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ILC Vertex Tracker R&D

Office of Scientific and Technical Information (OSTI)

Authors:

Marco Battaglia, Jean-Marie Bussat, Devis Contarato, Peter Denes, Lindsay Glesener, Leo Greiner, Benjamin Hooberman, Derek Shuman, Lauren Tompkins, Chinh Vu, Dario Bisello, Piero Giubilato, Devis Pantano, Marco Costa, Alessandro La Rosa, Gino Bolla, Daniela Bortoletto, Isaac Children
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Jet mass and substructure of inclusive jets in sqrt(s) = 7 TeV pp collisions with the ATLAS experiment

Abstract:

Recent studies have highlighted the potential of jet substructure techniques to identify the hadronic decays of boosted heavy particles. These studies all rely upon the assumption that the internal substructure of jets generated by QCD radiation is well understood. In this article, this assumption is tested on an inclusive sample of jets recorded with the ATLAS detector in 2010, which corresponds to 35 pb^-1 of pp collisions delivered by the LHC at sqrt(s) = 7 TeV. In a subsample of events with single pp collisions, measurementes corrected for detector efficiency and resolution are presented with full systematic uncertainties. Jet invariant mass, kt splitting scales and n-subjettiness variables are presented for anti-kt R = 1.0 jets and Cambridge-Aachen R = 1.2 jets. Jet invariant-mass spectra for Cambridge-Aachen R = 1.2 jets after a splitting and filtering procedure are also presented. Leading-order parton-shower Monte Carlo predictions for these variables are found to be broadly in agreement with data. The dependence of mean jet mass on additional pp interactions is also explored.
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Limits on contact interactions and leptoquarks at HERA

Authors:

H Abramowicz, B Foster

Abstract:

High-precision HERA data corresponding to a luminosity of around 1fb−1 have been used in the framework of eeqq contact interactions (CI) to set limits on possible high-energy contributions beyond the Standard Model to electron–quark scattering. Measurements of the inclusive deep inelastic cross sections in neutral and charged current ep scattering were considered. The analysis of the ep data has been based on simultaneous fits of parton distribution functions including contributions of CI couplings to ep scattering. Several general CI models and scenarios with heavy leptoquarks were considered. Improvements in the description of the inclusive HERA data were obtained for a few models. Since a statistically significant deviation from the Standard Model cannot be established, limits in the TeV range were set on all models considered.
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METNet: A combined pTmiss working point using a neural network with the ATLAS detector

ATLAS-PHYS-PUB-2021-025, July 2021

Authors:

The ATLAS collaboration

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.
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Measuring the electric dipole moment of the neutron: The cryoEDM experiment

Proceedings of Science EPS-HEP 2009 376

Authors:

CA Baker, SN Balashov, V Francis, K Green, MGD van der Grinten, PS Iaydjiev, SN Ivanov, A Khazov, MAH Tucker, DL Wark, A Davidson, JR Grozier, M Hardiman, PG Harris, JR Karamath, K Katsika, JM Pendlebury, SJM Peeters, DB Shiers, PN Smith, CM Townsley, I Wardell, C Clarke, S Henry, H Kraus, M McCann, P Geltenbort, H Yoshiki

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.