Di-photon excess illuminates Dark Matter

We propose a simplified model of dark matter with a scalar mediator to accommodate the di-photon excess recently observed by the ATLAS and CMS collaborations. Decays of the resonance into dark matter can easily account for a relatively large width of the scalar resonance, while the magnitude of the total width combined with the constraint on dark matter relic density lead to sharp predictions on the parameters of the Dark Sector. Under the assumption of a rather large width, the model predicts a signal consistent with ~300 GeV dark matter particle in channels with large missing energy. This prediction is not yet severely bounded by LHC Run I searches and will be accessible at the LHC Run II in the jet plus missing energy channel with more luminosity. Our analysis also considers astrophysical constraints, pointing out that future direct detection experiments will be sensitive to this scenario.Comment: 23 pages, 8 figures. Added 2 figures and more discussion

MadDM: New Dark Matter Tool in the LHC era

We present the updated version of MadDM, a new dark matter tool based on MadGraph5_aMC@NLO framework. New version includes direct detection capability in addition to relic abundance computation. In this article, we provide short description of the implementation of relevant effective operators and validations against existing results in literature.Comment: 4 pages. Submitted to the proceedings of PPC 201

Measuring Boosted Tops in Semi-leptonic ttˉt\bar t Events for the Standard Model and Beyond

We present a procedure for tagging boosted semi-leptonic $t\bar t$ events based on the Template Overlap Method. We introduce a new formulation of the template overlap function for leptonically decaying boosted tops and show that it can be used to compensate for the loss of background rejection due to reduction of b-tagging efficiency at high $p_T$. A study of asymmetric top pair production due to higher order effects shows that our approach improves the resolution of the truth level kinematic distributions. We show that the hadronic top overlap is weakly susceptible to pileup up to 50 interactions per bunch crossing, while leptonic overlap remains impervious to pileup to at least 70 interactions. A case study of Randall-Sundrum Kaluza-Klein gluon production suggests that the new formulation of semi-leptonic template overlap can extend the projected exclusion of the LHC $\sqrt{s}$ = 8 TeV run to Kaluza-Klein gluon masses of 2.7 TeV, using the leading order signal cross section.Comment: 34 pages, 18 figures; v2. Matches version accepted for publication in JHEP. We added new paragraphs in the introduction and in section 7 to explain more clearly the scope of our study and limitations. Results unchange

Direct Detection of Dark Matter with MadDM v.2.0

We present MadDM v.2.0, a numerical tool for dark matter physics in a generic model. This version is the next step towards the development of a fully automated framework for dark matter searches at the interface of collider physics, astro-physics and cosmology. It extends the capabilities of v.1.0 to perform calculations relevant to the direct detection of dark matter. These include calculations of spin-independent/spin-dependent nucleon scattering cross sections and nuclear recoil rates (as a function of both energy and angle), as well as a simplified functionality to compare the model points with existing constraints. The functionality of MadDM v.2.0 incorporates a large selection of dark matter detector materials and sizes, and simulates detector effects on the nuclear recoil signals. We validate the code in a wide range of dark matter models by comparing results from MadDM v.2.0 to the existing tools and literature.Comment: 38 pages, 8 figures, 5 tables; v2. Matches the version accepted for publication in Physics of the Dark Universe. We have improved table IV by validating the other sps points of the MSS

Playing Tag with ANN: Boosted Top Identification with Pattern Recognition

Many searches for physics beyond the Standard Model at the Large Hadron Collider (LHC) rely on top tagging algorithms, which discriminate between boosted hadronic top quarks and the much more common jets initiated by light quarks and gluons. We note that the hadronic calorimeter (HCAL) effectively takes a "digital image" of each jet, with pixel intensities given by energy deposits in individual HCAL cells. Viewed in this way, top tagging becomes a canonical pattern recognition problem. With this motivation, we present a novel top tagging algorithm based on an Artificial Neural Network (ANN), one of the most popular approaches to pattern recognition. The ANN is trained on a large sample of boosted tops and light quark/gluon jets, and is then applied to independent test samples. The ANN tagger demonstrated excellent performance in a Monte Carlo study: for example, for jets with p_T in the 1100-1200 GeV range, 60% top-tag efficiency can be achieved with a 4% mis-tag rate. We discuss the physical features of the jets identified by the ANN tagger as the most important for classification, as well as correlations between the ANN tagger and some of the familiar top-tagging observables and algorithms.Comment: 20 pages, 9 figure

