Download or read book Light Quark Fragmentation and a Measurement of A sub S at the SLD written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We have studied the fragmentation process in Z[sup 0][yields] light-flavor (u[bar u], d[bar d], s[bar s]) events by measuring the differential cross sections for the production of the identified hadrons[pi][sup[+-]], K[sup[+-]], p/[bar p], K[sub s][sup 0], [Lambda][sup 0]/[bar[Lambda]][sup 0], K*[sup 0]/[bar K]*[sup 0] and[phi], and by performing a preliminary study of correlations in rapidity between pairs of identified[pi][sup[+-]], K[sup[+-]], and p/[bar p]. Short range charge correlations are observed between all combinations of these three hadron species. A strong long range correlation is observed between all combinations of these three hadron species. A strong long range correlation is observed for high-momentum charged kaon pairs, and weaker[pi][sup+][pi][sup -], [pi][sup+]K[sup -] and pK[sup -] correlations are observed. The SLC beam polarization is used to tag the quark hemisphere in each event, allowing the first study of rapidities signed such that positive rapidity is along the quark rather than antiquark direction. Distributions of signed rapidities and of ordered differences between signed rapidities provide new insights into leading particle production and several new tests of fragmentation models. We have used these correlation studies to perform a preliminary direct measurement of the parity violating coupling of the Z[sup 0] to strange quarks, A[sub s]. Our result is: A[sub s]= 0.82[+-] 0.10(stat.)[+-] 0.08(syst.)(preliminary).

Download or read book Light Quark Fragmentation in Polarized Z Decays at SLD written by and published by . This book was released on 2000 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors report results on two physics topics from the SLD experiment at the SLAC Linear Collider, using the full sample of 550,000 events of the type ee --> Z° -->q anti-q. The electron beam was polarized, enabled the quark and antiquark hemispheres to be tagged in each event. One physics topics topic is the first study of rapidities signed such that positive rapidity is along the quark rather than antiquark direction. Distributions of ordered in signed rapidity between pairs of particles are analyzed, providing the first direct observation of baryon number ordering along the q anti-q axis. The other topic is the first direct measurement of A{sub s}, the parity-violating coupling of the Z° to strange quarks, by measuring the left-right forward-backward production asymmetry in polar angle of the tagged s quark. They obtain A{sub s} = 0.895 " 0.066(stat.) " 0.062(syst.), which is consistent with the Standard Model and is currently the most precise measurement of this quantity.

Download or read book Hadron Fragmentation Functions and Leading Particle Effects in Hadronic Z sup 0 Decays New Results from SLD written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors have measured the differential cross sections for the production of[pi][sup[+-]], K[sup[+-]], K[sup 0], K*(892), [phi](1,020), p and[Lambda] in hadronic Z[sup 0] decays and in subsets of flavor-tagged Z[sup 0][yields] light quark (u[anti u], d[anti d], or s[anti s]), Z[sup 0][yields] c[anti c] and Z[sup 0][yields] b[anti b] events. Charged hadrons were identified with the SLD Cherenkov ring imaging detector. The vertex detector was employed to select flavor enriched samples and the polarized electron beam from SLC was used to tag quark and anti-quark jets. The authors observe a flavor dependence in the hadron fragmentation functions. The authors present evidence for leading particle production in hadronic decays of the Z[sup 0] boson to light-flavor jets and a direct measurement of the strangeness suppression factor[gamma][sub s].

Download or read book An Improved Measurement of the B Quark Fragmentation Function in Z Decays at SLD written by and published by . This book was released on 1999 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present preliminary results of a new measurement of the b quark fragmentation function in Z° decays using a novel kinematic B hadron energy reconstruction technique. The measurement is performed using 150,000 hadronic Z° events recorded in the SLD experiment at SLAC between 1996 and 1997. The small and stable SLC beam spot and the CCD-based vertex detector are used to reconstruct topological B-decay vertices with high efficiency and purity, and to provide precise measurements of the kinematic quantities used in this technique. We measure the B energy with good efficiency and resolution over the full kinematic range. We compare the scale B hadron energy distribution with several functional forms of the B hadron energy distribution and predictions of several models of b quark fragmentation. Several functions including JETSET + Peterson are excluded by the data. The average scaled energy of the weakly decaying B hadron is measured to be x{sub B} = 0.719 " 0.005 (stat) " 0.007 (syst) " 0.001 (model) (preliminary).

