arXiv subjects

S. Stahl

Publications and source records attributed to S. Stahl.

9 recordsLinked to original sources

arXiv2022

Citizen Science Astronomy with a Network of Small Telescope: The Launch and Deployment of JWST

We present a coordinated campaign of observations to monitor the brightness of the James Webb Space Telescope (JWST) as it travels toward the second Earth-Sun Lagrange point and unfolds using the network ofUnistellar digital telescopes. Those observations collected by citizen astronomers across the world allowed us to detect specific phases such as the separation from the booster, glare due to a change of orientation after a maneuver, the unfurling of the sunshield, and deployment of the primary mirror. After deployment of the sunshield on January 6 2022, the 6-h lightcurve has a significant amplitude and shows small variations due to the artificial rotation of the space telescope during commissionning. These variations could be due to the deployment of the primary mirror or some changes in orientation of the space telescope. This work illustrates the power of a worldwide array of small telescopes, operated by citizen astronomers, to conduct large scientific campaigns over a long timeframe. In the future, our network and others will continue to monitor JWST to detect potential degradations to the space environment by comparing the evolution of the lightcurve.

astro-ph.IM↗

arXiv2019

A comprehensive real-time analysis model at the LHCb experiment

An evolved real-time data processing strategy is proposed for high-energy physics experiments, and its implementation at the LHCb experiment is presented. The reduced event model allows not only the signal candidate firing the trigger to be persisted, as previously available, but also an arbitrary set of other reconstructed or raw objects from the event. This allows for higher trigger rates for a given output data bandwidth, when compared to the traditional model of saving the full raw detector data for each trigger, whilst accommodating inclusive triggers and preserving data mining capabilities. The gains in physics reach and savings in computing resources already made possible by the model are discussed, along with the prospects of employing it more widely for Run 3 of the Large Hadron Collider.

hep-ex↗

arXiv2019

Novel method for measuring charm-mixing parameters using multibody decays

We propose a novel method to measure flavor-oscillations and charge-parity (CP) violation in charm mixing. The approach uses multibody charm decays, such as $D^0\to K_S^0π^+π^-$, and avoids the need for a fit of the decay amplitudes while suppressing biases due to nonuniform signal-reconstruction efficiencies as functions of phase space and decay time. Data are partitioned in decay-time and Dalitz-plot regions (bins). The Dalitz-plot bins are symmetric with respect to the principal bisector and chosen to ensure nearly constant values of the strong-interaction phases in each. The ratios of signal yields observed in each symmetric bin pair are fit as functions of decay time, using independent auxiliary measurements of the strong-interaction phases as constraints, to determine the relevant physics parameters. Simulation shows that this approach improves the sensitivity to the normalized charm-eigenstate mass difference by 35% with respect to existing model-independent methods. In addition, we introduce a parametrization of oscillation and CP-violation effects in charm mixing that has attractive statistical properties and may find wider applicability.

hep-ex↗

arXiv2016

Tesla : an application for real-time data analysis in High Energy Physics

Upgrades to the LHCb computing infrastructure in the first long shutdown of the LHC have allowed for high quality decay information to be calculated by the software trigger making a separate offline event reconstruction unnecessary. Furthermore, the storage space of the triggered candidate is an order of magnitude smaller than the entire raw event that would otherwise need to be persisted. Tesla, following the LHCb renowned physicist naming convention, is an application designed to process the information calculated by the trigger, with the resulting output used to directly perform physics measurements.

physics.ins-det↗

arXiv2014

Resistive and sympathetic cooling of highly-charged-ion clouds in a Penning trap

We present measurements of resistive and sympathetic cooling of ion clouds confined in a Penning trap. For resistive cooling of a cloud consisting of one ion species, we observe a significant deviation from exponential cooling behavior which is explained by an energy-transfer model. The observed sympathetic cooling of simultaneously confined ion species shows a quadratic dependence on the ion charge state and is hence in agreement with expectations from the physics of dilute non-neutral plasmas.

physics.atom-ph↗

arXiv2013

The LHCb Trigger and its Performance in 2011

This paper presents the design of the LHCb trigger and its performance on data taken at the LHC in 2011. A principal goal of LHCb is to perform flavour physics measurements, and the trigger is designed to distinguish charm and beauty decays from the light quark background. Using a combination of lepton identification and measurements of the particles' transverse momenta the trigger selects particles originating from charm and beauty hadrons, which typically fly a finite distance before decaying. The trigger reduces the roughly 11\,MHz of bunch-bunch crossings that contain at least one inelastic $pp$ interaction to 3\,kHz. This reduction takes place in two stages; the first stage is implemented in hardware and the second stage is a software application that runs on a large computer farm. A data-driven method is used to evaluate the performance of the trigger on several charm and beauty decay modes.

hep-ex↗

arXiv2009

A broad-Band FT-ICR Penning TRap System for KATRIN

The KArlsruhe TRItium Neutrino experiment KATRIN aims at improving the upper limit of the mass of the electron antineutrino to about 0.2 eV (90% c.l.) by investigating the beta-decay of tritium gas molecules. The experiment is currently under construction to start first data taking in 2012. One source of systematic uncertainties in the KATRIN experiment is the formation of ion clusters when tritium decays and decay products interact with residual tritium molecules. It is essential to monitor the abundances of these clusters since they have different final state energies than tritium ions. For this purpose, a prototype of a cylindrical Penning trap has been constructed and tested at the Max-Planck-Institute for Nuclear Physics in Heidelberg, which will be installed in the KATRIN beam line. This system employs the technique of Fourier-Transform Ion-Cyclotron-Resonance in order to measure the abundances of the different stored ion species.

physics.ins-det↗

arXiv2008

Experimental and theoretical challenges for the trapped electron quantum computer

We discuss quantum information processing with trapped electrons. After recalling the operation principle of planar Penning traps we sketch the experimental conditions to load, cool and detect single electrons. Here we present a detailed investigation of a scalable scheme including feasibility studies and the analysis of all important elements, relevant for the experimental stage. On the theoretical side, we discuss different methods to couple electron qubits. We estimate the relevant qubit coherence times and draw implications for the experimental setting. A critical assessment of quantum information processing with trapped electrons is concluding the article.

quant-ph↗

arXiv2007

Magnetic field stabilization for high-accuracy mass measurements on exotic nuclides

The magnetic-field stability of a mass spectrometer plays a crucial role in precision mass measurements. In the case of mass determination of short-lived nuclides with a Penning trap, major causes of instabilities are temperature fluctuations in the vicinity of the trap and pressure fluctuations in the liquid helium cryostat of the superconducting magnet. Thus systems for the temperature and pressure stabilization of the Penning trap mass spectrometer ISOLTRAP at the ISOLDE facility at CERN have been installed. A reduction of the fluctuations by at least one order of magnitude downto dT=+/-5mK and dp=+/-50mtorr has been achieved, which corresponds to a relative frequency change of 2.7x10^{-9} and 1.5x10^{-10}, respectively. With this stabilization the frequency determination with the Penning trap only shows a linear temporal drift over several hours on the 10 ppb level due to the finite resistance of the superconducting magnet coils.

physics.ins-det↗