The OLYMPUS Collaboration reports on a precision measurement of the positron-proton to electron-proton elastic cross section ratio, R_{2γ}, a direct measure of the contribution of hard two-photon ...exchange to the elastic cross section. In the OLYMPUS measurement, 2.01 GeV electron and positron beams were directed through a hydrogen gas target internal to the DORIS storage ring at DESY. A toroidal magnetic spectrometer instrumented with drift chambers and time-of-flight scintillators detected elastically scattered leptons in coincidence with recoiling protons over a scattering angle range of ≈20° to 80°. The relative luminosity between the two beam species was monitored using tracking telescopes of interleaved gas electron multiplier and multiwire proportional chamber detectors at 12°, as well as symmetric Møller or Bhabha calorimeters at 1.29°. A total integrated luminosity of 4.5 fb^{-1} was collected. In the extraction of R_{2γ}, radiative effects were taken into account using a Monte Carlo generator to simulate the convolutions of internal bremsstrahlung with experiment-specific conditions such as detector acceptance and reconstruction efficiency. The resulting values of R_{2γ}, presented here for a wide range of virtual photon polarization 0.456<ε<0.978, are smaller than some hadronic two-photon exchange calculations predict, but are in reasonable agreement with a subtracted dispersion model and a phenomenological fit to the form factor data.
We report the first measurement of the average of the electron-proton and positron-proton elastic scattering cross sections. This lepton charge-averaged cross section is insensitive to the leading ...effects of hard two-photon exchange, giving more robust access to the proton's electromagnetic form factors. The cross section was extracted from data taken by the OLYMPUS experiment at DESY, in which alternating stored electron and positron beams were scattered from a windowless gaseous hydrogen target. Elastic scattering events were identified from the coincident detection of the scattered lepton and recoil proton in a large-acceptance toroidal spectrometer. The luminosity was determined from the rates of Møller, Bhabha, and elastic scattering in forward electromagnetic calorimeters. The data provide some selectivity between existing form factor global fits and will provide valuable constraints to future fits.
Design and performance of a lead fluoride detector as a luminosity monitor Pérez Benito, R.; Khaneft, D.; O'Connor, C. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2016, Letnik:
826, Številka:
C
Journal Article
Recenzirano
Odprti dostop
Precise luminosity measurements for the OLYMPUS two-photon exchange experiment at DESY were performed by counting scattering events with alternating beams of electrons and positrons incident on ...atomic electrons in a gaseous hydrogen target. Final products of Møller, Bhabha, and pair annihilation interactions were observed using a pair of lead fluoride Cherenkov calorimeters with custom housings and electronics, adapted from a system used by the A4 parity violation experiment at MAMI. This paper describes the design, calibration, and operation of these detectors. An explanation of the Monte Carlo methods used to simulate the physical processes involved both at the scattering vertices and in the detector apparatus is also included.
The OLYMPUS experiment Milner, R.; Hasell, D.K.; Kohl, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
03/2014, Letnik:
741
Journal Article
Recenzirano
Odprti dostop
The OLYMPUS experiment was designed to measure the ratio between the positron–proton and electron–proton elastic scattering cross-sections, with the goal of determining the contribution of two-photon ...exchange to the elastic cross-section. Two-photon exchange might resolve the discrepancy between measurements of the proton form factor ratio, μpGEp/GMp, made using polarization techniques and those made in unpolarized experiments. OLYMPUS operated on the DORIS storage ring at DESY, alternating between 2.01GeV electron and positron beams incident on an internal hydrogen gas target. The experiment used a toroidal magnetic spectrometer instrumented with drift chambers and time-of-flight detectors to measure rates for elastic scattering over the polar angular range of approximately 25°–75°. Symmetric Møller/Bhabha calorimeters at 1.29° and telescopes of GEM and MWPC detectors at 12° served as luminosity monitors. A total luminosity of approximately 4.5fb−1 was collected over two running periods in 2012. This paper provides details on the accelerator, target, detectors, and operation of the experiment.
•ITER Tokamak fusion reactor operation.•Diagnostics and monitoring of Tokamak systems.•Hydraulic, thermal, structural & electromagnetic identification, inverse engineering.
Several thousands of ...sensors will be fitted in the main Tokamak Systems to oversee the behavior of the ITER machine. This engineering instrumentation will measure key parameters related to availability, prediction of failures, as well as schedule and needs related to their maintenance. However, despite the large amount of instrumentation envisaged, the Tokamak operator needs more data than those solely based on direct measurements, as it is not feasible to install sensors in every single location expected to be critical during the different operational modes.