Download or read book Hadron Fragmentation Functions and Leading Particle Effects in Hadronic Z Decays written by and published by . This book was released on 1997 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors have measured the differential cross sections for the production of [pi]{sup {+-}}, K{sup {+-}}, K°, K*(892), [phi](1,020), p and [Lambda] in hadronic Z° decays and in subsets of flavor-tagged Z° → light quark (u{anti u}, d{anti d}, or s{anti s}), Z° → c{anti c} and Z° → b{anti b} events. Charged hadrons were identified with the SLD Cherenkov ring imaging detector. The vertex detector was employed to select flavor enriched samples and the polarized electron beam from SLC was used to tag quark and anti-quark jets. The authors observe a flavor dependence in the hadron fragmentation functions. The authors present evidence for leading particle production in hadronic decays of the Z° boson to light-flavor jets and a direct measurement of the strangeness suppression factor [gamma]{sub s}.

Download or read book Identified Hadron Production and Light Quark Fragmentation in Z sup 0 Decays written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We have measured the differential cross sections for the production of[pi][sup+], K[sup+], K[sup 0], K*[sup 0], [phi], p, [Lambda] and their corresponding antiparticles in separate samples of flavor-tagged Z[sup 0][yields] light-flavor (u[bar u], d[bar d], or s[bar s]), Z[sup 0][yields] b[bar b] events. Clear flavor dependences are observed, and the results are compared with the predictions of three fragmentation models. We have also performed a direct measurement of A[sub s], the parity-violating coupling of the Z[sup 0] to strange quarks, by measuring the left-right-forward-backward production asymmetry in polar angle of the tagged s quark. Our preliminary result is A[sub s]= 0.82[+-] 0.10(stat.)[+-] 0.07(syst.).

Download or read book Identified Hadron Production and Light Quark Fragmentation in Z Decays written by and published by . This book was released on 1998 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: We have measured the differential cross sections for the production of [pi], K, K°, K*°, [phi], p, [Lambda] and their corresponding antiparticles in separate samples of flavor-tagged Z° 2!light-flavor (u{bar u}, d{bar d}, or s{bar s}), Z° 2!b{bar b} events. Clear flavor dependences are observed, and the results are compared with the predictions of three fragmentation models. We have also performed a direct measurement of A{sub s}, the parity-violating coupling of the Z° to strange quarks, by measuring the left-right-forward-backward production asymmetry in polar angle of the tagged s quark. Our preliminary result is A{sub s} = 0.82 ± 0.10(stat.) ± 0.07(syst.).

Download or read book Recent QCD Results from SLD written by and published by . This book was released on 1999 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present selected results on strong interaction physics from the SLD experiment at the SLAC Linear Collider. We report on several new studies of 3- and 4-jet hadronic Z° decays, in which jets are identified as quark, antiquark or gluon. The 3-jet Z° --> b anti-bg rate is sensitive to the b-quark mass; prospects for measuring m{sub b} are discussed. The gluon energy spectrum is measured over the full kinematic range, providing an improved test of QCD and limits on anomalous b anti-bg couplings. The parity violation in Z° --> b anti-bg decays is consistent with electroweak theory plus QCD. New tests of T- and CP-conservation at the bbg vertex are performed. A new measurement of the rate of gluon splitting into b anti-b pairs yields g{sub b anti-b} = 0.0031 " 0.0007 (stat.)" 0.0006 (syst.) (Preliminary). We also present a number of new results on jet fragmentation into identified hadrons. The B hadron energy spectrum is measured over the full kinematic range using a new, inclusive technique, allowing stringent tests of predictions for its shape and a precise measurement of (xB) = 0.714 " 0.005(stat.) " 0.007(syst.) (Preliminary). A detailed study of correlations in rapidity y between pairs of identified pi{sup {+-}}, K{sup {+-}} and p/anti-p confirms that strangeness and baryon number are conserved locally, and shows local charge conservation between meson-baryon and strange-nonstrange pairs. Flavor-dependent long-range correlations are observed for all combinations of these hadron species, yielding new information on leading particle production. The first study of correlations using rapidities signed such that y> 0 corresponds to the quark direction provides additional new insights into fragmentation, including the first direct observation of baryon number ordering along the q anti-q axis.

