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Application of the Principle of Maximum Conformality to Top-Pair Production

Description: A major contribution to the uncertainty of finite-order perturbative QCD predictions is the perceived ambiguity in setting the renormalization scale {mu}{sub r}. For example, by using the conventional way of setting {mu}{sub r} {element_of} [m{sub t}/2, 2m{sub t}], one obtains the total t{bar t} production cross-section {sigma}{sub t{bar t}} with the uncertainty {Delta}{sigma}{sub t{bar t}}/{sigma}{sub t{bar t}} {approx} (+3%/-4%) at the Tevatron and LHC even for the present NNLO level. The Principle of Maximum Conformality (PMC) eliminates the renormalization scale ambiguity in precision tests of Abelian QED and non-Abelian QCD theories. By using the PMC, all nonconformal {l_brace}{beta}{sub i}{r_brace}-terms in the perturbative expansion series are summed into the running coupling constant, and the resulting scale-fixed predictions are independent of the renormalization scheme. The correct scale-displacement between the arguments of different renormalization schemes is automatically set, and the number of active flavors n{sub f} in the {l_brace}{beta}{sub i}{r_brace}-function is correctly determined. The PMC is consistent with the renormalization group property that a physical result is independent of the renormalization scheme and the choice of the initial renormalization scale {mu}{sub r}{sup init}. The PMC scale {mu}{sub r}{sup PMC} is unambiguous at finite order. Any residual dependence on {mu}{sub r}{sup init} for a finite-order calculation will be highly suppressed since the unknown higher-order {l_brace}{beta}{sub i}{r_brace}-terms will be absorbed into the PMC scales higher-order perturbative terms. We find that such renormalization group invariance can be satisfied to high accuracy for {sigma}{sub t{bar t}} at the NNLO level. In this paper we apply PMC scale-setting to predict the t{bar t} cross-section {sigma}{sub t{bar t}} at the Tevatron and LHC colliders. It is found that {sigma}{sub t{bar t}} remains almost unchanged by varying {mu}{sub r}{sup init} within the region of [m{sub t}/4, 4m{sub t}]. The convergence of the expansion series is greatly improved. For the (q{bar ...
Date: May 13, 2013
Creator: Brodsky, Stanley J.; /SLAC; Wu, Xing-Gang & U., /SLAC /Chongqing
Partner: UNT Libraries Government Documents Department

Precision Top-Quark Mass Measurements at CDF

Description: We present a precision measurement of the top-quark mass using the full sample of Tevatron {radical}s = 1.96 TeV proton-antiproton collisions collected by the CDF II detector, corresponding to an integrated luminosity of 8.7 fb{sup -1}. Using a sample of t{bar t} candidate events decaying into the lepton+jets channel, we obtain distributions of the top-quark masses and the invariant mass of two jets from the W boson decays from data. We then compare these distributions to templates derived from signal and background samples to extract the top-quark mass and the energy scale of the calorimeter jets with in situ calibration. The likelihood fit of the templates from signal and background events to the data yields the single most-precise measurement of the top-quark mass, mtop = 172.85 {+-} 0.71 (stat) {+-} 0.85 (syst) GeV/c{sup 2}.
Date: July 1, 2012
Creator: Aaltonen, T.; Alvarez Gonzalez, B.; Amerio, S.; Amidei, D.; Anastassov, A.; Annovi, A. et al.
Partner: UNT Libraries Government Documents Department

