273 research outputs found

    The Minimal Model for Dark Matter and Unification

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    Gauge coupling unification and the success of TeV-scale weakly interacting dark matter are usually taken as evidence of low energy supersymmetry (SUSY). However, if we assume that the tuning of the higgs can be explained in some unnatural way, from environmental considerations for example, SUSY is no longer a necessary component of any Beyond the Standard Model theory. In this paper we study the minimal model with a dark matter candidate and gauge coupling unification. This consists of the SM plus fermions with the quantum numbers of SUSY higgsinos, and a singlet. It predicts thermal dark matter with a mass that can range from 100 GeV to around 2 TeV and generically gives rise to an electric dipole moment that is just beyond current experimental limits, with a large portion of its allowed parameter space accessible to next generation EDM and direct detection experiments. We study precision unification in this model by embedding it in a 5-D orbifold GUT where certain large threshold corrections are calculable, achieving gauge coupling and b-tau unification, and predicting a rate of proton decay just beyond current limits.Comment: 20 pages, 10 figures. v2: Minor typos and Reference errors corrected. Modified explanation of the KK mode contribution to runnin

    Spinless photon dark matter from two universal extra dimensions

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    We explore the properties of dark matter in theories with two universal extra dimensions, where the lightest Kaluza-Klein state is a spin-0 neutral particle, representing a six-dimensional photon polarized along the extra dimensions. Annihilation of this 'spinless photon' proceeds predominantly through Higgs boson exchange, and is largely independent of other Kaluza-Klein particles. The measured relic abundance sets an upper limit on the spinless photon mass of 500 GeV, which decreases to almost 200 GeV if the Higgs boson is light. The phenomenology of this dark matter candidate is strikingly different from Kaluza-Klein dark matter in theories with one universal extra dimension. Elastic scattering of the spinless photon with quarks is helicity suppressed, making its direct detection challenging, although possible at upcoming experiments. The prospects for indirect detection with gamma rays and antimatter are similar to those of neutralinos. The rates predicted at neutrino telescopes are below the sensitivity of next-generation experiments.Comment: 22 pages. Figure 7 corrected, leading to improved prospects for direct detection. Some clarifying remarks include

    Outside interference or Hong Kong embracing its unique identity? : The Chinese Universities Shakespeare Festival

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    Ongoing clashes between Hong Kong citizens and its government have foregrounded questions about outside interference in Hong Kong’s politics (largely from the government and media of People’s Public of China), as well as debate about what institutions in Hong Kong are neo-colonial, heavily inflected with nostalgia for British colonialism, or in the process of being ‘colonised’ by the People’s Republic of China. This article looks at Shakespeare in Hong Kong (and, to some extent, greater Chinese) theatre and education as one of those contested institutions, using the particular case of the now-defunct Chinese Universities Shakespeare Festival. The author probes their initial, surface impression of the festival as a simple outpouring of colonial sentiment and impulse, using its sizeable archives to realise a reading of the institution that highlights the complexities of international and intra-regional politics, culture and identity in Hong Kong and greater China. It builds on the Hong Kong literary critic Michael Ingham’s call for attention to Hong Kong’s quest – sometimes overt (as in the demonstrations of 2019), sometimes implicit (in the body of literature Ingham explores in his cultural and literary history) – for a unique, post-colonial identity that is inspired – but, critically, not confined – by its Chinese and British histories. The article briefly outlines the origins and set-up of the festival before juxtaposing the dominance of English language and culture in it with the opportunities it presents (seized by several teams) for intra-regional cooperation, competition and sharing diverse, greater Chinese cultures. The article offers a model for critically appraising other institutions and cultural products in Hong Kong in ways that resist easy binaries of British or Chinese, colonial or indigenous

