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Fragmentation is the process by which quarks and gluons organize themselves into hadrons. The fragmentation properties of the bottom quark cannot be predicted from fundamental principles and hence must be determined empirically. We investigate one such property, namely the flavour dependence of the fragmentation process for bottom quarks produced in 1.8-TeV proton-antiproton collisions. This flavour dependence is investigated by determining the 'B'-hadron production ratios. We use a sample of pp data corresponding to an integrated luminosity of 110 pb-1 and reconstruct the following semileptonic 'B'-hadron decays into electrons and charmed hadrons: B+[right arrow]e+neD 0X,hsp sp="0.265"B0[right arrow]e+n eD*-X , B0[right arrow]e+neD- X,hsp sp="0.265"B0s[right arrow]e +neD-s X and L0b [right arrow]e+neL- cX . With these data, we measure the ratios of fragmentation fractions fd/fuvmk id="vm1"=88± 21%, fs/fu+fdvmkr rid="vm1"= 21.5±7.1%hsp sp="0.265"and fbaryon/fu+fd vmkr rid="vm1"=12.0±4.2%. Assuming that these four hadrons saturate production of weakly-decaying ' B' hadrons, that is, that fu+fd+fs+fbaryon 1 , we determine fuvmk id="vm1"=39.8±5.4 %, fdvmkr rid="vm1"=35.2±4.8 %, fsvmkr rid="vm1"=16.1±4.5 %hsp sp="0.265"and fbaryonvmkr rid="vm1"=9.0± 2.9%. These results represent the first measurement of all four 'b'-quark fragmentation fractions in a single experiment. These fractions are in agreement both with previous phenomenological interpretations and with other experimental measurements.
A novel technique for measuring the mass of the top quark that uses only the kinematic properties of its charged decay products is presented. Top quark pair events with final states with one or two charged leptons and hadronic jets are selected from the data set of 8 TeV proton-proton collisions, corresponding to an integrated luminosity of 19.7 fb-1. By reconstructing secondary vertices inside the selected jets and computing the invariant mass of the system formed by the secondary vertex and an isolated lepton, an observable is constructed that is sensitive to the top quark mass that is expected to be robust against the energy scale of hadronic jets. The main theoretical systematic uncertainties, concerning the modeling of the fragmentation and hadronization of b quarks and the reconstruction of secondary vertices from the decays of b hadrons, are studied. A top quark mass of 173.68±0.20(stat)-0.97+1.58(syst) GeV is measured. Furthermore, the overall systematic uncertainty is dominated by the uncertainty in the b quark fragmentation and the modeling of kinematic properties of the top quark.
This thesis describes the first Run II measurement of b quark fragmentation into {bar B}{sup 0}, B{sup -}, and {bar B}{sub s}{sup 0} mesons and {Lambda}{sub b}{sup 0} baryons using semileptonic B decays. The result is based on 360 pb{sup -1} of data collected with the CDF detector in p{bar p} collisions at {radical}s = 1,960 GeV at the Tevatron Collider at Fermilab. The fragmentation fractions are measured for an effective {bar B} hadron p{sub T} threshold of 7 GeV/c to be f{sub u}/f{sub d} = 1.054 {+-} 0.018(stat){sub -0.045}{sup +0.025}(syst) {+-} 0.058(BR), f{sub s}/(f{sub u} + f{sub d}) = 0.160 {+-} 0.005(stat){sub -0.010}{sup +0.011}(syst){sub -0.034}{sup +0.057}(BR), and f{sub {Lambda}{sub b}}/(f{sub u} + f{sub d}) = 0.281 {+-} 0.012(stat){sub -0.056}{sup +0.058}(syst){sub -0.086}{sup +0.128}(BR). f{sub s}/(f{sub u} + f{sub d}) agrees both with previous CDF measurements and the world averages, dominated by the LEP measurements, with {approx} 1{sigma}. However, f{sub {Lambda}{sub b}}/(f{sub u} + f{sub d}) is approximately twice the value which has been measured at LEP and in CDF Run I and disagrees with the LEP results by approximately 2 {sigma}.
With an integrated luminosity of 2.47 fb-1 recorded by the ATLAS experiment at the LHC, the exclusive decays B0s→J/?? and B0d→J/?K*0 of B mesons produced in pp collisions at √s=7 TeV are used to determine the ratio of fragmentation fractions fs/fd. From the observed B0s→J/?? and B0d→J/?K*0 yields, the quantity (fs/fd)[B(B0s→J/??)/B(B0d→J/?K*0)] is measured to be 0.199±0.004(stat)±0.008(syst). Using a recent theory prediction for [B(B0s→J/??)/B(B0d→J/?K*0)] yields (fs/fd)=0.240±0.004(stat)±0.010(syst)±0.017(th). As a result, it is based on a new approach that provides a significant improvement of the world average.
We report the first measurement of the top quark mass using the decay length technique in p{bar p} collisions at a center-of-mass energy of 1.96 TeV. This technique uses the measured flight distance of the b hadron to infer the mass of the top quark in lepton plus jets events with missing transverse energy. It relies solely on tracking and avoids the jet energy scale uncertainty that is common to all other methods used so far. We apply our novel method to a 695 pb−1 data sample recorded by the CDF II detector at Fermilab and extract a measurement of m{sub t} = 180.7{sub -13.4}{sup +15.5}(stat.) ± 8.6 (syst.) GeV/c2. While the uncertainty of this result is larger than that of other measurements, the dominant uncertainties in the decay length technique are uncorrelated with those in other methods. This result can help reduce the overall uncertainty when combined with other existing measurements of the top quark mass.
We report the first measurement of the top quark mass using the decay length technique in p{bar p} collisions at a center-of-mass energy of 1.96 TeV. This technique uses the measured flight distance of the b hadron to infer the mass of the top quark in lepton plus jets events with missing transverse energy. It relies solely on tracking and avoids the jet energy scale uncertainty that is common to all other methods used so far. We apply our novel method to a 695 pb−1 data sample recorded by the CDF II detector at Fermilab and extract a measurement of m{sub t} = 180.7{sub -13.4}{sup +15.5}(stat.) ± 8.6 (syst.) GeV/c2. While the uncertainty of this result is larger than that of other measurements, the dominant uncertainties in the decay length technique are uncorrelated with those in other methods. This result can help reduce the overall uncertainty when combined with other existing measurements of the top quark mass.
^ 74 GeV and |y| 2.4; the b jets must contain a B hadron. The measurement has significant statistics up to p T ∼ O(TeV). Advanced methods of unfolding are performed to extract the signal. It is found that fixed-order calculations with underlying event describe the measurement well.