Download or read book Preliminary Measurement of the Charged Multiplicities in B C and Light Quark Events from Z sup 0 Decays written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book QCD Studies at SLD Identified Hadron Production in Jets of Different Flavors written by and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors have measured the differential cross sections for the production of[pi][sup[+-]], K[sup[+-]], K[sup 0], K[sup*](892), [phi](1020), p and[Lambda] in hadronic Z[sup 0] decays and in subsets of flavor-tagged Z[sup 0][yields] light-flavor (u[bar u], d[bar d], or s[bar s]), Z[sup 0][yields] c[bar c] and Z[sup 0][yields] b[bar b] events. Charged hadrons were identified with the SLD Cherenkov Ring Imaging Detector. A vertex detector was employed to select flavor-enriched samples, and the polarized electron beam from SLC was used to tag quark and antiquark jets. The authors observes a flavor dependence in the hadron fragmentation functions. They also present evidence for leading particle production in hadronic decays of the Z[sup 0] boson to light-flavor jets and a direct measurement of the strangeness suppression factor[gamma][sub s].

Download or read book Measurement of the Polarized Forward backward Asymmetry of S quarks at SLD written by and published by . This book was released on 1998 with total page 133 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents a direct measurement of the parity-violating parameter A{sub s} by analyzing the polarized forward-backward asymmetry of s quarks in e+e− → Z° → s{bar s}. The author has used the data taken at the Stanford Linear Accelerator Center (SLAC), from the SLAC Large Detector (SLD), which records the products of e+e− interactions at a center of mass energy √s = 91.2 GeV at the SLAC Linear Collider (SLC). The unique features of the SLC/SLD experimental apparatus provide interesting tests of the electroweak and the QCD physics. The small, stable SLC beam spot, and the precise tracking capability of the SLD allow the isolation of light flavor events. Charged hadrons are identified over wide momentum range with the Cherenkov Ring Imaging Detector (CRID). High momentum charged kaon, [Lambda]°/{bar {Lambda}}°, and K{sub s}° are used to select Z° → s{bar s} events and to identify the s-quark direction. The averaged polarization was 63.0% in 1993 SLD run and 77.3% in 1994--95 run. The author obtained A{sub s} = 0.86 ± 0.17(stat.) ± 0.10(syst.). This value is consistent with the prediction from the Standard Model and with the values of A{sub b} measurements from SLD and LEP experiments.

Download or read book Measurement of the Z0 S Anti s Coupling at the SLD written by and published by . This book was released on 1999 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation presents a direct measurement of the parity-violating coupling of the Z° to strange quarks, A{sub s}, derived from ee− collision data containing approximately 550,000 hadronic decays of polarized Z° bosons. Data were recorded with the SLC Large Detector (SLD) at the SLAC Linear Collider (SLC) between 1993 and 1998 with an average electron beam polarization of 73% and 74% during the 1993-5 and 1996-8 run periods, respectively. Making use of several unique features of the SLC and SLD, this measurement relies on a new generation particle identification system, the Cherenkov Ring Imaging Detector, to test the Standard Model prediction of universality in the coupling of the Z° to down-type quarks. Polarized Z° --> s anti-s events are tagged by the presence in each event hemisphere of a high-momentum K ", K{sub s}° or Lambda°/ anti-Lambda° identified using particle identification and/or a mass tag. The background from heavy flavor events is suppressed with the CCD-based vertex detector. The event thrust axis is signed with the strangeness of the tagged particle to point in the direction of the initial s quark. The coupling A{sub s} is derived from a maximum likelihood fit to the polar angle distributions of the tagged s quark measured with left- and right-handed electron beams. To reduce the model dependence of the measurement, the background from u anti-u and d anti-d events as well as the analyzing power of the method for s anti-s events are constrained from the data. We obtain A{sub s} = 0.86 " 0.08(stat.) " 0.05(syst.). The result is consistent with both the Standard Model prediction and previous bottom quark coupling mA{sub b}, measurements performed by SLD and LEP, and therefore supports the predicted universality of the Z° to down-type quark couplings.

