اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدIndirect measurement of $sin^2theta_W$ (M_W) using e+e- pairs in the Z-boson region with $pbar{p}$ collisions at a center-of-momentum energy of 1.96 TeV
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Drell-Yan lepton pairs are produced in the process $pbar{p} rightarrow e^+e^- + X$ through an intermediate $gamma^*/Z$ boson. The lepton angular distributions are used to provide information on the electroweak-mixing parameter $sin^2theta_W$ via its observable effective-leptonic $sin^2theta_W$, or $sin^2theta^{lept}_{eff}$. A new method to infer $sin^2theta_W$, or equivalently, the W-boson mass M_W in the on-shell scheme, is developed and tested using a previous CDF Run II measurement of angular distributions from electron pairs in a sample corresponding to 2.1 fb-1 of integrated luminosity from $pbar{p}$ collisions at a center-of-momentum energy of 1.96 TeV. The value of $sin^2theta^{lept}_{eff}$ is found to be 0.2328 +- 0.0010. Within a specified context of the standard model, this results in $sin^2theta_W$ = 0.2246 +- 0.0009 which corresponds to a W-boson mass of 80.297 +- 0.048 GeV/c^2, in agreement with previous determinations in electron-position collisions and at the Tevatron collider.
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Drell-Yan lepton pairs are produced in the process $pbar{p} rightarrow mu^+mu^- + X$ through an intermediate $gamma^*/Z$ boson. The forward-backward asymmetry in the polar-angle distribution of the $mu^-$ as a function of the invariant mass of the $m
u^+mu^-$ pair is used to obtain the effective leptonic determination $sin^2 theta^{lept}_{eff}$ of the electroweak-mixing parameter $sin^2 theta_W$, from which the value of $sin^2 theta_W$ is derived assuming the standard model. The measurement sample, recorded by the Collider Detector at Fermilab (CDF), corresponds to 9.2 fb-1 of integrated luminosity from $pbar{p}$ collisions at a center-of-momentum energy of 1.96 TeV, and is the full CDF Run II data set. The value of $sin^2 theta^{lept}_{eff}$ is found to be 0.2315 +- 0.0010, where statistical and systematic uncertainties are combined in quadrature. When interpreted within the context of the standard model using the on-shell renormalization scheme, where $sin^2 theta_W = 1 - M_W^2/M_Z^2$, the measurement yields $sin^2 theta_W$ = 0.2233 +- 0.0009, or equivalently a W-boson mass of 80.365 +- 0.047 GeV/c^2. The value of the W-boson mass is in agreement with previous determinations in electron-positron collisions and at the Tevatron collider.
At the Fermilab Tevatron proton-antiproton ($pbar{p}$) collider, Drell-Yan lepton pairs are produced in the process $p bar{p} rightarrow e^+e^- + X$ through an intermediate $gamma^*/Z$ boson. The forward-backward asymmetry in the polar-angle distribu
tion of the $e^-$ as a function of the $e^+e^-$-pair mass is used to obtain $sin^2theta^{rm lept}_{rm eff}$, the effective leptonic determination of the electroweak-mixing parameter $sin^2theta_W$. The measurement sample, recorded by the Collider Detector at Fermilab (CDF), corresponds to 9.4~fb$^{-1}$ of integrated luminosity from $pbar{p}$ collisions at a center-of-momentum energy of 1.96 TeV, and is the full CDF Run II data set. The value of $sin^2theta^{rm lept}_{rm eff}$ is found to be $0.23248 pm 0.00053$. The combination with the previous CDF measurement based on $mu^+mu^-$ pairs yields $sin^2theta^{rm lept}_{rm eff} = 0.23221 pm 0.00046$. This result, when interpreted within the specified context of the standard model assuming $sin^2 theta_W = 1 - M_W^2/M_Z^2$ and that the $W$- and $Z$-boson masses are on-shell, yields $sin^2theta_W = 0.22400 pm 0.00045$, or equivalently a $W$-boson mass of $80.328 pm 0.024 ;{rm GeV}/c^2$.
The transverse momentum cross section of $e^+e^-$ pairs in the $Z$-boson mass region of 66-116 GeV/$c^2$ is precisely measured using Run II data corresponding to 2.1 fb$^{-1}$ of integrated luminosity recorded by the Collider Detector at Fermilab. Th
e cross section is compared with quantum chromodynamic calculations. One is a fixed-order perturbative calculation at ${cal O}(alpha_s^2)$, and the other combines perturbative predictions at high transverse momentum with the gluon resummation formalism at low transverse momentum. Comparisons of the measurement with calculations show reasonable agreement. The measurement is of sufficient precision to allow refinements in the understanding of the transverse momentum distribution.
A measurement of the inclusive bottom jet cross section is presented for events containing a $Z$ boson in $pbar{p}$ collisions at $sqrt{s}=1.96$ TeV using the Collider Detector at Fermilab. $Z$ bosons are identified in their electron and muon decay m
odes, and $b$ jets with $E_T>20$ GeV and $|eta|<1.5$ are identified by reconstructing a secondary decay vertex. The measurement is based on an integrated luminosity of about 330 ${rm pb}^{-1}$. A cross section times branching ratio of $sigma (Z+b {rm jets}) times {cal B}(Z to ell^+ ell^-)= 0.93 pm 0.36$ pb is found, where ${cal B}(Zto ell^+ ell^-)$ is the branching ratio of the $Z$ boson or $gamma^*$ into a single flavor dilepton pair ($e$ or $mu$) in the mass range between 66 and 116 GeV$/c^2$. The ratio of $b$ jets to the total number of jets of any flavor in the $Z$ sample, within the same kinematic range as the $b$ jets, is $2.36 pm 0.92%$. Here, the uncertainties are the quadratic sum of statistical and systematic uncertainties. Predictions made with NLO QCD agree, within experimental and theoretical uncertainties, with these measurements.
A measurement of the $bjet$ production cross section is presented for events containing a $Z$ boson produced in $pbar{p}$ collisions at $sqrt{s}=1.96$ TeV, using data corresponding to an integrated luminosity of 2 fb$^{-1}$ collected by the CDF II de
tector at the Tevatron. $Z$ bosons are selected in the electron and muon decay modes. Jets are considered with transverse energy $E_T>20$ GeV and pseudorapidity $|eta|<1.5$ and are identified as $bjets$ using a secondary vertex algorithm. The ratio of the integrated $Z+bjet$ cross section to the inclusive $Z$ production cross section is measured to be $3.32 pm 0.53 {rm (stat.)} pm 0.42 {rm (syst.)}times 10^{-3}$. This ratio is also measured differentially in jet $E_T$, jet $eta$, $Z$-boson transverse momentum, number of jets, and number of $bjets$. The predictions from leading order Monte Carlo generators and next-to-leading-order QCD calculations are found to be consistent with the measurements within experimental and theoretical uncertainties.
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