Global decay chain vertex fitting at Belle II Krohn, J.-F.; Tenchini, F.; Urquijo, P. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
10/2020, Letnik:
976, Številka:
C
Journal Article
Recenzirano
Odprti dostop
In this paper we report the implementation of a global vertex fitting algorithm within the Belle II analysis software environment, which was originally developed for BaBar (Hulsbergen, 2005). We ...explore the impact of global vertex fitting algorithms for flavour physics analyses with the Belle II detector at the SuperKEKB e+e− collider, such as in the reconstruction of final states with neutral particles, and in fits with geometrical constraints from SuperKEKB’s nano-beam interaction region. The algorithm is compared to the standard vertex fitting algorithm employed by the Belle experiment. We have developed the fitting framework to utilise the EIGEN library for linear algebra operations, reducing the computation time for vertex fitting operations by an order of magnitude over previous methods. This has a significant impact on physics analysis computing efficiency, where vertex fitting over large combinations of final state particles is one of the most CPU intensive operations at Belle II.
One of the fundamental goals of chemistry is to determine how molecular structure influences interactions and leads to different reaction products. Studies of isomer-selected and resolved chemical ...reactions can shed light directly on how form leads to function. In the following, we present the results of gas-phase reactions between acetylene cations (C
2
D
2
+
) with two different isomers of C
3
H
4
: propyne (DC
3
D
3
) and allene (H
2
C
3
H
2
). Our highly controlled, trapped-ion environment allows for precise determination of reaction products and kinetics. From these results, we can infer details of the underlying reaction dynamics of C
2
H
2
+
+ C
3
H
4
. Through the synergy of experimental results and high-level quantum chemical potential energy surface calculations, we are able to identify distinct reaction mechanisms for the two isomers. We find long-range charge exchange with no complex formation is favored for allene, whereas charge exchange leads to an intermediate reaction complex for propyne and thus, different products. Therefore, this reaction displays a pronounced isomer-selective bi-molecular reactive process.
A combined experimental and quantum chemistry study between sympathetically cooled acetylene cations and propyne or allene explains the dramatically different reaction mechanisms.
Friction surfacing (FS) is a solid state technology with increasing applications in the context of localized surface engineering. FS has been investigated mainly for producing fine grained coatings, ...which exhibit superior wear and corrosion properties. Since no bulk melting takes place, this process allows dissimilar joining of materials that would be otherwise incompatible or difficult to deposit by fusion based methods. Several studies also emphasize its energy efficiency and low environmental impact as key advantages when compared with other alternative technologies. Main applications include repair of worn or damaged surfaces through building up or crack sealing. It has also been applied to enhance surface properties at specific areas in the manufacturing of parts and tools. A wide range of material combinations have been deposited by FS, mainly alloy and stainless steels. Aluminium, magnesium and titanium alloys have also been investigated, including the production of metal matrix composites.
Starting with a brief introduction, this review presents a detailed description of the thermo-mechanical and microstructural transformations as well as process modelling approaches. The material combinations investigated so far and the effect of process parameters are also addressed. An overview of the main technologic and equipment advances is presented, including: computational optimization models, surface preparation, gas protection, post-processing methods, pre-heating and cooling. An assessment of the material deposition rate and the specific energy consumption is also provided, comparing friction surfacing to mainstream electric arc, laser and thermal spraying based processes. Based on current process advantages and disadvantages, an outlook on future research and development is provided.
Friction surfacing has a significant potential for further industrial applications and is being developed as a practicable alternative to mainstream coating processes. The present review paper provides a broad overview throughout the fundamentals of FS and the most relevant technology developments, establishing both a theoretical and technical basis for new researchers and industrial practitioners searching for new coating alternatives.
The Full Event Interpretation Keck, T.; Abudinén, F.; Bernlochner, Florian U. ...
Computing and software for big science,
12/2019, Letnik:
3, Številka:
1
Journal Article
Odprti dostop
The full event interpretation is presented: a new exclusive tagging algorithm used by the high-energy physics experiment Belle II. The experimental setup of Belle II allows the precise measurement of ...otherwise inaccessible
B
meson decay modes. The Full Event Interpretation algorithm enables many of these measurements. The algorithm relies on machine learning to automatically identify plausible
B
meson decay chains based on the data recorded by the detector. Compared to similar algorithms employed by previous experiments, the Full Event Interpretation provides a greater efficiency, yielding a larger effective sample size usable in the measurement.