Diffractive Dijet Production in $\bar{p}p$ Collisions at $\sqrt{s}=1.96$ TeV

Description: We report on a study of diffractive dijet production in {bar p}p collisions at {radical}s = 1.96 TeV using the CDF II detector at the Fermilab Tevatron {bar p}p collider. A data sample from 310 pb{sup -1} of integrated luminosity collected by triggering on a high transverse energy jet, E{sub T}{sup jet}, in coincidence with a recoil antiproton detected in a Roman pot spectrometer is used to measure the ratio of single-diffractive to inclusive-dijet event rates as a function of x{sup {bar p}} of the interacting parton in the antiproton, the Bjorken-x, x{sub Bj}{sup {bar p}}, and a Q{sup 2} {approx} (E{sub T}{sup jet}){sup 2} in the ranges 10{sup -3} < x{sub Bj}{sup {bar p}} < 10{sup -1} and 10{sup 2} < Q{sup 2} < 10{sup 4} GeV{sup 2}, respectively. Results are presented for the region of {bar p}-momentum-loss fraction 0.03 < {zeta}{sub {bar p}} < 0.09 and a four-momentum transfer squared t{sub {bar p}} > -4 GeV{sup 2}. The t{sub {bar p}} dependence is measured as a function of Q{sup 2} and x{sub Bj}{sup {bar p}} and compared with that of inclusive single diffraction dissociation. We find weak x{sub Bj}{sup bar p}} and Q{sup 2} dependencies in the ratio of single diffractive to inclusive event rates, and no significant Q{sup 2} dependence in the diffractive t{sub {bar p}} distributions.
Date: June 1, 2012
Creator: Aaltonen, T.; Albrow, M.; Alvarez Gonzalez, B.; Amerio, S.; Amidei, D.; Anastassov, A. et al.
Partner: UNT Libraries Government Documents Department

Heavy Flavour results from Tevatron

Description: The CDF and D0 experiments finalize the analysis of their full statistics collected in the p{bar p} collisions at a center-of-mass energy of {radical}s = 1.96 TeV at the Fermilab Tevatron collider. This paper presents several new results on the properties of hadrons containing heavy b- and c-quarks obtained by both collaborations. These results include the search for the rare decays B{sup 0}, B{sub s}{sup 0} {yields} {mu}{sup +}{mu}{sup -} (CDF), the study of CP asymmetry in B{sub s} {yields} J{psi}{phi} decay (CDF, D0), the measurement of the like-sign dimuon charge asymmetry (D0), the measurement of CP asymmetry in D{sup 0} {yields} K{sup +}K{sup -} and D{sup 0} {yields} {pi}{sup +}{pi}{sup -} decays (CDF), and the new measurement of the B{sub s} {yields} D{sub s}{sup (*)+} D{sub s}{sup (*)-} branching fraction (CDF). Both experiments still expect to produce more results on the properties of heavy flavours.
Date: June 1, 2012
Creator: Borissov, G. & U., /Lancaster
Partner: UNT Libraries Government Documents Department

Measurement of the differential cross section $d\sigma/dt$ in elastic $p\bar{p}$ scattering at $\sqrt{s}=1.96$ TeV

Description: We present a measurement of the elastic differential cross section differential cross section d{sigma}(p{bar p}{yields}p{bar p})/dt as a function of the four-momentum-transfer squared t. The data sample corresponds to an integrated luminosity of {approx}31 nb{sup -1} collected with the D0 detector using dedicated Tevatron p{bar p} Collider operating conditions at {radical}s = 1.96 TeV and covers the range 0.26 < |t| < 1.2 GeV{sup 2}. For |t| < 0.6 GeV{sup 2}, d{sigma}/dt is described by an exponential function of the form Ae{sup -b|t|} with a slope parameter b = 16.86 {+-} 0.10 (stat) {+-} 0.20 (syst) GeV{sup -2}. A change in slope is observed at |t| {approx} 0.6 GeV{sup 2}, followed by a more gradual |t| dependence with increasing values of |t|.
Date: June 1, 2012
Creator: Abazov, V.M.; Abazov, V.M.; Abbott, B.; Acharya, B.S.; Adams, M.; Adams, T. et al.
Partner: UNT Libraries Government Documents Department

Searches for New Physics in Top Events at the Tevatron

Description: Recent results of searches for new physics in top events at the Tevatron are presented. In case of CDF three searches are discussed using 6 to 8.7 fb{sup -1} of data, with the latter being the final CDF data sample available for this kind of analysis. CDF carried out a search for Top + jet resonance production, dark matter production in association with single top and boosted tops. No signs of new physics are observed and instead upper limits are derived. D0 used 5.3 fb{sup -1} of data and searched for a narrow resonance in t{bar t} production and a time dependent t{bar t} cross section, which would reveal a violation of Lorentz invariance. However, no signs for deviations from standard model are seen and instead upper limits for non-standard model contributions are calculated.
Date: June 1, 2012
Creator: Jung, A.W.
Partner: UNT Libraries Government Documents Department

