Pion pair production in $e^+ e^-$ annihilation at next-to-leading order matched to Parton Shower

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Autori principali: Budassi, E., Calame, C. M. Carloni, Ghilardi, M., Gurgone, A., Montagna, G., Moretti, M., Nicrosini, O., Piccinini, F., Ucci, F. P.
Natura: Preprint
Pubblicazione: 2024
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author Budassi, E.
Calame, C. M. Carloni
Ghilardi, M.
Gurgone, A.
Montagna, G.
Moretti, M.
Nicrosini, O.
Piccinini, F.
Ucci, F. P.
author_facet Budassi, E.
Calame, C. M. Carloni
Ghilardi, M.
Gurgone, A.
Montagna, G.
Moretti, M.
Nicrosini, O.
Piccinini, F.
Ucci, F. P.
contents The pion pair production in $e^+ e^-$ annihilation at flavour factories plays a crucial role in the determination of the hadronic contribution to the muon anomalous magnetic moment. The recent CMD-3 measurement of the pion form factor via energy scan displays a significant difference with the previous experimental determinations. In order to contribute to an improved theoretical description and simulation of energy scan experiments, we present a calculation of the $e^+ e^- \to π^+ π^- (γ)$ hadronic channel at next-to-leading order matched to a Parton Shower algorithm in QED and sQED. According to the recent advances in the literature, particular attention is paid to the treatment of the pion composite structure in loop diagrams beyond the commonly used factorised sQED approach, as well as to the modelling of multiple photon radiation through the Parton Shower algorithm. In particular, we carry out a detailed discussion on the inclusion of the pion form factor in the virtual sQED corrections according to two independent methods, inspired by the generalised vector meson dominance model and the dispersive approach, respectively. We find the two methods to be in remarkable agreement. We show phenomenological results for inclusive and differential observables which are relevant for precision energy scan measurements, focusing on the impact of the radiative corrections and the effect of the various approaches for the treatment of the pion form factor. Our calculation is implemented in an updated version of the Monte Carlo event generator BabaYaga@NLO, that can be used for fully exclusive simulations in data analysis.
format Preprint
id arxiv_https___arxiv_org_abs_2409_03469
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Pion pair production in $e^+ e^-$ annihilation at next-to-leading order matched to Parton Shower
Budassi, E.
Calame, C. M. Carloni
Ghilardi, M.
Gurgone, A.
Montagna, G.
Moretti, M.
Nicrosini, O.
Piccinini, F.
Ucci, F. P.
High Energy Physics - Phenomenology
High Energy Physics - Experiment
The pion pair production in $e^+ e^-$ annihilation at flavour factories plays a crucial role in the determination of the hadronic contribution to the muon anomalous magnetic moment. The recent CMD-3 measurement of the pion form factor via energy scan displays a significant difference with the previous experimental determinations. In order to contribute to an improved theoretical description and simulation of energy scan experiments, we present a calculation of the $e^+ e^- \to π^+ π^- (γ)$ hadronic channel at next-to-leading order matched to a Parton Shower algorithm in QED and sQED. According to the recent advances in the literature, particular attention is paid to the treatment of the pion composite structure in loop diagrams beyond the commonly used factorised sQED approach, as well as to the modelling of multiple photon radiation through the Parton Shower algorithm. In particular, we carry out a detailed discussion on the inclusion of the pion form factor in the virtual sQED corrections according to two independent methods, inspired by the generalised vector meson dominance model and the dispersive approach, respectively. We find the two methods to be in remarkable agreement. We show phenomenological results for inclusive and differential observables which are relevant for precision energy scan measurements, focusing on the impact of the radiative corrections and the effect of the various approaches for the treatment of the pion form factor. Our calculation is implemented in an updated version of the Monte Carlo event generator BabaYaga@NLO, that can be used for fully exclusive simulations in data analysis.
title Pion pair production in $e^+ e^-$ annihilation at next-to-leading order matched to Parton Shower
topic High Energy Physics - Phenomenology
High Energy Physics - Experiment
url https://arxiv.org/abs/2409.03469