The “Tokamak Systems Monitor (TSM)” is a software suite specifically designed aiming at overcoming these limitations. By making use of the available measurements, it will provide an integrated view of the overall hydraulic, thermal, structural and electromagnetic response of the main Tokamak Systems (Vacuum Vessel, Magnets, Blankets, Divertor, Cryostat, Thermal Shields and the Diagnostics Port Plugs). Near real time processing shall allow an online evaluation of the Tokamak Systems status with only a few seconds latency. Offline data assessment shall expand the online calculation capabilities for in-depth detailed analysis after the plasma discharges. Sensor measurements can be used directly (e.g., the calculation of electromagnetic loads from measured currents and magnetic fields) or indirectly, through the resolution of ill-posed, inverse problems. The operator will receive all this information within the control room for managing scarce resources, operational limits, and decision-making. Eventually, the TSM will contribute to optimize the trade-off between maximal performance and equipment lifetime.
This paper attempts to summarize the initial feasibility and concept design efforts towards the development, validation and practical implementation of reconstruction and Tokamak simulation algorithms.
Despite the wealth of evidence suggesting a protective role of lifestyle factors on Huntington's disease (HD) onset and progression, their association with mortality has not been extensively studied. ...The aim of this study was to examine whether lifestyle factors such as caffeine and alcohol consumption, smoking, physical activity level, and Mediterranean diet (MeDi) adherence are associated with mortality among a Spanish cohort of patients with HD with a 9-year surveillance period.
This national study was performed using a nested, observational, longitudinal design. We included subjects diagnosed with HD who participated in the European Huntington's disease network and Enrol-HD studies. Date of death and baseline lifestyle factor information, demographics, disease severity assessed by the Unified Huntington's Disease Rating Scale (UHDRS), Problem Behaviours Assessment, total functional capacity (TFC) scores, and comorbidities were collected. Adjusted Cox proportional hazards models were conducted to determine the association of lifestyle factors with mortality.
We included 87 patients (52 females) with a mean age of 48.62±14.43 years and CAG repeats of 43.76±5.92. Sixteen deaths were recorded. After correcting for multiple comparisons, deceased patients had higher UHDRS scores at baseline and lower caffeine consumption than live patients. In multivariate Cox regression models, after adjusting for age, CAG repeats, and TFC, mortality risk was associated with lower caffeine consumption (HR 0.13, 95% CI 0.04, 0.45).
This national-based study suggests that increased caffeine consumption is associated with decreased HD mortality. Our results may help guide clinicians in counselling lifestyle practices for decreasing mortality in HD.
A pesar de la evidencia que existe sobre la importancia de los factores de estilo de vida con el inicio y la progresión de la enfermedad de Huntington (EH), su asociación con la mortalidad no ha sido ampliamente estudiada. El objetivo de este estudio es estudiar la asociación de factores de estilo de vida como el consumo de cafeína y alcohol, el tabaquismo, el nivel de actividad física y la adherencia a la dieta mediterránea, con la mortalidad en una cohorte española de pacientes con EH con un periodo de seguimiento nueve años.
Este estudio nacional, observacional, longitudinal se realizó mediante un diseño anidado. Se incluyeron sujetos diagnosticados con EH, participantes en la red Enroll europea de la enfermedad de Huntington. Se recogieron la fecha de fallecimiento y la información basal sobre los factores de estilo de vida, datos sociodemográficos, la gravedad de la EH con la Escala Unificada de la EH (UHDRS), evaluación de problemas conductuales (PBA), Capacidad Funcional Total (TFC) y las comorbilidades. Se realizaron análisis comparativos y de supervivencia con modelos de regresión de Cox ajustados.
Se incluyeron 87 pacientes con EH (52 mujeres) con una edad media de 48,62±14,43 años, y un número medio de repeticiones CAG de 43,76±5,92. Se registraron 16 fallecimientos. En análisis comparativos ajustados por comparaciones múltiples, los pacientes fallecidos tenían puntuaciones basales UHDRS mayores, y un consumo menor de cafeína comparado con los pacientes vivos. En los modelos multivariantes de regresión de Cox, tras ajustar por edad, repeticiones CAG y TFC, el riesgo de mortalidad se asoció con un menor consumo de cafeína (HR 0,13; IC 95%: 0,04; 0,45).
