Abstract The production of the $$\Lambda $$ Λ (1520) baryonic resonance has been measured at midrapidity in inelastic pp collisions at $$\sqrt{s} = 7\ \hbox {TeV}$$ s=7TeV and in p–Pb collisions at ...$$\sqrt{s_{\mathrm{NN}}} = 5.02\ \hbox {TeV}$$ sNN=5.02TeV for non-single diffractive events and in multiplicity classes. The resonance is reconstructed through its hadronic decay channel $$\Lambda $$ Λ (1520) $$\rightarrow \hbox {pK}^{-}$$ →pK- and the charge conjugate with the ALICE detector. The integrated yields and mean transverse momenta are calculated from the measured transverse momentum distributions in pp and p–Pb collisions. The mean transverse momenta follow mass ordering as previously observed for other hyperons in the same collision systems. A Blast-Wave function constrained by other light hadrons ($$\pi $$ π , K, $$\hbox {K}_{\mathrm{S}}^0$$ KS0 , p, $$\Lambda $$ Λ ) describes the shape of the $$\Lambda $$ Λ (1520) transverse momentum distribution up to $$3.5\ \hbox {GeV}/c$$ 3.5GeV/c in p–Pb collisions. In the framework of this model, this observation suggests that the $$\Lambda $$ Λ (1520) resonance participates in the same collective radial flow as other light hadrons. The ratio of the yield of $$\Lambda (1520)$$ Λ(1520) to the yield of the ground state particle $$\Lambda $$ Λ remains constant as a function of charged-particle multiplicity, suggesting that there is no net effect of the hadronic phase in p–Pb collisions on the $$\Lambda $$ Λ (1520) yield.
This document corrects two errors in Eur. Phys. J. C77 (2017) no. 8, 56: the incorrect referencing of Fig. 1 labels in three paragraphs in the results section and a missing acknowledgements section.
Abstract The production cross section of inclusive isolated photons has been measured by the ALICE experiment at the CERN LHC in pp collisions at a centre-of-momentum energy of $$\sqrt{s}=$$ s= ... 7 TeV. The measurement is performed with the electromagnetic calorimeter EMCal and the central tracking detectors, covering a range of $$|\eta |<0.27$$ |η|<0.27 in pseudorapidity and a transverse momentum range of $$ 10< p_\mathrm {T}^{\gamma }< 60~\mathrm {GeV}/c$$ 10<pTγ<60GeV/c . The result extends the $$p_\mathrm {T}$$ pT coverage of previously published results of the ATLAS and CMS experiments at the same collision energy to smaller $$p_\mathrm {T}$$ pT . The measurement is compared to next-to-leading order perturbative QCD calculations and to the results from the ATLAS and CMS experiments. All measurements and theory predictions are in agreement with each other.
Abstract We present a study of the inclusive charged-particle transverse momentum ($$p_{\mathrm{T}}$$ pT ) spectra as a function of charged-particle multiplicity density at mid-pseudorapidity, ...$$\mathrm{d}N_{\mathrm{ch}}/\mathrm{d}\eta $$ dNch/dη , in pp collisions at $$\sqrt{s}=5.02$$ s=5.02 and 13 TeV covering the kinematic range $$|\eta |<0.8$$ |η|<0.8 and $$0.15<p_{\mathrm{T}} <20$$ 0.15<pT<20 GeV/c. The results are presented for events with at least one charged particle in $$|\eta |<1$$ |η|<1 (INEL$$\,>0$$ >0 ). The $$p_\mathrm{T}$$ pT spectra are reported for two multiplicity estimators covering different pseudorapidity regions. The $$p_{\mathrm{T}}$$ pT spectra normalized to that for INEL$$\,>0$$ >0 show little energy dependence. Moreover, the high-$$p_{\mathrm{T}}$$ pT yields of charged particles increase faster than the charged-particle multiplicity density. The average $${ p}_{\mathrm{T}}$$ pT as a function of multiplicity and transverse spherocity is reported for pp collisions at $$\sqrt{s}=13$$ s=13 TeV. For low- (high-) spherocity events, corresponding to jet-like (isotropic) events, the average $$p_\mathrm{T}$$ pT is higher (smaller) than that measured in INEL$$\,>0$$ >0 pp collisions. Within uncertainties, the functional form of $$\langle p_{\mathrm{T}} \rangle (N_{\mathrm{ch}})$$ ⟨pT⟩(Nch) is not affected by the spherocity selection. While EPOS LHC gives a good description of many features of data, PYTHIA overestimates the average $$p_{\mathrm{T}}$$ pT in jet-like events.
