The first study of $\phi$-meson production in p–Pb collisions at forward and backward rapidity, at a nucleon–nucleon centre-of-mass energy s NN =5.02 TeV, has been performed with the ALICE apparatus ...at the LHC. The $\phi$-mesons have been identified in the dimuon decay channel in the transverse momentum (p T ) range 1 < p T < 7 GeV/c, both in the p-going (2.03 < y < 3.53) and the Pb-going (-4.46 < y < -2.96) directions — where y stands for the rapidity in the nucleon–nucleon centre-of-mass — the integrated luminosity amounting to 5.01±0.19 nb-1 and 5.81±0.20 nb-1 , respectively, for the two data samples. Differential cross sections as a function of transverse momentum and rapidity are presented. The forward–backward ratio for $\phi$-meson production is measured for 2.96 < |y| < 3.53, resulting in a ratio ~0.5 with no significant p T dependence within the uncertainties. The p T dependence of the $\phi$ nuclear modification factor R pPb exhibits an enhancement up to a factor 1.6 at p T =3–4 GeV/c in the Pb-going direction. The p T dependence of the $\phi$-meson cross section in pp collisions at s=2.76 TeV, which is used to determine a reference for the p–Pb results, is also presented here for 1 < p T < 5 GeV/c and 2.5 < y < 4, for a 78±3 nb-1 integrated luminosity sample.
Two-particle angular correlations were measured in pp collisions at $\sqrt{s} = 7$ TeV. The analysis was carried out 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.
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<pT< 8 GeV/c in minimum-bias p-Pb ...collisions at √sNN = 5.02 TeV and in 1.3 < pT< 8 GeV/c in the 20% most central Pb-Pb collisions at √sNN = 2.76 TeV. The pp reference spectra at √sNN = 5.02 TeV and √s = 2.76 TeV, needed for the calculation of the nuclear modification factors RpPb and RPbPb, were obtained by a pQCD-driven scaling of the cross section of electrons from beauty-hadron decays measured at √s = 7 TeV. In the pT interval 3 < pT < 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 pT, the RPbPb values increase with large systematic uncertainties. The RpPb 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 RpPb 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 RPbPb below unity at high pT may be ascribed to an effect of the hot and dense medium formed in Pb-Pb collisions.
The transverse momentum ( $p_\mathrm{T} $ ) spectra and elliptic flow coefficient ( $v_{2}$ ) of deuterons and anti-deuterons at mid-rapidity ( $|y|<0.5$ ) are measured with the ALICE detector at the ...LHC in Pb–Pb collisions at $\sqrt{s_{\mathrm {NN}}}$ = 2.76 TeV. The measurement of the $p_\mathrm{T} $ spectra of (anti-)deuterons is done up to 8 GeV $/c$ in 0–10% centrality class and up to 6 GeV $/c$ in 10–20% and 20–40% centrality classes. The $v_{2}$ is measured in the 0.8 < $p_\mathrm{T} $ $<~$ 5 GeV $/c$ interval and in six different centrality intervals (0–5, 5–10, 10–20, 20–30, 30–40 and 40–50%) using the scalar product technique. Measured $\pi^{\pm }$ , K$^{\pm }$ and p+ $\overline{\mathrm {p}}$ transverse-momentum spectra and $v_{2}$ are used to predict the deuteron $p_\mathrm{T} $ spectra and $v_{2}$ within the Blast-Wave model. The predictions are able to reproduce the $v_{2}$ coefficient in the measured $p_\mathrm{T} $ range and the transverse-momentum spectra for $p_\mathrm{T} $ > 1.8 GeV $/c$ within the experimental uncertainties. The measurement of the coalescence parameter $B_2$ is performed, showing a $p_\mathrm{T} $ dependence in contrast with the simplest coalescence model, which fails to reproduce also the measured $v_{2}$ coefficient. In addition, the coalescence parameter $B_2$ and the elliptic flow coefficient in the 20–40% centrality interval are compared with the AMPT model which is able, in its version without string melting, to reproduce the measured $v_{2}$ ( $p_\mathrm{T} $ ) and the $B_2$ ( $p_\mathrm{T} $ ) trend.
Abstract Two-particle angular correlations were measured in pp collisions at $$\sqrt{s} = 7$$ 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.
Abstract The production cross sections for prompt charmed mesons $$\mathrm{D^0}$$ D 0 , $$\mathrm{D^+}$$ D + , $$\mathrm{D^{*+}}$$ D ∗ + and $$\mathrm{D_s^+}$$ D s + were measured at mid-rapidity in ...proton–proton collisions at a centre-of-mass energy $$\sqrt{s}=7~{\mathrm {TeV}}$$ s = 7 TeV with the ALICE detector at the Large Hadron Collider (LHC). D mesons were reconstructed from their decays $$\mathrm{D}^0 \rightarrow \mathrm{K}^-\pi ^+$$ D 0 → K - π + , $$\mathrm{D}^+\rightarrow \mathrm{K}^-\pi ^+\pi ^+$$ D + → K - π + π + , $$\mathrm{D}^{*+} \rightarrow \mathrm{D}^0 \pi ^+$$ D ∗ + → D 0 π + , $$\mathrm{D_s^{+}\rightarrow \phi \pi ^+\rightarrow K^-K^+\pi ^+}$$ D s + → ϕ π + → K - K + π + , and their charge conjugates.With respect to previous measurements in the same rapidity region, the coverage in transverse momentum ( $$p_\mathrm{T}$$ p T ) is extended and the uncertainties are reduced by a factor of about two. The accuracy on the estimated total $$\mathrm{c}{\overline{\mathrm{c}}}$$ c c ¯ production cross section is likewise improved. The measured $$p_\mathrm{T}$$ p T -differential cross sections are compared with the results of three perturbative QCD calculations.
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