Engineering Papers⌕ Search

Engineering topics

Buchanan, E.

Publications and source records attributed to Buchanan, E..

At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Measurement of the b -Quark Production Cross Section in 7 and 13 TeV p p Collisions

Measurements of the cross section for producing b quarks in the reaction pp→bbX are reported in 7 and 13 TeV collisions at the LHC as a function of the pseudorapidity η in the range 2 < η < 5 covered by the acceptance of the LHCb experiment. The measurements are done using semileptonic decays of b-flavored hadrons decaying into a ground-state charmed hadron in association with a muon. The cross sections in the covered η range are 72.0±0.3±6.8 and 154.3±1.5±14.3 μb for 7 and 13 TeV. The ratio is 2.14±0.02±0.13, where the quoted uncertainties are statistical and systematic, respectively. The agreement with theoretical expectation is good at 7 TeV, but differs somewhat at 13 TeV. The measured ratio of cross sections is larger at lower η than the model prediction.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Measurement of forward t t - , W + b b ¯ and W + c c ¯ production in pp collisions at s = 8 TeV

The production of $t\bar{t}$, W + $b\bar{b}$ and W + $c\bar{c}$ is studied in the forward region of proton–proton collisions collected at a centre-of-mass energy of 8 TeV by the LHCb experiment, corresponding to an integrated luminosity of 1.98±0.02 fb -1 . The W bosons are reconstructed in the decays W→ℓν, where ℓ denotes muon or electron, while the b and c quarks are reconstructed as jets. All measured cross-sections are in agreement with next-to-leading-order Standard Model predictions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Amplitude analysis of B + → J / ψ Φ K + decays

The first full amplitude analysis of B + →J/ψΦK + with J/ψ→μ + μ – , Φ→K + K – decays is performed with a data sample of 3 fb –1 of pp collision data collected at √s = 7 and 8 TeV with the LHCb detector. The data cannot be described by a model that contains only excited kaon states decaying into ΦK + , and four J/ψΦ structures are observed, each with significance over 5 standard deviations. The quantum numbers of these structures are determined with significance of at least 4 standard deviations. The lightest has mass consistent with, but width much larger than, previous measurements of the claimed X(4140) state. The model includes significant contributions from a number of expected kaon excitations, including the first observation of the K*(1680) + →ΦK + transition.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Observation of J / ψ &straightphi; Structures Consistent with Exotic States from Amplitude Analysis of B + → J / ψ &straightphi; K + Decays

The first full amplitude analysis of B + → J/ψ&straightphi;K + with J/ψ → μ + μ - , &straightphi; → K + K - decays is performed with a data sample of 3 fb -1 of pp collision data collected at $\sqrt{s}$ =7 and 8 TeV with the LHCb detector. The data cannot be described by a model that contains only excited kaon states decaying into &straightphi;K + , and four J/ψ&straightphi; structures are observed, each with significance over 5 standard deviations. The quantum numbers of these structures are determined with significance of at least 4 standard deviations. The lightest has mass consistent with, but width much larger than, previous measurements of the claimed X(4140) state.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Observation of the decay B s 0 → Φ π + π – and evidence for B 0 → Φ π + π –

The first observation of the rare decay B 0 s →Φπ + π – and evidence for B 0 →Φπ + π – are reported, using pp collision data recorded by the LHCb detector at center-of-mass energies √s = 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb –1 . The branching fractions in the π + π – invariant mass range 400 < m(π + π – ) < 1600 MeV/c 2 are [3.48±0.23±0.17±0.35]×10 –6 and [1.82±0.25±0.41±0.14]×10 –7 for B 0 s →Φπ + π – and B 0 →Φπ + π – respectively, where the uncertainties are statistical, systematic and from the normalization mode B 0 s →ΦΦ. A combined analysis of the π + π – mass spectrum and the decay angles of the final-state particles identifies the exclusive decays B 0 s →Φf 0 (980), B 0 s →Φf 2 (1270), and B 0 s →Φρ 0 with branching fractions of [1.12±0.16+0.09–0.08±0.11]×10 –6 , [0.61±0.13+0.12–0.05±0.06]×10 –6 and [2.7±0.7±0.2±0.2]×10 –7 , respectively.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