Abstract The ALICE Collaboration has measured the energy dependence of exclusive photoproduction of $$\mathrm {J}/\psi $$ J/ψ vector mesons off proton targets in ultra–peripheral p–Pb collisions at a ...centre-of-mass energy per nucleon pair $$\sqrt{s_\mathrm{NN}} = 5.02$$ sNN=5.02 TeV. The e$$^+$$ + e$$^-$$ - and $$\mu ^+\mu ^-$$ μ+μ- decay channels are used to measure the cross section as a function of the rapidity of the $$\mathrm {J}/\psi $$ J/ψ in the range $$-2.5< y < 2.7$$ -2.5<y<2.7 , corresponding to an energy in the $$\gamma $$ γ p centre-of-mass in the interval $$40< W_{\gamma \mathrm {p}}<550$$ 40<Wγp<550 GeV. The measurements, which are consistent with a power law dependence of the exclusive $$\mathrm {J}/\psi $$ J/ψ photoproduction cross section, are compared to previous results from HERA and the LHC and to several theoretical models. They are found to be compatible with previous measurements.
Abstract The measurements of the production of prompt $${{\mathrm{D}}^0}$$ D0 , $${{\mathrm{D}}^+}$$ D+ , $${{\mathrm{D}}^{*+}}$$ D∗+ , and $${{\mathrm{D}}^+_{\mathrm{s}}}$$ Ds+ mesons in ...proton–proton (pp) collisions at $$\sqrt{s}=5.02~\mathrm {TeV}$$ s=5.02TeV with the ALICE detector at the Large Hadron Collider (LHC) are reported. D mesons were reconstructed at mid-rapidity ($$|y|<0.5$$ |y|<0.5 ) via their hadronic decay channels $$\mathrm{D}^0 \rightarrow {\mathrm{K}}^-\pi ^+$$ D0→K-π+ , $$\mathrm{D}^+\rightarrow {\mathrm{K}}^-\pi ^+\pi ^+$$ D+→K-π+π+ , $${\mathrm{D}}^{*+} \rightarrow {\mathrm{D}}^0 \pi ^+ \rightarrow {\mathrm{K}}^- \pi ^+ \pi ^+$$ D∗+→D0π+→K-π+π+ , $${{\mathrm{D}}^{+}_{\mathrm{s}}\rightarrow \phi \pi ^+\rightarrow {\mathrm{K}}^{+} {\mathrm{K}}^{-} \pi ^{+}}$$ Ds+→ϕπ+→K+K-π+ , and their charge conjugates. The production cross sections were measured in the transverse momentum interval $$0<p_{\mathrm{T}}<36~\mathrm {GeV}/c$$ 0<pT<36GeV/c for $${{\mathrm{D}}^0}$$ D0 , $$1<p_{\mathrm{T}}<36~\mathrm {GeV}/c$$ 1<pT<36GeV/c for $${{\mathrm{D}}^+}$$ D+ and $${{\mathrm{D}}^{*+}}$$ D∗+ , and in $$2<p_{\mathrm{T}}<24~\mathrm {GeV}/c$$ 2<pT<24GeV/c for $${{\mathrm{D}}^+_{\mathrm{s}}}$$ Ds+ mesons. Thanks to the higher integrated luminosity, an analysis in finer $$p_{\mathrm{T}}$$ pT bins with respect to the previous measurements at $$\sqrt{s}=7~\mathrm {TeV}$$ s=7TeV was performed, allowing for a more detailed description of the cross-section $$p_{\mathrm{T}}$$ pT shape. The measured $$p_{\mathrm{T}}$$ pT -differential production cross sections are compared to the results at $$\sqrt{s}=7$$ s=7 TeV and to four different perturbative QCD calculations. Its rapidity dependence is also tested combining the ALICE and LHCb measurements in pp collisions at $$\sqrt{s}=5.02~\mathrm {TeV}$$ s=5.02TeV . This measurement will allow for a more accurate determination of the nuclear modification factor in p–Pb and Pb–Pb collisions performed at the same nucleon–nucleon centre-of-mass energy.
