Λ , Ξ and Ω yields and transverse mass spectra have been measured in Pb-Pb and p-Pb collisions at 158 A GeV/ c . The yields in Pb-Pb interactions are presented as a function of the collision centrality and compared with those obtained from p-Pb collisions. Strangeness enhancement is observed which increases with centrality and with the strangeness content of the hyperon.
Measured slope for P-PB with POWER=3/2.
Measured slope for PB-PB with POWER=3/2.
Measured slope for P-PB with POWER=1.0.
We present total and differential cross sections for charm mesons produced in 600 GeV/ c π - emulsion interactions. Fits to d 2 σ / dx F dp T 2 ∞ (1−| x F |) n exp (- bp T 2 ) for 676 electronically reconstructed D mesons with x F >0 give n =4.25±0.24 ( stat .)±0.23 ( syst .) and b =0.76±0.03±0.03 ( GeV / c ) -2 . The total inclusive D + and D 0 cross sections are σ ( π - N → D ± ; x F >0) = 8.66±0.46±1.96 μb nucleon and σ(π - N→D 0 D 0 ; x F >0)=22.05±1.37±4.82μb nucleonk, where a linear dependence on the mean atomic weight of the target is assumed. These results are compared to next-to-leading order QCD predictions.
Linear A-dependence. Different modes of the charm mesons detection were used (see text for detail). The differential cross section is fitted by the equation : D2(SIG)/D(XL)/D(PT**2) = CONST*(1-XL)**POWER*EXP(-SLOPE*PT**2).
Linear A-dependence.
We report results on D 0 and D + production in proton-emulsion interactions at s =38.7 GeV. A fit to the form (1−| x F |) n exp (−bp 2 T ) yields n=6.9 +1.9 −1.8 and b=0.84 +0.10 −0.08 (GeV/ c ) −2 . The total inclusive cross section, is assuming linear A dependence, is measured to be 38±3(stat.) ±13 (sys.) μ b for the D 0 and 38±9±14 μ b for the D + . A comparison of these results with previous measurements indicates that nuclear effects do not strongly influence charm production. The predictions of QCD are in good agreement with our data.
The differential cross section is fitted by the equation : D2(SIG)/D(XL)/D(PT**2) = CONST*(1-XL)**POWER*EXP(-SLOPE*PT**2).
The differential cross section is fitted by the equation : D2(SIG)/D(XL)/D(PT**2) = CONST*(1-XL)**POWER*EXP(-SLOPE*PT**2).
Linear A-dependence. Different modes of the charm mesons detection were used (see text for detail).
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The inclusive production of charmed baryonsΛc+ by 40–70 GeV neutrons on carbon has been observed. The decays\(\Lambda _c^ + \to \bar K^0 p\pi ^ + \pi ^ -\) (130 ± 18 events) andΛc+→Λ0π+π+π− (57±14 events) have been detected. The mean value ofΛc+ mass is (2,268±6) MeV/c2. The invariant cross section forX>0.5 is described byE·d3σ/dp3∝ exp(−)bPT·(1−X)n withb=(2.5±0.6) (GeV/c)−1 andn=(1.5±0.5).
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The reactions π+p→Σ+(1385)K+ and π+p→Σ+(1385)K*+(890) are examined. The Σ+(1385)K+ differential cross section for −t′<0.5 GeV2 and spin density matrix elements agree with a Regge-pole model incorporating (nondegenerate) vector and tensor K* exchange with dominant M1 coupling. The Σ+(1385)K*+(890) density matrix elements are consistent with the quark-additivity predictions. A Y*+ at a mass of 1700 MeV is also observed in the Λπ+ mass distribution, produced opposite both K+ and K*+(890).
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GOTTFRIED-JACKSON FRAME.
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Axis error includes +- 7/7 contribution.
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IM(AMP) VIA OPTICAL THEOREM FROM TOTAL CROSS SECTIONS OF L. M. VASILYEV ET AL., PL 36B, 528 (1971).