This paper presents the energy dependence of multiplicity and net-electric charge fluctuations in p+p interactions at beam momenta 20, 31, 40, 80, and 158 Ge V /c . Results are corrected for the experimental biases and quantified with the use of cumulants and factorial cumulants. Cumulant ratios are an essential tool in the search for the critical point of strongly interacting matter in heavy ion collisions. Measurements performed in p+p interactions provide a vital baseline estimation in these studies. The measured signals are compared with the string hadronic models Epos1.99 and FTFP-BERT.

The Spin Physics Detector collaboration proposes to install a universal detector in the second interaction point of the NICA collider under construction (JINR, Dubna) to study the spin structure of the proton and deuteron and other spin-related phenomena using a unique possibility to operate with polarized proton and deuteron beams at a collision energy up to 27 GeV and a luminosity up to 10^32 cm^-2 s^-1. As the main goal, the experiment aims to provide access to the gluon TMD PDFs in the proton and deuteron, as well as the gluon transversity distribution and tensor PDFs in the deuteron, via the measurement of specific single and double spin asymmetries using different complementary probes such as charmonia, open charm, and prompt photon production processes. Other polarized and unpolarized physics is possible, especially at the first stage of NICA operation with reduced luminosity and collision energy of the proton and ion beams. This document is dedicated exclusively to technical issues of the SPD setup construction.

Proton computed tomography (pCT) is an imaging reconstruction technique that uses protons’ positions, directions, and energy loss to generate a map of an object’s relative stopping power. In this work, the trigger-controlling system was designed and constructed to synchronize between components of our proposed pCT prototype and a proton beam at King Chulalongkorn Memorial Hospital (KCMH) in Bangkok. The controlling system can control the proton beam gating, a rotational stage, and ALPIDE sensors, which are parts of a tracker and a proton calorimeter of the pCT prototype. The controlling system was constructed based on the MEGA2560 microcontroller unit. The controlling system was verified by measuring the activated rows of the ALPIDE sensor at different proton extraction times. Additionally, the controlling system can control an array of six ALPIDE sensors, which could provide preliminary results of the proton calorimeter prototype.

Measurements of K_S^0 meson production via its π^+π^- decay mode in inelastic p+p interactions at incident projectile momenta of 31, 40 and 80 GeV/c (√(s_NN)=7.7, 8.8 and 12.3 GeV, respectively) are presented. The data were recorded by the NA61/SHINE spectrometer at the CERN Super Proton Synchrotron. Double-differential distributions were obtained in transverse momentum and rapidity. The mean multiplicities of K_S^0 mesons were determined to be (5.95 ± 0.19 (stat) ± 0.22 (sys)) × 10^-2 at 31 GeV/c, (7.61 ± 0.13 (stat) ± 0.31 (sys)) × 10^-2 at 40 GeV/c and (11.58 ± 0.12 (stat) ± 0.37 (sys)) × 10^-2 at 80 GeV/c. The results on K^0_S production are compared with model calculations (Epos1.99, SMASH 2.0 and PHSD) as well as with published data from other experiments.

Abstract The azimuthal anisotropy of particles associated with jets (jet particles) at midrapidity is measured for the first time in p-Pb and Pb-Pb collisions at $$ \sqrt{{\textrm{s}}_{\textrm{NN}}} $$ s NN = 5.02 TeV down to transverse momentum (pT) of 0.5 GeV/c and 2 GeV/c, respectively, with ALICE. The results obtained in p-Pb collisions are based on a novel three-particle correlation technique. The azimuthal anisotropy coefficient v2 in high-multiplicity p-Pb collisions is positive, with a significance reaching 6.8σ at low pT, and its magnitude is smaller than in semicentral Pb-Pb collisions. In contrast to the measurements in Pb-Pb collisions, the v2 coefficient is also found independent of pT within uncertainties. Comparisons with the inclusive charged-particle v2 and with AMPT calculations are discussed. The predictions suggest that parton interactions play an important role in generating a non-zero jet-particle v2 in p-Pb collisions, even though they overestimate the reported measurement. These observations shed new insights on the understanding of the origin of the collective behaviour of jet particles in small systems such as p-Pb collisions, and provide significant stringent new constraints to models.

