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result(s) for
"David Milstead"
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Baryon number violation in supersymmetry
by
Ferretti, Gabriele
,
Milstead, David A.
,
Calibbi, Lorenzo
in
neutron anti-neutron
,
Supersymmetry
,
Supersymmetry Phenomenology
2016
We study baryon number violation in R-parity violating supersymmetry with focus on Delta B = 2 processes which allow neutron-anti-neutron (n - (n) over bar) oscillations. We provide prospects for going beyond the present limits by means of a new search for n oscillations. The motivation is the recently proposed n - (n) over bar oscillation experiment at the European Spallation Source in Lund, which is projected to be able to improve the current bound on the transition probability in the quasi-free regime by three orders of magnitude. We consider various processes giving rise to baryon number violation and extract the corresponding simplified models, including only the relevant superpartners and couplings. In terms of these models we determine the exclusion limits from LHC searches as well as from searches for flavor transitions, CP violation and di-nucleon decays. We find that, for certain regions of parameter space, the proposed n - (n) over bar experiment has a reach that goes beyond all other experiments, as it can probe gluino and squark masses in the multi-TeV range.
Journal Article
Advancements in Computing and Simulation Techniques for the HIBEAM-NNBAR Experiment
by
Kozela, Adam
,
Nepomuceno, André
,
Pysz, Krzysztof
in
Computation
,
Dark matter
,
Machine learning
2025
The HIBEAM-NNBAR program is a proposed two-stage experiment at the European Spallation Source focusing on searches for baryon number violation processes as well as ultralight dark matter. This paper presents recent advancements in computing and simulation, including machine learning for event selection, fast parametric simulations for detector studies, and detailed modeling of the time projection chamber and readout electronics.
Journal Article
Status of the Design of an Annihilation Detector to Observe Neutron-Antineutron Conversions at the European Spallation Source
by
Dunne, Katherine
,
Santoro, Valentina
,
Nepomuceno, André
in
Antiparticles
,
Atoms & subatomic particles
,
baryon number violation
2022
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.
Journal Article
Computing and Detector Simulation Framework for the HIBEAM/NNBAR Experimental Program at the ESS
by
Dunne, Katherine
,
Kamyshkov, Yuri
,
Nepomuceno, André
in
Antiparticles
,
Computation
,
Neutron flux
2021
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.
Journal Article
Baryon number violation in supersymmetry: n − n¯ oscillations as a probe beyond the LHC
by
Ferretti, Gabriele
,
Milstead, David
,
Calibbi, Lorenzo
in
Classical and Quantum Gravitation
,
Elementary Particles
,
Physics
2016
A
bstract
We study baryon number violation in
R
-parity violating supersymmetry with focus on Δ
B
= 2 processes which allow neutron-anti-neutron (
n
−
n
¯
) oscillations. We provide prospects for going beyond the present limits by means of a new search for
n
−
n
¯
oscillations. The motivation is the recently proposed
n
−
n
¯
oscillation experiment at the European Spallation Source in Lund, which is projected to be able to improve the current bound on the transition probability in the quasi-free regime by three orders of magnitude. We consider various processes giving rise to baryon number violation and extract the corresponding simplified models, including only the relevant superpartners and couplings. In terms of these models we determine the exclusion limits from LHC searches as well as from searches for flavor transitions, CP violation and di-nucleon decays. We find that, for certain regions of parameter space, the proposed
n
−
n
¯
experiment has a reach that goes beyond all other experiments, as it can probe gluino and squark masses in the multi-TeV range.
Journal Article
An updated description of heavy-hadron interactions in Geant-4
by
Milstead, D. A.
,
Mackeprang, R.
in
Astronomy
,
Astrophysics and Cosmology
,
Elementarpartikelfysik
2010
Exotic stable massive particles (SMP) are proposed in a number of scenarios of physics beyond the Standard Model. LHC experiments are expected to be able both to detect and extract the quantum numbers of any SMP with masses around the TeV scale. An understanding of the interactions of SMPs in matter is required to optimise the detection methods and calculate acceptances in an SMP search. In this paper a regge-based model of
R
-hadron scattering is extended and implemented in
Geant-4
. In addition, the implications of
R
-hadron scattering for collider searches are discussed.
Journal Article
Sensitivity of LHC experiments to exotic highly ionising particles
2012
The experiments at the Large Hadron Collider (LHC) are able to discover or set limits on the production of exotic particles with TeV-scale masses possessing values of electric and/or magnetic charge such that they behave as highly ionising particles (HIPs). In this paper the sensitivity of the LHC experiments to HIP production is discussed in detail. It is shown that a number of different detection methods are required to investigate as fully as possible the charge-mass range. These include direct detection as the HIPs pass through either passive or active detectors and, in the case of magnetically charged objects, the so-called induction method with which magnetic monopoles which stop in accelerator and detector material could be observed. The benefit of using complementary approaches to HIP detection is discussed.
Journal Article
Measurements of the Higgs boson inclusive and differential fiducial cross sections in the 4 ℓ decay channel at √ s =13 TeV
by
Nelson, Michael E.
,
Strandberg, Sara
,
Backman, Filip
in
Fysik
,
Natural Sciences
,
Naturvetenskap
2020
Inclusive and differential fiducial cross sections of the Higgs boson are measured in the H -> ZZ* -> 4l (l = e, mu) decay channel. The results are based on proton-proton collision data produced at the Large Hadron Collider at a centre-of-mass energy of 13 TeV and recorded by the ATLAS detector from 2015 to 2018, equivalent to an integrated luminosity of 139 fb(-1). The inclusive fiducial cross section for the H -> ZZ* -> 4l process is measured to be sigma(fid) = 3.28 +/- 0.32 fb, in agreement with the Standard Model prediction of sigma(fid,SM) = 3.41 +/- 0.18 fb. Differential fiducial cross sections are measured for a variety of observables which are sensitive to the production and decay of the Higgs boson. All measurements are in agreement with the Standard Model predictions. The results are used to constrain anomalous Higgs boson interactions with Standard Model particles.
Journal Article
Measurements of Higgs boson production via gluon–gluon fusion and vector-boson fusion using H → WW ∗ → lνlν decays in pp collisions with the ATLAS detector and their effective field theory interpretations
2025
Higgs boson production cross-sections via gluon–gluon fusion and vector-boson fusion in proton–proton collisions are measured in the
decay channel. The Large Hadron Collider delivered proton–proton collisions at a centre-of-mass energy of 13 TeV between 2015 and 2018, which were recorded by the ATLAS detector, corresponding to an integrated luminosity of 140 fb −1 The total cross-sections for Higgs boson production by gluon–gluon fusion and vector-boson fusion times the
branching ratio are measured to be
and
respectively, in agreement with the Standard Model predictions. Higgs boson production is further characterised through measurements of Simplified Template Cross-Sections in a total of fifteen kinematic fiducial regions. A new scheme of kinematic fiducial regions has been introduced to enhance the sensitivity to CP-violating effects in Higgs boson interactions. Both schemes are used to constrain CP-even and CP-odd dimension-six operators in the Standard Model effective field theory
Journal Article