the electric dipole moment of the neutron: The cryoEDM experiment
Proceedings of Science EPS-HEP 2009 376
Abstract:
The cryoEDM experiment at the Institut Laue-Langevin in Grenoble will measure the electric dipole moment (EDM) of the neutron with unparalleled precision. A neutron EDM arises due to CP violation. The cryoEDM experiment is sensitive to levels of CP violation predicted by many “beyond the standard model” theories and the result will therefore constrain or support these theories. The current limit to the neutron EDM stands at d_n<2.9x 10^-26 e cm as measured with a room temperature experiment. By operating in superfluid helium below 0.9 K and collecting high densities of ultra cold neutrons, the cryoEDM experiment will improve on the existing limit or measure an EDM. High precision magnetometry is essential to reduce the systematic errors in the cryoEDM experiment originating from changes in the magnetic environment. We present the cryoEDM apparatus and technologies.Precision measurements of the standard model; PDFs, pile-up and production of W+jets at 13 TEV with the ATLAS detector
Abstract:
The question of the nature of the universe at its most fundamental level is one which has been with humankind since ancient times. The development of the theoretical basis of the Standard Model of elementary particles during the 20th century, and its subsequent experimental validation, is a triumph of modern physics. However, the Standard Model is known to be incomplete, and, in the Large Hadron Collider era at the high-energy and high-intensity frontier, our understanding and modelling of the Standard Model has increasingly become limiting for searches for physics beyond it. In this thesis, a measurement performed using 36.2 fb−1 of integrated luminosity recorded by the ATLAS experiment during Large Hadron Collider Run 2 of a crucial benchmark process for Standard Model modelling is presented; W boson production in association with jets. This is the first such measurement in the W → μν decay channel at √s =13 TeV. Differential cross-sections, in observables sensitive to the modelling of quantum chromodynamics, are presented for both charge-independent and charge-separated W production, and compared to two cutting-edge calculations evolved to next-to-next-to-leading order in quantum chromodynamics. In addition, this process strongly constrains fits of the Parton Distribution Functions of the proton; an analysis of the structure of the proton using several previous ATLAS measurements, including W boson production in association with jets at √s=8 TeV, will also be presented.
Proper motions of the satellites of M31
Monthly Notices of the Royal Astronomical Society, Volume 488, Issue 3, September 2019, Pages 3231–3237
Abstract:
We predict the range of proper motions of 19 satellite galaxies of M31 that would rotationally stabilize the M31 plane of satellites consisting of 15–20 members as identified by Ibata et al. Our prediction is based purely on the current positions and line-of-sight velocities of these satellites and the assumption that the plane is not a transient feature. These predictions are therefore independent of the current debate about the formation history of this plane. We further comment on the feasibility of measuring these proper motions with future observations by the THEIA satellite mission as well as the currently planned observations by HST and JWST.
Search for new phenomena in final states with large jet multiplicities and missing transverse momentum using sqrt s = 7 TeV pp collisions with the ATLAS detector
The Journal of High Energy Physics 2011:11