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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Constraining hadronization mechanisms with Λ c + / D 0 production ratios in Pb–Pb collisions at s NN = 5.02 TeV

The production of prompt $\ Λ^{+}_{c}$ baryons at midrapidity (|y|<0.5) was measured in central (0–10%) and mid-central (30–50%) Pb–Pb collisions at the center-of-mass energy per nucleon–nucleon pair $\sqrt{s_{NN}}$ TeV with the ALICE detector. The results are more precise, more differential in centrality, and reach much lower transverse momentum (p T =1 GeV/c) with respect to previous measurements performed by the ALICE, STAR, and CMS Collaborations in nucleus–nucleus collisions, allowing for an extrapolation down to p T =0. The p T -differential $\ Λ^{+}_{c}$/D 0 ratio is enhanced with respect to the pp measurement for 4 < p T < 8 GeV/c by 3.7 standard deviations (σ), while the p T -integrated ratios are compatible within 1σ. The observed trend is similar to that observed in the strange sector for the Λ/$\ K^{0}_{S}$ ratio. Model calculations including coalescence or statistical hadronization for charm-hadron formation are compared with the data.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Measurements of inclusive J/ψ production at midrapidity and forward rapidity in Pb–Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV

The measurements of the inclusive J/ψ yield at midrapidity (|y| < 0.9) and forward rapidity (2.5 < y < 4) in Pb–Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV with the ALICE detector at the LHC are reported. The inclusive J/ψ production yields and nuclear modification factors, R AA , are measured as a function of the collision centrality, J/ψ transverse momentum (p T ), and rapidity. The J/ψ average transverse momentum and squared transverse momentum ($\langle$p T $\rangle$ and $\langle$$p^{2}_{T}$$\rangle$) are evaluated as a function of the centrality at midrapidity. Compared to the previous ALICE publications, here the entire Pb–Pb collisions dataset collected during the LHC Run 2 is used, which improves the precision of the measurements and extends the p T coverage. The p T -integrated R AA shows a hint of an increasing trend towards unity from semicentral to central collisions at midrapidity, while it is flat at forward rapidity. The p T -differential R AA shows a strong suppression at high p T with less suppression at low p T where it reaches a larger value at midrapidity compared to forward rapidity. The ratio of the p T -integrated yields of J/ψ to those of D 0 mesons is reported for the first time for the central and semicentral event classes at midrapidity. Model calculations implementing charmonium production via the coalescence of charm quarks and antiquarks during the fireball evolution (transport models) or in a statistical approach with thermal weights are in good agreement with the data at low p T . At higher p T , the data are well described by transport models and a model based on energy loss in the strongly-interacting medium produced in nuclear collisions at the LHC.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Coherent J/ψ photoproduction at midrapidity in Pb – Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV

The coherent J∕𝜓 photoproduction cross section is measured for the first time at midrapidity in peripheral to semicentral P b − P b collisions at $\sqrt{s_{NN}}$ = 5.02 TeV. The centrality differential cross section d 𝜎 ∕d𝑦 is reported for the centrality range 40–90%, together with the doubly-differential cross section d 2 𝜎∕d𝑦d𝑝 T , extracted in two peripheral centrality classes. The J∕𝜓 mesons are reconstructed in the dielectron channel, in the rapidity interval |𝑦| < 0.9 using the ALICE central barrel detectors. The J∕𝜓 cross section at midrapidity is statistically compatible to the earlier ALICE measurement at forward rapidity and at the same centre-of-mass energy, and shows only a mild centrality dependence over the covered range. Several sets of theoretical calculations taking into account the hadronic overlap in the collisions but ignoring possible final-state effects from a hot expanding medium are found to give a fairly good description of the current measurements within uncertainties.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

An upper bound on the second order asymptotic expansion for the quantum communication cost of state redistribution

State redistribution is the protocol in which given an arbitrary tripartite quantum state, with two of the subsystems initially being with Alice and one being with Bob, the goal is for Alice to send one of her subsystems to Bob, possibly with the help of prior shared entanglement. We derive an upper bound on the second order asymptotic expansion for the quantum communication cost of achieving state redistribution with a given finite accuracy. In proving our result, we also obtain an upper bound on the quantum communication cost of this protocol in the one-shot setting, by using the protocol of coherent state merging as a primitive.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

