A novel generic framework for track fitting in complex detector systems Höppner, C.; Neubert, S.; Ketzer, B. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2010, Letnik:
620, Številka:
2
Journal Article
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This paper presents a novel framework for track fitting which is usable in a wide range of experiments, independent of the specific event topology, detector setup, or magnetic field arrangement. This ...goal is achieved through a completely modular design. Fitting algorithms are implemented as interchangeable modules. At present, the framework contains a validated Kalman filter. Track parameterizations and the routines required to extrapolate the track parameters and their covariance matrices through the experiment are also implemented as interchangeable modules. Different track parameterizations and extrapolation routines can be used simultaneously for fitting of the same physical track. Representations of detector hits are the third modular ingredient to the framework. The hit dimensionality and orientation of planar tracking detectors are not restricted. Tracking information from detectors which do not measure the passage of particles in a fixed physical detector plane, e.g. drift chambers or TPCs, is used without any simplification. The concept is implemented in a light-weight C++ library called GENFIT, which is available as free software.
The COMPASS setup for physics with hadron beams Abbon, P.; Adolph, C.; Amoroso, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2015, Letnik:
779
Journal Article
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The main characteristics of the COMPASS experimental setup for physics with hadron beams are described. This setup was designed to perform exclusive measurements of processes with several charged ...and/or neutral particles in the final state. Making use of a large part of the apparatus that was previously built for spin structure studies with a muon beam, it also features a new target system as well as new or upgraded detectors. The hadron setup is able to operate at the high incident hadron flux available at CERN. It is characterised by large angular and momentum coverages, large and nearly flat acceptances, and good two and three-particle mass resolutions. In 2008 and 2009 it was successfully used with positive and negative hadron beams and with liquid hydrogen and solid nuclear targets. This paper describes the new and upgraded detectors and auxiliary equipment, outlines the reconstruction procedures used, and summarises the general performance of the setup.
The Collins and Sivers asymmetries for charged hadrons produced in deeply inelastic scattering on transversely polarised protons have been extracted from the data collected in 2007 with the CERN SPS ...muon beam tuned at 160 GeV/c. At large values of the Bjorken x variable non-zero Collins asymmetries are observed both for positive and negative hadrons while the Sivers asymmetry for positive hadrons is slightly positive over almost all the measured x range. These results strongly support the present theoretical interpretation of these asymmetries, in terms of leading-twist quark distribution and fragmentation functions.
A measurement of the azimuthal asymmetry in dihadron production in deep-inelastic scattering of muons on transversely polarised proton (NH3) targets is presented. They provide independent access to ...the transversity distribution functions through the measurement of the Collins asymmetry in single hadron production. The data were taken in the year 2010 with the COMPASS spectrometer using a 160 GeV/c muon beam of the CERN SPS, increasing by a factor of about four the overall statistics with respect to the previously published data taken in the year 2007. The measured sizeable asymmetry is in good agreement with the published data. An approximate equality of the Collins asymmetry and the dihadron asymmetry is observed, suggesting a common physical mechanism in the underlying fragmentation.
Components in industrial furnaces and apparatus construction are usually exposed to temperatures up to 1,200 °C as well as mechanical loading and corrosive attack of the environmental atmosphere. ...Furthermore, they undergo numerous temperature cycles in service. To describe the characteristics of the nickel base Alloy 602 CA, which is often used in this industrial sector, the long term creep behavior of this alloy was studied at temperatures from 800 °C to 1,200 °C with and without thermal cycling. During these tests unexpected effects could be noticed. At load levels representing typical component loads and isothermal temperature control an anomalous decrease in creep rate in the third creep stage was observed. Experiments under thermal cycling showed a considerably higher creep rate in the whole range than in the isothermal case. Within the present article, these findings are outlined in detail together with a brief discussion of causes and consequences based on extensive microstructural examinations.
