S. B. Beri

We report the observation of the X(3872) in the J/psipi(+)pi(-) channel, with J/psi decaying to mu(+)mu(-), in pp collisions at sqrt[s]=1.96 TeV. Using approximately 230 pb(-1) of data collected with the Run II D0 detector, we observe 522+/-100 X(3872) candidates. The mass difference between the X(3872) state and the J/psi is measured to be 774.9+/-3.1(stat)+/-3.0(syst) MeV/c(2). We have investigated the production and decay characteristics of the X(3872) and find them to be similar to those of the psi(2S) state.

We combine searches by the CDF and D0 Collaborations for the associated production of a Higgs boson with a W or Z boson and subsequent decay of the Higgs boson to a bottom-antibottom quark pair. The data, originating from Fermilab Tevatron pp collisions at √s = 1.96 TeV, correspond to integrated luminosities of up to 9.7 fb(-1). The searches are conducted for a Higgs boson with mass in the range 100-150 GeV/c(2). We observe an excess of events in the data compared with the background predictions, which is most significant in the mass range between 120 and 135 GeV/c(2). The largest local significance is 3.3 standard deviations, corresponding to a global significance of 3.1 standard deviations. We interpret this as evidence for the presence of a new particle consistent with the standard model Higgs boson, which is produced in association with a weak vector boson and decays to a bottom-antibottom quark pair.

We report on a measurement of the inclusive jet cross section in pp[over ] collisions at a center-of-mass energy sqrt[s]=1.96 TeV using data collected by the D0 experiment at the Fermilab Tevatron Collider corresponding to an integrated luminosity of 0.70 fb;{-1}. The data cover jet transverse momenta from 50 to 600 GeV and jet rapidities in the range -2.4 to 2.4. Detailed studies of correlations between systematic uncertainties in transverse momentum and rapidity are presented, and the cross section measurements are found to be in good agreement with next-to-leading order QCD calculations.

We present the first measurement of the integrated forward-backward charge asymmetry in top-quark–top-antiquark pair (t¯t) production in proton-antiproton (p¯p) collisions in the lepton+jets final state. Using a b-jet tagging algorithm and kinematic reconstruction assuming t¯t+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 t¯t+X production via a Z′ resonance.Received 7 December 2007DOI:https://doi.org/10.1103/PhysRevLett.100.142002©2008 American Physical Society

From an analysis of the flavor-tagged decay Bs0-->J/psiphi we obtain the width difference between the Bs0 light and heavy mass eigenstates, DeltaGammas = 0.19+/-0.07(stat)(-0.01)+0.02(syst) ps(-1), and the CP-violating phase, phi s= -0.57(-0.30)+0.24(stat)(-0.02)+0.08(syst). The allowed 90% CL intervals of DeltaGammas and phi s are 0.06 < DeltaGammas < 0.30 ps(-1) and -1.20 < phi s < 0.06, respectively. The data sample corresponds to an integrated luminosity of 2.8 fb(-1) accumulated with the D0 detector at the Fermilab Tevatron collider.

We report results of a study of the B(s)(0) oscillation frequency using a large sample of B(s)(0) semileptonic decays corresponding to approximately 1 fb(-1) of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron Collider in 2002-2006. The amplitude method gives a lower limit on the B(s)(0) oscillation frequency at 14.8 ps(-1) at the 95% C.L. At delta m(s) = 19 ps(-1), the amplitude deviates from the hypothesis A= 0(1) by 2.5 (1.6) standard deviations, corresponding to a two-sided C.L. of 1% (10%). A likelihood scan over the oscillation frequency, delta m(s), gives a most probable value of 19 ps(-1) and a range of 17 < delta m(s) < 21 ps(-1)at the 90% C.L., assuming Gaussian uncertainties. This is the first direct two-sided bound measured by a single experiment. If delta m(s) lies above 22 ps(-1), then the probability that it would produce a likelihood minimum similar to the one observed in the interval 16-22 ps(-1) is (5.0 +/- 0.3)%.

We have used a sample of photon+3 jets events collected by the D0 experiment with an integrated luminosity of about 1 fb^-1 to determine the fraction of events with double parton scattering (f_DP) in a single ppbar collision at sqrt{s}=1.96 TeV. The DP fraction and effective cross section (sigma_eff), a process-independent scale parameter related to the parton density inside the nucleon, are measured in three intervals of the second (ordered in pT) jet transverse momentum pT_jet2 within the range 15 < pT_jet2 < 30 GeV. In this range, f_DP varies between 0.23 < f_DP < 0.47, while sigma_eff has the average value sigma_eff_ave = 16.4 +- 0.3(stat) +- 2.3(syst) mb.

We measure the charge asymmetry A ≡ (N++ - N--)/(N++ + N--) of like-sign dimuon events in 6.1 fb-1 of pp collisions recorded with the D0 detector at a center-of-mass energy square root(s) = 1.96 TeV at the Fermilab Tevatron collider. From A we extract the like-sign dimuon charge asymmetry in semileptonic b-hadron decays: A(sl)(b) = -0.009 57 ± 0.002 51(stat) ± 0.001 46(sys). It differs by 3.2 standard deviations from the standard model prediction A(sl)(b)(SM) = (-2.3(-0.6)(+0.5)) × 10(-4), and provides first evidence of anomalous CP violation in the mixing of neutral B mesons.

We report evidence for a narrow structure, X(5568), in the decay sequence X(5568)→B_{s}^{0}π^{±}, B_{s}^{0}→J/ψϕ, J/ψ→μ^{+}μ^{-}, ϕ→K^{+}K^{-}. This is evidence for the first instance of a hadronic state with valence quarks of four different flavors. The mass and natural width of this state are measured to be m=5567.8±2.9(stat)_{-1.9}^{+0.9}(syst) MeV/c^{2} and Γ=21.9±6.4(stat)_{-2.5}^{+5.0}(syst) MeV/c^{2}. If the decay is X(5568)→B_{s}^{*}π^{±}→B_{s}^{0}γπ^{±} with an unseen γ, m(X(5568)) will be shifted up by m(B_{s}^{*})-m(B_{s}^{0})∼49 MeV/c^{2}. This measurement is based on 10.4 fb^{-1} of pp[over ¯] collision data at sqrt[s]=1.96 TeV collected by the D0 experiment at the Fermilab Tevatron collider.

We measure the charge asymmetry $A$ of like-sign dimuon events in 6.1 fb$^{-1}$ of $p\bar{p}$ collisions recorded with the D0 detector at a center-of-mass energy $\sqrt{s} = 1.96$ TeV at the Fermilab Tevatron collider. From $A$, we extract the like-sign dimuon charge asymmetry in semileptonic $b$-hadron decays: $\aslb = -0.00957 \pm 0.00251 ({\rm stat}) \pm 0.00146 ({\rm syst})$. This result differs by 3.2 standard deviations from the standard model prediction $\aslb(SM) = (-2.3^{+0.5}_{-0.6}) \times 10^{-4}$ and provides first evidence of anomalous CP-violation in the mixing of neutral $B$ mesons.

The top quark is the heaviest known elementary particle, with a mass about 40 times larger than the mass of its isospin partner, the bottom quark. It decays almost 100% of the time to a $W$ boson and a bottom quark. Using top-antitop pairs at the Tevatron proton-antiproton collider, the CDF and D0 Collaborations have measured the top quark's mass in different final states for integrated luminosities of up to $5.8\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$. This paper reports on a combination of these measurements that results in a more precise value of the mass than any individual decay channel can provide. It describes the treatment of the systematic uncertainties and their correlations. The mass value determined is $173.18\ifmmode\pm\else\textpm\fi{}0.56\text{ }(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.75\text{ }(\mathrm{syst})\text{ }\text{ }\mathrm{GeV}$ or $173.18\ifmmode\pm\else\textpm\fi{}0.94\text{ }\text{ }\mathrm{GeV}$, which has a precision of $\ifmmode\pm\else\textpm\fi{}0.54%$, making this the most precise determination of the top-quark mass.

We present a search for charged Higgs bosons in top quark decays. We analyze the \eplus, \muplus, $ee$, $e\mu$, $\mu\mu$, \etau and \mutau final states from top quark pair production events, using data from about 1${\text{fb}}^{-1}$ of integrated luminosity recorded by the \dzero experiment at the Fermilab Tevatron Collider. We consider different scenarios of possible charged Higgs boson decays, one where the charged Higgs boson decays purely hadronically into a charm and a strange quark, another where it decays into a $\tau$ lepton and a $\tau$ neutrino and a third one where both decays appear. We extract limits on the branching ratio $B(t\to H^+ b)$ for all these models. We use two methods, one where the $t\bar{t}$ production cross section is fixed, and one where the cross section is fitted simultaneously with $B(t\to H^+b)$. Based on the extracted limits, we exclude regions in the charged Higgs boson mass and $\tan \beta$ parameter space for different scenarios of the minimal supersymmetric standard model.

