Stephanie Majewski is a particle physicist who is actively involved in the search for dark matter and supersymmetry. She was part of the UO's team involved in the quest for the Higgs boson at the Large Hadron Collider near Geneva, Switzerland. Majewski also has had active roles in upgrades to the ATLAS detector at the collider site. Before joining the UO faculty in 2012, she served as a postdoctoral researcher at the Brookhaven National Laboratory. Majewski's research is supported by a five-year early career award from U.S. Department of Energy that runs through 2019.
Areas of Expertise (4)
Media Appearances (3)
cUriOus: Things That Go Bump
Jefferson Public Radio
Stephanie Majewski likes it when things bump into each other.
Which is a huge OVER-simplification of her work in the field of physics at the University of Oregon.
But it IS true that she learns a lot from atoms crashing into each other, especially at the Large Hadron Collider (LHC) in Switzerland.
Dr. Majewski's work is the topic of this month's installment of "cUriOus: Research Meets Radio."
We pick her brain about dark matter, supersymmetry, and more...
Stephanie Majewski selected for national Early Career Award
Around the O
UO physicist Stephanie A. Majewski is among 35 U.S. scientists chosen to receive substantial funding for the next five years under the U.S. Department of Energy's Early Career Research Program.
The program is designed to bolster the nation’s scientific workforce by providing support to select researchers during the crucial early career years, when many scientists do their most formative work...
The Software Brains Behind the Particle Colliders
Obviously, this a pretty significant culling process, one complicated by the fact that we're hoping to see particles that have been predicted by various theories (ideally, we'd also detect things that the theorists aren't expecting). How does that work? A hint of that was provided when Stephanie Majewski was asked about one model for the existence of dimensions beyond our well-known four. "Extra dimensions will give us lots of muon jets," Majewski said, "you couldn't miss it." In short, most of the things we're expect or hoping to find are the product of some fairly specific predictions, and will produce equally predictable patterns of particles in the detectors (Chris Lee covered this in a bit more detail)...
A search for direct pair production of a scalar partner to the top quark in events with four or more jets plus missing transverse momentum is presented. An analysis of 13.3 fb−1−1 of s√=13s=13 TeV proton-proton collisions collected using the ATLAS detector at the LHC yielded no significant excess over the Standard Model background expectation. In the supersymmetric interpretation, the top squark is assumed to decay via t̃ →tχ̃ 01t~→tχ~10, t̃ →bχ̃ ±1→bW(∗)χ̃ 01t~→bχ~1±→bW(∗)χ~10, or t̃ →bWχ̃ 01t~→bWχ~10, where χ̃ 01χ~10 (χ̃ ±1χ~1±) denotes the lightest neutralino (chargino). Exclusion limits are reported in terms of the top squark and neutralino masses. Assuming branching fractions of 100% to tχ̃ 01tχ~10, top squark masses in the range 310–820 GeV are excluded for χ̃ 01χ~10 masses below 160 GeV. In the case where mt̃ ∼mt+mχ̃ 01mt~∼mt+mχ~10 top squark masses between 23–380 GeV are excluded. Limits are also reported in terms of simplified models describing the associated production of dark matter (χχ) with top quark pairs through a (pseudo)scalar mediator; models with a global coupling of 3.5, mediator masses up to 300 GeV, and χχ masses below 40 GeV are excluded.
This paper reviews and extends searches for the direct pair production of the scalar supersymmetric partners of the top and bottom quarks in proton–proton collisions collected by the ATLAS collaboration during the LHC Run 1. Most of the analyses use 20 fb−1 of collisions at a centre-of-mass energy of √s=8 TeV, although in some case an additional 4.7 fb−1 of collision data at √s =7 TeV are used. New analyses are introduced to improve the sensitivity to specific regions of the model parameter space. Since no evidence of third-generation squarks is found, exclusion limits are derived by combining several analyses and are presented in both a simplified model framework, assuming simple decay chains, as well as within the context of more elaborate phenomenological supersymmetric models.
A summary of the constraints from the ATLAS experiment on R-parity-conserving supersymmetry is presented. Results from 22 separate ATLAS searches are considered, each based on analysis of up to 20.3 fb−1 of proton-proton collision data at centre-of-mass energies of s√=7s=7 and 8 TeV at the Large Hadron Collider. The results are interpreted in the context of the 19-parameter phenomenological minimal supersymmetric standard model, in which the lightest supersymmetric particle is a neutralino, taking into account constraints from previous precision electroweak and flavour measurements as well as from dark matter related measurements. The results are presented in terms of constraints on supersymmetric particle masses and are compared to limits from simplified models. The impact of ATLAS searches on parameters such as the dark matter relic density, the couplings of the observed Higgs boson, and the degree of electroweak fine-tuning is also shown. Spectra for surviving supersymmetry model points with low fine-tunings are presented.
Measurements of charged particle distributions, sensitive to the underlying event, have been performed with the ATLAS detector at the LHC. The measurements are based on data collected using a minimum-bias trigger to select proton-proton collisions at center-of-mass energies of 900 GeV and 7 TeV. The “underlying event” is defined as those aspects of a hadronic interaction attributed not to the hard scattering process, but rather to the accompanying interactions of the rest of the proton. Three regions are defined in azimuthal angle with respect to the highest transverse momentum charged particle in the event, such that the region transverse to the dominant momentum-flow is most sensitive to the underlying event. In each of these regions, distributions of the charged particle multiplicity, transverse momentum density, and average pT are measured. The data show generally higher underlying event activity than that predicted by Monte Carlo models tuned to pre-LHC data.