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Observation of the Decay B+-(c) ---> J/psi pi+- and Measurement of the B+-(c) Mass

Description: The B{sub c}{sup {+-}} meson is observed through the decay B{sub c}{sup {+-}} {yields} J/{psi} {pi}{sup {+-}}, in data corresponding to an integrated luminosity of 2.4 fb{sup -1} recorded by the CDF II detector at the Fermilab Tevatron. A signal of 108 {+-} 15 candidates is observed, with a significance that exceeds 8{sigma}. The mass of the B{sub c}{sup {+-}} meson is measured to be 6275.6 {+-} 2.9(stat.) {+-} 2.5(syst.) MeV/c{sup 2}.
Date: December 1, 2007
Creator: Aaltonen, T.
Partner: UNT Libraries Government Documents Department

Measurement of Lifetime and Decay-Width Difference in B0s -> J/psi phi Decays

Description: The authors measure the mean lifetime, {tau} = 2/({Lambda}{sub L} + {Lambda}{sub H}), and the decay-width difference, {Delta}{Lambda} = {Lambda}{sub L} - {Lambda}{sub H}, of the light and heavy mass eigenstates of the B{sub s}{sup 0} meson, B{sub sL}{sup 0} and B{sub sH}{sup 0}, in B{sub s}{sup 0} {yields} J/{psi}{phi} decays using 1.7 fb{sup -1} of data collected with the CDF II detector at the Fermilab Tevatron p{bar p} collider. Assuming CP conservation, a good approximation for the B{sub s}{sup 0} system in the standard model, they obtain {Delta}{Lambda} = 0.076{sub -0.063}{sup +0.059}(stat.) {+-} 0.006(syst.) ps{sup -1} and {tau} = 1.52 {+-} 0.04(stat.) {+-} 0.02(syst.) ps, the most precise measurements to date. The constraints on the weak phase and {Delta}{Lambda} are consistent with CP conservation.
Date: December 1, 2007
Creator: Aaltonen, : T.
Partner: UNT Libraries Government Documents Department

Measurement of the $\ttbar$ Production Cross Section in 2 fb$^{-1}$ of $\ppbar$ Collisions at $\sqrt{s}=1.96$ TeV Using Lepton Plus Jets Events with Soft Muon b-Tagging

Description: We present a measurement of the t{bar t} production cross section in p{bar p} collisions at {radical}s = 1.96 TeV using events containing a high transverse momentum electron or muon, three or more jets, and missing transverse energy. Events consistent with t{bar t} decay are found by identifying jets containing candidate heavy-flavor semileptonic decays to muons. The measurement uses a CDF Run II data sample corresponding to 2 fb{sup -1} of integrated luminosity. Based on 248 candidate events with three or more jets and an expected background of 79.5 {+-} 5.3 events, we measure a production cross section of 9.1 {+-} 1.6 pb.
Date: January 1, 2009
Creator: Aaltonen, T.
Partner: UNT Libraries Government Documents Department

Search for the Flavor Changing Neutral Current Decay t $\to Zq$ in $p \bar{p}$ Collisions at $\sqrt{s}=1.96$

Description: We report a search for the flavor changing neutral current (FCNC) decay of the top quark t {yields} Zq (q = u, c) in p{bar p} collisions at {radical}s = 1.96 TeV using a data sample corresponding to an integrated luminosity of 1.9 fb{sup -1} collected by the CDF II detector. This decay is strongly suppressed in the standard model (SM) and a signal at the Tevatron would be an indication of physics beyond the SM. Using Z+ {ge} 4 jet final state candidate events, both with and without an identified bottom quark jet, we discriminate signal from background by exploring kinematic constraints present in FCNC events and obtain an upper limit of {Beta}(t {yields} Zq) < 3.7% at 95% C.L.
Date: May 1, 2008
Creator: Aaltonen, : T.
Partner: UNT Libraries Government Documents Department

Search for doubly charged Higgs bosons with lepton-flavour-violating decays involving tau leptons

