Richard Breedon

The preponderance of matter over antimatter in the early Universe, the dynamics of the supernova bursts that produced the heavy elements necessary for life and whether protons eventually decay --- these mysteries at the forefront of particle physics and astrophysics are key to understanding the early evolution of our Universe, its current state and its eventual fate. The Long-Baseline Neutrino Experiment (LBNE) represents an extensively developed plan for a world-class experiment dedicated to addressing these questions. LBNE is conceived around three central components: (1) a new, high-intensity neutrino source generated from a megawatt-class proton accelerator at Fermi National Accelerator Laboratory, (2) a near neutrino detector just downstream of the source, and (3) a massive liquid argon time-projection chamber deployed as a far detector deep underground at the Sanford Underground Research Facility. This facility, located at the site of the former Homestake Mine in Lead, South Dakota, is approximately 1,300 km from the neutrino source at Fermilab -- a distance (baseline) that delivers optimal sensitivity to neutrino charge-parity symmetry violation and mass ordering effects. This ambitious yet cost-effective design incorporates scalability and flexibility and can accommodate a variety of upgrades and contributions. With its exceptional combination of experimental configuration, technical capabilities, and potential for transformative discoveries, LBNE promises to be a vital facility for the field of particle physics worldwide, providing physicists from around the globe with opportunities to collaborate in a twenty to thirty year program of exciting science. In this document we provide a comprehensive overview of LBNE's scientific objectives, its place in the landscape of neutrino physics worldwide, the technologies it will incorporate and the capabilities it will possess.

We present measurements of the bb production cross section and angular correlations using the DØ detector at the Fermilab Tevatron pp Collider operating at s = 1.8 TeV. The b quark production cross section for |yb|<1.0 and pTb>6 GeV/c is extracted from single muon and dimuon data samples. The results agree in shape with the next-to-leading order QCD calculation of heavy flavor production but are greater than the central values of these predictions. The angular correlations between b and b quarks, measured from the azimuthal opening angle between their decay muons, also agree in shape with the next-to-leading order QCD prediction.

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

The Proceedings of the 2011 workshop on Fundamental Physics at the Intensity Frontier. Science opportunities at the intensity frontier are identified and described in the areas of heavy quarks, charged leptons, neutrinos, proton decay, new light weakly-coupled particles, and nucleons, nuclei, and atoms.

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.

We present the general properties of multihadron final states produced by ${e}^{+}{e}^{\ensuremath{-}}$ annihilation at center-of-mass energies from 52 to 57 GeV in the AMY detector at the KEK collider TRISTAN. Global shape, inclusive charged-particle, and particle-flow distributions are presented. Our measurements are compared with QCD+fragmentation models that use either leading-logarithmic parton-shower evolution or QCD matrix elements at the parton level, and either string or cluster fragmentation for hadronization.

Bottom-quark production in $\overline{p}p$ collisions at $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8\mathrm{TeV}$ is studied with $5{\mathrm{pb}}^{\ensuremath{-}1}$ of data collected in 1995 by the D0 detector at the Fermilab Tevatron Collider. The differential production cross section for $b$ jets in the central rapidity region ( $|{y}^{b}|&lt;1$) as a function of jet transverse energy is extracted from a muon-tagged jet sample. Within experimental and theoretical uncertainties, D0 results are found to be higher than, but compatible with, next-to-leading-order QCD predictions.

We report a search for effects of large extra spatial dimensions in pp collisions at a center-of-mass energy of 1.8 TeV with the D0 detector, using events containing a pair of electrons or photons. The data are in good agreement with the expected background and do not exhibit evidence for large extra dimensions. We set the most restrictive lower limits to date, at the 95% C.L. on the effective Planck scale between 1.0 and 1.4 TeV for several formalisms and numbers of extra dimensions.

Results are presented from analyses of jet data produced in pp ¯collisions at ͱsϭ630 and 1800 GeV collected with the DØ detector during the 1994 -1995 Fermilab Tevatron Collider run.We discuss the details of detector calibration, and jet selection criteria in measurements of various jet production cross sections at ͱsϭ630 and 1800 GeV.The inclusive jet cross sections, the dijet mass spectrum, the dijet angular distribu- tions, and the ratio of inclusive jet cross sections at ͱsϭ630 and 1800 GeV are compared to next-to-leading- order QCD predictions.The order ␣ s 3 calculations are in good agreement with the data.We also use the data at ͱsϭ1800 GeV to rule out models of quark compositeness with a contact interaction scale less than 2.2 TeV at the 95% confidence level.

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.

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.

We present a search for large extra dimensions (ED) in pp collisions at a center-of-mass energy of 1.8 TeV using data collected by the DØ detector at the Fermilab Tevatron in 1994-1996. Data corresponding to 78.8+/-3.9 pb(-1) are examined for events with large missing transverse energy, one high-p(T) jet, and no isolated muons. There is no excess observed beyond expectation from the standard model, and we place lower limits on the fundamental Planck scale of 1.0 and 0.6 TeV for 2 and 7 ED, respectively.

We present results of an experimental study of e+e−+ hadrons in the kinematic regime for which the process is interpreted as hadron production in collisions of almost-real photons. The data sample corresponds to an integrated luminosity of 27.5 pb− and covers center-of-mass energies from 55 to 61.4 GeV. We observe more events than expected from the incoherent sum of quark-parton and vector-meson-dominance models, and we give a quantitative explanation of the excess by including the hard scattering of the hadronic constituents of the photons calculated with QCD.

Using data corresponding to an integrated luminosity of $79{\mathrm{pb}}^{\ensuremath{-}1}$, D0 has searched for events containing multiple jets and large missing transverse energy in $p\overline{p}$ collisions at $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8\phantom{\rule{0ex}{0ex}}\mathrm{TeV}$ at the Fermilab Tevatron collider. Observing no significant excess beyond what is expected from the standard model, we set limits on the masses of squarks and gluinos and on the model parameters ${m}_{0}$ and ${m}_{1/2}$, in the framework of the minimal low-energy supergravity models of supersymmetry. For $\mathrm{tan}\ensuremath{\beta}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2$ and ${A}_{0}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0$, with $\ensuremath{\mu}&lt;0$, we exclude all models with ${m}_{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{q}}&lt;250\phantom{\rule{0ex}{0ex}}\mathrm{GeV}{/c}^{2}$. For models with equal squark and gluino masses, we exclude $m&lt;260\phantom{\rule{0ex}{0ex}}\mathrm{GeV}{/c}^{2}$.