We present an updated measurement of the anomalous like-sign dimuon charge asymmetry Aslb for semi-leptonic $b$-hadron decays in 9.0 fb^-1 of p pbar collisions recorded with the D0 detector at a center-of-mass energy of sqrt{s} = 1.96 TeV at the Fermilab Tevatron collider. We obtain Aslb = (-0.787 +- 0.172(stat) +- 0.093 (syst))%. This result differs by 3.9 standard deviations from the prediction of the standard model and provides evidence for anomalously large CP violation in semi-leptonic neutral B decay. The dependence of the asymmetry on the muon impact parameter is consistent with the hypothesis that it originates from semi-leptonic b-hadron decays.

We combine searches by the CDF and D0 Collaborations for the standard model Higgs boson with mass in the range 90–200 GeV/c2 produced in the gluon-gluon fusion, WH, ZH, t¯tH, and vector boson fusion processes, and decaying in the H→b¯b, H→W+W−, H→ZZ, H→τ+τ−, and H→γγ modes. The data correspond to integrated luminosities of up to 10 fb−1 and were collected at the Fermilab Tevatron in p¯p collisions at √s=1.96 TeV. The searches are also interpreted in the context of fermiophobic and fourth generation models. We observe a significant excess of events in the mass range between 115 and 140 GeV/c2. The local significance corresponds to 3.0 standard deviations at mH=125 GeV/c2, consistent with the mass of the Higgs boson observed at the LHC, and we expect a local significance of 1.9 standard deviations. We separately combine searches for H→b¯b, H→W+W−, H→τ+τ−, and H→γγ. The observed signal strengths in all channels are consistent with the presence of a standard model Higgs boson with a mass of 125 GeV/c2.18 MoreReceived 26 March 2013DOI:https://doi.org/10.1103/PhysRevD.88.052014© 2013 American Physical Society

We report an updated measurement of the CP-violating phase, $\phi_s^{J/\psi \phi}$, and the decay-width difference for the two mass eigenstates, $\Delta \Gamma_s$, from the flavor-tagged decay $B_s^0 \rightarrow J/\psi \phi$. The data sample corresponds to an integrated luminosity of 8.0 fb$^{-1}$ accumulated with the D0 detector using $p \barp$ collisions at $\sqrt{s} = 1.96$ TeV produced at the Fermilab Tevatron collider. The 68% confidence level intervals, including systematic uncertainties, are $\Delta \Gamma_s = 0.163 +0.065 -0.064 ps^{-1}$ and $\phi_s^{J/\psi \phi} = -0.55 +0.38 -0.36$. The $p$-value for the Standard Model point is 29.8%.

We investigate the decay B + → J/ψφK + in a search for the X(4140) state, a narrow threshold resonance in the J/ψφ system.The data sample corresponds

We describe an analysis comparing the $p\overline{p}$ 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 $\sqrt{s}=1.96\text{ }\text{ }\mathrm{TeV}$, 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 $3.4\ensuremath{\sigma}$ 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 $3.4\ensuremath{\sigma}$ and $4.6\ensuremath{\sigma}$. The combined significance is larger than $5\ensuremath{\sigma}$ and is interpreted as the first observation of the exchange of a colorless, $C$-odd gluonic compound.

The D0 collaboration has performed a measurement of the top quark mass based on six candidate events for the process t tbar -&gt; b W+ bbar W-, where the W bosons decay to e nu or mu nu. This sample was collected during an exposure of the D0 detector to an integrated luminosity of 125 pb^-1 of sqrt(s)=1.8 TeV p-pbar collisions. We obtain mt = 168.4 +- 12.3 (stat) +- 3.7 (sys) GeV/c^2, consistent with the measurement obtained using single-lepton events. Combination of the single-lepton and dilepton results yields mt = 172.0 +- 7.5 GeV/c^2.

We determine the top quark mass mt using tt¯ pairs produced in the DØ detector by s=1.8TeV pp¯ collisions in a 125pb−1 exposure at the Fermilab Tevatron. We make a two constraint fit to mt in tt¯→bW+b¯W− final states with one W boson decaying to qq¯ and the other to eν or μν. Likelihood fits to the data yield mt(l+jets)=173.3±5.6(stat)±5.5(syst) GeV/c2. When this result is combined with an analysis of events in which both W bosons decay into leptons, we obtain mt=172.1±5.2(stat)±4.9(syst) GeV/c2. An alternate analysis, using three constraint fits to fixed top quark masses, gives mt(l+jets)=176.0±7.9(stat)±4.8(syst) GeV/c2, consistent with the above result. Studies of kinematic distributions of the top quark candidates are also presented. 14.65.Ha, 13.85.Ni, 13.85.QkReceived 27 January 1998DOI:https://doi.org/10.1103/PhysRevD.58.052001©1998 American Physical Society

A data sample corresponding to an integrated luminosity of 2.1 fb−1 collected by the DØ detector at the Fermilab Tevatron Collider was analyzed to search for squarks and gluinos produced in pp¯ collisions at a center-of-mass energy of 1.96 TeV. No evidence for the production of such particles was observed in topologies involving jets and missing transverse energy, and 95% C.L. lower limits of 379 GeV and 308 GeV were set on the squark and gluino masses, respectively, within the framework of minimal supergravity with tanβ=3, A0=0, and μ<0. The corresponding previous limits are improved by 54 GeV and 67 GeV.

We present a measurement of the shape of the $Z/{\ensuremath{\gamma}}^{*}$ boson transverse momentum (${q}_{T}$) distribution in $p\overline{p}\ensuremath{\rightarrow}Z/{\ensuremath{\gamma}}^{*}\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}}+X$ events at a center-of-mass energy of 1.96 TeV using $0.98\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of data collected with the D0 detector at the Fermilab Tevatron collider. The data are found to be consistent with the resummation prediction at low ${q}_{T}$, but above the perturbative QCD calculation in the region of ${q}_{T}&gt;30\text{ }\text{ }\mathrm{GeV}/c$. Using events with ${q}_{T}&lt;30\text{ }\text{ }\mathrm{GeV}/c$, we extract the value of ${g}_{2}$, one of the nonperturbative parameters for the resummation calculation. Data at large boson rapidity $y$ are compared with the prediction of resummation and with alternative models that employ a resummed form factor with modifications in the small Bjorken $x$ region of the proton wave function.

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).

We combine measurements of the top quark pair production cross section in p¯p collisions in the ℓ+jets, ℓℓ, and τℓ final states (where ℓ is an electron or muon) at a center of mass energy of √s=1.96 TeV in 1 fb−1 of data collected with the D0 detector. For a top quark mass of 170 GeV/c2, we obtain σt¯t=8.18+0.98−0.87 pb in agreement with the theoretical prediction. Based on predictions from higher order quantum chromodynamics, we extract a mass for the top quark from the combined t¯t cross section, consistent with the world average of the top quark mass. In addition, the ratios of t¯t cross sections in different final states are used to set upper limits on the branching fractions B(t→H+b→τ+νb) and B(t→H+b→c¯sb) as a function of the charged Higgs boson mass.Received 31 March 2009DOI:https://doi.org/10.1103/PhysRevD.80.071102©2009 American Physical Society

We present the first measurement of dijet angular distributions in ppbar collisions at sqrt{s}=1.96TeV at the Fermilab Tevatron Collider. The measurement is based on a dataset corresponding to an integrated luminosity of up to 0.7fb-1 collected with the D0 detector. Dijet angular distributions have been measured over a range of dijet masses, from 0.25TeV to above 1.1TeV. The data are in good agreement with the predictions of perturbative QCD and are used to constrain new physics models including quark compositeness, large extra dimensions, and TeV-1 scale extra dimensions. For all models we set the most stringent direct limits to date.

We summarize and combine direct measurements of the mass of the W boson in √s=1.96 TeV proton-antiproton collision data collected by CDF and D0 experiments at the Fermilab Tevatron Collider. Earlier measurements from CDF and D0 are combined with the two latest, more precise measurements: a CDF measurement in the electron and muon channels using data corresponding to 2.2 fb−1 of integrated luminosity, and a D0 measurement in the electron channel using data corresponding to 4.3 fb−1 of integrated luminosity. The resulting Tevatron average for the mass of the W boson is MW=80387±16 MeV. Including measurements obtained in electron-positron collisions at LEP yields the most precise value of MW=80385±15 MeV.Received 29 July 2013DOI:https://doi.org/10.1103/PhysRevD.88.052018© 2013 American Physical Society

A fully reconstructed Bc-->J/psipi signal is observed with the D0 detector at the Fermilab Tevatron pp[over] collider using 1.3 fb(-1) of integrated luminosity. The signal consists of 54+/-12 candidates with a significance that exceeds 5 standard deviations, and confirms earlier observations of this decay. The measured mass of the Bc meson is 6300+/-14(stat)+/-5(syst) MeV/c2.

