Measurement of angular correlations inside jets induced by gluon polarization in proton-proton collisions at $\sqrt{s}$ = 13.6 TeV

Abstract

A study of angular correlations inside jets induced by gluon polarization is performed using proton-proton collisions at a center-of-mass energy of $\sqrt{s}$ = 13.6 TeV. The data correspond to an integrated luminosity of 34.7 fb$^{-1}$, collected in 2022 with the CMS detector at the LHC. The details of the parton shower are investigated using jets reconstructed with the anti-$k_\mathrm{T}$ algorithm and subsequently declustered with the Cambridge$-$Aachen algorithm. A novel analysis technique is developed to identify characteristic features of the jet substructure and to select intermediate gluon splittings into quark-antiquark pairs. An observable sensitive to gluon polarization in the parton shower is measured and compared with PYTHIA 8 and HERWIG 7 model predictions, with and without angular correlations induced by the gluon spin. The results are consistent with models that incorporate gluon polarization and strongly disfavor those that neglect them.

Figures (3)

• Figure 1: Distribution of the DNN output score, before reweighting, for a jet identified in the ${ \mathup{{{q}}{} _{ {}} ^{ {}}} }\xspace{ \mathup{{ \overline{ {{ \mathup{{{q}}{} _{ {}} ^{ {}}} }\xspace}}}{} _{ {}} ^{ {}}} }\xspace$ class in inclusive events (i.e., before any categorization) in data (black dots with error bars indicating statistical uncertainties) and in the different MC simulations (histograms, indicating different parton splitting contributions). Solid and dashed lines represent correlation-on and -off models, respectively. The lower panel shows the ratio of data and various MC models over the pythia 8 correlation-off prediction.
• Figure 2: Reconstructed $\Delta\varphi$ distributions in data (black dots with error bars indicating statistical uncertainties) and MC simulations (histograms, indicating different parton splitting contributions) for the inclusive sample (upper), and in the ${ \mathup{{{q}}{} _{ {}} ^{ {}}} }\xspace{ \mathup{{ \overline{ {{ \mathup{{{q}}{} _{ {}} ^{ {}}} }\xspace}}}{} _{ {}} ^{ {}}} }\xspace$ category with $\text{score}_{{ \mathup{{{g}}{} _{ {}} ^{ {}}} }\xspace\to{ \mathup{{{q}}{} _{ {}} ^{ {}}} }\xspace{ \mathup{{ \overline{ {{ \mathup{{{q}}{} _{ {}} ^{ {}}} }\xspace}}}{} _{ {}} ^{ {}}} }\xspace\xspace\xspace}\xspace > 0.6$ (lower). The ${ \mathup{{{q}}{} _{ {}} ^{ {}}} }\xspace,{ \mathup{{{g}}{} _{ {}} ^{ {}}} }\xspace$ composition breakdown is shown for the herwig simulation. The lower panels show the ratio of the data to the pythia 8 correlation-off prediction. Systematic uncertainties are shown as gray hatched bands.
• Figure 3: Unfolded $\Delta\varphi$ distribution in events of the ${ \mathup{{{q}}{} _{ {}} ^{ {}}} }\xspace{ \mathup{{ \overline{ {{ \mathup{{{q}}{} _{ {}} ^{ {}}} }\xspace}}}{} _{ {}} ^{ {}}} }\xspace$ category with $\text{score}_{{ \mathup{{{g}}{} _{ {}} ^{ {}}} }\xspace\to{ \mathup{{{q}}{} _{ {}} ^{ {}}} }\xspace{ \mathup{{ \overline{ {{ \mathup{{{q}}{} _{ {}} ^{ {}}} }\xspace}}}{} _{ {}} ^{ {}}} }\xspace\xspace\xspace}\xspace > 0.6$ in data (black dots with error bars indicating statistical uncertainties) compared with pythia 8 and herwig 7 correlation-on predictions (histograms) passing the event selection described in the text. The lower panel shows the ratio of the data and the herwig (correlation-on) model over the pythia 8 correlation-on prediction. Systematic uncertainties are shown as gray hatched bands.