Observation of double <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>J</mml:mi></mml:mrow><mml:mo>/</mml:mo><mml:mi>ψ</mml:mi></mml:math> meson production in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>p</mml:mi><mml:mi>Pb</mml:mi></mml:mrow></mml:math> collisions at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msqrt><mml:mrow><mml:msub><mml:mrow><mml:mi>s</mml:mi></mml:mrow><mml:mrow><mml:mi>NN</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:msqrt><mml:mo>=</mml:mo><mml:mn>8.16</mml:mn><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:mi>TeV</mml:mi></mml:mrow></mml:math>
Bibliographic record
Abstract
The first observation of the concurrent production of two <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mi>J</a:mi><a:mo>/</a:mo><a:mi>ψ</a:mi></a:mrow></a:math> mesons in proton-nucleus collisions is presented. The analysis is based on a proton-lead (<c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mi>p</c:mi><c:mi>Pb</c:mi></c:math>) data sample recorded at a nucleon-nucleon center-of-mass energy of 8.16 TeV by the CMS experiment at the CERN LHC and corresponding to an integrated luminosity of <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mn>174.6</e:mn><e:mtext> </e:mtext><e:mtext> </e:mtext><e:msup><e:mi>nb</e:mi><e:mrow><e:mo>−</e:mo><e:mn>1</e:mn></e:mrow></e:msup></e:math>. The two <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mi>J</g:mi><g:mo>/</g:mo><g:mi>ψ</g:mi></g:math> mesons are reconstructed in their <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:mrow><i:msup><i:mrow><i:mi>μ</i:mi></i:mrow><i:mrow><i:mo>+</i:mo></i:mrow></i:msup><i:msup><i:mrow><i:mi>μ</i:mi></i:mrow><i:mrow><i:mo>−</i:mo></i:mrow></i:msup></i:mrow></i:math> decay channels with transverse momenta <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"><k:msub><k:mi>p</k:mi><k:mi mathvariant="normal">T</k:mi></k:msub><k:mo>></k:mo><k:mn>6.5</k:mn><k:mtext> </k:mtext><k:mtext> </k:mtext><k:mi>GeV</k:mi></k:math> and rapidity <n:math xmlns:n="http://www.w3.org/1998/Math/MathML" display="inline"><n:mrow><n:mo stretchy="false">|</n:mo><n:mi>y</n:mi><n:mo stretchy="false">|</n:mo></n:mrow><n:mo><</n:mo><n:mn>2.4</n:mn></n:math>. Events where one of the <r:math xmlns:r="http://www.w3.org/1998/Math/MathML" display="inline"><r:mi>J</r:mi><r:mo>/</r:mo><r:mi>ψ</r:mi></r:math> mesons is reconstructed in the dielectron channel are also considered in the search. The <t:math xmlns:t="http://www.w3.org/1998/Math/MathML" display="inline"><t:mi>p</t:mi><t:mi>Pb</t:mi><t:mo stretchy="false">→</t:mo><t:mrow><t:mrow><t:mi>J</t:mi><t:mo>/</t:mo><t:mi>ψ</t:mi></t:mrow><t:mrow><t:mi>J</t:mi><t:mo>/</t:mo><t:mi>ψ</t:mi></t:mrow><t:mo>+</t:mo><t:mrow><t:mi>X</t:mi></t:mrow></t:mrow></t:math> process is observed with a significance of 5.3 standard deviations. The measured inclusive fiducial cross section, using the four-muon channel alone, is <w:math xmlns:w="http://www.w3.org/1998/Math/MathML" display="inline"><w:mi>σ</w:mi><w:mo stretchy="false">(</w:mo><w:mi>p</w:mi><w:mi>Pb</w:mi><w:mo stretchy="false">→</w:mo><w:mrow><w:mi>J</w:mi><w:mo>/</w:mo><w:mi>ψ</w:mi></w:mrow><w:mrow><w:mi>J</w:mi><w:mo>/</w:mo><w:mi>ψ</w:mi></w:mrow><w:mo>+</w:mo><w:mrow><w:mi>X</w:mi></w:mrow><w:mo stretchy="false">)</w:mo><w:mo>=</w:mo><w:mspace