Vector meson photoproduction in UPCs with FoCal

Abstract We discuss the physics prospects of photon-induced measurements using the high-granularity FoCal detector to be installed at the ALICE experiment, covering the pseudorapidity interval 3.4 ≤ η ≤ 5.8. This new detector, scheduled to be in operation from Run 4, will explore the small Bjorken- x physics region in an unprecedented way. In this region the gluon ,saturation phenomenon is expected to be dominant. Combined with the rest of the ALICE subdetectors, including the zero degree calorimenters, FoCal will serve to reconstruct in a model-independent way the measured photoproduction cross sections for vectors mesons in a wide range of photon-target energies, down to x values of about 7 × 10 −6 and 2 × 10 −6 in ultra-peripheral photon–proton and photon–lead collisions, respectively.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

Next Generation Workload Management System For Big Data on Heterogeneous Distributed Computing

The Large Hadron Collider (LHC), operating at the international CERN Laboratory in Geneva, Switzerland, is leading Big Data driven scientific explorations. Experiments at the LHC explore the fundamental nature of matter and the basic forces that shape our universe, and were recently credited for the discovery of a Higgs boson. ATLAS and ALICE are the largest collaborations ever assembled in the sciences and are at the forefront of research at the LHC. To address an unprecedented multi-petabyte data processing challenge, both experiments rely on a heterogeneous distributed computational infrastructure. The ATLAS experiment uses PanDA (Production and Data Analysis) Workload Management System (WMS) for managing the workflow for all data processing on hundreds of data centers. Through PanDA, ATLAS physicists see a single computing facility that enables rapid scientific breakthroughs for the experiment, even though the data centers are physically scattered all over the world. The scale is demonstrated by the following numbers: PanDA manages O(10 2 ) sites, O(10 5 ) cores, O(10 8 ) jobs per year, O(10 3 ) users, and ATLAS data volume is O(10 17 ) bytes. In 2013 we started an ambitious program to expand PanDA to all available computing resources, including opportunistic use of commercial and academic clouds and Leadership Computing Facilities (LCF). The project titled 'Next Generation Workload Management and Analysis System for Big Data' (BigPanDA) is funded by DOE ASCR and HEP. Extending PanDA to clouds and LCF presents new challenges in managing heterogeneity and supporting workflow. The BigPanDA project is underway to setup and tailor PanDA at the Oak Ridge Leadership Computing Facility (OLCF) and at the National Research Center "Kurchatov Institute" together with ALICE distributed computing and ORNL computing professionals. Our approach to integration of HPC platforms at the OLCF and elsewhere is to reuse, as much as possible, existing components of the PanDA system. Finally, we will present our current accomplishments with running the PanDA WMS at OLCF and other supercomputers and demonstrate our ability to use PanDA as a portal independent of the computing facilities infrastructure for High Energy and Nuclear Physics as well as other data-intensive science applications.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2025

𝐷 0 -meson-tagged jet axes difference in proton-proton collisions at $\sqrt{s}$ = 5.02 TeV

Heavy-flavor quarks produced in proton-proton (pp) collisions provide a unique opportunity to investigate the evolution of quark-initiated parton showers from initial hard scatterings to final-state hadrons. By examining jets that contain heavy-flavor hadrons, this study explores the effects of both perturbative and nonperturbative QCD on jet formation and structure. The angular differences between various jet axes, Δ⁢𝑅 axis , offer insight into the radiation patterns and fragmentation of charm quarks. The first measurement of 𝐷 0 -tagged jet axes differences in pp collisions at $\sqrt{s}$ =5.02 TeV by the ALICE experiment at the LHC is presented for jets with transverse momentum 𝑝$^{ch jet}_{T}$ ≥ 10 GeV/𝑐 and 𝐷 0 mesons with 𝑝$^{D^0}_{T}$ ≥ 5 GeV/𝑐. In this 𝐷 0 -meson-tagged jet measurement, three jet axis definitions, each with different sensitivities to soft, wide-angle radiation, are used: the standard axis, soft drop groomed axis, and winner-takes-all axis. Measurements of the radial distributions of 𝐷 0 mesons with respect to the jet axes, Δ⁢𝑅 axis−D 0 , are reported, along with the angle, Δ⁢𝑅 axis , between the three jet axes. The 𝐷 0 meson emerges as the leading particle in these jets, closely aligning with the winner-takes-all axis and diverging from the standard jet axis. The results also examine how varying the sensitivity to soft radiation with grooming influences the orientation of the soft drop jet axis and uncover that charm-jet structure is more likely to survive grooming when the soft drop axis is further from the 𝐷 0 direction, providing further evidence of the dead-cone effect recently measured by ALICE.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