We combine six measurements of the inclusive top-quark pair (ttbar) production cross section (sigma_ttbar) from data collected with the CDF and D0 detectors at the Fermilab Tevatron with proton anti-proton collisions at sqrt{s} = 1.96 TeV. The data correspond to integrated luminosities of up to 8.8 fb^{-1}. We obtain a value of sigma_ttbar = 7.60 \pm 0.41 pb for a top-quark mass of m_t=172.5 GeV. The contributions to the uncertainty are 0.20 pb from statistical sources, 0.29 pb from systematic sources, and 0.21 pb from the uncertainty on the integrated luminosity. The result is in good agreement with the standard model expectation of 7.35^{+0.28}_{-0.33} pb at NNLO+NNLL in pertubative QCD.

We present an improved determination of the total width of the top quark, $Γ_t$, using 5.4 fb$^{-1}$ of integrated luminosity collected by the D0 Collaboration at the Tevatron $p\bar{p}$ Collider. The total width $Γ_t$ is extracted from the partial decay width $Γ(t\to Wb)$ and the branching fraction $\mathcal{B}(t\to Wb)$. $Γ(t\to Wb)$ is obtained from the $t$-channel single top quark production cross section and $\mathcal{B}(t\to Wb)$ is measured in $t\bar{t}$ events. For a top mass of $172.5\;\rm GeV$, the resulting width is $Γ_t = 2.00^{+0.47}_{-0.43}$ GeV. This translates to a top-quark lifetime of $τ_t = (3.29^{+0.90}_{-0.63})\times10^{-25}$ s. We also extract an improved direct limit on the CKM matrix element $0.81 &lt; |V_{tb}| \leq 1$ at 95% C.L. and a limit of $|V_{tb'}| &lt; 0.59$ for a high mass fourth generation bottom quark assuming unitarity of the fourth generation quark mixing matrix.

We present a measurement of the inclusive jet cross section using the Run II cone algorithm and data collected by the D0 experiment in p pbar collisions at a center-of-mass energy sqrt(s)=1.96 TeV, corresponding to an integrated luminosity of 0.70 fb^(-1). The jet energy calibration and the method used to extract the inclusive jet cross section are described. We discuss the main uncertainties, which are dominated by the jet energy scale uncertainty. The results cover jet transverse momenta from 50 GeV to 600 GeV with jet rapidities in the range -2.4 to 2.4 and are compared to predictions using recent proton parton distribution functions. Studies of correlations between systematic uncertainties in transverse momentum and rapidity are presented.

We present the observation of doubly-produced $J/\psi$ mesons with the D0 detector at Fermilab in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV. The production cross section for both singly and doubly-produced $J/\psi$ mesons is measured using a sample with an integrated luminosity of 8.1fb$^{-1}$. For the first time, the double $J/\psi$ production cross section is separated into contributions due to single and double parton scatterings. Using these measurements, we determine the effective cross section $\sigma_{eff}$, a parameter characterizing an effective spatial area of the parton-parton interactions and related to the parton spatial density inside the nucleon.

We present the final combination of CDF and D0 measurements of cross sections for single-top-quark production in proton-antiproton collisions at a center-of-mass energy of 1.96 TeV. The data correspond to total integrated luminosities of up to 9.7 fb^{-1} per experiment. The t-channel cross section is measured to be σ_{t}=2.25_{-0.31}^{+0.29} pb. We also present the combinations of the two-dimensional measurements of the s- vs t-channel cross section. In addition, we give the combination of the s+t channel cross section measurement resulting in σ_{s+t}=3.30_{-0.40}^{+0.52} pb, without assuming the standard model value for the ratio σ_{s}/σ_{t}. The resulting value of the magnitude of the top-to-bottom quark coupling is |V_{tb}|=1.02_{-0.05}^{+0.06}, corresponding to |V_{tb}|>0.92 at the 95% C.L.

We present a search for events consistent with the production and decay of the squarks and gluinos of the minimal supersymmetric standard model (MSSM) in the D0 detector at the Fermilab Tevatron $p\overline{p}$ collider. We examined data for events containing large missing transverse energy and three or more jets. We observed no excess of events above the expected yield from standard model processes. For a choice of MSSM parameter values, we set a lower limit at the 95% confidence level on the mass of the gluino of 144 GeV ${/c}^{2}$ for all squark masses and a lower limit of 212 GeV ${/c}^{2}$ for equal squark and gluino masses.

We measure the top quark mass m t using t t pairs produced in the DØ detector by √ s = 1.8 TeV pp collisions in a 125 pb -1 exposure at the Fermilab Tevatron.We make a two constraint fit to m t in t t → bW + bW -final states with one W decaying to q q and the other to eν or µν.Events are binned in fit mass versus a measure of probability for events to be signal rather than background.Likelihood fits to the data yield m t = 173.3± 5.6 (stat) ± 6.2 (syst) GeV/c 2 .

We report a measurement of the inclusive muon and b-quark production cross sections in pp¯ collisions at s=1.8 TeV using the D0 detector at the Fermilab Tevatron collider. The inclusive muon spectrum extends over the kinematic range |yμ|<0.8 and 3.5<pTμ<60GeV/c, and is well described by the expected contributions from various known sources. The b-quark production cross section for |yb|<1.0 and pTb>6GeV/c is extracted, and agrees with next-to-leading order QCD predictions within the experimental and theoretical uncertainties.Received 12 December 1994DOI:https://doi.org/10.1103/PhysRevLett.74.3548©1995 American Physical Society

The cross section for the inclusive production of isolated photons has been measured in pp¯ collisions at s=1.96TeV with the DØ detector at the Fermilab Tevatron Collider. The photons span transverse momenta 23 to 300 GeV and have pseudorapidity |η|<0.9. The cross section is compared with the results from two next-to-leading order perturbative QCD calculations. The theoretical predictions agree with the measurement within uncertainties.

We have studied Jψ production in pp collisions at s = 1.8 TeV with the DØ detector at Fermilab using μ+μ− data. We have measured the inclusive Jψ production cross section as a function of Jψ transverse momentum, pT. For the kinematic range pT > 8 GeV/c and |η| < 0.6 we obtain σ(pp → Jψ + X) · Br(Jψ → μ+μ−) = 2.08 ± 0.17(stat) ± 0.46(syst) nb. Using the muon impact parameter we have estimated the fraction of Jψ mesons coming from B meson decays to be fb = 0.35 ± 0.09(stat)±0.10(syst) and inferred the inclusive b production cross section. From the information on the event topology the fraction of nonisolated Jψ events has been measured to be fnonisol = 0.64 ± 0.08(stat)±0.06(syst). We have also obtained the fraction of Jψ events resulting from radiative decays of χc states, fχ = 0.32 ± 0.07(stat)±0.07(syst). We discuss the implications of our measurements for charmonium production processes.

We present a measurement of the inclusive jet cross section in p¯p collisions at √s =1.8 TeV at the Fermilab Tevatron using the Collider Detector at Fermilab. Good agreement is seen with the predictions of recent next-to-leading-order [O(α3s)] QCD predictions. The dependence of the cross section on clustering cone size is reported for the first time. An improved limit on Λc, a term characterizing possible quark substructure, is set at 1.4 TeV (95% C.L.).Received 7 August 1991DOI:https://doi.org/10.1103/PhysRevLett.68.1104©1992 American Physical Society

Correlations in the azimuthal angle between the two largest transverse momentum jets have been measured using the D0 detector in $p\overline{p}$ collisions at a center-of-mass energy $\sqrt{s}=1.96\text{ }\text{ }\mathrm{TeV}$. The analysis is based on an inclusive dijet event sample in the central rapidity region corresponding to an integrated luminosity of $150\text{ }\text{ }{\mathrm{pb}}^{\ensuremath{-}1}$. Azimuthal correlations are stronger at larger transverse momenta. These are well described in perturbative QCD at next-to-leading order in the strong coupling constant, except at large azimuthal differences where contributions with low transverse momentum are significant.

We report the observation of the doubly strange b baryon Omegab- in the decay channel Omegab(-)-->J/psiOmega-, with J/psi-->mu+mu(-) and Omega(-)-->LambdaK(-)-->(ppi-)K-, in pp collisions at sqrt[s]=1.96 TeV. Using approximately 1.3 fb(-1) of data collected with the D0 detector at the Fermilab Tevatron Collider, we observe 17.8+/-4.9(stat)+/-0.8(syst) Omegab- signal events at a mass of 6.165+/-0.010(stat)+/-0.013(syst) GeV. The significance of the observed signal is 5.4sigma, corresponding to a probability of 6.7 x 10(-8) of it arising from a background fluctuation.