Punzi-loss Abudinén, F.; Bertemes, M.; Bilokin, S. ...
The European physical journal. C, Particles and fields,
2022/2, Letnik:
82, Številka:
2
Journal Article
Recenzirano
Odprti dostop
We present the novel implementation of a non-differentiable metric approximation and a corresponding loss-scheduling aimed at the search for new particles of unknown mass in high energy physics ...experiments. We call the loss-scheduling, based on the minimisation of a figure-of-merit related function typical of particle physics, a Punzi-loss function, and the neural network that utilises this loss function a Punzi-net. We show that the Punzi-net outperforms standard multivariate analysis techniques and generalises well to mass hypotheses for which it was not trained. This is achieved by training a single classifier that provides a coherent and optimal classification of all signal hypotheses over the whole search space. Our result constitutes a complementary approach to fully differentiable analyses in particle physics. We implemented this work using PyTorch and provide users full access to a public repository containing all the codes and a training example.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Hypoxia imparts resistance to radiotherapy and chemotherapy and also promotes a variety of changes in tumor biology through inducible promoters. The purpose of this study was to evaluate the use of ...positron emission tomography (PET) imaging with fluorine-18 fluoromisonidazole (FMISO) in soft tissue sarcomas (STS) as a measure of hypoxia and to compare the results with those obtained using (18)Ffluorodeoxyglucose (FDG) and other known biologic correlates. FDG evaluates energy metabolism in tumors while FMISO uptake is proportional to tissue hypoxia. FMISO uptake was compared with FDG uptake. Vascular endothelial growth factor (VEGF) expression was also compared with FMISO uptake. Nineteen patients with STS underwent PET scanning with quantitative determination of FMISO and FDG uptake prior to therapy (neo-adjuvant chemotherapy or surgery alone). Ten patients receiving neo-adjuvant chemotherapy were also imaged after chemotherapy but prior to surgical resection. Standardized uptake value (SUV) was used to describe FDG uptake; regional tissue to blood ratio (>or=1.2 was considered significant) was used for FMISO uptake. Significant hypoxia was found in 76% of tumors imaged prior to therapy. No correlation was identified between pretherapy hypoxic volume (HV) and tumor grade ( r=0.15) or tumor volume ( r=0.03). The correlation of HV with VEGF expression was 0.39. Individual tumors showed marked heterogeneity in regional VEGF expression. The mean pixel-by-pixel correlation between FMISO and FDG uptake was 0.49 (range 0.09-0.79) pretreatment and 0.32 (range -0.46-0.72) after treatment. Most tumors showed evidence of reduced uptake of both FMISO and FDG following chemotherapy. FMISO PET demonstrates areas of significant and heterogeneous hypoxia in soft tissue sarcomas. The significant discrepancy between FDG and FMISO uptake seen in this study indicates that regional hypoxia and glucose metabolism do not always correlate. Similarly, we did not find any relationship between the hypoxic volume and the tumor volume or VEGF expression. Identification of hypoxia and development of a more complete biologic profile of STS will serve to guide more rational, individualized cancer treatment approaches.
By the process of friction surfacing, coatings are generated from metallic materials at temperatures below their melting range. The high degree of deformation while depositing leads to grain ...refinement in the microstructure, which has a positive effect on the mechanical properties of the layer. The applicability of the process has been described for a large number of materials. The deposition of Ti–6Al–4V has been reported in one publication but was not systematically studied. Therefore, the main aims of the present work are to define the process parameter fields for the deposition of Ti–6Al–4V leading to flash and defect free coatings and associate them with geometric features of the deposited layer.
