Odderon Exchange from Elastic Scattering Differences between pp and pp[over ¯] Data at 1.96 TeV and from pp Forward Scattering Measurements.

We describe an analysis comparing the pp[over ¯] elastic cross section as measured by the D0 Collaboration at a center-of-mass energy of 1.96 TeV to that in pp collisions as measured by the TOTEM Collaboration at 2.76, 7, 8, and 13 TeV using a model-independent approach. The TOTEM cross sections, extrapolated to a center-of-mass energy of sqrt[s]=1.96 TeV, are compared with the D0 measurement in the region of the diffractive minimum and the second maximum of the pp cross section. The two data sets disagree at the 3.4σ level and thus provide evidence for the t-channel exchange of a colorless, C-odd gluonic compound, also known as the odderon. We combine these results with a TOTEM analysis of the same C-odd exchange based on the total cross section and the ratio of the real to imaginary parts of the forward elastic strong interaction scattering amplitude in pp scattering for which the significance is between 3.4σ and 4.6σ. The combined significance is larger than 5σ and is interpreted as the first observation of the exchange of a colorless, C-odd gluonic compound.

Direct observation of the strange b baryon Xib-.

We report the first direct observation of the strange b baryon Xi(b)- (Xi(b)+). We reconstruct the decay Xi(b)- -->J/psiXi-, with J/psi-->mu+mu-, and Xi--->Lambdapi--->ppi-pi- in pp collisions at square root of s =1.96 TeV. Using 1.3 fb(-1) of data collected by the D0 detector, we observe 15.2 +/- 4.4(stat)(-0.4)(+1.9)(syst) Xi(b)- candidates at a mass of 5.774 +/- 0.011(stat) +/- 0.015(syst) GeV. The significance of the observed signal is 5.5 sigma, equivalent to a probability of 3.3 x 10(-8) of it arising from a background fluctuation. Normalizing to the decay Lambda(b)-->J/psiLambda, we measure the relative rate sigma(Xi(b-) x B(Xi)b})- -->J/psiXi-)/sigma(Lambda(b)) x B(Lambda(b)-->J/psiLambda) = 0.28+/-0.09(stat)(-0.08)(+0.09)(syst).

Search for long-lived charged massive particles with the D0 detector.

We search for long-lived charged massive particles using 1.1 fb;{-1} of data collected by the D0 detector at the Fermilab Tevatron pp[over ] Collider. Time-of-flight information is used to search for pair produced long-lived tau sleptons, gauginolike charginos, and Higgsino-like charginos. We find no evidence of a signal and set 95% C.L. cross section upper limits for staus, which vary from 0.31 to 0.04 pb for stau masses between 60 and 300 GeV. We also set lower mass limits of 206 GeV (171 GeV) for pair produced charged gauginos (Higgsinos).

Search for charged higgs bosons decaying into top and bottom quarks in pp[over ] collisions.

We describe a search for production of a charged Higgs boson, qq[over ];{'}-->H;{+}, reconstructed in the tb[over ] final state in the mass range 180< or =M_{H;{+}}< or =300 GeV. The search was undertaken at the Fermilab Tevatron collider with a center-of-mass energy sqrt[s]=1.96 TeV and uses 0.9 fb;{-1} of data collected with the D0 detector. We find no evidence for charged Higgs boson production and set upper limits on the production cross section in the types I, II, and III two-Higgs-doublet models (2HDMs). An excluded region in the (M_{H;{+}}, tanbeta) plane for type I 2HDM is presented.

Measurement of the angular and lifetime parameters of the decays Bd0-->J/psiK*0 and Bs0-->J/psiphi.

We present measurements of the linear polarization amplitudes and the strong relative phases that describe the flavor-untagged decays Bd0-->J/psiK*0 and Bs0-->J/psiphi in the transversity basis. We also measure the mean lifetime taus of the Bs0 mass eigenstates and the lifetime ratio taus/taud. The analyses are based on approximately 2.8 fb(-1) of data recorded with the D0 detector. From our measurements of the angular parameters we conclude that there is no evidence for a deviation from flavor SU(3) symmetry for these decays and that the factorization assumption is not valid for the Bd0-->J/psiK*0 decay.

Search for large extra spatial dimensions in the dielectron and diphoton channels in pp[over ] collisions at sqrt[s]=1.96 TeV.

We report on a search for large extra spatial dimensions in the dielectron and diphoton channels using a data sample of 1.05 fb;{-1} of pp[over ] collisions at a center-of-mass energy of 1.96 TeV collected by the D0 detector at the Fermilab Tevatron Collider. The invariant mass spectrum of the data agrees well with the prediction of the standard model. We find the most restrictive 95% C.L. lower limits on the effective Planck scale between 2.1 and 1.3 TeV for 2 to 7 extra dimensions.

