Featured Researches

High Energy Physics Experiment

A Comment on the note arXiv:2006.13147 on arXiv:2005.05301, "Preparation of the Neutrino-4 experiment on search for sterile neutrino and the obtained results of measurements"

Here is response Neutrino-4 collaboration to the note arXiv:2006.13147 on article "Preparation of the Neutrino-4 experiment on search for sterile neutrino and the obtained results of measurements" arXiv:2005.05301. Red text is commentary from the note arXiv:2006.13147, black text is our answers.

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High Energy Physics Experiment

A Convolutional Neural Network based Cascade Reconstruction for the IceCube Neutrino Observatory

Continued improvements on existing reconstruction methods are vital to the success of high-energy physics experiments, such as the IceCube Neutrino Observatory. In IceCube, further challenges arise as the detector is situated at the geographic South Pole where computational resources are limited. However, to perform real-time analyses and to issue alerts to telescopes around the world, powerful and fast reconstruction methods are desired. Deep neural networks can be extremely powerful, and their usage is computationally inexpensive once the networks are trained. These characteristics make a deep learning-based approach an excellent candidate for the application in IceCube. A reconstruction method based on convolutional architectures and hexagonally shaped kernels is presented. The presented method is robust towards systematic uncertainties in the simulation and has been tested on experimental data. In comparison to standard reconstruction methods in IceCube, it can improve upon the reconstruction accuracy, while reducing the time necessary to run the reconstruction by two to three orders of magnitude.

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High Energy Physics Experiment

A Data-driven Event Generator for Hadron Colliders using Wasserstein Generative Adversarial Network

Highly reliable Monte-Carlo event generators and detector simulation programs are important for the precision measurement in the high energy physics. Huge amounts of computing resources are required to produce a sufficient number of simulated events. Moreover, simulation parameters have to be fine-tuned to reproduce situations in the high energy particle interactions which is not trivial in some phase spaces in physics interests. In this paper, we suggest a new method based on the Wasserstein Generative Adversarial Network (WGAN) that can learn the probability distribution of the real data. Our method is capable of event generation at a very short computing time compared to the traditional MC generators. The trained WGAN is able to reproduce the shape of the real data with high fidelity.

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High Energy Physics Experiment

A New Journey to the Center of the Earth

There are still several unanswered fundamental questions concerning our planet and in particular, about the deep Earth, from where we lack direct samples. Today, due to the progress in neutrino-detection techniques, a new and unique tool to study our planet exists: geoneutrinos, antineutrinos from the decays of long-lived radioactive elements inside the Earth. In 2020, the Borexino experiment published its updated geoneutrino measurement. Thanks to the increase in acquired data and the improved analysis techniques in an enlarged fiducial volume, the final precision has significantly improved, corresponding to a total geoneutrino signal of 47.0+8.4??.7(stat)+2.4??.9(sys)TNU. The null-hypothesis of the geoneutrino signal from the Earth's mantle was excluded at a 99% C.L. for the first time, while exploiting the knowledge of the local crust around the detector. The article will introduce the field and describe the key elements of the updated analysis. Geological interpretation and significance of the new result will be discussed in terms of the corresponding radiogenic heat and the limits to a hypothetical georeactor.

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High Energy Physics Experiment

A Review of Basic Energy Reconstruction Techniques in Liquid Xenon and Argon Detectors for Dark Matter and Neutrino Physics Using NEST

Detectors based upon the noble elements, especially liquid xenon as well as liquid argon, as both single- and dual-phase types, require reconstruction of the energies of interacting particles, both in the field of direct detection of dark matter (Weakly Interacting Massive Particles or WIMPs, axions, etc.) and in neutrino physics. Experimentalists, as well as theorists who reanalyze/reinterpret experimental data, have used a few different techniques over the past few decades. In this paper, we review techniques based on solely the primary scintillation channel, the ionization or secondary channel available at non-zero drift electric fields, and combined techniques that include a simple linear combination and weighted averages, with a brief discussion of the applications of profile likelihood, maximum likelihood, and machine learning. Comparing results for electron recoils (beta and gamma interactions) and nuclear recoils (primarily from neutrons) from the Noble Element Simulation Technique (NEST) simulation to available data, we confirm that combining all available information generates higher-precision means, lower widths (energy resolution), and more symmetric shapes (approximately Gaussian) especially at keV-scale energies, with the symmetry even greater when thresholding is addressed. Near thresholds, bias from upward fluctuations matters. For MeV-GeV scales, if only one channel is utilized, an ionization-only-based energy scale outperforms scintillation; channel combination remains beneficial. We discuss here what major collaborations use.

