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Buchanan, E.

Publications and source records attributed to Buchanan, E..

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

The ABC130 barrel module prototyping programme for the ATLAS strip tracker

For the Phase-II Upgrade of the ATLAS Detector [1], its Inner Detector, consisting of silicon pixel, silicon strip and transition radiation sub-detectors, will be replaced with an all new 100% silicon tracker, composed of a pixel tracker at inner radii and a strip tracker at outer radii. The future ATLAS strip tracker will include 11,000 silicon sensor modules in the central region (barrel) and 7,000 modules in the forward region (end-caps), which are foreseen to be constructed over a period of 3.5 years. The construction of each module consists of a series of assembly and quality control steps, which were engineered to be identical for all production sites. In order to develop the tooling and procedures for assembly and testing of these modules, two series of major prototyping programs were conducted: an early program using readout chips designed using a 250 nm fabrication process (ABCN-250) [2,2] and a subsequent program using a follow-up chip set made using 130 nm processing (ABC130 and HCC130 chips). This second generation of readout chips was used for an extensive prototyping program that produced around 100 barrel-type modules and contributed significantly to the development of the final module layout. This paper gives an overview of the components used in ABC130 barrel modules, their assembly procedure and findings resulting from their tests.

47 OTHER INSTRUMENTATION↗
DOE OSTI2019

Measurement of the ratio of branching fractions of the decays $Λ_{b}^{o}$ → ψ(2S)Λ and $Λ_{b}^{o}$ → J /ψΛ

Using pp collisions corresponding to 3 fb –1 integrated luminosity, recorded by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV, the ratio of branching fractions B ($Λ_{b}^{o}$ → ψ(2S)Λ)/ B ($Λ_{b}^{o}$ → J /ψΛ) = 0.513 ± 0.023(stat) ± 0.016(syst) ± 0.011 ( B ) is determined. The first uncertainty is statistical, the second is systematic and the third is due to the external branching fractions used.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

A measurement of the CP asymmetry difference between Λ c + → pK – K + and pπ – π + decays

The difference between the CP asymmetries in the decays Λ c + → pK – K + and Λ c + → pπ – π + is presented. Proton-proton collision data taken at centre-of-mass energies of 7 and 8 TeV collected by the LHCb detector in 2011 and 2012 are used, corresponding to an integrated luminosity of 3 fb –1 . The Λ c + candidates are reconstructed as part of the Λ b o → Λ c + μ – X decay chain. In order to maximize the cancellation of production and detection asymmetries in the difference, the final-state kinematic distributions of the two samples are aligned by applying phase-space-dependent weights to the Λ c + → pπ – π + sample. This alters the definition of the integrated CP asymmetry to A CP wgt (pπ – π + ).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

First measurement of the CP -violating phase $ {\phi}_s^{d\overline{d}} $ in B s o → (K + π – )(K – π + ) decays

A flavour-tagged decay-time-dependent amplitude analysis of B s o → (K + π – )(K – π + ) decays is presented in the K ± π ∓ mass range from 750 to 1600MeV/c 2 . The analysis uses pp collision data collected with the LHCb detector at centre-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3.0 fb –1 . Several quasi-two-body decay modes are considered, corresponding to K ± π ∓ combinations with spin 0, 1 and 2, which are dominated by the K o * (800)0 and K o * (1430) o , the K*(892) o and the K 2 * (1430) o resonances, respectively. The longitudinal polarisation fraction for the B 0 s → K*(892)°K¯*(892) 0 decay is measured as f L = 0.208 ± 0.032 ± 0.046, where the first uncertainty is statistical and the second is systematic. The first measurement of the mixing-induced CP -violating phase, $ {\phi}_s^{d\overline{d}} $, in b → dd¯s transitions is performed, yielding a value of $ {\phi}_s^{d\overline{d}} $ = –0.10 ± 0.13 (stat) ± 0.14 (syst) rad.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Measurement of the Ratio of Branching Fractions B ( B c + → J / ψ τ + ν τ ) / B ( B c + → J / ψ μ + ν μ )

