122 research outputs found

    Energy dependence of ϕ meson production at forward rapidity in pp collisions at the LHC

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    The production of ϕ\phi mesons has been studied in pp collisions at LHC energies with the ALICE detector via the dimuon decay channel in the rapidity region 2.5<y<42.5< y < 4. Measurements of the differential cross section d2σ/dydpT\mathrm{d}^2\sigma /\mathrm{d}y \mathrm{d}p_{\mathrm {T}} are presented as a function of the transverse momentum (pTp_{\mathrm {T}}) at the center-of-mass energies s=5.02\sqrt{s}=5.02, 8 and 13 TeV and compared with the ALICE results at midrapidity. The differential cross sections at s=5.02\sqrt{s}=5.02 and 13 TeV are also studied in several rapidity intervals as a function of pTp_{\mathrm {T}}, and as a function of rapidity in three pTp_{\mathrm {T}} intervals. A hardening of the pTp_{\mathrm {T}}-differential cross section with the collision energy is observed, while, for a given energy, pTp_{\mathrm {T}} spectra soften with increasing rapidity and, conversely, rapidity distributions get slightly narrower at increasing pTp_{\mathrm {T}}. The new results, complementing the published measurements at s=2.76\sqrt{s}=2.76 and 7 TeV, allow one to establish the energy dependence of ϕ\phi meson production and to compare the measured cross sections with phenomenological models. None of the considered models manages to describe the evolution of the cross section with pTp_{\mathrm {T}} and rapidity at all the energies.publishedVersio

    First measurement of Ωc0 production in pp collisions at s=13 TeV

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    The inclusive production of the charm–strange baryon 0 c is measured for the first time via its hadronic √ decay into −π+ at midrapidity (|y| &lt;0.5) in proton–proton (pp) collisions at the centre-of-mass energy 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 &lt; pT &lt; 12 GeV/c. The pT dependence of the 0 c-baryon production relative to the prompt D0-meson and to the prompt 0 c-baryon production is compared to various models that take different hadronisation mechanisms into consideration. In the measured pT interval, the ratio of the pT-integrated cross sections of 0 c and prompt + c baryons multiplied by the −π+ branching ratio is found to be larger by a factor of about 20 with a significance of about 4σ when compared to e+e− collisions

    Elliptic flow of charged particles at midrapidity relative to the spectator plane in Pb–Pb and Xe–Xe collisions

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    Measurements of the elliptic flow coefficient relative to the collision plane defined by the spectator neutrons v2{ SP} in collisions of Pb ions at center-of-mass energy per nucleon–nucleon pair √ 2.76 TeV and Xe ions at √ sNN = sNN =5.44 TeV are reported. The results are presented for charged particles produced at midrapidity as a function of centrality and transverse momentum for the 5–70% and 0.2–6 GeV/c ranges, respectively. The ratio between v2{ SP} and the elliptic flow coefficient relative to the participant plane v2{4}, estimated using four-particle correlations, deviates by up to 20% from unity depending on centrality. This observation differs strongly from the magnitude of the corresponding eccentricity ratios predicted by the TRENTo and the elliptic power models of initial state fluctuations that are tuned to describe the participant plane anisotropies. The differences can be interpreted as a decorrelation of the neutron spectator plane and the reaction plane because of fragmentation of the remnants from the colliding nuclei, which points to an incompleteness of current models describing the initial state fluctuations. A significant transverse momentum dependence of the ratio v2{ SP}/v2{4} is observed in all but the most central collisions, which may help to understand whether momentum anisotropies at low and intermediate transverse momentum have a common origin in initial state f luctuations. The ratios of v2{ SP} and v2{4} to the corresponding initial state eccentricities for Xe–Xe and Pb–Pb collisions at similar initial entropy density show a difference of (7.0 ±0.9)%with an additional variation of +1.8% when including RHIC data in the TRENTo parameter extraction. These observations provide new experimental constraints for viscous effects in the hydrodynamic modeling of the expanding quark–gluon plasma produced in heavy-ion collisions at the LHC

    Effect of moderate alcohol consumption on parameters of reverse cholesterol transport in postmenopausal women

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    Background: Alcohol consumption is associated with increased high-density lipoprotein (HDL) cholesterol levels. One of the main antiatherogenic functions of HDL is reverse cholesterol transport. Three early steps of reverse cholesterol transport are (1) cellular cholesterol efflux, (2) plasma cholesterol esterification (EST), and (3) cholesteryl ester transfer (CET) to apolipoprotein B-containing lipoproteins. Our previous study in healthy middle-aged men showed that moderate alcohol consumption increases cellular cholesterol efflux and EST. This study investigated the effect of moderate alcohol consumption on three early steps of reverse cholesterol transport in postmenopausal women. Methods: In a randomized crossover study, 18 postmenopausal women-all apparently healthy, non-smoking, and moderate alcohol drinkers-consumed white wine or white grape juice with evening dinner during 2 successive periods of 3 weeks. During the white wine period, alcohol intake equaled 24 g/day. At the end of each of the two experimental periods, blood samples were collected. Results: Three weeks of alcohol consumption increased serum HDL cholesterol levels (5.0%; p < 0.05), serum HDL phospholipid levels (5.8%; p < 0.05), and the ex vivo cellular cholesterol efflux capacity of plasma, measured with Fu5AH cells (3.4%; p < 0.05). Plasma EST and CET did not change. Conclusions: Moderate alcohol intake increases serum HDL cholesterol level and stimulates cellular cholesterol efflux in postmenopausal women. Moderate alcohol consumption does not seem to affect two other early steps of reverse cholesterol transport at this level of alcohol intake. Our data suggest that the relative protection of moderate alcohol consumption against cardiovascular disease in postmenopausal women may involve the stimulation of reverse cholesterol transport through increased HDL
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