Abstract The measurement of the azimuthal-correlation function of prompt D mesons with charged particles in pp collisions at $$\sqrt{s} =5.02\ \hbox {TeV}$$ s = 5.02 TeV and p–Pb collisions at ...$$\sqrt{s_{\mathrm{NN}}} = 5.02\ \hbox {TeV}$$ s NN = 5.02 TeV with the ALICE detector at the LHC is reported. The $$\mathrm{D}^{0}$$ D 0 , $$\mathrm{D}^{+} $$ D + , and $$\mathrm{D}^{*+} $$ D ∗ + mesons, together with their charge conjugates, were reconstructed at midrapidity in the transverse momentum interval $$3< p_\mathrm{T} < 24\ \hbox {GeV}/c$$ 3 < p T < 24 GeV / c and correlated with charged particles having $$p_\mathrm{T} > 0.3\ \hbox {GeV}/c$$ p T > 0.3 GeV / c and pseudorapidity $$|\eta | < 0.8$$ | η | < 0.8 . The properties of the correlation peaks appearing in the near- and away-side regions (for $$\Delta \varphi \approx 0$$ Δ φ ≈ 0 and $$\Delta \varphi \approx \pi $$ Δ φ ≈ π , respectively) were extracted via a fit to the azimuthal correlation functions. The shape of the correlation functions and the near- and away-side peak features are found to be consistent in pp and p–Pb collisions, showing no modifications due to nuclear effects within uncertainties. The results are compared with predictions from Monte Carlo simulations performed with the PYTHIA, POWHEG+PYTHIA, HERWIG, and EPOS 3 event generators.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract The study of (anti-)deuteron production in pp collisions has proven to be a powerful tool to investigate the formation mechanism of loosely bound states in high-energy hadronic collisions. ...In this paper the production of $$\text {(anti-)deuterons}$$ (anti-)deuterons is studied as a function of the charged particle multiplicity in inelastic pp collisions at $$\sqrt{s}=13$$ s = 13 TeV using the ALICE experiment. Thanks to the large number of accumulated minimum bias events, it has been possible to measure (anti-)deuteron production in pp collisions up to the same charged particle multiplicity ( $${\mathrm {d} N_{ch}/\mathrm {d} \eta } \sim 26$$ d N ch / d η ∼ 26 ) as measured in p–Pb collisions at similar centre-of-mass energies. Within the uncertainties, the deuteron yield in pp collisions resembles the one in p–Pb interactions, suggesting a common formation mechanism behind the production of light nuclei in hadronic interactions. In this context the measurements are compared with the expectations of coalescence and statistical hadronisation models (SHM).
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract This paper presents the measurements of $$\pi ^{\pm }$$ π± , $$\mathrm {K}^{\pm }$$ K± , $$\text {p}$$ p and $$\overline{\mathrm{p}} $$ p¯ transverse momentum ($$p_{\text {T}}$$ pT ) spectra ...as a function of charged-particle multiplicity density in proton–proton (pp) collisions at $$\sqrt{s}\ =\ 13\ \text {TeV}$$ s=13TeV with the ALICE detector at the LHC. Such study allows us to isolate the center-of-mass energy dependence of light-flavour particle production. The measurements reported here cover a $$p_{\text {T}}$$ pT range from 0.1 to 20 $$\text {GeV}/c$$ GeV/c and are done in the rapidity interval $$|y|<0.5$$ |y|<0.5 . The $$p_{\text {T}}$$ pT -differential particle ratios exhibit an evolution with multiplicity, similar to that observed in pp collisions at $$\sqrt{s}\ =\ 7\ \text {TeV}$$ s=7TeV , which is qualitatively described by some of the hydrodynamical and pQCD-inspired models discussed in this paper. Furthermore, the $$p_{\text {T}}$$ pT -integrated hadron-to-pion yield ratios measured in pp collisions at two different center-of-mass energies are consistent when compared at similar multiplicities. This also extends to strange and multi-strange hadrons, suggesting that, at LHC energies, particle hadrochemistry scales with particle multiplicity the same way under different collision energies and colliding systems.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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 The production yields of the Σ(1385) ± and Ξ(1530)0 resonances are measured in pp collisions at s $$ \sqrt{s} $$ = 13 TeV with ALICE. The measurements are performed as a function of the ...charged-particle multiplicity ⟨dN ch /dη⟩, which is related to the energy density produced in the collision. The results include transverse momentum (p T) distributions, p T-integrated yields, mean transverse momenta of Σ(1385) ± and Ξ(1530)0, as well as ratios of the p T-integrated resonance yields relative to yields of other hadron species. The Σ(1385) ± /π ± and Ξ(1530)0 /π ± yield ratios are consistent with the trend of the enhancement of strangeness production from low to high multiplicity pp collisions, which was previously observed for strange and multi-strange baryons. The yield ratio between the measured resonances and the long-lived baryons with the same strangeness content exhibits a hint of a mild increasing trend at low multiplicity, despite too large uncertainties to exclude the flat behaviour. The results are compared with predictions from models such as EPOS-LHC and PYTHIA 8 with Rope shoving. The latter provides the best description of the multiplicity dependence of the Σ(1385) ± and Ξ(1530)0 production in pp collisions at s $$ \sqrt{s} $$ = 13 TeV.
Abstract The ALICE Collaboration reports a search for jet quenching effects in high-multiplicity (HM) proton-proton collisions at s $$ \sqrt{s} $$ = 13 TeV, using the semi-inclusive ...azimuthal-difference distribution ∆φ of charged-particle jets recoiling from a high transverse momentum (high-p T,trig) trigger hadron. Jet quenching may broaden the ∆φ distribution measured in HM events compared to that in minimum bias (MB) events. The measurement employs a p T,trig-differential observable for data-driven suppression of the contribution of multiple partonic interactions, which is the dominant background. While azimuthal broadening is indeed observed in HM compared to MB events, similar broadening for HM events is observed for simulations based on the PYTHIA 8 Monte Carlo generator, which does not incorporate jet quenching. Detailed analysis of these data and simulations show that the azimuthal broadening is due to bias of the HM selection towards events with multiple jets in the final state. The identification of this bias has implications for all jet quenching searches where selection is made on the event activity.
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