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High Energy Physics Experiment

A Search for Charged Excitation of Dark Matter with the KamLAND-Zen Detector

There are many theories where a dark matter particle is part of a multiplet with an electrically charged state. If WIMP dark matter (?0) is accompanied by a charged excited state (???) separated by a small mass difference, it can form a stable bound state with a nucleus. In supersymmetric models, the?0and the???could be the neutralino and a charged slepton, such as the neutralino-stau degenerate model. The formation binding process is expected to result in an energy deposition of {\it O}(1--10 MeV), making it suitable for detection in large liquid scintillator detectors. We describe new constraints on the bound state formation with a xenon nucleus using the KamLAND-Zen 400 Phase-II dataset. In order to enlarge the searchable parameter space, all xenon isotopes in the detector were used. For a benchmark parameter set ofm?0=100GeV and?m=10MeV, this study sets the most stringent upper limits on the recombination cross section?�σv??and the decay-width of???of2.0?10??1cm3/sand1.1?10??8GeV, respectively (90\% confidence level).

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High Energy Physics Experiment

A Search for Charged Lepton Flavor Violation in the Mu2e Experiment

The Mu2e experiment will search for the neutrino-less conversion of a muon into an electron in the field of an aluminum nucleus. An observation would be the first signal of charged lepton flavor violation and de facto evidence for new physics beyond the Standard Model. The clean signature of the conversion process offers an opportunity for a powerful search: Mu2e will probe four orders of magnitude beyond current limits, with real discovery potential over a wide range of well motivated new physics models. This goal requires an integrated system of solenoids that will create the most intense muon beam in the world, and suppression of all possible background sources. The Mu2e components are currently being constructed, with the experiment planned to begin operations in the Fermilab Muon Campus within the next few years.

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High Energy Physics Experiment

A Study of Multifractal Analysis in 16O-AgBr Collisions at 60A and 200A GeV

A multifractal analysis to study the multiparticle dynamics in 60A and 200A GeV/c 16O-AgBr collisions has been performed in the pseudorapidity phase space. Multifractal moments Gq as the function of pseudorapidity bin size for different order of the moments, q have been calculated. The power-law behaviour has been observed in the considered data sets. The variation of multifractal dimensions, Dq and multifractal spectral function, f(αq) with order of the moments, q have been studied thoroughly. Dq is found to decrease with increasing order of the moments, q indicating thereby a self-similar behaviour in the multiparticle production in the considered collisions. We have also found a concave downward curve of multifractal spectral function with maxima q=0.

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High Energy Physics Experiment

A Study of Pseudo-Central Collision Events Observed in Pion-Nucleus Interactions

The present study is based on the interactions caused by 340-GeV negative pions with emulsion nuclei. The main aim of this paper is to investigate some aspects of central collision events. Thus, the events in which the total number of charged shower particles is greater than or equal to twenty eight (Ns geq 28) were chosen for the analysis. They are not exactly central collision events, but may be considered as pseudo-central collision events. The angular characteristics of relativistic charged secondaries have been studied in terms of pseudo-rapidity, and bimodality is found to be absent in the distributions. The mean pseudo-rapidity seems to be independent of grey and heavy particle multiplicities, which indicates its independence with number of collisions. Finally, the correlation between different particle multiplicities in this paper is discussed.

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High Energy Physics Experiment

A calibration of the Belle II hadronic tag-side reconstruction algorithm withB→Xℓνdecays

Tag-side reconstruction is an important method for reconstructingBmeson decays with missing energy. The Belle II tag-side reconstruction algorithm, Full Event Interpretation, relies on a hierarchical reconstruction ofBmeson decays with multivariate classification employed at each stage of reconstruction. Given the large numbers of classifiers employed and decay chains reconstructed, the performance of the algorithm on data and simulation differs significantly. Here, calibration factors are derived for hadronic tag-sideBdecays by measuring a signal side decay,B→Xℓν, in34.6fb−1of Belle II data. For a very loose selection on the tag-sideBmultivariate classifier, the calibration factors are0.65±0.02and0.83±0.03for tag-sideB+andB0mesons, respectively.

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