Events - Page 27
Joachim Kopp, University of Mainz
We consider two scenarios in which the first experimental hint for the particle physics nature of dark matter (DM) comes from highly boosted DM particles. The first scenario interprets the high energy events observed in IceCube as a signal of PeV DM decaying to a much lighter state, which in turn is detected in IceCube. The model explains the event rate and spectrum observed in IceCube, it shows a preference for shower-like events at the highest energies, and it features a small dip in the spectrum at few hundred TeV. The second scenario is a very generic dark photon model. We point out that DM production at the LHC can be accompanied by final state radiation in the form of "dark photons", which decay back to SM particles. We discuss this process analytically and numerically in analogy to collinear particle showers in QED and QCD. The smoking gun signal of this "radiating DM" scenario are collimated jets or lepton jets with unusual properties.
(The slides are now available.)
Bryan Webber, University of Cambridge
Tests of the Standard Model and searches for new phenomena at the Large Hadron Collider depend heavily on computer simulations of signal and background processes. Monte Carlo event generators aim to simulate the final states of high-energy collisions in full detail, down to the level of individual stable particles. The talk will review the physics behind these programs, their main ingredients and theoretical status, with emphasis on recent work to improve their precision. Comparisons with the latest LHC data will illustrate these developments, and the places where further improvements are needed.
(The Slides are now available)
Gabrijela Zaharijas, University of Nova Gorica
The Isotropic Gamma-ray Background (IGRB) up to 820 GeV has been recently measured by the Fermi LAT using 50 months of data. Understanding the origin of this IGRB is a crucial task that requires to identify and model possible contributions in detail. Dark matter annihilation signals integrated over all cosmic epochs have been proposed to account for a portion of the measured IGRB intensity. I will discuss the theoretical predictions for the clustering of dark matter signal and refined predictions for the contribution of the unresolved astrophysical source populations to the IGRB. We use these ingredients to set the limits on the dark matter annihilation cross section which turn out to be comparable to the ones set by the observation of dwarf spheroidal galaxies and Milky Way halo for sub-TeV dark matter masses, while they improve upon them at the high mass end due to the significant energy extension of the isotropic measurement. In addition I will compare these finding with complementary techniques which probe the cosmological dark matter annihilations, as those of the small scale angular anisotropies and gamma ray cross correlations with galaxy catalogs.
(Slides are now available)
David Mota, ITA
Several extensions of the standard cosmological model include scalar fields as new degrees of freedom in the underlying gravitational theory. A particular class of these scalar field theories include screening mechanisms intended to hide the scalar field below observational limits in the solar system, but not on galactic scales, where data still gives freedom to find possible signatures of their presence. I describe how one can use structure formation to study screening mechanisms in extensions to General Relativity. In particular, I will present observable signatures of modified gravity in the nonlinear matter power spectrum, on the halo mass function and other properties of galaxy clusters. Those would help us to discriminate between models with and without scalar fields and even between different screening mechanisms.
(The slides are now available)
Dr. Terry Onsager, National Oceanic and Atmospheric Administration, USA/Space Weather Prediction Center, USA.
Kåre Olaussen, NTNU Trondheim
After 100 years people are still trying to modify (or mutilate) the Einstein General Theory of Relativity. I will first give a general overview of various possibilities, as I learned at a workshop this summer.
Next I will discuss in more detail the possibility of a non-minimal coupling of Einstein gravity to scalar fields, and some modest computations I have done with a master student on that model (in the Robertson-Walker geometry).
The presentation will mainly be aimed at an audience with limited experience with general relativity.
(Slides will be available after the talk).
Ipsita Mandal, Perimeter institute
We devise a renormalization group analysis for quantum field theories with Fermi surface to study scaling behaviour of non-Fermi liquid states in a controlled approximation. The non-Fermi liquid fixed points are identified from a Fermi surface in (m+1) spatial dimensions, while the co-dimension of Fermi surface is also extended to a generic value. We also study superconducting instability in such systems as a function of dimension and co-dimension of the Fermi surface. The key point in this whole analysis is that unlike in relativistic QFT, the Fermi momentum kF enters as a dimensionful parameter, thus modifying the naive scaling arguments. The effective coupling constants are found to be combinations of the original coupling constants and kF.
The slides are now available.
