1,720,988 research outputs found
Sensitivity and background estimates for phase-II of the COMET experiment
Full text linkConservation of Lepton Flavour in the Standard Model (SM) requires that neutrino emission accompanies muon decay. COMET is one experiment looking for Charged Lepton Flavour Violation. It searches for COherent Muon to Electron Transitions, where a muon converts to a 105 MeV electron in the presence of an atomic nucleus, without emitting neutrinos. The current limit on this process is at 90% C.L., which COMET intends to improve by four orders of magnitude.
To realise such an improvement, COMET will use several novel techniques to produce a very intense, low-energy muon beam, with very high signal acceptance and strong background suppression. Given the challenge this presents, COMET will run in a staged approach. Phase-I is currently under construction with first data-taking due in JFY 2018, and the goal of measuring -e conversion with a Single-Event Sensitivity (SES) of . Phase-II should follow at the start of the next decade and achieve a SES of .
This thesis provides an overview of CLFV, -e conversion, and the COMET experiment itself. It sets out the software and simulation that has been developed to help understand and analyse the experiment, and then uses this to perform a comprehensive optimisation of the Phase-II set-up, providing a new baseline configuration. The expected performance of this baseline is assessed, with studies on the signal sensitivity demonstrating that an SES of can be achieved in s of beam. Background rates are also estimated and, although subject to large uncertainties, predict 0.662 background events can be expected during Phase-II. Suggestions for future performance studies and experiment improvements are also discussed, with a possible improvement in the SES of a factor of 2.5 likely achievable.Open Acces
Low-energy event physics with the T2K neutrino detector SuperFGD and global neutrino data fitting with GAMBIT
No full textThe field of neutrino oscillation physics has yielded numerous significant results in recent decades. The Japan-based long-baseline accelerator neutrino oscillation Tokai-to-Kamioka (T2K) experiment, renowned for its contributions to accelerator neutrino oscillation studies, is undergoing several upgrades to further advance high-impact measurements. Among the newly constructed subdetectors of the T2K off-axis near detector ND280 is the Super Fine-Grained Detector (SuperFGD), which was installed in 2023. It is a high-resolution particle tracker that is made up of approximately two million plastic scintillating cubes. Its novel design allows the detector to measure neutrino interactions with high precision, an essential key to reducing uncertainties of current and future neutrino experiments.
This thesis includes a brief summary of the SuperFGD design and the related calibration tasks. In particular, the charge and pedestal calibration for the Multi-Pixel Photon Counters (MPPCs) are described in detail. A neural network based on a Transformer architecture developed for general voxelised 3D detectors was utilised to increase calibration tolerance.
Finally, this thesis presents the development of a Standard Model three-neutrino oscillation global fit study within the GAMBIT software framework, where the incorporation of the likelihood functions of the NOA, MINOS, and KamLAND experiments are detailed. Their validation results demonstrate good agreement with the experimental counterparts, but the limited public data and experiment information negatively affect the accuracy of the implementations. A preliminary scan, which included eight neutrino oscillation experiments that covered a wide range of measurement technologies, was also performed. In general, the early results are consistent with the existing neutrino global fits, and some noticeable deviations are discussed.Open Acces
Study of the kaon contribution to the T2K neutrino beam using neutrino interactions in the Near Detector
Full text linkT2K is a long-baseline neutrino oscillation experiment. It uses an accelerator-
produced neutrino beam, whereby a beam of protons impinges on a nuclear
target, producing kaon and pion mesons that decay to neutrinos. The main
neutrino detectors are situated at 2.50 off-axis from the centre of the beam. An
accurate flux prediction for this off-axis beam is crucial to achieve the sensitivity required for the goals of T2K. External experiments reduce the major flux uncertainty (hadronic interactions in the target), but are inherently independent of the real and variable beamline conditions of T2K. Therefore, in situ
measurements are required to validate the flux. This thesis uses data from the
T2K near detector (ND280) to validate the
ux prediction.
The normalisation of K+-originating neutrinos at the ND280 is measured.
The K+ beam component is important since K+ daughters dominate the high
energy part of the μ beam and contribute to the intrinsic e contamination.
As many aspects of the beam simulation affect this measurement, including the
hadron production at the target and the off-axis angle, it is used to validate
the entire system. The November 2010 to March 2011 data set is used, corresponding to 7:837 x 1019 protons on target. μ charged-current interactions are
selected (with 86.3% purity) using the ND280 tracker and binned according to
the momentum and angle of the muon candidate. The Monte Carlo (MC) is fitted to the data to extract the normalisations of both K+ and π+ originating
neutrinos, bK and bπ respectively. The flux, cross-section and detector systematic errors are considered. The best fit point is at bK = 0:86 and bπ = 0:78,
consistent with the nominal MC at the 1σ level.
Additionally, results of the first time calibration of the ND280 detector,
primarily of the ECal sub-detector, are presented
Measuring charged current neutrino interactions in the electromagnetic calorimeters of the ND280 detector
Full text linkThis thesis presents a study of neutrino interactions within the electromagnetic
calorimeters (ECals) of the Tokai-to-Kamioka (T2K) off -axis
near detector (ND280), using data collected from T2K Run II and
Run III.
Neutrino oscillation physics is a rapidly advancing field, with the
recent discovery of non-zero [Symbol appears here. To view, please open pdf attachment]13 allowing the possibility of measuring CP-violation
in the lepton sector. The current neutrino beam experiments
must make precise measurements of the oscillation parameters and to do
this require an improved understanding of neutrino interactions, which
can only come through better measurements of neutrino cross-sections.
This thesis describes the development of a neutrino event selection
using a boosted decision tree multi-variate analysis to separate interactions
within the ND280 ECals from entering backgrounds. This is
then used to provide a selection of neutrino event samples from each
ECal module, which are inputs to a X2 fit that is used to extract the
[Symbols appears here. To view, please open pdf attachment] charged current inclusive cross-section, which was found to be [Mathematical equation appears here. To view, please open pdf attachment].Open Acces
Neutrino Induced Charged Current π+ Production at the T2K Near Detector
Full text linkA study of ν µ-induced charged current (CC) π+ production at the T2K off -axis near detector
(ND280) is presented. Using Monte Carlo (MC) data studies event selections for
both CC-inclusive and enriched CC- π+ samples have been developed using the ND280
tracker-region and surrounding ECals. Two types of CC- π+ selections were developed - one using the TPC to identify the pion and the other using a new ECal PID based on the
deposited charge per unit length. Data/MC ratios are calculated and compared with the
associated detector, neutrino interaction and
flux simulation systematics.
The predicted neutrino interaction rate was based on v2.6.2 of the GENIE MC generator
and on T2Ks tuned 11a JNUBEAM
flux simulation. The data used was collected between
Nov. 2010 and March 2011 during the Run 2 data taking period and corresponds to a
total integrated POT of 7.83 x 10[to the power of 19]. For the ν µ-CC-Inclusive selection which selects ν µ -CC
interactions with a purity of 88:1% we find:
[Mathematical formulae appear here. To view, please open pdf attachment]
These show that the current measured and predicted rates for both the inclusive rate of ν µ
neutrino interactions and those with at least one π+ in the final state agree to within the
systematic uncertainties associated with neutrino interaction and
flux simulation. Moreover,
these selections lay the groundwork for future analyses, using larger data sets, that
can be used to constrain these sources of uncertainty
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
