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Exclusive photoproduction of excited ρ mesons decaying to four pions in ultraperipheral Pb–Pb collisions at √sNN = 5.02 TeV

Acharya, S. ; Basu, S. LU orcid ; Christiansen, P. LU ; Hansen, J. LU orcid ; Iversen, K.E. LU orcid ; Matonoha, O. LU ; Nepeivoda, R. LU orcid ; Ohlson, A. LU ; Silvermyr, D. LU orcid and Staa, J. LU , et al. (2026) In Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 872.
Abstract
The intense photon fluxes from relativistic nuclei provide an opportunity to study photonuclear interactions in ultraperipheral collisions. In particular, it allows for the investigations of excited, light-flavour vector mesons. The measurement of coherently photoproduced π+π−π+π− final states in ultraperipheral Pb–Pb collisions at sNN=5.02 TeV is presented for the first time. The cross section, d σ /d y , times the branching ratio (ρ→π+π+π−π−) is found to be 47.8 ± 2.3 (stat.) ± 7.7 (syst.) mb in the rapidity interval | y | < 0.5. The invariant mass distribution is not well described with a single Breit-Wigner resonance without an interference term. Including interference with a non-resonant contribution results in the mass and width... (More)
The intense photon fluxes from relativistic nuclei provide an opportunity to study photonuclear interactions in ultraperipheral collisions. In particular, it allows for the investigations of excited, light-flavour vector mesons. The measurement of coherently photoproduced π+π−π+π− final states in ultraperipheral Pb–Pb collisions at sNN=5.02 TeV is presented for the first time. The cross section, d σ /d y , times the branching ratio (ρ→π+π+π−π−) is found to be 47.8 ± 2.3 (stat.) ± 7.7 (syst.) mb in the rapidity interval | y | < 0.5. The invariant mass distribution is not well described with a single Breit-Wigner resonance without an interference term. Including interference with a non-resonant contribution results in the mass and width values being too far from those reported in PDG, while the production of two interfering resonances, ρ (1450) and ρ (1700), also provides a good description of the data. The values of the masses ( m ) and widths (Γ) of the resonances extracted from the fit assuming two interfering resonances are m1=1385±14(stat.)±3(syst.) MeV/ c 2, Γ1=431±36(stat.)±82(syst.) MeV/ c 2, m2=1663±13(stat.)±22(syst.) MeV/ c 2 and Γ2=357±31(stat.)±49(syst.) MeV/ c 2, respectively. The measured cross sections times the branching ratios are compared to recent theoretical predictions. Copyright © 2025. Published by Elsevier B.V. (Less)
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type
Contribution to journal
publication status
published
subject
keywords
Exclusive photoproduction, Ultraperipheral collisions, Vector mesons
in
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
volume
872
article number
140006
publisher
Elsevier
external identifiers
  • scopus:105024317699
ISSN
0370-2693
DOI
10.1016/j.physletb.2025.140006
language
English
LU publication?
yes
id
e0a0c13a-dc1f-4449-ad3a-1f9315c46ae1
date added to LUP
2026-04-07 15:27:12
date last changed
2026-04-07 15:28:25
@article{e0a0c13a-dc1f-4449-ad3a-1f9315c46ae1,
  abstract     = {{The intense photon fluxes from relativistic nuclei provide an opportunity to study photonuclear interactions in ultraperipheral collisions. In particular, it allows for the investigations of excited, light-flavour vector mesons. The measurement of coherently photoproduced π+π−π+π− final states in ultraperipheral Pb–Pb collisions at sNN=5.02 TeV is presented for the first time. The cross section, d σ /d y , times the branching ratio (ρ→π+π+π−π−) is found to be 47.8 ± 2.3 (stat.) ± 7.7 (syst.) mb in the rapidity interval | y | &lt; 0.5. The invariant mass distribution is not well described with a single Breit-Wigner resonance without an interference term. Including interference with a non-resonant contribution results in the mass and width values being too far from those reported in PDG, while the production of two interfering resonances, ρ (1450) and ρ (1700), also provides a good description of the data. The values of the masses ( m ) and widths (Γ) of the resonances extracted from the fit assuming two interfering resonances are m1=1385±14(stat.)±3(syst.) MeV/ c 2, Γ1=431±36(stat.)±82(syst.) MeV/ c 2, m2=1663±13(stat.)±22(syst.) MeV/ c 2 and Γ2=357±31(stat.)±49(syst.) MeV/ c 2, respectively. The measured cross sections times the branching ratios are compared to recent theoretical predictions. Copyright © 2025. Published by Elsevier B.V.}},
  author       = {{Acharya, S. and Basu, S. and Christiansen, P. and Hansen, J. and Iversen, K.E. and Matonoha, O. and Nepeivoda, R. and Ohlson, A. and Silvermyr, D. and Staa, J. and Vislavicius, V. and Zurlo, N.}},
  issn         = {{0370-2693}},
  keywords     = {{Exclusive photoproduction; Ultraperipheral collisions; Vector mesons}},
  language     = {{eng}},
  publisher    = {{Elsevier}},
  series       = {{Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics}},
  title        = {{Exclusive photoproduction of excited ρ mesons decaying to four pions in ultraperipheral Pb–Pb collisions at √s<sub>NN</sub> = 5.02 TeV}},
  url          = {{http://dx.doi.org/10.1016/j.physletb.2025.140006}},
  doi          = {{10.1016/j.physletb.2025.140006}},
  volume       = {{872}},
  year         = {{2026}},
}