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Average charged multiplicities have been measured separately in b, c and light quark (u, d, s) events from Z[sup 0] decays measured in the SLD experiment. Impact parameters of charged tracks were used to select enriched samples of b and light quark events, and reconstructed charmed mesons were used to select c quark events. We measured the charged multiplicities:[anti n][sub uds]= 20.21[+-] 0.10 (stat.)[+-] 0.17 (syst.), [anti n][sub c]= 21.28[+-] 0.46 (stat.)[sub -0.33][sup+0.38] (syst.) and[anti n][sub b]= 23.14[+-] 0.10 (stat.)[sub -0.34][sup+0.35] (syst.), from which we derived the differences between the total average charged multiplicities of c or b quark events and light quark events:[Delta][anti n][sub c]= 1.07[+-] 0.47 (stat.)[sub -0.30][sup+0.36] (syst.) and[Delta][anti n][sub b]= 2.93[+-] 0.14 (stat.)[sub -0.29][sup+0.30] (syst.). We compared these measurements with those at lower center-of-mass energies and with perturbative QCD predictions. These combined results are in agreement with the QCD expectations and disfavor the hypothesis of flavor-independent fragmentation.
Average charged multiplicities have been measured separately in b, c and light quark (u, d, s) events from Z° decays measured in the SLD experiment. Impact parameters of charged tracks were used to select enriched samples of b and light quark events, and reconstructed charmed mesons were used to select c quark events. We measured the charged multiplicities: {anti n}{sub uds} = 20.21 ± 0.10 (stat.) ± 0.17 (syst.), {anti n}{sub c} = 21.28 ± 0.46 (stat.){sub -0.33}{sup +0.38} (syst.) and {anti n}{sub b} = 23.14 ± 0.10 (stat.){sub -0.34}{sup +0.35} (syst.), from which we derived the differences between the total average charged multiplicities of c or b quark events and light quark events: [Delta]{anti n}{sub c} = 1.07 ± 0.47 (stat.){sub -0.30}{sup +0.36} (syst.) and [Delta]{anti n}{sub b} = 2.93 ± 0.14 (stat.){sub -0.29}{sup +0.30} (syst.). We compared these measurements with those at lower center-of-mass energies and with perturbative QCD predictions. These combined results are in agreement with the QCD expectations and disfavor the hypothesis of flavor-independent fragmentation.
Average charged multiplicities have been measured separately for[ital b, c] and light quark ([ital u, d, s]) events from Z[sup 0] decays at SLD. Impact parameters of charged tracks were used to select enriched samples of[ital b] and light quark events. We measured the charged multiplicities:[bar[ital n]][sub[ital uds]]= 19.80[+-] 0.09 ([ital stat])[+-] 0.57 ([ital syst]), [bar[ital n]][sub[ital c]]= 21.17[+-] 0.44 ([ital stat])[+-] 1.01 ([ital syst]) and[bar[ital n]][sub[ital b]][+-]23.14[+-] 0.09 ([ital stat])[+-] 1.03 ([ital syst]) (PRELIMINARY), from which we derived the differences between the total average charged multiplicities of[ital c] or[ital b] quark events and light quark events:[delta][bar[ital n]][sub[ital c]]= 1.37[+-] 0.45 ([ital stat])[+-] 0.86 ([ital syst]) and[delta][bar[ital n]][sub[ital b]]= 3.34[+-] 0. 13 ([ital stat])[+-] 0.77 ([ital syst]) (PRELIMINARY). We compared these measurements with those at lower center-of-mass energies and with QCD predictions.
