Photoproduction of 𝐾+𝐾− Pairs in Ultraperipheral Collisions

Scientific paper - Original scientific paper

• Author: S. Acharya
• Author: ...
• Author: Sven Gotovac
• Author: ...
• Author: David Karatović
• Author: ...
• Author: Nino Kovačić
• Author: ...
• Author: Petra Lončar
• Author: ...
• Author: Mirko Planinić
• Author: ...
• Author: Nikola Poljak
• Author: ...
• Author: Linda Vicković
• Author: ...
• Author: N. Zurlo
• Collaboration: ALICE Collaboration
• Author's institution: University of Zagreb; Faculty of Science; (Department of Physics)
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Physics

Abstract (english)

𝐾+𝐾− pairs may be produced in photonuclear collisions, either from the decays of photoproduced 𝜙⁡(1020) mesons or directly as nonresonant 𝐾+𝐾− pairs. Measurements of 𝐾+𝐾− photoproduction probe the couplings between the 𝜙⁡(1020) and charged kaons with photons and nuclear targets. The kaon-proton scattering occurs at energies far above those available elsewhere. We present the first measurement of coherent photoproduction of 𝐾+𝐾− pairs on lead ions in ultraperipheral collisions using the ALICE detector, including the first investigation of direct 𝐾+𝐾− production. There is significant 𝐾+𝐾− production at low transverse momentum, consistent with coherent photoproduction on lead targets. In the mass range 1.1<𝑀𝐾𝐾<1.4  GeV/𝑐2 above the 𝜙⁡(1020) resonance, for rapidity |𝑦𝐾𝐾|<0.8 and 𝑝𝑇,𝐾𝐾<0.1  GeV/𝑐, the measured coherent photoproduction cross section is d𝜎/d𝑦=3.37±0.61(stat)±0.15(syst)  mb. The center-of-mass energy per nucleon of the photon-nucleus (Pb) system 𝑊𝛾Pb,𝑛 ranges from 33 to 188 GeV, far higher than previous measurements on heavy-nucleus targets. The cross section is larger than expected for 𝜙⁡(1020) photoproduction alone. The mass spectrum is fit to a cocktail consisting of 𝜙⁡(1020) decays, direct 𝐾+𝐾− photoproduction, and interference between the two. The confidence regions for the amplitude and relative phase angle for direct 𝐾+𝐾− photoproduction are presented.

• Keywords (english): photoproduction; ultraperipheral collisions
• Language: english
• Publication type: Scientific paper - Original scientific paper
• Publication status: Published
• Peer review: Peer review - international
• Publication version: Published version
• Journal title: Physical Review Letters
• Numbering: vol. 132, no. 22, 222303
• p-ISSN: 0031-9007
• e-ISSN: 1079-7114
• DOI: https://doi.org/10.1103/PhysRevLett.132.222303
• URN:NBN: urn:nbn:hr:217:096140
• Publication: 2024
• Document URL: https://link.aps.org/doi/10.1103/PhysRevLett.132.222303
• Type of resource: Text
• Access conditions: Open access
• Public note: © 2024 CERN, for the ALICE Collaboration. Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Open access publication funded by CERN. Received 8 December 2023; revised 16 February 2024; accepted 3 May 2024; published 31 May 2024.
• Created on: 2024-09-13 13:05:25