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1. Photoproduction of $K^{+}{K}^{-}$ Pairs in Ultraperipheral Collisions

   https://doi.org/10.1103/PhysRevLett.132.222303  

   Acharya, S; Adamová, D; Aglieri_Rinella, G; Agnello, M; Agrawal, N; Ahammed, Z; Ahmad, S; Ahn, S U; Ahuja, I; Akindinov, A; et al (May 2024, Physical Review Letters)

   $K^{+}{K}^{-}$pairs may be produced in photonuclear collisions, either from the decays of photoproduced $\varphi \left(1020\right)$mesons or directly as nonresonant $K^{+}{K}^{-}$pairs. Measurements of $K^{+}{K}^{-}$photoproduction probe the couplings between the $\varphi \left(1020\right)$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 $1.1<M_{KK}<1.4\mathrm{GeV}/c^2$above the $\varphi \left(1020\right)$resonance, for rapidity $\left|y_{KK}\right|<0.8$and $p_{T,KK}<0.1\mathrm{GeV}/c$, the measured coherent photoproduction cross section is $\mathrm{d}\sigma /\mathrm{d}y=3.37\pm 0.61\left(\text{stat}\right)\pm 0.15\left(\mathrm{syst}\right)\mathrm{mb}$. The center-of-mass energy per nucleon of the photon-nucleus (Pb) system $W_{\gamma \mathrm{Pb},n}$ranges from 33 to 188 GeV, far higher than previous measurements on heavy-nucleus targets. The cross section is larger than expected for $\varphi \left(1020\right)$photoproduction alone. The mass spectrum is fit to a cocktail consisting of $\varphi \left(1020\right)$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 Collaboration2024CERN 

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2. Observation of $\mathrm{\Lambda }$ Hyperon Local Polarization in $p$ -Pb Collisions at $\sqrt{s_{\mathrm{NN}}}=8.16\mathrm{TeV}$

   https://doi.org/10.1103/6ywq-gm61  

   Hayrapetyan, A; Tumasyan, A; Adam, W; Andrejkovic, J W; Benato, L; Bergauer, T; Chatterjee, S; Damanakis, K; Dragicevic, M; Hussain, P S; et al (September 2025, Physical Review Letters)

   The polarization of the $\mathrm{\Lambda }$and $\overline{\mathrm{\Lambda }}$hyperons along the beam direction has been measured in proton-lead ( $p\text{-Pb}$) collisions at a center-of-mass energy per nucleon pair of 8.16 TeV. The data were obtained with the CMS detector at the LHC and correspond to an integrated luminosity of $186.0\pm 6.5{\mathrm{nb}}^{-1}$. A significant azimuthal dependence of the hyperon polarization, characterized by the second-order Fourier sine coefficient $P_{z,\mathrm{s}2}$, is observed. The $P_{z,\mathrm{s}2}$values decrease as a function of charged particle multiplicity, but increase with transverse momentum. A hydrodynamic model that describes the observed $P_{z,\mathrm{s}2}$values in nucleus-nucleus collisions by introducing vorticity effects does not reproduce either the sign or the magnitude of the $p\text{-Pb}$results. These observations pose a challenge to the current theoretical implementation of spin polarization in heavy ion collisions and offer new insights into the origin of spin polarization in hadronic collisions at LHC energies. 

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3. Search for $h_b\left(2P\right)\to \gamma {\chi }_{bJ}\left(1P\right)$ at $\sqrt{s}=10.860\mathrm{GeV}$

   https://doi.org/10.1103/PhysRevD.111.L011102  

   Boschetti, A; Mussa, R; Tamponi, U; Adachi, I; Aihara, H; Asner, D M; Aushev, T; Ayad, R; Banerjee, Sw; Belous, K; et al (January 2025, Physical Review D)

   In the bottomonium sector, the hindered magnetic dipole transitions between P-wave states $h_b\left(2P\right)\to {\chi }_{bJ}\left(1P\right)\gamma$, $J=0$, 1, 2, are expected to be severely suppressed according to the relativized quark model, due to the spin flip of the $b$quark. Nevertheless, a recent model following the coupled-channel approach predicts the corresponding branching fractions to be enhanced by orders of magnitude. In this Letter, we report the first search for such transitions. We find no significant signals and set upper limits at 90% confidence level on the corresponding branching fractions: $\mathcal{B}\left[h_b\right(2P)\to \gamma {\chi }_{b0}(1P\left)\right]<2.7\times {10}^{-1}$, $\mathcal{B}\left[h_b\right(2P)\to \gamma {\chi }_{b1}(1P\left)\right]<5.4\times {10}^{-3}$and $\mathcal{B}\left[h_b\right(2P)\to \gamma {\chi }_{b2}(1P\left)\right]<1.3\times {10}^{-2}$. These values help to constrain the parameters of the coupled-channel models. The results are obtained using a $121.4{\mathrm{fb}}^{-1}$data sample taken around $\sqrt{s}=10.860\mathrm{GeV}$with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$collider. Published by the American Physical Society2025 