First Experimental Study of Photon Polarization in Radiative B s 0 Decays

The polarization of photons produced in radiative B 0 s decays is studied for the first time. The data are recorded by the LHCb experiment in pp collisions corresponding to an integrated luminosity of 3 fb –1 at center-of-mass energies of 7 and 8 TeV. A time-dependent analysis of the B 0 s →Φγ decay rate is conducted to determine the parameter A Δ , which is related to the ratio of right- over left-handed photon polarization amplitudes in b→sγ transitions. A value of A Δ = –0.98 +0.46 –0.52 +0.23 –0.20 is measured. This result is consistent with the standard model prediction within 2 standard deviations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Search for the CP-violating strong decays η → π + π - and η' (958)→ π + π -

A search for the CP-violating strong decays η→π + π - and η'(958)→π + π - has been performed using approximately 2.5×10 7 events of each of the decays D + →π + π + π - and D$+\atop{s}$→π + π + π - , recorded by the LHCb experiment. The data set corresponds to an integrated luminosity of 3.0 fb -1 of pp collision data recorded during LHC Run 1 and 0.3 fb -1 recorded in Run 2. No evidence is seen for D$+\atop{s}$→π + η(') with η(')→π + π - , and upper limits at 90% confidence level are set on the branching fractions, B(η→π + π - )<1.6×10 -5 and B(η'→π + π - )<1.8×10 -5 . The limit for the η decay is comparable with the existing one, while that for the η' is a factor of three smaller than the previous limit.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Measurement of C P Violation in B 0 → D + D – Decays

The CP violation observables S and C in the decay channel B 0 →D + D – are determined from a sample of proton-proton collisions at center-of-mass energies of 7 and 8 TeV, collected by the LHCb experiment and corresponding to an integrated luminosity of 3 fb –1 . The observable S describes CP violation in the interference between mixing and the decay amplitude, and C parametrizes direct CP violation in the decay. The following values are obtained from a flavor-tagged, decay-time-dependent analysis: S = –0.54 +0.17 –0.16 (stat)±0.05(syst), C = 0.26 +0.18 –0.17 (stat)±0.02(syst). These values provide evidence for CP violation at a significance level of 4.0 standard deviations. The phase shift due to higher-order standard model corrections is constrained to a small value of ΔΦ = –0.16 +0.19 –0.21 rad.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Search for the suppressed decays B + → K + K + π – and B + → π + π + K –

A search is made for the highly-suppressed B meson decays B + → K + K + π – and B + → π + π + K – using a data sample corresponding to an integrated luminosity of 3.0 fb–1collected by the LHCb experiment in proton–proton collisions at centre-of-mass energies of 7 and 8 TeV. No evidence is found for the decays, and upper limits at 90% confidence level are determined to be $\mathscr{B}$(B + →K + K + π – ) < 1.1 × 10 –8 and $\mathscr{B}$(B + →π + π + K – ) < 4.6 × 10 –8 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Search for Higgs-like bosons decaying into long-lived exotic particles

A search is presented for massive long-lived particles, in the 20–60 GeV/c 2 mass range with lifetimes between 5 and 100 ps. The dataset used corresponds to 0.62 fb -1 of proton-proton collision data collected by the LHCb detector at √s = 7TeV. The particles are assumed to be pair-produced by the decay of a Higgs-like boson with mass between 80 and 140 GeV/c 2 . No excess above the background expectation is observed and limits are set on the production cross-section as a function of the long-lived particle mass and lifetime and of the Higgs-like boson mass.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Differential branching fraction and angular moments analysis of the decay B 0 → K + π - μ + μ - in the K 0,2 * (1430)⁰ region

