Two recent outreach projects are making use of public communities to enhance and build upon the first phases set up by physicists. “ATLAScraft” is a recreation of ATLAS and the wider CERN complex in ...Minecraft. The basic layout was provided, but school students subsequently researched and created the experiment and subdetector models and their own mini-games to explain various aspects of the LHC and detector physics to others. “HiggsHunters” asked the public to search for displaced vertices in event displays, during which time a pool of trusted members arose in the associated discussion. A second phase also involved schoolchildren, with groups analysing the data this generated, through which they can both learn the principles of scientific research and contribute directly to it.
Dark Matter searches with the ATLAS detector Kalderon, Charles William
26th International Workshop on Deep-Inelastic Scattering and Related Subjects, DIS 2018,Kobe, Japan,2018-04-16 - 2018-04-20,
2018, Letnik:
316
Conference Proceeding
Recenzirano
Odprti dostop
As evinced by multiple astrophysical measurements, a large fraction of the matter in the Universe is in the form of a dark, non-baryonic component. If dark matter interacts weakly with Standard Model ...particles it could be produced at the LHC, escaping the ATLAS detector and thus leaving a signature of large missing transverse momentum. If this interaction is mediated by a kinematically accessible mediator, then that mediator can also give rise to a dijet resonance signature. The latest results of these dijet resonance searches are presented, and their limitations and future prospects discussed.
Ultra-peripheral heavy ion collisions provide a unique opportunity to study the parton distributions in the colliding nuclei via the measurement of photo-nuclear jet production. An analysis of jet ...production in ultra-peripheral Pb+Pb collisions at sNN=5.02 TeV performed using data collected with the ATLAS detector in 2015 is described. The data set corresponds to a total Pb+Pb integrated luminosity of 0.38 nb−1. The ultra-peripheral collisions are selected using a combination of forward neutron and rapidity gap requirements. The cross-sections, not unfolded for detector response, are compared to results from Pythia Monte Carlo simulations re-weighted to match a photon spectrum obtained from the STARlight model. Qualitative agreement between data and these simulations is observed over a broad kinematic range suggesting that using these collisions to measure nuclear parton distributions is experimentally realisable.
Following the extremely successful operation of the Large Hadron Collider at CERN during its first years of operation, the ATLAS and CMS collaborations announced the discovery of a new particle ...compatible with the Higgs boson in July 2012, finishing the complement of particles in the Standard Model. However, no other new particle was even hinted at, confounding predictions of an early discovery of Supersymmetry that would resolve the hierarchy problem and retain low fine-tuning. This thesis presents two searches for new phenomena that would have evaded early efforts. The first, using the full 8 TeV dataset collected in 2012 by ATLAS, targets heavy particles decaying to charm quarks and non-interacting particles through the use of a recently developed charm-jet identification algorithm. No excess is observed over the Standard Model predictions, so results are interpreted in the context of supersymmetric charm production. This is constrained to the highest masses so far, with scharms excluded at the 95% confidence level for masses up to 550 GeV with neutralino masses below 200 GeV. The second search makes use of the 13 TeV dataset collected in 2015, and looks for heavier particles which are produced with far higher cross section at this increased collision energy. It is sensitive to particles decaying via cascades to large numbers (= 7 to = 10) of hadronic jets, with sensitivity enhanced through requirements on the number of jets identified as arising from bottom quarks. Again, no excess is observed, and so limits are set on gluino production in two cascade decay scenarios, with a significant increase in reach obtained over 2012 searches for the same final state - gluino masses below 1400 GeV are excluded in the models considered.
Following the extremely successful operation of the Large Hadron Collider at CERN during its first years of operation, the ATLAS and CMS collaborations announced the discovery of a new particle ...compatible with the Higgs boson in July 2012, finishing the complement of particles in the Standard Model. However, no other new particle was even hinted at, confounding predictions of an early discovery of Supersymmetry that would resolve the hierarchy problem and retain low fine-tuning. This thesis presents two searches for new phenomena that would have evaded early efforts. The first, using the full 8 TeV dataset collected in 2012 by ATLAS, targets heavy particles decaying to charm quarks and non-interacting particles through the use of a recently developed charm-jet identification algorithm. No excess is observed over the Standard Model predictions, so results are interpreted in the context of supersymmetric charm production. This is constrained to the highest masses so far, with scharms excluded at the 95% confidence level for masses up to 550 GeV with neutralino masses below 200 GeV. The second search makes use of the 13 TeV dataset collected in 2015, and looks for heavier particles which are produced with far higher cross section at this increased collision energy. It is sensitive to particles decaying via cascades to large numbers (= 7 to = 10) of hadronic jets, with sensitivity enhanced through requirements on the number of jets identified as arising from bottom quarks. Again, no excess is observed, and so limits are set on gluino production in two cascade decay scenarios, with a significant increase in reach obtained over 2012 searches for the same final state - gluino masses below 1400 GeV are excluded in the models considered.
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