The production of prompt $\rm \Lambda_{\rm c}^{+}$ 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 $\sqrt{s_{\rm NN}} = 5.02$ TeV with the ALICE detector. The results are more precise, more differential in centrality, and reach much lower transverse momentum ($p_{\rm T}=1$ 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 $p_{\rm T}=0$. The $p_{\rm T}$-differential $\rm \Lambda_{\rm c}^{+}$/D$^0$ production ratio is enhanced with respect to the pp measurement for $4<p_{\rm T}<8$ GeV/$c$ by 3.7 standard deviations ($\sigma$), while the $p_{\rm T}$-integrated ratios are compatible within 1$\sigma$. The observed trend is similar to that observed in the strange sector for the $\Lambda/$K$^0_{\rm S}$ ratio. Model calculations including coalescence or statistical hadronization for charm-hadron formation are compared with the data.

Differential two-particle normalized cumulants ($R_2$) and transverse momentum correlations ($P_2$) are measured as a function of the relative pseudorapidity and azimuthal angle difference $( Δη, Δφ)$ of charged particle pairs in minimum bias pp collisions at $\sqrt{\textit{s}}$ = 13 TeV. The measurements use charged hadrons in the pseudorapidity region of $|η| < 0.8$ and the transverse momentum range \mbox{0.2 $< \textit{p}_{\mathrm T} < $ 2.0 $\mathrm{GeV}/\textit{c}$} in order to focus on soft multiparticle interactions and to complement prior measurements of these correlation functions in p-Pb and Pb-Pb collisions. The correlation functions are reported for both unlike-sign and like-sign pairs and their charge-independent and charge-dependent combinations. Both the $R_2$ and $P_2$ measured in pp collisions exhibit features qualitatively similar to those observed in p--Pb and Pb--Pb collisions. The $Δη$ and $Δφ$ root mean square widths of the near-side peak of the correlation functions are evaluated and compared with those observed in p-Pb and Pb-Pb collisions and show smooth evolution with the multiplicity of charged particles produced in the collision. The comparison of the measured correlation functions with predictions from PYTHIA8 shows that this model qualitatively captures their basic structure and characteristics but feature important differences. In addition, the $R_2^{\rm CD}$ is used to determine the charge balance function of hadrons produced within the detector acceptance of the measurements. The integral of the balance function is found to be compatible with those reported by a previous measurement in Pb--Pb collisions.

Ultrarelativistic heavy-ion collisions create a quark-gluon plasma (QGP), a hot and dense state of strongly interacting QCD matter. In ultracentral collisions, the QGP volume remains nearly constant event-by-event, while its total entropy can fluctuate due to quantum effects, leading to temperature variations. These features allow the correlation between the mean transverse momentum $(\langle p_{\mathrm{T}} \rangle)$ of charged hadrons and their multiplicity to serve as a probe of the QGP's speed of sound, $c_{s}$. This study extracts $c_{s}$ by analyzing the relative increase in $\langle p_{\mathrm{T}} \rangle$ with respect to the charged-particle density $(\langle \mathrm{d}N_\mathrm{ch}/\mathrm{d}\eta \rangle)$ at midrapidity in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02~\mathrm{TeV}$, using data from the ALICE detector. Centrality is determined with estimators based on multiplicity and transverse energy, applying a pseudorapidity gap to reduce selection biases. The extracted value of $c_{s}^{2}$ is found to strongly depend on the employed centrality estimator and ranges between $0.1146 \pm 0.0028 \,\mathrm{(stat.)} \pm 0.0065 \,\mathrm{(syst.)}$ and $0.4374 \pm 0.0006 \mathrm{(stat.)} \pm 0.0184 \mathrm{(syst.)}$ in natural units. Additionally, the event-by-event $[p_{\mathrm{T}}]$ distribution is studied through its variance, skewness, and kurtosis. A pronounced decrease in the self-normalized variance and a peak followed by a drop in skewness suggest the suppression of impact-parameter fluctuations in ultracentral collisions. These observations provide new insights into the thermodynamic properties and initial-state fluctuations of the QGP.

