A determination of branching ratios for D meson decays into all charged particle final states is reported. The values obtained: (D ± → K ∓ π ± π ± /all D ± ) = (14 ± 6)% and ( D 0 /D 0 → K ± π ∓ π + π − /all D 0 /D 0 ) = (10 ± 4)%, are higher than those currently accepted. This result, if confirmed, implies a corresponding reduction in the accepted values for some total cross section measurements. Revised inclusive cross sections for D meson production in the forward hemisphere in π − p and pp interactions at 360 GeV/ c , are presented.
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We have measured the inclusive production properties of D and D messons produced from pp interactions at s =27.4 GeV . The differential production cross section is well represented by the empirical form d 2 σ d x F d P 2 T = 1 2 [σ ( D / D )(n+1)b](1−|x F |) n exp (−bp 2 T ) with n=4.9 ± 0.5, b=(1.0±0.1)( GeV /c) −2 , and the inclusive D / D cross section σ ( D / D ) is (30.2±3.3) ωb. The QCD fusion model predicts D / D production which is in good agreement with our data except for the magnitude of the cross section which depends sensitively on the assumed mass of the charm quark.
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Results of fitting the differential distributions in x F and p T 2 of D mesons produced in 400 GeV/ c p-p interactions to the form d 2 σ d x F d p T 2 ∝(1−x F ) n exp [−(p T 2 /〈p T 2 〉)] are discussed. The D + distribution is found to be relatively hard [ n =3.1±0.8〈 P t 2 〉=1.32±0.27 (GeV/ c ) 2 ] and the D̄ 0 distribution relatively soft [ n =8.1±1.9,〈 p T 2 〉=0.62±0.14 (GeV/ c ) 2 ] compared to the average for all D's [ n =4.9±0.5,〈 p T 2 〉=0.99±0.10 (GeV/ c ) 2 ]. It is suggested that these distributions could reflect contribution of leading di-quarks in pp collisions. Comparison is made with evidence for leading quarks in charm production in 360 GeV/ cπ − p interactions.
The invariant (C=INV) and non-invariant (C=NON-INV) distributions are fitted to (1-XL)**POWER. Pt distribution is fitted to EXP(-PT**2/SLOPE).
The $\jpsi$ $\pt$ spectrum and nuclear modification factor ($\raa$) are reported for $\pt < 5 \ \gevc$ and $|y|<1$ from 0\% to 60\% central Au+Au and Cu+Cu collisions at $\snn = 200 \ \gev$ at STAR. A significant suppression of $\pt$-integrated $\jpsi$ production is observed in central Au+Au events. The Cu+Cu data are consistent with no suppression, although the precision is limited by the available statistics. $\raa$ in Au+Au collisions exhibits a strong suppression at low transverse momentum and gradually increases with $\pt$. The data are compared to high-$\pt$ STAR results and previously published BNL Relativistic Heavy Ion Collider results. Comparing with model calculations, it is found that the invariant yields at low $\pt$ are significantly above hydrodynamic flow predictions but are consistent with models that include color screening and regeneration.
The invariant yield versus transverse momentum for |y| < 1 in 0-20% centrality in Au+Au collisions (solid circles). The results are compared to high-$p_T$ (3 < $p_T$ < 10 GeV/c) results from STAR [9] (solid squares) and PHENIX data [8] (open squares).
The invariant yield versus transverse momentum for |y| < 1 in 20-40% centrality in Au+Au collisions (solid circles). The results are compared to high-$p_T$ (3 < $p_T$ < 10 GeV/c) results from STAR [9] (solid squares) and PHENIX data [8] (open squares).
The invariant yield versus transverse momentum for |y| < 1 in 40-60% centrality in Au+Au collisions (solid circles). The results are compared to high-$p_T$ (3 < $p_T$ < 10 GeV/c) results from STAR [9] (solid squares) and PHENIX data [8] (open squares).
We present the measurements of the Λ c production cross section in proton-proton interactions at s =27.4 GeV and give new limits on the exclusive branching ratio Λ c →pK + π − .
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We report Λ 0 -hyperon polarization measurements at the CERN intersecting storage rings from √ s of 31 to 62 GeV. P Λ 0 changes insignificantly, +(0.8±1.7)%, over this range of √ s . However, P Λ 0 is observed to grow with Feynman- x F and with transverse momentum. At an average p t of 1.1 GeV/ c , P Λ 0 depends linearly on x F and approaches −40% at x F =0.8.
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The differential cross sections for the elastic scattering of π+, π−, K+, K−, p, and p¯ on protons have been measured in the t interval -0.04 to -0.75 GeV2 at five momenta: 50, 70, 100, 140, and 175 GeV/c. The t distributions have been parametrized by the quadratic exponential form dσdt=Aexp(B|t|+C|t|2) and the energy dependence has been described in terms of a single-pole Regge model. The pp and K+p diffraction peaks are found to shrink with α′∼0.20 and ∼0.15 GeV−2, respectively. The p¯p diffraction peak is antishrinking while π±p and K−p are relatively energy-independent. Total elastic cross sections are calculated by integrating the differential cross sections. The rapid decline in σel observed at low energies has stopped and all six reactions approach relatively constant values of σel. The ratio of σelσtot approaches a constant value for all six reactions by 100 GeV, consistent with the predictions of the geometric-scaling hypothesis. This ratio is ∼0.18 for pp and p¯p, and ∼0.12-0.14 for π±p and K±p. A crossover is observed between K+p and K−p scattering at |t|∼0.19 GeV2, and between pp and p¯p at |t|∼0.11 GeV2. Inversion of the cross sections into impact-parameter space shows that protons are quite transparent to mesons even in head-on collisions. The probability for a meson to pass through a proton head-on without interaction inelastically is ∼20% while it is only ∼6% for an incident proton or antiproton. Finally, the results are compared with various quark-model predictions.
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The inclusive production cross sections of pions, kaons, protons, and antiprotons in p p and pp interactions at √ s =53 GeV are compared in the kinematic range | y | < 0.8 and p T < 1.5 GeV/ c . We observe differences in the K + /K − and p /p ratios for the two data samples. Although the bulk of the particles are produced with the same momentum and rapidity distributions in p p and pp collisions, we observe difference in these distributions for produced protons and antiprotons.
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We have studied the inclusive production of the hadrons π ± , K ± , p, p , Λ, Λ , ρ and ⋉ in the central region at the ISR s = 53 GeV , in both pp and p p collisions. Differences are observed only for K ± , p, and p production. We then study also correlations between low- p T pp and p p pairs in the two types of collisions, separating the contribution from baryon pair production and from the incident particles (stopping protons). We observe a positive correlation between two stopping protons; between the production of two pairs, and between a stopping proton and a pair production, there are negative correlations.
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The ratio of π+p to pp elastic scattering is found to be smoothly varying over the range −t=0.03 to 0.4 GeV2. It is well fitted by a single exponential, indicating the forward behavior must be quite similar for the two reactions.
ACTUALLY THE DATA ARE THE EXPONENTIAL SLOPE OF THE RATIO OF D(SIG)/DT FOR THE TWO REACTIONS.