Abstract The measurement of three-dimensional femtoscopic correlations between identical charged kaons (K ± K ± ) produced in p–Pb collisions at center-of-mass energy per nucleon pair $$\sqrt{{s}_{\text{NN}}}=5.02$$ TeV with ALICE at the LHC is presented for the first time. This measurement, supplementary to those in pp and Pb–Pb collisions, allows understanding the particle-production mechanisms at different charged-particle multiplicities and provides information on the dynamics of the source of particles created in p–Pb collisions, for which a general consensus does not yet exist. It is shown that the measured source sizes increase with charged-particle multiplicity and decrease with increasing pair transverse momentum. These trends for K ± K ± are similar to the ones observed earlier in identical charged-pion and $${\text{K}}_{\text{s}}^{0}{\text{K}}_{\text{s}}^{0}$$ correlations in Pb–Pb collisions at various energies and in π ± π ± correlations in p–Pb collisions at $$\sqrt{{s}_{\text{NN}}}=5.02$$ TeV. At comparable multiplicity, the source sizes measured in p–Pb collisions agree within uncertainties with those observed in pp collisions, and there is an indication that they are smaller than those observed in Pb–Pb collisions. The obtained results are also compared with predictions from the hadronic interaction model EPOS 3, which tends to underestimate the source size for the most central collisions and agrees with the data for semicentral and peripheral events. Furthermore, the time of maximal emission for kaons is extracted. It turns out to be comparable with the value obtained in highly peripheral Pb–Pb collisions at the same energy, indicating that the kaon emission evolution is similar to that in p–Pb collisions.

The low-lying states in the even-even 128,130Xe nuclei have been investigated using prompt γ-ray spectroscopy to explore the quasiparticle-phonon coupling. The nuclei were populated via fusion-evaporation reactions: 130Te(4He, 4nγ)130Xe at 43 MeV of beam energy and 124Sn(9Be, 5nγ)128Xe at 40 MeV of beam energy. The bands built on the second 2+ state in these two isotopes have been primarily investigated in the light of the new results obtained in this work. The spectroscopic features of these bands are systematically compared with the quasi-γ bands reported in the lighter Xe isotopes which reveals a remarkable similarity. To gain insight into the intrinsic structures of 128,130Xe, theoretical calculations using the microscopic Triaxial Projected Shell Model (TPSM) approach have been carried out. The experimental results are compared with these calculations, showing a good overall agreement and suggesting a transition from γ-soft to γ-rigid shape in 130Xe.

The excitation scheme of the ^65Zn (Z = 30, N = 35) nucleus has been probed following its population in the ^63Cu(α,pn) reaction at E_beam = 30 MeV and using an array of Compton suppressed HPGe clovers as the detection system. This work has identified several new transitions of the nucleus and have modified the placements of some of the previously known ones. The multipolarities and the electric/ magnetic nature of the observed γ-ray rays have been measured, using the conventional methodologies. The spin-parity assignments for the levels have consequently been made; some of the spin-parities are new while others are either validation of the existing values or are modified results based on the present analysis. The experimental level scheme exhibits collective as well as single particle structures. The measured level energies have been compared with those calculated in the framework of the large basis shell model using a model space of p_3/2, f_5/2, p_1/2, g_9/2 orbitals and two different interactions. The collective excitations of the nucleus were probed through the properties of its band structures and through the calculations of the Total Routhian Surface (TRS) for the associated deformations/ shapes. The results of this study brings out the essential features of evolving structural characteristics and developing collectivity with increasing number of nucleons outside a doubly-magic core and with their occupancy of deformation driving high-j orbitals.

This paper presents the first measurement of the angle between different jet axes (denoted as Delta R-axis) in Pb-Pb collisions. The measurement is carried out in the 0-10% most-central events at root s(NN) = 5.02 TeV. Jets are assembled by clustering charged particles at midrapidity using the anti-kT algorithm with resolution parameters R = 0.2 and 0.4 and transverse momenta in the intervals 40 < p(T)(ch jet) < 140 GeV/c and 80 < p(T)(ch jet) < 140 GeV/c, respectively. Measurements at these low transverse momenta enhance the sensitivity to quark-gluon plasma (QGP) effects. A comparison to models implementing various mechanisms of jet energy loss in the QGP suggests that the observed narrowing of the Pb-Pb distribution relative to pp can be explained if quark-initiated jets are more likely to emerge from the medium than gluon-initiated jets. These new measurements disfavor intrajet p(T) broadening as implemented in a simple model calculation with the Baier-Dokshitzer-Mueller-Peigne-Schiff formalism for energy loss in the QGP. The comparison of Pb-Pb and pp collisions shows sensitivity to the angular scale at which the QGP can resolve two independent splittings, favoring mechanisms that incorporate incoherent energy loss.