Recommendations of the LHC Dark Matter Working Group: Comparing LHC searches for heavy mediators of dark matter production in visible and invisible decay channels

Weakly-coupled TeV-scale particles may mediate the interactions between normal matter and dark matter. If so, the LHC would produce dark matter through these mediators, leading to the familiar "mono-X" search signatures, but the mediators would also produce signals without missing momentum via the same vertices involved in their production. This document from the LHC Dark Matter Working Group suggests how to compare searches for these two types of signals in case of vector and axial-vector mediators, based on a workshop that took place on September 19/20, 2016 and subsequent discussions. These suggestions include how to extend the spin-1 mediated simplified models already in widespread use to include lepton couplings. This document also provides analytic calculations of the relic density in the simplified models and reports an issue that arose when ATLAS and CMS first began to use preliminary numerical calculations of the dark matter relic density in these models.Comment: 19 pages, 4 figures; v2: author list and LaTeX problem fixe

Between two worlds : approaching Balkan oral music tradition through the use of technology as a compositional and performing medium

This text explores the problems of interpreting musical identity, meaning, and sociocultural value of a compositional work influenced by two traditions with different values: the modernist tradition based on Western European classical heritage, and the oral tradition of the Balkans. It also follows the process of transformation and recreation of the author's musical language: from classical, notation-oriented to a more intuitive, improvisational and live-performance based. Through detailing some of the experiences of the author as a composer and a performer, it also discusses some observations on the ways in which this discrepancy between two traditions and practices has affected and still influences those creative practices in Serbia and the former Yugoslavia that relate to traditional music and its derivations. By identifying musical performance within certain socio-cultural contexts this dichotomy can be highlighted. As a result, a substantial part of this text focuses on investigating the capacity of a technologically assisted composition and performance practice to overcome this issue. Technology is here perceived not only as an instrument for recording, improvising, composing and performing but also as a medium which communicates musical value. In this study, the oral tradition from the Balkans was approached not only as a purely acoustic phenomenon, but it also included a raised awareness of the nature of the continuous fusion of various cultures in the region, as well as existing cultural and religious antagonisms. This study investigates the problems of constructing musical identity as well as the meaning of an author’s creative practice in relation to the socio-cultural environment of its origin, whilst observing its reception by audiences outside the Balkan region. Socio-cultural environments are established through exploring the writings of the authors that depict the Balkans historical, cultural and musical spheres in relation to other cultural practices and influences

Implications of a High-Mass Diphoton Resonance for Heavy Quark Searches

Heavy vector-like quarks coupled to a scalar $S$ will induce a coupling of this scalar to gluons and possibly (if electrically charged) photons. The decay of the heavy quark into $Sq$, with $q$ being a Standard Model quark, provides, if kinematically allowed, new channels for heavy quark searches. Inspired by naturalness considerations, we consider the case of a vector-like partner of the top quark. For illustration, we show that a singlet partner can be searched for at the 13$\,$TeV LHC through its decay into a scalar resonance in the $2\gamma+\ell + X$ final states, especially if the diphoton branching ratio of the scalar $S$ is further enhanced by the contribution of non coloured particles. We then show that conventional heavy quark searches are also sensitive to this new decay mode, when $S$ decays hadronically, by slightly tightening the current selection cuts. Finally, we comment about the possibility of disentangling, by scrutinising appropriate kinematic distributions, heavy quark decays to $St$ from other standard decay modes.Comment: 8 pages, 3 figures and 1 table; v3: typos fixed. Matches published versio