Photon-Tagged Energy Flow in Inclusive Endpoint B Decays
Abstract
We introduce a B-decay tagged energy correlator (BTEC) to resolve the angular structure of energy flow in inclusive B decays in the endpoint region, focusing on the direct-photon contribution to B̅→ Xsγ. At leading power and at the natural collinear angular scale τ∼ s∼ QΛQCD, we derive a factorization relation involving the standard hard coefficient and B-meson shape function together with a new measured quark jet function; no new leading-power nonperturbative function is introduced. We calculate the measured jet function at one-loop accuracy and verify that its angular integral reproduces the standard inclusive quark jet function. For the central Bosch--Lange--Neubert--Paz parameter set, an illustrative benchmark gives 3 − 16% migration outside the fixed angular cuts τc=2 − 4 GeV2. With an independently constrained shape function, the angular cumulatives provide a closure test of leading-power endpoint factorization and are sensitive to direct-O7 power corrections and resolved-photon effects. The BTEC thereby adds information on the angular structure of the inclusive recoil jet beyond the ordinary photon spectrum and may improve signal--background discrimination when their energy-flow profiles differ.
Versions
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BibTeX
@misc{zhao2026photontagged,
title = {{Photon-Tagged Energy Flow in Inclusive Endpoint $B$ Decays}},
author = {Shuai Zhao},
howpublished = {arXiv},
year = {2026},
month = jul,
doi = {10.48550/arxiv.2607.27367},
eprint = {2607.27367},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2607.27367},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Photon-Tagged Energy Flow in Inclusive Endpoint B Decays
AU - Shuai Zhao
PY - 2026
DA - 2026/07/29
PB - arXiv
DO - 10.48550/arxiv.2607.27367
UR - https://arxiv.org/abs/2607.27367
AB - We introduce a B-decay tagged energy correlator (BTEC) to resolve the angular structure of energy flow in inclusive B decays in the endpoint region, focusing on the direct-photon contribution to B̅→ X_sγ. At leading power and at the natural collinear angular scale τ∼ s∼ QΛ_QCD, we derive a factorization relation involving the standard hard coefficient and B-meson shape function together with a new measured quark jet function; no new leading-power nonperturbative function is introduced. We calculate the measured jet function at one-loop accuracy and verify that its angular integral reproduces the standard inclusive quark jet function. For the central Bosch--Lange--Neubert--Paz parameter set, an illustrative benchmark gives 3 − 16% migration outside the fixed angular cuts τ_c=2 − 4 GeV^2. With an independently constrained shape function, the angular cumulatives provide a closure test of leading-power endpoint factorization and are sensitive to direct-O_7 power corrections and resolved-photon effects. The BTEC thereby adds information on the angular structure of the inclusive recoil jet beyond the ordinary photon spectrum and may improve signal--background discrimination when their energy-flow profiles differ.
ER -