Testing Supersymmetry at the Next Linear Collider

If new particles are discovered, it will be important to determine if they are the supersymmetric partners of standard model bosons and fermions. Supersymmetry predicts relations among the couplings and masses of these particles. We discuss the prospects for testing these relations at a future $e^+e^-$ linear collider with measurements that exploit the availability of polarized beams.Comment: Talk presented at DPF'94, Albuquerque, New Mexico, Aug 2-6, 1994, 6 pages, Latex with world_sci.sty, 3 figures available upon request, SLAC-PUB-6662. (text with encapsulated figures available in ps form by anonymous ftp from preprint.slac.stanford.edu, directory pub/preprints/hep-ph/9409

Non-WIMP Candidates

Non-WIMP dark matter candidates include particles motivated by minimality, candidates motivated by experimental anomalies, and exotic possibilities motivated primarily by the desire of clever iconoclasts to highlight how truly ignorant we are about the nature of dark matter. In this review, I discuss candidates that are not WIMPs, but nevertheless share the same theoretical motivations as WIMPs and also naturally have the correct relic density. There are two classes: superWIMP dark matter, where the desired relic density is inherited through decays, and WIMPless dark matter, where the dark matter's mass and couplings scale together to maintain the desired thermal relic density.Comment: 20 pages, published as Chapter 10, pp. 190-204, in Particle Dark Matter: Observations, Models and Searches, edited by Gianfranco Bertone (Cambridge University Press, 2010), available at http://cambridge.org/us/catalogue/catalogue.asp?isbn=978052176368

Naturalness and the Status of Supersymmetry

For decades, the unnaturalness of the weak scale has been the dominant problem motivating new particle physics, and weak-scale supersymmetry has been the dominant proposed solution. This paradigm is now being challenged by a wealth of experimental data. In this review, we begin by recalling the theoretical motivations for weak-scale supersymmetry, including the gauge hierarchy problem, grand unification, and WIMP dark matter, and their implications for superpartner masses. These are set against the leading constraints on supersymmetry from collider searches, the Higgs boson mass, and low-energy constraints on flavor and CP violation. We then critically examine attempts to quantify naturalness in supersymmetry, stressing the many subjective choices that impact the results both quantitatively and qualitatively. Finally, we survey various proposals for natural supersymmetric models, including effective supersymmetry, focus point supersymmetry, compressed supersymmetry, and R-parity-violating supersymmetry, and summarize their key features, current status, and implications for future experiments.Comment: 38 pages, to appear in Annual Review of Nuclear and Particle Science; v2: fixed typos, updated Higgs results, added references and a parable, published versio

ILC Cosmology

Recent breakthroughs in cosmology pose questions that require particle physics answers. I review the problems of dark matter, baryogenesis, and dark energy and discuss how particle colliders, particularly the International Linear Collider, may advance our understanding of the contents and evolution of the Universe.Comment: 18 pages, Plenary Colloquium presented at the 2005 International Linear Collider Workshop, Stanford, California, USA, 18-22 March 200

Mitigation of dynamical instabilities in laser arrays via non-Hermitian coupling

Arrays of coupled semiconductor lasers are systems possessing complex dynamical behavior that are of major interest in photonics and laser science. Dynamical instabilities, arising from supermode competition and slow carrier dynamics, are known to prevent stable phase locking in a wide range of parameter space, requiring special methods to realize stable laser operation. Inspired by recent concepts of parity-time ($\mathcal{PT}$) and non-Hermitian photonics, in this work we consider non-Hermitian coupling engineering in laser arrays in a ring geometry and show, both analytically and numerically, that non-Hermitian coupling can help to mitigate the onset of dynamical laser instabilities. In particular, we consider in details two kinds of nearest-neighbor non-Hermitian couplings: symmetric but complex mode coupling (type-I non-Hermitian coupling) and asymmetric mode coupling (type-II non-Hermitian coupling). Suppression of dynamical instabilities can be realized in both coupling schemes, resulting in stable phase-locking laser emission with the lasers emitting in phase (for type-I coupling) or with $\pi/2$ phase gradient (for type-II coupling), resulting in a vortex far-field beam. In type-II non-Hermitian coupling, chirality induced by asymmetric mode coupling enables laser phase locking even in presence of moderate disorder in the resonance frequencies of the lasers.Comment: revised version, changed title, added one figure and some reference