Standard Model Higgs Searches at the Tevatron

Description: We present results from the search for a standard model Higgs boson using data corresponding up to 10 fb{sup -1} of proton-antiproton collision data produced by the Fermilab Tevatron at a center-of-mass energy of 1.96 TeV. The data were recorded by the CDF and D0 detectors between March 2001 and September of 2011. A broad excess is observed between 105 < m{sub H} < 145 GeV/c{sup 2} with a global significance of 2.2 standard deviations relative to the background-only hypothesis.
Date: June 1, 2012
Creator: Knoepfel, Kyle J.
Partner: UNT Libraries Government Documents Department

B_c Meson Production Around the Z^0 Peak at a High Luminosity e^+ e^- Collider

Description: Considering the possibility to build an e{sup +}e{sup -} collider at the energies around the Z{sup 0}-boson resonance with a planned luminosity so high as L {proportional_to} 10{sup 34} {approx} 10{sup 36} cm{sup -2}s{sup -1} (super Z-factory), we make a detailed discussion on the (c{bar b})-quarkonium production through e{sup +}e{sup -} {yields} (c{bar b})[n] + b + {bar c} within the framework of non-relativistic QCD. Here [n] stands for the Fock-states |(c{sub b}){sub 1}[{sup 1}S{sub 0}]>, |(c{bar b})8[{sup 1}S{sub 0}]g>, |(c{bar b} ){sub 1}[{sup 3}S{sub 1}]>, |(c{bar b}){sub 8}[{sup 3}S{sub 1}]g>, |(c{bar b}){sub 1}[{sup 1}P{sub 1}]> and |(c{bar b}){sub 1}[{sup 3}P{sub J}]> (with J = (1, 2, 3)) respectively. To simplify the hard-scattering amplitude as much as possible and to derive analytic expressions for the purpose of future events simulation, we adopt the 'improved trace technology' to do our calculation, which deals with the hard scattering amplitude directly at the amplitude level other than the conventional way at the squared-amplitude level. Total cross-section uncertainties caused by the quark masses are predicted by taking m{sub c} = 1.50 {+-} 0.30 GeV and m{sub b} = 4.90 {+-} 0.40 GeV. If all higher (c{bar b})-quarkonium states decay to the ground state B{sub c} (|(c{bar b}){sub 1}[{sup 1}S{sub 0}]>) with 100% efficiency, we obtain {sigma}{sub e{sup +}+e{sup -}{yields}B{sub c}+b+{bar c}} = 5.190{sub -2.419}{sup +6.222} pb, which shows that about 10{sup 5} {approx} 10{sup 7} B{sub c} events per operation year can be accumulated in the super Z-factory. If taking the collider energy runs slightly off the Z{sup 0}-peak, i.e. {radical}S = (1.00 {+-} 0.05)m{sub Z}, the total cross-section shall be lowered by about one-order from its peak value. Such a super Z-factory shall provide another useful platform to study the properties of B{sub c} meson, or even the properties of its excited P-wave ...
Date: May 22, 2012
Creator: Yang, Zhi; U., /Chongqing; Wu, Xing-Gang; /SLAC, /Chongqing U.; Chen, Gu; Liao, Qi-Li et al.
Partner: UNT Libraries Government Documents Department

Recent T980 Crystal Collimation Studies at the Tevatron Exploiting a Pixel Detector System and a Multi-Strip Crystal Array

Description: With the shutdown of the Tevatron, the T-980 crystal collimation experiment at Fermilab has been successfully completed. Results of dedicated beam studies in May 2011 are described in this paper. For these studies, two multi-strip crystals were installed in the vertical goniometer and an O-shaped crystal installed in a horizontal goniometer. A two-plane CMS pixel detector was also installed in order to enhance the experiment with the capability to image the profile of crystal channeled or multiple volume reflected beam. The experiment successfully imaged channeled beam from a crystal for 980-GeV protons for the first time. This new enhanced hardware yielded impressive results. The performance and characterization of the crystals studied have been very reproducible over time and consistent with simulations.
Date: May 15, 2012
Creator: Still, D.; Annala, G. E.; Carrigan, R. A.; Drozhdin, A. I.; Johnson, T. R.; Mokhov, N. V. et al.
Partner: UNT Libraries Government Documents Department

