Identification of Dark Matter Particles Bertone, Gianfranco
Nuclear physics. Section B, Proceedings supplement,
August-November 2012, 2012-8-00, Volume:
229-232
Journal Article
A reliable identification of Dark Matter particles can probably be achieved only through a combined analysis of accelerators, direct and indirect searches. I review here the status of these detection ...strategies, and discuss how to combine them in a self-consistent way, keeping into account all astrophysical uncertainties.
Investigations on neutrino physics and astrophysics at Joint Institute for Nuclear Research are presented briefly. The role of Bruno Pontecorvo in the field is stressed in connection with his 100th ...anniversary.
Despite the many successes of the current standard model of cosmology on the largest physical scales, it relies on two phenomenologically motivated constituents, cold dark matter and dark energy, ...which account for approximately 95% of the energy-matter content of the universe. From a more fundamental point of view, however, the introduction of a dark energy (DE) component is theoretically challenging and extremely fine-tuned, despite the many proposals for its dynamics. On the other hand, the concept of cold dark matter (CDM) also suffers from several issues such as the lack of direct experimental detection, the question of its cosmological abundance and problems related to the formation of structure on small scales. A perhaps more natural solution might be that the gravitational interaction genuinely differs from that of general relativity, which expresses itself as either one or even both of the above dark components. Here we consider different possibilities on how to constrain hypothetical modifications to the gravitational sector, focusing on the subset of tensor-vector-scalar (TeVeS) theory as an alternative to CDM on galactic scales and a particular class of chameleon models which aim at explaining the coincidences of DE. Developing an analytic model for nonspherical lenses, we begin our analysis with testing TeVeS against observations of multiple-image systems. We then approach the role of low-density objects such as cosmic filaments in this framework and discuss potentially observable signatures. Along these lines, we also consider the possibility of massive neutrinos in TeVeS theory and outline a general approach for constraining this hypothesis with the help of cluster lenses. This approach is then demonstrated using the cluster lens A2390 with its remarkable straight arc. Presenting a general framework to explore the nonlinear clustering of density perturbations in coupled scalar field models, we then consider a particular chameleon model and highlight the possibility of measurable effects on intermediate scales, i.e. those relevant for galaxy clusters. Finally, we discuss the prospects of applying similar methods in the context of TeVeS and present an ansatz which allows to cast the linear perturbation equations into a more convenient form.
Present measurements of b→cτν and b→uτν transitions differ from the standard model predictions of lepton flavor universality by almost 4σ. We examine new physics (NP) interpretations of this anomaly. ...An effective field theory analysis shows that minimal flavor violating models are not preferred as an explanation, but are also not yet excluded. Allowing for general flavor violation, right-right vector and right-left scalar quark currents are identified as viable candidates. We discuss explicit examples of two Higgs doublet models, leptoquarks as well as quark and lepton compositeness.
In the second part, we show that the charge asymmetry in tt¯ production at the LHC, AC, and the forward-backward asymmetry at the Tevatron, AFB, are in general not tightly correlated. They can even have opposite signs, if the underlying NP model is general enough. We demonstrate this using an example NP model featuring a light axigluon. The small value of AC measured at the LHC is thus shown not to exclude a NP interpretation of the anomalously large AFB at the Tevatron. We identify two observables where significant NP effects are still expected at the Tevatron and the LHC, the b¯b production forward-backward asymmetry and spin polarizations of the pair-produced tops and anti-tops.
The observable consequences of gauge-mediated supersymmetry breaking (GMSB) are reviewed here. Implications of scenarios both with a neutralino and a slepton as the next lightest supersymmetric ...particle (NLSP) are surveyed in relation to hadronic ande+e- colliders. We also discuss the phenomenological consequences of the NLSP decaying slowly, giving rise to delayed events in the detectors.The importance of distinguishing signals of GMSB models from those of the commonly discussed supergravity-type theories is emphasized.
Given the particle content of the standard model without and with a right-handed neutrino, the requirement that all anomalies cancel singles out a set of possible global symmetries which can be ...gauged. I review this topic and propose a new gauge symmetryB — 3LT in the context of the minimal standard model consisting of the usual three families of quarks and leptons plus just onevR. The many interesting phenomenological consequences of this hypothesis are briefly discussed.
Leptoquark-Higgs interactions induce mixing between leptoquark states with different chiralities once the electro-weak symmetry is broken. In such LQ models Majorana neutrino masses are generated at ...1-loop order. Here we calculate the neutrino mass matrix and explore the constraints on the parameter space enforced by the assumption that LQ-loops explain current neutrino oscillation data. LQs will be produced at the LHC, if their masses are at or below the TeV scale. Since the fermionic decays of LQs are governed by the same Yukawa couplings, which are responsible for the non-trivial neutrino mass matrix, several decay branching ratios of LQ states can be predicted from measured neutrino data. Especially interesting is that large lepton flavour violating rates in muon and τ final states are expected. In addition, the model predicts that, if kinematically possible, heavier LQs decay into lighter ones plus either a standard model Higgs boson or a Z0/W± gauge boson. Thus, experiments at the LHC might be able to exclude the LQ mechanism as explanation of neutrino data.
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