We present a measurement of the W boson mass in W-->e(nu) decays using 1 fb-1 of data collected with the D0 detector during Run II of the Fermilab Tevatron collider. With a sample of 499830 W-->e(nu) candidate events, we measure M(W)=80.401+/-0.043 GeV. This is the most precise measurement from a single experiment.

We report the results of a search for associated production of charginos and neutralinos using a data set corresponding to an integrated luminosity of 2.3 fb−1 collected with the DØ experiment during Run II of the Tevatron proton–antiproton collider. Final states containing three charged leptons and missing transverse energy are probed for a signal from supersymmetry with four dedicated trilepton event selections. No evidence for a signal is observed, and we set limits on the product of production cross section and leptonic branching fraction. Within minimal supergravity, these limits translate into bounds on m0 and m1/2 that are well beyond existing limits.

We report on the test beam results and calibration methods using high energy electrons, pions and muons with the CMS forward calorimeter (HF). The HF calorimeter covers a large pseudorapidity region ( $3\leq|\eta|\leq5$ ), and is essential for a large number of physics channels with missing transverse energy. It is also expected to play a prominent role in the measurement of forward tagging jets in weak boson fusion channels in Higgs production. The HF calorimeter is based on steel absorber with embedded fused-silica-core optical fibers where Cherenkov radiation forms the basis of signal generation. Thus, the detector is essentially sensitive only to the electromagnetic shower core and is highly non-compensating (e/h≈5). This feature is also manifest in narrow and relatively short showers compared to similar calorimeters based on ionization. The choice of fused-silica optical fibers as active material is dictated by its exceptional radiation hardness. The electromagnetic energy resolution is dominated by photoelectron statistics and can be expressed in the customary form as $\frac{a}{\sqrt{E}}\oplus{b}$ . The stochastic term a is 198% and the constant term b is 9%. The hadronic energy resolution is largely determined by the fluctuations in the neutral pion production in showers, and when it is expressed as in the electromagnetic case, a = 280% and b = 11%.

We present a measurement of the muon charge asymmetry from W boson decays using 0.3 fb−1 of data collected at s=1.96 GeV between 2002 and 2004 with the D0 detector at the Fermilab Tevatron pp¯ Collider. We compare our findings with expectations from next-to-leading-order calculations performed using the CTEQ6.1M and MRST04 NLO parton distribution functions. Our findings can be used to constrain future parton distribution function fits.Received 27 September 2007DOI:https://doi.org/10.1103/PhysRevD.77.011106©2008 American Physical Society

We report the results of a search for a heavy neutral gauge boson Z′ decaying into the dielectron final state using data corresponding to an integrated luminosity of 5.4 fb−1 collected by the D0 experiment at the Fermilab Tevatron Collider. No significant excess above the standard model prediction is observed in the dielectron invariant-mass spectrum. We set 95σ(pp¯→Z′)×BR(Z′→ee) depending on the dielectron invariant mass. These cross section limits are used to determine lower mass limits for Z′ bosons in a variety of models. For the sequential standard model Z′ boson a lower mass limit of 1023 GeV is obtained.

We use higher-order quantum chromodynamics calculations to extract the mass of the top quark from the ttbar cross section measured in the lepton+jets channel in ppbar collisions at sqrt(s)=1.96 TeV using 5.3 fb-1 of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron Collider. The extracted top quark pole mass and MSbar mass are compared to the current Tevatron average top quark mass obtained from direct measurements.

We determine the strong coupling constant ${\ensuremath{\alpha}}_{s}$ and its energy dependence from the ${p}_{T}$ dependence of the inclusive jet cross section in $p\overline{p}$ collisions at $\sqrt{s}=1.96\text{ }\text{ }\mathrm{TeV}$. The strong coupling constant is determined over the transverse momentum range $50&lt;{p}_{T}&lt;145\text{ }\text{ }\mathrm{GeV}$. Using perturbative QCD calculations to order $\mathcal{O}({\ensuremath{\alpha}}_{s}^{3})$ combined with $\mathcal{O}({\ensuremath{\alpha}}_{s}^{4})$ contributions from threshold corrections, we obtain ${\ensuremath{\alpha}}_{s}({M}_{Z})={0.1161}_{\ensuremath{-}0.0048}^{+0.0041}$. This is the most precise result obtained at a hadron-hadron collider.

We present a measurement of the elastic differential cross section $d\ensuremath{\sigma}(p\overline{p}\ensuremath{\rightarrow}p\overline{p})/dt$ as a function of the four-momentum-transfer squared $t$. The data sample corresponds to an integrated luminosity of $\ensuremath{\approx}31\text{ }\text{ }{\mathrm{nb}}^{\ensuremath{-}1}$ collected with the D0 detector using dedicated Tevatron $p\overline{p}$ Collider operating conditions at $\sqrt{s}=1.96\text{ }\text{ }\mathrm{TeV}$ and covers the range $0.26&lt;|t|&lt;1.2\text{ }\text{ }{\mathrm{GeV}}^{2}$. For $|t|&lt;0.6\text{ }\text{ }{\mathrm{GeV}}^{2}$, $d\ensuremath{\sigma}/dt$ is described by an exponential function of the form $A{e}^{\ensuremath{-}b|t|}$ with a slope parameter $b=16.86\ifmmode\pm\else\textpm\fi{}0.10(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.20(\mathrm{syst})\text{ }\text{ }{\mathrm{GeV}}^{\ensuremath{-}2}$. A change in slope is observed at $|t|\ensuremath{\approx}0.6\text{ }\text{ }{\mathrm{GeV}}^{2}$, followed by a more gradual $|t|$ dependence with increasing values of $|t|$.

Using 7.3 pb-1 of ppbar collisions collected by the D0 detector at the Fermilab Tevatron, we measure the distribution of the variable \phistar, which probes the same physical effects as the Z/gamma* boson transverse momentum, but is less susceptible to the effects of experimental resolution and efficiency. A QCD prediction is found to describe the general features of the \phistar distribution, but is unable to describe its detailed shape or dependence on boson rapidity. A prediction that includes a broadening of transverse momentum for small values of the parton momentum fraction is strongly disfavored.

We present a measurement of the inclusive top quark pair production cross section in \ppbar collisions at (\sqrt{s}=1.96) TeV utilizing data corresponding to an integrated luminosity of \lumi\ collected with the D0 detector at the Fermilab Tevatron Collider. We consider final states containing one high-$p_{T}$ isolated electron or muon and at least two jets, and we perform three analyses: one exploiting specific kinematic features of \ttbar events, the second using $b$-jet identification, and the third using both techniques to separate \ttbar\ signal from background. In the third case, we determine simultaneously the $t\bar{t}$ cross section and the ratio of the production rates of $W$+heavy flavor jets and $W$+light flavor jets, which reduces the impact of the systematic uncertainties related to the background estimation. Assuming a top quark mass of 172.5 GeV, we obtain $\sigma_{t\bar{t}} = 7.78^{+0.77}_{-0.64} $ pb. This result agrees with predictions of the standard model.

We present a measurement of the ttbar production cross section sigma(ttbar) in ppbar collisions at sqrt{s} = 1.96 TeV using 5.4 fb-1 of integrated luminosity collected with the D0 detector. We consider final states with at least two jets and two leptons (ee, emu, mumu), and events with one jet for the the emu final state as well. The measured cross section is sigma(ttbar)= 7.36 +0.90-0.79 (stat + syst) pb. This result combined with the cross section measurement in the lepton + jets final state yields sigma(ttbar)=7.56 +0.63-0.56 (stat + syst) pb, which agrees with the standard model expectation. The relative precision of 8% of this measurement is comparable to the latest theoretical calculations.

We present a measurement of the electron charge asymmetry in $p\bar{p}\rightarrow W+X \rightarrow e\nu +X$ events at a center-of-mass energy of 1.96 TeV, using data corresponding to 9.7~fb$^{-1}$ of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider. The asymmetry is measured as a function of the electron pseudorapidity and is presented in five kinematic bins based on the electron transverse energy and the missing transverse energy in the event. The measured asymmetry is compared with next-to-leading-order predictions in perturbative quantum chromodynamics and provides accurate information for the determination of parton distribution functions of the proton. This is the most precise lepton charge asymmetry measurement to date.