    The New Fat Higgs: Slimmer and More Attractive

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    In this paper we increase the MSSM tree level higgs mass bound to a value that is naturally larger than the LEP-II search constraint by adding to the superpotential a λSHuHd\lambda S H_{u}H_{d} term, as in the NMSSM, and UV completing with new strong dynamics {\it before} λ\lambda becomes non-perturbative. Unlike other models of this type the higgs fields remain elementary, alleviating the supersymmetric fine-tuning problem while maintaining unification in a natural way.Comment: 14 pages and 2 figures. Added references and updated argument about constraints from reheating temperatur

    East Asia and the global/transatlantic/Western crisis

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    This paper introduces the special collection on East Asia and the Global Crisis. After justifying why a focus on East Asia is appropriate, it draws out the main themes that run through the individual contributions. These are the extent to which the region is decoupling from the global economy (or the West), the increasing legitimacy of statist alternatives to neoliberal development strategies, and the impact of crises on the definition of ―region‖ and the functioning of regional institutions and governance mechanisms

    Precision Electroweak Observables in the Minimal Moose Little Higgs Model

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    Little Higgs theories, in which the Higgs particle is realized as the pseudo-Goldstone boson of an approximate global chiral symmetry have generated much interest as possible alternatives to weak scale supersymmetry. In this paper we analyze precision electroweak observables in the Minimal Moose model and find that in order to be consistent with current experimental bounds, the gauge structure of this theory needs to be modified. We then look for viable regions of parameter space in the modified theory by calculating the various contributions to the S and T parameters.Comment: v2: 17 pages, 9 figures. Typeset in JHEP style. Added a references and two figures showing parameter space for each of two reference points. Corrected typo

    The Gran Sasso muon puzzle

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    We carry out a time-series analysis of the combined data from three experiments measuring the cosmic muon flux at the Gran Sasso laboratory, at a depth of 3800 m.w.e. These data, taken by the MACRO, LVD and Borexino experiments, span a period of over 20 years, and correspond to muons with a threshold energy, at sea level, of around 1.3 TeV. We compare the best-fit period and phase of the full muon data set with the combined DAMA/NaI and DAMA/LIBRA data, which spans the same time period, as a test of the hypothesis that the cosmic ray muon flux is responsible for the annual modulation detected by DAMA. We find in the muon data a large-amplitude fluctuation with a period of around one year, and a phase that is incompatible with that of the DAMA modulation at 5.2 sigmas. Aside from this annual variation, the muon data also contains a further significant modulation with a period between 10 and 11 years and a power well above the 99.9% C.L threshold for noise, whose phase corresponds well with the solar cycle: a surprising observation for such high energy muons. We see no corresponding long-period oscillation in the stratospheric temperature data.Comment: Minor changes and clarifications, matches version accepted at JCAP. 5 pages, 3 figure

    Neutrino Mass from R-parity Violation in Split Supersymmetry

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    We investigate how the observed neutrino data can be accommodated by R-parity violation in Split Supersymmetry. The atmospheric neutrino mass and mixing are explained by the bilinear parameters ξi\xi_i inducing the neutrino-neutralino mixing as in the usual low-energy supersymmetry. Among various one-loop corrections, only the quark-squark exchanging diagrams involving the order-one trilinear couplings λi23,i32\lambda'_{i23,i32} can generate the solar neutrino mass and mixing if the scalar mass mSm_S is not larger than 10910^9 GeV. This scheme requires an unpleasant hierarchical structure of the couplings, e.g., λi23,i321\lambda_{i23,i32}\sim 1, λi33104\lambda'_{i33} \lesssim 10^{-4} and ξi106\xi_i \lesssim 10^{-6}. On the other hand, the model has a distinct collider signature of the lightest neutralino which can decay only to the final states, liW()l_i W^{(*)} and νZ()\nu Z^{(*)}, arising from the bilinear mixing. Thus, the measurement of the ratio; Γ(eW()):Γ(μW()):Γ(τW())\Gamma(e W^{(*)}) : \Gamma(\mu W^{(*)}) : \Gamma(\tau W^{(*)}) would provide a clean probe of the small reactor and large atmospheric neutrino mixing angles as far as the neutralino mass is larger than 62 GeV.Comment: 10 pages, 3 figures, version submitted to JHE
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