Average charged multiplicities have been measured separately for {ital b, c} and light quark ({ital u, d, s}) events from Z° decays at SLD. Impact parameters of charged tracks were used to select enriched samples of {ital b} and light quark events. We measured the charged multiplicities: {bar {ital n}}{sub {ital uds}} = 19.80 ± 0.09 ({ital stat}) ± 0.57 ({ital syst}), {bar {ital n}}{sub {ital c}} = 21.17 ± 0.44 ({ital stat}) ± 1.01 ({ital syst}) and {bar {ital n}}{sub {ital b}}±23.14 ± 0.09 ({ital stat}) ± 1.03 ({ital syst}) (PRELIMINARY), from which we derived the differences between the total average charged multiplicities of {ital c} or {ital b} quark events and light quark events: [delta]{bar {ital n}}{sub {ital c}} = 1.37 ± 0.45 ({ital stat}) ± 0.86 ({ital syst}) and [delta]{bar {ital n}}{sub {ital b}} = 3.34 ± 0. 13 ({ital stat}) ± 0.77 ({ital syst}) (PRELIMINARY). We compared these measurements with those at lower center-of-mass energies and with QCD predictions.
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.
Using the precision vertex detectors of the Mark 2 at the SLC, an impact parameter tag was developed to select a sample of hadronic Z° decays enriched in its fraction of bottom quark events. The nominal tagging method requires that there be at least three tracks whose impact parameters are inconsistent with the track having originated at the electron-position interaction point. A tagging efficiency for b{bar b} events of 50% with a enriched sample purity of 85% was achieved. This impact parameter tag was used to measure the fraction hadronic Z° decays which produce b{bar b} events, F{sub b}. It is found that F{sub b} = 0.232{sub -0.045}{sup +0.053} (stat) {sub -0.021}{sup +0.025} (syst). This result is consistent with those found using other tagging methods as well as the Standard Model prediction of 0.217. The b{bar b}-enriched event sample was also used to measure the difference between the average charged multiplicity of b{bar b} events and that of all hadronic Z° decays,?{bar n}{sub b} = 2.11 {plus minus} 1.82(stat) {plus minus} 0.57(syst). Using previous measurements of the total hadronic charged multiplicity, the corresponding total multiplicity for b{bar b} events is {bar n}{sub b}=23.05 {plus minus} 1.82 (stat) {plus minus} 0.60 (syst). Subtracting the contribution to the multiplicity from B hadron decays yields the multiplicity of the b{bar b} non-leading system, {bar n}{sub nl} = 12.04 {plus minus} 1.82 (stat) {plus minus} 0.63(syst). Comparing this non-leading multiplicity to the total hadronic multiplicity data at lower energy supports the hypothesis that the non-leading particle production is independent of the flavor of the initial quarks.
This book highlights two essential analyses of data collected during the LHCb experiment, based on the Large Hadron Collider at CERN. The first comprises the first observation and studies of matter-antimatter asymmetries in two three-body b-baryon decays, paving the way for more precise measurements of the relatively unknown decay properties of b-baryon decays. The second is an analysis of a charged B meson decay to three charged pions, where previously large matter-antimatter asymmetries were observed in a model-independent analysis. Here a model of the decay amplitude is constructed using the unitarity-conserving ‘K-matrix’ model for the scalar contributions, so as to gain an understanding of how the previously observed matter-antimatter asymmetries arise; further, the model’s construction yields the most precise and comprehensive study of this decay mode to date.
We present a measurement of the production cross section for ZW and ZZ boson pairs in final states with a pair of charged leptons, from the decay of a Z boson, and at least two jets, from the decay of a W or Z boson, using the full sample of proton-antiproton collisions recorded with the CDF II detector at the Tevatron, corresponding to 8.9 fb(̂-1) of integrated luminosity. We increase the sensitivity to vector boson decays into pairs of quarks using a neural network discriminant that exploits the differences between the spatial spread of energy depositions and charged-particle momenta contained within the jet of particles originating from quarks and gluons. Additionally, we employ new jet energy corrections to Monte Carlo simulations that account for differences in the observed energy scales for quark and gluon jets. The number of signal events is extracted through a simultaneous fit to the dijet mass spectrum in three classes of events: events likely to contain jets with a heavy-quark decay, events likely to contain jets originating from light quarks, and events that fail these identification criteria. We determine the production cross section to be 2.5 +2.0 -1.0 pb (