Transverse momentum ($p_{\rm{T}}$) spectra of pions, kaons, and protons up to $p_{\rm{T}} = 20$ GeV/$c$ have been measured in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV using the ALICE detector for six different centrality classes covering 0-80%. The proton-to-pion and the kaon-to-pion ratios both show a distinct peak at $p_{\rm{T}} \approx 3$ GeV/$c$ in central Pb-Pb collisions that decreases towards more peripheral collisions. For $p_{\rm{T}} > 10$ GeV/$c$, the nuclear modification factor is found to be the same for all three particle species in each centrality interval within systematic uncertainties of 10-20%. This suggests there is no direct interplay between the energy loss in the medium and the particle species composition in the hard core of the quenched jet. For $p_{\rm{T}} < 10$ GeV/$c$, the data provide important constraints for models aimed at describing the transition from soft to hard physics.
Invariant yields of identified pions in Pb-Pb collisions.
Invariant yields of identified kaons in Pb-Pb collisions.
Invariant yields of identified protons in Pb-Pb collisions.
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The cross section of the quasi-elastic reactions\(\bar v_\mup \to \mu ^ +\Lambda (\Sigma ^0 )\) in the energy range 5–100 GeV is determined from Fermilab 15′ bubble chamber antineutrino data. TheQ2 analysis of quasi-elastic Λ events yieldsMA=1.0±0.3 GeV/c2 for the axial mass value. With zero µΛK0 events observed, the 90% confidence level upper limit\(\sigma (\bar v_\mup \to \mu ^ +\Lambda {\rm K}^0 )< 2.0 \cdot 10^{ - 40} cm^2 \) is obtained. At the same time, we found that the cross section of reaction\(\bar v_\mup \to \mu ^ +\Lambda {\rm K}^0+ m\pi ^0 \) is equal to\(\left( {3.9\begin{array}{*{20}c}{ + 1.6}\\{ - 1.3}\\ \end{array} } \right) \cdot 10^{ - 40} cm^2 \).
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Results from a partial wave analysis of theKππ system produced in the hypercharge exchange reaction π−p→(K+π−π0)Λ at 3.95 GeV/c are presented. SignificantQ1 production is observed but no evidence is found forQ2 production thus confirming the results obtained in a previous decay Dalitz plot analysis of the same reaction. The relative phase behaviour of the 1+(Kϱ) partial waves obtained with the present analysis provides additional confirmation of the resonance interpretation of theQ1 enhancement. Information is also obtained about its production properties and the role played by the Λ polarization in the hypercharge exchange reaction. This is compared with the results obtained in the reactionK−p→(π+π−π0)Λ at 4 GeV/c.
LAMBDA POLARIZATION CALCULATED AS AVERAGE POLARIZATION OF ALL 1 + (K RHO0) PARTIAL WAVES IN THE QLOW(1240) REGION.
SPIN PARITY CONTENT OF (K PI PI) SYSTEM.
CONTRIBUTION TO THE TOTAL JP=1+ INTENSITY FROM THE K* AND RHO ISOBARS.
Q-meson production is studied in the hypercharge exchange reaction π-p → (Kππ)Λ at 3.95 GeV/c by selecting events witht(π- →Kππ)>1.2GeV2. An enhancement with a mass of 1294±10 MeV and a width of 66±15 MeV is observed in the (Kππ) mass distribution. A spin-parity analysis of the (Kππ) decay Dalitz plot shows the enhancement to be in theJP=1+S(Kϱ) wave and is therefore attributed toQ1-meson production. No evidence is found for the decayQ1→K0ω but limited statistics allow only placing an upper limit of 30% for the decay ratioKω/Kϱ0. TheQ1 production cross section fort(π- →Kππ)>1.2GeV2 is 8±1.3 μb. No evidence is found for the process π-p→Q2Λ withQ2→K*π for which the partial wave analysis gives an upper cross section limit of 2.5 μb at the 95% confidence level.
PRODUCTION OF Q1 OF MASS 1294 +- 10 MEV, WIDTH 66 +- 15 MEV. IN BACKWARD HEMISPHERE, CROSS SECTION IS <0.5 MUB (CL = 95 PCT).
UPPER LIMIT FOR PRODUCTION OF Q2 OF MASS AROUND 1400 MEV.
We present results on inclusive particle production in the antineutrino charged current induced hadron jets observed in the Fermilab 15 ft bubble chamber. Fractional energy distributions, particle ratios and average multiplicities of the hadrons in the jets are measured. Ratios between the inclusive production rates of different mesons in the jets are studied to seek evidence for the d-quark origin of the observed hadrons. Good over-all agreement with the hypothesis of d-quark fragmentation with universal fragmentation functions obeying isospin systematics is established.
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p p annihilations, leading to the production of at least one neutral K meson in the final state, have been studied in the incident momentum region of 700–760 MeV/ c . Topological cross sections and cross sections for the various exclusive final states are presented. Detailed analyses of the different final states have been carried out to study the importance of resonance production and of quasi two-body and quasi three-body processes. A detailed study of the K K π system in the four-body final states shows that the F 1 meson is a spurious effect due to systematic biases. In the momentum range investigated, the C = +1 final states are strongly suppressed.
SUMMARY OF QUASI-TWO-BODY CROSS SECTIONS.
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The results of a study of strange particle production in charged current $\bar{\nu}_{\mu} N$ interactions in the Fermilab 15 ft bubble chamber filled with a heavy $Ne-H_2$ mixture are presented. Production rates and average multiplicities of $K^0$'s and Λ's as functions of W 2 and Q 2 are given. The experimental data agree well with the quark-parton model predictions if a yield of 0.06 ± 0.02 of $K^0$'s and Λ's from charm production is included. Upper limits for D-meson production are given and the shape of the charmed quark fragmentation function is discussed. Inclusive production of the K ∗ (890) and Σ(1385) resonances is measured and it is shown that only about 5% of the K 0 mesons and Λ hyperons results from resonance decays. Relative production rates of neutral strange particles on proton and neutron targets are studied.
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