Alignment methods for the OPERA drift tube detector Büttner, B.; Ebert, J.; Ferber, T. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2014, Letnik:
747
Journal Article
Recenzirano
The goal of the OPERA experiment is to give the first direct evidence for neutrino oscillations in the channel νμ→ντ. The OPERA detector is designed to observe the appearance of tau neutrinos in the ...originally pure muon neutrino CNGS beam. An important part of the magnetic spectrometer is the Precision Tracker (PT), a drift tube detector consisting of 9504 drift tubes. Its main task is the determination of the muon charge and momentum. The alignment strategy for the PT consists of two parts: the hardware measurement by theodolite and the software alignment using long muon tracks. In this paper, the hardware and the software alignment are described, and the track-based alignment methods are explained in detail. Results of the software alignment are presented with a focus on the analysis of cosmic particles.
A first result of the search for \numu $\rightarrow$ \nue oscillations in the OPERA experiment, located at the Gran Sasso Underground Laboratory, is presented. The experiment looked for the ...appearance of \nue in the CNGS neutrino beam using the data collected in 2008 and 2009. Data are compatible with the non-oscillation hypothesis in the three-flavour mixing model. A further analysis of the same data constrains the non-standard oscillation parameters $\theta_{new}$ and $\Delta m^2_{new}$ suggested by the LSND and MiniBooNE experiments. For large $\Delta m^{2}_{new}$ values ($>$0.1 eV$^{2}$), the OPERA 90% C.L. upper limit on sin$^{2}(2\theta_{new})$ based on a Bayesian statistical method reaches the value $7.2 \times 10^{-3}$.
The gas system of the drift tube detector of the neutrino experiment OPERA is presented. The drift tube detector, called precision tracker (PT), consists of 10
000 thinwalled aluminum tubes of 38
mm ...diameter and 8
m length filled with an 80% Ar 20%
CO
2
gas mixture. The total gas volume amounts to
80
m
3
. During stable operation the gas is exchanged once per 80
h and not recycled. Thus about 1
m
3 per hour is consumed. Argon and
CO
2
are stored and supplied in liquid form. Subsequently they are mixed and the composition ratio is regulated with a precision better than 1% per component. Inside the drift tubes the gas is kept at a constant absolute pressure within
±
0.5
%
. Since the experiment is operated in the low activity environment of the Gran Sasso underground laboratory, monitoring of the gas quality with a radioactive source is prohibited. Instead the oxygen content of the used gas is measured. We report on the first experience with the performance of the gas system.
The OPERA neutrino experiment in the underground Gran Sasso Laboratory (LNGS) was designed to perform the first detection of neutrino oscillations in direct appearance mode in the ...$\nu_\mu\rightarrow\nu_\tau$ channel, the $\nu_\tau$ signature being the identification of the $\tau$-lepton created in its charged current interaction. The hybrid apparatus consists of a large mass emulsion film/lead target complemented by electronic detectors. It is placed in the high energy long-baseline CERN to LNGS neutrino beam (CNGS) 730 km away from the neutrino source. The observation of a first $\nu_\tau$ candidate event was reported in 2010. In this paper, we present the status of the experiment based on the analysis of the data taken during the first two years of operation (2008-2009). The statistical significance of the one event observed so far is then assessed.
The OPERA neutrino detector in the underground Gran Sasso Laboratory (LNGS) has been designed to perform the first detection of neutrino oscillations in direct appearance mode through the study of ...the $\nu_\mu\rightarrow\nu_\tau$ channel. The hybrid apparatus consists of an emulsion/lead target complemented by electronic detectors and it is placed in the high energy long-baseline CERN to LNGS beam (CNGS) 730 km away from the neutrino source. Runs with CNGS neutrinos were successfully carried out in 2008 and 2009. After a brief description of the beam, the experimental setup and the procedures used for the analysis of the neutrino events, we describe the topology and kinematics of a first candidate $\nu_\tau$ charged-current event satisfying the kinematical selection criteria. The background calculations and their cross-check are explained in detail and the significance of the event is assessed.
