Causal-horizon scaling of prompt X(3872) formation lengths
Abstract
We use conventional charmonium as a spatial ruler for the correlations accessed in prompt X(3872) formation. In a Gaussian source model, averaging an early phase field over an exponential causal-horizon ensemble gives a leading formation loss linear in the sampled length. Comparing the changes of two adjacent production ratios removes the common field strength, horizon scale and exposure. Potential-model charmonium separation lengths then calibrate the remaining length gaps. Matched LHCb measurements at 13 TeV give, for a common source and a direct J/psi reference, a central lower X(3872) formation profile scale of about 1.3 fm and a central lower prepared source scale of about 0.65 fm. An arbitrarily compact common source cannot reproduce the observed difference simply by increasing the final profile. These formation constraints permit an arbitrarily long final-state tail. A fixed proper-exposure rule is separately tested against conventional-charmonium activity data and prompt X(3872)/psi(2S) jet shapes. Prompt feed-down and relative production changes quantify the sensitivity of the extraction. A matched activity measurement of all three states tests the inferred spatial ordering.
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BibTeX
@misc{yang2026causalhorizon,
title = {{Causal-horizon scaling of prompt X(3872) formation lengths}},
author = {Yi Yang},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.22424},
eprint = {2610.22424},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.22424},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - Causal-horizon scaling of prompt X(3872) formation lengths
AU - Yi Yang
PY - 2026
DA - 2026/10/15
PB - arXiv
DO - 10.48550/arxiv.2610.22424
UR - https://arxiv.org/abs/2610.22424
AB - We use conventional charmonium as a spatial ruler for the correlations accessed in prompt X(3872) formation. In a Gaussian source model, averaging an early phase field over an exponential causal-horizon ensemble gives a leading formation loss linear in the sampled length. Comparing the changes of two adjacent production ratios removes the common field strength, horizon scale and exposure. Potential-model charmonium separation lengths then calibrate the remaining length gaps. Matched LHCb measurements at 13 TeV give, for a common source and a direct J/psi reference, a central lower X(3872) formation profile scale of about 1.3 fm and a central lower prepared source scale of about 0.65 fm. An arbitrarily compact common source cannot reproduce the observed difference simply by increasing the final profile. These formation constraints permit an arbitrarily long final-state tail. A fixed proper-exposure rule is separately tested against conventional-charmonium activity data and prompt X(3872)/psi(2S) jet shapes. Prompt feed-down and relative production changes quantify the sensitivity of the extraction. A matched activity measurement of all three states tests the inferred spatial ordering.
ER -