Engineering Papers⌕ Search

Engineering topics

Arnaldi, R.

Publications and source records attributed to Arnaldi, R..

At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Insight into particle production mechanisms via angular correlations of identified particles in pp collisions at $\sqrt{\mathrm{s}}=7$ TeV

We measured two-particle angular correlations in pp collisions at √s=7 TeV for pions, kaons, protons, and lambdas, for all particle/anti-particle combinations in the pair. Data for mesons exhibit an expected peak dominated by effects associated with mini-jets and are well reproduced by general purpose Monte Carlo generators. However, for baryon–baryon and anti-baryon–anti-baryon pairs, where both particles have the same baryon number, a near-side anti-correlation structure is observed instead of a peak. This effect is interpreted in the context of baryon production mechanisms in the fragmentation process. It currently presents a challenge to Monte Carlo models and its origin remains an open question.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Measurement of D-meson production at mid-rapidity in pp collisions at ${\sqrt{s}=7}$ TeV

The production cross sections for prompt charmed mesons D 0 , D + , D * + and Ds+ were measured at mid-rapidity in proton–proton collisions at a centre-of-mass energy s=7TeV with the ALICE detector at the Large Hadron Collider (LHC). D mesons were reconstructed from their decays D 0 → K - π + , D + → K - π + π + , D * + → D 0 π + , D$+\atop{s}$→K - K + π + , and their charge conjugates.With respect to previous measurements in the same rapidity region, the coverage in transverse momentum (p T ) is extended and the uncertainties are reduced by a factor of about two. The accuracy on the estimated total c$\bar{c}$ production cross section is likewise improved. The measured p T -differential cross sections are compared with the results of three perturbative QCD calculations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Linear and non-linear flow mode in Pb–Pb collisions at s NN = 2.76 TeV

The second and the third order anisotropic flow, V 2 and V 3 , are mostly determined by the corresponding initial spatial anisotropy coefficients, and , in the initial density distribution. In addition to their dependence on the same order initial anisotropy coefficient, higher order anisotropic flow, V n (n > 3), can also have a significant contribution from lower order initial anisotropy coefficients, which leads to mode-coupling effects. In this Letter we investigate the linear and non-linear modes in higher order anisotropic flow V n for n = 4, 5, 6 with the ALICE detector at the Large Hadron Collider. The measurements are done for particles in the pseudorapidity range |η| < 0.8 and the transverse momentum range 0.2 < p T < 5.0 GeV/c as a function of collision centrality. The results are compared with theoretical calculations and provide important constraints on the initial conditions, including initial spatial geometry and its fluctuations, as well as the ratio of the shear viscosity to entropy density of the produced system.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2017

Measurement of electrons from beauty-hadron decays in p-Pb collisions at $ \sqrt{s_{\mathrm{NN}}}=5.02 $ TeV and Pb-Pb collisions at $ \sqrt{s_{\mathrm{NN}}}=2.76 $ TeV

The production of beauty hadrons was measured via semi-leptonic decays at mid-rapidity with the ALICE detector at the LHC in the transverse momentum interval 1 s NN = 5.02 TeV and in 1.3 < pT< 8 GeV/c in the 20% most central Pb-Pb collisions at √ s NN = 2.76 TeV. The pp reference spectra at √ s NN = 5.02 TeV and √s = 2.76 TeV, needed for the calculation of the nuclear modification factors R pPb and R PbPb , were obtained by a pQCD-driven scaling of the cross section of electrons from beauty-hadron decays measured at √s = 7 TeV. In the p T interval 3 < p T < 8 GeV/c, a suppression of the yield of electrons from beauty-hadron decays is observed in Pb-Pb compared to pp collisions. Towards lower p T , the R PbPb values increase with large systematic uncertainties. The R pPb is consistent with unity within systematic uncertainties and is well described by theoretical calculations that include cold nuclear matter effects in p-Pb collisions. The measured R pPb and these calculations indicate that cold nuclear matter effects are small at high transverse momentum also in Pb-Pb collisions. Therefore, the observed reduction of R PbPb below unity at high p T may be ascribed to an effect of the hot and dense medium formed in Pb-Pb collisions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Energy dependence of forward-rapidity $\mathrm {J}/\psi $ and $\psi \mathrm {(2S)}$ production in pp collisions at the LHC

We present results on transverse momentum (p T ) and rapidity (y) differential production cross sections, mean transverse momentum and mean transverse momentum square of inclusive J/ψ and ψ(2S) at forward rapidity (2.5 < y < 4) as well as ψ(2S)-to-J/ψ cross section ratios. These quantities are measured in pp collisions at center of mass energies √s = 5.02 and 13 TeV with the ALICE detector. Both charmonium states are reconstructed in the dimuon decay channel, using the muon spectrometer. A comprehensive comparison to inclusive charmonium cross sections measured at √s = 2.76, 7 and 8 TeV is performed. A comparison to non-relativistic quantum chromodynamics and fixed-order next-to-leading logarithm calculations, which describe prompt and non-prompt charmonium production respectively, is also presented. A good description of the data is obtained over the full p T range, provided that both contributions are summed. In particular, it is found that for p T > 15 GeV/c the non-prompt contribution reaches up to 50% of the total charmonium yield.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Production of ${\Sigma (1385)^{\pm }}$ and ${\Xi (1530)^{0}}$ in p–Pb collisions at ${\sqrt{s_{\mathrm{NN}}}= 5.02}$ TeV