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 Dπ 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 Dπ 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

Abstract The yields of $$K^0_S$$ K S 0 mesons have been measured in inelastic p+p interactions at incident projectile momenta of 31, 40 and 80 $$\text {Ge}\hspace{-1.00006pt}\text {V}\!/\!c$$ Ge V / c ( $$\sqrt{s_{NN}}=7.7, 8.8$$ s NN = 7.7 , 8.8 and 12.3 $$\text {Ge}\hspace{-1.00006pt}\text {V}$$ Ge V , respectively). The data were recorded by the NA61 $$/$$ / SHINE spectrometer at the CERN Super Proton Synchrotron and the $$K^0_S$$ K S 0 mesons identified via their decays into $$\pi ^{+} \pi ^{-}$$ π + π - pairs. Double-differential distributions are presented as function of transverse momentum and rapidity. The mean multiplicities of $$K^0_S$$ K S 0 mesons were determined to be $$(5.95 \pm 0.19 (stat) \pm 0.30 (sys)) \times 10^{-2}$$ ( 5.95 ± 0.19 ( s t a t ) ± 0.30 ( s y s ) ) × 10 - 2 at 31 $$\text {Ge}\hspace{-1.00006pt}\text {V}\!/\!c$$ Ge V / c , $$(7.61 \pm 0.13 (stat) \pm 0.43 (sys)) \times 10^{-2}$$ ( 7.61 ± 0.13 ( s t a t ) ± 0.43 ( s y s ) ) × 10 - 2 at 40 $$\text {Ge}\hspace{-1.00006pt}\text {V}\!/\!c$$ Ge V / c and $$(11.58 \pm 0.12 (stat) \pm 0.55 (sys)) \times 10^{-2}$$ ( 11.58 ± 0.12 ( s t a t ) ± 0.55 ( s y s ) ) × 10 - 2 at 80 $$\text {Ge}\hspace{-1.00006pt}\text {V}\!/\!c$$ Ge V / c . The results on $$K^{0}_{S}$$ K S 0 production are compared with the production of charged kaons in corresponding reactions and with model calculations (Epos1.99, SMASH 2.0 and PHSD) as well as with published data from other experiments.

Collective behavior has been observed in high-energy heavy-ion collisions for several decades. Collectivity is driven by the high particle multiplicities that are produced in these collisions. At the CERN Large Hadron Collider (LHC), features of collectivity have also been seen in high-multiplicity proton-proton collisions that can attain particle multiplicities comparable to peripheral Pb-Pb collisions. One of the possible signatures of collective behavior is the decrease of femtoscopic radii extracted from pion and kaon pairs emitted from highmultiplicity collisions with increasing pair transverse momentum. This decrease can be described in terms of an approximate transverse mass scaling. In the present work, femtoscopic analyses are carried out by the ALICE Collaboration on charged pion and kaon pairs produced in pp collisions at root s = 13 TeV from the LHC to study possible collectivity in pp collisions. The event-shape analysis method based on transverse sphericity is used to select for spherical versus jetlike events, and the effects of this selection on the femtoscopic radii for both charged pion and kaon pairs are studied. This is the first time this selection method has been applied to charged kaon pairs. An approximate transverse-mass scaling of the radii is found in all multiplicity ranges studied when the difference in the Lorentz boost for pions and kaons is taken into account. This observation does not support the hypothesis of collective expansion of hot and dense matter that should only occur in high-multiplicity events. A possible alternate explanation of the present results is based on a scenario of common emission conditions for pions and kaons in pp collisions for the multiplicity ranges studied.

A method based on Bayes’ formula was used to estimate the relative error in determining the number of spectator nucleons from the energy measured in a calorimeter during the collision of relativistic nuclei. The minimum possible relative error in determining the number of spectator nucleons in an event is obtained for an arbitrary distribution of spectators.

Long- and short-range correlations for pairs of charged particles are studied via two-particle angular correlations in pp collisions at √(s) = 13 TeV and p–Pb collisions at √(s_NN) = 5.02 TeV. The correlation functions are measured as a function of relative azimuthal angle ∆φ and pseudorapidity separation ∆η for pairs of primary charged particles within the pseudorapidity interval |η| < 0.9 and the transverse-momentum interval 1 < pT < 4 GeV/c. Flow coefficients are extracted for the long-range correlations (1.6 < |∆η| < 1.8) in various high-multiplicity event classes using the low-multiplicity template fit method. The method is used to subtract the enhanced yield of away-side jet fragments in high-multiplicity events. These results show decreasing flow signals toward lower multiplicity events. Furthermore, the flow coefficients for events with hard probes, such as jets or leading particles, do not exhibit any significant changes compared to those obtained from high-multiplicity events without any specific event selection criteria. The results are compared with hydrodynamic-model calculations, and it is found that a better understanding of the initial conditions is necessary to describe the results, particularly for low-multiplicity events.