We present a measurement of the differential cross section as a function of transverse momentum of the Z boson in ppbar collisions at sqrt{s}=1.8 TeV using data collected by the D0 experiment at the Fermilab Tevatron Collider during 1994--1996. We find good agreement between our data and the NNLO resummation prediction and extract values of the non-perturbative parameters for the resummed prediction from a fit to the differential cross section.

We present results on dijet production via hard color-singlet exchange in proton-antiproton collisions at s=630 GeV and 1800 GeV using the DØ detector. The fraction of dijet events produced via color-singlet exchange is measured as a function of jet transverse energy, separation in pseudorapidity between the two highest transverse energy jets, and proton-antiproton center-of-mass energy. The results are consistent with a color-singlet fraction that increases with an increasing fraction of quark-initiated processes and inconsistent with two-gluon models for the hard color-singlet.

We present a quasi-model-independent search for the physics responsible for electroweak symmetry breaking.We define final states to be studied, and construct a rule that identifies a set of relevant variables for any particular final state.A new algorithm ͑''SLEUTH''͒ searches for regions of excess in those variables and quantifies the significance of any detected excess.After demonstrating the sensitivity of the method, we apply it to the semi-inclusive channel eX collected in 108 pb Ϫ1 of pp ¯collisions at ͱsϭ1.8 TeV at the DO " experiment during 1992-1996 at the Fermilab Tevatron.We find no evidence of new high p T physics in this sample.

The inclusive cross section for production of isolated photons has been measured in pp macro collisions at square root of s = 630 GeV with the D0 detector at the Fermilab Tevatron Collider. The photons span a transverse energy (E(T)) range from 7-49 GeV and have pseudorapidity absolute value of eta < 2.5. This measurement is combined with the previous D0 result at square root of s = 1800 GeV to form a ratio of the cross sections. Comparison of next-to-leading-order QCD with the measured cross section at 630 GeV and the ratio of cross sections show satisfactory agreement in most of the E(T) range.

We present a search for charged Higgs bosons in decays of pair-produced top quarks in $p\overline{p}$ collisions at $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8\mathrm{TeV}$ recorded by the D0 detector at the Fermilab Tevatron collider. With no evidence for signal, we exclude most regions of the ( ${M}_{{H}^{\ifmmode\pm\else\textpm\fi{}}},\mathrm{tan}\ensuremath{\beta}$) parameter space where the decay $t\ensuremath{\rightarrow}{\mathrm{H}}^{+}b$ has a branching fraction $&gt;0.36$ and $B({H}^{\ifmmode\pm\else\textpm\fi{}}\ensuremath{\rightarrow}\ensuremath{\tau}{\ensuremath{\nu}}_{\ensuremath{\tau}})$ is large.

We have measured the W boson mass using the DØ detector and a data sample of 82 pb−1 from the Fermilab Tevatron collider. This measurement uses W→eν decays, where the electron is close to a boundary of a central electromagnetic calorimeter module. Such “edge” electrons have not been used in any previous DØ analysis, and represent a 14% increase in the W boson sample size. For these electrons, new response and resolution parameters are determined, and revised backgrounds and underlying event energy flow measurements are made. When the current measurement is combined with previous DØ W boson mass measurements, we obtain MW=80.483±0.084 GeV. The 8% improvement from the previous DØ measurement is primarily due to the improved determination of the response parameters for non-edge electrons using the sample of Z bosons with non-edge and edge electrons.Received 10 April 2002DOI:https://doi.org/10.1103/PhysRevD.66.012001©2002 American Physical Society

We present the charged-particle multiplicity distributions for ${e}^{+}{e}^{\ensuremath{-}}$ annihilation at center-of-mass energies from 50 to 61.4 GeV. The results are based on a data sample corresponding to a total integrated luminosity of 30 ${\mathrm{pb}}^{\ensuremath{-}1}$ obtained with the AMY detector at the KEK storage ring TRISTAN. The charged-particle multiplicity distributions deviate significantly from the modified Poisson and pair Poisson distributions, but follow Koba-Nielsen-Olesen scaling and are well reproduced by the LUND parton-shower model.

A measurement of direct photon production in pp collisions at a center of mass energy ∝s=63 GeV is reported. Arrays of lead-glass calorimeters and multiwire proportional chambers were used as photon detectors. Data are presented in the transverse momentum range from 4.5 to 10 GeV/c and compared with QCD predictions. The event structure of this sample is compared with that of a set dominated by high transverse momentum πÓ's.

The spectrum dNdET0 (ET0 = neutral transverse energy) has been measured with an electromagnetic calorimeter covering 90% of 2π in azimuth. The measurement, performed in pp collisions at s = 62 GeV, covered the ET0 range from 10 to 30 GeV. Evidence is presented that a large fraction of these events are jet-like, the fraction increasing with ET0.

In early 2010, the Long-Baseline Neutrino Experiment (LBNE) science collaboration initiated a study to investigate the physics potential of the experiment with a broad set of different beam, near- and far-detector configurations. Nine initial topics were identified as scientific areas that motivate construction of a long-baseline neutrino experiment with a very large far detector. We summarize the scientific justification for each topic and the estimated performance for a set of far detector reference configurations. We report also on a study of optimized beam parameters and the physics capability of proposed Near Detector configurations. This document was presented to the collaboration in fall 2010 and updated with minor modifications in early 2011.

The D0 collaboration has performed a study of spin correlation in $t\overline{t}$ production for the process $t\overline{t}\ensuremath{\rightarrow}{\mathrm{bW}}^{+}\overline{b}{W}^{\ensuremath{-}}$, where the $W$ bosons decay to $e\ensuremath{\nu}$ or $\ensuremath{\mu}\ensuremath{\nu}$. A sample of six events was collected during an exposure of the D0 detector to an integrated luminosity of approximately $125{\mathrm{pb}}^{\ensuremath{-}1}$ of $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8\mathrm{TeV}$ $p\overline{p}$ collisions. The standard model (SM) predicts that the short lifetime of the top quark ensures the transmission of any spin information at production to the $t\overline{t}$ decay products. The degree of spin correlation is characterized by a correlation coefficient $\ensuremath{\kappa}$. We find that $\ensuremath{\kappa}&gt;\ensuremath{-}0.25$ at the $68%$ confidence level, in agreement with the SM prediction of $\ensuremath{\kappa}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.88$.

