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Buehler, M.

Publications and source records attributed to Buehler, M..

At least 37 records · Page 2
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DOE OSTI2016

Development of aluminum-stabilized superconducting cables for the Mu2e detector solenoid

Here, the Mu2e experiment at Fermilab is designed to measure the rare process of direct muon-to-electron conversion in the field of a nucleus. The experiment comprises a system of three superconducting solenoids, which focus secondary muons from the production target and transport them to an aluminum stopping target, while minimizing the associated background. The Detector Solenoid (DS) is the last magnet in the transport line and its main functions are to provide a graded field in the region of the stopping target as well as a precision magnetic field in a volume large enough to house the tracker downstream of the stopping target. The Detector Solenoid coils are designed to be wound using NbTi Rutherford cables conformed in high purity aluminum for stabilization and then cold-worked for strength. Two types of Al-stabilized conductor are required to build the DS coils, one for the gradient section and one for the spectrometer section of the solenoid. The dimensions are optimized to generate the required field profile when the same current is transported in both conductors. The conductors contain NbTi Rutherford cables with 12 (DS1) and 8 (DS2) strands respectively and are manufactured by two different vendors. This paper describes the results of the manufacturing of production lengths of the Al-stabilized cables needed to build the Mu2e Detector Solenoid as well as the testing campaigns and main results. The main cable properties and results of electrical and mechanical tests are summarized and discussed for each stage of the cable development process. Results are compared to design values to show how the production cables satisfy all the design criteria starting from the NbTi wires to the Al-stabilized cables.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Study of double parton interactions in diphoton + dijet events in $p\bar{p}$ collisions at $\sqrt{s} = 1.96$ TeV

We use a sample of diphoton+dijet events to measure the effective cross section of double parton interactions, which characterizes the area containing the interacting partons in proton-antiproton collisions, and find it to be σeff=19.3±1.4(stat)±7.8(syst) mb. The sample was collected by the D0 detector at the Fermilab Tevatron collider in pp¯ collisions at s=1.96 TeV and corresponds to an integrated luminosity of 8.7 fb-1.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Evidence for Simultaneous Production of J/ψ and Υ Mesons

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

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Tevatron combination of single-top-quark cross sections and determination of the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element $\bf V_{tb}$

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

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Simultaneous measurement of forward-backward asymmetry and top polarization in dilepton final states from $t\bar t$ production at the Tevatron

We present a simultaneous measurement of the forward-backward asymmetry and the top-quark polarization in tt¯ production in dilepton final states using 9.7 fb –1 of proton-antiproton collisions at √s=1.96 TeV with the D0 detector. To reconstruct the distributions of kinematic observables we employ a matrix element technique that calculates the likelihood of the possible tt¯ kinematic configurations. After accounting for the presence of background events and for calibration effects, we obtain a forward-backward asymmetry of A tt¯ =(15.0±6.4(stat)±4.9(syst))% and a top-quark polarization times spin analyzing power in the beam basis of κP=(7.2±10.5(stat)±4.2(syst))%, with a correlation of –56% between the measurements. If we constrain the forward-backward asymmetry to its expected standard model value, we obtain a measurement of the top polarization of κP=(11.3±9.1(stat)±1.9(syst))%. If we constrain the top polarization to its expected standard model value, we measure a forward-backward asymmetry of A tt¯ =(17.5±5.6(stat)±3.1(syst))%. A combination with the D0 A tt¯ measurement in the lepton+jets final state yields an asymmetry of Att¯=(11.8±2.5(stat)±1.3(syst))%. Within their respective uncertainties, all these results are consistent with the standard model expectations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Measurement of the Effective Weak Mixing Angle in p p ¯ → Z / γ * → e + e - Events

We present a measurement of the fundamental parameter of the standard model, the weak mixing angle sin 2 θ ℓ eff which determines the relative strength of weak and electromagnetic interactions, in pp¯→Z/γ*→e + e - events at a center of mass energy of 1.96 TeV, using data corresponding to 9.7 fb -1 of integrated luminosity collected by the D0 detector at the Fermilab Tevatron. The effective weak mixing angle is extracted from the forward-backward charge asymmetry as a function of the invariant mass around the Z boson pole. The measured value of sin 2 θ ℓ eff =0.23147±0.00047 is the most precise measurement from light quark interactions to date, with a precision close to the best LEP and SLD results.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Measurement of the ratio of inclusive cross sections $\sigma (p\bar{p} \rightarrow Z+2~b~\text{jets}) / \sigma (p\bar{p} \rightarrow Z+ \text{2 jets})$ in $p\bar{p}$ collisions at $\sqrt s=1.96$ TeV