Tomás Gonzalo, University College London
Grand Unified Theories are a very well motivated extension of the Standard Model, but the landscape of models and possibilities is overwhelming, and different patterns present rather distinct and unique phenomenology. We present in this work a way to automatise the model building process, by considering a top-bottom approach that constructs viable and sensible theories from a small and controllable set of inputs at the high scale. By providing a GUT scale symmetry group and the field content, all the possible symmetry breaking paths are generated and checked for consistency, ensuring anomaly cancellation and Standard Model embedding. We emphasise the usefulness of this process for various models such as a Supersymmetric SO(10) model, a non-SUSY left-right symmetry model or a theory of GUT inflation.
(Slides are now available).
The conference aims to promote scientific exchange and the development of novel ideas, with a particular emphasis on interdisciplinarity.
Yong Tang, KIAS
This talk will discuss some possible connections between neutrinos and dark matter, in light of astrophysical observations. Contents include self-interacting dark matter, sterile neutrinos and IceCube Events.
The slides are now available.
Kalliopi Petraki, NIKEF Amsterdam [slides]
Observations of the galactic and sub-galactic structure of our universe suggest that a shift from the collisionless cold dark matter paradigm may be needed. Dark matter with sizable self-interactions offers a compelling explanation of these observations.
Particle physics models of self-interacting dark matter can be well accommodated within the asymmetric dark matter scenario. Asymmetric dark matter hypothesizes that the relic dark matter abundance is due to an excess of dark particles over antiparticles, and allows for sizable and direct couplings of dark matter to light force mediators.
In addition, the dark particle-antiparticle asymmetry may be related to the baryon asymmetry of the universe, thus offering a dynamical explanation for the similarity of the dark and the ordinary matter abundances. Exploring the low-energy phenomenology of self-interacting asymmetric dark matter, including the effect on the dynamics of dark matter halos and possible detection strategies, presupposes understanding the cosmology of these models, which can be quite involved. I will discuss the above, and illustrate them in the context of the atomic dark matter model.
Kai Schmidt Hoberg, DESY, Hamburg [slides]
I will review motivations for the existence of self interacting dark matter and discuss possible astrophysical observables. Self-interactions of dark matter particles can potentially lead to an observable separation between the dark matter halo and the stars of a galaxy moving through a region of large dark matter density. Such a separation has recently been observed in a galaxy falling into the core of the galaxy cluster Abell 3827. I discuss the DM self-interaction cross section needed to reproduce the observed effects.
The research centre for dark matter, The Strategic Dark Matter Initiative - SDI, will officially be launched on Friday, and invites you all to a popular science lecture, with coffee and snacks.
Thomas Jacques, Université de Genève, Switzerland [slides]
As beyond-standard-model physics continues to elude discovery at the LHC, it becomes increasingly important to ask what we can learn about dark matter in a model-independent way. I will introduce the theory and usage of effective operators; these have become popular in recent years as a way to construct model-independent constraints on dark matter, but at LHC energies it is crucial to understand their significance and limitations, and how they can be used to compare the reach of vastly different experiments. With this in mind, I will also discuss the next step beyond effective operators, and techniques to link the search for missing energy with the much-sought-after Dark Matter.
Mark Burgess
Physics is probably the most successful science when it comes to describing how things behave, but it avoids interpreting the meaning or the intent of behaviours. In technology, especially IT, meaning and intent are at the top of the list when it comes to description, but IT fails to describe system dynamics convincingly. Promise Theory is an attempt to unify dynamical and semantic descriptions of systems, inspired by the successes of physics - and it sheds an interesting light on both fundamental physics and information science.
Thomas Schwetz-Mangold, Stockholms Universitet [slides]
The observation of neutrino oscillations requires that neutrinos have a tiny but non-zero mass. This implies that the Standard Model of particle physics has to be extended in some way beyond its original formulation where neutrinos are massless. We review the present status of neutrino oscillations and give a brief outlook on future developments in the field. We speculate on the implications for physics beyond the Standard Model and discuss the challenges to identify the mechanism responsible for neutrino mass.
Nils-Erik Bomark, University of Warsaw
Within the MSSM, the heavy stops required to meet the experimental value of the Higgs mass, poses tension with naturalness, the main reason to believe in supersymmetry at LHC scales. This is alleviated in the NMSSM, where especially the possibility of a light singlet-like scalar can easily push the Higgs mass up to the measure value.
The presence of a singlet-like scalar and pseudoscalar gives rise to LHC phenomenology potentially rather different from the MSSM as these particles can be very light without coming in conflict with observations. In this presentation I will discuss the discovery prospects of these light pseudoscalars in the NMSSM. As direct production of such singlet-dominated particles is very difficult, the main focus will be on channels where heavier scalars decay to pairs of pseudoscalars or pseusodscalars and Z bosons. I will demonstrate that the LHC should be capable of probing a large part of the NMSSM parameter space through these channels.
