1,969 research outputs found
Study of Λ(1520) production in pp simulated interactions at 14 TeV with the ALICE detector
No full textThe measurement of hadronic resonances with different lifetimes provides a tool to investigate the time interval between chemical and kinetic freeze-out in heavy ion collisions by examining the influence of the hot dense matter on the resonance yields and properties. The same studies are necessary in pp collisions in order to provide a baseline for heavy ions. Simulated pp events at 14 TeV have been analyzed in order to estimate the capabilities of the ALICE experiment for the Λ(1520) detection. The results show that the reconstruction of this resonance will be possible with a reasonable significance. © 2008 IOP Publishing Ltd
Hadronic resonance production measured by ALICE at the LHC
No full textHadronic resonances with different lifetimes are very useful to probe the hadronic phase of heavy-ion collisions. Due to their relatively short lifetimes compared to the duration of the hadronic phase, resonances are good candidates to investigate the interplay between particle re-scattering and regeneration in the hadronic phase. In addition, having different masses, quantum numbers and quark content, hadronic resonances carry a wealth of information on different aspects of ionion collisions, including the processes that determine the shapes of particle momentum spectra, strangeness production, and the possible onset of collective effects in small systems. We here present the latest results on resonance production in pp, pPb, PbPb and XeXe collisions at different energies. Results include system-size and collision-energy evolution of transverse momentum spectra, integrated yields, mean transverse momenta and particle ratios. These results will be given through comparisons to measurements from lower energy and theoretical models
Neutral meson production measurements with the ALICE at the LHC
No full textIdentified hadron spectra are considered to be sensitive to the transport properties of strongly interacting matter produced in high-energy nucleus-nucleus collisions. π0 and η mesons in ALICE are identified via their two-photon decays by using calorimeters and the central tracking system. In the latter, photons are measured via their conversion to electron-positron pairs in the material of the inner ALICE barrel tracking detectors. The measured production spectra in pp, p–Pb and Pb–Pb collisions at mid–rapidity and over a wide pT range will be presented in the available Large Hadron Collider (LHC) energies of Run I. The resulting nuclear modification factor RAA at different centrality classes shows a clear pattern of strong suppression in the hot QCD medium with respect to pp collisions. Comparison of the ALICE results on neutral mesons with lower-energy experiments is also discussed
Study of the p–p–K + and p–p–K - dynamics using the femtoscopy technique
No full textThe interactions of kaons (K) and antikaons (K ̄) with few nucleons (N) were studied so far using kaonic atom data and measurements of kaon production and interaction yields in nuclei. Some details of the three-body KNN and K ̄ NN dynamics are still not well understood, mainly due to the overlap with multi-nucleon interactions in nuclei. An alternative method to probe the dynamics of three-body systems with kaons is to study the final state interaction within triplet of particles emitted in pp collisions at the Large Hadron Collider, which are free from effects due to the presence of bound nucleons. This Letter reports the first femtoscopic study of p–p–K + and p–p–K - correlations measured in high-multiplicity pp collisions at s = 13 TeV by the ALICE Collaboration. The analysis shows that the measured p–p–K + and p–p–K - correlation functions can be interpreted in terms of pairwise interactions in the triplets, indicating that the dynamics of such systems is dominated by the two-body interactions without significant contributions from three-body effects or bound states
Towards the understanding of the genuine three-body interaction for p-p-p and p-p-Lambda
No full textThree-body nuclear forces play an important role in the structure of nuclei and hypernuclei and are also incorporated in models to describe the dynamics of dense baryonic matter, such as in neutron stars. So far, only indirect measurements anchored to the binding energies of nuclei can be used to constrain the three-nucleon force, and if hyperons are considered, the scarce data on hypernuclei impose only weak constraints on the three-body forces. In this work, we present the first direct measurement of the p–p–p and p–p– Λ systems in terms of three-particle correlation functions carried out for pp collisions at s=13 TeV. Three-particle cumulants are extracted from the correlation functions by applying the Kubo formalism, where the three-particle interaction contribution to these correlations can be isolated after subtracting the known two-body interaction terms. A negative cumulant is found for the p–p–p system, hinting to the presence of a residual three-body effect while for p–p– Λ the cumulant is consistent with zero. This measurement demonstrates the accessibility of three-baryon correlations at the LHC
Study of the p–p–K and p–p–K dynamics using the femtoscopy technique
No full textThe interactions of kaons (K) and antikaons (K)
with few nucleons (N) were studied so far using kaonic
atom data and measurements of kaon production and interaction yields in nuclei. Some details of the three-body KNN
and KNN dynamics are still not well understood, mainly
due to the overlap with multi-nucleon interactions in nuclei.
