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The authors have measured the production rates as a function of scaled energy x of prompt charmed pseudoscalar D[sup[+-]] and vector D*[sup[+-]] mesons in hadronic Z[sup 0] decays. The prompt signal components were isolated from the background of D mesons from B hadron decays using impact parameters of reconstructed D[sup[+-]][yields] K[sup[minus-plus]][pi][sup[+-]][pi][sup[+-]] and D*-daughter D[sup 0][yields] K[sup[minus]][pi][sup+] and D[sup 0][yields] K[sup[minus]][pi][sup+][pi][sup[minus]][pi][sup+] candidates. Using the combined meson production rates the authors have measured the fraction of hadronic Z[sup 0] decays into c[bar c], R[sub c]= 0.182[+-] 0.027 (stat.)[+-] 0.012 (syst.) (Preliminary). Comparison of the D*[sup[+-]] and D[sup[+-]] rates gives a direct probe of vector (V) vs. pseudoscalar (P) meson production for charmed quarks, and for x> 0.4 they have measured P[sub V]= V/(V+ P)= 0.65[+-] 0.09(stat.)[+-] 0.03(syst.)[+-] 0.03 (BR) (Preliminary). They have measured the degree of spin alignment of the D*[sup[+-]] mesons along their flight direction and find it to be consistent with zero. They compared the latter two results with QCD- and model-based predictions of charm-quark jet fragmentation.

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Languages : en
Pages : 24

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The authors have measured the production rates as a function of scaled energy x of prompt charmed pseudoscalar D{sup ±} and vector D*{sup ±} mesons in hadronic Z° decays. The prompt signal components were isolated from the background of D mesons from B hadron decays using impact parameters of reconstructed D{sup ±} → K{sup {minus_plus}}?{sup ±}?{sup ±} and D*-daughter D° → K−? and D° → K−?+?−?+ candidates. Using the combined meson production rates the authors have measured the fraction of hadronic Z° decays into c{bar c}, R{sub c} = 0.182 {+-} 0.027 (stat.) {+-} 0.012 (syst.) (Preliminary). Comparison of the D*{sup {+-}} and D{sup {+-}} rates gives a direct probe of vector (V) vs. pseudoscalar (P) meson production for charmed quarks, and for x> 0.4 they have measured P{sub V} = V/(V + P) = 0.65 {+-} 0.09(stat.) {+-} 0.03(syst.) {+-} 0.03 (BR) (Preliminary). They have measured the degree of spin alignment of the D*{sup {+-}} mesons along their flight direction and find it to be consistent with zero. They compared the latter two results with QCD- and model-based predictions of charm-quark jet fragmentation.

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Languages : en
Pages : 9

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USING HADRONIC Z° DECAYS RECORDED BY THE SLD EXPERIMENT AT SLAC, WE HAVE MEASURED THE VECTOR/(VECTOR+PSEUDOSCALAR) PRODUCTION RATIO, V/(V + P), FOR THE PROMPT CHARMED MESONS D{sup *+} AND D. USING THE CHANNELS D{sup *+} → D°?+{sub S}, D° → K−?+, AND D° → K−?+?−?+, AS WELL AS D+ → K−?+?−, WE FIND V/(V + P) = 0.61 +/- 0.09(STAT.) +/- 0.03(BR), WHICH DISFAVORS THE EXPECTATION OF 0.75 FROM NAIVE SPIN COUNTING. WE HAVE ALSO MEASURED THE DEGREE OF D{sup *+} SPIN ALIGNMENT ALONG THE FLIGHT DIRECTION AND FIND IT TO BE CONSISTENT WITH ZERO FOR D{sup *+} FRACTIONAL MOMENTA x = E{sub D*}/E{sub BEAM}

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Languages : en
Pages : 19

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Using hadronic Z° decays recorded by the SLD experiment at SLAC, we have measured the vector/(vector+pseudoscalar) production ratio, V/(V+P), for the prompt charmed mesons, D{sup *+} and D. Using the channels D{sup *+}→D°?+{sub s}, D°→ K−?+, and D°→ K{sup - }?+?−?+, as well as D+??2192? K−?+?−, we find V/(V+P) = 0.57 ± 0.07 ({ital stat})± 0.02({ital BR}), which disfavors the expectations of 0.75 from naive spin counting. We have also measured the degree of D{sup *+} spin alignment along the flight direction and find it to be consistent with the zero for D{sup *+} fractional momenta? {triple_bond} E{sub D{sup *}}/D{sub {ital beam}}

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Languages : en
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USING HADRONIC Z[sup 0] DECAYS RECORDED BY THE SLD EXPERIMENT AT SLAC, WE HAVE MEASURED THE VECTOR/(VECTOR+PSEUDOSCALAR) PRODUCTION RATIO, V/(V+ P), FOR THE PROMPT CHARMED MESONS D[sup*+] AND D[sup+]. USING THE CHANNELS D[sup*+][yields] D[sup 0][pi][sup+][sub S], D[sup 0][yields] K[sup -][pi][sup+], AND D[sup 0][yields] K[sup -][pi][sup+][pi][sup -][pi][sup+], AS WELL AS D[sup+][yields] K[sup -][pi][sup+][pi][sup -], WE FIND V/(V+ P)= 0.61+/- 0.09(STAT.)+/- 0.03(BR), WHICH DISFAVORS THE EXPECTATION OF 0.75 FROM NAIVE SPIN COUNTING. WE HAVE ALSO MEASURED THE DEGREE OF D[sup*+] SPIN ALIGNMENT ALONG THE FLIGHT DIRECTION AND FIND IT TO BE CONSISTENT WITH ZERO FOR D[sup*+] FRACTIONAL MOMENTA x= E[sub D*]/E[sub BEAM][gt] 0.2. We compare these results with QCD model predictions.

