In:
Physical Review Letters, American Physical Society (APS), Vol. 132, No. 22 ( 2024-5-31)
Abstract:
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 〈 M K K 〈 1.4 GeV / c 2 above the ϕ ( 1020 ) resonance, for rapidity | y K K | 〈 0.8 and p T , K K 〈 0.1 GeV / c , the measured coherent photoproduction cross section is d σ / d y = 3.37 ± 0.61 ( stat ) ± 0.15 ( syst ) mb . The center-of-mass energy per nucleon of the photon-nucleus (Pb) system W γ Pb , 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. © 2024 CERN, for the ALICE Collaboration 2024 CERN
Type of Medium:
Online Resource
ISSN:
0031-9007
,
1079-7114
DOI:
10.1103/PhysRevLett.132.222303
Language:
English
Publisher:
American Physical Society (APS)
Publication Date:
2024
detail.hit.zdb_id:
1472655-5
detail.hit.zdb_id:
208853-8
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