Inclusive e+e− production in collisions of pions with protons and nuclei in the second resonance region of baryons

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F61389005%3A_____%2F25%3A00619781" target="_blank" >RIV/61389005:_____/25:00619781 - isvavai.cz</a>

Výsledek na webu

<a href="https://journals.aps.org/prc/abstract/10.1103/PhysRevC.111.024908" target="_blank" >https://journals.aps.org/prc/abstract/10.1103/PhysRevC.111.024908</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1103/PhysRevC.111.024908" target="_blank" >10.1103/PhysRevC.111.024908</a>

Jazyk výsledku

angličtina

Název v původním jazyce

Inclusive e+e− production in collisions of pions with protons and nuclei in the second resonance region of baryons

Popis výsledku v původním jazyce

Inclusive e(+) e(-) production has been studied with HADES in pi(-) + p, pi(-) + C, and pi(-) + CH2 reactions, using the GSI pion beam at root s(pi p) = 1.49 GeV. Invariant mass and transverse momentum distributions have been measured and reveal contributions from Dalitz decays of pi(0), eta mesons, and baryon resonances. The transverse momentum distributions are very sensitive to the underlying kinematics of the various processes. The baryon contribution exhibits a deviation up to a factor seven from the QED reference expected for the dielectron decay of a hypothetical pointlike baryon with the production cross section constrained from the inverse gamma n -> pi(-) p reaction. The enhancement is attributed to a strong four-momentum squared dependence of the timelike electromagnetic transition form factors as suggested by vector meson dominance (VMD). Two versions of the VMD that differ in the photon-baryon coupling have been applied in simulations and compared to data. VMD1 (or two-component VMD) assumes a coupling via the rho meson and a direct coupling of the photon, while in VMD2 (or strict VMD) the coupling is only mediated via the rho meson. The VMD2 model, frequently used in transport calculations for dilepton decays, is found to overestimate the measured dielectron yields, while a good description of the data can be obtained with the VMD1 model assuming no phase difference between the two amplitudes. Similar descriptions have also been obtained using a timelike baryon transition form factor model where the pion cloud plays the major role.

Název v anglickém jazyce

Inclusive e+e− production in collisions of pions with protons and nuclei in the second resonance region of baryons

Popis výsledku anglicky

Inclusive e(+) e(-) production has been studied with HADES in pi(-) + p, pi(-) + C, and pi(-) + CH2 reactions, using the GSI pion beam at root s(pi p) = 1.49 GeV. Invariant mass and transverse momentum distributions have been measured and reveal contributions from Dalitz decays of pi(0), eta mesons, and baryon resonances. The transverse momentum distributions are very sensitive to the underlying kinematics of the various processes. The baryon contribution exhibits a deviation up to a factor seven from the QED reference expected for the dielectron decay of a hypothetical pointlike baryon with the production cross section constrained from the inverse gamma n -> pi(-) p reaction. The enhancement is attributed to a strong four-momentum squared dependence of the timelike electromagnetic transition form factors as suggested by vector meson dominance (VMD). Two versions of the VMD that differ in the photon-baryon coupling have been applied in simulations and compared to data. VMD1 (or two-component VMD) assumes a coupling via the rho meson and a direct coupling of the photon, while in VMD2 (or strict VMD) the coupling is only mediated via the rho meson. The VMD2 model, frequently used in transport calculations for dilepton decays, is found to overestimate the measured dielectron yields, while a good description of the data can be obtained with the VMD1 model assuming no phase difference between the two amplitudes. Similar descriptions have also been obtained using a timelike baryon transition form factor model where the pion cloud plays the major role.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10303 - Particles and field physics

Projekt

Výsledek vznikl pri realizaci vícero projektů. Více informací v záložce Projekty.

Návaznosti

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2025

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Physical Review C

ISSN

2469-9985

e-ISSN

2469-9993

Svazek periodika

111

Číslo periodika v rámci svazku

2

Stát vydavatele periodika

US - Spojené státy americké

Počet stran výsledku

13

Strana od-do

0204908

Kód UT WoS článku

001459938300001

EID výsledku v databázi Scopus

2-s2.0-85219705384