A measurement is reported of the ratio of branching fractions R( J /ψ) = B( B + c → J /ψτ + ν τ )/B( B + c → J /ψμ + ν μ ), where the τ + lepton is identified in the decay mode τ + → μ + ν μ ¯ν τ . This analysis uses a sample of proton-proton collision data corresponding to 3.0 fb –1 of integrated luminosity recorded with the LHCb experiment at center-of-mass energies of 7 and 8 TeV. A signal is found for the decay B + c → J /ψτ + ν τ at a significance of 3 standard deviations corrected for systematic uncertainty, and the ratio of the branching fractions is measured to be R( J /ψ) = 0.71 ± 0.17 (stat) ± 0.18 (syst). This result lies within 2 standard deviations above the range of central values currently predicted by the standard model.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Search for the lepton-flavour violating decays B (s) o → e ± μ ∓

A search for the lepton-flavour violating decays B (s) o → e ± μ ∓ and B o → e ± μ ∓ is performed based on a sample of proton-proton collision data corresponding to an integrated luminosity of 3 fb –1 , collected with the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The observed yields are consistent with the background-only hypothesis. Upper limits on the branching fraction of the B ( s) o → e ± μ ∓ decays are evaluated both in the hypotheses of an amplitude completely dominated by the heavy eigenstate and by the light eigenstate.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Updated determination of D 0 – D ¯ 0 mixing and C P violation parameters with D 0 → K + π – decays

We report measurements of charm-mixing parameters based on the decay-time-dependent ratio of D 0 →K + π – to D 0 →K – π + rates. The analysis uses a data sample of proton-proton collisions corresponding to an integrated luminosity of 5.0 fb –1 recorded by the LHCb experiment from 2011 through 2016. Assuming charge-parity ( CP ) symmetry, the mixing parameters are determined to be x' 2 =(3.9±2.7)×10 –5 , y'=(5.28±0.52)×10 –3 , and R D =(3.454±0.031)×10 –3 . Without this assumption, the measurement is performed separately for D 0 and D¯ 0 mesons, yielding a direct CP-violating asymmetry A D =(–0.1±9.1)×10 –3 , and magnitude of the ratio of mixing parameters 1.00 < |q/p| < 1.35 at the 68.3% confidence level. All results include statistical and systematic uncertainties and improve significantly upon previous single-measurement determinations. No evidence for CP violation in charm mixing is observed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Measurement of branching fractions of charmless four-body Λ o b and Ξ o b decays

A search for charmless four-body decays of Λ o b and Ξ o b baryons with a proton and three charged mesons (either kaons or pions) in the final state is performed. The data sample used was recorded in 2011 and 2012 with the LHCb experiment and corresponds to an integrated luminosity of 3 fb –1 . Six decay modes are observed, among which Λ o b → pK – π + π – , Λ o b → pK – K + K – , Ξ o b → pK – π + π – and Ξ o b → pK – π + K – are established for the first time. Their branching fractions (including the ratio of hadronisation fractions in the case of the Ξ o b baryon) are determined relative to the Λ o b → Λ c + π – decay.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Search for weakly decaying b -flavored pentaquarks

Investigations of the existence of pentaquark states containing a single b (anti)quark decaying weakly into four specific final states J/ψK + π – p, J/ψK – π – p, J/ψK – π + p, and J/ψΦ(1020)p are reported. The data sample corresponds to an integrated luminosity of 3.0 fb –1 in 7 and 8 TeV pp collisions acquired with the LHCb detector. Signals are not observed and upper limits are set on the product of the production cross section times branching fraction with respect to that of the Λ 0 b .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Search for Dark Photons Produced in 13 TeV p p Collisions

Searches are performed for both promptlike and long-lived dark photons, A ', produced in proton-proton collisions at a center-of-mass energy of 13 TeV, using A ' → μ + μ - decays and a data sample corresponding to an integrated luminosity of 1.6 fb -1 collected with the LHCb detector. The promptlike A ' search covers the mass range from near the dimuon threshold up to 70 GeV, while the long-lived A; search is restricted to the low-mass region 214 < m ( A ') < 350 MeV. No evidence for a signal is found, and 90% confidence level exclusion limits are placed on the γ– A ' kinetic-mixing strength. The constraints placed on prompt like dark photons are the most stringent to date for the mass range 10.6 < m ( A ') < 70 GeV, and are comparable to the best existing limits for m ( A ') < 0.5 GeV. The search for long-lived dark photons is the first to achieve sensitivity using a displaced-vertex signature.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