Description: The authors search for pair production of doubly charged Higgs particles (H{sup {+-}{+-}}) followed by decays into electron-tau (e{tau}) and muon-tau ({mu}{tau}) pairs using a data set corresponding to an integrated luminosity of 350 pb{sup -1} collected from {bar p}p collisions at {radical}s = 1.96 TeV by the CDF II experiment. They search separately for cases where three or four final-state leptons are detected, and then combine the results into limits for each exclusive flavor decay mode of the H{sup {+-}{+-}}. Assuming 100% branching ratios of the H{sup {+-}{+-}} to left-handed e{tau} ({mu}{tau}) pairs, they set an H{sup {+-}{+-}} lower mass limit of 114 (112) GeV/c{sup 2} at the 95% confidence level (C.L.).
Date: December 1, 2007
Creator: Aaltonen, T.
Partner: UNT Libraries Government Documents Department

Search for Standard Model Higgs Bosons Produced in Association with W Bosons

Description: The authors report on the results of a search for standard model Higgs bosons produced in association with W bosons from p{bar p} collisions at {radical}s = 1.96 TeV. The search uses a data sample corresponding to approximately 1 fb{sup -1} of integrated luminosity. Events consistent with the W {yields} {ell}{nu} and H {yields} b{bar b} signature are selected by triggering on a high-p{sub T} electron or muon candidate and tagging one or two of the jet candidates as having originated from b quarks. A neural network filter rejects a fraction of tagged charm and light flavor jets, increasing the b-jet purity in the sample and thereby reducing the background to Higgs boson production. They observe no excess {ell}{nu}b{bar b} production beyond the background expectation, and they set 95% confidence level upper limits on the production cross section times branching fraction {sigma}(p{bar p} {yields} WH) {center_dot} Br(H {yields} b{bar b}) ranging from 3.9 to 1.3 pb, for specific Higgs boson mass hypotheses in the range 110 to 150 GeV/c{sup 2}, respectively.
Date: October 1, 2007
Creator: Aaltonen, T.
Partner: UNT Libraries Government Documents Department

Measurement of the cross section for W-boson production in association with jets in ppbar collisions at s**(1/2) = 1.96-TeV

Description: We present a measurement of the cross section for W-boson production in association with jets in p{bar p} collisions at {radical}s = 1.96 TeV. The analysis uses a data sample corresponding to an integrated luminosity of 320 pb{sup -1} collected with the CDF II detector. W bosons are identified in their electron decay channel and jets are reconstructed using a cone algorithm. For each W + {ge} n-jet sample (n = 1-4) we measure {sigma}(p{bar p} {yields} W + {ge} n-jet) x {Beta}(W {yields} e{nu}) with respect to the transverse energy E{sub T} of the nth-highest E{sub T} jet above 20 GeV, for a restricted W {yields} e{nu} decay phase space. The cross sections, corrected for all detector effects, can be directly compared to particle level W + jet(s) predictions. We present here comparisons to leading order and next-to-leading order predictions.
Date: November 1, 2007
Creator: Aaltonen, T.
Partner: UNT Libraries Government Documents Department

Measurement of b-jet Shapes in Inclusive Jet Production in p anti-p Collisions at s**(1/2) = 1.96-TeV

Description: We present a measurement of the shapes of b-jets using 300 pb{sup -1} of data obtained with the upgraded Collider Detector at Fermilab (CDF II) in p{bar p} collisions at center of mass energy {radical}s = 1.96 TeV. This measurement covers a wide transverse momentum range, from 52 to 300 GeV/c. Samples of heavy-flavor enhanced jets together with inclusive jets are used to extract the average shapes of b-jets. The b-jets are expected to be broader than inclusive jets. Moreover, b-jets containing a single b-quark are expected to be narrower than those containing a b{bar b} pair from gluon splitting. The measured b-jet shapes are found to be significantly broader than expected from the pythia and HERWIG Monte Carlo simulations. This effect may arise from an underestimation of the fraction of b-jets originating from gluon splitting in these simulations.
Date: June 1, 2008
Creator: Aaltonen, T.
Partner: UNT Libraries Government Documents Department

