Showing papers by "Allan G Clark published in 2006"

The upgraded DØ detector

Abstract: The D0 experiment enjoyed a very successful data-collection run at the Fermilab Tevatron collider between 1992 and 1996. Since then, the detector has been upgraded to take advantage of improvements to the Tevatron and to enhance its physics capabilities. We describe the new elements of the detector, including the silicon microstrip tracker, central fiber tracker, solenoidal magnet, preshower detectors, forward muon detector, and forward proton detector. The uranium/liquid-argon calorimeters and central muon detector, remaining from Run I, are discussed briefly. We also present the associated electronics, triggering, and data acquisition systems, along with the design and implementation of software specific to D0.

The barrel modules of the ATLAS semiconductor tracker

Abstract: This paper describes the silicon microstrip modules in the barrel section of the SemiConductor Tracker (SCT) of the ATLAS experiment at the CERN Large Hadron Collider (LHC). The module requirements, components and assembly techniques are given, as well as first results of the module performance on the fully assembled barrels that make up the detector being installed in the ATLAS experiment.

Measurement of the Bs0-B̄s0 oscillation frequency

Abstract: The authors present the first measurement of the B{sub s}{sup 0}-{bar B}{sub s}{sup 0} oscillation frequency {Delta}m{sub s}. They use 1 fb{sup -1} of data from p{bar p} collisions at {radical}s = 1.96 TeV collected with the CDF II detector at the Fermilab Tevatron. The sample contains signals of 3600 fully reconstructed hadronic B{sub s} decays and 37,000 partially reconstructed semileptonic B{sub s} decays. They measure the probability as a function of proper decay time that the B{sub s} decays with the same, or opposite, flavor as the flavor at production and they find a signal consistent with B{sub s}{sup 0}-{bar B}{sub s}{sup 0} oscillations. The probability that random fluctuations could produce a comparable signal is 0.2%. Under the hypothesis that the signal is due to B{sub s}{sup 0}-{bar B}{sub s}{sup 0} oscillations, they measure {Delta}m{sub s} = 17.31{sub -0.18}{sup +0.33}(stat.) {+-} 0.07(syst.) ps{sup -1} and determine |V{sub td}/V{sub ts}| = 0.208{sub -0.002}{sup +0.001}(exp.){sub -0.006}{sup +0.008}(theo.).

Observation of Bs 0 - B̄s 0 oscillations

Abstract: We report the observation of B{sub s}{sup 0}-B{sub s}{sup 0} oscillations from a time-dependent measurement of the B{sub s}{sup 0}-B{sub s}{sup 0} oscillation frequency {delta}m{sub s}. Using a data sample of 1 fb{sup -1} of pp collisions at {radical}(s)=1.96 TeV collected with the CDF II detector at the Fermilab Tevatron, we find signals of 5600 fully reconstructed hadronic B{sub s} decays, 3100 partially reconstructed hadronic B{sub s} decays, and 61 500 partially reconstructed semileptonic B{sub s} decays. We measure the probability as a function of proper decay time that the B{sub s} decays with the same, or opposite, flavor as the flavor at production, and we find a signal for B{sub s}{sup 0}-B{sub s}{sup 0} oscillations. The probability that random fluctuations could produce a comparable signal is 8x10{sup -8}, which exceeds 5{sigma} significance. We measure {delta}m{sub s}=17.77{+-}0.10(stat){+-}0.07(syst) ps{sup -1} and extract vertical bar V{sub td}/V{sub ts} vertical bar =0.2060{+-}0.0007({delta}m{sub s}){sub -0.0060}{sup +0.0081}({delta}m{sub d}+theor)

Search for charged Higgs bosons from top quark decays in pp̄ collisions at s=1.96TeV

Abstract: We report the results of a search for a charged Higgs boson in the decays of top quarks produced in pp collisions at a center-of-mass energy of 1.96 TeV. We use a data sample corresponding to an integrated luminosity of 193 pb{sup -1} collected by the upgraded Collider Detector at Fermilab. No evidence for charged Higgs production is found, allowing 95% C.L. upper limits to be placed on BR(t{yields}H{sup +}b) for different charged Higgs decay scenarios. In addition, we present in the minimal supersymmetric standard model (m{sub H{sup {+-}}},tan{beta}) plane the first exclusion regions with radiative and Yukawa coupling corrections.

