Accessing the strong interaction between Λ baryons and charged kaons with the femtoscopy technique at the LHC

The interaction between Λ baryons and kaons/antikaons is a crucial ingredient for the strangeness S=0 and S=-2 sector of the meson–baryon interaction at low energies. In particular, the Lambda-Kbar might help in understanding the origin of states such as the Csi(1620), whose nature and properties are still under debate. Experimental data on Lambda-K and Lambda-Kbar systems are scarce, leading to large uncertainties and tension between the available theoretical predictions constrained by such data. In this Letter we present the measurements of Λ–KK− and Λ–KK+ correlations obtained in the high-multiplicity triggered data sample in pp collisions at sqrt(s) = 13 TeV recorded by ALICE at the LHC. The correlation function for both pairs is modeled using the Lednický–Lyuboshits analytical formula and the corresponding scattering parameters are extracted. The Λ–KK+ correlations show the presence of several structures at relative momenta k* above 200 MeV/c, compatible with the Ω baryon, the , and resonances decaying into Λ–K− pairs. The low k* region in the Λ–KK+ also exhibits the presence of the state, expected to strongly couple to the measured pair. The presented data allow to access the ΛK+ and ΛK− strong interaction with an unprecedented precision and deliver the first experimental observation of the decaying into ΛK−

Probing the chiral magnetic wave with charge-dependent flow measurements in Pb-Pb collisions at the LHC

The Chiral MagneticWave (CMW) phenomenon is essential to provide insights into the strong interaction in QCD, the properties of the quark-gluon plasma, and the topological characteristics of the early universe, offering a deeper understanding of fundamental physics in high-energy collisions. Measurements of the charge-dependent anisotropic flow coefficients are studied in Pb-Pb collisions at center-of-mass energy per nucleon-nucleon collision v sNN = 5.02TeV to probe the CMW. In particular, the slope of the normalized difference in elliptic (v2) and triangular (v3) flow coefficients of positively and negatively charged particles as a function of their event-wise normalized number difference, is reported for inclusive and identified particles. The slope rNorm 3 is found to be larger than zero and to have a magnitude similar to rNorm 2, thus pointing to a large background contribution for these measurements. Furthermore, rNorm 2 can be described by a blast wave model calculation that incorporates local charge conservation. In addition, using the event shape engineering technique yields a fraction of CMW (fCMW) contribution to this measurement which is compatible with zero. This measurement provides the very first upper limit for fCMW, and in the 10-60% centrality interval it is found to be 26% (38%) at 95% (99.7%) confidence level

Energy dependence of coherent photonuclear production of J/?? mesons in ultra-peripheral Pb-Pb collisions at sNN \sqrt{{\textrm{s}}_{\textrm{NN}}} = 5.02 TeV

The cross section for coherent photonuclear production of J/ψ is presented as a function of the electromagnetic dissociation (EMD) of Pb. The measurement is performed with the ALICE detector in ultra-peripheral Pb-Pb collisions at a centre-of-mass energy per nucleon pair of √sNN = 5.02 TeV. Cross sections are presented in five different J/ψ rapidity ranges within |y| < 4, with the J/ψ reconstructed via its dilepton decay channels. In some events the J/ψ is not accompanied by EMD, while other events do produce neu- trons from EMD at beam rapidities either in one or the other beam direction, or in both. The cross sections in a given rapidity range and for different configurations of neutrons from EMD allow for the extraction of the energy dependence of this process in the range 17 < Wγ Pb,n < 920 GeV, where Wγ Pb,n is the centre-of-mass energy per nucleon of the γPb system. This range corresponds to a Bjorken-x interval spanning about three orders of magnitude: 1.1 × 10−5 < x < 3.3 × 10−2. In addition to the ultra-peripheral and pho- tonuclear cross sections, the nuclear suppression factor is obtained. These measurements point to a strong depletion of the gluon distribution in Pb nuclei over a broad, previously unexplored, energy range. These results, together with previous ALICE measurements, provide unprecedented information to probe quantum chromodynamics at high energie