An alternative method to probe the dynamics of three-body
systems with kaons is to study the final state interaction
within triplet of particles emitted in pp collisions at the Large
Hadron Collider, which are free from effects due to the presence of bound nucleons. This Letter reports the first femtoscopic study of p–p–K+ and p–p–K− correlations measured in high-multiplicity pp collisions at √s = 13 TeV
by the ALICE Collaboration. The analysis shows that the
measured p–p–K+ and p–p–K− correlation functions can be
interpreted in terms of pairwise interactions in the triplets,
indicating that the dynamics of such systems is dominated
by the two-body interactions without significant contributions from three-body effects or bound states
Investigating the p--π± and p--p--π± dynamics with femtoscopy in pp collisions at s=13 TeV
No full textThe interaction between pions and nucleons plays a crucial role in hadron physics. It represents a fundamental building block of the low-energy QCD dynamics and is subject to several resonance excitations. This work studies the p--π± dynamics using femtoscopic correlations in high-multiplicity pp collisions at s=13 TeV measured by ALICE at the LHC. As the final-state interaction between protons and pions is well constrained by scattering experiments and the study of pionic hydrogen, the results give access to information on the particle-emitting source in pp collisions using the femtoscopy methods. The scaling of the source size of primordial protons and pions against their pair transverse mass is extracted. The results are compared with the source sizes studied with p–p, p--K+, and π±–π± pairs by ALICE in the same collision system and are found to be in agreement for the different particle pairs. This reinforces recent findings by ALICE of a common emission source for all hadron-pairs in pp collisions at LHC energies. Furthermore, the p--p--π± systems are studied using three-particle femtoscopy in pp collisions at s=13 TeV. The presence of three-body effects is analyzed utilizing the cumulant expansion method. In this formalism, the known two-body interactions are subtracted in order to isolate the three-body effects. For both, p--p--π+ and p--p--π-, a non-zero cumulant is found, indicating effects beyond pairwise interactions. These results give information on the coupling of the pion to multiple nucleons
p-p, p-Lambda, and Lambda-Lambda correlations studied via femtoscopy in pp reactions at root s=7 TeV
No full textWe report on the first femtoscopic measurement of baryon pairs, such as p-p, p-Λ, and Λ-Λ, measured by ALICE at the Large Hadron Collider (LHC) in proton-proton collisions at s=7TeV. This study demonstrates the feasibility of such measurements in pp collisions at ultrarelativistic energies. The femtoscopy method is employed to constrain the hyperon-nucleon and hyperon-hyperon interactions, which are still rather poorly understood. A new method to evaluate the influence of residual correlations induced by the decays of resonances and experimental impurities is hereby presented. The p-p, p-Λ, and Λ-Λ correlation functions were fitted simultaneously with the help of a new tool developed specifically for the femtoscopy analysis in small colliding systems: Correlation Analysis Tool using the Schrödinger equation (CATS). Within the assumption that in pp collisions the three particle pairs originate from a common source, its radius is found to be equal to r0=1.125±0.018(stat)-0.035+0.058(syst) fm. The sensitivity of the measured p-Λ correlation is tested against different scattering parameters, which are defined by the interaction among the two particles, but the statistics is not sufficient yet to discriminate among different models. The measurement of the Λ-Λ correlation function constrains the phase space spanned by the effective range and scattering length of the strong interaction. Discrepancies between the measured scattering parameters and the resulting correlation functions at LHC and RHIC energies are discussed in the context of various models
Measurement of the production of high-p(T) electrons from heavy-flavour hadron decays in Pb-Pb collisions at root s(NN)=2.76 TeV
No full textElectrons from heavy-flavour hadron decays (charm and beauty) were measured with the ALICE detector in Pb-Pb collisions at a centre-of-mass of energy root s(NN) = 2.76 TeV. The transverse momentum (pT) differential production yields at mid-rapidity were used to calculate the nuclear modification factor R-AA in the interval 3 < p(T) < 18 GeV/c. The R-AA shows a strong suppression compared to binary scaling of pp collisions at the same energy (up to a factor of 4) in the 10% most central Pb-Pb collisions. There is a centrality trend of suppression, and a weaker suppression (down to a factor of 2) in semi-peripheral (50-80%) collisions is observed. The suppression of electrons in this broad p(T) interval indicates that both charm and beauty quarks lose energy when they traverse the hot medium formed in Pb-Pb collisions at LHC. (C) 2017 The Author. Published by Elsevier B.V
Measurement of isolated photon-hadron correlations in √ s NN = 5.02 TeV p p and p -Pb collisions
No full textThis paper presents isolated photon-hadron correlations using pp and p-Pb data collected by the ALICE detector at the LHC. For photons with |η|<0.67 and 12<40 GeV/c, the associated yield of charged particles in the range |η|<0.80 and 0.5<10 GeV/c is presented. These momenta are much lower than previous measurements at the LHC. No significant difference between pp and p-Pb is observed, with Pythia 8.2 describing both data sets within uncertainties. This measurement constrains nuclear effects on the parton fragmentation in p-Pb collisions, and provides a benchmark for future studies of Pb-Pb collisions
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