The nuclear modification factor R-AA of charm jets, identified by the presence of a D-0 meson among the jet constituents, has been measured for the first time in Pb-Pb collisions at a centre-of-mass energy per nucleon pair root s(NN) = 5.02 TeV with the ALICE detector at the LHC. The D-0 mesons and their charge conjugates are reconstructed from the hadronic decay D-0 -> K-pi(+). Jets are reconstructed from D-0-meson candidates and charged particles using the anti-k(T) algorithm with jet resolution parameter R = 0.3, in the jet transverse momentum (p(T)) range 5

The two known low-lying long-lived states in 178Ta, J(x)=1+(T1/2=9.3 min) and J(x)=7-(T1/2=2.36 h) are populated through the 175Lu(a,n) reaction with two different irradiation times. The resulting y decay spectra have been analyzed with an aim to resolve the ambiguity in the ground state assignment of 178Ta. From the simultaneous decays of the two activities, their percentage populations are determined to be (66.2 +/- 3.0)% for the 1+ state and (33.8 +/- 0.9)% for the 7-state. The experimental results are compared with a) theoretical calculations using the phenomenological Two Quasiparticle Rotor Model and b) reaction modeling using TALYS. The consistency between experiment and both theoretical approaches provides evidence for the 1+ state to be the ground state while the 7-could be an excited level at similar to 20 keV in the 178Ta level scheme.

The production of (multi-)strange hadrons is measured at midrapidity in proton-proton collisions at √(s) = 13 TeV as a function of the local charged-particle multiplicity in the pseudorapidity interval |η| < 0.5 and of the very-forward energy measured by the ALICE Zero-Degree Calorimeters. The latter provides information on the effective energy, i.e. the energy available for particle production in the collision once subtracted from the centre-of-mass energy. The yields of K_S^0 , Λ +Λ , and Ξ^-+Ξ^+ per charged-particle increase with the effective energy. In addition, this work exploits a multi-differential approach to decouple the roles of local multiplicity and effective energy in such an enhancement. The results presented in this article provide new insights into the interplay between global properties of the collision, such as the initial available energy in the event, and the locally produced final hadronic state, connected to the charged-particle multiplicity at midrapidity. Notably, a strong increase of strange baryon production with effective energy is observed for fixed charged-particle multiplicity at midrapidity. These results are discussed within the context of existing phenomenological models of hadronisation implemented in different tunes of the PYTHIA 8 event generator.

The excited states of odd-A nucleus 55Mn have been investigated using alpha-induced fusion evaporation reaction to explore the shape driving effect of proton f7/2 orbital below Z = 28 shell gap. A deformed band structure, based on pi f7/2 configuration has been identified at lower excitation with firm spin-parity assignments of the levels. Band crossing has been identified for the first time in this nucleus through the observation of back bending in one of the signature partners. The properties of this band has been compared with the similar bands in the neighboring isotopes, 57,59Mn. The Total Routhian Surface calculations predict prolate shape for all the three Mn isotopes below the band crossing. However, a change in shape is predicted by these calculations at higher frequencies beyond the particle alignment. An unnatural parity state has also been identified in 55Mn which has been found to decay by E3 and E1 transitions. This observation indicates, for the first time, the presence of octupole correlation in this nucleus. It has been discussed in the light of the octupole correlation observed in its isobar 55V and other nearby odd-odd nuclei.

This paper presents a study of the inclusive forward J/ψ yield as a function of forward charged-particle multiplicity in pp collisions at √(s) = 13 TeV using data collected by the ALICE experiment at the CERN LHC. The results are presented in terms of relative J/ψ yields and relative charged-particle multiplicities with respect to these quantities obtained in inelastic collisions having at least one charged particle in the pseudorapidity range |η| < 1. The J/ψ mesons are reconstructed via their decay into μ+μ− pairs in the forward rapidity region (2.5 < y < 4). The relative multiplicity is estimated in the forward pseudorapidity range which overlaps with the J/ψ rapidity region. The results show a steeper-than-linear increase of the J/ψ yields versus the multiplicity. They are compared with previous measurements and theoretical model calculations.

The first measurements of proton emission accompanied by neutron emission in the electromagnetic dissociation (EMD) of Pb-208 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 Pb-208 - Pb-208 collisions at a center-of-mass energy per nucleon pair root s(NN) = 5.02 TeV. 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 Pb-208. 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 Tl-206,Tl-205,Tl-204.

