ArgoNeuT: A Liquid Argon Time Projection Chamber Test in the NuMI Beamline

Liquid Argon Time Projection Chamber detectors are ideally suited for studying neutrino interactions and probing the parameters that characterize neutrino oscillations. The ability to drift ionization particles over long distances in purified argon and to trigger on abundant scintillation light allows for excellent particle identification and triggering capability. In these proceedings the details of the ArgoNeuT test-beam project will be presented after a brief introduction to the detector technique. ArgoNeuT is a 175 liter detector exposed to Fermilab's NuMI neutrino beamline. The first neutrino interactions observed in ArgoNeuT will be presented, along with discussion of the various physics analyses to be performed on this data sample.Comment: To be published in the proceedings of DPF-2009, Detroit, MI, July 2009, eConf C09072

Random Graph Models with Hidden Color

We demonstrate how to generalize two of the most well-known random graph models, the classic random graph, and random graphs with a given degree distribution, by the introduction of hidden variables in the form of extra degrees of freedom, color, applied to vertices or stubs (half-edges). The color is assumed unobservable, but is allowed to affect edge probabilities. This serves as a convenient method to define very general classes of models within a common unifying formalism, and allowing for a non-trivial edge correlation structure.Comment: 17 pages, 2 figures; contrib. to the Workshop on Random Geometry in Krakow, May 200

Radio and X-ray Observations of the Type Ic SN 2007gr Reveal an Ordinary, Non-relativistic Explosion

We present extensive radio and X-ray observations of the nearby Type Ic SN 2007gr in NGC 1058 obtained with the Very Large Array and the Chandra X-ray Observatory and spanning 5 to 150 days after explosion. Through our detailed modeling of these data, we estimate the properties of the blastwave and the circumstellar environment. We find evidence for a freely-expanding and non-relativistic explosion with an average blastwave velocity, v~0.2c, and a total internal energy for the radio emitting material of E ~ 2 x 10^46 erg assuming equipartition of energy between electrons and magnetic fields (epsilon_e=epsilon_B=0.1). The temporal and spectral evolution of the radio emission points to a stellar wind-blown environment shaped by a steady progenitor mass loss rate of Mdot ~ 6 x 10^-7 solar masses per year (wind velocity, v_w=10^3 km/s). These parameters are fully consistent with those inferred for other SNe Ibc and are in line with the expectations for an ordinary, homologous SN explosion. Our results are at odds with those of Paragi et al. (2010) who recently reported evidence for a relativistic blastwave in SN 2007gr based on their claim that the radio emission was resolved away in a low signal-to-noise Very Long Baseline Interferometry (VLBI) observation. Here we show that the exotic physical scenarios required to explain the claimed relativistic velocity -- extreme departures from equipartition and/or a highly collimated outflow -- are excluded by our detailed Very Large Array radio observations. Moreover, we present an independent analysis of the VLBI data and propose that a modest loss of phase coherence provides a more natural explanation for the apparent flux density loss which is evident on both short and long baselines. We conclude that SN 2007gr is an ordinary Type Ibc supernova.Comment: 14 pages, 6 figures, submitted to Ap

The Diagonalisation of the Lund Fragmentation Model I

We will in this note show that it is possible to diagonalise the Lund Fragmentation Model. We show that the basic original result, the Lund Area law, can be factorised into a product of transition operators, each describing the production of a single particle and the two adjacent breakup points (vertex positions) of the string field. The transition operator has a discrete spectrum of (orthonormal) eigenfunctions, describing the vertex positions (which in a dual way corresponds to the momentum transfers between the produced particles) and discrete eigenvalues, which only depend upon the particle produced. The eigenfunctions turn out to be the well-known two- dimensional harmonic oscillator functions and the eigenvalues are the analytic continuations of these functions to time-like values (corresponding to the particle mass). In this way all observables in the model can be expressed in terms of analytical formulas. In this note only the 1+1-dimensional version of the model is treated but we end with remarks on the extensions to gluonic radiation, transverse momentum generation etc, to be performed in future papers.Comment: 15 pages, 7 figure

Constraints on the Bulk Lorentz Factor of GRB 990123

GRB 990123 was a long, complex gamma-ray burst accompanied by an extremely bright optical flash. We present the collective constraints on the bulk Lorentz factor for this burst based on estimates from burst kinematics, synchrotron spectral decay, prompt radio flash observations, and prompt emission pulse width. Combination of these constraints leads to an average bulk Lorentz factor for GRB 990123 of Gamma_0=1000 +/- 100 which implies a baryon loading of M_jet=8 (+17/-2) x 10^-8 Msolar. We find these constraints to be consistent with the speculation that the optical light is emission from the reverse shock component of the external shock. In addition, we find the implied value of M_jet to be in accordance with theoretical estimates: the baryonic loading is sufficiently small to allow acceleration of the outflow to Gamma > 100.Comment: 4 pages, 2 postscript figures, to appear in "Gamma-Ray Burst and Afterglow Astronomy 2001", Woods Hole; 5-9 Nov, 200