The coherent J/$\psi$ photoproduction cross section is measured for the first time at midrapidity in peripheral to semicentral Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV. The centrality differential cross section ${\rm d} \sigma/ {\rm d}y$ is reported for the centrality range 40-90%, together with the doubly-differential cross section ${\rm d}^2 \sigma /{\rm d}y {\rm d} p_{\rm T}$, extracted in two peripheral centrality classes. The J/$\psi$ mesons are reconstructed in the dielectron channel, in the rapidity interval $|y| <$ 0.9 using the ALICE central barrel detectors. The J/$\psi$ 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.

The transverse momentum spectra and integrated yields of $\overlineΣ^{\pm}$ have been measured in pp and p-Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02$ TeV with the ALICE experiment. Measurements are performed via the newly accessed decay channel $\overlineΣ^{\pm} \rightarrow {\rm\overline{n}}π^{\pm}$. A new method of antineutron reconstruction with the PHOS electromagnetic spectrometer is developed and applied to this analysis. The $p_{\rm T}$ spectra of $\overlineΣ^{\pm}$ are measured in the range $0.5 < p_{\rm T} < 3$ GeV/$c$ and compared to predictions of the PYTHIA 8, DPMJET, PHOJET, EPOS LHC and EPOS4 models. The EPOS LHC and EPOS4 models provide the best descriptions of the measured spectra both in pp and p-Pb collisions, while models which do not account for multiparton interactions provide a considerably worse description at high $p_{\rm T}$. The total yields of $\overlineΣ^{\pm}$ in both pp and p-Pb collisions are compared to predictions of the Thermal-FIST model and dynamical models PYTHIA 8, DPMJET, PHOJET, EPOS LHC and EPOS4. All models reproduce the total yields in both colliding systems within uncertainties. The nuclear modification factors $R_{\rm pPb}$ for both $\overlineΣ^{+}$ and $\overlineΣ^{-}$ are evaluated and compared to those of protons, $Λ$ and $Ξ$ hyperons, and predictions of EPOS LHC and EPOS4 models. No deviations of $R_{\rm pPb}$ for $\overlineΣ^{\pm}$ from the model predictions or measurements for other hadrons are found within uncertainties.

The FASER experiment at the LHC is designed to search for light, weakly-interacting particles produced in proton-proton collisions at the ATLAS interaction point that travel in the far-forward direction. The first results from a search for dark photons decaying to an electron-positron pair, using a dataset corresponding to an integrated luminosity of 27.0 fb$^{-1}$ collected at center-of-mass energy $\sqrt{s} = 13.6$ TeV in 2022 in LHC Run 3, are presented. No events are seen in an almost background-free analysis, yielding world-leading constraints on dark photons with couplings $\epsilon \sim 2 \times 10^{-5} - 1 \times 10^{-4}$ and masses $\sim$ 17 MeV - 70 MeV. The analysis is also used to probe the parameter space of a massive gauge boson from a U(1)$_{B-L}$ model, with couplings $g_{B-L} \sim 5 \times 10^{-6} - 2 \times 10^{-5}$ and masses $\sim$ 15 MeV - 40 MeV excluded for the first time.