Summary of Fermilab's Recycler Electron Cooler Operation and Studies

Description: Fermilab's Recycler ring was used as a storage ring for accumulation and subsequent manipulations of 8 GeV antiprotons destined for the Tevatron collider. To satisfy these missions, a unique electron cooling system was designed, developed and successfully implemented. The most important features that distinguish the Recycler cooler from other existing electron coolers are its relativistic energy, 4.3 MV combined with 0.1-0.5 A DC beam current, a weak continuous longitudinal magnetic field in the cooling section, 100 G, and lumped focusing elsewhere. With the termination of the Tevatron collider operation, so did the cooler. In this article, we summarize the experience of running this unique machine.
Date: May 15, 2012
Creator: Prost, L. R. & Shemyakin, A.
Partner: UNT Libraries Government Documents Department

Application of the Principle of Maximum Conformality to the Top-Quark Forward-Backward Asymmetry at the Tevatron

Description: The renormalization scale uncertainty can be eliminated by the Principle of Maximum Conformality (PMC) in a systematic scheme-independent way. Applying the PMC for the t{bar t}-pair hadroproduction at the NNLO level, we have found that the total cross-sections {sigma}{sub t{bar t}} at both the Tevatron and LHC remain almost unchanged when taking very disparate initial scales {mu}{sub R}{sup init} equal to m{sub t}, 10 m{sub t}, 20 m{sub t} and {radical}s, which is consistent with renormalization group invariance. As an important new application, we apply PMC scale-setting to study the top-quark forward-backward asymmetry. We observe that the more convergent perturbative series after PMC scale-setting leads to a more accurate top-quark forward-backward asymmetry. The resulting PMC prediction on the asymmetry is also free from the initial renormalization scale-dependence. Because the NLO PMC scale has a dip behavior for the (q{bar q})-channel at small subprocess collision energies, the importance of this channel to the asymmetry is increased. We observe that the asymmetries A{sub FB}{sup t{bar t}} and A{sub FB}{sup p{bar p}} at the Tevatron will be increased by 42% in comparison to the previous estimates obtained by using conventional scale-setting; i.e. we obtain A{sub FB}{sup t{bar t}PMC} {approx_equal} 12.5% and A{sub FB}{sup p{bar p},PMC} {approx_equal} 8.28%. Moreover, we obtain A{sub FB}{sup t{bar t}PMC} (M{sub t{bar t}} > 450 GeV) {approx_equal} 35.0%. These predictions have a 1{sigma}-deviation from the present CDF and D0 measurements; the large discrepancies of the top-quark forward-backward asymmetry between the Standard Model estimate and the CDF and D0 data are thus greatly reduced.
Date: May 14, 2012
Creator: Brodsky, Stanley J.; /SLAC; Wu, Xing-Gang & U., /SLAC /Chongqing
Partner: UNT Libraries Government Documents Department

New Measurements with Photons at the Tevatron

Description: With the recent completion of Run II at the Fermilab Tevatron, the CDF and D0 experiments are publishing results based on challenging measurements that probe quantum chromodynamics (QCD) and are sensitive to next-to-leading-order (NLO) and next-to-next-to-leading-order (NNLO) effects and non-perturbative physics. A superior understanding of parton distribution functions and QCD backgrounds will improve the sensitivity of searches for new phenomena at the LHC and reduce uncertainties in a multitude of future measurements. We present three recent photon analyses from data collected at the Fermilab Tevatron: measurements of the direct photon pair production cross section at CDF and D0, measurements of azimuthal decorrelations and multiple parton interactions in {gamma} + 2 jet and {gamma} + 3 jet events at D0, and an observation of exclusive diphoton production at CDF.
Date: May 1, 2012
Creator: Dittmann, J.R. & U., /Baylor
Partner: UNT Libraries Government Documents Department

Numerical Simulations of Transverse Beam Diffusion Enhancement by the Use of Electron Lens in the Tevatron Collider

