The polarization of neutral Cascade and anti-Cascade hyperons produced by 800 GeV/c protons on a BeO target at a fixed targeting angle of 4.8 mrad is measured by the KTeV experiment at Fermilab. Our result of 9.7% for the neutral Cascade polarization shows no significant energy dependence when compared to a result obtained at 400 GeV/c production energy and at twice our targeting angle. The polarization of the neutral anti-Cascade is measured for the first time and found to be consistent with zero. We also examine the dependence of polarization on transverse production momentum.
Measured polarizations as a function of transverse momentum.
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ABSENT OF AN ABSOLUTE NEUTRON FLUX NORMALIZATION DIDN'T ALLOWED TO DEFINE THE CROSS-SECTION OF LAMBDA-K0-PARE PRODUCTION,SO IT WAS DEFINED THE RELATION OF CARBON AND CUPRUM CROSS-SECTION.
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The production of $J/\psi$ mesons in continuum $e^+e^-$ annihilations has been studied with the BABAR detector at energies near the $\Upsilon(4S)$ resonance, approximately 10.6 GeV. The mesons are distinguished from $J/\psi$ production in B decays through their center-of-mass momentum and energy. We measure the cross section $e^+e^-\to J/\psi X$ to be $2.52\pm 0.21\pm 0.21$ pb: for momentum above 2 GeV/c, it is $1.87\pm 0.10\pm 0.15$ pb. We set a 90% confidence level upper limit on the branching fraction for direct $\Upsilon(4S)$\to J/\psi X$ decays at $4.7\times 10^{-4}$.
Cross section measurement.
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The cross-section obtained in the paper is the model dependent estimation.
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Axis error includes +- 1/1 contribution (DUE TO BACKGROUND).
We present measurements of time-dependent CP-violating asymmetries in neutral B decays to several CP eigenstates. The measurement uses a data sample of 23 million Upsilon(4S)-->B-anti-B decays collected by the BABAR detector at the PEP-II asymmetric B Factory at SLAC. In this sample, we find events where one neutral B meson is fully reconstructed in a CP eigenstate containing charmonium and the flavor of the other neutral B meson is determined from its decay products. The amplitude of the CP-violating asymmetry, which in the Standard Model is proportional to sin2beta, is derived from the decay time distributions in such events. The result is sin2beta=0.34 +/- 0.20 (stat) +/- 0.05 (syst).
Standard Model predicts the time-dependent rate asymmetry as follows: A(t) = (B0(t)-BBAR0(t))/(B0(t)+BBAR0(t)) = SIN(2*BETA)*SIN(Delta(M)*t), where Delta(M) is the mass difference between the two B0 mass eigenstates. The total systematic error equals +0.50 -0.46.
The momentum distribution of electrons from decays of heavy flavor (charm and beauty) for midrapidity |y| < 0.35 in p+p collisions at sqrt(s) = 200 GeV has been measured by the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) over the transverse momentum range 0.3 < p_T < 9 GeV/c. Two independent methods have been used to determine the heavy flavor yields, and the results are in good agreement with each other. A fixed-order-plus-next-to-leading-log pQCD calculation agrees with the data within the theoretical and experimental uncertainties, with the data/theory ratio of 1.72 +/- 0.02^stat +/- 0.19^sys for 0.3 < p_T < 9 GeV/c. The total charm production cross section at this energy has also been deduced to be sigma_(c c^bar) = 567 +/- 57^stat +/- 224^sys micro barns.
Heavy-flavor decay electrons invariant differential cross-section An additional 10% normalization uncertainty is to add.
Differential charm cross section To obtain this value, the differential "charm-decay" electrons cross-section, integrated over PT>0.4 GeV/c, has been extrapolated down to PT=0 using the spectrum shape predicted by a fixed-order-plus-next-to-leading-log (FONLL)calculation. The contribution from beauty and beauty cascades, estimated to be 0.1 microbarn, has been substracted, and the c->e branching ratio used was 9.5 +- 1.0%.
Total charm cross section To obtain the total charm cross section, the differential charm cross section has been extrapolated to the whole rapidity range, using a HVQMNR rapidity distribution with aCTEQ5M PDF.
J/Psi production in p+p collisions at sqrt(s) = 200 GeV has been Measured in the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) over a rapidity range of -2.2 < y < 2.2 and a transverse momentum range of 0 < pT < 9 GeV/c. The statistics available allow a detailed measurement of both the pT and rapidity distributions and are sufficient to constrain production models. The total cross section times branching ratio determined for J/Psi production is B_{ll} sigma_pp^J/psi = 178 +/- 3(stat) +/- 53(syst) +/- 18(norm) nb.
J/PSI differential cross section, times dilepton branching ratio, versus transverse momentum PT, at mid rapidity : -0.35<y<0.35.
J/PSI differential cross section, times dilepton branching ratio, versus transverse momentum PT, at forward rapidities : absolute value of y belongs to [1.2;2.2].
Mean PT^2 value at mid rapidities : -0.35<y<0.35 The mean PT is obtained with a phenomonological fit of the J/PSI distribution in PT of the form (1/(2*PI*PT))*D(SIG)/DPT = A ( 1+(PT/B)^2)^-6 .The systematic error includes the incertainty from the maximum shape deviation permitted by the point-to-point correlated errors and from allowing the exponent of the fit fonctionto be a free parameter.
The PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) has measured J/psi production for rapidities 2.2 < y < 2.2 in Au+Au collisions at sqrt(s_NN) = 200 GeV. The J/psi invariant yield and nuclear modification factor R_AA as a function of centrality, transverse momentum and rapidity are reported. A suppression of J/psi relative to binary collision scaling of proton-proton reaction yields is observed. Models which describe the lower energy J/Psi data at the Super Proton Synchrotron (SPS) invoking only J/psi destruction based on the local medium density would predict a significantly larger suppression at RHIC and more suppression at mid rapidity than at forward rapidity. Both trends are contradicted by our data.
J/PSI invariant yield versus transverse momentum for 0-20%, 20-40%, 40-60%, 60-92% centrality at mid rapidity :,-0.35<y<0.35 An up/down correction, to translate each point at the center of it's relative bin, have been applied to the data.
J/PSI invariant yield versus transverse momentum for 0-20%, 20-40%, 40-60%, 60-92% centrality at forward rapidities : absolute value of y belongs to [1.2;2.2] An up/down correction, to translate each point at the center of it's relative bin, have been applied to the data.
Mean PT^2 values for different bins of centrality, at mid rapidities :-0.35<y<0.35,.
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