Measurement by the STAR experiment at RHIC of the cold nuclear matter (CNM) effects experienced by inclusive $J/\psi$ at mid-rapidity in 0-100%$p$+Au collisions at $\sqrt{s_{_{\mathrm{NN}}}}$ = 200 GeV is presented. Such effects are quantified utilizing the nuclear modification factor, $R_{p\mathrm{Au}}$, obtained by taking a ratio of $J/\psi$ yield in $p$+Au collisions to that in $p$+$p$ collisions scaled by the number of binary nucleon-nucleon collisions. The differential $J/\psi$ yield in both $p$+$p$ and $p$+Au collisions is measured through the dimuon decay channel, taking advantage of the trigger capability provided by the Muon Telescope Detector in the RHIC 2015 run. Consequently, the $J/\psi$$R_{p\mathrm{Au}}$ is derived within the transverse momentum ($p_{\mathrm{T}}$) range of 0 to 10 GeV/$c$. A suppression of approximately 30% is observed for $p_{\mathrm{T}}<2$ GeV/$c$, while $J/\psi$ $R_{p\mathrm{Au}}$ becomes compatible with unity for $p_{\mathrm{T}}$ greater than 3 GeV/$c$, indicating the $J/\psi$ yield is minimally affected by the CNM effects at high $p_{\mathrm{T}}$. Comparison to a similar measurement from 0-20% central Au+Au collisions reveals that the observed strong $J/\psi$ suppression above 3 Gev/$c$ is mostly due to the hot medium effects, providing strong evidence for the formation of the quark-gluon plasma in these collisions. Several model calculations show qualitative agreement with the measured $J/\psi$ $R_{p\mathrm{Au}}$, while their agreement with the $J/\psi$ yields in $p$+$p$ and $p$+Au collisions is worse.

Results from the study of the rare decays $K^+\toπ^+ν\barν$, $K^{+}\rightarrowπ^{+}μ^{+}μ^{-}$ and $K^{+}\rightarrowπ^{+}γγ$ at the NA62 experiment at CERN are interpreted in terms of improved limits for $\rm{B}(K^+\toπ^+X)$ and coupling parameters of hidden-sector models, where $X$ is a mediator. World-leading limits are achieved for dark photon, dark scalar and axion-like particle models.

We report on measurements of sequential $\Upsilon$ suppression in Au+Au collisions at $\sqrt{s_{_\mathrm{NN}}}$ = 200 GeV with the STAR detector at the Relativistic Heavy Ion Collider (RHIC) through both the dielectron and dimuon decay channels. In the 0-60% centrality class, the nuclear modification factors ($R_{\mathrm{AA}}$), which quantify the level of yield suppression in heavy-ion collisions compared to $p$+$p$ collisions, for $\Upsilon$(1S) and $\Upsilon$(2S) are $0.40 \pm 0.03~\textrm{(stat.)} \pm 0.03~\textrm{(sys.)} \pm 0.09~\textrm{(norm.)}$ and $0.26 \pm 0.08~\textrm{(stat.)} \pm 0.02~\textrm{(sys.)} \pm 0.06~\textrm{(norm.)}$, respectively, while the upper limit of the $\Upsilon$(3S) $R_{\mathrm{AA}}$ is 0.17 at a 95% confidence level. This provides experimental evidence that the $\Upsilon$(3S) is significantly more suppressed than the $\Upsilon$(1S) at RHIC. The level of suppression for $\Upsilon$(1S) is comparable to that observed at the much higher collision energy at the Large Hadron Collider. These results point to the creation of a medium at RHIC whose temperature is sufficiently high to strongly suppress excited $\Upsilon$ states.

We report results on an elastic cross section measurement in proton-proton collisions at a center-of-mass energy $\sqrt{s}=510$ GeV, obtained with the Roman Pot setup of the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). The elastic differential cross section is measured in the four-momentum transfer squared range $0.23 \leq -t \leq 0.67$ GeV$^2$. We find that a constant slope $B$ does not fit the data in the aforementioned $t$ range, and we obtain a much better fit using a second-order polynomial for $B(t)$. The $t$ dependence of $B$ is determined using six subintervals of $t$ in the STAR measured $t$ range, and is in good agreement with the phenomenological models. The measured elastic differential cross section $\mathrm{d}\sigma/\mathrm{dt}$ agrees well with the results obtained at $\sqrt{s} = 546$ GeV for proton--antiproton collisions by the UA4 experiment. We also determine that the integrated elastic cross section within the STAR $t$-range is $\sigma^\mathrm{fid}_\mathrm{el} = 462.1 \pm 0.9 (\mathrm{stat.}) \pm 1.1 (\mathrm {syst.}) \pm 11.6 (\mathrm {scale})$~$\mu\mathrm{b}$.