This paper presents the first measurement of inclusive J͞c production cross section in the forward pseudorapidity region 2.5 # jh J͞c j # 3.7 in pp collisions at p s 1.8 TeV.The results are based on 9.8 pb 21 of data collected using the D0 detector at the Fermilab Tevatron Collider.The inclusive J͞c cross section for transverse momenta between 1 and 16 GeV͞c is compared with theoretical models of charmonium production.[S0031-9007(98)08183-6

This Letter describes a measurement of the muon cross section originating from $b$-quark decay in the forward rapidity range $2.4&lt;|{y}^{\ensuremath{\mu}}|&lt;3.2$ in $p\overline{p}$ collisions at $\sqrt{s}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.8\mathrm{TeV}$. The data used in this analysis were collected by the D0 experiment at the Fermilab Tevatron. We find that next-to-leading-order QCD calculations underestimate $b$-quark production by a factor of 4 in the forward rapidity region.

We apply a quasi-model-independent strategy ("Sleuth") to search for new high p_T physics in approximately 100 pb^-1 of ppbar collisions at sqrt(s) = 1.8 TeV collected by the DZero experiment during 1992-1996 at the Fermilab Tevatron. Over thirty-two e mu X, W+jets-like, Z+jets-like, and 3(lepton/photon)X exclusive final states are systematically analyzed for hints of physics beyond the standard model. Simultaneous sensitivity to a variety of models predicting new phenomena at the electroweak scale is demonstrated by testing the method on a particular signature in each set of final states. No evidence of new high p_T physics is observed in the course of this search, and we find that 89% of an ensemble of hypothetical similar experimental runs would have produced a final state with a candidate signal more interesting than the most interesting observed in these data.

We apply a quasi-model-independent strategy ("Sleuth") to search for new high p(T) physics in approximately 100 pb(-1) of pp collisions at square root of (s) = 1.8 TeV collected by the D0 experiment during 1992-1996 at the Fermilab Tevatron. We systematically analyze many exclusive final states and demonstrate sensitivity to a variety of models predicting new phenomena at the electroweak scale. No evidence of new high p(T) physics is observed.

We present cross section measurements for inclusive jet production in almost-real photon-photon interactions at TRISTAN using the AMY detector. The results are compared with leading-order QCD calculations for different parameterizations of the parton density in the photon.

We present a search for electroweak production of single top quarks in the electronϩjets and muonϩjets decay channels.The measurements use Ϸ90 pb Ϫ1 of data from Run 1 of the Fermilab Tevatron collider, collected at 1.8 TeV with the DO " detector between 1992 and 1995.We use events that include a tagging muon, implying the presence of a b jet, to set an upper limit at the 95% confidence level on the cross section for the s-channel process pp ¯→tbϩX of 39 pb.The upper limit for the t-channel process pp ¯→tqbϩX is 58 pb.

The photon structure function F2 has been measured at average Q2 values of 73,160 and 390 (GeVc)2. We compare the x dependence of the Q2 = 73 (GeVc)2 data with theoretical expectations based on QCD. In addition we present results on the Q2 evolution of the structure function for the intermediate x range (0.3⩽ x ⩽0.8). The results are consistent with QCD.

Results are presented on a measurement of the ttbar pair production cross section in ppbar collisions at sqrt{s} = 1.8 TeV from nine independent decay channels. The data were collected by the Dzero experiment during the 1992-1996 run of the Fermilab Tevatron Collider. A total of 80 candidate events are observed with an expected background of 38.8 +- 3.3 events. For a top quark mass of 172.1 GeV/c^2, the measured cross section is 5.69 +- 1.21 (stat) +- 1.04 (sys) pb.

Direct photons have been studied in pp̄ interactions at √s = 24.3 GeV and in the transverse momentum (pT) range 3–7 GeV/c(0.25 < xT < 0.58). The experiment was performed using an internal H2 cluster the target in the CERN pp̄ Collider. The measured invariant cross section is compared with recent theoretical predictions.

We report results on inclusive direct photon (γ),π0, and η production in both pp and p̄p interactions at s=24.3 GeV in the transverse momentum range 4.1≤pT≤7.7 GeV/c and rapidity range −0.1≤y≤0.9. The data were collected between 1988 and 1990 by the UA6 experiment at CERN, which employed an internal H2 gas jet target in the Sp̄pS collider. The inclusive direct photon cross sections and the cross section difference σ(pp)−σ(pp) expressed as functions of pT(γ) are compared with next-to-leading order QCD predictions.

ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

We present a measurement of the W boson mass using data collected by the DØ experiment at the Fermilab Tevatron during 1994–1995. We identify W bosons by their decays to eν final states where the electron is detected in a forward calorimeter. We extract the W boson mass MW by fitting the transverse mass and transverse electron and neutrino momentum spectra from a sample of 11 089 −→Weν decay candidates. We use a sample of 1687 dielectron events, mostly due to →Zee decays, to constrain our model of the detector response. Using the forward calorimeter data, we measure MW=80.691±0.227GeV. Combining the forward calorimeter measurements with our previously published central calorimeter results, we obtain MW=80.482±0.091GeV. Received 23 August 1999DOI:https://doi.org/10.1103/PhysRevD.62.092006©2000 American Physical Society

The central inclusive jet cross section has been measured using a successive-combination algorithm for reconstruction of jets. The measurement uses 87.3 pb−1 of data collected with the DØ detector at the Fermilab Tevatron pp Collider during 1994–1995. The cross section, reported as a function of transverse momentum (pT>60 GeV) in the central region of pseudorapidity (|η|<0.5), exhibits reasonable agreement with next-to-leading order QCD predictions, except at low pT where the agreement is marginal.

Three-jet events produced in ${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$ annihilations are used to provide comparisons between quark and gluon jets. Differences between quark-induced and gluon-induced jets are observed. Quark jets tend to have a more tightly collimated structure than gluon jets, which is reflected in the concentration of a larger fraction of the jet's energy near the jet axis.