Measurement of the semileptonic branching ratio of B_{s};{0} to an orbitally excited D_{s};{**} state: Br(B_{s};{0}-->D_{s1};{-}(2536)mu;{+}nuX).

In a data sample of approximately 1.3 fb;{-1} collected with the D0 detector between 2002 and 2006, the orbitally excited charm state D_{s1};{+/-}(2536) has been observed with a measured mass of 2535.7+/-0.6(stat)+/-0.5(syst) MeV/c;{2} via the decay mode B_{s};{0}-->D_{s1};{-}(2536)mu;{+}nu_{mu}X. A first measurement is made of the branching ratio product Br(b[over ]-->D_{s1};{-}(2536)mu;{+}nu_{mu}X)xBr(D_{s1};{-}-->D;{*-}K_{S};{0}). Assuming that D_{s1};{-}(2536) production in semileptonic decay is entirely from B_{s};{0}, an extraction of the semileptonic branching ratio Br(B_{s};{0}-->D_{s1};{-}(2536)mu;{+}nu_{mu}X) is made.

Search for associated W and Higgs Boson production in pp[over ] collisions at sqrt[s]=1.96 TeV.

We present results of a search for WH-->lnubb[over ] production in pp[over ] collisions based on the analysis of 1.05 fb;{-1} of data collected by the D0 experiment at the Fermilab Tevatron, using a neural network for separating the signal from backgrounds. No signal-like excess is observed, and we set 95% C.L. upper limits on the WH production cross section multiplied by the branching ratio for H-->bb[over ] for Higgs boson masses between 100 and 150 GeV. For a mass of 115 GeV, we obtain an observed (expected) limit of 1.5 (1.4) pb, a factor of 11.4 (10.7) times larger than the standard model prediction.

Search for neutral Higgs Bosons at high tanbeta in the b(h/H/A)-->btau;{+}tau;{-} channel.

The first search in pp[over ] collisions at sqrt[s]=1.96 TeV for the production of neutral Higgs bosons in association with bottom quarks and decaying in two tau leptons is presented. The cross section for this process is enhanced in many extensions of the standard model, such as its minimal supersymmetric extension (MSSM) at large tanbeta. The data, corresponding to an integrated luminosity of 328 pb;{-1}, were collected with the D0 detector at the Fermilab Tevatron Collider. An upper limit is set on the production cross section of neutral Higgs bosons in the mass range of 90 to 150 GeV, and this limit is used to exclude part of the MSSM parameter space.

Evidence for the decay Bs0-->Ds(*)Ds(*) and a measurement of DeltaGammasCP/Gammas.

We search for the semi-inclusive process Bs0-->Ds(*)Ds(*) using 2.8 fb(-1) of pp collisions at sqrt[s]=1.96 TeV recorded by the D0 detector operating at the Fermilab Tevatron Collider. We observe 26.6+/-8.4 signal events with a significance above background of 3.2 standard deviations yielding a branching ratio of B(Bs0-->Ds(*)Ds(*))=0.035+/-0.010(stat.)+/-0.011(syst.). Under certain theoretical assumptions, these double-charm final states saturate CP-even eigenstates in the Bs0 decays resulting in a width difference of DeltaGammasCP/Gammas=0.072+/-0.021(stat.)+/-0.022(syst.).

Measurement of the lifetime of the Bc+/- meson in the semileptonic decay channel.

Using approximately 1.3 fb(-1) of data collected by the D0 detector between 2002 and 2006, we measure the lifetime of the Bc+/- meson in the Bc-/+-->J/psimicro+/-+X final state. A simultaneous unbinned likelihood fit to the J/psi+micro invariant mass and lifetime distributions yields a signal of 881+/-80(stat) candidates and a lifetime measurement of tau(Bc+/-)=0.448(-0.036)(+0.038)(stat)+/-0.032(syst) ps.

Search for anomalous top-quark couplings with the D0 detector.

Anomalous Wtb couplings modify the angular correlations of the top-quark decay products and change the single top-quark production cross section. We present limits on anomalous top-quark couplings by combining information from W boson helicity measurements in top-quark decays and anomalous coupling searches in the single top-quark final state. We set limits on right-handed vector couplings as well as left-handed and right-handed tensor couplings based on about 1 fb(-1) of data collected by the D0 experiment.

Search for resonant diphoton production with the D0 detector.

We present a search for a narrow resonance in the inclusive diphoton final state using approximately 2.7 fb(-1) of data collected with the D0 detector at the Fermilab Tevatron pp Collider. We observe good agreement between the data and the background prediction, and set the first 95% C.L. upper limits on the production cross section times the branching ratio for decay into a pair of photons for resonance masses between 100 and 150 GeV. This search is also interpreted in the context of several models of electroweak symmetry breaking with a Higgs boson decaying into two photons.