Study of flavor dependence of the baryon-to-meson ratio in proton-proton collisions at s=13 TeV

The production cross sections of D0 and Λ+c hadrons originating from beauty-hadron decays (i.e., nonprompt) were measured for the first time at midrapidity (|y|&lt;0.5) by the ALICE Collaboration in proton-proton collisions at a center-of-mass energy √s=13 TeV. They are described within uncertainties by perturbative QCD calculations employing the fragmentation fractions of beauty quarks to baryons measured at forward rapidity by the LHCb Collaboration. The b ̄b production cross section per unit of rapidity at midrapidity, estimated from these measurements, is dσb ̄b/dy||y|&lt;0.5=83.1±3.5(stat)±5.4(syst)+12.3−3.2(extrap) μb. The baryon-to-meson ratios are computed to investigate the hadronization mechanism of beauty quarks. The nonprompt Λ+c/D0 production ratio has a similar trend to the one measured for the promptly produced charmed particles and to the p/π+ and Λ/K0S ratios, suggesting a similar baryon-formation mechanism among light, strange, charm, and beauty hadrons. The pT -integrated nonprompt Λ+c/D0 ratio is found to be significantly higher than the one measured in e+e− collisions

Charm production and fragmentation fractions at midrapidity in pp collisions at s s \sqrt{\textrm{s}} = 13 TeV

Abstract Measurements of the production cross sections of prompt D0, D+, D*+, D s + $${\textrm{D}}_{\textrm{s}}^{+}$$ , Λ c + $${\Lambda}_{\textrm{c}}^{+}$$ , and Ξ c + $${\Xi}_{\textrm{c}}^{+}$$ charm hadrons at midrapidity in proton-proton collisions at s $$\sqrt{s}$$ = 13 TeV with the ALICE detector are presented. The D-meson cross sections as a function of transverse momentum (p T) are provided with improved precision and granularity. The ratios of p T-differential meson production cross sections based on this publication and on measurements at different rapidity and collision energy provide a constraint on gluon parton distribution functions at low values of Bjorken-x (10 −5–10 −4). The measurements of Λ c + $${\Lambda}_{\textrm{c}}^{+}$$ ( Ξ c + $${\Xi}_{\textrm{c}}^{+}$$ ) baryon production extend the measured p T intervals down to p T = 0(3) GeV/c. These measurements are used to determine the charm-quark fragmentation fractions and the c c ¯ $$\textrm{c}\overline{\textrm{c}}$$ production cross section at midrapidity (|y| < 0.5) based on the sum of the cross sections of the weakly-decaying ground-state charm hadrons D0, D+, D s + $${\textrm{D}}_{\textrm{s}}^{+}$$ , Λ c + $${\Lambda}_{\textrm{c}}^{+}$$ , Ξ c 0 $${\Xi}_{\textrm{c}}^0$$ and, for the first time, Ξ c + $${\Xi}_{\textrm{c}}^{+}$$ , and of the strongly-decaying J/ψ mesons. The first measurements of Ξ c + $${\Xi}_{\textrm{c}}^{+}$$ and Σ c 0 , + + $${\Sigma}_{\textrm{c}}^{0,++}$$ fragmentation fractions at midrapidity are also reported. A significantly larger fraction of charm quarks hadronising to baryons is found compared to e+e − and ep collisions. The c c ¯ $$\textrm{c}\overline{\textrm{c}}$$ production cross section at midrapidity is found to be at the upper bound of state-of-the-art perturbative QCD calculations

Accessing the strong interaction between Λ baryons and charged kaons with the femtoscopy technique at the LHC