Extensive experimental data from high-energy nucleus-nucleus collisions were recorded using the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC). The comprehensive set of measurements from the first three years of RHIC operation includes charged particle multiplicities, transverse energy, yield ratios and spectra of identified hadrons in a wide range of transverse momenta (pT), elliptic flow, two-particle correlations, nonstatistical fluctuations, and suppression of particle production at high pT. The results are examined with an emphasis on implications for the formation of a new state of dense matter. We find that the state of matter created at RHIC cannot be described in terms of ordinary color neutral hadrons.

Neutral transverse energy spectra in pp and αα interactions are analyzed in terms of the wounded nucleon model. Analysis of the αα spectrum by application of a multiple nucleon-nucleon collision mechanism is conveniently performed when a gamma distribution is used to represent the pp spectral shape. The wounded nucleon model provides a reasonable description of the αα spectrum for the first three orders of magnitude, but completly fails to account for the slope of the high energy tail of the distribution. However, the pp and αα spectra can both be fitted to the same gamma distribution when scaled by their respective mean values and thus exhibit KNO scaling.

The rates for same-sign and opposite-sign dimuon events with missing energy (indicative of final-state neutrinos) have been measured in 278 GeV π−-Fe and 350 GeV proton-Fe collisions. The main source of opposite-sign events is two semi-leptonic decays of hadronically produced charm states. The same-sign events are consistent with background from pion and kaon decays. We obtain a limit of 0.044 (90% CL) on the fraction of D0 semileptonic decays that result in the wrong-sign muon and conclude that less than 9% (90% CL) of same-sign dimuon events produced in neutrino interactions can be attributed to D0-D0 mixing. The data imply δm < 6.5 × 10−4 eV and δλλ < 0.55 for the difference in mass and inverse lifetime of the CP eigenstates of the D0. Limits on diffractive bottom production cross sections in proton and pion collisions are also presented.

We present a measurement of t t production in pp collisions at √ s = 1.8 TeV from 110 pb -1 of data collected in the all-jets decay channel with the DØ detector at Fermilab.A neural network analysis yields a cross section of 7.1 ± 2.8 (stat.)± 1.5 (syst.)pb, at a top quark mass (mt) of 172.1 GeV/c 2 .Using previous DØ measurements from dilepton and single lepton channels, the combined DØ result for the t t production cross section is 5.9 ± 1.2 (stat.)± 1.1 (syst.)pb for mt = 172.1 GeV/c 2 .

The photon structure function F2γ has been measured at average Q2 values of 73 and 390 GeV2 using data collected by the AMY detector at the TRISTAN e+e− collider. F2γ is observed to be increasing as ln Q2. The x-dependence of F2γ, where x is the momentum fraction carried by the parton inside the photon, is also measured. The measurements are compared with several parton density models.

We have studied t t ¯production using multijet final states in pp ¯collisions at a center-of-mass energy of 1.8 TeV, with an integrated luminosity of 110.3 pb Ϫ1 .Each of the top quarks with these final states decays exclusively to a bottom quark and a W boson, with the W bosons decaying into quark-antiquark pairs.The analysis has been optimized using neural networks to achieve the smallest expected fractional uncertainty on the t t ¯production cross section, and yields a cross section of 7.1Ϯ2.8͑stat͒Ϯ1.5͑syst͒ pb, assuming a top quark mass of 172.1 GeV/c 2 .Combining this result with previous DO " measurements, where one or both of the W bosons decay leptonically, gives a t t ¯production cross section of 5.9Ϯ1.2(stat)Ϯ1.1 (syst) pb.͓S0556-2821͑99͒03607-3͔

Inclusive dijet production at large pseudorapidity intervals (Deltaeta) between the two jets has been suggested as a regime for observing Balitsky-Fadin-Kuraev-Lipatov (BFKL) dynamics. We have measured the dijet cross section for large Deltaeta in pp collisions at sqrt[s]=1800 and 630 GeV using the D0 detector. The partonic cross section increases strongly with the size of Deltaeta. The observed growth is even stronger than expected on the basis of BFKL resummation in the leading logarithmic approximation. The growth of the partonic cross section can be accommodated with an effective BFKL intercept of alphaBFKL(20 GeV)=1.65+/-0.07.

We have searched for second-generation leptoquark (LQ) pairs in the &mgr;&mgr;+jets channel using 94+/-5 pb(-1) of &pmacr;p collider data collected by the D0 experiment at the Fermilab Tevatron during 1993-1996. No evidence for a signal is observed. These results are combined with those from the &mgr;nu+jets and nunu+jets channels to obtain 95% confidence level (C.L.) upper limits on the LQ pair production cross section as a function of mass and beta, the branching fraction of a LQ decay into a charged lepton and a quark. Lower limits of 200(180) GeV/c(2) for beta = 1(1 / 2) are set at the 95% C.L. on the mass of scalar LQ. Mass limits are also set on vector leptoquarks as a function of beta.

We present results of searches for technirho (rho(T)), techniomega (omega(T)), and Z' particles, using the decay channels rho(T),omega(T),Z'-->e(+)e(-). The search is based on 124.8 pb(-1) of data collected by the D0 detector at the Fermilab Tevatron during 1992-1996. In the absence of a signal, we set 95% C.L. upper limits on the cross sections for the processes pp-->rho(T),omega(T),Z'-->e(+)e(-) as a function of the mass of the decaying particle. For certain model parameters, we exclude the existence of degenerate rho(T) and omega(T) states with masses below about 200 GeV. We exclude a Z' with mass below 670 GeV, assuming that it has the same couplings to fermions as the Z boson.

The ratio $R$ of the total cross section for ${e}^{+}{e}^{\ensuremath{-}}$ annihilation into hadrons to the lowest-order QED cross section for ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ has been measured for center-of-mass energies ranging from 50 to 61.4 GeV. If we allow for an overall shift of ---4.9%, about 1.5 times our estimated normalization error, the results are consistent with the standard-model predictions.

Inclusive π0 and η production at large transverse momentum were studied in both p̄p and pp interactions at √s = 24.3 GeV. The experiment was performed using an internal molecular hydrogen gas jet target in the CERN SPS collider. No significant differences between production in p̄p and pp were observed in the transverse momentum range 2.5 < PT < 5.1 GeV/c.