Here, measurements of the differential branching fraction and angular moments of the decay B 0 → K + π - μ + μ - in the K + π - invariant mass range 1330 < m(K + π - ) < 1530 MeV/c 2 are presented. Proton-proton collision data are used, corresponding to an integrated luminosity of 3 fb -1 collected by the LHCb experiment. Differential branching fraction measurements are reported in five bins of the invariant mass squared of the dimuon system, q 2 , between 0.1 and 8.0 GeV 2 /c 4 . For the first time, an angular analysis sensitive to the S-, P- and D-wave contributions of this rare decay is performed. The set of 40 normalised angular moments describing the decay is presented for the q 2 range 1.1-6.0 GeV 2 /c 4 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Measurements of the S-wave fraction in $B^0$ → $K^+π^-μ^+μ^-$ decays and the $B^0 → K^*(892)^0μ^+μ^-$ differential branching fraction

A measurement of the differential branching fraction of the decay $B^0 → K^*(892)^0$ $μ^+μ^-$ is presented together with a determination of the S-wave fraction of the $K^+π^-$ system in the decay $B^0 → K^+π^-μ^+μ^-$. The analysis is based on pp-collision data corresponding to an integrated luminosity of 3 fb -1 collected with the LHCb experiment. The measurements are made in bins of the invariant mass squared of the dimuon system, q 2 . Precise theoretical predictions for the differential branching fraction of $B^0 → K^*(892)^0 μ^+μ^-$ decays are available for the q 2 region 1.1 < q 2 < 6.0 GeV 2 / c 4 . In this q 2 region, for the $K^+π^-$ invariant mass range 796 < $m_{K_π}$ < 996 MeV/c 2 , the S-wave fraction of the $K^+π^-$ system in $B^0 → K^+π^-μ^+μ^-$ decays is found to be F S = 0.101 &#x00B1;<!-- ± --> 0.017 ( s t a t ) &#x00B1;<!-- ± --> 0.009 ( s y s t ) , and the differential branching fraction of $B^0 → K^*(892)^0 μ^+μ^-$ decays is determined to be d B / d q 2 = ( 0. 392 &#x2212;<!-- - --> 0.019 + 0.020 ( s t a t ) &#x00B1;<!-- ± --> 0.010 ( s y s t ) &#x00B1;<!-- ± --> 0.027 ( n o r m ) ) &#x00D7;<!-- × --> 1 0 &#x2212;<!-- - --> 7 c 4 / G e V 2 . The differential branching fraction measurements presented are the most precise to date and are found to be in agreement with Standard Model predictions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Measurement of the B s 0 → J / ψ η lifetime

Using a data set corresponding to an integrated luminosity of 3 fb –1 , collected by the LHCb experiment in pp collisions at centre-of-mass energies of 7 and 8 TeV, the effective lifetime in the B s 0 → J / ψ η decay mode, τ eff , is measured to be τ eff =1.479±0.034 (stat)±0.011 (syst) ps. Assuming CP conservation, τ eff corresponds to the lifetime of the light B$^{0}_{s}$ mass eigenstate. This is the first measurement of the effective lifetime in this decay mode.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Measurement of forward $W → eν$ production in $pp$ collisions at $\sqrt{s}=8$ TeV