Differential two-particle number and momentum correlations with the AMPT, UrQMD, and EPOS models in Pb-Pb collisions at s N N = 2.76 TeV

We report studies of charge-independent and charge-dependent two-particle differential number correlation functions, R 2 (Δη,Δφ), and transverse momentum correlation functions, P 2 (Δη,Δφ), of charged particles produced in Pb–Pb collisions at the LHC center-of-mass energy √sNN= 2.76 TeV with the UrQMD, AMPT, and EPOS models. Model calculations for R2 and P2 correlation functions are presented for inclusive charged hadrons (h ± ) in selected transverse momentum ranges and with full azimuthal coverage in the pseudorapidity range |η|<1.0. We compare these calculations for the strength, shape, and particularly the width of the correlation functions with recent measurements of these observables by the ALICE collaboration. Our analysis indicates that comparative studies of R 2 and P 2 correlation functions provide valuable insight towards the understanding of particle production in Pb–Pb collisions. We find, in particular, that these models produce quantitatively different magnitudes and shapes for these correlation functions and none reproduce the results reported by the ALICE collaboration. Accounting for quantum number conservation in models, particularly charge conservation, is mandatory to reproduce the detailed measurements of number and transverse momentum correlation functions.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

System-size dependence of the hadronic rescattering effect at energies available at the CERN Large Hadron Collider

The first measurements of K * ( 892 ) 0 resonance production as a function of charged-particle multiplicity in Xe-Xe collisions at s N N = 5.44 TeV and p p collisions at s = 5.02 TeV using the ALICE detector are presented. The resonance is reconstructed at midrapidity ( | y | < 0.5) using the hadronic decay channel K * 0 → K ± π ∓ . Measurements of transverse-momentum integrated yield, mean transverse-momentum, nuclear modification factor of K * 0 , and yield ratios of resonance to stable hadron ( K * 0 / K ) are compared across different collision systems ( p p , p -Pb, Xe-Xe, and Pb-Pb) at similar collision energies to investigate how the production of K * 0 resonances depends on the size of the system formed in these collisions. The hadronic rescattering effect is found to be independent of the size of colliding systems and mainly driven by the produced charged-particle multiplicity, which is a proxy of the volume of produced matter at the chemical freeze-out. In addition, the production yields of K * 0 in Xe-Xe collisions are utilized to constrain the dependence of the kinetic freeze-out temperature on the system size using the hadron resonance gas–partial chemical equilibrium model. ©2024 CERN, for the ALICE Collaboration 2024 CERN

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

K ∗ (892) ± resonance production in Pb−Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV

The production of K *⁢(892) ± meson resonance is measured at midrapidity (| y |<0.5) in Pb-Pb collisions at $\sqrt{^sNN}$ = 5.02 TeV using the ALICE detector at the CERN Large Hadron Collider. The resonance is reconstructed via its hadronic decay channel K *⁢(892) ± → K $^0_S$⁢π ± . The transverse momentum distributions are obtained for various centrality intervals in the p T range of 0.4-16 GeV/ c . Measurements of integrated yields, mean transverse momenta, and particle yield ratios are reported and found to be consistent with previous ALICE measurements for K *⁢(892) 0 within uncertainties. The p T -integrated yield ratio 2 K *⁢(892) ± ⁢/(⁢ K + + K - ) in central Pb-Pb collisions shows a significant suppression at a level of 9.3σ⁢ relative to pp collisions. Thermal model calculations result in an overprediction of the particle yield ratio. Although both hadron resonance gas in partial chemical equilibrium (HRG-PCE) and MUSIC + SMASH simulations consider the hadronic phase, only HRG-PCE accurately represents the measurements, whereas MUSIC + SMASH simulations tend to overpredict the particle yield ratio. These observations, along with the kinetic freeze-out temperatures extracted from the yields measured for light-flavored hadrons using the HRG-PCE model, indicate a finite hadronic phase lifetime, which decreases with increasing collision centrality percentile. The p T-differential yield ratios 2 K *⁢(892) ±⁢ /(⁢ K + + K - ) and 2 K *⁢(892) ± ⁢/(⁢π + +π - ) are presented and compared with measurements in pp collisions at $\sqrt{s}$ = 5.02 TeV. Both particle ratios are found to be suppressed by up to a factor of five at p T <2.0 GeV/ c in central Pb-Pb collisions and are qualitatively consistent with expectations for rescattering effects in the hadronic phase. The nuclear modification factor ( R AA ) shows a smooth evolution with centrality and is found to be below unity at p T >8 GeV/ c , consistent with measurements for other light-flavored hadrons. The smallest values are observed in most central collisions, indicating larger energy loss of partons traversing the dense medium.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Systematic study of flow vector fluctuations in $\sqrt{S_{NN}}$ = 5.02 TeV Pb-Pb collisions

