Author: Jianchun Wang
Publisher:
ISBN:
Category :
Languages : en
Pages : 78

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Author:
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Category :
Languages : en
Pages : 52

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Author:
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ISBN:
Category :
Languages : en
Pages : 154

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A study has been made of neutral strange baryons and pseudoscalar mesons produced in hadronic decays of the weak gauge boson V. The experiment was performed at the Stanford Linear Accelerator Center, which has the unique capability of colliding highly polarized electrons with unpolarized positrons. Overall production rates and spectra of the K° and the [Lambda]° (+[Lambda]°) were measured and compared with other experiments as well as with Quantum Chromodynamics calculations. The combination of the small, stable beam spots produced by the SLAC Linear Collider (SLC) and the precision vertexing capabilities of the SLC Large Detector (SLD) permitted the separation of the hadronic events into three quark flavor-enriched samples. An unfolding was performed to obtain flavor-pure samples, and for the first time measurements were made of K° and [Lambda]° (+[Lambda]°) production rates and spectra in uds, c, and b quark events at the Z° pole. This measurement revealed significant production differences. Utilizing the large quark production asymmetry due to the polarized electron beam, high-purity quark and antiquark jet samples were obtained. The first measurement of production differences of the [Lambda]° baryon in quark and antiquark jets was performed, which provided clear evidence for a leading particle effect at high momenta.

Author:
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Category :
Languages : en
Pages :

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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.

Author:
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Category :
Languages : en
Pages : 16

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We present preliminary evidence for leading particle production in hadronic decays of the Z° 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° decay. Similarly, more high momentum K− that K 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.

Author: Zygmunt Ajduk
Publisher: World Scientific
ISBN: 9814547107
Category :
Languages : en
Pages : 1878

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The 28th conference from the Rochester series was the major high energy physics conference in 1996. Volume one contains short reports on new theoretical and experimental results. Volume two consists of the review talks presented in the plenary sessions.

Author: S. SCHAEL
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

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Category :
Languages : en
Pages : 26

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Z° bosons have been produced by collisions of longitudinally polarized electrons with unpolarized positrons at the SLAC Linear Collider and their decays have been recorded by the SLD experiment. We present preliminary measurements of the properties of the resulting Z° decays into multi-hadronic final states. We find good agreement with the predictions of perturbative QCD and fragmentation models.

Author:
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Category :
Languages : en
Pages : 239

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This dissertation presents a study of strange vector meson production, {open_quotes}leading particle{close_quotes} effect and a first direct measurement of the strangeness suppression parameter in hadronic decays of the neutral electroweak boson, Z°. The measurements were performed in ee− collisions at the Stanford Linear Accelerator Center (SLAC) with the SLC Large Detector (SLD) experiment. A new generation particle ID system, the SLD Cerenkov Ring Imaging Detector (CRID) is used to discriminate kaons from pions, enabling the reconstruction of the vector mesons over a wide momentum range. The inclusive production rates of? and K*° and the differential rates versus momentum were measured and are compared with those of other experiments and theoretical predictions. The high longitudinal polarisation of the SLC electron beam is used in conjunction with the electroweak quark production asymmetries to separate quark jets from antiquark jets. K*° production is studied separately in these samples, and the results show evidence for the {open_quotes}leading particle{close_quotes} effect. The difference between K*° production rates at high momentum in quark and antiquark jets yields a first direct measurement of strangeness suppression in jet fragmentation.

Author: Catherine Vander Velde
Publisher: World Scientific
ISBN: 9814547700
Category :
Languages : en
Pages : 1042

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