36,512 research outputs found

    Complex mass renormalization in EFT

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    We consider an effective field theory of unstable particles (resonances) using the complex-mass renormalization. As an application we calculate the masses and the widths of the ρ\rho meson and the Roper resonance.Comment: 8 pages, 2 figures; Proceedings of 6th International Workshop on Chiral Dynamics, 6-10 July 2009, Bern, Switzerlan

    Assessing the Effectiveness of a Computer Simulation in Introductory Undergraduate Environments

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    We present studies documenting the effectiveness of using a computer simulation, specifically the Circuit Construction Kit (CCK) developed as part of the Physics Education Technology Project (PhET) [1, 2], in two environments: an interactive college lecture and an inquiry-based laboratory. In the first study conducted in lecture, we compared students viewing CCK to viewing a traditional demonstration during Peer Instruction [3]. Students viewing CCK had a 47% larger relative gain (11% absolute gain) on measures of conceptual understanding compared to traditional demonstrations. These results led us to study the impact of the simulation's explicit representation for visualizing current flow in a laboratory environment, where we removed this feature for a subset of students. Students using CCK with or without the explicit visualization of current performed similarly to each other on common exam questions. Although the majority of students in both groups favored the use of CCK over real circuit equipment, the students who used CCK without the explicit current model favored the simulation more than the other grou

    Time Delay Interferometry for LISA with one arm dysfunctional

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    In order to attain the requisite sensitivity for LISA - a joint space mission of the ESA and NASA- the laser frequency noise must be suppressed below the secondary noises such as the optical path noise, acceleration noise etc. By combining six appropriately time-delayed data streams containing fractional Doppler shifts - a technique called time delay interferometry (TDI) - the laser frequency noise may be adequately suppressed. We consider the general model of LISA where the armlengths vary with time, so that second generation TDI are relevant. However, we must envisage the possibility, that not all the optical links of LISA will be operating at all times, and therefore, we here consider the case of LISA operating with two arms only. As shown earlier in the literature, obtaining even approximate solutions of TDI to the general problem is very difficult. Since here only four optical links are relevant, the algebraic problem simplifies considerably. We are then able to exhibit a large number of solutions (from mathematical point of view an infinite number) and further present an algorithm to generate these solutions

    Evolution from a molecular Rydberg gas to an ultracold plasma in a seeded supersonic expansion of NO

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    We report the spontaneous formation of a plasma from a gas of cold Rydberg molecules. Double-resonant laser excitation promotes nitric oxide, cooled to 1 K in a seeded supersonic molecular beam, to single Rydberg states extending as deep as 80 cm1^{-1} below the lowest ionization threshold. The density of excited molecules in the illuminated volume is as high as 1 x 1013^{13} cm3^{-3}. This population evolves to produce prompt free electrons and a durable cold plasma of electrons and intact NO+^{+} ions.Comment: 4 pages (two column) 3 figures; smaller figure files, corrected typo

    Measuring the mass of the W at the LHC

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    We explore the ability of the Large Hadron Collider to measure the mass of the W boson. We believe that a precision better than ~ 15 MeV could be attained, based on a year of operation at low luminosity (10^(33)cm^(-2)s^(-1)). If this is true, this measurement will be the world's best determination of the W mass. We feel this interesting opportunity warrants investigation in more detail

    Oxygen-isotope effect on the superconducting gap in the cuprate superconductor Y_{1-x}Pr_xBa_2Cu_3O_{7-\delta}

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    The oxygen-isotope (^{16}O/^{18}O) effect (OIE) on the zero-temperature superconducting energy gap \Delta_0 was studied for a series of Y_{1-x}Pr_xBa_2Cu_3O_{7-\delta} samples (0.0\leq x\leq0.45). The OIE on \Delta_0 was found to scale with the one on the superconducting transition temperature. These experimental results are in quantitative agreement with predictions from a polaronic model for cuprate high-temperature superconductors and rule out approaches based on purely electronic mechanisms.Comment: 5 pages, 3 figure