Translation
Bauteile im industriellen Ofen‐ und Apparatebau sind Temperaturen bis über 1.200 °C sowie mechanischer Beanspruchung und korrosivem Angriff durch die Umgebungsatmosphäre ausgesetzt. Außerdem kommt es während des Betriebs zu zahlreichen Temperaturwechseln. Um die Eigenschaften der Nickelbasislegierung Alloy 602 CA unter diesen Bedingungen zu beschreiben, wurde das langzeitige Kriechverhalten bei Temperaturen von 800 °C bis 1.200 °C mit und ohne zyklische Temperaturwechselbeanspruchung experimentell untersucht. Bei niedrigen Spannungen und isothermer Versuchsführung wurde hierbei eine ungewöhnliche Abnahme der Dehnrate im tertiären Kriechbereich beobachtet. Unter Temperaturwechselbeanspruchung konnte dagegen eine erheblich höhere Dehnrate im Vergleich zum isothermen Fall festgestellt werden. Die Diskussion der experimentellen Ergebnisse sowie der ergründeten Ursachen auf Basis mikrostruktureller Nachuntersuchungen sind Hauptgegenstände des vorliegenden Beitrags.
In this paper, a systematic examination of the creep behavior of the material Alloy 602 CA and resulting unexpected effects will be discussed. Findings and approaches will be outlined to clarify the phenomena of an unusual decrease in creep rate within the tertiary creep regime under isothermal conditions as well as the effect of an increased creep rate under anisothermal conditions.
Multiplicities of charged hadrons produced in deep inelastic muon scattering off a
6
LiD target have been measured as a function of the DIS variables
x
Bj
,
Q
2
,
W
2
and the final state hadron ...variables
p
T
and
z
. The
distributions are fitted with a single exponential function at low values of
to determine the dependence of
on
x
Bj
,
Q
2
,
W
2
and
z
. The
z
-dependence of
is shown to be a potential tool to extract the average intrinsic transverse momentum squared of partons,
, as a function of
x
Bj
and
Q
2
in a leading order QCD parton model.
Double-spin asymmetries for production of charged pions and kaons in semi-inclusive deep-inelastic muon scattering have been measured by the COMPASS experiment at CERN. The data, obtained by ...scattering a 160 GeV muon beam off a longitudinally polarised NH
3 target, cover a range of the Bjorken variable
x between 0.004 and 0.7. A leading order evaluation of the helicity distributions for the three lightest quarks and antiquark flavours derived from these asymmetries and from our previous deuteron data is presented. The resulting values of the sea quark distributions are small and do not show any sizable dependence on
x in the range of the measurements. No significant difference is observed between the strange and antistrange helicity distributions, both compatible with zero. The integrated value of the flavour asymmetry of the helicity distribution of the light-quark sea,
Δ
u
¯
−
Δ
d
¯
, is found to be slightly positive, about 1.5 standard deviations away from zero.
The COMPASS collaboration at CERN has investigated pion Compton scattering, π(-)γ→π(-)γ, at center-of-mass energy below 3.5 pion masses. The process is embedded in the reaction π(-)Ni→π(-)γNi, which ...is initiated by 190 GeV pions impinging on a nickel target. The exchange of quasireal photons is selected by isolating the sharp Coulomb peak observed at smallest momentum transfers, Q(2)<0.0015 (GeV/c)(2). From a sample of 63,000 events, the pion electric polarizability is determined to be α(π)=(2.0±0.6(stat)±0.7(syst))×10(-4) fm(3) under the assumption α(π)=-β(π), which relates the electric and magnetic dipole polarizabilities. It is the most precise measurement of this fundamental low-energy parameter of strong interaction that has been addressed since long by various methods with conflicting outcomes. While this result is in tension with previous dedicated measurements, it is found in agreement with the expectation from chiral perturbation theory. An additional measurement replacing pions by muons, for which the cross-section behavior is unambiguously known, was performed for an independent estimate of the systematic uncertainty.
We present the case of a 28-year-old female who presented for primary care at 22-week gestation with type II achalasia and worsening solid/liquid dysphagia leading to pregnancy weight loss. ...Considering that durable therapies such as surgical myotomy and pneumatic dilatation have considerable risk, botulinum A toxin injection was selected as a temporizing bridging therapy. She had an uncomplicated post procedure course and had significant rapid improvement in dysphagia symptoms, which enabled her to progress to normal peripartum weight. This case highlights the need for early recognition of achalasia and an unique niche for use of botulinum toxin A as a temporizing therapy in this risk averse population.
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