The invariant cross sections for π0 meson production in alpha—alpha and alpha—proton collisions at the ISR were meas- ured up to transverse momenta of 7 GeVc and 8 GeVc, respectively. These measurements are compared with π0 production in pp collisions at the same values of s/nucleon, and the variation of the nuclear A-dependence with pT is determined.

The forward production of charm states in 350 GeV p-Fe interactions has been studied via the production of prompt single muons with momentum p ≳ 20 GeV/c. The data indicate equal production of single μ+ and μ− events. The observed momentum distributions can be fit with the hypothesis that D mesons are produced with an invariant cross section proportional to (1 − xF)5.0±0.8 exp[−(2 ± 0.3)Pt] and do not favor a large diffractive cross section predicted by intrinsic charm models. Extrapolation of the distributions to xF = 0 yields a total DD production cross section of 22.6 ± 2.1(±3.6)ωb/nucleon on the assumption of a linear A dependence and 8% average semileptonic branching ratio of charm states.

The spectra in total neutral energy, ETOT0, have been measured in pp, dd and αα collisions at centre-of-mass energy per nucleon pair, sNN, of 31 GeV. The range in ETOT0 covered was 1 to 19 GeV in pp, 18 to 24 GeV in dd and 1 to 34 GeV in αα interactions. The ratio of the αα to the pp spectra rises monotonically from 7 at ETOT0 = 1.5 GeV to 105 at ETOT 0 = 19 GeV. Since ETOT0 is the sum over many particles in the detector, it is directly sensitive to multiple nucleon-nucleon collisions in the interacting α particles. The αα spectrum in the range 8 < ETOT0 < 17 GeV is consistent with being described by a simple model of 4 simultaneous nucleon-nucleon collisions with a cross section about equal to 10% of the observed αα interaction cross section. The spectrum of ETOT0 above 17 GeV is even flatter than this extreme case where four nucleon pairs are interacting.

Evidence of anomalous WW and WZ production was sought in pbar{p} collisions at a center-of-mass energy of sqrt(s) = 1.8 TeV. The final states $WW (WZ) to mu-nu-jet-jet + X, WZ to mu-nu-e-e + X and WZ to e-nu-e-e + X were studied using a data sample corresponding to an integrated luminosity of approximately 90 pb-1. No evidence of anomalous diboson production was found. Limits were set on anomalous WWgamma and WWZ couplings and were combined with our previous results. The combined 95% confidence level anomalous coupling limits for Lambda=2 TeV are -0.25 LE Delta-kappa LE 0.39 (lambda=0) and -0.18 LE lambda LE 0.19 (Delta \kappa = 0), assuming the WWgamma couplings are equal to the WWZ couplings.

We report a measurement of the differential cross section for W boson production as a function of its transverse momentum in proton–antiproton collisions at s=1.8 TeV. The data were collected by the DØ experiment at the Fermilab Tevatron Collider during 1994–1995 and correspond to an integrated luminosity of 85 pb−1. The results are in good agreement with quantum chromodynamics over the entire range of transverse momentum.

We report on a search for R-parity violating supersymmetry in p-pbar collisions at sqrt(s) = 1.8 TeV using the D0 detector at Fermilab. Events with at least two electrons and four or more jets were studied. We observe 2 events in 99 +- 4.4 pb-1 of data, consistent with the expected background of 1.8 +- 0.4 events. This result is interpreted within the framework of minimal low-energy supergravity supersymmetry models. Squarks with mass below 243 GeV/c^2 and gluinos with mass below 227 GeV/c^2 are excluded at the 95% confidence level (C. L.) for A_0=0, mu &lt; 0$, tan beta=2 and a finite value for R-parity violating Yukawa coupling lambda'_1jk (j=1, 2 and k=1, 2, 3). For equal squark and gluino masses, the corresponding mass limit is 277 GeV/c^2.

We report on a search for bottom squarks $(\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{b})$ produced in $p\overline{p}$ collisions at $\sqrt{s}=1.8 \mathrm{TeV}$ using the D\O{} detector at Fermilab. Bottom squarks are assumed to be produced in pairs and to decay to the lightest supersymmetric particle (LSP) and a b quark with a branching fraction of 100%. The LSP is assumed to be the lightest neutralino and stable. We set limits on the production cross section as a function of $\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{b}$ mass and LSP mass.

Based on 85 ${\mathrm{pb}}^{\mathrm{\ensuremath{-}}1}$ data of $p\overline{p}$ collisions at $\sqrt{s}=1.8\mathrm{TeV}$ collected using the D\O{} detector at Fermilab during the 1994--1995 run of the Tevatron, we present a direct measurement of the total decay width of the W boson ${\ensuremath{\Gamma}}_{W}.$ The width is determined from the transverse mass spectrum in the $\stackrel{\ensuremath{\rightarrow}}{W}e+{\ensuremath{\nu}}_{e}$ decay channel and found to be ${\ensuremath{\Gamma}}_{W}{=2.23}_{\ensuremath{-}0.14}^{+0.15}(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.10(\mathrm{syst})\mathrm{GeV},$ consistent with the expectation from the standard model.

Mg -1Mq -1 = 1.84 ± 0.15 (stat.)± 0.22 0.18 (sys.).This ratio is

Using the D0 detector, we have studied events produced in proton-antiproton collisions that contain large forward regions with very little energy deposition (``rapidity gaps'') and concurrent jet production at center-of-mass energies of root-s = 630 and 1800 Gev. The fractions of forward and central jet events associated with such rapidity gaps are measured and compared to predictions from Monte Carlo models. For hard diffractive candidate events, we use the calorimeter to extract the fractional momentum loss of the scattered protons.

We report results from a measurement of antiproton-proton and proton-proton small-angle elastic scattering at √s = 24.3 GeV in the range 0.001 ⩽ |t | ⩽ 0.06 (GeV/c)2. The measurement was performed at the CERN pp Collider by using silicon detectors to observe protons recoiling from a hydrogen cluster-jet target intercepting the stored p and p beams. Fits to the measured differential cross sections yield the ratio of the real to the imaginary part of the forward nuclear scattering amplitude ρ and the nuclear slope parameter b for both pp and pp. We find that the difference Δρ = ρ (pp) − ρ(pp) = 0.031 ± 0.010 agrees with conventional fits and disagrees with the “odderon” fit designed to accommodate the recent UA4 measurement of ρ(pp) at 546 GeV.

