Measurements of the charge ratio and polarization of cosmic-ray muons with the Super-Kamiokande detector
Bibliographic record
Abstract
We present the results of the charge ratio (<a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi>R</a:mi></a:math>) and polarization (<c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:msubsup><c:mi>P</c:mi><c:mn>0</c:mn><c:mi>μ</c:mi></c:msubsup></c:math>) measurements using decay electron events collected between September 2008 and June 2022 with the Super-Kamiokande detector. Because of its underground location and long operation, we are able to perform high-precision measurements by accumulating cosmic-ray muons. We measured the muon charge ratio to be <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mi>R</e:mi><e:mo>=</e:mo><e:mn>1.32</e:mn><e:mo>±</e:mo><e:mn>0.02</e:mn><e:mo stretchy="false">(</e:mo><e:mrow><e:mi>stat</e:mi></e:mrow><e:mo>+</e:mo><e:mrow><e:mi>syst</e:mi></e:mrow><e:mo stretchy="false">)</e:mo></e:math> at <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:msub><i:mi>E</i:mi><i:mi>μ</i:mi></i:msub><i:mi>cos</i:mi><i:msub><i:mi>θ</i:mi><i:mtext>Zenith</i:mtext></i:msub><i:mo>=</i:mo><i:msubsup><i:mn>0.7</i:mn><i:mrow><i:mo>−</i:mo><i:mn>0.2</i:mn></i:mrow><i:mrow><i:mo>+</i:mo><i:mn>0.3</i:mn></i:mrow></i:msubsup><i:mtext> </i:mtext><i:mtext> </i:mtext><i:mi>TeV</i:mi></i:math>, where <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"><k:msub><k:mi>E</k:mi><k:mi>μ</k:mi></k:msub></k:math> is the muon energy and <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:msub><m:mi>θ</m:mi><m:mtext>Zenith</m:mtext></m:msub></m:math> is the zenith angle of incoming cosmic-ray muons. This result is consistent with the Honda flux model while indicating a tension with the <o:math xmlns:o="http://www.w3.org/1998/Math/MathML" display="inline"><o:mi>π</o:mi><o:mi>K</o:mi></o:math> model of <q:math xmlns:q="http://www.w3.org/1998/Math/MathML" display="inline"><q:mn>1.9</q:mn><q:mi>σ</q:mi></q:math>. We also measured the muon polarization at the production location to be <s:math xmlns:s="http://www.w3.org/1998/Math/MathML" display="inline"><s:mrow><s:msubsup><s:mrow><s:mi>P</s:mi></s:mrow><s:mrow><s:mn>0</s:mn></s:mrow><s:mrow><s:mi>μ</s:mi></s:mrow></s:msubsup><s:mo>=</s:mo><s:mn>0.52</s:mn><s:mo>±</s:mo><s:mn>0.02</s:mn><s:mtext> </s:mtext><s:mtext> </s:mtext><s:mo stretchy="false">(</s:mo><s:mrow><s:mi>stat</s:mi></s:mrow><s:mo>+</s:mo><s:mrow><s:mi>syst</s:mi></s:mrow><s:mo stretchy="false">)</s:mo></s:mrow></s:math> at the muon momentum of <w:math xmlns:w="http://www.w3.org/1998/Math/MathML" display="inline"><w:msubsup><w:mn>0.9</w:mn><w:mrow><w:mo>−</w:mo><w:mn>0.1</w:mn></w:mrow><w:mrow><w:mo>+</w:mo><w:mn>0.6</w:mn></w:mrow></w:msubsup><w:mtext> </w:mtext><w:mtext> </w:mtext><w:mi>TeV</w:mi><w:mo>/</w:mo><w:mi>c</w:mi></w:math> at the surface of the mountain; this also suggests a tension with the Honda flux model of <y:math xmlns:y="http://www.w3.org/1998/Math/MathML" display="inline"><y:mn>1.5</y:mn><y:mi>σ</y:mi></y:math>. This is the most precise measurement ever to experimentally determine the cosmic-ray muon polarization near <ab:math xmlns:ab="http://www.w3.org/1998/Math/MathML" display="inline"><ab:mn>1</ab:mn><ab:mtext> </ab:mtext><ab:mtext> </ab:mtext><ab:mi>TeV</ab:mi><ab:mo>/</ab:mo><ab:mi>c</ab:mi></ab:math>. These measurement results are useful to improve atmospheric neutrino simulations. Published by the American Physical Society 2024
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".