Search for flavor-changing-neutral-current d meson decays.

We study the flavor-changing-neutral-current process c-->u micro(+) micro(-) using 1.3 fb(-1) of pp[over ] collisions at square root s = 1.96 TeV recorded by the D0 detector operating at the Fermilab Tevatron Collider. We see clear indications of the charged-current mediated D(s)(+) and D(+)-->phipi(+) --> micro(+)micro(-)pi(+) final states with significance greater than 4 standard deviations above background for the D(+) state. We search for the continuum neutral-current decay of D(+)-->pi(+) micro(+) micro(-) in the dimuon invariant mass spectrum away from the phi resonance. We see no evidence of signal above background and set a limit of B(D(+) --> pi(+) micro(+) micro(-))<3.9 x 10(-6) at the 90% C.L. This limit places the most stringent constraint on new phenomena in the c--> u micro(+) micro(-) transition.

Model-independent measurement of the W-boson helicity in top-quark decays at D0.

We present the first model-independent measurement of the helicity of W bosons produced in top quark decays, based on a 1 fb(-1) sample of candidate tt events in the dilepton and lepton plus jets channels collected by the D0 detector at the Fermilab Tevatron pp Collider. We reconstruct the angle theta(*) between the momenta of the down-type fermion and the top quark in the W boson rest frame for each top quark decay. A fit of the resulting costheta(*) distribution finds that the fraction of longitudinal W bosons f(0)=0.425+/-0.166(stat)+/-0.102(syst) and the fraction of right-handed W bosons f(+)=0.119+/-0.090(stat)+/-0.053(syst), which is consistent at the 30% C.L. with the standard model.

Observation and properties of the orbitally excited B_(s2)(*) meson.

We report the direct observation of the excited L=1 state B_(s2)(*) in fully reconstructed decays to B+K-. The mass of the B_(s2)(*) meson is measured to be 5839.6+/-1.1(stat)+/-0.7(syst) MeV/c(2), and its production rate relative to the B+ meson is measured to be [1.15+/-0.23(stat)+/-0.13(syst)]%.

Search for Randall-Sundrum gravitons with 1 fb(-1) of data from pp collisions at sqrt(s)=1.96 TeV.

We search for decays of Kaluza-Klein excitations of the graviton in the Randall-Sundrum model of extra dimensions to e+ e(-) and gamma gamma in 1 fb(-1) of pp collisions at sqrt(s)=1.96 TeV collected by the D0 detector at the Fermilab Tevatron. We set 95% confidence level upper limits on the production cross section times branching fraction, which translate into lower limits on the mass of the lightest excitation between 300 and 900 GeV for values of the coupling k/MPl between 0.01 and 0.1.

Search for W' bosons decaying to an electron and a neutrino with the D0 detector.

This Letter describes the search for a new heavy charged gauge boson W' decaying into an electron and a neutrino. The data were collected with the D0 detector at the Fermilab Tevatron pp[over] Collider at sqrt[s]=1.96 TeV, and correspond to an integrated luminosity of about 1 fb(-1). Lacking any significant excess in the data in comparison with known processes, an upper limit is set on sigma_(W') x B(W')-->e nu), and a W' boson with mass below 1.00 TeV can be excluded at the 95% C.L., assuming standard-model-like couplings to fermions. This result significantly improves upon previous limits and is the most stringent to date.

Search for ZZ and Zgamma* production in pp[over ] collisions at square root s=1.96 TeV and limits on anomalous ZZZ and ZZgamma* couplings.

We present a study of micro micro micro micro, eeee, and micro micro ee events using 1 fb(-1) of data collected with the D0 detector at the Fermilab Tevatron pp[over ] Collider at square root s=1.96 TeV. Requiring the lepton pair masses to be greater than 30 GeV, we observe one event, consistent with the expected background of 0.13+/-0.03 events and with the predicted standard model ZZ and Zgamma* production of 1.71+/-0.15 events. We set an upper limit on the ZZ and Zgamma* cross section of 4.4 pb at the 95% C.L. We also derive limits on anomalous neutral trilinear ZZZ and ZZgamma* gauge couplings. The one-parameter 95% C.L. coupling limits with a form-factor scale Lambda=1.2 TeV are -0.28

Measurement of the forward-backward charge asymmetry in top-quark pair production.

We present the first measurement of the integrated forward-backward charge asymmetry in top-quark-top-antiquark pair (tt) production in proton-antiproton (pp) collisions in the lepton+jets final state. Using a b-jet tagging algorithm and kinematic reconstruction assuming tt + X production and decay, a sample of 0.9 fb(-1) of data, collected by the D0 experiment at the Fermilab Tevatron Collider, is used to measure the asymmetry for different jet multiplicities. The result is also used to set upper limits on tt+X production via a Z' resonance.