We measure the mass of the top quark in lepton+jets final states using the full sample of $p\bar{p}$ collision data collected by the D0 experiment in Run~II of the Fermilab Tevatron Collider at $\sqrt s=1.96~$TeV, corresponding to $9.7~{\rm fb}^{-1}$ of integrated luminosity. We use a matrix element technique that calculates the probabilities for each event to result from $t\bar t$ production or background. The overall jet energy scale is constrained in situ by the mass of the $W$ boson. We measure $m_t=174.98\pm0.76~{\rm GeV}$. This constitutes the most precise single measurement of the top-quark mass.

We measure the inclusive single muon charge asymmetry and the like-sign dimuon charge asymmetry in pp collisions using the full data set of 10.4 fb -1 collected with

We report evidence for the simultaneous production of $J/\psi$ and $\Upsilon$ mesons in 8.1 fb$^{-1}$ of data collected at $\sqrt{s}=$1.96 TeV by the D0 experiment at the Fermilab $p \bar p$ Tevatron Collider. Events with these characteristics are expected to be produced predominantly by gluon-gluon interactions. In this analysis, we extract the effective cross section characterizing the initial parton spatial distribution, $\sigma_{eff}=2.2\pm 0.7\mbox{(stat)} \pm 0.9 \mbox{(syst)} ~\mbox{mb}$.

We present a search for charged Higgs bosons in decays of pair-produced top quarks using $109.2\ifmmode\pm\else\textpm\fi{}5.8{\mathrm{pb}}^{\ensuremath{-}1}$ of data recorded from $p\overline{p}$ collisions at $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8\mathrm{TeV}$ by the D0 detector during 1992--1996 at the Fermilab Tevatron. No evidence is found for charged Higgs production, and most parts of the $[{M}_{{H}^{+}},\mathrm{tan}\ensuremath{\beta}]$ parameter space where the decay $t\ensuremath{\rightarrow}{H}^{+}b$ has a branching fraction close to or larger than that for $t\ensuremath{\rightarrow}{W}^{+}b$ are excluded at $95%$ confidence level. Assuming ${m}_{t}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}175\mathrm{GeV}$ and $\ensuremath{\sigma}(p\overline{p}\ensuremath{\rightarrow}t\overline{t})\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}5.5\mathrm{pb}$, for ${M}_{{H}^{+}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}60\mathrm{GeV}$, we exclude $\mathrm{tan}\ensuremath{\beta}&lt;0.97$ and $\mathrm{tan}\ensuremath{\beta}&gt;40.9$.

We report a measurement of the top quark mass using six candidate events for the process $p\overline{p}\ensuremath{\rightarrow}t\overline{t}+\stackrel{\ensuremath{\rightarrow}}{X}{l}^{+}\ensuremath{\nu}{\mathrm{bl}}^{\ensuremath{-}}\overline{\ensuremath{\nu}}\overline{b}+X$, observed in the D0 experiment at the Fermilab $p\overline{p}$ collider. Using maximum likelihood fits to the dynamics of the decays, we measure a mass for the top quark of ${m}_{t}=168.4\ifmmode\pm\else\textpm\fi{}12.3(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}3.6(\mathrm{syst}) \mathrm{Gev}$. We combine this result with our previous measurement in the $t\overline{t}\ensuremath{\rightarrow}l+\mathrm{jets}$ channel to obtain ${m}_{t}=172.1\ifmmode\pm\else\textpm\fi{}7.1 \mathrm{GeV}$ as the best value of the mass of the top quark measured by D0.

We report a new measurement of the pseudorapidity (eta) and transverse-energy ( E(T)) dependence of the inclusive jet production cross section in pp(macro) collisions at square root of s = 1.8 TeV using 95 pb(-1) of data collected with the D0 detector at the Fermilab Tevatron. The differential cross section d(2)sigma/(dE(T)d eta) is presented up to eta = 3, significantly extending previous measurements. The results are in good overall agreement with next-to-leading order predictions from QCD and indicate a preference for certain parton distribution functions.

We report a new measurement of the cross section for the production of isolated photons with transverse energies ( E(gamma)(T)) above 10 GeV and pseudorapidities |eta|<2.5 in p&pmacr; collisions at sqrt[s] = 1.8 TeV. The results are based on a data sample of 107.6 pb(-1) recorded during 1992-1995 with the D0 detector at the Fermilab Tevatron collider. The background, predominantly from jets which fragment to neutral mesons, was estimated using the longitudinal shower shape of photon candidates in the calorimeter. The measured cross section is in good agreement with the next-to-leading order QCD calculation for E(gamma)(T) greater, similar36 GeV.

A search for pair production of doubly-charged Higgs bosons in the process p pbar to H++H-- to mu+mu+mu-mu- is performed with the D0 Run II detector at the Fermilab Tevatron. The analysis is based on a sample of inclusive di-muon data collected at an energy of sqrt{s}=1.96 TeV, corresponding to an integrated luminosity of 113 pb-1. In the absence of a signal, 95 % confidence level mass limits of M(H++L)>118.4 GeV/c2 and M(H++R)>98.2 GeV/c2 are set for left-handed and right-handed doubly-charged Higgs bosons, respectively, assuming 100% branching into muon pairs.

We present a measurement of the electron charge asymmetry in pp[over ]-->W+X-->enu+X events at a center of mass energy of 1.96 TeV using 0.75 fb(-1) of data collected with the D0 detector at the Fermilab Tevatron Collider. The asymmetry is measured as a function of the electron transverse momentum and pseudorapidity in the interval (-3.2, 3.2) and is compared with expectations from next-to-leading order calculations in perturbative quantum chromodynamics. These measurements will allow more accurate determinations of the proton parton distribution functions.

We present a search for the pair production of scalar top quarks, t˜, using 995 pb−1 of data collected in pp¯ collisions with the DØ detector at the Fermilab Tevatron Collider at s=1.96TeV. Both scalar top quarks are assumed to decay into a charm quark and a neutralino (χ˜10), where χ˜10 is the lightest supersymmetric particle. This leads to a final state with two acoplanar charm jets and missing transverse energy. We find the yield of such events to be consistent with the standard model expectation, and exclude sets of t˜ and χ˜10 masses at the 95% C.L. that substantially extend the domain excluded by previous searches.

We search for long-lived charged massive particles using $1.1\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of data collected by the D0 detector at the Fermilab Tevatron $p\overline{p}$ 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).

We search for the production of a heavy W′ gauge boson that decays to third generation quarks in 0.9 fb−1 of pp¯ collisions at s=1.96 TeV, collected with the D0 detector at the Fermilab Tevatron collider. We find no significant excess in the final-state invariant mass distribution and set upper limits on the production cross section times branching fraction. For a left-handed W′ boson with SM couplings, we set a lower mass limit of 731 GeV. For right-handed W′ bosons, we set lower mass limits of 739 GeV if the W′ boson decays to both leptons and quarks and 768 GeV if the W′ boson decays only to quarks. We also set limits on the coupling of the W′ boson to fermions as a function of its mass.Received 21 March 2008DOI:https://doi.org/10.1103/PhysRevLett.100.211803©2008 American Physical Society

We report on a search for large extra dimensions in a data sample of approximately 1 fb−1 of p¯p collisions at √s=1.96 TeV. We investigate Kaluza-Klein graviton production with a photon and missing transverse energy in the final state. At the 95% C.L. we set limits on the fundamental mass scale MD from 884 to 778 GeV for two to eight extra dimensions.Received 14 March 2008DOI:https://doi.org/10.1103/PhysRevLett.101.011601©2008 American Physical Society

We report on a first search for production of the lightest neutral $CP$-even Higgs boson ($h$) in the next-to-minimal supersymmetric standard model, where $h$ decays to a pair of neutral pseudoscalar Higgs bosons ($a$), using $4.2\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of data recorded with the D0 detector at Fermilab. The $a$ bosons are required to either both decay to ${\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ or one to ${\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ and the other to ${\ensuremath{\tau}}^{+}{\ensuremath{\tau}}^{\ensuremath{-}}$. No significant signal is observed, and we set limits on its production as functions of ${M}_{a}$ and ${M}_{h}$.

We present a search for flavor changing neutral currents via quark-gluon couplings in a sample of single top quark final states corresponding to 2.3 fb^-1 of integrated luminosity collected with the D0 detector at the Fermilab Tevatron Collider. We select events containing a single top quark candidates with an additional jet, and obtain separation between signal and background using Bayesian neural networks. We find consistency between background expectation and observed data, and set limits on flavor changing neutral current gluon couplings of the top quark to up quarks (tgu) and charm quarks (tgc). The cross section limits at the 95% C.L. are sigma_tgu<0.20pb and sigma_tgc<0.27pb. These correspond to limits on the top quark decay branching fractions of B(t->gu)<2.0*10^-4 and B(t->gc)<3.9*10^-3.

