Engineering topics
Bross, A
Publications and source records attributed to Bross, A.
Z(gamma) production and limits on anomalous ZZ(gamma) and Z(gamma gamma) couplings in p(p)over-bar collisions at root s 1.96 TeV
We present a measurement of p{bar p} {yields} Z{sub {gamma}} {yields} {ell}{sup +}{ell}{sup -}{sub {gamma}} ({ell} = e, {mu}) production with a data sample corresponding to an integrated luminosity of 6.2 fb{sup -1} collected by the D0 detector at the Fermilab Tevatron p{bar p} Collider. The results of the electron and muon channels are combined, and we measure the total production cross section and the differential cross section d{sigma}/dp{sub T}{sup {gamma}}, where p{sub T}{sup {gamma}} is the momentum of the photon in the plane transverse to the beam line. The results obtained are consistent with the standard model predictions from next-to-leading order use ttransverse momentum spectrum of the photon to place limits on anomalous ZZ{gamma} and Z{gamma}{gamma} couplings.
Measurement of the CP-violating phase phi sJ/psi phi using the flavor-tagged decay Bs(0) -> J/psi phi in 8 fb(-1) of p(p)over-bar collisions
We report an updated measurement of the CP-violating phase, {phi}{sub s}{sup J/{psi}{phi}} and the decay-width difference for the two mass eigenstates, {Delta}{Gamma}{sub s}, from the flavor-tagged decay B{sub s}{sup 0} {yields} J/{psi}{phi}. The data sample corresponds to an integrated luminosity of 8.0 fb{sup -1} accumulated with the D0 detector using p{bar p} collisions at {radical}s = 1.96 TeV produced at the Fermilab Tevatron collider. The 68% Bayesian credibility intervals, including systematic uncertainties, are {Delta}{Gamma}{sub s} = 0.163{sub -0.064}{sup +0.065} ps{sup -1} and {phi}{sub s}{sup J}/{psi}{phi} = -0.55{sub -0.36}{sup +0.38}. The p-value for the Standard Model point is 29.8%.
Search for anomalous Wtb couplings in single top quark production in p(p)over-bar collisions at root s=1.96 TeV
We present new direct constraints on a general Wtb interaction using data corresponding to an integrated luminosity of 5.4 fb{sup -1} collected by the D0 detector at the Tevatron p{bar p} collider. The standard model provides a purely left-handed vector coupling at the Wtb vertex, while the most general, lowest dimension Lagrangian allows right-handed vector and left- or right-handed tensor couplings as well. We obtain precise limits on these anomalous couplings by comparing the data to the expectations from different assumptions on the Wtb coupling.
Search for Higgs bosons decaying to tau(+)tau(-) pairs in p(p)over-bar collisions at root s=1.96 TeV
We present a search for the production of neutral Higgs bosons decaying into {tau}{sup +}{tau}{sup -} pairs in p{bar p} collisions at a center-of-mass energy of 1.96 TeV. The data, corresponding to an integrated luminosity of 5.4 fb{sup -1}, were collected by the D0 experiment at the Fermilab Tevatron Collider. We set upper limits at the 95% C.L. on the product of production cross section and branching ratio for a scalar resonance decaying into {tau}{sup +}{tau}{sup -} pairs, and we interpret these limits as limits on the production of Higgs bosons in the minimal supersymmetric standard model (MSSM) and as constraints in the MSSM parameter space.
Measurement of the relative branching ratio of B s 0 → J / ψ f 0 ( 980 ) to B s 0 → J / ψ ϕ
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Forward-backward asymmetry in top quark-antiquark production
We present a measurement of forward-backward asymmetry in top quark-antiquark production in proton-antiproton collisions in the final state containing a lepton and at least four jets. Using a data set corresponding to an integrated luminosity of 5.4 fb{sup -1}, collected by the D0 experiment at the Fermilab Tevatron Collider, we measure the t{bar t} forward-backward asymmetry to be (9.2 {+-} 3.7)% at the reconstruction level. When corrected for detector acceptance and resolution, the asymmetry is found to be (19.6 {+-} 6.5)%. We also measure a corrected asymmetry based on the lepton from a top quark decay, found to be (15.2 {+-} 4.0)%. The results are compared to predictions based on the next-to-leading-order QCD generator mc@nlo. The sensitivity of the measured and predicted asymmetries to the modeling of gluon radiation is discussed.
Model-independent measurement of t-channel single top quark production in p(p)over-bar collisions at,root s=1.96 TeV
We present a model-independent measurement of t-channel electroweak production of single top quarks in p{bar p} collisions at {radical}s = 1.96 TeV. Using 5.4 fb{sup -1} of integrated luminosity collected by the D0 detector at the Fermilab Tevatron Collider, and selecting events containing an isolated electron or muon, missing transverse energy and one or two jets originating from the fragmentation of b quarks, we measure a cross section {sigma}(p{bar p} {yields} tqb + X) = 2.90 {+-} 0.59 (stat + syst) pb for a top quark mass of 172.5 GeV. The probability of the background to fluctuate and produce a signal as large as the one observed is 1.6 x 10{sup -8}, corresponding to a significance of 5.5 standard deviations.
The US Muon Accelerator Program
An accelerator complex that can produce ultra-intense beams of muons presents many opportunities to explore new physics. A facility of this type is unique in that, in a relatively straightforward way, it can present a physics program that can be staged and thus move forward incrementally, addressing exciting new physics at each step. At the request of the US Department of Energy's Office of High Energy Physics, the Neutrino Factory and Muon Collider Collaboration (NFMCC) and the Fermilab Muon Collider Task Force (MCTF) have recently submitted a proposal to create a Muon Accelerator Program that will have, as a primary goal, to deliver a Design Feasibility Study for an energy-frontier Muon Collider by the end of a 7 year R&D program. This paper presents a description of a Muon Collider facility and gives an overview of the proposal.
The MuCool Test Area and RF Program
The MuCool RF Program focuses on the study of normal conducting RF structures operating in high magnetic field for applications in muon ionization cooling for Neutrino Factories and Muon Colliders. Here we give an overview of the program, which includes a description of the test facility and its capabilities, the current test program, and the status of a cavity that can be rotated in the magnetic field, which allows for a detailed study of the maximum stable operating gradient vs. magnetic field strength and angle.
Rectangular Box Cavity Tests in Magnetic Field for Muon Cooling
Muon cooling requires high-gradient normal conducting cavities operating in multi-Tesla magnetic fields for muon beam focusing in an ionization cooling channel. Recent experience with an 805-MHz pillbox cavity at the Fermilab MuCool Test Area has shown a significant drop in accelerating field performance for the case of parallel electric and magnetic fields. It has been suggested that having the magnetic field perpendicular to the electric field should provide magnetic insulation and suppress breakdown. An 805-MHz Cu rectangular box cavity was built for testing with the fields perpendicular. It was mounted on an adjustable support to vary the angle between the rf electric and external magnetic field. We report on the design and initial operation of the rectangular box cavity.