Light Gravitinos at Colliders and Implications for Cosmology

Light gravitinos, with mass in the eV to MeV range, are well-motivated in particle physics, but their status as dark-matter candidates is muddled by early-Universe uncertainties. We investigate how upcoming data from colliders may clarify this picture. Light gravitinos are produced primarily in the decays of the next-to-lightest supersymmetric particle, resulting in spectacular signals, including di-photons, delayed and non-pointing photons, kinked charged tracks, and heavy metastable charged particles. We find that the Tevatron with 20/fb and the 7 TeV LHC with 1/fb may both see evidence for hundreds of light-gravitino events. Remarkably, this collider data is also well suited to distinguish between currently viable light-gravitino scenarios, with striking implications for structure formation, inflation, and other early-Universe cosmology.Comment: 12 pages, 6 figures. To be submitted to Phys. Rev. D

Geometric phases and Wannier functions of Bloch electrons in 1-dimension

We present a formal expression for Wannier functions of composite bands of 1-D Bloch electrons in terms of parallel-transported Bloch functions and their non-Abelian geometric phases. Spatial decay properties of these Wannier functions are studied in the case of simple bands of 1-D model insulator and metal. Within first-principles density functional theory, we illustrate the formalism through the construction of Wannier functions of polyethylene and polyacetylene.Comment: 4 pages, 4 figure

Bimodal Coherence in Dense Self-Interacting Neutrino Gases

Analytical solutions are obtained to the nonlinear equations describing neutrino oscillations when explicit neutrino-antineutrino asymmetries are present. Such a system occurs in the early Universe if neutrinos have a non-zero chemical potential. Solutions to the equations lead to a new type of coherent behavior governed by two modes. These bimodal solutions provide new insights into dense neutrino gases and into neutrino oscillations in the early Universe, thereby allowing one to surmise the flavor behavior of neutrinos with a non-zero chemical potential.Comment: 21 pages in Latex, 11 figures packaged in one Postscript file. Figures also obtainable as 20 gif files at http://www.sci.ccny.cuny.edu/~ssamuel/bimodalfigs.html Revision on 4/19/96 was to pack the figures more sensibly. This paper is to appear in a May issue of Phys. Rev.

Renormalization-Scale Invariance, Minimal Sensitivity, and the Inclusive Hadronic Decays of a 115 GeV Higgs Particle

Known perturbative expressions for the decay rates of 115 GeV Higgs particle into either two gluons or a $b\bar{b}$ pair are shown to exhibit renormalization-scale-($\mu$)-dependence that is largely removed via renormalization-group/Pade-approximant estimates of these rates' next order contributions. The extrema in $\mu$ characterizing both rates, as determined from fully-known orders of perturbation theory, are very nearly equal to corresponding $\mu$-insensitive rates obtained via estimation of their next order contributions, consistent with "minimal-sensitivity" expectations.Comment: 12 pages, 3 figures, LaTe

SmartState: A Protocol-driven Human Interface

Since the inception of human research studies, researchers must often interact with participants on a set schedule to collect data. Researchers manually perform many interactions, leading to considerable time and financial expenses. Usually, user-provided data collection consists of surveys administered via telephone or email. These methods are tedious for the survey administrators, which could cause fatigue and potentially lead to collection mistakes. This project leverages recent advancements in automatic speech recognition, speech-to-text, natural language understanding (NLU), and finite-state machines to automate research protocols. This generalized application is fully customizable and irrespective of any research study. New research protocols can be quickly created based on these parameters once envisioned. Thus, we present SmartState, a fully-customizable, state-driven protocol manager combined with supporting AI components to autonomously manage user data and intelligently determine users' intentions through chat and end-device interactions.Comment: 8 pages, 8 figure

Neutrino Oscillations in the Early Universe with Nonequilibrium Neutrino Distributions

Around one second after the big bang, neutrino decoupling and $e^+$-$e^-$ annihilation distort the Fermi-Dirac spectrum of neutrino energies. Assuming neutrinos have masses and can mix, we compute the distortions using nonequilibrium thermodynamics and the Boltzmann equation. The flavor behavior of neutrinos is studied during and following the generation of the distortion.Comment: accepted for publication in Physical Review

An Inverse Scattering Transform for the Lattice Potential KdV Equation

The lattice potential Korteweg-de Vries equation (LKdV) is a partial difference equation in two independent variables, which possesses many properties that are analogous to those of the celebrated Korteweg-de Vries equation. These include discrete soliton solutions, Backlund transformations and an associated linear problem, called a Lax pair, for which it provides the compatibility condition. In this paper, we solve the initial value problem for the LKdV equation through a discrete implementation of the inverse scattering transform method applied to the Lax pair. The initial value used for the LKdV equation is assumed to be real and decaying to zero as the absolute value of the discrete spatial variable approaches large values. An interesting feature of our approach is the solution of a discrete Gel'fand-Levitan equation. Moreover, we provide a complete characterization of reflectionless potentials and show that this leads to the Cauchy matrix form of N-soliton solutions

Geometric phase in open systems

We calculate the geometric phase associated to the evolution of a system subjected to decoherence through a quantum-jump approach. The method is general and can be applied to many different physical systems. As examples, two main source of decoherence are considered: dephasing and spontaneous decay. We show that the geometric phase is completely insensitive to the former, i.e. it is independent of the number of jumps determined by the dephasing operator.Comment: 4 pages, 2 figures, RevTe

The quantum mechanical geometric phase of a particle in a resonant vibrating cavity

We study the general-setting quantum geometric phase acquired by a particle in a vibrating cavity. Solving the two-level theory with the rotating-wave approximation and the SU(2) method, we obtain analytic formulae that give excellent descriptions of the geometric phase, energy, and wavefunction of the resonating system. In particular, we observe a sudden $\pi$-jump in the geometric phase when the system is in resonance. We found similar behaviors in the geometric phase of a spin-1/2 particle in a rotating magnetic field, for which we developed a geometrical model to help visualize its evolution.Comment: 15pages,6figure

Modeling power corrections to the Bjorken sum rule for the neutrino structure function F_1

Direct measurements of the the structure functions F_1^{nu p} and F_1^{nu n} at a neutrino factory would allow for an accurate extraction of alpha_s from the Q^2-dependence of the Bjorken sum rule, complementing that based on the Gross-Llewellyn-Smith sum rule for F_3. We estimate the power (1/Q^2-) corrections to the Bjorken sum rule in the instanton vacuum model. For the reduced matrix element of the flavor-nonsinglet twist-4 operator ubar_g_Gdual_gamma_gamma5_u - (u -> d) we obtain a value of 0.18 GeV^2, in good agreement with the QCD sum rule calculations of Braun and Kolesnichenko. Our result allows to reduce the theoretical error in the determination of alpha_s.Comment: 3 pages, 1 figure, uses iopart.cls. Proceedings of the 4th NuFact'02 Workshop "Neutrino Factories based on Muon Storage Rings", Imperial College, London, July 1-6, 200