Measurement of Resonance Parameters of Orbitally Excited Narrow B^0 Mesons

Description: The authors report a measurement of resonance parameters of the orbitally excited (L = 1) narrow B{sup 0} mesons in decays to B{sup (*)+}{pi}{sup -} using 1.7 fb{sup -1} of data collected by the CDF II detector at the Fermilab Tevatron. The mass and width of the B*{sub 2}{sup 0} state are measured to be m(B*{sub 2}{sup 0}) = 5740.2{sub -1.8}{sup +1.7}(stat.){sub -0.8}{sup +0.9}(syst.) MeV/c{sup 2} and {Lambda}(B*{sub 2}{sup 0}) = 22.7{sub -3.2}{sup +3.8}(stat.){sub -10.2}{sup +3.2}(syst.) MeV/c{sub 2}. The mass difference between the B*{sub 2}{sup 0} and B{sub 1}{sup 0} states is measured to be 14.9{sub -2.5}{sup +2.2}(stat.){sub -1.4}{sup +1.2}(syst.) MeV/c{sup 2}, resulting in a B{sub 1}{sup 0} mass of 5725.3{sub -2.2}{sup +1.6}(stat.){sub -1.5}{sup +1.4}(syst.) MeV/c{sup 2}. This is currently the most precise measurement of the masses of these states and the first measurement of the B*{sub 2}{sup 0} width.
Date: September 1, 2008
Creator: Aaltonen, : T.
Partner: UNT Libraries Government Documents Department

Search for Bs --> mu+mu- and Bd --> mu+mu- Decays with 2fb-1 of ppbar Collisions

Description: The authors have performed a search for B{sub s}{sup 0} {yields} {mu}{sup +}{mu}{sup -} and B{sup 0} {yields} {mu}{sup +}{mu}{sup -} decays in p{bar p} collisions at {radical}s = 1.96 TeV using 2 fb{sup -1} of integrated luminosity collected by the CDF II detector at the Fermilab Tevatron Collider. The observed number of B{sub s}{sup 0} and B{sup 0} candidates is consistent with background expectations. The resulting upper limits on the branching fractions are {Beta}(B{sub s}{sup 0} {yields} {mu}{sup +}{mu}{sup -}) < 5.8 x 10{sup -8} and {Beta}(B{sup 0} {yields} {mu}{sup +}{mu}{sup -}) < 1.8 x 10{sup -8} at 95% C.L.
Date: December 1, 2007
Creator: CDF Collaboration
Partner: UNT Libraries Government Documents Department

First Measurement of the Fraction of Top Quark Pair Production Through Gluon-Gluon Fusion

Description: We present the first measurement of {sigma}(gG {yields} t{bar t})/{sigma}(p{bar p} {yields} t{bar t}). We use 0.96 fb{sup -1} of {radical}s = 1.96 TeV p{bar p} collision data recorded with the CDF II detector at Fermilab. We identify the candidate t{bar t} events with a high-energy charged lepton, a neutrino candidate, and four or more jets with at least one identified as originating from a b quark. Using charged particles with low transverse momentum in t{bar t} events, we find {sigma}(gg {yields} t{bar t})/{sigma}(p{bar p} {yields} t{bar t}) = 0.07 {+-} 0.14(stat) {+-} 0.07(syst), in agreement with the standard model NLO prediction of 0.15 {+-} 0.05.
Date: December 1, 2007
Creator: CDF Collaboration
Partner: UNT Libraries Government Documents Department

Search for New Heavy Particles Decaying to Z0 Z0 to llll, lljj in p pbar Collisions at Sqrt(s) = 1.96 TeV

Description: We report on a search for anomalous production of Z pairs through a massive resonance decay in data corresponding to 2.5-2.9 fb{sup -1} of integrated luminosity in p{bar p} collisions at {radical}s = 1.96 TeV using the CDF II detector at the Fermilab Tevatron. This analysis, with more data and channels where the Z bosons decay to muons or jets, supersedes the 1.1 fb{sup -1} four-electron channel result previously published by CDF. In order to maintain high efficiency for muons, we use a new forward tracking algorithm and muon identification requirements optimized for these high signal-to-background channels. Predicting the dominant backgrounds in each channel entirely from sideband data samples, we observe four-body invariant mass spectra above 300 GeV/c{sup 2} that are consistent with background. We set limits using the acceptance for a massive graviton resonance that are 7-20 times stronger than the previously published direct limits on resonant ZZ production.
Date: February 1, 2011
Creator: Aaltonen, T.
Partner: UNT Libraries Government Documents Department