Carmelo Evoli, Universität Hamburg [slides]
At GeV-TeV energies the propagation of CRs in our Galaxy is diffusive. Current models of galactic propagation are based on a simplified approach for which diffusion is constant and isotropic. In fact, diffusion transport must be described as in-homogenous and anisotropic and experimental data have now reached an accuracy that allows to study such effects.
In my talk, I will present some of the consequences of adopting realistic diffusion models for the propagation of galactic CRs, and I will show how these models allow a better understanding of local observations and diffusion emissions within an unified framework.
In the second part of my talk, I will focus on antiprotons as a tool to set constraints on DM models. In particular, I will discuss the uncertainties associated to both standard astrophysical and DM originated antiprotons. I will show on which extent current antiproton data can place tight constraints on DM models, excluding some of those suggested in connection with indirect and direct searches.
Marco Cirelli, Saclay, France [slides]
The field of Dark Matter Indirect Detection is in a thriving but somewhat chaotic moment: quite a few hints of possible detection of signals of DM (over a large range of masses and, in general, inferred properties) are confronted with stringent constraints, often based on the same experiments that provide the possible hints. In turn, this spurs a lot of theoretical activity, aimed at phenomenologically analyzing the claims and, perhaps, at embedding them in wider model building. I will briefly review the current status of the searches, mention the most debated hints and sketch the general directions of the theory activity.
Daniele Gaggero, SISSA, Trieste, Italy [slides]
In the first part of the talk, after a general introduction on the physics of cosmic rays (CRs), I present a detailed overview on recent results regarding modeling of CR propagation in the Galaxy and in the Heliosphere. In particular I focus on the necessity to go beyond the standard and simplified picture of uniform and homogeneous diffusion, showing that gamma-ray data point towards different propagation regimes in different regions of the Galaxy. I also sketch the impact of large-scale structure on CR observables. Concerning the propagation of the Heliosphere, I mention the necessity to consider a charge-dependent modulation scenario.
In the second part, I discuss several aspects of the recent claim of a gamma-ray excess in the Galactic center region, discussing in particular the interpretation in terms of Dark Matter, compared to other astrophysical interpretations. I will emphasize the interplay between the non-trivial aspects of CR propagation discussed in the first part and the understanding of the GC excess origin. In particular, I will show in detail how the knowledge of the CR transport parameters and solar modulation is crucial to investigate the compatibility with other channels (namely antiprotons) and to provide alternative astrophysical interpretations.
Susanne Viefers, UiO
In recent years there has been substantial interest in the study of strongly correlated states of cold atoms, analogous to exotic states known from low-dimensional electron systems - one 'holy grail' being experimental realisation of quantum Hall-like states in atomic Bose condensates. In particular there have been many studies on the rotational properties of cold atom systems, as rotation is the conceptually simplest way of simulating a magnetic field for electrically neutral atoms. Even richer physics is expected in the case of two-species gases, such as mixtures of two types of bosonic atoms.
In this talk I will give an introduction to the field, followed by some recent results on the rotational properties of two-species Bose gases in the lowest Landau level. In particular we show that, contrary to expectations, trial wave functions of the composite fermion (CF) type, known from quantum Hall physics, give a very accurate description of this system. It is also shown how working only with a certain subset of possible CF candidate wave functions constitutes a major computational simplification without much loss of accuracy for the low-lying states. Finally I will briefly discuss some striking mathematical identities between seemingly different CF candidate states, of interest for a better understanding of the CF method in general.
Each year in spring, research institutes and universities around the world invite high-school students for a day-long programme to experience life at the forefront of basic research. These International Masterclasses give students the opportunity to be particle physicists for a day by analysing real data from the Large Hadron Collider, or LHC, at CERN.
Abram Krislock, UiO
During Supersymmetry phenomenology research, involving simulations of the Large Hadron Collider experiments, a certain mistrust of data analysis using common histograms arose. Someone once said, "Change the bins and try the fit again..." A quest began to eliminate the bins entirely. After a recent study, it was clear that a deeper understanding of statistics was needed to complete this quest. A new probability calculus was discovered, leading to an interesting new data smoothing technique.
Each year in spring, research institutes and universities around the world invite high-school students for a day-long programme to experience life at the forefront of basic research. These International Masterclasses give students the opportunity to be particle physicists for a day by analysing real data from the Large Hadron Collider, or LHC, at CERN.