arXiv subjects
Publications and source records attributed to C. Timmermans.
The present white paper is submitted as part of the "Snowmass" process to help inform the long-term plans of the United States Department of Energy and the National Science Foundation for high-energy physics. It summarizes the science questions driving the Ultra-High-Energy Cosmic-Ray (UHECR) community and provides recommendations on the strategy to answer them in the next two decades.
The FPGA/NIOS FIR filter based on linear prediction (LP) to suppress radio frequency interference (RFI) has been installed in several radio stations in the Auger Engineering Radio Array (AERA) experiment. AERA observes coherent radio emission from extensive air showers induced by ultra-high-energy cosmic rays to make a detailed study of the development of the electromagnetic part of air showers. Radio signals provide complementary information to that obtained from Auger surface detectors, which are predominantly sensitive to the particle content of an air shower at the surface. The radio signals from air showers are caused by the coherent emission due to geomagnetic and charge-excess processes. These emissions can be observed in the frequency band between 10 - 100 MHz. However, this frequency range is significantly contaminated by narrow-band RFI and other human-made distortions. A FIR filter implemented in the FPGA logic segment of the front-end electronics of a radio sensor significantly improves the signal-to-noise ratio. In this paper we present first results of the efficiency of the adaptive LP FIR filter, deployed in real AERA station on pampas, with a comparison to the currently used IIR notch filter with constant coefficients. The laboratory tests confirms the stability of the filter. Using constant LP coefficients the suppression efficiency remains the same for hours, which corresponds to more than $\bf 10^{12}$ clock cycles. We compared in real conditions several variants of the LP FIR filter with various lengths and various coefficients widths (due to fixed-point representations in the FPGA logic) with the aim to minimize the power consumption for the radio station while keeping sufficient accuracy for noise reduction.
When Charge Coupled Devices are used for scientific observations, their dark signal is a hindrance. In their pristine state, most CCD pixels are `cool'; they exhibit low, quasi uniform dark current, which can be estimated and corrected for. In space, after having been hit by an energetic particle, pixels can turn `hot'. They start delivering excessive, less predictable, dark current. The hot pixels need therefore to be flagged so that subsequent analysis may ignore them. The image data of the PICARD SODISM solar telescope (Meftah et al. 2013) require dark signal correction and hot pixel identification. Its frame transfer E2V 42-80 CCD operates at -7°C. Both image and memory zones thus accumulate dark current during, respectively, integration and readout time. These two components must be separated to estimate the dark signal for any observation. This is the purpose of the Dark Signal Model presented in this paper. The dark signal time series of every pixel is processed by the Unbalanced Haar Technique (Fryzlewicz 2007) in order to timestamp when its dark signal is expected to change. In-between those instants, both components are assumed constant and a robust linear regression vs. integration time provides first estimates and a quality coefficient. The latter serves to assign definitive estimates. Our model is part of the SODISM Level 1 data production scheme. To check its reliability, we verify on dark frames that it leaves a negligible residual bias (5 e-), and generates a small RMS error (25 e- rms). The cool pixel level is found to be 4 e-/pxl/s, in agreement with the predicted value. The emergence rate of hot pixels is investigated too. It legitimates a threshold criterion at 50 e-/pxl/s. The growth rate is found to be 4% of the frame area per year. Aspects of the method (adaptation of the Unbalanced Haar Technique, dedicated robust linear regression) have a generic interest.
Three independent searches for an electric dipole moment (EDM) of the positive and negative muons have been performed, using spin precession data from the muon g-2 storage ring at Brookhaven National Laboratory. Details on the experimental apparatus and the three analyses are presented. Since the individual results on the positive and negative muon, as well as the combined result, d=-0.1(0.9)E-19 e-cm, are all consistent with zero, we set a new muon EDM limit, |d| < 1.9E-19 e-cm (95% C.L.). This represents a factor of 5 improvement over the previous best limit on the muon EDM.
The LORUN/NAHSA system is a pathfinder for hybrid cosmic ray research combined with education and outreach in the field of astro-particle physics. Particle detectors and radio antennae were mainly setup by students and placed on public buildings. After fully digital data acquisition, coincidence detections were selected. Three candidate events confirmed a working prototype, which can be multiplied to extend further particle detector arrays on high schools.