Studying the Underlying Event in Drell-Yan and High Transverse Momentum Jet Production at the Tevatron

Description: We study the underlying event in proton-antiproton collisions by examining the behavior of charged particles (transverse momentum p{sub T} > 0.5 GeV/c, pseudorapidity |{eta}| < 1) produced in association with large transverse momentum jets ({approx}2.2 fb{sup -1}) or with Drell-Yan lepton-pairs ({approx}2.7 fb{sup -1}) in the Z-boson mass region (70 < M(pair) < 110 GeV/c{sup 2}) as measured by CDF at 1.96 TeV center-of-mass energy. We use the direction of the lepton-pair (in Drell-Yan production) or the leading jet (in high-p{sub T} jet production) in each event to define three regions of {eta}-{phi} space; toward, away, and transverse, where {phi} is the azimuthal scattering angle. For Drell-Yan production (excluding the leptons) both the toward and transverse regions are very sensitive to the underlying event. In high-p{sub T} jet production the transverse region is very sensitive to the underlying event and is separated into a MAX and MIN transverse region, which helps separate the hard component (initial and final-state radiation) from the beam-beam remnant and multiple parton interaction components of the scattering. The data are corrected to the particle level to remove detector effects and are then compared with several QCD Monte-Carlo models. The goal of this analysis is to provide data that can be used to test and improve the QCD Monte-Carlo models of the underlying event that are used to simulate hadron-hadron collisions.
Date: March 1, 2010
Creator: ,; Aaltonen, T.; Adelman, J.; Gonzalez, B.Alvarez; Amerio, S.; Amidei, D. et al.
Partner: UNT Libraries Government Documents Department

Measurement of the Top Quark Mass in the Lepton+Jets Channel Using the Lepton Transverse Momentum

Description: This letter reports a measurement of the top quark mass, M{sub top}, in data from p{bar p} collisions at {radical}s = 1.96 TeV corresponding to 2.7 fb{sup -1} of integrated luminosity at the Fermilab Tevatron using the CDF II detector. Events with the lepton+jets topology are selected. An unbinned likelihood is constructed based on the dependence of the lepton transverse momentum, P{sub T}, on M{sub top}. A maximum likelihood fit to the data yields a measured mass M{sub top} = 176.9 {+-} 8.0{sub stat} {+-} 2.7{sub syst} GeV/c{sup 2}. In this measurement, the contribution by the jet energy scale uncertainty to the systematic error is negligible. The result provides an important consistency test for other M{sub top} measurements where explicit use of the jet energy is made for deriving the top quark mass.
Date: January 1, 2011
Creator: Aaltonen, T.; Aaltonen, T.; Phys., /Helsinki Inst. of; Alvarez Gonzalez, B.; Phys., /Cantabria Inst. of; Amerio, S. et al.
Partner: UNT Libraries Government Documents Department

First Measurement of the Angular Coefficients of Drell-Yan $e^{+}e^{-}$ pairs in the Z Mass Region from $p\bar{p}$ Collisions at $\sqrt{s}$ = 1.96 TeV

Description: We report on the first measurement of the angular distributions of final state electrons in p{bar p} {yields} {gamma}*/Z {yields} e{sup +}e{sup -} + X events produced in the Z boson mass region at {radical}s = 1.96 TeV. The data sample collected by the CDF II detector for this result corresponds to 2.1 fb{sup -1} of integrated luminosity. The angular distributions are studied as a function of the transverse momentum of the electron-positron pair and show good agreement with the Lam-Tung relation, consistent with a spin-1 description of the gluon, and demonstrate that at high values of the transverse momentum, Z bosons are produced via quark anti-quark annihilation and quark-gluon Compton processes.
Date: March 1, 2011
Creator: Aaltonen, T.; Aaltonen, T.; Phys., /Helsinki Inst. of; Alvarez Gonzalez, B.; Phys., /Oviedo U. /Cantabria Inst. of; Amerio, S. et al.
Partner: UNT Libraries Government Documents Department

