We show that Σ+ hyperons produced by 800 GeV/c protons on targets of Be and Cu have significant polarizations (15–20%). These polarizations persist at values of pt≈2 GeV/c and a wide range of xF. The polarizations from the Cu target are consistently less than from Be. The average ratio of the Σ+ polarization from Cu to that from Be is 0.68±0.08.
Measured values of the SIGMA+ polarization as functions of PT and XL for proton CU collisions.
Measured values of the SIGMA+ polarization as functions of PT and XL for proton BE collisions.
The Sigma^- mean squared charge radius has been measured in the space-like Q^2 range 0.035-0.105 GeV^2/c^2 by elastic scattering of a Sigma^- beam off atomic electrons. The measurement was performed with the SELEX (E781) spectrometer using the Fermilab hyperon beam at a mean energy of 610 GeV/c. We obtain
Total systematic errors are given.
The correlations between different moments of two flow amplitudes, extracted with the recently developed asymmetric cumulants, are measured in Pb$-$Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV recorded by the ALICE detector at the CERN Large Hadron Collider. The magnitudes of the measured observables show a dependence on the different moments as well as on the collision centrality, indicating the presence of non-linear response in all even moments up to the eighth. Furthermore, the higher-order asymmetric cumulants show different signatures than the symmetric and lower-order asymmetric cumulants. Comparisons with state-of-the-art event generators using two different parametrizations obtained from Bayesian optimization show differences between data and simulations in many of the studied observables, indicating a need for further tuning of the models behind those event generators. These results provide new and independent constraints on the initial conditions and transport properties of the system created in heavy-ion collisions.
Centrality dependence of ${\rm SC}(2,3)$ in Pb$-$Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV.
Centrality dependence of ${\rm AC}_{2,1}(2,3)$ in Pb$-$Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV.
Centrality dependence of ${\rm AC}_{1,2}(2,3)$ in Pb$-$Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV.
The event-by-event correlations between three flow amplitudes are measured for the first time in Pb--Pb collisions, using higher-order Symmetric Cumulants. We find that different three-harmonic correlations develop during the collective evolution of the medium, when compared with correlations that exist in the initial state. These new results cannot be interpreted in terms of previous lower-order flow measurements, since contributions from two-harmonic correlations are explicitly removed in the new observables. Comparison with Monte Carlo simulations provides new and independent constraints for the initial conditions and system properties of nuclear matter created in heavy-ion collisions.
Centrality dependence of ${\rm SC}(2,3,4)$ in Pb--Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$~TeV.
Centrality dependence of ${\rm SC}(2,3,5)$ in Pb--Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$~TeV.
Centrality dependence of ${\rm SC}(2,4,6)$ in Pb--Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$~TeV.
Measurements of the inclusive J/$\psi$ yield as a function of charged-particle pseudorapidity density ${\rm d}N_{\rm ch}/\rm{d}\eta$ in pp collisions at $\sqrt{s}$ = 13 TeV with ALICE at the LHC are reported. The J/$\psi$ meson yield is measured at midrapidity ($|y|<0.9$) in the dielectron channel, for events selected based on the charged-particle multiplicity at midrapidity ($|\eta|<1$) and at forward rapidity ($-3.7<\eta<-1.7$ and $2.8<\eta<5.1$); both observables are normalized to their corresponding averages in minimum bias events. The increase of the normalized J/$\psi$ yield with normalized ${\rm d}N_{\rm ch}/\rm{d}\eta$ is significantly stronger than linear and dependent on the transverse momentum. The data are compared to theoretical predictions, which describe the observed trends well, albeit not always quantitatively.