Determinants of local responsiveness of FMNCS in mainland China

Recent regulations, associated with China’s accession to the World Trade Organisation (WTO), specifically Decree 113 and Decree 114, have largely changed the situation for foreign multinational construction companies (FMNCs) operating in mainland China. A field investigation has identified that local responsiveness is critical for FMNCs to survive and develop in the complicated and uncertain Chinese construction industry. Government policy, China-specific construction industrial factors and increasing competition intensity imposed by local competitors are recognized as the major determinants driving local responsiveness of FMNCs. This study has also examined that localisation of internal resources, establishment of local networks and cooperation or strategic alliances with local contractors and design institutes are the key local adaptation strategies for FMNCs operating in mainland China

Tevatron Signatures of Long-lived Charged Sleptons in Gauge-Mediated Supersymmetry Breaking Models

In supersymmetric models with gauge-mediated supersymmetry breaking, charged sleptons are the next lightest supersymmetric particles and decay outside the detector for large regions of parameter space. In such scenarios, supersymmetry may be discovered by searches for a number of novel signals, including highly ionizing tracks from long-lived slow charged particles and excesses of multi-lepton signals. We consider this scenario in detail and find that the currently available Tevatron data probes regions of parameter space beyond the kinematic reach of LEP II. Future Tevatron runs with integrated luminosities of 2, 10, and 30 fb-1 probe right-handed slepton masses of 110, 180, and 230 GeV and Wino masses of 310, 370, and 420 GeV, respectively, greatly extending current search limits.Comment: Revtex, 30 pages, 15 figures, minor revisions to conform to published versio

MSSM4G: Reviving Bino Dark Matter with Vector-like 4th Generation Particles

We supplement the minimal supersymmetric standard model (MSSM) with vector-like copies of standard model particles. Such 4th generation particles can raise the Higgs boson mass to the observed value without requiring very heavy superpartners, improving naturalness and the prospects for discovering supersymmetry at the LHC. Here we show that these new particles are also motivated cosmologically: in the MSSM, pure Bino dark matter typically overcloses the Universe, but 4th generation particles open up new annihilation channels, allowing Binos to have the correct thermal relic density without resonances or co-annihilation. We show that this can be done in a sizable region of parameter space while preserving gauge coupling unification and satisfying constraints from collider, Higgs, precision electroweak, and flavor physics.Comment: 16 pages, 3 figure

Supernatural Supersymmetry: Phenomenological Implications of Anomaly-Mediated Supersymmetry Breaking

We discuss the phenomenology of supersymmetric models in which supersymmetry breaking terms are induced by the super-Weyl anomaly. Such a scenario is envisioned to arise when supersymmetry breaking takes place in another world, i.e., on another brane. We review the anomaly-mediated framework and study in detail the minimal anomaly-mediated model parametrized by only 3+1 parameters: M_aux, m_0, \tan\beta, and sign(\mu). The renormalization group equations exhibit a novel "focus point" (as opposed to fixed point) behavior, which allows squark and slepton masses to be far above their usual naturalness bounds. We present the superparticle spectrum and highlight several implications for high energy colliders. Three lightest supersymmetric particle (LSP) candidates exist: the Wino, the stau, and the tau sneutrino. For the Wino LSP scenario, light Wino triplets with the smallest possible mass splittings are preferred; such Winos are within reach of Run II Tevatron searches. Finally, we study a variety of sensitive low energy probes, including b -> s gamma, the anomalous magnetic moment of the muon, and the electric dipole moments of the electron and neutron.Comment: 32 pages, 17 figure