linebreak="goodbreak"/><w:mn>22.0</w:mn><w:mo>±</w:mo><w:mn>8.9</w:mn><w:mo stretchy="false">(</w:mo><w:mi>stat</w:mi><w:mo stretchy="false">)</w:mo><w:mo>±</w:mo><w:mn>1.5</w:mn><w:mo stretchy="false">(</w:mo><w:mi>syst</w:mi><w:mo stretchy="false">)</w:mo><w:mtext> </w:mtext><w:mtext> </w:mtext><w:mi>nb</w:mi></w:math>. A fit of the data to the expected rapidity separation for pairs of <gb:math xmlns:gb="http://www.w3.org/1998/Math/MathML" display="inline"><gb:mi>J</gb:mi><gb:mo>/</gb:mo><gb:mi>ψ</gb:mi></gb:math> mesons produced in single (SPS) and double (DPS) parton scatterings yields <ib:math xmlns:ib="http://www.w3.org/1998/Math/MathML" display="inline"><ib:mrow><ib:msubsup><ib:mrow><ib:mi>σ</ib:mi></ib:mrow><ib:mrow><ib:mi>SPS</ib:mi></ib:mrow><ib:mrow><ib:mi>p</ib:mi><ib:mi>Pb</ib:mi><ib:mo stretchy="false">→</ib:mo><ib:mrow><ib:mi>J</ib:mi><ib:mo>/</ib:mo><ib:mi>ψ</ib:mi></ib:mrow><ib:mrow><ib:mi>J</ib:mi><ib:mo>/</ib:mo><ib:mi>ψ</ib:mi></ib:mrow><ib:mo>+</ib:mo><ib:mrow><ib:mi>X</ib:mi></ib:mrow></ib:mrow></ib:msubsup><ib:mo>=</ib:mo><ib:mn>16.5</ib:mn><ib:mo>±</ib:mo><ib:mn>10.8</ib:mn><ib:mo stretchy="false">(</ib:mo><ib:mi>stat</ib:mi><ib:mo stretchy="false">)</ib:mo><ib:mo>±</ib:mo><ib:mn>0.1</ib:mn><ib:mo stretchy="false">(</ib:mo><ib:mi>syst</ib:mi><ib:mo stretchy="false">)</ib:mo><ib:mtext> </ib:mtext><ib:mtext> </ib:mtext><ib:mi>nb</ib:mi></ib:mrow></ib:math> and <pb:math xmlns:pb="http://www.w3.org/1998/Math/MathML" display="inline"><pb:msubsup><pb:mi>σ</pb:mi><pb:mi>DPS</pb:mi><pb:mrow><pb:mi>p</pb:mi><pb:mi>Pb</pb:mi><pb:mo stretchy="false">→</pb:mo><pb:mrow><pb:mi>J</pb:mi><pb:mo>/</pb:mo><pb:mi>ψ</pb:mi></pb:mrow><pb:mrow><pb:mi>J</pb:mi><pb:mo>/</pb:mo><pb:mi>ψ</pb:mi></pb:mrow><pb:mo>+</pb:mo><pb:mrow><pb:mi>X</pb:mi></pb:mrow></pb:mrow></pb:msubsup><pb:mo>=</pb:mo><pb:mn>5.4</pb:mn><pb:mo>±</pb:mo><pb:mn>6.2</pb:mn><pb:mo stretchy="false">(</pb:mo><pb:mi>stat</pb:mi><pb:mo stretchy="false">)</pb:mo><pb:mo>±</pb:mo><pb:mn>0.4</pb:mn><pb:mo stretchy="false">(</pb:mo><pb:mi>syst</pb:mi><pb:mo stretchy="false">)</pb:mo><pb:mtext> </pb:mtext><pb:mtext> </pb:mtext><pb:mi>nb</pb:mi></pb:math>, respectively. This latter result can be transformed into a lower bound on the effective DPS cross section, closely related to the squared average interparton transverse separation in the collision, of <wb:math xmlns:wb="http://www.w3.org/1998/Math/MathML" display="inline"><wb:msub><wb:mi>σ</wb:mi><wb:mi>eff</wb:mi></wb:msub><wb:mo>></wb:mo><wb:mn>1.0</wb:mn><wb:mtext> </wb:mtext><wb:mtext> </wb:mtext><wb:mi>mb</wb:mi></wb:math> at 95% confidence level. © 2024 CERN, for the CMS Collaboration 2024 CERN
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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 | 0.009 | 0.009 |
| Meta-epidemiology (narrow) | 0.005 | 0.009 |
| Meta-epidemiology (broad) | 0.002 | 0.011 |
| Bibliometrics | 0.002 | 0.008 |
| Science and technology studies | 0.007 | 0.008 |
| Scholarly communication | 0.007 | 0.007 |
| Open science | 0.010 | 0.010 |
| Research integrity | 0.008 | 0.009 |
| Insufficient payload (model declined to judge) | 0.442 | 0.014 |
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; both teacher heads agree on what is shown here.
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".