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1. Strangeness Photoproduction at the BGO-OD experiment

   https://doi.org/10.1051/epjconf/202024101008  

   Jude, Thomas ; Alef, Stefan ; Bauer, Patrick ; Beck, Reinhard ; Braghieri, Alessandro ; Cole, Philip ; Di Salvo, Rachele ; Elsner, Daniel ; Fantini, Alessia ; Freyermuth, Oliver ; et al ( January 2020 , EPJ Web of Conferences)

   Beck, R. ; Thiel, A. ; Thoma, U. ; Wunderlich, Y. (Ed.)

   The BGO-OD experiment at the ELSA accelerator facility uses an energy tagged bremsstrahlung photon beam to investigate the excitation structure of the nucleon. The setup consists of a highly segmented BGO calorimeter surrounding the target, with a particle tracking magnetic spectrometer at forward angles. BGO-OD is ideal for investigating low momentum transfer processes due to the acceptance and high momentum resolution at forward angles. In particular, this enables the investigation of strangeness photoproduction where t-channel exchange mechanisms play an important role. This also allows access to low momentum exchange kinematics where extended, molecular structure may manifest in reaction mechanisms. First key results at low t indicate a cusp-like structure in K + Σ 0 photoproduction at W = 1900 MeV, line shapes and differential cross sections for K + Λ(1405)→ K + Σ 0 π 0 , and a peak structure in K 0 S Σ 0 photoproduction. The peak in the K 0 S Σ 0 channel appears consistent with meson-baryon generated states, where equivalent models have been used to describe the P C pentaquark candidates in the heavy charmed quark sector. 

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2. Constraining the $${\overline{\textrm{K}}}{\textrm{N}}$$ coupled channel dynamics using femtoscopic correlations at the LHC

   https://doi.org/10.1140/epjc/s10052-023-11476-0  

   Acharya, S. ; Adamová, D. ; Adler, A. ; Aglieri Rinella, G. ; Agnello, M. ; Agrawal, N. ; Ahammed, Z. ; Ahmad, S. ; Ahn, S. U. ; Ahuja, I. ; et al ( April 2023 , The European Physical Journal C)

   Abstract The interaction of $$\textrm{K}^{-}$$ K - with protons is characterised by the presence of several coupled channels, systems like $${\overline{\textrm{K}}}^0$$ K ¯ 0 n and $$\uppi \Sigma $$ π Σ with a similar mass and the same quantum numbers as the $$\textrm{K}^{-}$$ K - p state. The strengths of these couplings to the $$\textrm{K}^{-}$$ K - p system are of crucial importance for the understanding of the nature of the $$\Lambda (1405)$$ Λ ( 1405 ) resonance and of the attractive $$\textrm{K}^{-}$$ K - p strong interaction. In this article, we present measurements of the $$\textrm{K}^{-}$$ K - p correlation functions in relative momentum space obtained in pp collisions at $$\sqrt{s}~=~13$$ s = 13  Te, in p–Pb collisions at $$\sqrt{s_{\textrm{NN}}}~=~5.02$$ s NN = 5.02  Te, and (semi)peripheral Pb–Pb collisions at $$\sqrt{s_{\textrm{NN}}}~=~5.02$$ s NN = 5.02  Te. The emitting source size, composed of a core radius anchored to the $$\textrm{K}^{+}$$ K + p correlation and of a resonance halo specific to each particle pair, varies between 1 and 2 fm in these collision systems. The strength and the effects of the $${\overline{\textrm{K}}}^0$$ K ¯ 0 n and $$\uppi \Sigma $$ π Σ inelastic channels on the measured $$\textrm{K}^{-}$$ K - p correlation function are investigated in the different colliding systems by comparing the data with state-of-the-art models of chiral potentials. A novel approach to determine the conversion weights $$\omega $$ ω , necessary to quantify the amount of produced inelastic channels in the correlation function, is presented. In this method, particle yields are estimated from thermal model predictions, and their kinematic distribution from blast-wave fits to measured data. The comparison of chiral potentials to the measured $$\textrm{K}^{-}$$ K - p interaction indicates that, while the $$\uppi \Sigma $$ π Σ – $$\textrm{K}^{-}$$ K - p dynamics is well reproduced by the model, the coupling to the $${\overline{\textrm{K}}}^0$$ K ¯ 0 n channel in the model is currently underestimated. 