A measurement of the cross-section for $W → eν$ production in $pp$ collisions is presented using data corresponding to an integrated luminosity of 2fb -1 collected by the LHCb experiment at a centre-of-mass energy of $\sqrt{s}=8$ TeV. The electrons are required to have more than 20 GeV of transverse momentum and to lie between 2.00 and 4.25 in pseudorapidity. The inclusive $W$ production cross-sections, where the $W$ decays to $eν$, are measured to be &#x03C3;<!-- σ --> W + &#x2192;<!-- → --> e + &#x03BD;<!-- ν --> e = 1124.4 &#x00B1;<!-- ± --> 2.1 &#x00B1;<!-- ± --> 21.5 &#x00B1;<!-- ± --> 11.2 &#x00B1;<!-- ± --> 13.0 p b , &#x03C3;<!-- σ --> W &#x2212;<!-- - --> &#x2192;<!-- → --> e &#x2212;<!-- - --> &#x03BD;<!-- ν --> &#x00AF;<!-- ¯ --> e = 809.0 &#x00B1;<!-- ± --> 1.9 &#x00B1;<!-- ± --> 18.1 &#x00B1;<!-- ± --> 7.0 &#x00B1;<!-- ± --> 9.4 p b , where the first uncertainties are statistical, the second are systematic, the third are due to the knowledge of the LHC beam energy and the fourth are due to the luminosity determination. Differential cross-sections as a function of the electron pseudorapidity are measured. The $W^+/W^-$ cross-section ratio and production charge asymmetry are also reported. Results are compared with theoretical predictions at next-to-next-to-leading order in perturbative quantum chromodynamics. Finally, in a precise test of lepton universality, the ratio of $W$ boson branching fractions is determined to be B ( W &#x2192;<!-- → --> e &#x03BD;<!-- ν --> ) / B ( W &#x2192;<!-- → --> &#x03BC;<!-- μ --> &#x03BD;<!-- ν --> ) = 1.020 &#x00B1;<!-- ± --> 0.002 &#x00B1;<!-- ± --> 0.019 , where the first uncertainty is statistical and the second is systematic.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Measurements of long-range near-side angular correlations in s N N = 5 TeV proton-lead collisions in the forward region

Two-particle angular correlations are studied in proton-lead collisions at a nucleon–nucleon centre-of-mass energy of s N N = 5 TeV , collected with the LHCb detector at the LHC. The analysis is based on data recorded in two beam configurations, in which either the direction of the proton or that of the lead ion is analysed. The correlations are measured in the laboratory system as a function of relative pseudorapidity, Δη, and relative azimuthal angle, Δφ, for events in different classes of event activity and for different bins of particle transverse momentum. In high-activity events a long-range correlation on the near side, Δφ≈0, is observed in the pseudorapidity range 2.0 < η < 4.9. This measurement of long-range correlations on the near side in proton-lead collisions extends previous observations into the forward region up to η=4.9. The correlation increases with growing event activity and is found to be more pronounced in the direction of the lead beam. However, the correlation in the direction of the lead and proton beams are found to be compatible when comparing events with similar absolute activity in the direction analysed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Amplitude analysis of B - → D + π - π - decays

The Dalitz plot analysis technique is used to study the resonant substructures of B - → D + π - π - decays in a data sample corresponding to 3.0 fb -1 of pp collision data recorded by the LHCb experiment during 2011 and 2012. A model-independent analysis of the angular moments demonstrates the presence of resonances with spins 1, 2 and 3 at high D + π - mass. The data are fitted with an amplitude model composed of a quasi-model-independent function to describe the D + π - S wave together with virtual contributions from the D*(2007) 0 and B* 0 states, and components corresponding to the D$*\atop{2}$(2460) 0 , D$*\atop{1}$(2680) 0 , D$*\atop{3}$(2760) 0 and D$*\atop{2}$(3000) 0 resonances. The masses and widths of these resonances are determined together with the branching fractions for their production in B- → D + π - π - decays. The D + π - S wave has phase motion consistent with that expected due to the presence of the D$*\atop{0}$(2400) 0 state. These results constitute the first observations of the D$*\atop{3}$(2760) 0 and D$*\atop{2}$(3000) 0 resonances, with significances of 10σ and 6.6σ, respectively.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Search for Structure in the B s 0 π ± Invariant Mass Spectrum

The B 0 s π ± invariant mass distribution is investigated in order to search for possible exotic meson states. The analysis is based on a data sample recorded with the LHCb detector corresponding to 3 fb –1 of pp collision data at √s = 7 and 8 TeV. No significant excess is found, and upper limits are set on the production rate of the claimed X(5568) state within the LHCb acceptance. Upper limits are also set as a function of the mass and width of a possible exotic meson decaying to the B 0 s π ± final state. The same limits also apply to a possible exotic meson decaying through the chain B* 0 s π ± , B* 0 s →B 0 s γ where the photon is excluded from the reconstructed decays.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