36,512 research outputs found

### Complex mass renormalization in EFT

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 $\rho$ 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

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

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

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 cm$^{-1}$ below the lowest ionization threshold. The density of
excited molecules in the illuminated volume is as high as 1 x 10$^{13}$
cm$^{-3}$. 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

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}

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

- …