The transverse momentum distributions of the strange and double-strange hyperon resonances (Σ(1385) ± , Ξ(1530) 0 ) produced in p–Pb collisions at √ s NN = 5.02 TeV were measured in the rapidity range –0.5 < y CMS < 0 for event classes corresponding to different charged-particle multiplicity densities, < dN ch /dη lab >. The mean transverse momentum values are presented as a function of < dN ch /dη lab >, as well as a function of the particle masses and compared with previous results on hyperon production. The integrated yield ratios of excited to ground-state hyperons are constant as a function of < dN ch /dη lab >. The equivalent ratios to pions exhibit an increase with < dN ch /dη lab >, depending on their strangeness content.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Production of ${\pi ^0}$ and $\eta $ mesons up to high transverse momentum in pp collisions at 2.76 TeV

The invariant differential cross sections for inclusive π 0 and η mesons at midrapidity were measured in pp collisions at √s=2.76 TeV for transverse momenta 0.4 < p T < 40 GeV/c and 0.6 < p T < 20 GeV/c, respectively, using the ALICE detector. This large range in p T was achieved by combining various analysis techniques and different triggers involving the electromagnetic calorimeter (EMCal). Particularly, a new single-cluster, shower-shape based method was developed for the identification of high-p T neutral pions, which exploits that the showers originating from their decay photons overlap in the EMCal. Above 4 GeV/c, the measured cross sections are found to exhibit a similar power-law behavior with an exponent of about 6.3. Next-to-leading-order perturbative QCD calculations differ from the measured cross sections by about 30% for the π 0 , and between 30–50% for the η meson, while generator-level simulations with PYTHIA 8.2 describe the data to better than 10–30%, except at p T < 1 GeV/c. The new data can therefore be used to further improve the theoretical description of π 0 and η meson production.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Heavy-flavor production and medium properties in high-energy nuclear collisions --What next?

Open and hidden heavy-flavor physics in high-energy nuclear collisions are entering a new and exciting stage towards reaching a clearer understanding of the new experimental results with the possibility to link them directly to the advancement in lattice Quantum Chromo-Dynamics (QCD). Some recent results from experiments and theoretical developments regarding open and hidden heavy-flavor dynamics have been debated at the Lorentz Workshop Tomography of the Quark-Gluon Plasma with Heavy Quarks, which was held in October 2016 in Leiden, The Netherlands. Here, we summarize identified common understandings and developed strategies for the upcoming five years, which aim at achieving a profound knowledge of the dynamical properties of the quark-gluon plasma.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Measurement of azimuthal correlations of D mesons with charged particles in pp collisions at √s = 7 TeV and p–Pb collisions at √s NN = 5.02 TeV

The azimuthal correlations of D mesons with charged particles were measured with the ALICE apparatus in pp collisions at s = 7 &#xA0; T e V and p–Pb collisions at s N N = 5.02 &#xA0; T e V at the Large Hadron Collider. D 0 , D + , and D &#x2217;<!-- * --> + mesons and their charge conjugates with transverse momentum 3 < p T < 16 &#xA0; G e V / c and rapidity in the nucleon-nucleon centre-of-mass system | y c m s | < 0.5 (pp collisions) and &#x2212;<!-- - --> 0.96 < y c m s < 0.04 (p–Pb collisions) were correlated to charged particles with p T > 0.3 &#xA0; G e V / c . The yield of charged particles in the correlation peak induced by the jet containing the D meson and the peak width are compatible within uncertainties in the two collision systems. The data are described within uncertainties by Monte-Carlo simulations based on PYTHIA, POWHEG, and EPOS 3 event generators.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Production of muons from heavy-flavour hadron decays in p–Pb collisions at s NN = 5.02 TeV

The production of muons from heavy-flavour hadron decays in p–Pb collisions at √ s NN = 5.02 TeV was studied for 2< p T <16 GeV/c with the ALICE detector at the CERN LHC. The measurement was performed at forward (p-going direction) and backward (Pb-going direction) rapidity, in the ranges of rapidity in the centre-of-mass system (cms) 2.03 cms <3.53 and –4.46 cms <–2.96, respectively. The production cross sections and nuclear modification factors are presented as a function of transverse momentum (p T ). At forward rapidity, the nuclear modification factor is compatible with unity while at backward rapidity, in the interval 2.5 < p T < 3.5 GeV/c, it is above unity by more than 2σ. The ratio of the forward-to-backward production cross sections is also measured in the overlapping interval 2.96<|y cms | < 3.53 and is smaller than unity by 3.7σ in 2.5< p T <3.5 GeV/c. The data are described by model calculations including cold nuclear matter effects.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