1,720,968 research outputs found
Dark matter models: Signals and backgrounds at the LHC and future colliders
No full textWe explore the phenomenological signals and potential backgrounds of various Minimal Consistent Dark Matter (MCDM) models in the context of the Large Hadron Collider (LHC), non-LHC and future collider experiment searches. We study two key background processes to Dark Matter (DM), and indeed more general beyond the Standard Model (BSM) physics, at the LHC as part of the ATLAS collaboration. For the production of boson in association with high jets, we present results for data-driven modelling and multi-jet background derivation. We also investigate non-perturbative corrections, and comparisons of our Monte Carlo generator results from the analysis' Rivet routine. For the production of boson in association with heavy flavour quarks (i.e. and quarks) we present a novel approach to jet flavour discrimination through a fitting algorithm. We explore the full parameter space and provide new LHC limits for both inert 2-Higgs Doublet Model (i2HDM) scalar DM and Minimal Fermionic DM (MFDM) at 13 TeV through a multilepton+missing analysis. We parametrise in terms of mass splits, providing a more intuitive picture of the underlying physics in addition to a no-lose theorem in MFDM. We find significant contributions to sensitivity from 3-lepton final states. These limits and efficiencies we provide can then be extrapolated and applied in a model-independent way. We additionally study non-LHC constraints from relic density requirements, direct and indirect detection, including Cosmic Microwave Background (CMB) and future Cherenkov Telescope Array (CTA) projections. These are combined for a comprehensive picture of the MFDM model, in addition to a summary of the i2HDM limits. We utilise a model independent method for discriminating DM mass at future colliders, by analysing the energy distributions of charged DM decay products in cascades. We apply this to the i2HDM and MFDM models with two example benchmark points that provide correct observed DM density and comply with direct detection experimental bounds. We additionally present a method for discriminating DM spin by observing angular distributions of from reconstructed dijets
Multilepton Signatures from Dark Matter at the LHC
Full text linkLeptonic signatures of Dark Matter (DM) are one of the cleanest ways to
discover such a secluded form of matter at high energy colliders. We explore
the full parameter space relevant to multi-lepton (2- and 3-lepton) signatures
at the Large Hadron Collider (LHC) from representative minimal consistent
models with scalar and fermion DM. In our analysis, we suggest a new
parametrisation of the model parameter spaces in terms of the DM mass and mass
differences between DM and its multiplet partners. This parametrisation allows
us to explore properties of DM models in their whole parameter space. This
approach is generic and quite model-independent since the mass differences are
related to the couplings of the DM to the Standard Model (SM) sector. We
establish the most up-to-date LHC limits on the inert 2-Higgs Doublet Model
(i2HDM) and Minimal Fermion DM (MFDM) model parameter spaces, by using the
complementary information stemming from 2- and 3-lepton signatures. We provide
a map of LHC efficiencies and cross-section limits for such 2- and 3-lepton
signatures allowing one to easily make model-independent reinterpretations of
LHC results for analogous classes of models. We also present combined
constraints from the LHC, DM relic density and direct search experiments
indicating the current status of the i2HDM and MFDM model
Decoding Dark Matter at future colliders
No full textWe explore the potential of the colliders to discover dark matter
and determine its properties such as mass and the spin. For this purpose we
study spin zero and spin one-half cases of dark matter, which belongs to
weak doublet and therefore has the charged doublet partner, . For
the case of scalar dark matter we chose Inert Doublet Model, while for the case
of fermion dark matter we suggest the new minimal fermion dark matter model
with only three parameters. We choose two benchmarks for the models under study
which provide the correct amount of observed DM relic density and consistent
with the current DM searches. We focus on the particular process at 500 GeV ILC collider
which gives rise to the "di-jet + + missing " signature and study it
at the level of fast detector simulation, taking into account Bremsstrahlung
and ISR effects. We have found that two kinematical observables -- the energy
of the muon, , and the angular distribution of -boson, reconstructed
from di-jet, are very powerful in determination of DM mass
and spin, respectively. In particular we have demonstrated that in case of
fermion DM, the masses can be measured with a few percent accuracy already at
500 fb integrated luminosity. At the same time, the scalar DM model
which has about an order of magnitude lower signal, requires about factor of 40
higher luminosity to reach the same accuracy in the mass measurement. We have
found that one can distinguish fermion and scalar DM scenarios with about 2
ab total integrated luminosity or less without using the information on
the cross sections for benchmarks under study.Comment: Updated with the Electroweak Precision S,T,U oblique parameters
analytical and numerical evaluatio
(Re)interpreting the results of new physics searches at the LHC
No full textWhile overwhelming cosmological evidences point to the existence of Dark Matter (DM), only its gravitational interaction has been experimentally confirmed. Limitations on the most general mono-X DM signature at colliders motivate searches beyond this. This could manifest in the form of a weak multiplet/doublet DM via weak interactions giving multilepton plus missing energy final states that can be probed at the LHC. Here we present our latest limits on inert 2-Higgs Doublet model (I2HDM) and Minimal Fermion Dark Matter model (MFDM) for 8/13 TeV pp collisions, producing 2-3 leptons plus missing energy final states, using CheckMATE
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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