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Ahammed, Z.; Ahmad, S.; Alfanda, H. M.; Alocco, G.; Anaam, M. N.; Andreou, N.; Apadula, N.; Appelshäuser, H.; Aresti, M.; Baek, Y. W.; Bailhache, R.; Balbino, A.; Beattie, C.; Bergmann, L.; Besoiu, M. G.; Biro, G.; Borissov, A.; Botta, E.; Buesching, H.; Calvo Villar, E.; Canedo, F. D. M.; Ceballos Sanchez, C.; Chandra, S.; Cheng, T.; Christensen, C. H.; Concas, M.; Diab, B.; Ding, Y.; Erazmus, B.; Faivre, J.; Ferrer, M. B.; Feuillard, V. J. G.; Foertsch, S.; Gago, A. M.; Gangadharan, D. R.; Giubellino, P.; Glässel, P.; Grosse-Oetringhaus, J. F.; Grunwald, N. A.; Hamdi, A.; Hassan, H.; Hofman, B.; Ilyas, H.; Jacazio, N.; Jakubowska, M. J.; Jung, M.; Karpechev, E.; Kozhuharov, V.; Kumar, N.; Kurepin, A.; Kurepin, A. B.; Lee, H.; Lim, B.; Lokos, S.; Maire, A.; Massen, O.; Mendez, J. E. M.; Mikhaylov, K.; Mulliri, A.; Nappi, E.; Nath, A.; Park, H.; Pennisi, M.; Petrov, V.; Płoskoń, M.; Pozdniakov, V.; Pruneau, C. A.; Pshenichnov, I.; Ramello, L.; Reme-Ness, H. A.; Riffero, A. G.; Rodríguez Ramírez, S. A.; Roy, S.; Russek, P. G.; Saha, P.; Scapparone, E.; Schmah, A.; Shatat, A.; Shin, J.; Song, J.; Sputowska, I.; Staa, J.; Stiefelmaier, S. F.; Stratmann, P.; Sturniolo, A.; Tejeda Muñoz, G.; Valle, N.; van Doremalen, L. V. R.; Verma, R.; Verweij, M.; Vodopyanov, A.; Volkel, B.; Vrláková, J.; Wan, J.; Willems, G. A.; Windelband, B.; Xu, R.; Zarochentsev, A.; Zhang, S.; Zhou, Y.
Physical review letters, 05/2024, Volume: 132, Issue: 22Journal Article
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