Description: Transverse beam diffusion for the Tevatron machine has been calculated using the Lifetrac code. The following effects were included: random noise (representing residual gas scattering, voltage noise in the accelerating cavities) lattice nonlinearities and beam-beam interactions. The time evolution of particle distributions with different initial amplitudes in Hamiltonian action has been simulated for 6 million turns, corresponding to a time of about 2 minutes. For each particle distribution, several cases have been considered: a single beam in storage ring mode, the collider case and the effects of a hollow electron beam collimator. The diffusion coefficient for some representative points in the amplitude space has been calculated by fitting the time evolution of delta-like particle distributions using the diffusion equation, for different machine conditions. The results confirm a strong efficiency of the electron lens as an halo diffusive enhancer, leading to diffusion coefficients which are at least a factor 10K higher than the values obtained for the collision case. This result is confirmed by the Frequency Map Analysis, which shows a clear intensification of resonance lines for particle amplitudes larger than the electron lens inner radius. If compared with past experiments, the simulations successfully reproduce the diffusion coefficients for the beam core, but still present a large discrepancy for halo particles, still under investigation.
Date: May 1, 2012
Creator: Previtali, V.; Stancari, G.; Valishev, A.; /Fermilab; Shatilov, D.N. & /Novosibirsk, IYF
Partner: UNT Libraries Government Documents Department

Recent heavy flavor results from the Tevatron

Description: The CDF and D0 experiments at the Tevatron p{bar p} collider have pioneered and established the role of flavor physics in hadron collisions. A broad program is now at its full maturity. We report on three new results sensitive to physics beyond the standard model, obtained using the whole CDF dataset: a measurement of the difference of CP asymmetries in K{sup +}K{sup -} and {pi}{sup +}{pi}{sup -} decays of D{sup 0} mesons, new bounds on the B{sub s}{sup 0} mixing phase and on the decay width difference of B{sub s}{sup 0} mass-eigenstates, and an update of the summer 2011 search for B{sub (s)}{sup 0} mesons decaying into pairs of muons. Finally, the D0 confirmation of the observation of a new hadron, the {chi}{sub b}(3P) state, is briefly mentioned.
Date: May 1, 2012
Creator: Dorigo, Mirco & /Trieste U. /INFN, Trieste
Partner: UNT Libraries Government Documents Department

Simulation of Hollow Electron Beam Collimation in the Fermilab Tevatron Collider

Description: The concept of augmenting the conventional collimation system of high-energy storage rings with a hollow electron beam was successfully demonstrated in experiments at the Tevatron. A reliable numerical model is required for understanding particle dynamics in the presence of a hollow beam collimator. Several models were developed to describe imperfections of the electron beam profile and alignment. The features of the imperfections are estimated from electron beam profile measurements. Numerical simulations of halo removal rates are compared with experimental data taken at the Tevatron.
Date: May 1, 2012
Creator: Morozov, I.A.; Stancari, G.; Valishev, A.; /Fermilab; Shatilov, D.N. & /Novosibirsk, IYF
Partner: UNT Libraries Government Documents Department

Single Top Production at the Tevatron

Description: We present recent results of single top quark production in the lepton plus jet final state, performed by the CDF and D0 collaborations based on 7.5 and 5.4 fb{sup -1} of p{bar p} collision data collected at {radical}s = 1.96 TeV from the Fermilab Tevatron collider. Multivariate techniques are used to separate the single top signal from the backgrounds. Both collaborations present measurements of the single top quark cross section and the CKM matrix element |V{sub tb}|. A search for anomalous Wtb coupling from D0 is also presented.
Date: May 1, 2012
Creator: Wu, Zhenbin & U., /Baylor
Partner: UNT Libraries Government Documents Department

Single Z Production at the Tevatron

Description: The production of single Z bosons has been studied at Fermilab's Tevatron by the CDF and D0 collaborations. Measurements include the weak mixing angle, vector and axial-vector couplings between Z bosons and light quarks, and angular coefficients in electronic decays which are sensitive to the spin of the gluon. The collaborations have looked for and indication of new physics above the mass scale that can be directly produced at the Tevatron by studying the interference between Z and photon propagators. All measurements are consistent with Standard Model expectations.
Date: May 1, 2012
Creator: Phillips, Thomas J.
Partner: UNT Libraries Government Documents Department