The OPERA neutrino experiment is designed to perform the first observation of neutrino oscillations in direct appearance mode in the nu ^sub mu^ arrow right nu ^sub tau^ channel, via the detection of ...the tau-leptons created in charged current nu^sub tau^ interactions. The detector, located in the underground Gran Sasso Laboratory, consists of an emulsion/lead target with an average mass of about 1.2 kt, complemented by electronic detectors. It is exposed to the CERN Neutrinos to Gran Sasso beam, with a baseline of 730 km and a mean energy of 17 GeV. The observation of the first nu ^sub tau^ candidate event and the analysis of the 2008-2009 neutrino sample have been reported in previous publications. This work describes substantial improvements in the analysis and in the evaluation of the detection efficiencies and backgrounds using new simulation tools. The analysis is extended to a sub-sample of 2010 and 2011 data, resulting from an electronic detector-based pre-selection, in which an additional nu ^sub tau^ candidate has been observed. The significance of the two events in terms of a nu ^sub mu^ arrow right nu ^sub tau^ oscillation signal is of 2.40sigma. Figure not available: see fulltext.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image) A first result of the search for nu ^sub mu^ arrow right nu ^sub e^ oscillations in the OPERA experiment, located at the ...Gran Sasso Underground Laboratory, is presented. The experiment looked for the appearance of nu ^sub e^ in the CNGS neutrino beam using the data collected in 2008 and 2009. Data are compatible with the non-oscillation hypothesis in the three-flavour mixing model. A further analysis of the same data constrains the non-standard oscillation parameters theta ^sub new^ and ... suggested by the LSND and MiniBooNE experiments. For large ... values (>0.1 eV^sup 2^), the OPERA 90% C.L. upper limit on sin^sup 2^(2theta ^sub new^) based on a Bayesian statistical method reaches the value 7.2 × 10^sup -3^.
This paper describes an alternative method for helmet design using finite element analysis (FEA). While previous research has illustrated the use of FEA as a tool to simulate standard helmet tests, ...the objective of this research was to use FEA as a tool to optimize the performance characteristics of the energy absorbing (EA) liner of an existing Navy helicopter pilot helmet (i.e., the HGU-84/P). Three dimensional finite element models (FEM) of the helmet components and the test headform were developed using MSC software and material properties were estimated from published data and physical tests. A 6.0 m/s flat anvil impact was then simulated at three different sites on the helmet using MSC.Dytran software and these simulations served as the baseline. Full scale impact tests were performed with an examplar helmet in order to confirm the validity of the simulations as well as the helmet shell and liner material properties.
A group of candidate EA materials were obtained and physical impact tests were conducted in order to quantify the stress-strain characteristics of each candidate material. These stress-strain characteristics were then used to define the material properties of the existing HGU-84/P helmet liner FEM, effectively replacing the existing helmet EA liner with one fabricated from the candidate material. Whenever possible, a given EA liner material was evaluated over a range of densities. This allowed the researchers to study the effect of manipulating the EA liner density properties of the helmet without the necessity of conducting physical tests.
A total of 13 EA materials in different densities were evaluated by conducting over 120 FEM impact simulations at each of the three impact sites. The performance of a given EA liner material was evaluated by comparing simulation results with the peak headform acceleration values obtained from physical tests of the actual HGU-84/P helmet. The simulation results effectively predicted trends in liner material performance and making it possible to identify a small group of EA liner materials with a good likelihood of providing improved impact protection.
The results of this research clearly illustrate that FEA can be an effective tool for the analysis and design of both new and existing helmet designs. Simulation of various helmet liner materials allows for the evaluation of multiple material configurations, without the expense associated with production and testing of physical prototypes. This research and development tool can be particularly useful in the evaluation of new energy absorbing materials in applications where production and testing of individual helmet samples is quite costly (e.g., advanced composite helmet designs) and for applications where the geometric properties of the helmet are fixed (e.g., existing helmet designs).