Measurements of the 𝑝 T -dependent flow vector fluctuations in Pb–Pb collisions at $\sqrt{S_{NN}}$ = 5.02 TeV using azimuthal correlations with the ALICE experiment at the Large Hadron Collider are presented. A four-particle correlation approach [ALICE Collaboration, Phys. Rev. C 107, L051901 (2023)] is used to quantify the effects of flow angle and magnitude fluctuations separately. This paper extends previous studies to additional centrality intervals and provides measurements of the 𝑝 T -dependent flow vector fluctuations at $\sqrt{S_{NN}}$ = 5.02 TeV with two-particle correlations. Significant 𝑝 T -dependent fluctuations of the $\vec{𝑉}$ 2 flow vector in Pb–Pb collisions are found across different centrality ranges, with the largest fluctuations of up to ∼15% being present in the 5% most central collisions. In parallel, no evidence of significant 𝑝 T -dependent fluctuations of $\vec{𝑉}$ 3 or $\vec{𝑉}$ 4 is found. Additionally, evidence of flow angle and magnitude fluctuations is observed with more than 5⁢𝜎 significance in central collisions. These observations in Pb–Pb collisions indicate where the classical picture of hydrodynamic modeling with a common symmetry plane breaks down. This has implications for hard probes at high 𝑝 T , which might be biased by 𝑝 T -dependent flow angle fluctuations of at least 23% in central collisions. Given the presented results, existing theoretical models should be reexamined to improve our understanding of initial conditions, quark–gluon plasma properties, and the dynamic evolution of the created system.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Proton emission in ultraperipheral Pb-Pb collisions at $\sqrt{𝑠_{𝑁⁢𝑁}}$ = 5.02 TeV

The first measurements of proton emission accompanied by neutron emission in the electromagnetic dissociation (EMD) of 208 Pb nuclei in the ALICE experiment at the Large Hadron Collider are presented. The EMD protons and neutrons emitted at very forward rapidities are detected by the proton and neutron zero degree calorimeters of the ALICE experiment. The emission cross sections of zero, one, two, and three protons accompanied by at least one neutron were measured in ultraperipheral 208 Pb − 208 Pb collisions at a center-of-mass energy per nucleon pair $\sqrt{𝑠_{𝑁⁢𝑁}}$ = 5.02TeV. The 0p and 3p cross sections are described by the RELDIS model within their measurement uncertainties, while the 1p and 2p cross sections are underestimated by the model by 17–25%. According to this model, these 0p, 1p, 2p, and 3p cross sections are associated, respectively, with the production of various isotopes of Pb, Tl, Hg, and Au in the EMD of 208 Pb . The cross sections of the emission of a single proton accompanied by the emission of one, two, or three neutrons in EMD were also measured. The data are significantly overestimated by the RELDIS model, which predicts that the (1p,1n), (1p,2n), and (1p,3n) cross sections are very similar to the cross sections for the production of the thallium isotopes 206,205,204 Tl.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Spectra and elliptic flow for identified hadrons in 2.76 A TeV Pb + Pb collisions

Using the VISHNU hybrid model that couples (2+1)-dimensional viscous hydrodynamics to a microscopic hadronic transport model, we calculate the multiplicity, p T spectra, and elliptic flow for pions, kaons, and protons in 2.76A TeV Pb+Pb collisions, using MC-KLN initializations with smoothed initial conditions, obtained by averaging over a large number of events. The results from our calculations are compared to data from the ALICE Collaboration, showing nice agreement over several centrality bins. Using the same inputs, we predict the p T spectra and elliptic flow for φ mesons and explore their flow development in the strong and weak coupling limits through hydrodynamic calculations with different decoupling temperatures. In addition we study the influence of baryon and antibaryon annihilation processes on common observables and demonstrate that, by including annihilation processes below a switching temperature of 165 MeV, VISHNU provides a good description of the multiplicity and p T spectra for pions, kaons, and protons measured by PHENIX and ALICE at both the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC).