Abstract The pseudorapidity density of charged particles, $$\mathrm {d}N_{\mathrm{ch}}/\mathrm {d}\eta $$ dNch/dη , in p–Pb collisions has been measured at a centre-of-mass energy per nucleon–nucleon ...pair of $$\sqrt{s_{\scriptscriptstyle {\mathrm{NN}}}$$ sNN = 8.16 TeV at mid-pseudorapidity for non-single-diffractive events. The results cover 3.6 units of pseudorapidity, $$|\eta |<1.8$$ |η|<1.8 . The $$\mathrm {d}N_{\mathrm{ch}}/\mathrm {d}\eta $$ dNch/dη value is $$19.1\pm 0.7$$ 19.1±0.7 at $$|\eta |<0.5$$ |η|<0.5 . This quantity divided by $$\langle N_{\mathrm{part}} \rangle $$ ⟨Npart⟩ / 2 is $$4.73\pm 0.20$$ 4.73±0.20 , where $$\langle N_{\mathrm{part}} \rangle $$ ⟨Npart⟩ is the average number of participating nucleons, is 9.5% higher than the corresponding value for p–Pb collisions at $$\sqrt{s_{\scriptscriptstyle {\mathrm{NN}}}$$ sNN = 5.02 TeV. Measurements are compared with models based on different mechanisms for particle production. All models agree within uncertainties with data in the Pb-going side, while HIJING overestimates, showing a symmetric behaviour, and EPOS underestimates the p-going side of the $$\mathrm {d}N_{\mathrm{ch}}/\mathrm {d}\eta $$ dNch/dη distribution. Saturation-based models reproduce the distributions well for $$\eta >-1.3$$ η>-1.3 . The $$\mathrm {d}N_{\mathrm{ch}}/\mathrm {d}\eta $$ dNch/dη is also measured for different centrality estimators, based both on the charged-particle multiplicity and on the energy deposited in the Zero-Degree Calorimeters. A study of the implications of the large multiplicity fluctuations due to the small number of participants for systems like p–Pb in the centrality calculation for multiplicity-based estimators is discussed, demonstrating the advantages of determining the centrality with energy deposited near beam rapidity.
Abstract First results on $$\hbox {K}/\pi $$ K/π , $$\hbox {p}/\pi $$ p/π and K/p fluctuations are obtained with the ALICE detector at the CERN LHC as a function of centrality in $$\text{ Pb--Pb }$$ ...Pb--Pb collisions at $$\sqrt{s_\mathrm{{NN}}} =2.76\hbox { TeV}$$ sNN=2.76TeV . The observable $$\nu _{\mathrm{dyn}}$$ νdyn , which is defined in terms of the moments of particle multiplicity distributions, is used to quantify the magnitude of dynamical fluctuations of relative particle yields and also provides insight into the correlation between particle pairs. This study is based on a novel experimental technique, called the Identity Method, which allows one to measure the moments of multiplicity distributions in case of incomplete particle identification. The results for $$\hbox {p}/\pi $$ p/π show a change of sign in $$\nu _{\mathrm{dyn}}$$ νdyn from positive to negative towards more peripheral collisions. For central collisions, the results follow the smooth trend of the data at lower energies and $$\nu _{\mathrm{dyn}}$$ νdyn exhibits a change in sign for $$\hbox {p}/\pi $$ p/π and K/p.