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3. Progress on Meson-Baryon Scattering

   https://doi.org/10.22323/1.396.0170  

   C. Morningstar ; J. Bulava ; A. Hanlon ; B. Hörz ; D. Mohler ; A. Nicholson ; S. Skinner ; A. Walker-Loud ( January 2021 , 38th International Symposium on Lattice Field Theory, LATTICE2021 26th-30th July, 2021)

   Progress in computing various meson-baryon scattering amplitudes is presented on a single en- semble from the Coordinated Lattice Simulations (CLS) consortium with m π = 200 MeV and Nf = 2 + 1 dynamical fermions. The finite-volume Lüscher approach is employed to determine the lowest few partial waves from ground- and excited-state energies computed from correla- tion matrices rotated in a single pivot using a generalized eigenvector solution. This analysis requires evaluating matrices of correlation functions between single- and two-hadron interpolat- ing operators which are projected onto definite spatial momenta and finite-volume irreducible representations. The stochastic LapH method is used to estimate all needed quark propagators. Preliminary results are presented for I = 1/2, 3/2 N π amplitudes including the ∆(1232) resonance and the I = 0 S-wave amplitude with unit strangeness relevant for the Λ(1405). 

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4. $$\Sigma (1385)^{\pm }$$ resonance production in Pb–Pb collisions at $$\sqrt{s_{\textrm{NN}}}~=~5.02$$ TeV

   https://doi.org/10.1140/epjc/s10052-023-11475-1  

   Acharya, S. ; Adamová, D. ; Adler, A. ; Aglieri Rinella, G. ; Agnello, M. ; Agrawal, N. ; Ahammed, Z. ; Ahmad, S. ; Ahn, S. U. ; Ahuja, I. ; et al ( May 2023 , The European Physical Journal C)

   Abstract Hadronic resonances are used to probe the hadron gas produced in the late stage of heavy-ion collisions since they decay on the same timescale, of the order of 1–10 fm/ c , as the decoupling time of the system. In the hadron gas, (pseudo)elastic scatterings among the products of resonances that decayed before the kinetic freeze-out and regeneration processes counteract each other, the net effect depending on the resonance lifetime, the duration of the hadronic phase, and the hadronic cross sections at play. In this context, the $$\Sigma (1385)^{\pm }$$ Σ ( 1385 ) ± particle is of particular interest as models predict that regeneration dominates over rescattering despite its relatively short lifetime of about 5.5 fm/ c . The first measurement of the $$\Sigma (1385)^{\pm }$$ Σ ( 1385 ) ± resonance production at midrapidity in Pb–Pb collisions at $$\sqrt{s_{\textrm{NN}}}= 5.02$$ s NN = 5.02 TeV with the ALICE detector is presented in this Letter. The resonances are reconstructed via their hadronic decay channel, $$\Lambda \pi $$ Λ π , as a function of the transverse momentum ( $$p_\textrm{T}$$ p T ) and the collision centrality. The results are discussed in comparison with the measured yield of pions and with expectations from the statistical hadronization model as well as commonly employed event generators, including PYTHIA8/Angantyr and EPOS3 coupled to the UrQMD hadronic cascade afterburner. None of the models can describe the data. For $$\Sigma (1385)^{\pm }$$ Σ ( 1385 ) ± , a similar behaviour as $$\textrm{K}^{*} (892)^{0}$$ K ∗ ( 892 ) 0 is observed in data unlike the predictions of EPOS3 with afterburner. 

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5. Measurement of the $$ {\Lambda}_c^{+} $$ to D0 production ratio in periphera PbPb collisions at $$ \sqrt{s_{\textrm{NN}}} $$ = 5.02 TeV

   https://doi.org/10.1007/JHEP06(2023)132  

   Aaij, R. ; Abdelmotteleb, A. S. ; Abellan Beteta, C. ; Abudinén, F. ; Ackernley, T. ; Adeva, B. ; Adinolfi, M. ; Afsharnia, H. ; Agapopoulou, C. ; Aidala, C. A. ; et al ( June 2023 , Journal of High Energy Physics)

   A bstract We report on a measurement of the $$ {\Lambda}_c^{+} $$ Λ c + to D 0 production ratio in peripheral PbPb collisions at $$ \sqrt{s_{\textrm{NN}}} $$ s NN = 5 . 02 TeV with the LHCb detector in the forward rapidity region 2 < y < 4 . 5. The $$ {\Lambda}_c^{+} $$ Λ c + ( D 0 ) hadrons are reconstructed via the decay channel $$ {\Lambda}_c^{+} $$ Λ c + → pK − π + ( D 0 → K − π + ) for 2 < p T < 8 GeV/ c and in the centrality range of about 65–90%. The results show no significant dependence on p T , y or the mean number of participating nucleons. They are also consistent with similar measurements obtained by the LHCb collaboration in pPb and Pbp collisions at $$ \sqrt{s_{\textrm{NN}}} $$ s NN = 5 . 02 TeV. The data agree well with predictions from PYTHIA in pp collisions at $$ \sqrt{s} $$ s = 5 TeV but are in tension with predictions of the Statistical Hadronization model. 

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