We present a new measurement of the Z/γ∗ transverse momentum distribution in the range 0–330 GeV, in proton–antiproton collisions at s=1.96TeV. The measurement uses 0.97 fb−1 of integrated luminosity recorded by the D0 experiment and is the first using the Z/γ∗→μ+μ−+X channel at this center-of-mass energy. This is also the first measurement of the Z/γ∗ transverse momentum distribution that presents the result at the level of particles entering the detector, minimizing dependence on theoretical models. As any momentum of the Z/γ∗ in the plane transverse to the incoming beams must be balanced by some recoiling system, primarily the result of QCD radiation in the initial state, this variable is an excellent probe of the underlying process. Tests of the predictions of QCD calculations and current event generators show they have varied success in describing the data. Using this measurement as an input to theoretical predictions will allow for a better description of hadron collider data and hence it will increase experimental sensitivity to rare signals.

We present a search for the production of a heavy gauge boson, W′, that decays to third-generation quarks, by D0 Collaboration in pp¯ collisions at s=1.96TeV. We set 95% confidence level upper limits on the production cross section times branching fraction. For the first time, we set limits for arbitrary combinations of left- and right-handed couplings of the W′ boson to fermions. For couplings with the same strength as for the standard model W boson, we set the following limits, assuming that there are right-handed neutrinos νR for all three generations with M(W′)>m(νR): M(W′)>863GeV for purely left-handed couplings, M(W′)>885GeV for purely right-handed couplings, and M(W′)>916GeV if both left- and right-handed couplings are present. The limit for right-handed couplings improves for M(W′)<m(νR) to M(W′)>890GeV.

We present a measurement of the ratio of top quark branching fractions R = B(t -> Wb)/B(t -> Wq), where q can be a d, s or b quark, in the lepton+jets and dilepton ttbar final states. The measurement uses data from 5.4 fb-1 of ppbar collisions collected with the D0 detector at the Fermilab Tevatron Collider. We measure R = 0.90 +/- 0.04, and we extract the CKM matrix element |Vtb| as |Vtb| = 0.95 +/- 0.02, assuming unitarity of the 3x3 CKM matrix.

We present a measurement of the average value of a new observable at hadron colliders that is sensitive to QCD dynamics and to the strong coupling constant, while being only weakly sensitive to parton distribution functions. The observable measures the angular correlations of jets and is defined as the number of neighboring jets above a given transverse momentum threshold which accompany a given jet within a given distance Delta-R in the plane of rapidity and azimuthal angle. The ensemble average over all jets in an inclusive jet sample is measured and the results are presented as a function of transverse momentum of the inclusive jets, in different regions of Delta-R and for different transverse momentum requirements for the neighboring jets. The measurement is based on a data set corresponding to an integrated luminosity of 0.7 fb-1 collected with the D0 detector at the Fermilab Tevatron Collider in pp-bar collisions at sqrt(s)=1.96 The results are well described by a perturbative QCD calculation in next-to-leading order in the strong coupling constant, corrected for non-perturbative effects. From these results, we extract the strong coupling and test the QCD predictions for its running over a range of momentum transfers of 50-400 GeV.

We report the combination of recent measurements of the helicity of the $W$ boson from top quark decay by the CDF and D0 collaborations, based on data samples corresponding to integrated luminosities of $2.7--5.4\text{ }\text{ }\mathrm{f}{\mathrm{b}}^{\ensuremath{-}1}$ of $p\overline{p}$ collisions collected during Run II of the Fermilab Tevatron collider. Combining measurements that simultaneously determine the fractions of $W$ bosons with longitudinal (${f}_{0}$) and right-handed (${f}_{+}$) helicities, we find ${f}_{0}=0.722\ifmmode\pm\else\textpm\fi{}0.081[\ifmmode\pm\else\textpm\fi{}0.062(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.052(\mathrm{syst})]$ and ${f}_{+}=\ensuremath{-}0.033\ifmmode\pm\else\textpm\fi{}0.046[\ifmmode\pm\else\textpm\fi{}0.034(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.031(\mathrm{syst})]$. Combining measurements where one of the helicity fractions is fixed to the value expected in the standard model, we find ${f}_{0}=0.682\ifmmode\pm\else\textpm\fi{}0.057[\ifmmode\pm\else\textpm\fi{}0.035(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.046(\mathrm{syst})]$ for fixed ${f}_{+}$ and ${f}_{+}=\ensuremath{-}0.015\ifmmode\pm\else\textpm\fi{}0.035[\ifmmode\pm\else\textpm\fi{}0.018(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.030(\mathrm{syst})]$ for fixed ${f}_{0}$. The results are consistent with standard model expectations.

Using data corresponding to an integrated luminosity of 1.3 fb^-1, we observe a narrow mass state decaying into Upsilon(1S)+gamma, where the Upsilon(1S) meson is detected by its decay into a pair of oppositely charged muons, and the photon is identified through its conversion into an electron-positron pair. The significance of this observation is 5.6 standard deviations. The mass of the state is centered at 10.551 \pm 0.014 (stat.) \pm 0.017 (syst.) GeV/c^2, which is consistent with that of the state recently observed by the ATLAS Collaboration.

We present a measurement of the time-integrated flavor-specific semileptonic charge asymmetry in the decays of ${B}_{s}^{0}$ mesons that have undergone flavor mixing, ${a}_{\mathrm{sl}}^{s}$, using ${B}_{s}^{0}({\overline{B}}_{s}^{0})\ensuremath{\rightarrow}{D}_{s}^{\ensuremath{\mp}}{\ensuremath{\mu}}^{\ifmmode\pm\else\textpm\fi{}}X$ decays, with ${D}_{s}^{\ensuremath{\mp}}\ensuremath{\rightarrow}\ensuremath{\phi}{\ensuremath{\pi}}^{\ensuremath{\mp}}$ and $\ensuremath{\phi}\ensuremath{\rightarrow}{K}^{+}{K}^{\ensuremath{-}}$, using $10.4\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of proton-antiproton collisions collected by the D0 detector during Run II at the Fermilab Tevatron Collider. A fit to the difference between the time-integrated ${D}_{s}^{\ensuremath{-}}$ and ${D}_{s}^{+}$ mass distributions of the ${B}_{s}^{0}$ and ${\overline{B}}_{s}^{0}$ candidates yields the flavor-specific asymmetry ${a}_{\mathrm{sl}}^{s}=[\ensuremath{-}1.12\ifmmode\pm\else\textpm\fi{}0.74(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.17(\mathrm{syst})]%$, which is the most precise measurement and in agreement with the standard model prediction.

We present measurements of lepton ($\ensuremath{\ell}$) angular distributions in top-quark ($t$) pair production and $t\overline{t}\ensuremath{\rightarrow}{W}^{+}b{W}^{\ensuremath{-}}\overline{b}\ensuremath{\rightarrow}{\ensuremath{\ell}}^{+}\ensuremath{\nu}b{\ensuremath{\ell}}^{\ensuremath{-}}\overline{\ensuremath{\nu}}\overline{b}$ decays produced in $p\overline{p}$ collisions at a center-of-mass energy of $\sqrt{s}=1.96\text{ }\text{ }\mathrm{TeV}$, where $\ensuremath{\ell}$ is an electron or muon. Using data corresponding to an integrated luminosity of $5.4\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$, collected with the D0 detector at the Fermilab Tevatron Collider, we measure for the first time the leptonic forward-backward asymmetry in dilepton final states and obtain ${A}_{\mathrm{FB}}^{\ensuremath{\ell}}=(5.8\ifmmode\pm\else\textpm\fi{}5.1(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}1.3(\mathrm{syst}))%$, corrected for detector acceptance. This is compared to the standard model prediction of ${A}_{\mathrm{FB}}^{\ensuremath{\ell}}(\mathrm{predicted})=(4.7\ifmmode\pm\else\textpm\fi{}0.1)%$. A deviation from the standard model prediction as previously seen in a D0 measurement based on the analysis of the $\ensuremath{\ell}+\mathrm{\text{jets}}$ final state is not observed in these dilepton final states. The two results differ from each other by 1.4 standard deviations and are combined to obtain ${A}_{\mathrm{FB}}^{\ensuremath{\ell}}=(11.8\ifmmode\pm\else\textpm\fi{}3.2)%$. Furthermore, we present a first study of the top-quark polarization.

We determine the fraction of events with double parton (DP) scattering in a single ppbar collision at sqrt{s}=1.96 TeV in samples of photon + 3 jet and photon + b/c jet + 2 jet events collected with the D0 detector and corresponding to an integrated luminosity of about 8.7 fb^{-1}. The DP fractions and effective cross sections (sigma_eff) are measured for both event samples using the same kinematic selections. The measured DP fractions range from 0.21 to 0.17, with effective cross sections in the photon + 3 jet and photon + b/c jet + 2 jet samples of sigma_eff^incl = 12.7 +- 0.2 (stat) +- 1.3 (syst) mb and sigma_eff^HF = 14.6 +- 0.6 (stat) +- 3.2 (syst) mb, respectively.

