Comparison of deep inelastic scattering with photoproduction interactions at HERA

Photon-proton (\gamma p) interactions with~Q^25~GeV^2 are studied at the high energy electron-proton collider HERA. The transverse energy flow and relative rates of large rapidity gap events are compared in the two event samples. The observed similarity between \gamma p and \gamma^* p interactions can be understood in a picture where the photon develops as a hadronic object. The transverse energy density measured in the central region of the collision, at \eta^*=0 in the \gsp centre of mass frame, is compared with data from hadron-hadron interactions as function of the CMS energy of the collision

A Compact Fireball Model of Gamma Ray Bursts

It is proposed that the gamma ray burst photons near the peak of the spectrum at several hundred KeV are produced on very compact scales, where photon production is limited by blackbody effects and/or the requirement of energetic quanta ($E>2m_e c^2$) for efficient further production. The fast variation of order milliseconds in the time profile is then a natural expectation, given the other observed GRB parameters. Analytic calculations are presented to show that the escape of non-thermal, energetic gamma rays can emerge within a second of the thermal photons from a gammasphere of below $10^{12}$ cm. The minimum asymptotic bulk Lorentz factor in this model is found to be of order several hundred if the photosphere is of order $3 \times 10^{11}$ cm and greater for larger or smaller photospheric radii. It is suggested that prompt UHE gamma rays might provide a new constraint on the asymptotic Lorentz factor of the outflow.Comment: To appear in ApJ, revisions requested by the refere

Cosmic ray drift, shock wave acceleration and the anomalous component of cosmic rays

A model of the anomalous component of the quiet-time cosmic ray flux is presented in which ex-interstellar neutral particles are accelerated continuously in the polar regions of the solar-wind termination shock, and then drift into the equatorial regions of the inner heliosphere. The observed solar-cycle variations, radial gradient, and apparent latitude gradient of the anomalous component are a natural consequence of this model

Shading and Smothering of Gamma Ray Bursts

The gamma ray burst (GRB) 980425 is distinctive in that it seems to be associated with supernova (SN) 1998bw, has no X-ray afterglow, and has a single peak light curve and a soft spectrum. The supernova is itself unusual in that its expansion velocity exceeds c/6. We suggest that many of these features can be accounted for with the hypothesis that we observe the GRB along a penumbral line of sight that contains mainly photons that have scattered off ejected baryons. The hypothesis suggests a baryon poor jet (BPJ) existing within a baryon rich outflow. The sharp distinction can be attributed to whether or not the magnetic field lines thread an event horizon. Such a configuration suggests that there will be some non-thermal acceleration of pick-up ex-neutrons within the BPJ. This scenario might produce observable spallation products and neutrinos.Comment: 7 pages, 2 figures, submitted to ApJ

Classical many-body time crystals

Discrete time crystals are a many-body state of matter where the extensive system's dynamics are slower than the forces acting on it. Nowadays, there is a growing debate regarding the specific properties required to demonstrate such a many-body state, alongside several experimental realizations. In this work, we provide a simple and pedagogical framework by which to obtain many-body time crystals using parametrically coupled resonators. In our analysis, we use classical period-doubling bifurcation theory and present a clear distinction between single-mode time-translation symmetry breaking and a situation where an extensive number of degrees of freedom undergo the transition. We experimentally demonstrate this paradigm using coupled mechanical oscillators, thus providing a clear route for time crystals realizations in real materials.Comment: 23 pages, 5 figures, comments are welcom

Electron Spin Resonance at the Level of 10000 Spins Using Low Impedance Superconducting Resonators

We report on electron spin resonance (ESR) measurements of phosphorus donors localized in a 200 square micron area below the inductive wire of a lumped element superconducting resonator. By combining quantum limited parametric amplification with a low impedance microwave resonator design we are able to detect around 20000 spins with a signal-to-noise ratio (SNR) of 1 in a single shot. The 150 Hz coupling strength between the resonator field and individual spins is significantly larger than the 1 - 10 Hz coupling rates obtained with typical coplanar waveguide resonator designs. Due to the larger coupling rate, we find that spin relaxation is dominated by radiative decay into the resonator and dependent upon the spin-resonator detuning, as predicted by Purcell

Asymptotic channels and gauge transformations of the time-dependent Dirac equation for extremely relativistic heavy-ion collisions

We discuss the two-center, time-dependent Dirac equation describing the dynamics of an electron during a peripheral, relativistic heavy-ion collision at extreme energies. We derive a factored form, which is exact in the high-energy limit, for the asymptotic channel solutions of the Dirac equation, and elucidate their close connection with gauge transformations which transform the dynamics into a representation in which the interaction between the electron and a distant ion is of short range. We describe the implications of this relationship for solving the time-dependent Dirac equation for extremely relativistic collisions.Comment: 12 pages, RevTeX, 2 figures, submitted to PR