Studies of top quark properties at the Tevatron

Description: An overview of the recent measurements of the top quark properties in proton antiproton collisions at {radical}s = 1.96 TeV is presented. These measurements are based on 5.4-8.7 fb{sup -1} of data collected with the D0 and CDF experiments at the Fermilab Tevatron collider. The top quark mass and width measurements, studies of the spin correlation in top quark pair production, W boson helicity measurement, searches for anomalous top quark couplings and Lorentz invariance violation are discussed.
Date: May 1, 2012
Creator: Shary, Viatcheslav
Partner: UNT Libraries Government Documents Department

Tevatron End-of-Run Beam Physics Experiments

Description: Before the Tevatron Collider Run II ended in September of 2011, a number of specialized beam study periods were dedicated to the experiments on various accelerator physics concepts and effects during the last year of the machine operation. The study topics included collimation with bent crystals and hollow electron beams, diffusion measurements and various aspects of beam-beam interactions. In this report we concentrate on the subject of beam-beam interactions, summarizing the results of beam experiments. The covered topics include offset collisions, coherent beam stability, effect of the bunch-length-to-beta-function ratio, and operation of AC dipole with colliding beams.
Date: May 1, 2012
Creator: Valishev, A.; Gu, X.; Miyamoto, R.; White, S.; Schmidt, F. & Qiang, J.
Partner: UNT Libraries Government Documents Department

$W$ boson polarization measurement in the $t\bar{t}$ dilepton channel using the CDF II Detector

Description: We present a measurement of W boson polarization in top-quark decays in t{bar t} events with decays to dilepton final states using 5.1 fb{sup -1} integrated luminosity in p{bar p} collisions collected by the CDF II detector at the Tevatron. A simultaneous measurement of the fractions of longitudinal (f{sub 0}) and right-handed (f{sub +}) W bosons yields the results f{sub 0} = 0.71{sub -0.17}{sup +0.18}(stat) {+-} 0.06(syst) and f{sub +} = -0.07 {+-} 0.09(stat) {+-} 0.03(syst). Combining this measurement with our previous result based on single lepton final states, we obtain f{sub 0} = 0.84 {+-} 0.09(stat) {+-} 0.05(syst) and f{sub +} = -0.16 {+-} 0.05(stat) {+-} 0.04(syst). The results are consistent with standard model expectation.
Date: May 1, 2012
Creator: Aaltonen, T.; Alvarez Gonzalez, B.; Amerio, S.; Amidei, D.; Anastassov, A.; Annovi, A. et al.
Partner: UNT Libraries Government Documents Department

Eliminating the Renormalization Scale Ambiguity for Top-Pair Production Using the Principle of Maximum Conformality

Description: The uncertainty in setting the renormalization scale in finite-order perturbative QCD predictions using standard methods substantially reduces the precision of tests of the Standard Model in collider experiments. It is conventional to choose a typical momentum transfer of the process as the renormalization scale and take an arbitrary range to estimate the uncertainty in the QCD prediction. However, predictions using this procedure depend on the choice of renormalization scheme, leave a non-convergent renormalon perturbative series, and moreover, one obtains incorrect results when applied to QED processes. In contrast, if one fixes the renormalization scale using the Principle of Maximum Conformality (PMC), all non-conformal {l_brace}{beta}{sub i}{r_brace}-terms in the perturbative expansion series are summed into the running coupling, and one obtains a unique, scale-fixed, scheme-independent prediction at any finite order. The PMC renormalization scale {mu}{sub R}{sup PMC} and the resulting finite-order PMC prediction are both to high accuracy independent of choice of the initial renormalization scale {mu}{sub R}{sup init}, consistent with renormalization group invariance. Moreover, after PMC scale-setting, the n!-growth of the pQCD expansion is eliminated. Even the residual scale-dependence at fixed order due to unknown higher-order {l_brace}{beta}{sub i}{r_brace}-terms is substantially suppressed. As an application, we apply the PMC procedure to obtain NNLO predictions for the t{bar t}-pair hadroproduction cross-section at the Tevatron and LHC colliders. There are no renormalization scale or scheme uncertainties, thus greatly improving the precision of the QCD prediction. The PMC prediction for {sigma}{sub t{bar t}} is larger in magnitude in comparison with the conventional scale-setting method, and it agrees well with the present Tevatron and LHC data. We also verify that the initial scale-independence of the PMC prediction is satisfied to high accuracy at the NNLO level: the total cross-section remains almost unchanged even when taking very disparate initial scales {mu}{sub R}{sup init} equal to m{sub t}, ...
Date: April 2, 2012
Creator: Brodsky, Stanley J.; /SLAC; Wu, Xing-Gang & U., /Chongqing
Partner: UNT Libraries Government Documents Department