Measurement of Event Shapes in Proton-Antiproton Collisions at Center-of-Mass Energy 1.96 TeV

Description: A study of event shape observables in proton-antiproton collisions at {radical}s = 1.96 TeV is presented. The data for this analysis were recorded by the CDF II detector at the Tevatron collider. The variables studied are the transverse thrust and thrust minor, both defined in the plane perpendicular to the beam direction. The observables are measured using energies from unclustered calorimeter cells. In addition to studies of the differential distributions, we present the dependence of event shape mean values on the leading jet transverse energy. Data are compared with pythia Tune A and to resummed parton level predictions that were matched to fixed order results at NLO accuracy (NLO+NLL). Predictions from pythia Tune A agree fairly well with the data. However, the underlying event contributes significantly to these observables, making it difficult to make direct comparisons to the NLO+NLL predictions, which do not account for the underlying event. To overcome this difficulty, we introduce a new observable, a weighted difference of the mean values of the thrust and thrust minor, which is less sensitive to the underlying event, allowing for a comparison with NLO+NLL. Both pythia Tune A and the NLO+NLL calculations agree well within the 20% theoretical uncertainty with the data for this observable, indicating that perturbative QCD successfully describes shapes of the hadronic final states.
Date: March 1, 2011
Creator: Aaltonen, T.; Aaltonen, T.; Phys., /Helsinki Inst. of; Alvarez Gonzalez, B.; Phys., /Oviedo U. /Cantabria Inst. of; Amerio, S. et al.
Partner: UNT Libraries Government Documents Department

Measurements of Direct CP Violating Asymmetries in Charmless Decays of Strange Bottom Mesons and Bottom Baryons

Description: We report measurements of direct CP-violating asymmetries in charmless decays of neutral bottom hadrons to pairs of charged hadrons with the upgraded Collider Detector at the Fermilab Tevatron. Using a data sample corresponding to 1 fb{sup -1} of integrated luminosity, we obtain the first measurements of direct CP violation in bottom strange mesons, A{sub CP}(B{sub s}{sup 0} {yields} K{sup -}{pi}{sup +}) = +0.39 {+-} 0.15 (stat) {+-} 0.08 (syst), and botton baryons, A{sub CP}({Lambda}{sub b}{sup 0} {yields} p{pi}{sup -}) = + 0.03 {+-} 0.17 (stat) {+-} 0.05 (syst) and A{sub CP} ({Lambda}{sub b}{sup 0} {yields} pK{sup -}) = +0.37 {+-} 0.17 (stat) {+-} 0.03 (syst). In addition, they measure CP violation in B{sup 0} {yields} K{sup +}{pi}{sup -} decays with 3.5{sigma} significance, A{sub CP} (B{sup 0} {yields} K{sup +}{pi}{sup -}) = -0.086 {+-} 0.023 (stat) {+-} 0.009 (syst), in agreement with the current world average. Measurements of branching fractions of B{sub s}{sup 0} {yields} K{sup +}K{sup -} and B{sup 0} {yields} {pi}{sup +}{pi}{sup -} decays are also updated.
Date: March 1, 2011
Creator: Aaltonen, T.; Aaltonen, T.; Phys., /Helsinki Inst. of; Alvarez Gonzalez, B.; Phys., /Oviedo U. /Cantabria Inst. of; Amerio, S. et al.
Partner: UNT Libraries Government Documents Department

Limits on Anomalous Trilinear Gauge Couplings in $Z\gamma$ Events from $p\bar{p}$ Collisions at $\sqrt{s} = 1.96$ TeV