Top quark mass measurement using the template method in the lepton + jets channel at CDF II

Abstract: This article presents a measurement of the top quark mass using the CDF II detector at Fermilab. Colliding beams of protons and antiprotons at Fermilab's Tevatron ($\sqrt{s}=1.96\text{ }\text{ }\mathrm{TeV}$) produce top/antitop pairs, which decay to ${W}^{+}{W}^{\ensuremath{-}}b\overline{b}$; events are selected where one $W$ decays to hadrons and the other $W$ decays to either $e$ or $\ensuremath{\mu}$ plus a neutrino. The data sample corresponds to an integrated luminosity of approximately $318\text{ }\text{ }{\mathrm{pb}}^{\ensuremath{-}1}$. A total of 165 $t\overline{t}$ events are separated into four subsamples based on jet transverse energy thresholds and the number of $b$ jets identified by reconstructing a displaced vertex. In each event, the reconstructed top quark invariant mass is determined by minimizing a ${\ensuremath{\chi}}^{2}$ for the overconstrained kinematic system. At the same time, the mass of the hadronically decaying $W$ boson is measured in the same event sample. The observed $W$ boson mass provides an in situ improvement in the determination of the hadronic jet energy scale. A simultaneous likelihood fit of the reconstructed top quark masses and the $W$ boson invariant masses in the data sample to distributions from simulated signal and background events gives a top quark mass of ${173.5}_{\ensuremath{-}3.8}^{+3.9}\text{ }\text{ }\mathrm{GeV}/{c}^{2}$.

Search for Z??e+e- Using Dielectron Mass and Angular Distribution

Abstract: The authors search Z{prime} bosons in dielectron events produced in p{bar p} collisions at {radical}s = 1.96 TeV, using a 0.45 fb{sup -1} dataset accumulated with the CDF II detector at the Fermilab Tevatron. To identify the Z{prime} {yields} e{sup +}e{sup -} signal, both the dielectron invariant mass distribution and the angular distribution of the electron pair are used. No evidence of a signal is found, and 95% confidence level lower limits are set on the Z{prime} mass for several models. Limits are also placed on the mass and gauge coupling of a generic Z{prime}, as well as on the contact interaction mass scales for different helicity structure scenarios.

Search for neutral Higgs Bosons of the minimal supersymmetric standard model decaying to τ pairs in pp̄ collisions at s=1.96TeV

Abstract: We present a search for neutral supersymmetric Higgs bosons decaying to tau pairs produced in pp collisions at square root of s = 1.96 TeV. The data, corresponding to 310 pb(-1) integrated luminosity, were collected with the Collider Detector at Fermilab in run II of the Tevatron. No significant excess above the standard model backgrounds is observed. We set exclusion limits on the production cross section times branching fraction to tau pairs for Higgs boson masses in the range from 90 to 250 GeV/c2.

Search for second-generation scalar leptoquarks in p(p)over-bar collisions at root s=1.96 TeV

Abstract: Results on a search for pair production of second generation scalar leptoquark in p{bar p} collisions at {radical}s=1.96 TeV are reported. The data analyzed were collected by the CDF detector during the 2002-2003 Tevatron Run II and correspond to an integrated luminosity of 198 pb{sup -1}. Leptoquarks (LQ) are sought through their decay into (charged) leptons and quarks, with final state signatures represented by two muons and jets and one muon, large transverse missing energy and jets. We observe no evidence for LQ production and derive 95% C.L. upper limits on the LQ production cross sections as well as lower limits on their mass as a function of {beta}, where {beta} is the branching fraction for LQ {yields} {mu}q.