Download or read book Preliminary Measurement of the Charged Multiplicities in B C and Light Quark Events from Z Decays written by and published by . This book was released on 1996 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book A Preliminary Measurement of the B Quark Fragmentation Function in Hadronic Z sup 0 Decays written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a measurement of the[ital b] quark fragmentation function from a sample of semi-leptonic[bold B] decays collected between 1993 and 1995 in the SLD experiment at SLAC. The energy of each tagged[bold B] hadron was reconstructed using information from the lepton and a partially reconstructed charm decay vertex. A comparison of the scaled energy distribution with several phenomenological models of heavy quark fragmentation was made, using the same model in each case to correct the data. The average scaled energy was found to be[l-angle][chi][sub E][r-angle]= 0.697[+-]0.012([ital stat])[sup+0. 028][sub -0.024] ([ital syst])(preliminary).

Download or read book Recent Tests of QCD at SLD written by and published by . This book was released on 2001 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present selected results on strong interaction physics from the SLD experiment at the SLAC Linear Collider. We report on several new studies of 3- and 4-jet hadronic Z° decays, in which jets are identified as quark, antiquark or gluon. The gluon energy spectrum is measured over the full kinematic range, providing an improved test of QCD and limits on anomalous bbg and bbg couplings. The parity violation in Z° 2!b{bar b}g decays is consistent with electroweak theory plus QCD. New tests of T- and CP-conservation at the bbg vertex are performed. An improved measurement of the rate of gluon splitting into b{bar b} pairs yields g{sub b{bar b}} = 0.00244 ± 0.00059(stat.) ± 0.00034(syst.). We also present a number of new results on jet fragmentation into identified hadrons. The B hadron energy spectrum is measured over the full kinematic range using a new, inclusive technique, allowing stringent tests of predictions for its shape and a precise measurement of x{sub B} = 0.710 ± 0.003(stat.) ± 0.006(syst.) (Preliminary). A detailed study of correlations in rapidity y between pairs of identified [pi]{sup {+-}}, K{sup {+-}} and p/{bar p} confirms that strangeness and baryon number are conserved locally, and shows local charge conservation between meson-baryon and strange-nonstrange pairs. Flavor-dependent long-range correlations are observed for all combinations of these hadron species, yielding new information on leading particle production. The first study of correlations using rapidities signed such that y 0 corresponds to the quark direction provides additional new insights into fragmentation, including the first direct observation of baryon number ordering along the q{bar q} axis.

Download or read book A Preliminary Measurement of the B Quark Fragmentation Function in Hadronic Z Decays written by and published by . This book was released on 1996 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt: We present a measurement of the {ital b} quark fragmentation function from a sample of semi-leptonic {bold B} decays collected between 1993 and 1995 in the SLD experiment at SLAC. The energy of each tagged {bold B} hadron was reconstructed using information from the lepton and a partially reconstructed charm decay vertex. A comparison of the scaled energy distribution with several phenomenological models of heavy quark fragmentation was made, using the same model in each case to correct the data. The average scaled energy was found to be {l_angle}[chi]{sub E}{r_angle} = 0.697±0.012({ital stat}){sup +0. 028}{sub -0.024} ({ital syst})(preliminary).

Download or read book Some Aspects of Quark Fragmentation written by and published by . This book was released on 1984 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The data that the author presents come from the first two years of operation of the High Resolution Spectrometer (HRS) at PEP, and correspond to an integrated luminosity of 106 +- 5 pb−1 (20 pb−1 from the first year and 86 pb−1 from the second year's running). Since the quark-meson transitions may have a particularly simple form at the values of the momentum fraction Z = 2p/sub meson//.sqrt.s, we emphasize this aspect of the data, and show how a sample of e/sup +/e− .-->. (u anti u, d anti d, s anti s) events can be selected. The characteristics of these events are compared to e/sup +/e− .-->. c anti c selected by a D* tag.