We present a study of the inclusive production of the X(4140) state with the decay to the J/ψϕ final state in hadronic collisions. Based on 10.4 fb^{-1} of pp[over ¯] collision data collected by the D0 experiment at the Fermilab Tevatron collider, we report the first evidence for the prompt production of an X(4140) state and find the fraction of X(4140) events originating from b hadrons to be f_{b}=0.39±0.07(stat)±0.10(syst). The ratio of the nonprompt X(4140) production rate to the B_{s}^{0} yield in the same channel is R=0.19±0.05(stat)±0.07(syst). The values of the mass M=4152.5±1.7(stat)_{-5.4}^{+6.2}(syst) MeV and width Γ=16.3±5.6(stat)±11.4(syst) MeV are consistent with previous measurements.

The production of top quark-antiquark pair events in $p\bar{p}$ collisions at $\sqrt{s}=1.96$ TeV is studied as a function of the transverse momentum and absolute value of the rapidity of the top quarks as well as of the invariant mass of the $t\bar{t}$ pair. We select events containing an isolated lepton, a large imbalance in transverse momentum, and four or more jets with at least one jet identified to originate from a $b$ quark. The data sample corresponds to 9.7 fb$^{-1}$ of integrated luminosity recorded with the D0 detector during Run II of the Fermilab Tevatron Collider. Observed differential cross sections are consistent with standard model predictions.

We present a measurement of the $t\overline{t}$ production cross section in $p\overline{p}$ collisions at $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8\mathrm{TeV}$ by the D0 experiment at the Fermilab Tevatron. The measurement is based on data from an integrated luminosity of approximately $125{\mathrm{pb}}^{\ensuremath{-}1}$ accumulated during the 1992--1996 collider run. We observe 39 $t\overline{t}$ candidate events in the dilepton and $\mathrm{lepton}+\mathrm{jets}$ decay channels with an expected background of $13.7\ifmmode\pm\else\textpm\fi{}2.2$ events. For a top quark mass of $173.3\mathrm{GeV}{/c}^{2}$, we measure the $t\overline{t}$ production cross section to be $5.5\ifmmode\pm\else\textpm\fi{}1.8\mathrm{pb}$.

We report on measurements on inclusive cross sections times branching fractions into electrons for W and Z bosons produced in pp¯ collisions at s=1.8TeV. From an integrated luminosity of 84.5 pb−1 recorded in 1994–1995 using the DØ detector at the Fermilab Tevatron, we determine σ(pp¯→W+X)×B(W→eν)=2310±10(stat)±50(syst)±100(lum)pb and σ(pp¯→Z+X)×B(Z→ee)=221±3(stat)±4(syst)±10(lum)pb. From these, we derive σ(pp¯→W+X)×B(W→eν)/σ(pp¯→Z+X)×B(Z→ee)=10.43±0.15(stat)±0.20(syst)±0.10(NLO), B(W→eν)=0.1044±0.0015(stat)±0.0020(syst)±0.0017(theory)±0.0010(NLO), and ΓW=2.169±0.031(stat)±0.042(syst)±0.041(theory)±0.022(NLO)GeV. We use the latter to set a 95% confidence level upper limit on the partial decay width of the W boson into nonstandard model final states, ΓWinv, of 0.213 GeV. Combining these results with those from the 1992–1993 data gives σ(pp¯→W+X)×B(W→eν)/σ(pp¯→Z+X)×B(Z→ee)=10.51±0.25, ΓW=2.152±0.066GeV, and a 95% C.L. upper limit on ΓWinv of 0.191 GeV. Using a sample with a luminosity of 505 nb−1 taken at s=630GeV, we measure σ(pp¯→W+X)×B(W→eν)=658±67pb. Received 15 June 1999DOI:https://doi.org/10.1103/PhysRevD.61.072001©2000 American Physical Society

We present a measurement of the Drell-Yan cross section at high dielectron invariant mass using $120\mathrm{pb}{}^{\ensuremath{-}1}$ of data collected in $p\overline{p}$ collisions at $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8\mathrm{TeV}$ by the D0 Collaboration during 1992--1996. No deviation from standard model expectations is observed. We use the data to set limits on the quark-electron compositeness scale. The $95%$ confidence level lower limits on the compositeness scale vary between 3.3 and 6.1 TeV depending on the assumed form of the effective contact interaction.

The DØ detector is used to study pp̄ collisions at the 1800 and 630 GeV center-of-mass energies available at the Fermilab Tevatron. To measure jets, the detector uses a sampling calorimeter composed of uranium and liquid argon as the passive and active media, respectively. Understanding the jet energy calibration is not only crucial for precision tests of QCD, but also for the measurement of particle masses and the determination of physics backgrounds associated with new phenomena. This paper describes the energy calibration of jets observed with the DØ detector at the two pp̄ center-of-mass energies in the transverse energy and pseudorapidity range ET>8 GeV and |η|<3.

Using the D0 detector at the 1.8 TeV $\overline{p}p$ Fermilab Tevatron collider, we have measured the inclusive dijet mass spectrum in the central pseudorapidity region $|{\ensuremath{\eta}}_{\mathrm{jet}}|&lt;1.0$ for dijet masses greater than $200\mathrm{GeV}{/c}^{2}$. We have also measured the ratio of spectra $\ensuremath{\sigma}(|{\ensuremath{\eta}}_{\mathrm{jet}}|&lt;0.5)/\ensuremath{\sigma}(0.5&lt;|{\ensuremath{\eta}}_{\mathrm{jet}}|&lt;1.0)$. The order ${\ensuremath{\alpha}}_{s}^{3}$ quantum chromodynamics predictions are in good agreement with the data and we rule out models of quark compositeness with a contact interaction scale $&lt;2.4\mathrm{TeV}$ at the $95%$ confidence level.

We have made a precise measurement of the central inclusive jet cross section at sqrt(s) = 1.8 TeV. The measurement is based on an integrated luminosity of 92 pb-1 collected at the Fermilab Tevatron pbar-p Collider with the D-Zero detector. The cross section, reported as a function of jet transverse energy (ET >= 60 GeV) in the pseudorapidity interval |eta| <= 0.5, is in good agreement with predictions from next-to-leading order quantum chromodynamics.

We present a search for electroweak production of single top quarks in ~90 pb^-1 of data collected with the DZero detector at the Fermilab Tevatron collider. Using arrays of neural networks to separate signals from backgrounds, we set upper limits on the cross sections of 17 pb for the s-channel process ppbar->tb+X, and 22 pb for the t-channel process ppbar->tqb+X, both at the 95% confidence level.

The results based on 1992-95 data (Run 1) from the CDF and DO experiments on the measurements of the W boson mass and width are presented, along with the combined results. We report a Tevatron collider average M_W = 80.456 +- 0.059 GeV. We also report the Tevatron collider average of the directly measured W boson width Gamma_W = 2.115 +- 0.105 GeV. We describe a new joint analysis of the direct W mass and width measurements. Assuming the validity of the standard model, we combine the directly measured W boson width with the width extracted from the ratio of W and Z boson leptonic partial cross sections. This combined result for the Tevatron is Gamma_W = 2.135 +- 0.050 GeV. Finally, we use the measurements of the direct total W width and the leptonic branching ratio to extract the leptonic partial width Gamma(W -> e nu) = 224 +- 13 MeV.

We present the results of a search for the flavor-changing neutral current decay B0s→μ+μ− using a data set with integrated luminosity of 240 pb−1 of p¯p collisions at √s=1.96 TeV collected with the D0 detector in run II of the Fermilab Tevatron collider. We find the upper limit on the branching fraction to be B(B0s→μ+μ−)≤5.0×10−7 at the 95% C.L. assuming no contributions from the decay B0d→μ+μ− in the signal region. This limit is the most stringent upper bound on the branching fraction B0s→μ+μ− to date.Received 15 October 2004DOI:https://doi.org/10.1103/PhysRevLett.94.071802©2005 American Physical Society

We examine properties of tt¯ candidate events in lepton + jets final states to establish the helicities of W bosons in t→W+b decays. Our analysis is based on a direct calculation of a probability density for each event to correspond to a tt¯ final state, as a function of the helicity of the W boson. Using the 125 events/pb of data collected by the DØ experiment at the Fermilab Tevatron pp¯ Collider at s=1.8TeV, we obtain a longitudinal helicity fraction F0=0.56±0.31, consistent with the prediction of F0=0.70 from the standard model.