In this study, we measure the ratio of cross sections, σ(pp¯ → Z + 2 b jets)/σ(pp¯ → Z + 2 jets), for associated production of a Z boson with at least two jets with transverse momentum p jet T > 20 GeV and pseudorapidity |η jet | < 2.5. This measurement uses data corresponding to an integrated luminosity of 9.7 fb –1 collected by the D0 experiment in Run II of Fermilab’s Tevatron pp¯ Collider at a center-of-mass energy of 1.96 TeV. The measured integrated ratio of 0.0236 ± 0.0032(stat) ± 0.0035(syst) is in agreement with predictions from next-to-leading-order perturbative QCD and the Monte Carlo event generators PYTHIA and ALPGEN .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Measurement of the $B_s^0$ Lifetime in the Flavor-Specific Decay Channel $B_s^0 \to D_s^- \mu^+\nu X$

We present an updated measurement of the B s 0 lifetime using the semileptonic decays B s 0 → D s - μ + ν X , with D s - → ϕ π - and ϕ → K + K - (and the charge conjugate process). This measurement uses the full Tevatron Run II sample of proton-antiproton collisions at s = 1.96 TeV , comprising an integrated luminosity of 10.4 fb − 1 . We find a flavor-specific lifetime τ fs ( B s 0 ) = 1.479 ± 0.010 ( stat ) ± 0.021 ( syst ) ps . This technique is also used to determine the B 0 lifetime using the analogous B 0 → D - μ + ν X decay with D - → ϕ π - and ϕ → K + K - , yielding τ ( B 0 ) = 1.534 ± 0.019 ( stat ) ± 0.021 ( syst ) ps . Both measurements are consistent with the current world averages, and the B s 0 lifetime measurement is one of the most precise to date. Taking advantage of the cancellation of systematic uncertainties, we determine the lifetime ratio τ fs ( B s 0 ) / τ ( B 0 ) = 0.964 ± 0.013 ( stat ) ± 0.007 ( syst ) .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

11 T Twin-Aperture Nb$_3$Sn Dipole Development for LHC Upgrades

FNAL and CERN are developing a twin-aperture 11 T Nb3Sn dipole suitable for installation in the LHC. This paper describes the design and parameters of the 11 T dipole developed at FNAL for the LHC upgrades in both single-aperture and twin-aperture configurations, and presents details of the constructed dipole models. Results of studies of magnet quench performance, quench protection and magnetic measurements performed using short 1 m long coils in the dipole mirror and single-aperture configurations are reported and discussed.

43 PARTICLE ACCELERATORS↗
DOE OSTI2014

Thermal design of the Mu2e detector solenoid

The reference design for a superconducting detector solenoid (DS) for the Mu2e experiment has been completed. In this study, the main functions of the DS are to provide a graded field in the region of the stopping target, which ranges from 2 to 1 T and a uniform precision magnetic field of 1 T in a volume large enough to house a tracker downstream of the stopping target. The inner diameter of the magnet cryostat is 1.9 m and the length is 10.9 m. The gradient section of the magnet is about 4 m long and the spectrometer section with a uniform magnetic field is about 6 m long. The inner cryostat wall supports the stopping target, tracker, calorimeter and other equipment installed in the DS. This warm bore volume is under vacuum during operation. It is sealed on one end by the muon beam stop, while it is open on the other end where it interfaces with the Transport Solenoid. The operating temperature of the magnetic coil is 4.7 K and is indirectly cooled with helium flowing in a thermosiphon cooling scheme. This paper describes the thermal design of the solenoid, including the design aspects of the thermosiphon for the coil cooling, forced flow cooling of the thermal shields with 2 phase LN2 (Liquid Nitrogen) and the transient studies of the cool down of the cold mass as well.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Measurement of the direct C P -violating parameter A C P in the decay D + → K - π + π +

We measure the direct C P -violating parameter A C P for the decay of the charged charm meson, D + → K - π + π + (and charge conjugate), using the full 10.4 fb - 1 sample of p p ¯ collisions at s = 1.96 TeV collected by the D0 detector at the Fermilab Tevatron collider. We extract the raw reconstructed charge asymmetry by fitting the invariant mass distributions for the sum and difference of charge-specific samples. This quantity is then corrected for detector-related asymmetries using data-driven methods and for possible physics asymmetries (from B → D processes) using input from Monte Carlo simulation. We measure A C P = [ - 0.16 ± 0.15 ( stat ) ± 0.09 ( syst ) ] % , which is consistent with zero, as expected from the standard model prediction of C P conservation, and is the most precise measurement of this quantity to date.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