Top-quark mass measurement from dilepton events at CDF II

Abstract: We report a measurement of the top quark mass using events collected by the CDF II Detector from p{bar p} collisions at {radical}s = 1.96 TeV at the Fermilab Tevatron. We calculate a likelihood function for the top mass in events that are consistent with t{bar t} {yields} {bar b}{ell}{sup -}{bar {nu}}{sub {ell}}b{ell}{prime}{sup +}{nu}{sub {ell}}{prime} decays. The likelihood is formed as the convolution of the leading-order matrix element and detector resolution functions. The joint likelihood is the product of likelihoods for each of 33 events collected in 340 pb{sup -1} of integrated luminosity, yielding a top quark mass M{sub t} = 165.2 {+-} 6.1(stat.) {+-} 3.4(syst.) GeV/c{sup 2}. This first application of a matrix-element technique to t{bar t} {yields} b{ell}{sup +}{nu}{sub {ell}}{bar b}{ell}{prime}{sup -}{bar {nu}}{sub {ell}}, decays gives the most precise single measurement of M{sub t} in dilepton events. Combined with other CDF Run II measurements using dilepton events, we measure M{sub t} = 167.9 {+-} 5.2(stat.) {+-} 3.7(syst.) GeV/c{sup 2}.

Measurement of the inclusive jet cross section using the kT algorithm in pp̄ collisions at s=1.96TeV

Abstract: We report on a measurement of the inclusive jet production cross section in pp-bar collisions at sqrt{s} = 1.96 TeV using data collected with the upgraded Collider Detector at Fermilab in Run II (CDF II) corresponding to an integrated luminosity of 385 pb^-1. Jets are reconstructed using the kt algorithm. The measurement is carried out for jets with rapidity 0.1 < | yjet | < 0.7 and transverse momentum in the range 54 < ptjet < 700 GeV/c. The measured cross section is in good agreement with next-to-leading order perturbative QCD predictions after the necessary non-perturbative parton-to-hadron corrections are included.

Measurement of the tt̄ production cross section in pp̄ collisions at s=1.96TeV using lepton+jets events with jet probability b-tagging

Abstract: The authors present a measurement of the t{bar t} production cross section using events with one charged lepton and jets from p{bar p} collisions at a center-of-mass energy of 1.96 TeV. A b-tagging algorithm based on the probability of displaced tracks coming from the event interaction vertex is applied to identify b quarks from top decay. Using 318 pb{sup -1} of data collected with the CDF II detector, they measure the t{bar t} production cross section in events with at least one restrictive (tight) b-tagged jet and obtain 8.9{sub -1.0}{sup +1.0}(stat.){sub -1.0}{sup +1.1}(syst.) pb. The cross section value assumes a top quark mass of m{sub t} is presented in the paper. This result is consistent with other CDF measurements of the t{bar t} cross section using different samples and analysis techniques, and has similar systematic uncertainties. They have also performed consistency checks by using the b-tagging probability function to vary the signal to background ratio and also using events that have at least two b-tagged jets.

Top quark mass measurement from dilepton events at CDF II with the matrix-element method

Abstract: We describe a measurement of the top quark mass using events with two charged leptons collected by the CDF II detector from p{bar p} collisions with {radical}s = 1.96 TeV at the Fermilab Tevatron. The likelihood in top mass is calculated for each event by convoluting the leading order matrix element describing q{bar q} {yields} t{bar t} {yields} b{ell}{nu}{sub {ell}}{bar b}{ell}{prime} {nu}{sub {ell}}, with detector resolution functions. The presence of background events in the data sample is modeled using similar calculations involving the matrix elements for major background processes. In a data sample with integrated luminosity of 340 pb{sup -1}, we observe 33 candidate events and measure M{sub top} = 165.2 {+-} 6.1(stat.) {+-} 3.4(syst.) GeV/c{sup 2}. This measurement represents the first application of this method to events with two charged leptons and is the most precise single measurement of the top quark mass in this channel.

