The ratios of yields of anti-baryons to baryons probes the mechanisms of baryon-number transport. Results for $\bar{\rm p}/{\rm p}$, $\bar{\rm \Lambda}/{\rm \Lambda}$, $\rm\bar{\Xi}$$^{+}/{\rm \Xi}^{-}$ and $\rm\bar{\Omega}$$^{+}/{\rm \Omega}^{-}$ in pp collisions at $\sqrt{s} = 0.9$, 2.76 and 7 TeV, measured with the ALICE detector at the LHC, are reported. Within the experimental uncertainties and ranges covered by our measurement, these ratios are independent of rapidity, transverse momentum and multiplicity for all measured energies. The results are compared to expectations from event generators, such as PYTHIA and HIJING-B, that are used to model the particle production in pp collisions. The energy dependence of $\bar{\rm p}/{\rm p}$, $\bar{\rm \Lambda}/{\rm \Lambda}$, $\rm\bar{\Xi}$$^{+}/{\rm \Xi^{-}}$ and $\rm\bar{\Omega}$$^{+}/{\rm \Omega^{-}}$, reaching values compatible with unity for $\sqrt{s} = 7$ TeV, complement the earlier $\bar{\rm p}/{\rm p}$ measurement of ALICE. These dependencies can be described by exchanges with the Regge-trajectory intercept of $\alpha_{\rm {J}} \approx 0.5$, which are suppressed with increasing rapidity interval ${\rm \Delta} y$. Any significant contribution of an exchange not suppressed at large ${\rm \Delta} y$ (reached at LHC energies) is disfavoured.
The pbar/p ratio at sqrt(s) = 2.76 TeV as a function of pT.
The pbar/p ratio at sqrt(s) = 2.76 TeV as a function of rapidity.
The LambdaBar/Lambda ratio at sqrt(s) = 0.9 TeV as a function of pT.
Mid-rapidity spectra and yields of K$^-$ and K$^+$ have been measured for Au+Au collisions at 4, 6, 8, and 10.7 AGeV. The K$^-$ yield increases faster with beam energy than for K$^+$ and hence the K$^-$/K$^+$ ratio increases with beam energy. This ratio is studied as a function of both $\sqrt{s}$ and $\sqrt{s}$-$\sqrt{s_{th}}$ which allows the direct comparison of the kaon yields with respect to the production threshold in p+p reactions. For equal $\sqrt{s}$ - $\sqrt{s_{th}}$ the measured ratio K$^-$/K$^+$=0.2 at energies above threshold in contrast to the K$^-$/K$^+$ ratio of near unity observed at energies below threshold. The use of the K$^-$/K$^+$ ratio to test the predicted changes of kaon properties in dense nuclear matter is discussed.
Only statistical errors are presented.
Only statistical errors are presented.
Only statistical errors are presented.
Positive pion and kaon production from Au+Au reactions have been measured as a function of beam energy over the range 2.0-10.7~AGeV. Both the kaon and the pion production cross-sections at mid-rapidity are observed to increase steadily with beam kinetic energy. The ratio of K$^+$ to $\pi^+$ mid-rapidity yields increases from 0.0271$\pm0.0015\pm0.0014$ at 2.0~AGeV to 0.202$\pm0.005\pm0.010$ at 10.7~AGeV and is larger than the K$^+$/$\pi^+$ ratio from p+p reactions over the same beam energy region. There is no indication of an onset of any new production mechanism in heavy-ion reactions in this energy range beyond rescattering of hadrons.
The centrality selection at each beam energy is the most central 5% of the total interaction cross-section (SIG(C=interaction) = 6.8b). A single exponential function in MT was fit simultaneously to the two kaonspectra at each beam energy D2(N)/D(MT)/D(YRAP)/2/PI/MT=D(N)/D(YRAP)/2/PI/T/(T+ M(KAON))/EXP((MT-M(KAON))/T). The fits reproduce the spectra well with two free parameters, the inverse slope parameter T and the rapidity density, D(N)/D(YRAP)in that rapidity slice. The mid-rapidity range for 2, 4, 6, 8 AGeV is ABS((YRAP-Ynn)/Ynn) < 0.25, for 10.7 AGeV the width is ABS((YRAP-Ynn)/Ynn) < 0.125, where Ynn is mid-rapidity in the laboratory frame. The errors are statistical only. The 1.96, 4. and 10.74 GeV are E866 data, another - E917 data.