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4. Search for charmed baryons in the ${\mathrm{\Lambda }}_c^{+}\eta$ system and measurement of the branching fractions of ${\mathrm{\Lambda }}_c(2880{)}^{+}$ and ${\mathrm{\Lambda }}_c(2940{)}^{+}$ decaying to ${\mathrm{\Lambda }}_c^{+}\eta$ and $p{D}^0$ relative to ${\mathrm{\Sigma }}_c\left(2455\right)\pi$

   https://doi.org/10.1103/PhysRevD.110.032021  

   Li, S X; Shen, C P; Adachi, I; Ahn, J K; Aihara, H; Asner, D M; Atmacan, H; Aushev, T; Ayad, R; Banerjee, Sw; et al (August 2024, Physical Review D)

   We search for excited charmed baryons in the ${\mathrm{\Lambda }}_c^{+}\eta$system using a data sample corresponding to an integrated luminosity of $980{\mathrm{fb}}^{-1}$. The data were collected by the Belle detector at the KEKB $e^{+}{e}^{-}$asymmetric-energy collider. No significant signals are found in the ${\mathrm{\Lambda }}_c^{+}\eta$mass spectrum, including the known ${\mathrm{\Lambda }}_c(2880{)}^{+}$and ${\mathrm{\Lambda }}_c(2940{)}^{+}$. Clear ${\mathrm{\Lambda }}_c(2880{)}^{+}$and ${\mathrm{\Lambda }}_c(2940{)}^{+}$signals are observed in the $p{D}^0$mass spectrum. We set upper limits at 90% credibility level on ratios of branching fractions of ${\mathrm{\Lambda }}_c(2880{)}^{+}$and ${\mathrm{\Lambda }}_c(2940{)}^{+}$decaying to ${\mathrm{\Lambda }}_c^{+}\eta$relative to ${\mathrm{\Sigma }}_c\left(2455\right)\pi$of $<0.13$for the ${\mathrm{\Lambda }}_c(2880{)}^{+}$and $<1.11$for the ${\mathrm{\Lambda }}_c(2940{)}^{+}$. We measure ratios of branching fractions of ${\mathrm{\Lambda }}_c(2880{)}^{+}$and ${\mathrm{\Lambda }}_c(2940{)}^{+}$decaying to $p{D}^0$relative to ${\mathrm{\Sigma }}_c\left(2455\right)\pi$of $0.75\pm 0.03\left(\mathrm{stat}\right)\pm 0.07\left(\mathrm{syst}\right)$for the ${\mathrm{\Lambda }}_c(2880{)}^{+}$and $3.59\pm 0.21\left(\mathrm{stat}\right)\pm 0.56\left(\mathrm{syst}\right)$for the ${\mathrm{\Lambda }}_c(2940{)}^{+}$. Published by the American Physical Society2024 

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5. First measurement of $D_{s1}\left(1^{+}\right)(2536{)}^{+}$ and $D_{s2}^{*}\left(2^{+}\right)(2573{)}^{+}$ production in proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$ at the LHC

   https://doi.org/10.1103/PhysRevD.111.112005  

   Acharya, S; Agarwal, A; Aglieri_Rinella, G; Aglietta, L; Agnello, M; Agrawal, N; Ahammed, Z; Ahmad, S; Ahn, S U; Ahuja, I; et al (June 2025, Physical Review D)

   The production yields of the orbitally excited charm-strange mesons ${\mathrm{D}}_{\mathrm{s}1}\left(1^{+}\right)(2536{)}^{+}$and ${\mathrm{D}}_{\mathrm{s}2}^{*}\left(2^{+}\right)(2573{)}^{+}$were measured for the first time in proton-proton (pp) collisions at a center-of-mass energy of $\sqrt{s}=13\mathrm{TeV}$with the ALICE experiment at the LHC. The ${\mathrm{D}}_{\mathrm{s}1}^{+}$and ${\mathrm{D}}_{\mathrm{s}2}^{*+}$mesons were measured at midrapidity ( $\left|y\right|<0.5$) in minimum-bias and high-multiplicity pp collisions in the transverse-momentum interval $2<p_{\mathrm{T}}<24\mathrm{GeV}/c$. Their production yields relative to the ${\mathrm{D}}_{\mathrm{s}}^{+}$ground-state yield were found to be compatible between minimum-bias and high-multiplicity collisions, as well as with previous measurements in ${\mathrm{e}}^{\pm }\mathrm{p}$and ${\mathrm{e}}^{+}{\mathrm{e}}^{-}$collisions. The measured ${\mathrm{D}}_{\mathrm{s}1}^{+}/{\mathrm{D}}_{\mathrm{s}}^{+}$and ${\mathrm{D}}_{\mathrm{s}2}^{*+}/{\mathrm{D}}_{\mathrm{s}}^{+}$yield ratios are described by statistical hadronization models and can be used to tune the parameters governing the production of excited charm-strange hadrons in Monte Carlo generators, such as 8. 

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