Este estudio nacional sugiere que un mayor consumo de cafeína se asocia con una menor mortalidad en la EH. Nuestros resultados pueden ayudar a orientar a los profesionales sanitarios en el asesoramiento de una mejora de prácticas de estilo de vida para la EH asociadas con menor mortalidad.
The PANDA experiment at the new FAIR facility will cover a broad experimental programme in hadron structure and spectroscopy. As a multipurpose detector, the PANDA spectrometer needs to ensure almost ...4π coverage of the scattering solid angle, full and accurate multiple-particle event reconstruction and very good particle identification capabilities. The electromagnetic calorimeter (EMC) will be a key item for many of these aspects. Particle energies ranging from some MeVs to several GeVs have to be measured with a relative resolution of 1% ⊕ 2%/ E/GeV . It will be a homogeneous calorimeter made of PbWO4 crystals and will be operated at -25°C, in order to improve the scintillation light yield. With the exception of the very forward section, the light will be detected by large area avalanche photodiodes (APDs). The current pulses from the APDs will be integrated, amplified and shaped by ASIC chips which were developed for this purpose. The whole calorimeter has been designed in three sections: a forward end-cap, a central barrel and a backward end-cap (BWEC). In this contribution, a status report on the development of the BWEC is presented.
The OLYMPUS collaboration reports on a precision measurement of the positron-proton to electron-proton elastic cross section ratio, \(R_{2\gamma}\), a direct measure of the contribution of hard ...two-photon exchange to the elastic cross section. In the OLYMPUS measurement, 2.01~GeV electron and positron beams were directed through a hydrogen gas target internal to the DORIS storage ring at DESY. A toroidal magnetic spectrometer instrumented with drift chambers and time-of-flight scintillators detected elastically scattered leptons in coincidence with recoiling protons over a scattering angle range of \(\approx 20\degree\) to \(80\degree\). The relative luminosity between the two beam species was monitored using tracking telescopes of interleaved GEM and MWPC detectors at \(12\degree\), as well as symmetric Møller/Bhabha calorimeters at \(1.29\degree\). A total integrated luminosity of 4.5~fb\(^{-1}\) was collected. In the extraction of \(R_{2\gamma}\), radiative effects were taken into account using a Monte Carlo generator to simulate the convolutions of internal bremsstrahlung with experiment-specific conditions such as detector acceptance and reconstruction efficiency. The resulting values of \(R_{2\gamma}\), presented here for a wide range of virtual photon polarization \(0.456<\epsilon<0.978\), are smaller than some hadronic two-photon exchange calculations predict, but are in reasonable agreement with a subtracted dispersion model and a phenomenological fit to the form factor data.
Phys. Rev. Lett. 126, 162501 (2021) We report the first measurement of the average of the electron-proton and
positron-proton elastic scattering cross sections. This lepton charge-averaged
cross ...section is insensitive to the leading effects of hard two-photon
exchange, giving more robust access to the proton's electromagnetic form
factors. The cross section was extracted from data taken by the OLYMPUS
experiment at DESY, in which alternating stored electron and positron beams
were scattered from a windowless gaseous hydrogen target. Elastic scattering
events were identified from the coincident detection of the scattered lepton
and recoil proton in a large-acceptance toroidal spectrometer. The luminosity
was determined from the rates of M{\o}ller, Bhabha and elastic scattering in
forward electromagnetic calorimeters. The data provide some selectivity between
existing form factor global fits and will provide valuable constraints to
future fits.
PANDA Phase One Davì, F; Montalto, L; Krusche, B ...
arXiv.org,
06/2021
Paper, Journal Article
Odprti dostop
The Facility for Antiproton and Ion Research (FAIR) in Darmstadt, Germany, provides unique possibilities for a new generation of hadron-, nuclear- and atomic physics experiments. The future ...antiProton ANnihilations at DArmstadt (PANDA or \(\overline{\rm P}\)ANDA) experiment at FAIR will offer a broad physics programme, covering different aspects of the strong interaction. Understanding the latter in the non-perturbative regime remains one of the greatest challenges in contemporary physics. The antiproton-nucleon interaction studied with PANDA provides crucial tests in this area. Furthermore, the high-intensity, low-energy domain of PANDA allows for searches for physics beyond the Standard Model, e.g. through high precision symmetry tests. This paper takes into account a staged approach for the detector setup and for the delivered luminosity from the accelerator. The available detector setup at the time of the delivery of the first antiproton beams in the HESR storage ring is referred to as the \textit{Phase One} setup. The physics programme that is achievable during Phase One is outlined in this paper.
PDF