Measurement of the inclusive jet cross section in pp̄ interactions at s=1.96TeV using a cone-based jet algorithm

Abstract: We present a measurement of the inclusive jet cross section in p (p) over bar interactions at root s>=1.96 TeV using 385 pb(-1) of data collected with the CDF II detector at the Fermilab Tevatron. The results are obtained using an improved cone-based jet algorithm (Midpoint). The data cover the jet transverse momentum range from 61 to 620 GeV/c, extending the reach by almost 150 GeV/c compared with previous measurements at the Tevatron. The results are in good agreement with next-to-leading order perturbative QCD predictions using the CTEQ6.1M parton distribution functions.

Measurement of the helicity of W bosons in top quark decays

Abstract: We measure the branching fraction of the top quark to longitudinally and right-handed polarized W bosons, F{sub 0} and F{sub +}, using approximately 200 pb{sup -1} of p{bar p} collisions collected by the CDF II detector. We analyze two quantities sensitive to the W helicity: the invariant mass of the charged lepton and the bottom-quark jet in the decay t {yields} Wb {yields} {ell}{nu}b (where {ell} = e or {mu}), and the transverse momentum of the charged lepton. We find F{sub 0} = 0.74{sub -0.34}{sup +0.22}, and F{sub +} < 0.27 at the 95% confidence level. These measurements are in agreement with the standard model predictions.

Measurement of the top quark mass with the dynamical likelihood method using lepton plus jets events with b-tags in pp̄ collisions at s=1.96TeV

Abstract: This report describes a measurement of the top quark mass, M{sub top}, with the dynamical likelihood method (DLM) using the CDF II detector at the Fermilab Tevatron. The Tevatron produces top/anti-top (t{bar t}) pairs in p{bar p} collisions at a center-of-mass energy of 1.96 TeV. The data sample used in this analysis was accumulated from March 2002 through August 2004, which corresponds to an integrated luminosity of 318 pb{sup -1}. They use the t{bar t} candidates in the ''lepton+jets'' decay channel, requiring at least one jet identified as a b quark by finding an displaced secondary vertex. The DLM defines a likelihood for each event based on the differential cross section as a function of M{sub top} per unit phase space volume of the final partons, multiplied by the transfer functions from jet to parton energies. The method takes into account all possible jet combinations in an event, and the likelihood is multiplied event by event to derive the top quark mass by the maximum likelihood method. Using 63 t{bar t} candidates observed in the data, with 9.2 events expected from background, they measure the top quark mass to be 173.2{sub -2.4}{sup +2.6}(stat.) {+-} 3.2(syst.) GeV/c{sup 2}, or 173.2{sub -4.0}{sup +4.1} GeV/c{sup 2}.

Search for high-mass resonances decaying to eμ in pp̄ collisions at s=1.96TeV

Abstract: We describe a general search for resonances decaying to a neutral e{mu} final state in p{bar p} collisions at a center-of-mass energy of 1.96 TeV. Using a data sample representing 344 pb{sup -1} of integrated luminosity recorded by the CDF II experiment, we compare Standard Model predictions with the number of observed events for invariant masses between 50 and 800 GeV/c{sup 2}. Finding no significant excess (5 events observed vs. 7.7 {+-} 0.8 expected for M{sub e{mu}} > 100 GeV/c{sup 2}), we set limits on sneutrino and Z' masses as functions of lepton family number violating couplings.

Measurement of mass and width of the excited charmed meson states D10 and D2*0 at CDF

Abstract: This paper describes a measurement of the mass and of the width of two neutral narrow resonances D{sub 1}{sup 0} and D*{sub 2}{sup 0}, both composed of a charm quark and an up antiquark. The difference with respect to the well-known resonance D{sup 0}, also neutral and with the same quark composition, is that the two quarks have an orbital momentum 1, which increases their binding energy. Therefore the mass is larger than that of the D{sup 0}. Since the relative orientation of the spin is the same, in the limit of very large charm mass, the masses of these resonances should be the same; their small difference is predicted by theory and therefore important to measurement to distinguish the different models. These states have been observed in their decay into a kaon and three pions; two of these particles are required to originate from a displaced vertex with respect to the primary interaction vertex, to account for the longer lifetime of the charmed mesons. The resonances parameters have been extracted using a fitting procedure accounting for the expected resonance shape, including effects from detector resolution and background, providing a new best single measurement of the D{sub 1}{sup 0} andmore » D*{sub 2}{sup 0} masses and a competitive measurement of their widths.« less