$N_{J/psi}/<N_{J/\psi}> / N_{ch}/<N_{ch}>$, $|y^{J/\psi}|<0.9$, $p_{T}^{J/\psi}$ integrated, event selection SPD
$N_{J/psi}/<N_{J/\psi}> / N_{ch}/<N_{ch}>$, $|y^{J/\psi}|<0.9$, $p_{T}^{J/\psi}$ integrated, event selection V0
$N_{J/psi}/<N_{J/\psi}> / N_{ch}/<N_{ch}>$, $|y^{J/\psi}|<0.9$, $p_{T}^{J/\psi}$ 0-4 and 4-8 GeV/c, event selection SPD
Multiplicity ($N_{\rm ch}$) distributions and transverse momentum ($p_{\rm T}$) spectra of inclusive primary charged particles in the kinematic range of $|\eta| < 0.8$ and 0.15 GeV/$c$$< p_{T} <$ 10 GeV/$c$ are reported for pp, p-Pb, Xe-Xe and Pb-Pb collisions at centre-of-mass energies per nucleon pair ranging from $\sqrt{s_{\rm NN}} = 2.76$ TeV up to $13$ TeV. A sequential two-dimensional unfolding procedure is used to extract the correlation between the transverse momentum of primary charged particles and the charged-particle multiplicity of the corresponding collision. This correlation sharply characterises important features of the final state of a collision and, therefore, can be used as a stringent test of theoretical models. The multiplicity distributions as well as the mean and standard deviation derived from the $p_{\rm T}$ spectra are compared to state-of-the-art model predictions. Providing these fundamental observables of bulk particle production consistently across a wide range of collision energies and system sizes can serve as an important input for tuning Monte Carlo event generators.
Charged-particle multiplicity distribution for pp collisions at 2.76 TeV.
Charged-particle multiplicity distribution for pp collisions at 2.76 TeV.
Koba-Nielsen-Olesen scaled charged-particle multiplicity distribution for pp collisions at 2.76 TeV.
The analyzing power,$A_{oono}$, and the polarization transfer observables$K_{onno}$,$K_{os''so}$
Position 'A' (see text for explanation).
Position 'A' (see text for explanation).
Position 'A' (see text for explanation).
$\phi$ meson measurements provide insight into strangeness production, which is one of the key observables for the hot medium formed in high-energy heavy-ion collisions. ALICE measured $\phi$ production through its decay in muon pairs in Pb-Pb collisions at $\sqrt{s_\mathrm{NN}}$ = 2.76 TeV in the intermediate transverse momentum range $2 < p_{\rm T} < 5$ GeV/$c$ and in the rapidity interval $2.5
phi yield as a function of $p_\mathrm{T}$ at forward rapidity in pp collisions.
phi yield as a function of $p_\mathrm{T}$ at forward rapidity in Pb-Pb collisions for 0-40\% centrality.
phi yield as a function of $p_\mathrm{T}$ at forward rapidity in Pb-Pb collisions for 40-90\% centrality (scaled by 3 in the figure).
We employ data taken by the JADE and OPAL experiments for an integrated QCD study in hadronic e+e- annihilations at c.m.s. energies ranging from 35 GeV through 189 GeV. The study is based on jet-multiplicity related observables. The observables are obtained to high jet resolution scales with the JADE, Durham, Cambridge and cone jet finders, and compared with the predictions of various QCD and Monte Carlo models. The strong coupling strength, alpha_s, is determined at each energy by fits of O(alpha_s^2) calculations, as well as matched O(alpha_s^2) and NLLA predictions, to the data. Matching schemes are compared, and the dependence of the results on the choice of the renormalization scale is investigated. The combination of the results using matched predictions gives alpha_s(MZ)=0.1187+{0.0034}-{0.0019}. The strong coupling is also obtained, at lower precision, from O(alpha_s^2) fits of the c.m.s. energy evolution of some of the observables. A qualitative comparison is made between the data and a recent MLLA prediction for mean jet multiplicities.
Overall result for ALPHAS at the Z0 mass from the combination of the ln R-matching results from the observables evolved using a three-loop running expression. The errors shown are total errors and contain all the statistics and systematics.