Description: Using Z{gamma} candidate events collected by the CDF detector at the Tevatron Collider, we search for potential anomalous (non-standard-model) couplings between the Z boson and the photon. At the hard scatter energies typical of the Tevatron, standard model Z{gamma} couplings are too weak to be detected by current experiments; hence any evidence of couplings indicates new physics. Measurements are performed using data corresponding to an integrated luminosity of 4.9 fb{sup -1} in the Z {yields} {nu}{bar {nu}} decay channel and 5.1 fb{sup -1} in the Z {yields} l{sup +}l{sup -} (l = {mu}, e) decay channels. The combination of these measurements provides the most stringent limits to date on Z{gamma} trilinear gauge couplings. Using an energy scale of {Lambda} = 1.5 TeV to allow for a direct comparison with previous measurements, we find limits on the CP-conserving parameters that describe Z{gamma} couplings to be |h{sub 3}{sup {gamma},Z}| < 0.017 and |h{sub 4}{sup {gamma},Z}| < 0.0006. These results are consistent with standard model predictions.
Date: March 1, 2011
Creator: Aaltonen, T.; Aaltonen, T.; Phys., /Helsinki Inst. of; Alvarez Gonzalez, B.; Phys., /Oviedo U. /Cantabria Inst. of; Amerio, S. et al.
Partner: UNT Libraries Government Documents Department

Search for anomalous production of multiple leptons in association with $W$ and $Z$ bosons at CDF

Description: This paper presents a search for anomalous production of multiple low-energy leptons in association with a W or Z boson using events collected at the CDF experiment corresponding to 5.1 fb{sup -1} of integrated luminosity. This search is sensitive to a wide range of topologies with low-momentum leptons, including those with the leptons near one another. The observed rates of production of additional electrons and muons are compared with the standard model predictions. No indications of phenomena beyond the standard model are found. A 95% confidence level limit is presented on the production cross section for a benchmark model of supersymmetric hidden-valley Higgs production. Particle identification efficiencies are also provided to enable the calculation of limits on additional models.
Date: February 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

Search for Standard Model Higgs Boson Production in Association with a $W$ Boson Using a Matrix Element Technique at CDF in $p\bar{p}$ Collisions at $\sqrt{s} = 1.96$ TeV

Description: This paper presents a search for standard model Higgs boson production in association with a W boson using events recorded by the CDF experiment in a dataset corresponding to an integrated luminosity of 5.6 fb{sup -1}. The search is performed using a matrix element technique in which the signal and background hypotheses are used to create a powerful discriminator. The discriminant output distributions for signal and background are fit to the observed events using a binned likelihood approach to search for the Higgs boson signal. We find no evidence for a Higgs boson, and 95% confidence level (C.L.) upper limits are set on {sigma}(p{bar p} {yields} WH) x {Beta}(H {yields} b{bar b}). The observed limits range from 3.5 to 37.6 relative to the standard model expectation for Higgs boson masses between m{sub H} = 100 GeV/c{sup 2} and m{sub H} = 150 GeV/c{sup 2}. The 95% C.L. expected limit is estimated from the median of an ensemble of simulated experiments and varies between 2.9 and 32.7 relative to the production rate predicted by the standard model over the Higgs boson mass range studied.
Date: December 1, 2011
Creator: Aaltonen, T.; Alvarez Gonzalez, B.; Amerio, S.; Amidei, D.; Anastassov, A.; Annovi, A. et al.
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

A Search for dark matter in events with one jet and missing transverse energy in $p\bar{p}$ collisions at $\sqrt{s} = 1.96$ TeV

Description: We present the results of a search for dark matter production in the monojet signature. We analyze a sample of Tevatron pp collisions at {radical}s = 1.96 TeV corresponding to an integrated luminosity of 6.7 fb{sup -1} recorded by the CDF II detector. In events with large missing transverse energy and one energetic jet, we find good agreement between the standard model prediction and the observed data. We set 90% confidence level upper limits on the dark matter production rate. The limits are translated into bounds on nucleon-dark matter scattering rates which are competitive with current direct detection bounds on spin-independent interaction below a dark matter candidate mass of 5 GeV/c{sup 2}, and on spin-dependent interactions up to masses of 200 GeV/c{sup 2}.
Date: March 1, 2012
Creator: Aaltonen, T.; Alvarez Gonzalez, B.; Amerio, S.; Amidei, D.; Anastassov, A.; Annovi, A. et al.
Partner: UNT Libraries Government Documents Department