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2019

Collision-energy dependence of p t correlations in Au + Au collisions at energies available at the BNL Relativistic Heavy Ion Collider

We present two-particle $p_{\rm t}$ correlations as a function of event centrality for Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV at the Relativistic Heavy Ion Collider using the STAR detector. These results are compared to previous measurements from CERES at the Super Proton Synchrotron and from ALICE at the Large Hadron Collider. The data are compared with UrQMD model calculations and with a model based on a Boltzmann-Langevin approach incorporating effects from thermalization. The relative dynamical correlations for Au+Au collisions at $\sqrt{s_{\rm NN}}$ = 200 GeV show a power law dependence on the number of participant nucleons and agree with the results for Pb+Pb collisions at $\sqrt{s_{\rm NN}} = 2.76~ {\rm TeV}$ from ALICE. As the collision energy is lowered from $\sqrt{s_{\rm NN}}$ = 200 GeV to 7.7 GeV, the centrality dependence of the relative dynamical correlations departs from the power law behavior observed at the higher collision energies. In central collisions, the relative dynamical correlations increase with collision energy up to $\sqrt{s_{\rm NN}}$ = 200 GeV in contrast to previous measurements that showed little dependence on the collision energy.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Studying the interaction between charm and light-flavor mesons

The two-particle momentum correlation functions between charm mesons ( D * ± and D ± ) and charged light-flavor mesons ( π ± and K ± ) in all charge combinations are measured for the first time by the ALICE Collaboration in high-multiplicity proton–proton collisions at a center-of-mass energy of s = 13 TeV . For DK and D * K pairs, the experimental results are in agreement with theoretical predictions of the residual strong interaction based on quantum chromodynamics calculations on the lattice and chiral effective field theory. In the case of D π and D * π pairs, tension between the calculations including strong interactions and the measurement is observed. For all particle pairs, the data can be adequately described by Coulomb interaction only, indicating a shallow interaction between charm and light-flavor mesons. Finally, the scattering lengths governing the residual strong interaction of the D π and D * π systems are determined by fitting the experimental correlation functions with a model that employs a Gaussian potential. The extracted values are small and compatible with zero. © 2024 CERN, for the ALICE Collaboration 2024 CERN

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Measurement of electrons from semileptonic heavy-flavor hadron decays in p p collisions at s = 2.76 TeV

We measured the p T -differential production cross section of electrons from semileptonic decays of heavy-flavor hadrons at midrapidity in proton-proton collisions and at √s=2.76 TeV in the transverse momentum range 0.5 T <12 GeV/c with the ALICE detector at the LHC. Our analysis was performed using minimum bias events and events triggered by the electromagnetic calorimeter. Predictions from perturbative QCD calculations agree with the data within the theoretical and experimental uncertainties.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

ψ ( 2 S ) Suppression in Pb-Pb Collisions at the LHC

The production of the ψ ( 2 S ) charmonium state was measured with ALICE in Pb-Pb collisions at s NN = 5.02 TeV , in the dimuon decay channel. A significant signal was observed for the first time at LHC energies down to zero transverse momentum, at forward rapidity ( 2.5 < y < 4 ). The measurement of the ratio of the inclusive production cross sections of the ψ ( 2 S ) and J / ψ resonances is reported as a function of the centrality of the collisions and of transverse momentum, in the region p T < 12 GeV / c . The results are compared with the corresponding measurements in p p collisions, by forming the double ratio [ σ ψ ( 2 S ) / σ J / ψ ] Pb − Pb / [ σ ψ ( 2 S ) / σ J / ψ ] p p . It is found that in Pb-Pb collisions the ψ ( 2 S ) is suppressed by a factor of ∼ 2 with respect to the J / ψ . The ψ ( 2 S ) nuclear modification factor R AA was also obtained as a function of both centrality and p T . The results show that the ψ ( 2 S ) resonance yield is strongly suppressed in Pb-Pb collisions, by a factor of up to ∼ 3 with respect to p p . Comparisons of cross section ratios with previous Super Proton Synchrotron findings by the NA50 experiment and of R AA with higher- p T results at LHC energy are also reported. These results and the corresponding comparisons with calculations of transport and statistical models address questions on the presence and properties of charmonium states in the quark-gluon plasma formed in nuclear collisions at the LHC. © 2024 CERN, for the ALICE Collaboration 2024 CERN

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Photoproduction of K + K − Pairs in Ultraperipheral Collisions

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

43 PARTICLE ACCELERATORS↗