The interaction between Lambda baryons and kaons/antikaons is a crucial ingredient for the strangeness S= 0 and S= -2 sector of the meson-baryon interaction at low energies. In particular, the Lambda(K) over bar might help in understanding the origin of states such as the Xi(1620), whose nature and properties are still under debate. Experimental data on Lambda-K and Lambda-(K) over bar systems are scarce, leading to large uncertainties and tension between the available theoretical predictions constrained by such data. In this Letter we present the measurements of Lambda-K+ circle plus (Lambda) over bar -K- and Lambda-K- circle plus (Lambda) over bar -K+ correlations obtained in the high-multiplicity triggered data sample in pp collisions at root s= 13TeV recorded by ALICE at the LHC. The correlation function for both pairs is modeled using the Lednicky-Lyuboshits analytical formula and the corresponding scattering parameters are extracted. The Lambda-K- circle plus (Lambda) over bar -K+ correlations show the presence of several structures at relative momenta k* above 200 MeV/c, compatible with the Omega baryon, the Xi(1690), and Xi(1820) resonances decaying into Lambda-K- pairs. The low k* region in the Lambda-K- circle plus (Lambda) over bar -K+ also exhibits the presence of the Xi(1620) state, expected to strongly couple to the measured pair. The presented data allow to access the Lambda K+ and Lambda K- strong interaction with an unprecedented precision and deliver the first experimental observation of the Xi(1620) decaying into Lambda K-. (c) 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP3

Energy dependence of coherent photonuclear production of J/ψ mesons in ultra-peripheral Pb-Pb collisions at s NN sNN \sqrt{{\textrm{s}}_{\textrm{NN}}} = 5.02 TeV

Abstract The cross section for coherent photonuclear production of J/ψ is presented as a function of the electromagnetic dissociation (EMD) of Pb. The measurement is performed with the ALICE detector in ultra-peripheral Pb-Pb collisions at a centre-of-mass energy per nucleon pair of s NN $$\sqrt{{\textrm{s}}_{\textrm{NN}}}$$ = 5.02 TeV. Cross sections are presented in five different J/ψ rapidity ranges within |y| < 4, with the J/ψ reconstructed via its dilepton decay channels. In some events the J/ψ is not accompanied by EMD, while other events do produce neutrons from EMD at beam rapidities either in one or the other beam direction, or in both. The cross sections in a given rapidity range and for different configurations of neutrons from EMD allow for the extraction of the energy dependence of this process in the range 17 < W γ Pb,n < 920 GeV, where W γ Pb,n is the centre-of-mass energy per nucleon of the γPb system. This range corresponds to a Bjorken-x interval spanning about three orders of magnitude: 1.1 × 10 −5 < x < 3.3 × 10 −2. In addition to the ultra-peripheral and photonuclear cross sections, the nuclear suppression factor is obtained. These measurements point to a strong depletion of the gluon distribution in Pb nuclei over a broad, previously unexplored, energy range. These results, together with previous ALICE measurements, provide unprecedented information to probe quantum chromodynamics at high energies

Energy dependence of coherent photonuclear production of J/ψ mesons in ultra-peripheral Pb-Pb collisions at √sNN = 5.02 TeV

The cross section for coherent photonuclear production of J/ψ is presented as a function of the electromagnetic dissociation (EMD) of Pb. The measurement is performed with the ALICE detector in ultra-peripheral Pb-Pb collisions at a centre-of-mass energy per nucleon pair of sNN = 5.02 TeV. Cross sections are presented in five different J/ψ rapidity ranges within |y| < 4, with the J/ψ reconstructed via its dilepton decay channels. In some events the J/ψ is not accompanied by EMD, while other events do produce neutrons from EMD at beam rapidities either in one or the other beam direction, or in both. The cross sections in a given rapidity range and for different configurations of neutrons from EMD allow for the extraction of the energy dependence of this process in the range 17 < Wγ Pb,n < 920 GeV, where Wγ Pb,n is the centre-of-mass energy per nucleon of the γPb system. This range corresponds to a Bjorken-x interval spanning about three orders of magnitude: 1.1 × 10 −5 < x < 3.3 × 10 −2. In addition to the ultra-peripheral and photonuclear cross sections, the nuclear suppression factor is obtained. These measurements point to a strong depletion of the gluon distribution in Pb nuclei over a broad, previously unexplored, energy range. These results, together with previous ALICE measurements, provide unprecedented information to probe quantum chromodynamics at high energies. [Figure not available: see fulltext.