The inclusive production of the charm-strange baryon Omega(0)(c) is measured for the first time via its semileptonic decay into Omega(-)e(+)nu(e) at midrapidity (vertical bar y vertical bar < 0.8) in proton-proton (pp) collisions at the center-of-mass energy root s =13 TeV with the ALICE detector at the LHC. The transverse momentum (pT) differential cross section multiplied by the branching ratio is presented in the interval 2 < p(T) < 12 GeV=c. The branching-fraction ratio BR(Omega(0)(c) -> Omega(-)e(+)nu(e))/BR(Omega(0)(c) -> Omega(-)pi(+)) is measured to be 1.12 +/- 0.22 (stat) +/- 0.27 (syst). Comparisons with other experimental measurements, as well as with theoretical calculations, are presented.

The ALICE Collaboration reports the measurement of semi-inclusive distributions of charged-particle jets recoiling from a high transverse momentum (high p_{T}) hadron trigger in proton-proton and central Pb-Pb collisions at sqrt[s_{NN}]=5.02  TeV. A data-driven statistical method is used to mitigate the large uncorrelated background in central Pb-Pb collisions. Recoil jet distributions are reported for jet resolution parameter R=0.2, 0.4, and 0.5 in the range 7<p_{T,jet}<140  GeV/c and trigger-recoil jet azimuthal separation π/2<Δφ<π. The measurements exhibit a marked medium-induced jet yield enhancement at low p_{T} and at large azimuthal deviation from Δφ∼π. The enhancement is characterized by its dependence on Δφ, which has a slope that differs from zero by 4.7σ. Comparisons to model calculations incorporating different formulations of jet quenching are reported. These comparisons indicate that the observed yield enhancement arises from the response of the QGP medium to jet propagation.

AbstractThe first measurement of the multiplicity dependence of intra-jet properties of leading charged-particle jets in proton–proton (pp) collisions is reported. The mean charged-particle multiplicity and jet fragmentation distributions are measured in minimum-bias and high-multiplicity pp collisions at center-of-mass energy $$\sqrt{s}$$ s = 13 TeV using the ALICE detector. Jets are reconstructed from charged particles produced in the midrapidity region ($$|\eta | < 0.9$$ | η | < 0.9 ) using the sequential recombination anti-$$k_{\textrm{T}}$$ k T algorithm with jet resolution parameters R = 0.2, 0.3, and 0.4 for the transverse momentum ($$p_\textrm{T}$$ p T ) interval 5–110 GeV/c. The high-multiplicity events are selected by the forward V0 scintillator detectors. The mean charged-particle multiplicity inside the leading jet cone rises monotonically with increasing jet $$p_\textrm{T}$$ p T in qualitative agreement with previous measurements at lower energies. The distributions of jet fragmentation function variables $$z^{\textrm{ch}}$$ z ch and $$\xi ^{\textrm{ch}}$$ ξ ch are measured for different jet-$$p_\textrm{T}$$ p T intervals. Jet-$$p_\textrm{T}$$ p T independent fragmentation of leading jets is observed for wider jets except at high- and low-$$z^{\textrm{ch}}$$ z ch values. The observed “hump-backed plateau” structure in the $$\xi ^{\textrm{ch}}$$ ξ ch distribution indicates suppression of low-$$p_\textrm{T}$$ p T particles. In high-multiplicity events, an enhancement of the fragmentation probability of low-$$z^{\textrm{ch}}$$ z ch particles accompanied by a suppression of high-$$z^{\textrm{ch}}$$ z ch particles is observed compared to minimum-bias events. This behavior becomes more prominent for low-$$p_\textrm{T}$$ p T jets with larger jet radius. The results are compared with predictions of QCD-inspired event generators, PYTHIA 8 with Monash 2013 tune and EPOS LHC. It is found that PYTHIA 8 qualitatively reproduces the jet modification in high-multiplicity events except at high jet $$p_\textrm{T}$$ p T . These measurements provide important constraints to models of jet fragmentation.

We present geometry-based corrections to estimates of the Bjorken energy density in a broad range of heavy-ion collision energies (from RHIC to the LHC) considereing non-circular shape of the nuclei overlap area in case of events selected in 0-5% centrality classes. We compare the updated Bjorken energy excitation function, obtained in our study for these very central A-A collisions, to the previously obtained ones. We present also and discuss the relevant energy dependences of pion, kaon and proton contributions to the Bjorken energy density that are also estimated in our study.