Abstract The inclusive cross section times branching ratio for J/ψ→e + e − has been measured in the forward region in the UA6 experiment for p p and pp collisions at √ s = 24.3 GeV. The ratio of the pp to p p cross sections is found to be 0.76 ± 0.14 ± 0.06. This demonstrates that gluon-gluon fusion dominates over quark-antiquark annihilation in the formation of the c c state.

Limits on anomalous WW␥ and WWZ couplings are presented from a study of WW/WZ→e j j events produced in pp ¯collisions at ͱsϭ1.8 TeV.Results from the analysis of data collected using the DO " detector during the 1993-1995 Tevatron collider run at Fermilab are combined with those of an earlier study from the 1992-1993 run.A fit to the transverse momentum spectrum of the W boson yields direct limits on anomalous WW␥ and WWZ couplings.With the assumption that the WW␥ and WWZ couplings are equal, we obtain Ϫ0.34ϽϽ0.36͑with ⌬ϭ0) and Ϫ0.43Ͻ⌬Ͻ0.59͑with ϭ0) at the 95% confidence level for a formfactor scale ⌳ϭ2.0 TeV.

Searches for the pair production of the supersymmetric partner particles of leptons, quarks, and non-minimal Higgs have been made in e +e − annihilations at center-of-mass energies between 50 and 60.8 GeV using the AMY detector at TRISTAN. No evidence for their existence is observed and 95% CL mass limits are presented.

We have performed a search for scalar top quark (stop) pair production in the inclusive electron-muon-missing transverse energy final state, using a sample of pp events corresponding to 108.3 pb(-1) of data collected with the D0 detector at Fermilab. The search is done in the framework of the minimal supersymmetric standard model assuming that the sneutrino is the lightest supersymmetric particle. For the dominant decays of the lightest stop, t-->b chi+1 and t-->blnu, no evidence for signal is found. We derive cross-section limits as a function of stop ( t ), chargino ( chi+1), and sneutrino ( nu) masses.

The forward production of charm states in 278 GeV π− Fe interactions has been studied via the production of prompt single muons with momentum ≳ 20 GeV/c. The production of prompt 1u− is significantly larger than the production of prompt 1u+ events. For xD ≳ 0.2 the data indicate that on the average D mesons are produced with a (1−x)2 distribution. The experimental distributions are compared with various charm production models. A fit to a model incorporating both central and forward production yields a production cross section of 17.5−3.9+5.4 μb/nucleon (x >fx 0), assuming a linear A dependence and an 8% average semileptonic branching ratio.

DO has measured the inclusive production cross section of W and Z bosons in a sample of 13 pb$^{-1}$ of data collected at the Fermilab Tevatron. The cross sections, multiplied by their leptonic branching fractions, for production in pbar-p collisions at sqrt{s}=1.8 TeV are sigma_W*B(W-&gt;e nu) = 2.36+-0.02+-0.08+-0.13 nb, sigma_W*B(W-&gt;mu nu) = 2.09+-0.06+-0.22+-0.11 nb, sigma_Z*B(Z-&gt;e+ e-) = 0.218+-0.008+-0.008+-0.012 nb, and sigma_Z*B(Z-&gt;mu+ mu-) = 0.178+-0.022+-0.021+-0.009 nb, where the first uncertainty is statistical and the second systematic; the third reflects the uncertainty in the integrated luminosity. For the combined electron and muon analyses, we find sigma_W*B(W-&gt;l mu)/sigma_Z*B(Z-&gt;l+ l-) = 10.90+-0.52. Assuming standard model couplings, we use this result to determine the width of the W boson, and obtain Gamma(W) = 2.044+-0.097 GeV.

We search for new physics using events with one high transverse energy photon, two or more jets, and an apparent imbalance in transverse energy, in p¯p collisions at the Fermilab Tevatron at √s=1.8TeV. Such events are predicted for production of supersymmetric particles in some models. No excess is observed beyond expected background. For the parameter space of the minimal supersymmetric standard model with branching fraction B(˜χ02→γ˜χ01)=1 and m˜χ02−m˜χ01>20GeV, we obtain a 95% confidence level lower mass limit of 310 GeV for equal mass squarks and gluinos. The results are also interpreted in models with low energy gauge mediated supersymmetry breaking.Received 14 August 1998DOI:https://doi.org/10.1103/PhysRevLett.82.29©1999 American Physical Society

We report on a measurement of sigma(pp-->W+X)B(W-->taunu) in pp collisions at sqrt[s]=1.8 TeV at the Fermilab Tevatron. The measurement is based on an integrated luminosity (lum) of 18 pb-1 of data collected with the D0 detector during 1994-1995. We find that sigma(pp-->W+X)B(W-->taunu)=2.22+/-0.09 (stat)+/-0. 10 (syst)+/-0.10 (lum) nb. Lepton universality predicts that the ratio of the tau and electron electroweak charged current couplings to the W boson, gWtau/gWe, be unity. We find gWtau/gWe=0.980+/-0.031, in agreement with lepton universality.

By studying ${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$ annihilations in the center-of-mass energy range between 50 and 60.8 GeV, we have established a 95%-confidence-level lower limit on the mass of a fourth-generation charge -(1/3 quark b' of 27.2 GeV. In contrast with all previous searches, this limit has been obtained through consideration of the decay processes b'\ensuremath{\rightarrow}b\ensuremath{\gamma} and b'\ensuremath{\rightarrow}bg aswell as b'\ensuremath{\rightarrow}${\mathrm{cW}}^{\mathrm{\ensuremath{-}}}$. For the cases where any one of the three decay modes dominates, we obtain higher mass limits.

Abstract The hadronic production of charm particle pairs produced in the forward direction has been investigated in study of μ + μ − pairs with large missing energy (indicative of final-state neutrinos). These events result primarily from two semileptonic decays of charm-anticharm states. A comparison of the data with the prediction of the intrinsic charm diffractive model indicates that diffractive production cross sections are small (of the order of a few μ b) in both 350 GeV proton and 278 GeV pion interactions.