First experimental results are presented from a search for events with a rapidity gap between jets. The D0 detector was used to examine events produced by the Fermilab Tevatron pp\ifmmode\bar\else\textasciimacron\fi{} collider at \ensuremath{\surd}s =1.8 TeV. The fraction of events with an observed rapidity gap between the two highest transverse energy (${\mathit{E}}_{\mathit{T}}$) jets is measured as a function of the pseudorapidity separation between the jet edges (\ensuremath{\Delta}${\mathrm{\ensuremath{\eta}}}_{\mathit{c}}$). An upper limit at the 95% confidence level of 1.1\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}2}$ is obtained on the fraction of events with non particles between the jets, for events with \ensuremath{\Delta}${\mathrm{\ensuremath{\eta}}}_{\mathit{c}}$&gt;3 and jet ${\mathit{E}}_{\mathit{T}}$ greater than 30 GeV.

We present the results of a search for the production of new particles decaying into two jets in $\overline{p}p$ collisions at $\sqrt{s}=1.8\mathrm{TeV},$ using the D\O{} 1992--1995 data set corresponding to ${109\mathrm{}\mathrm{pb}}^{\ensuremath{-}1}.$ We exclude at the 95% confidence level the production of excited quarks ${(q}^{*})$ with masses below 775 GeV/${c}^{2},$ the most restrictive limit to date. We also exclude standard-model-like ${W}^{\ensuremath{'}}$ ${(Z}^{\ensuremath{'}})$ bosons with masses between 300 and 800 GeV/${c}^{2}$ (400 and 640 GeV/${c}^{2}).$ A ${W}^{\ensuremath{'}}$ boson with mass $&lt;786\mathrm{GeV}{/c}^{2}$ has been excluded by previous measurements, and our lower limit is therefore the most stringent to date.

We present a measurement of the top quark mass with the matrix element method in the $\mathrm{\text{lepton}}+\mathrm{\text{jets}}$ final state. As the energy scale for calorimeter jets represents the dominant source of systematic uncertainty, the matrix element likelihood is extended by an additional parameter, which is defined as a global multiplicative factor applied to the standard energy scale. The top quark mass is obtained from a fit that yields the combined statistical and systematic jet energy scale uncertainty. Using a data set of $0.4\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ taken with the D0 experiment at Run II of the Fermilab Tevatron Collider, the mass of the top quark is measured using topological information to be: ${m}_{\mathrm{top}}^{\ensuremath{\ell}+\mathrm{jets}}(\mathrm{topo})={169.2}_{\ensuremath{-}7.4}^{+5.0}(\mathrm{stat}+JES{)}_{\ensuremath{-}1.4}^{+1.5}(\mathrm{syst})\text{ }\text{ }\mathrm{GeV}$, and when information about identified $b$ jets is included: ${m}_{\mathrm{top}}^{\ensuremath{\ell}+\mathrm{jets}}(b\mathrm{\text{-tag}})={170.3}_{\ensuremath{-}4.5}^{+4.1}(\mathrm{stat}+\phantom{\rule{0ex}{0ex}}JES{)}_{\ensuremath{-}1.8}^{+1.2}(\mathrm{syst})\text{ }\text{ }\mathrm{GeV}$. The measurements yield a jet energy scale consistent with the reference scale.

We search for the production of single top quarks via flavor-changing neutral current couplings of a gluon to the top quark and a charm ($c$) or up ($u$) quark. We analyze 230 pb$^{-1}$ of lepton + jets data from $\ppbar$ collisions at a center of mass energy of 1.96 TeV collected by the D0 detector at the Fermilab Tevatron Collider. We observe no significant deviation from standard model predictions, and hence set upper limits on the anomalous coupling parameters $\kappacLambda$ and $\kappauLambda$, where $\kappag$ define the strength of $tcg$ and $tug$ couplings, and $\Lambda$ defines the scale of new physics. The limits at 95% C.L. are: $\kappacLambda < 0.15 \rm TeV^{-1}$ and $\kappauLambda < 0.037 \rm TeV^{-1}$.

We report the results of a search for pair production of doubly charged Higgs bosons via pp over-->H++H - - X-->mu+ mu+ mu- mu- X at sqrt s=1.96 TeV. We use a data set corresponding to an integrated luminosity of 1.1 fb(-1) collected from 2002 to 2006 by the D0 detector at the Fermilab Tevatron Collider. In the absence of an excess above the standard model background, lower mass limits of M(H L +/- +/-) >150 GeV/c2 and M(H R+/- +/-) >127 GeV/c2 at 95% C.L. are set, respectively, for left-handed and right-handed doubly charged Higgs bosons assuming a 100% branching ratio into muons.

We present a search for a narrow-width heavy resonance decaying into top quark pairs (X→tt¯) in pp¯ collisions at s=1.96TeV using approximately 0.9fb−1 of data collected with the DØ detector at the Fermilab Tevatron Collider. This analysis considers tt¯ candidate events in the lepton plus jets channel with at least one identified b jet and uses the tt¯ invariant mass distribution to search for evidence of resonant production. We find no evidence for a narrow resonance X decaying to tt¯. Therefore, we set upper limits on σX⋅B(X→tt¯) for different hypothesized resonance masses using a Bayesian approach. For a Topcolor-assisted technicolor model, the existence of a leptophobic Z′ boson with mass MZ′<700GeV and width ΓZ′=0.012MZ′ can be excluded at the 95% C.L.

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.

We present results from a study of p¯p→Wγ+X events utilizing data corresponding to 0.7 fb−1 of integrated luminosity at √s=1.96 TeV collected by the D0 detector at the Fermilab Tevatron Collider. We set limits on anomalous WWγ couplings at the 95% C.L. The one-dimensional 95% C.L. limits are 0.49<κγ<1.51 and −0.12<λγ<0.13. We make the first study of the charge-signed rapidity difference between the lepton and the photon and find it to be indicative of the standard model radiation-amplitude zero in the Wγ system.Received 1 March 2008DOI:https://doi.org/10.1103/PhysRevLett.100.241805©2008 American Physical Society

First measurements of the differential cross sections d;{3}sigma/(dp_{T};{gamma}dy;{gamma}dy;{jet}) for the inclusive production of a photon in association with a heavy quark (b, c) jet are presented, covering photon transverse momenta 30<p_{T};{gamma}<150 GeV, photon rapidities |y;{gamma}|<1.0, jet rapidities |y;{jet}|<0.8, and jet transverse momenta p_{T};{jet}>15 GeV. The results are based on an integrated luminosity of 1 fb;{-1} in pp[over ] collisions at sqrt[s]=1.96 TeV recorded with the D0 detector at the Fermilab Tevatron Collider. The results are compared with next-to-leading order perturbative QCD predictions.

Extensive measurements have been made with pions, electrons and muons on four production wedges of the compact muon solenoid (CMS) hadron barrel (HB) calorimeter in the H2 beam line at CERN with particle momenta varying from 20 to 300 GeV/c. The time structure of the events was measured with the full chain of preproduction front-end electronics running at 34 MHz. Moving-wire radioactive source data were also collected for all scintillator layers in the HB. The energy dependent time slewing effect was measured and tuned for optimal performance.

We report on a first search for resonant pair production of neutral long-lived particles (NLLP) which each decay to a bb pair, using 3.6 fb(-1) of data recorded with the D0 detector at the Fermilab Tevatron collider. We search for pairs of displaced vertices in the tracking detector at radii in the range 1.6-20 cm from the beam axis. No significant excess is observed above background, and upper limits are set on the production rate in a hidden-valley benchmark model for a range of Higgs boson masses and NLLP masses and lifetimes.

We measure the t¯t production cross section in p¯p collisions at √s=1.96 TeV in the lepton+jets channel. Two complementary methods discriminate between signal and background: b tagging and a kinematic likelihood discriminant. Based on 0.9 fb−1 of data collected by the D0 detector at the Fermilab Tevatron Collider, we measure σt¯t=7.62±0.85 pb, assuming the current world average mt=172.6 GeV. We compare our cross section measurement with theory predictions to determine a value for the top-quark mass of 170±7 GeV.Received 19 March 2008DOI:https://doi.org/10.1103/PhysRevLett.100.192004©2008 American Physical Society

We report the results of a search for pair production of scalar bottom quarks (b˜1) and scalar third-generation leptoquarks (LQ3) in 5.2 fb−1 of pp¯ collisions at the D0 experiment of the Fermilab Tevatron Collider. Scalar bottom quarks are assumed to decay to a neutralino (χ˜10) and a b quark, and we set 95% C.L. lower limits on their production in the (mb˜1, mχ˜10) mass plane such as mb˜1>247 GeV for mχ˜10=0 and mχ˜10>110 GeV for 160<mb˜1<200 GeV. The leptoquarks are assumed to decay to a tau neutrino and a b quark, and we set a 95% C.L. lower limit of 247 GeV on the mass of a charge-1/3 third-generation scalar leptoquark.