Combination of Tevatron Searches for the Standard Model Higgs Boson in the W(+)W(−) Decay Mode

This is the publisher's version, also available electronically from http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.104.061802.We combine searches by the CDF and D0 Collaborations for a Higgs boson decaying to W(+)W(−). The data correspond to an integrated total luminosity of 4.8 (CDF) and 5.4 (D0) fb(−1) of pp-bar collisions at s√=1.96  TeV at the Fermilab Tevatron collider. No excess is observed above background expectation, and resulting limits on Higgs boson production exclude a standard model Higgs boson in the mass range 162–166 GeV at the 95% C.L

Search for charged Higgs bosons in decays of top quarks

This is the publisher's version, also available electronically from http://journals.aps.org/prd/abstract/10.1103/PhysRevD.80.051107.We present a search for charged Higgs bosons in decays of top quarks, in the mass range 800.24 for m(H±)=80  GeV and B(t→H(+b))>0.19 for mH±=155  GeV at the 95% C.L

Search for New Fermions (“Quirks”) at the Fermilab Tevatron Collider

This is the publisher's version, also available electronically from http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.105.211803.We report results of a search for particles with anomalously high ionization in events with a high transverse energy jet and large missing transverse energy in 2.4  fb(−1) of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron pp-bar collider. Production of such particles (quirks) is expected in scenarios with extra QCD-like SU(N) sectors, and this study is the first dedicated search for such signatures. We find no evidence of a signal and set a lower mass limit of 107, 119, and 133 GeV for the mass of a charged quirk with strong dynamics scale Λ in the range from 10 keV to 1 MeV and N=2, 3, and 5, respectively

Measurement of the top quark mass in final states with two leptons

This is the publisher's version, also available electronically from http://journals.aps.org/prd/abstract/10.1103/PhysRevD.80.092006.We present measurements of the top quark mass (mt) in tt-bar candidate events with two final state leptons using 1  fb(−1) of data collected by the D0 experiment. Our data sample is selected by requiring two fully identified leptons or by relaxing one lepton requirement to an isolated track if at least one jet is tagged as a b jet. The top quark mass is extracted after reconstructing the event kinematics under the tt-bar hypothesis using two methods. In the first method, we integrate over expected neutrino rapidity distributions, and in the second we calculate a weight for the possible top quark masses based on the observed particle momenta and the known parton distribution functions. We analyze 83 candidate events in the data and obtain mt=176.2±4.8(stat)±2.1(sys)  GeV and mt=173.2±4.9(stat)±2.0(sys)  GeV for the two methods, respectively. Accounting for correlations between the two methods, we combine the measurements to obtain mt=174.7±4.4(stat)±2.0(sys)  GeV

Direct Measurement of the W Boson Width

This is the publisher's version, also available electronically from http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.103.231802.We present a direct measurement of the width of the W boson using the shape of the transverse mass distribution of W→eν candidate events. Data from approximately 1  fb(−1) of integrated luminosity recorded at s√=1.96  TeV by the D0 detector at the Fermilab Tevatron pp-bar collider are analyzed. We use the same methods and data sample that were used for our recently published W boson mass measurement, except for the modeling of the recoil, which is done with a new method based on a recoil library. Our result, 2.028±0.072  GeV, is in agreement with the predictions of the standard model

Measurement of the tt-bar cross section using high-multiplicity jet events

This is the publisher's version, also available electronically from http://journals.aps.org/prd/abstract/10.1103/PhysRevD.82.032002.We present a measurement of the tt-bar cross section using high-multiplicity jet events produced in pp-bar collisions at s√=1.96  TeV. These data were recorded at the Fermilab Tevatron Collider with the D0 detector. Events with at least six jets, two of them identified as b jets, were selected from a 1  fb(−1) data set. The measured cross section, assuming a top quark mass of 175  GeV/c2, is 6.9±2.0  pb, in agreement with theoretical expectations

Search for the Associated Production of a b Quark and a Neutral Supersymmetric Higgs Boson that Decays into τ Pairs

This is the publisher's version, also available electronically from http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.104.151801.We report results from a search for production of a neutral Higgs boson in association with a b quark. We search for Higgs decays to τ pairs with one τ subsequently decaying to a muon and the other to hadrons. The data correspond to 2.7  fb(−1) of pp-bar collisions recorded by the D0 detector at s√=1.96  TeV. The data are found to be consistent with background predictions. The result allows us to exclude a significant region of parameter space of the minimal supersymmetric model

High mass exclusive diffractive dijet production in ppbar collisions at √s = 1.96 TeV

We present evidence for diffractive exclusive dijet production with an invariant dijet mass greater than 100 GeV in data collected with the D0 experiment at the Fermilab Tevatron Collider. A discriminant based on calorimeter information is used to measure a significant number of events with little energy (typically less than 10 GeV) outside the dijet system, consistent with the diffractive exclusive dijet production topology. The probability for these events to be explained by other dijet production processes is 2×^(10−6), corresponding to a 4.7 standard deviation significance

Combined Tevatron upper limit on gg→H→W^(+)W^(−) and constraints on the Higgs boson mass in fourth-generation fermion models

This is the publisher's version, also available electronically from http://journals.aps.org/prd/abstract/10.1103/PhysRevD.82.011102

Search for Charged Massive Long-Lived Particles

This is the publisher's version, also available electronically from http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.108.121802.We report on a search for charged massive long-lived particles (CMLLPs), based on 5.2  fb^(−1) of integrated luminosity collected with the D0 detector at the Fermilab Tevatron ppbar collider. We search for events in which one or more particles are reconstructed as muons but have speed and ionization energy loss (dE/dx) inconsistent with muons produced in beam collisions. CMLLPs are predicted in several theories of physics beyond the standard model. We exclude pair-produced long-lived gauginolike charginos below 267 GeV and Higgsino-like charginos below 217 GeV at 95% C.L., as well as long-lived scalar top quarks with mass below 285 GeV