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Languages : en
Pages : 26

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We have measured production of?{sup {+-}},?{sup {+-}}, {ital p}/{ital {bar p}},?° and?°/{bar?}° as a function of momentum in inclusive hadronic {ital Z}° decay events and separately in events containing primary light-({ital uds}) and {ital b}-quarks. The SLD Cherenkov Ring Imaging Detector was used to identify charged pions, kaons, and protons over most of the available momentum range 0.8>{ital p}>33 GeV/c. The neutral?°{sub s} and {Lambda}° were reconstructed using the??− and {ital p}?− decay modes, respectively. We present the first comparisons of momentum of charged tracks measured in the SLD Vertex Detector. Substantial differences are observed, consistent with the kinematics of {ital B}-hadron production in Z° decays and the properties of {ital B}-hadron decays as measured at lower energies.

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Languages : en
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We present preliminary evidence for leading particle production in hadronic decays of the Z[sup 0] to light quark pairs using 150,000 events recorded in the SLD experiment at SLAC. The highly polarized electron beam produced by the SLC is used to tag quark and antiquark jets, and a signed impact parameter technique is employed to reject heavy flavor events. Charged hadrons are identified in the SLD Cherenkov Ring Imaging Detector (CRID) and[Lambda]/[bar[Lambda]] are reconstructed using their charged decay modes. In a high purity sample of quark jets, the baryon momentum spectrum is harder that that of the antibaryon, and conversely for a sample of antiquark jets, supporting the hypothesis that the faster particles in jets are more likely to carry the primary quark or antiquark from the Z[sup 0] decay. Similarly, more high momentum K[sup -] that K[sup+] are observed in quark jets and conversely for antiquark jets, consistent with the hypothesis that leading K[sup[+-]] are produced predominantly in s[bar s] events rather than[ital u][bar[ital u]] events.

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Languages : en
Pages : 5

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In 1992 the SLD experiment at SLAC collected over 11,000 hadronic decay events of Z[sup 0] bosons produced in collisions of polarised electrons with unpolarised positrons delivered by the SLC. Preliminary experimental results are presented on tests of the value of the gluon spin involving events containing three hadronic jets measured in the final state. A leading order QCD prediction is found to be in agreement with the data, whilst a model including scalar gluons is clearly excluded. Effects of the electron beam polarisation upon the orientation of the three-jet event plane are discussed.

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Languages : en
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We have measured production of[pi][sup[+-]], [Kappa][sup[+-]], [ital p]/[ital[bar p]], [Kappa][sup 0] and[Lambda][sup 0]/[bar[Lambda]][sup 0] as a function of momentum in inclusive hadronic[ital Z][sup 0] decay events and separately in events containing primary light-([ital uds]) and[ital b]-quarks. The SLD Cherenkov Ring Imaging Detector was used to identify charged pions, kaons, and protons over most of the available momentum range 0.8[lt][ital p][lt]33 GeV/c. The neutral[Kappa][sup 0][sub s] and[Lambda][sup 0] were reconstructed using the[pi][sup+][pi][sup -] and[ital p][pi][sup -] decay modes, respectively. We present the first comparisons of momentum of charged tracks measured in the SLD Vertex Detector. Substantial differences are observed, consistent with the kinematics of[ital B]-hadron production in Z[sup 0] decays and the properties of[ital B]-hadron decays as measured at lower energies.

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A search for decays of the B[sub c] meson was performed using data collected from 1990--1995 with the OPAL detector on or near the Z[sup 0] peak at LEP. The decay channels B[sub c][sup+][r-arrow] J/[psi][pi][sup+], B[sub c][sup+][r-arrow] J/[psi]a[sub 1][sup+] and B[sub c][sup+][r-arrow] J/[psi][ell][sup+][nu] were investigated, where[ell] denotes an electron or a muon. Two candidates are observed in the mode B[sub c][sup+][r-arrow] J/[psi][pi][sup+], with an estimated background of (0.63[+-] 0.20) events. The weighted mean of the masses of the two candidates is (6.32[+-] 0.06) GeV/c[sup 2], which is consistent with the predicted mass of the B[sub c] meson. One candidate event is observed in the mode B[sub c][sup+][r-arrow] J/[psi][ell][sup+][nu], with an estimated background of (0.82[+-] 0.19) events. No candidate events are observed in the B[sub c][sup+][r-arrow] J/[psi]a[sub 1][sup+] decay mode, with an estimated background of (1.10[+-] 0.22) events. Upper bounds at the 90% confidence level are set on the production rates for these processes.