2012 Update of the Combination of CDF and D0 Results for the Mass of the W Boson

Description: We summarize and combine the results on the direct measurements of the mass of the W boson in data collected by the Tevatron experiments CDF and D0 at Fermilab. Earlier results from CDF Run-0 (1988-1989), D0 and CDF Run-I (1992-1995) and D0 results from 1 fb{sup -1} (2002-2006) of Run-II data are now combined with two new, high statistics Run-II measurements: a CDF measurement in both electron and muon channels using 2.2 fb{sup -1} of integrated luminosity collected between 2002 and 2007, and a D0 measurement in the electron channel using 4.3 fb{sup -1} collected between 2006 and 2009. As in previous combinations, the results are corrected for inconsistencies in parton distribution functions and assumptions about electroweak parameters used in the different analyses. The resulting Tevatron average for the mass of the W boson is M{sub W} = 80,387 {+-} 16 MeV and a new world average including data from LEP II is M{sub W} = 80,385 {+-} 15 MeV.
Date: April 1, 2012
Creator: Tevatron Electroweak Working Group,
Partner: UNT Libraries Government Documents Department

Measurement of $B_s^0 \to D_s^{(*)+} D_s^{(*)-}$ Branching Ratios

Description: The decays B{sub s}{sup 0} {yields} D{sub s}{sup (*)+}D{sub s}{sup (*)-}s are reconstructed in a data sample corresponding to an integrated luminosity of 6.8 fb{sup -1} collected by the CDF II detector at the Tevatron p{bar p} collider. All decay modes are observed with a significance of more than 10 {sigma}, and we measure the B{sub s}{sup 0} production rate times B{sub s}{sup 0} {yields} D{sub s}{sup (*)+} D{sub s}{sup (*)-} branching ratios relative to the normalization mode B{sup 0} {yields} D{sub s}{sup +}d{sup -} to be 0.183 {+-} 0.021 {+-} 0.017 for B{sub s}{sup 0} {yields} D{sub s}{sup +}D{sub s}{sup -}, 0.424 {+-} 0.046 {+-} 0.035 for B{sub s}{sup 0} {yields} D{sub s}{sup {+-}} D{sub s}{sup {-+}}, 0.654 {+-} 0.072 {+-} 0.065 for B{sub s}{sup 0} {yields} D{sub s}{sup *+} D{sub s}{sup *-}, and 1.261 {+-} 0.095 {+-} 0.112 for the inclusive decay B{sub s}{sup 0} {yields} D{sub s}{sup (*)+}D{sub s}{sup (*)-}, where the uncertainties are statistical and systematic. These results are the most precise single measurements to date and provide important constraints for indirect searches for non-standard model physics in B{sub s}{sup 0} mixing.
Date: April 1, 2012
Creator: Aaltonen, T.; Alvarez Gonzalez, B.; Amerio, S.; Amidei, D.; Anastassov, A.; Annovi, A. et al.
Partner: UNT Libraries Government Documents Department

Measurements of the top quark mass at the Tevatron

Description: The mass of the top quark (m{sub top}) is a fundamental parameter of the standard model (SM). Currently, its most precise measurements are performed by the CDF and D0 collaborations at the Fermilab Tevatron p{bar p} collider at a centre-of-mass energy of {radical}s = 1.96 TeV. We review the most recent of those measurements, performed on data samples of up to 8.7 fb{sup -1} of integrated luminosity. The Tevatron combination using up to 5.8 fb{sup -1} of data results in a preliminary world average top quark mass of m{sub top} = 173.2 {+-} 0.9 GeV. This corresponds to a relative precision of about 0.54%. We conclude with an outlook of anticipated precision the final measurement of m{sub top} at the Tevatron.
Date: April 1, 2012
Creator: Brandt, Oleg & /Gottingen U., II. Phys. Inst.
Partner: UNT Libraries Government Documents Department