Weighted mean for ALPHAS at the Z0 mass determined from the energy evolutions of the mean values of the 2-jet cross sections obtained with the JADE and DURHAMschemes and the 3-jet fraction for the JADE, DURHAM and CAMBRIDGE schemes evaluted at a fixed YCUT.. The errors shown are total errors and contain all the statistics and systematics.
Combined results for ALPHA_S from fits of matched predicitions. The first systematic (DSYS) error is the experimental systematic, the second DSYS error isthe hadronization systematic and the third is the QCD scale error. The values of ALPHAS evolved to the Z0 mass using a three-loop evolution are also given.
Angular correlations of heavy-flavour and charged particles in high-energy proton-proton collisions are sensitive to the production mechanisms of heavy quarks and to their fragmentation as well as hadronisation processes. The measurement of the azimuthal-correlation function of prompt D mesons with charged particles in proton-proton collisions at a centre-of-mass energy of $\sqrt{s} = 13$ TeV with the ALICE detector is reported, considering D$^{0}$, D$^{+}$, and D$^{*+}$ mesons in the transverse-momentum interval $3 < p_{\rm T} < 36$ GeV/$c$ at midrapidity ($|y| < 0.5$), and charged particles with $p_{\rm T} > 0.3$ GeV/$c$ and pseudorapidity $|\eta| < 0.8$. This measurement has an improved precision and provides an extended transverse-momentum coverage compared to previous ALICE measurements at lower energies. The study is also performed as a function of the charged-particle multiplicity, showing no modifications of the correlation function with multiplicity within uncertainties. The properties and the transverse-momentum evolution of the near- and away-side correlation peaks are studied and compared with predictions from various Monte Carlo event generators. Among those considered, PYTHIA8 and POWHEG+PYTHIA8 provide the best description of the measured observables. The obtained results can provide guidance on tuning the generators.
Comparison of the azimuthal-correlation distributions of D mesons (average of D$^{0}$, D$^{+}$, and D$^{*+}$) with $3 < p_{\rm T} < 5$ GeV/$c$ and charged particles with $0.3 < p_{\rm T} < 1$ GeV/$c$, in pp collisions at $\sqrt{s} = $5, 7, and 13 TeV, after baseline subtraction. Rapidity range for the D mesons is $|y^{\rm D}_{\rm cms}| < 0.5$. Correlations are integrated for $|\Delta\eta|=|\eta_{\rm ch}-\eta_{\rm D}| < 1$. The azimuthal-correlation distributions are reported in the range $0 < \Delta\varphi < \pi$.
Comparison of the azimuthal-correlation distributions of D mesons (average of D$^{0}$, D$^{+}$, and D$^{*+}$) with $8 < p_{\rm T} < 16$ GeV/$c$ and charged particles with $0.3 < p_{\rm T} < 1$ GeV/$c$, in pp collisions at $\sqrt{s} = $5, 7, and 13 TeV, after baseline subtraction. Rapidity range for the D mesons is $|y^{\rm D}_{\rm cms}| < 0.5$. Correlations are integrated for $|\Delta\eta|=|\eta_{\rm ch}-\eta_{\rm D}| < 1$. The azimuthal-correlation distributions are reported in the range $0 < \Delta\varphi < \pi$.
Comparison of the azimuthal-correlation distributions of D mesons (average of D$^{0}$, D$^{+}$, and D$^{*+}$) with $16 < p_{\rm T} < 24$ GeV/$c$ and charged particles with $0.3 < p_{\rm T} < 1$ GeV/$c$, in pp collisions at $\sqrt{s} = $5, 7, and 13 TeV, after baseline subtraction. Rapidity range for the D mesons is $|y^{\rm D}_{\rm cms}| < 0.5$. Correlations are integrated for $|\Delta\eta|=|\eta_{\rm ch}-\eta_{\rm D}| < 1$. The azimuthal-correlation distributions are reported in the range $0 < \Delta\varphi < \pi$.
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