Measurement of the tt̄ Production Cross Section in pp̄ Collisions at s=1.96TeV Using Missing ET+jets Events with Secondary Vertex b Tagging

Abstract: We present a measurement of the t{bar t} production cross section in p{bar p} collisions at {radical}(s)=1.96 TeV which uses events with an inclusive signature of significant missing transverse energy and jets. This is the first measurement which makes no explicit lepton identification requirements, so that sensitivity to W{yields}{tau}{nu} decays is maintained. Heavy flavor jets from top quark decay are identified with a secondary vertex tagging algorithm. From 311 pb{sup -1} of data collected by the Collider Detector at Fermilab, we measure a production cross section of 5.8{+-}1.2(stat){sub -0.7}{sup +0.9}(syst) pb for a top quark mass of 178 GeV/c2, in agreement with previous determinations and standard model predictions.

Observation of Bs0→ψ(2S) and measurement of the ratio of branching fractions B(Bs0→ψ(2S) /B(Bs0→J/ψ)

Abstract: The authors report the first observation of B{sub s}{sup 0} {yields} {psi}(2S){phi} decay in p{bar p} collisions {radical}s = 1.96 TeV using 360 pb{sup -1} of data collected by the CDF II detector at the Fermilab Tevatron. They observe 20.2 {+-} 5.0 and 12.3 {+-} 4.1 B{sub s}{sup 0} {yields} {psi}(2S){phi} candidates, in {psi}(2S) {yields} {mu}{sup +}{mu}{sup -} and {psi}(2S) {yields} J/{psi}{pi}{sup +}{pi}{sup -} decay modes, respectively. They present a measurement of the relative branching fraction {Beta}(B{sub s}{sup 0} {yields} {psi}(2S){phi})/{Beta}(B{sub s}{sup 0} {yields} J/{psi}{phi}) = 0.52 {+-} 0.13(stat.) {+-} 0.04(syst.) {+-} 0.06(BR) using the {psi}(2S) {yields} {mu}{sup +}{mu}{sup -} decay mode.

Search for a neutral higgs boson decaying to a W boson pair in pp̄ collisions at s=1.96TeV

Abstract: The authors present the results of a search for standard model Higgs boson production with decay to WW*, identified through the leptonic final states e{sup +}e{sup -} {bar {nu}}{nu}, e{sup {+-}}{mu}{sup {-+}} {bar {nu}}{nu} and {mu}{sup +} {mu}{sup -} {bar {nu}}{nu}. This search uses 360 pb{sup -1} of data collected from p{bar p} collisions at {radical}s = 1.96 TeV by the upgraded Collider Detector at Fermilab (CDF II). They observe no signal excess and set 95% confidence level upper limits on the production cross section times branching ratio for the Higgs boson to WW* or any new scalar particle with similar decay products. These upper limits range from 5.5 to 3.2 pb for Higgs boson masses between 120 and 200 GeV/c{sup 2}.

Supporting Technological Literacy Through The Integration Of Engineering, Mathematic, Scientific, And Technological Concepts