Measurements of azimuthal angular correlations of inclusive and identified particles from EPOS4 and PYTHIA8 event generators are used to study the unexpected collective behavior observed in small collision systems. In particular, anisotropic flow coefficients measured using two- and four-particle correlations and balance functions are reported in pp collisions at root s = 13.6 TeV. The second- order Fourier coefficient of ir +/-, K +/-, p+p, Lambda+Lambda, K-0(S), and Xi-+Xi+ obtained using the scalar product method exhibits a mass ordering at low transverse momentum when a pseudorapidity gap of divided by Delta eta divided by> 2 is used, being more pronounced for EPOS4. The second harmonic two-particle cumulants of inclusive charged particles decrease with charged-particle multiplicity and depend weakly on divided by Delta eta divided by, while the second harmonic four-particle cumulants are consistent with zero. The balance functions show different responses, being influenced by the different charge production mechanisms.

Femtoscopy of nonidentical particle pairs has been instrumental for precision measurements of both two-particle sources and the final-state interactions in high-energy elementary and heavy-ion collisions. The majority of measurements assessing the source properties are based on identical particle pairs, providing direct access to the characteristics of the single-particle source. The work in this paper demonstrates, via femtoscopy measurements of charged pion-deuteron pairs in Pb-Pb collisions at s NN = 5.02 TeV, the feasibility of accessing the characteristics of the single-particle femtoscopic source by using particle pairs with large mass differences such as pions and deuterons. The first experimental results of the measurement of deuteron source sizes in ultrarelativistic heavy-ion collisions are presented. The results show good agreement with the trend derived from other charged hadrons such as pions, kaons, and protons as a function of transverse mass, indicating similar source properties.

In this letter, we present the first measurement of direct photons at the transverse momentum of 1 < p(T) < 6 GeV/c at midrapidity in inelastic and high-multiplicity proton-proton collisions at a centre-of-mass energy of root s = 13 TeV. The fraction of virtual direct photons in the inclusive virtual photon spectrum is obtained from a fit to the dielectron invariant mass spectrum. In the limit of zero invariant mass, this fraction is equal to the relative contribution of real direct photons in the inclusive real photon spectrum. Contributions from decays of light-flavour neutral mesons are estimated using independent measurements in proton-proton collisions at the same energy and the same event class. For the first time at the LHC energies, a direct-photon signal is observed at low p(T) in both inelastic and high-multiplicity event classes, with a significance of 3.2 sigma and 1.9 sigma in terms of standard deviations, correspondingly. The yield of direct photons in inelastic pp collisions is compared to perturbative QCD calculations. The integrated photon yield is studied as a function of charged-particle multiplicity and is compared to the results from other experiments and theoretical calculations. The results show a significant increase of direct-photon yield with charged-particle multiplicity.

Correlations between event-by-event fluctuations of anisotropic flow harmonics are measured in Pb-Pb collisions at a center-of-mass energy per nucleon pair of 5.02 TeV, as recorded by the ALICE detector at the LHC. This study presents correlations up to the hexagonal flow harmonic v6, which was measured for the first time. The magnitudes of these higher-order correlations are found to vary as a function of collision centrality and harmonic order. These measurements are compared to viscous hydrodynamic model calculations with EKRT initial conditions and to the iEBE-VISHNU model with TRENTo initial conditions. The observed discrepancies between the data and the model calculations vary depending on the harmonic combinations. Due to the sensitivity of model parameters estimated with Bayesian analyses to these higher-order observables, the results presented in this work provide new and independent constraints on the initial conditions and transport properties in theoretical models used to describe the system created in heavy-ion collisions.

The production yields of the orbitally excited charm-strange mesons Ds1(1+)(2536)+ and Ds2*(2+)(2573)+ were measured for the first time in proton-proton (pp) collisions at a center-of-mass energy of s=13 TeV with the ALICE experiment at the LHC. The Ds1+ and Ds2*+ mesons were measured at midrapidity (|y|<0.5) in minimum-bias and high-multiplicity pp collisions in the transverse-momentum interval 2

The correlations between event-by-event fluctuations of symmetry planes are measured in Pb-Pb collisions at a center-of-mass energy per nucleon pair root sNN = 5.02 TeV recorded by the ALICE detector at the Large Hadron Collider. This analysis is conducted using the Gaussian estimator technique, which is insensitive to biases from correlations between different flow amplitudes. The study presents, for the first time, the centrality dependence of correlations involving up to five different symmetry planes. The correlation strength varies depending on the harmonic order of the symmetry plane and the collision centrality. Comparisons with measurements from lower energies indicate no significant differences within uncertainties. Additionally, the results are compared with hydrodynamic model calculations. Although the model predictions provide a qualitative explanation of the experimental results, they overestimate the data for some observables. This is particularly true for correlators that are sensitive to the nonlinear response of the medium to initial-state anisotropies in the collision system. As these new correlators provide unique information-independent of flow amplitudes-their usage in future model developments can further constrain the properties of the strongly interacting matter created in ultrarelativistic heavy-ion collisions.