The centrality selection at each beam energy is the most central 5% of the total interaction cross-section (SIG(C=interaction) = 6.8b). A single exponential function in MT was fit simultaneously to the two kaonspectra at each beam energy D2(N)/D(MT)/D(YRAP)/2/PI/MT=D(N)/D(YRAP)/2/PI/T/(T+ M(KAON))/EXP((MT-M(KAON))/T). The fits reproduce the spectra well with two free parameters, the inverse slope parameter T and the rapidity density, D(N)/D(YRAP)in that rapidity slice. The mid-rapidity range for 2, 4, 6, 8 AGeV is ABS((YRAP-Ynn)/Ynn) < 0.25, for 10.7 AGeV the width is ABS((YRAP-Ynn)/Ynn) < 0.125, where Ynn is mid-rapidity in the laboratory frame. The errors are statistical only. The 1.96, 4. and 10.74 GeV are E866 data, another - E917 data.
The centrality selection at each beam energy is the most central 5% of the total interaction cross-section (SIG(C=interaction) = 6.8b). The spectra were fit with a scaled exponential, D2(N)/D(YRAP)/D(MT)/2/PI/MT=D(N)/D(YRAP)/2/PI/(T**(2-L))/GAMMA(2-L,M(PION)/T)/MT**L/EXP(MT/T), where GAMMA(2-L,M(PION)/T), the complementary incomplete gamma function, is introduced in the normalization so that D(N)/D(YRAP) is a fitted parameter (and other free parameters are L and T). The mid-rapidity range for 2, 4 (E866 data), 6, 8 AGeV (E917 data) beam energy is ABS((YRAP-Ynn)/Ynn) < 0.25, for 10.7 AGeV (E917 data) the width is ABS((YRAP-Ynn)/Ynn) <0.125, where Ynn is mid-rapidity in the laboratory frame. The errors are statistical only.
Strange and multistrange baryon production is expected to be enhanced in heavy ion interactions if a phase transition from hadronic matter to a Quark-Gluon Plasma takes place. The production yields of Λ s, Λ s, Ξ − s, and Ξ + s relative to the production of negative particles are presented for sulphur-tungsten interactions at 200 GeV/ c per nucleon. These production yields are compared to those produced in proton-tungsten interactions and the enhancements of strange and multistrange baryons and antibaryons are presented.
Hyperon to negative production ratios with sulphur beam.
Hyperon to negative production ratios with proton beam.
Strange and multistrange baryon enhancements.
The double differential cross section of low momentum kaons ( ≤0.3GeV/c) from p+C collisions at subthreshold bombarding energies has been for the first time measured by the use of the CLAMSUD magnetic spectrometer installed at the CELSIUS storage ring. Invariant cross sections extracted from the data show a source rapidity shifted below the nucleon-nucleon rapidity, in agreement with the existence of multistep processes in the K+ production cross section. The total cross section of the inclusive reaction 12C(p,K+) at 1.2 GeV was extracted and compared with recent data systematics as a function of the proton bombarding energy.
No description provided.
The relative production yields and transverse mass spectra for Λ, Λ , Ξ − and Ξ + hyperons in proton-tungsten interactions are presented and compared with the WA85 results from central sulphur-tungsten interactions. A study of the negative particle yield has also been undertaken and the ratio of Λ hyperons to negative particles has been calculated.
No description provided.
No description provided.
No description provided.
Charged particle production in central S-S collisions at 200 GeV/ c per nucleon has been studied by the WA94 experiment at the CERN-SPS. Particle identification has been provided by the Omega RICH, while a silicon telescope in the Omega spectrometer and an array of MultiWire Proportional Chambers have been used to trace particles through the RICH detector. Production ratios and transverse mass spectra for π ± , K ± and p( p ) at central rapidity and p T > 1.3 GeV/ c are presented.
Distributions are fitted with (1/MT**1.5)*DSIG/DMT = CONST*EXP(-MT/SLOPE).
1.54 GeV ratio is calculated from the fit to the MT distribution.
1.54 GeV ratio is calculated from the fit to the MT distribution.
We measure forward cross sections for production of D+, D0, Ds, D*+, and Λc in collisions of π±, K±, and p on a nuclear target. Production induced by different beam particles is found to be the same within statistics. Strange and baryonic final states are seen to contribute appreciably to the total charm cross section, which our measurements indicate is larger than but consistent with QCD predictions. The energy dependence mapped out by these and previous measurements is consistent with theory. Leading-particle asymmetry measurements for K and p-induced charm production are also presented.
No description provided.
No description provided.
No description provided.
Results on K s 0 production at central rapidity in sulphur-tungsten interactions are presented. The selection procedure used to identify K s 0 particles through their decay to two charged pions is described. The m T spectra for K s 0 , Λ and Λ and the relative production rates K s 0 Λ and K s 0 Λ , calculated in the kinematic region p T > 1 GeV/ c and 2.5 ≤ y LAB ≤ 3.0, are discussed.
No description provided.
No description provided.
Strange and multistrange baryon and antibaryon production has been studied in sulphur sulphur interactions at 200 GeV/ c per nucleon at central rapidity using the CERN Omega Spectrometer. Particle production ratios and transverse mass spectra are presented for Λ, Ξ − , Λ and Ξ − .
No description provided.
No description provided.
No description provided.
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