Abstract: National emphasis is placed on schools to produce technologically literate students while promoting and teaching pre-engineering education. A technologically literate person understands and effectively communicates basic technological concepts, processes, and interrelationships with engineering, mathematics, science, and society. Federal and state agencies have been funding projects related to these areas over the past decades and will most likely continue to do so. VisTE (Visualization in Technology Education) is a National Science Foundation funded project that promotes technological literacy by attempting to link engineering, mathematics, science, and technology concepts through the study and creation of visualizations. Over a three-year period, the VisTE project team has developed, piloted, and is now field testing 12 units for technology education in grades 6 to 12. The research is based upon five basic areas of investigation during the piloting phase of the integrated VisTE materials: students’ test scores on knowledge of technology, teachers’ ratings of effectiveness of VisTE regarding enhancing students’ understanding of intended learning goals, teachers’ ratings of effectiveness of VisTE regarding enhancing students’ understanding of real-world applications of technology, and students’ selfconcept of ability in technology, mathematics and science, and students’ attitudes toward general technology. The purpose of this research was to provide a process and outcome evaluation for the 12 VisTE instructional units. The data in this presentation and discussion of research is drawn from several sources. Students’ content knowledge and conceptual understanding are measured. Beliefs about their own abilities in learning technology, mathematics, and science, and their attitudes toward technology in general and toward the specific type of technology taught in each unit were measured. Also, data was gathered from teachers through teacher logs. While teaching the VisTE units, teachers were asked to fill in a unit completion log for each unit they taught. Through the logs, teachers reported on several different topics, including their reaction to the unit, their students’ reactions to the unit, aspects of the unit they liked, and aspects they did not like. The study of engineering, mathematics, science, and technology-based content and the application of conceptual modeling, data-driven visualizations, physical modeling, and presentations promote visual literacy. Visual and technical literacy maintain a significant role in successful knowledge and skill development in engineering and technology career paths. Data and information collected from this project is beneficial to pre-engineering education and K-12 outreach through the expansion of research and extension of knowledge. Research-based findings from projects such as VisTE provide for the continued successes in engineering, mathematics, science, and society.

Measurement of the tt̄ production cross section in pp̄ collisions at s=1.96TeV in the all hadronic decay mode

Abstract: We report a measurement of the tt production cross section using the CDF II detector at the Fermilab Tevatron. The analysis is performed using 311 pb{sup -1} of pp collisions at {radical}(s)=1.96 TeV. The data consist of events selected with six or more hadronic jets with additional kinematic requirements. At least one of these jets must be identified as a b-quark jet by the reconstruction of a secondary vertex. The cross section is measured to be {sigma}{sub tt}=7.5{+-}2.1(stat.){sub -2.2}{sup +3.3}(syst.){sub -0.4}{sup +0.5}(lumi.) pb, which is consistent with the standard model prediction.

A Study of Current Trends and Issues for Graphics Education: Results from a Five-Year Follow-Up Survey.

Abstract: During the 1998-1999 academic year, a survey was conducted to look at current trends and issues in the profession of graphics education (Clark & Scales, 1999). The survey solicited information from the membership of the Engineering Design Graphics Division of American Society for Engineering Education related to their view of future areas of growth, problems that exist, and direction the profession of engineering graphics education is headed in the future. This survey, conducted in the spring of 2004, is a five-year follow-up using the same instrument, but with new categories added to provide for current trends in post-secondary graphics education. New areas added to the survey asked questions on certifications, distance education, salaries, and research interests.

A noiseless kilohertz frame rate imaging detector based on microchannel plates read out with the Medipix2 CMOS pixel chip

Abstract: A new hybrid optical imaging detector is described that is being developed for the next generation adaptive optics (AO) wavefront sensors (WFS) for ground-based telescopes. The detector consists of a photocathode and proximity focused microchannel plates (MCPs) read out by the Medipix2 CMOS pixel ASIC. Each pixel of the Medipix2 device measures 55 × 55 μ m 2 and comprises pre-amplifier, a window discriminator and a 14-bit counter. The 256 × 256 Medipix2 array can be read out noiselessly in 287 μ s . The readout can be electronically shuttered down to a temporal window of a few μ s . The Medipix2 is buttable on three sides to produce 512 × ( n * 256 ) pixel devices. Measurements with ultraviolet light yield a spatial resolution of the detector at the Nyquist limit. Sub-pixel resolution can be achieved using centroiding algorithms. For the AO application, very high continuous frame rates of the order of 1 kHz are required for a matrix of 512 × 512 pixels. The design concepts of a parallel readout board are presented that will allow this fast data throughput. The development status of the optical WFS tube is also explained.