The NA61/SHINE experiment at the CERN Super Proton Synchrotron studies the onset of deconfinement in strongly interacting matter through a beam energy scan of particle production in collisions of nuclei of varied sizes. This paper presents results on inclusive double-differential spectra, transverse momentum and rapidity distributions and mean multiplicities of π ^± , K^± , p and p̅ produced in ^40Ar+^45Sc collisions at beam momenta of 13A, 19A, 30A, 40A, 75A and 150A Ge V /c . The analysis uses the 10 K^± / π ^± ratios as well as of inverse slope parameters of the K^± transverse mass distributions are placed in between those found in inelastic p+p and central Pb + Pb collisions. The results obtained here establish a system-size dependence of hadron production properties that so far cannot be explained either within statistical or dynamical models.

We use the available data on ⟨dN/ . -0emdy⟩ and ⟨p_T⟩ for the identified hadrons including π^ + + π^ - , K^ + + K^ - , p + p̅ , K*(892)^0 , K*(892)^0 and φ-mesons, registered at midrapidity (| y | < 0.5) in 0–5 ss̅ quarks) and K‑meson (containing single s-quark), are of specific interest because they might have different production mechanisms and differ in sensitivity to the properties of the QGP-medium formed in relativistic heavy-ion collisions.

The yields of K^0_S mesons have been measured in inelastic p+p interactions at incident projectile momenta of 31, 40 and 80 GeV/c ( √(s_NN)=7.7, 8.8 and 12.3 GeV , respectively). The data were recorded by the NA61 / SHINE spectrometer at the CERN Super Proton Synchrotron and the K^0_S mesons identified via their decays into π ^+π ^- pairs. Double-differential distributions are presented as function of transverse momentum and rapidity. The mean multiplicities of K^0_S mesons were determined to be (5.95 ± 0.19 (stat) ± 0.30 (sys)) × 10^-2 at 31 GeV/c , (7.61 ± 0.13 (stat) ± 0.43 (sys)) × 10^-2 at 40 GeV/c and (11.58 ± 0.12 (stat) ± 0.55 (sys)) × 10^-2 at 80 GeV/c . The results on K^0_S production are compared with the production of charged kaons in corresponding reactions and with model calculations (Epos1.99, SMASH 2.0 and PHSD) as well as with published data from other experiments.

Abstract The critical point of strongly interacting matter is searched for at the CERN SPS by the NA61/SHINE experiment in central $$^{40}$$ 40 Ar + $$^{45}$$ 45 Sc collisions at 13 A, 19 A, 30 A, 40 A, and 75 A GeV/c. The dependence of the second-order scaled factorial moments of proton multiplicity distributions on the number of subdivisions in transverse momentum space is measured. The intermittency analysis uses statistically independent data sets for every subdivision in transverse and cumulative-transverse momentum variables. The results obtained do not indicate the searched intermittent pattern. An upper limit on the fraction of correlated protons and the intermittency index is obtained based on a comparison with the Power-law Model.

The modern vertex detectors based on silicon sensors (tracking systems of leading experiments at the Large Hadron Collider and vertex detectors of the MPD and SPD experiments at the NICA accelerator complex) are discussed. The development of concepts for new detector systems using thin silicon pixel detectors for the precision identification of charmed hadrons decay vertices is considered. Results from developing cooling systems for large-area ultrathin silicon detector modules and studies of the properties and characteristics of silicon pixel sensors based on CMOS technology are presented in the context of detecting rare decays of hadrons containing heavy quarks.

The first measurements of femtoscopic correlations with the particle pair combinations pi +/- K-S(0) in pp collisions at root s = 13 TeV at the Large Hadron Collider (LHC) are reported by the ALICE experiment. Using the femtoscopic approach, it is shown that it is possible to study the elusive K-0*(700) particle that has been considered a tetraquark candidate for over forty years. Source and final-state interaction parameters are extracted by fitting a model assuming a Gaussian source to the experimentally measured two-particle correlation functions. The final-state interaction in the pi +/- K-S(0) system is modeled through a resonant scattering amplitude, defined in terms of a mass and a coupling parameter, The extracted mass and Breit-Wigner width, derived from the coupling parameter, of the final-state interaction are found to be consistent with previous measurements of the K-0*(700). The small value and increase of the correlation strength with increasing source size support the hypothesis that the K-0*(700) is a four-quark state, i.e. a tetraquark state of the form (q(1), (q(2)) over bar, q(3), (q(3)) over bar) in which q(1), q(2) and q(3) indicate the flavor of the valence quarks of the pi and K-S(0). This latter trend is also confirmed via a simple geometric model that assumes a tetraquark structure of the K-0*(700) resonance.