Abstract Measurements of inclusive charged-particle jet production in pp and p-Pb collisions at center-of-mass energy per nucleon-nucleon collision s NN $$ \sqrt{s_{\textrm{NN}}} $$ = 5.02 TeV and ...the corresponding nuclear modification factor R pPb ch jet $$ {R}_{\textrm{pPb}}^{\textrm{ch}\ \textrm{jet}} $$ are presented, using data collected with the ALICE detector at the LHC. Jets are reconstructed in the central rapidity region |η jet| < 0.5 from charged particles using the anti-k T algorithm with resolution parameters R = 0.2, 0.3, and 0.4. The p T-differential inclusive production cross section of charged-particle jets, as well as the corresponding cross section ratios, are reported for pp and p-Pb collisions in the transverse momentum range 10 < p T , jet ch $$ {p}_{\textrm{T},\textrm{jet}}^{\textrm{ch}} $$ < 140 GeV/c and 10 < p T , jet ch $$ {p}_{\textrm{T},\textrm{jet}}^{\textrm{ch}} $$ < 160 GeV/c, respectively, together with the nuclear modification factor R pPb ch jet $$ {R}_{\textrm{pPb}}^{\textrm{ch}\ \textrm{jet}} $$ in the range 10 < p T , jet ch $$ {p}_{\textrm{T},\textrm{jet}}^{\textrm{ch}} $$ < 140 GeV/c. The analysis extends the p T range of the previously-reported charged-particle jet measurements by the ALICE Collaboration. The nuclear modification factor is found to be consistent with one and independent of the jet resolution parameter with the improved precision of this study, indicating that the possible influence of cold nuclear matter effects on the production cross section of charged-particle jets in p-Pb collisions at s NN $$ \sqrt{s_{\textrm{NN}}} $$ = 5.02 TeV is smaller than the current precision. The obtained results are in agreement with other minimum bias jet measurements available for RHIC and LHC energies, and are well reproduced by the NLO perturbative QCD Powheg calculations with parton shower provided by Pythia8 as well as by Jetscape simulations.
Abstract Results on the transverse spherocity dependence of light-flavor particle production (π, K, p, ϕ, K*0, K S 0 $$ {\textrm{K}}_{\textrm{S}}^0 $$ , Λ, Ξ) at midrapidity in high-multiplicity pp ...collisions at s $$ \sqrt{s} $$ = 13 TeV were obtained with the ALICE apparatus. The transverse spherocity estimator S O p T = 1 $$ \left({S}_{\textrm{O}}^{p_{\textrm{T}}=1}\right) $$ categorizes events by their azimuthal topology. Utilizing narrow selections on S O p T = 1 $$ {S}_{\textrm{O}}^{p_{\textrm{T}}=1} $$ , it is possible to contrast particle production in collisions dominated by many soft initial interactions with that observed in collisions dominated by one or more hard scatterings. Results are reported for two multiplicity estimators covering different pseudorapidity regions. The S O p T = 1 $$ {S}_{\textrm{O}}^{p_{\textrm{T}}=1} $$ estimator is found to effectively constrain the hardness of the events when the midrapidity (|η| < 0.8) estimator is used. The production rates of strange particles are found to be slightly higher for soft isotropic topologies, and severely suppressed in hard jet-like topologies. These effects are more pronounced for hadrons with larger mass and strangeness content, and observed when the topological selection is done within a narrow multiplicity interval. This demonstrates that an important aspect of the universal scaling of strangeness enhancement with final-state multiplicity is that high-multiplicity collisions are dominated by soft, isotropic processes. On the contrary, strangeness production in events with jet-like processes is significantly reduced. The results presented in this article are compared with several QCD-inspired Monte Carlo event generators. Models that incorporate a two-component phenomenology, either through mechanisms accounting for string density, or thermal production, are able to describe the observed strangeness enhancement as a function of S O p T = 1 $$ {S}_{\textrm{O}}^{p_{\textrm{T}}=1} $$ .
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