Measurement of the ratios of branching fractions B(Bs0→Ds-π+)/ B(B0→D-π+) and B(B+→D̄0π+)/B(B0→D-π+)

Abstract: We report an observation of the decay B-s(0)-> D-s(-)pi(+) in p (p) over bar collisions at root s = 1.96 TeV using 115 pb(-1) of data collected by the CDF II detector at the Fermilab Tevatron. We observe 83 +/- 11(stat) B-s(0)-> D-s(-)pi(+) candidates, representing a large increase in statistics over previous measurements and the first observation of this decay at a p (p) over bar collider. We present the first measurement of the relative branching fraction B(B-s(0)-> D-s(-)pi(+))/B(B-0 -> D-pi(+))=1.32 +/- 0.18(stat)+/- 0.38(syst). We also measure B(B+->(D) over bar (0)pi(+))/B(B-0 -> D-pi(+))=1.97 +/- 0.10(stat)+/- 0.21(syst), which is consistent with previous measurements.

Search for anomalous semileptonic decay of heavy flavor hadrons produced in association with a W boson at CDF II

Abstract: We present a search for anomalous semileptonic decays of heavy flavor hadrons produced in association with a $W$ boson, in proton-antiproton collisions at sqrt{s}=1.96 TeV. We use 162 pb-1 of data collected with the CDF II detector at the Fermilab Tevatron Collider. We select events with one W boson and at least one jet with an identified secondary vertex. In the jets with a secondary vertex we look for a semileptonic decay to a muon. We compare the number of jets with both a secondary vertex and a semileptonic decay, and the kinematic properties of these jets, with the standard model expectation of W plus heavy flavor production and decay. No discrepancy is seen between the observation and the expectation, and we set limits on the production cross section of a B-like hadron with an anomalously high semileptonic branching ratio.

Observation of $B^0_s - \bar{B}^0_s$ Oscillations

Abstract: We report the observation of Bs-Bsbar oscillations from a time-dependent measurement of the Bs-Bsbar oscillation frequency Delta ms. Using a data sample of 1 fb^-1 of p-pbar collisions at sqrt{s}=1.96 TeV collected with the CDF II detector at the Fermilab Tevatron, we find signals of 5600 fully reconstructed hadronic Bs decays, 3100 partially reconstructed hadronic Bs decays, and 61500 partially reconstructed semileptonic Bs decays. We measure the probability as a function of proper decay time that the Bs decays with the same, or opposite, flavor as the flavor at production, and we find a signal for Bs-Bsbar oscillations. The probability that random fluctuations could produce a comparable signal is 8 X 10^-8, which exceeds 5 sigma significance. We measure Delta ms = 17.77 +- 0.10 (stat) +- 0.07 (syst) ps^-1 and extract |Vtd/Vts| = 0.2060 +- 0.0007 (exp) + 0.0081 - 0.0060 (theor).

Robotic mounting of ATLAS barrel SCT modules

Abstract: The 2112 silicon detector modules of the barrel part of the ATLAS SemiConductor Tracker (SCT) have been mounted on their carbon fibre support structure. Module insertion, placement and fixing were performed by robotic assembly tooling. We report on our experience with this assembly method. Part of the mounting sequence involves a partial survey of elements of the support structure which is needed to align the modules properly during insertion. An analysis of these data is used to estimate the positional accuracy of the robots.

Search for higgs bosons decaying to bb̄ and produced in association with W bosons in pp̄ collisions at s=1.96TeV

Abstract: The authors present a search for the standard model Higgs boson decaying into b{bar b} and produced in association with W bosons in p{bar p} collisions at {radical}s = 1.96 TeV. This search uses 320 pb{sup -1} of the dataset accumulated by the upgraded Collider Detector at Fermilab. Events are selected that have a high-transverse momentum electron or muon, missing transverse energy, and two jets, at least one of which is consistent with the hadronization of a b quark. Both the number of events and the dijet mass distribution are consistent with standard model background expectations, and they set 95% confidence level upper limits on the production cross section times branching ratio for the Higgs boson or any new particle with similar decay kinematics. These upper limits range from 10 pb for m{sub H} = 110 GeV/c{sup 2} to 3 pb for m{sub H} = 150 GeV/c{sup 2}.