Direct photon cross sections obtained in pp and pp collisions at √s = 24.3 GeV at the CERN SPS, are used in a next-to-leading order QCD analysis. From the cross-section difference σ(pp → γX) − σ (pp → γX), and quark distributions measured in deep inelastic scattering, a determination of the strong coupling constant, αs, is performed via a measurement of Λ(4)MS. This first measurement of Λ(4)MS using direct photon data yields a value Λ(4)MS = 235 ± 79 (stat.) ± 70 (syst.) MeV. The corresponding value of αs expressed at MZ2 is αs (MZ2) = 0.112±0.006 (stat.)±0.005 (syst.)−0.001+0.009 (theor.). The gluon distribution in the proton for x > 0.2 is determined both from the pp and from the pp data, and the results agree with each other and with previous determinations using the same method.

The photon structure function F2γ has been measured at an average Q2 value of 6.8 GeV2 using data collected by the AMY detector at the TRISTAN e+e− collider. The measured F2γ is compared with several QCD-based parton density models.

Inclusive direct photon invariant cross sections have been measured in both pp and pp collisions at √s = 24.3 GeV at the CERN SPS, permitting the first measurement of the difference of the pp and pp cross sections. The direct photon cross section in pp collisions has been found to be systematically larger than that in pp collisions, which indicates a significant contribution of the qq annihilation term as predicted by theoretical calculations.

The forward-backward asymmetry of quarks produced in ${e}^{+}$${e}^{\mathrm{\ensuremath{-}}}$ annihilations, summed over all flavors, is measured at \ensuremath{\surd}s between 50 and 60.8 GeV. Methods of determining the charge direction of jet pairs are discussed. The asymmetry is found to agree with the five-flavor standard model.

The D0 Collaboration has measured the inclusive jet cross section in barpp collisions at square root of s = 630 GeV. The results for pseudorapidities (eta)<0.5 are combined with our previous results at square root of s = 1800 GeV to form a ratio of cross sections with smaller uncertainties than either individual measurement. Next-to-leading-order QCD predictions show excellent agreement with the measurement at 630 GeV; agreement is also satisfactory for the ratio. Specifically, despite a 10% to 15% difference in the absolute magnitude, the dependence of the ratio on jet transverse momentum is very similar for data and theory.

Presented are the main design features of the large Cathode Strip Chambers (CSCs) for the CMS Endcap Muon System as well as the performance results obtained with the two full-scale 3.4×1.5 m2 six-plane prototypes. The prototype performance was within the baseline requirements: (a) higher than 99% efficiency of muon track finding at the trigger level with more than 92% probability for bunch crossing identification and better than 2 mm spatial resolution, and (b) better than 150 μm spatial resolution in off-line.

Abstract Most events with high neutral transverse energy, ET0, produced in pp colisions at √s = 62.3 GeV, are jet-like. The evidence for this is presented, based on data collected using an electromagnetic calorimeter covering 90% of 2π in azimuth. The spectrum dN/dET0 has been measured over the ET0 range from 10 to 35 GeV. Properties of the observed jets are discussed.

We describe a search for the pair production of first-generation scalar and vector leptoquarks in the eejj and enujj channels by the D0 Collaboration. The data are from the 1992--1996 ppbar run at sqrt{s} = 1.8 TeV at the Fermilab Tevatron collider. We find no evidence for leptoquark production; in addition, no kinematically interesting events are observed using relaxed selection criteria. The results from the eejj and enujj channels are combined with those from a previous D0 analysis of the nunujj channel to obtain 95% confidence level (C.L.) upper limits on the leptoquark pair-production cross section as a function of mass and of beta, the branching fraction to a charged lepton. These limits are compared to next-to-leading-order theory to set 95% C.L. lower limits on the mass of a first-generation scalar leptoquark of 225, 204, and 79 GeV/c^2 for beta=1, 1/2, and 0, respectively. For vector leptoquarks with gauge (Yang-Mills) couplings, 95% C.L. lower limits of 345, 337, and 206 GeV/c^2 are set on the mass for beta=1, 1/2, and 0, respectively. Mass limits for vector leptoquarks are also set for anomalous vector couplings.

We present data on multiple production of jets with transverse energies near 20 GeV in pp collisions at √ s = 1.8 TeV.QCD calculations in the partonshower approximation of pythia and herwig and the next-to-leading order approximation of jetrad are compared to the data for one, two, three, and four jet inclusive production.Transverse energy spectra and multiple jet angular and summed transverse-energy distributions are adequately described by the shower approximation while next-to-leading order calculations describe the data poorly.

Abstract A sample of 58e + e − events with an invariant mass greater than 11 GeV/c 2 produced in pp collisions at a centre-of-mass energy of 62.3 GeV is discussed. The cross sections are presented as a function of the mass and transverse momentum. The electron pairs produced with a mean transverse momentum of 2.50 ± 0.25 GeV/ c .

We have searched for the signature of 3- and 4-body decays of pair-produced scalar top quarks (stop) in the inclusive final state containing an electron, a muon, and significant missing transverse energy using a sample of pp̄ events corresponding to 108.3 pb−1 of data collected with the DØ detector at Fermilab. The search is done in the framework of the minimal supersymmetric standard model assuming that the neutralino (χ̃01) is the lightest supersymmetric particle and is stable. No evidence for a signal is found and we derive cross-section upper limits as a function of stop (t̃) and neutralino masses in different decay scenarios leading to the bℓνχ̃01 final state.

We report on a search for second generation leptoquarks (LQ) produced in p¯p collisions at √s=1.8TeV using the D0 detector at Fermilab. Second generation leptoquarks are assumed to be produced in pairs and to decay to either μ or ν and either a strange or a charm quark (q). Limits are placed on σ(p¯p→LQ¯LQ→μν+jets) as a function of the mass of the leptoquark. For equal branching ratios to μq and νq, second generation scalar leptoquarks with a mass below 160GeV/c2, vector leptoquarks with anomalous minimal vector couplings with a mass below 240GeV/c2, and vector leptoquarks with Yang-Mills couplings with a mass below 290GeV/c2, are excluded at the 95% confidence level.Received 23 April 1999DOI:https://doi.org/10.1103/PhysRevLett.83.2896©1999 American Physical Society

We describe QUAERO, a method that (i) enables the automatic optimization of searches for physics beyond the standard model, and (ii) provides a mechanism for making high energy collider data generally available. We apply QUAERO to searches for standard model WW, ZZ, and t t macro production, to searches for these objects produced through a new heavy resonance, and to the first direct search for W'-->WZ. Through this interface, we make three data sets collected by the D0 experiment at square root of [s] = 1.8 TeV publicly available.