The first measurement of the e + e − pair production at midrapidity and low invariant mass in central Pb-Pb collisions at s N N = 5.02 TeV at the Large Hadron Collider is presented. The yield of e + e − pairs is compared with a cocktail of expected hadronic decay contributions in the invariant mass ( m e e ) and pair transverse momentum ( p T , e e ) ranges m e e < 3.5 GeV / c 2 and p T , e e < 8 GeV / c . For 0.18 < m e e < 0.5 GeV / c 2 the ratio of data to the cocktail of hadronic contributions amounts to 1.40 ± 0.11 ( stat . ) ± 0.23 ( syst . ) ± 0.16 ( cocktail ) and 1.42 ± 0.11 ( stat . ) ± 0.23 ( syst . ) − 0.29 + 0.24 ( cocktail ) , including or not including medium effects in the estimation of the heavy-flavor background, respectively. It is consistent with predictions from two different models for an additional contribution of thermal e + e − pairs from the hadronic and partonic phases. In the intermediate-mass range ( 1.2 < m e e < 2.6 GeV / c 2 ), the pair transverse impact parameter of the e + e − pairs ( DCA e e , where “DCA” denotes “distance of closest approach”) is used for the first time in Pb-Pb collisions to separate displaced dielectrons from heavy-flavor hadron decays from a possible (thermal) contribution produced at the interaction point. The data are consistent with a suppression of e + e − pairs from c c ¯ and an additional prompt component. Finally, the first direct-photon measurement in the 10% most central Pb-Pb collisions at s N N = 5.02 TeV is reported via the study of virtual direct photons in the transverse momentum range 1 < p T < 5 GeV / c . A model including prompt photons, as well as photons from the preequilibrium and fluid-dynamic phases, can reproduce the result, while being at the upper edge of the data uncertainties.

Details of the nuclear structure of 129Xe, such as the quadrupole deformation and the nuclear diffuseness, are studied by extensive measurements of anisotropic-flow-related observables in Xe–Xe collisions at a centre-of-mass energy per nucleon pair sNN=5.44 TeV with the ALICE detector at the LHC. The results are compared with those from Pb–Pb collisions at sNN=5.02 TeV for a baseline, given that the 208Pb nucleus exhibits a very weak deformation. Furthermore, comprehensive comparisons are performed with a state-of-the-art hybrid model using IP-Glasma+MUSIC+UrQMD. It is found that among various IP-Glasma+MUSIC+UrQMD calculations with different values of nuclear parameters, the one using a nuclear diffuseness parameter of a0=0.492 and a nuclear quadrupole deformation parameter of β2=0.207 provides a better description of the presented flow measurements. These studies represent the first systematic exploration of nuclear structure at TeV energies, utilizing a comprehensive set of anisotropic flow observables. The measurements serve as a critical experimental benchmark for rigorously testing the interplay between nuclear structure inputs and heavy-ion theoretical models.

We report on the measurement of inclusive, non-prompt, and prompt J/ψ-hadron correlations by the ALICE Collaboration at the CERN Large Hadron Collider in pp collisions at a center-of-mass energy of 13 TeV. The correlations are studied at midrapidity (|y| < 0.9) in the transverse momentum ranges pT < 40 GeV/c for the J/ψ and 0.15 < pT < 10 GeV/c and |η| < 0.9 for the associated hadrons. The measurement is based on minimum bias and high multiplicity data samples corresponding to integrated luminosities of Lint = 34 nb−1 and Lint = 6.9 pb−1, respectively. In addition, two more data samples are employed, requiring, on top of the minimum bias condition, a threshold on the tower energy of E = 4 and 9 GeV in the ALICE electromagnetic calorimeters, which correspond to integrated luminosities of Lint = 0.9 pb−1 and Lint = 8.4 pb−1, respectively. The azimuthally integrated near and away side yields of associated charged hadrons per J/ψ trigger are presented as a function of the J/ψ and associated hadron transverse momentum. The measurements are discussed in comparison to PYTHIA calculations.