This investigation has shown that Ti–6Al–4V coatings can be effectively deposited onto a Ti–6Al–4V substrate by friction surfacing. A wide range of process parameters was established in which coatings of high quality have been obtained. The consumption rate control has been implemented as an efficient mode for the deposition of Ti–6Al–4V coatings. Temperature measurements at the coating interface have been accomplished showing that the coating material has been deformed in the β-phase. Furthermore, the homogeneity of the coating surface has been established to be a function of the rotational speed. The coatings exhibited a defect-free bond at the interface with the substrate. Two process parameter ranges with respect to the flash formation have been established. One of them enables flash-free coatings and the other generates coatings with flash formation on the retreating side, which can be controlled by the rotational and deposition speeds. Moreover, an increase in the rotational speed has been shown to lead to an increase in the coating thickness and width as well as an increase in the deposition efficiency up to 39 %.
•A wide range of rotational speeds (300min−1–6000min−1) was applied for the deposition of the titanium alloy by Friction Surfacing.•The rod consumption rate mode has been established as an efficient control mode for the deposition of Ti–6Al–4V layers.•The coating geometry was found to be dependent on the rotational speed and the resulting axial force.•An increase in the rotational speed led to wider and thicker coatings.•Flash formation at the coatings could be controlled using appropriate rotational and deposition speeds.•Ti–6Al–4V has been deformed in the β-phase, because the temperature obtained during the deposition process (in the range of 1021 °C –1299 °C) always exceeded the β–transus temperature (995 °C)
The absolute configurations (ACs) of the iridoid natural products, plumericin (1) and isoplumericin (2), have been re-investigated using vibrational circular dichroism (VCD) spectroscopy, electronic ...circular dichroism (ECD) spectroscopy, and optical rotatory dispersion (ORD). Comparison of DFT calculations of the VCD spectra of 1 and 2 to the experimental VCD spectra of the natural products, (+)-1 and (+)-2, leads unambiguously to the AC (1R,5S,8S,9S,10S)-(+) for both 1 and 2. In contrast, comparison of time-dependent DFT (TDDFT) calculations of the ECD spectra of 1 and 2 to the experimental spectra of (+)-1 and (+)-2 does not permit definitive assignment of their ACs. On the other hand, TDDFT calculations of the ORD of (1R,5S,8S,9S,10S)-1 and -2 over the range of 365−589 nm are in excellent agreement with the experimental data of (+)-1 and (+)-2, confirming the ACs derived from the VCD spectra. Thus, the ACs initially proposed by Albers-Schönberg and Schmid are shown to be correct, and the opposite ACs recently derived from the ECD spectra of 1 and 2 by Elsässer et al. are shown to be incorrect. As a result, the ACs of other iridoid natural products obtained by chemical correlation with 1 and 2 are not in need of revision.
The microstructural evolution during friction surfacing of an aluminum alloy 6082-T6 rod on an aluminum alloy 2024-T351 substrate was characterized using the electron backscatter diffraction ...technique. Crystallographic data were obtained from several regions in the consumable material and in the deposited material. From the results, it can be deduced that the grain structure formation was a complex process governed by the geometrical effect of strain and the superposition of continuous and discontinuous dynamic recrystallizations.
Punzi-loss Abudinén, F; Bertemes, M; Bilokin, S ...
The European physical journal. C, Particles and fields,
02/2022, Letnik:
82, Številka:
2
Journal Article
Recenzirano
Odprti dostop
We present the novel implementation of a non-differentiable metric approximation and a corresponding loss-scheduling aimed at the search for new particles of unknown mass in high energy physics ...experiments. We call the loss-scheduling, based on the minimisation of a figure-of-merit related function typical of particle physics, a Punzi-loss function, and the neural network that utilises this loss function a Punzi-net. We show that the Punzi-net outperforms standard multivariate analysis techniques and generalises well to mass hypotheses for which it was not trained. This is achieved by training a single classifier that provides a coherent and optimal classification of all signal hypotheses over the whole search space. Our result constitutes a complementary approach to fully differentiable analyses in particle physics. We implemented this work using PyTorch and provide users full access to a public repository containing all the codes and a training example.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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![[18F]FMISO and [18F]FDG PET...](http://api.summon.serialssolutions.com/2.0.0/image/issn/XR4PS5YY4K/1619-7070/small "[18F]FMISO and [18F]FDG PET imaging in soft tissue sarcomas: correlation of hypoxia, metabolism and VEGF expression")