We report on a search for supersymmetry using the DØ detector. The 1994–1996 data sample of √s=1.8 TeV p¯p collisions was analyzed for events containing two leptons (e or μ), two or more jets, and missing transverse energy. Assuming the minimal supergravity model, with A0=0 and μ<0, various thresholds were employed to optimize the search. No events were found beyond expectation from the background. We set a lower limit at the 95% C.L. of 255 GeV/c2 for equal mass squarks and gluinos for tanβ=2, and present exclusion contours in the (m0,m1/2) plane for tanβ=2–6.Received 9 February 2000DOI:https://doi.org/10.1103/PhysRevD.63.091102©2001 American Physical Society

We report on a study of the ratio of inclusive three-jet to inclusive two-jet production cross sections as a function of total transverse energy in p&pmacr; collisions at a center-of-mass energy sqrt[s] = 1.8 TeV, using data collected with the D0 detector during the 1992-1993 run of the Fermilab Tevatron Collider. The measurements are used to deduce preferred renormalization scales in perturbative O(alpha(3)(s)) QCD calculations in modeling soft-jet emission.

We report on a search for the pair production of leptoquarks and colored leptons in e+e− annihilations t center-of-mass energies from 50 to 60.8 GeV, using the AMY detector at TRISTAN. No evidence for such particles is found and 95% CL mass limits are given.

Abstract A comparison of p p and pp interactions s =52.7 GeV at the CERN ISR. The quantities compared were the charged and neutral multiplicities, the total neutral transverse energy, ΣET, up to 12 GeV, and the single π0 inclusive cross section up to p T = 5 GeV c . No significant differences were observed.

We present the results of a search for leptoquark (LQ) pairs in (85.2+/-3.7) pb(-1) of pp* collider data collected by the D0 experiment at the Fermilab Tevatron. We observe no evidence for leptoquark production and set a limit on sigma(pp*-->LQLQ-->nunu+jets) as a function of the mass of the leptoquark (m(LQ)). Assuming the decay LQ-->nuq, we exclude scalar leptoquarks for m(LQ) < 98 GeV/c(2), and vector leptoquarks for m(LQ) < 200 GeV/c(2) and coupling which produces the minimum cross section, at a 95% confidence level.

Two CMS production Cathode Strip Chambers were tested for aging effects in a high-radiation environment at the Gamma Irradiation Facility at CERN. The chambers were irradiated over a large area: in total, about 2.1 m2 or 700 m of wire in each chamber. The 40% Ar+50% CO2+10% CF4 gas mixture was provided by an open-loop gas system for one of the chambers and by a closed-loop re-circulating gas system for the other. After an accumulation of 0.3–0.4 C/cm of a wire, equivalent to about 30–50 years of operation at peak LHC luminosity, no significant changes in gas gain, chamber efficiency and wire signal noise were observed for either of the two chambers. The only consistent signs of aging were a small increase in dark current from ∼2 to ∼10 nA per plane of 600 wires and a decrease of strip-to-strip resistance from 1000 to 10–100 GΩ. Disassembly of the chambers revealed deposits on the cathode planes, while the anode wires remained fairly clean.

A study of e+e− annihilations into final states containing a single energetic photon with no accompanying particles is made at a center of mass energy of 57.8 GeV. The measured cross section is consistent with expectations from standard model processes and is used to set limits on the masses of the scalar electron and photino particles predicted by supersymmetry theories. If the photino is assumed to be massless, the 90% confidence level lower limit on the mass of the degenerate scalar electron is 65.5 GeV. If the results of all the single photon experiments are combined, this lower limit increases to 79.3 GeV.

Direct photon production cross sections obtained in high statistics p̄p and pp collisions at s=24.3 GeV at the CERN SPS are used in a next-to-leading order QCD analysis. From the cross section difference σ(p̄p→γX)−σ(pp→γX) and quark distributions measured in deep inelastic scattering, a determination of the strong coupling constant, αs, is performed via a measurement of Λ(4)MS. This measurement yields a value Λ(4)MS = 210±22(stat.)±44(syst.)+105−36(theo.) MeV. The corresponding value of αs expressed at M2Z is αs(M2Z)=0.1112±0.0016(stat.)±0.0033(syst.)+0.0077−0.0034(theo.).

After a brief overview of the CMS EMU electronics system, results on radiation induced single event effects, total ionization dose and displacement effects will be reported. These results are obtained by irradiating the components on electronics boards with 63MeV protons and 1MeV neutrons. During the proton irradiation, the electronics board was fully under power, all components on the board were active and the data were read out in the same way as designed for CMS. No deterioration of analog performance for each of the three CMOS ASICs on the tested board was observed, up to a dose of 10krad. Each of the tested FPGAs survived beyond the dose of 30krad. No single event latch-up was detected for the CMOS ASICs up to a proton fluence of 2×1012cm−2. Single Event Upsets (SEU) in FPGAs were detected and their cross-sections measured. SEU mitigation with triple module redundancy and voting was implemented and tested.

We present the first measurement of the electron angular distribution parameter ␣ 2 in W→e events produced in proton-antiproton collisions as a function of the W boson transverse momentum.Our analysis is based on data collected using the DØ detector during the 1994-1995 Fermilab Tevatron run.We compare our results with next-to-leading order perturbative QCD, which predicts an angular distribution of (1 Ϯ␣ 1 cos *ϩ␣ 2 cos 2 *), where * is the polar angle of the electron in the Collins-Soper frame.In the presence of QCD corrections, the parameters ␣ 1 and ␣ 2 become functions of p T W , the W boson transverse momentum.This measurement provides a test of next-to-leading order QCD corrections which are a nonnegligible contribution to the W boson mass measurement.