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Stugu, B.

Publications and source records attributed to Stugu, B..

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Beam test results of 3D pixel detectors constructed with poly-crystalline CVD diamond

As a possible candidate for extremely radiation tolerant tracking devices we present a novel detector design - namely 3D detectors - based on poly-crystalline CVD diamond sensors with a pixel readout. The fabrication of recent 3D detectors as well their results in recent beam tests are presented. We measured the hit efficiency and signal response of two 3D diamond detectors with 50 × 50 μm cell sizes using pixel readout chip technologies currently used at CMS and ATLAS. In all runs, both devices attained efficiencies >98 % in a normal incident test beam of minimum ionising particles. The highest efficiency observed during the beam tests was 99.2 %.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Measurements of Cross Sections and Couplings of the Higgs Boson Using the ATLAS Detector

Measurements of cross sections and couplings of the Higgs boson using the ATLAS detector at CERN's LHC are presented. Data from proton proton collisions at $\sqrt{s}$ = 7, 8 and 13 TeV are discussed. A range of production and decay couplings can be tested with a precision that depends on the generality of the assumptions made. Data at 7 and 8 TeV are also combined with CMS results to enhance the precision. The results are all consistent with predictions of the Standard Model..

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Evidence for C P violation in B + → K * ( 892 ) + π 0 from a Dalitz plot analysis of B + → K S 0 π + π 0 decays

We report a Dalitz plot analysis of charmless hadronic decays of charged B mesons to the final state K 0 S π + π 0 using the full BABAR data set of 470.9 ± 2.8 million B¯B events collected at the Υ(4S) resonance. We measure the overall branching fraction and CP asymmetry to be B(B + → K 0 π + π 0 ) = (31.8 ± 1.8 ± 2.1 +6.0 –0.0 ) × 10 –6 and A CP (B + → K 0 π + π 0 ) = 0.07 ± 0.05 ± 0.03 +0.02 –0.03 , where the uncertainties are statistical, systematic, and due to the signal model, respectively. This is the first measurement of the branching fraction for B + → K 0 π + π 0 . We find first evidence of a CP asymmetry in B + → K*(892) + π 0 decays: A CP (B + → K*(892) + π 0 ) = –0.52 ± 0.14 ± 0.04 +0.04 –0.02 . The significance of this asymmetry, including systematic and model uncertainties, is 3.4 standard deviations. As a result, we also measure the branching fractions and CP asymmetries for three other intermediate decay modes.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Search for mixing-induced C P violation using partial reconstruction of B ¯ 0 → D * + X ℓ - ν ¯ ℓ and kaon tagging

We describe in detail a previously published measurement of CP violation in B 0 -B¯ 0 oscillations, based on an integrated luminosity of 425.7 fb -1 collected by the BABAR experiment at the PEPII collider. We apply a novel technique to a sample of about 6 million B¯ 0 →D* + ℓ - ν ℓ ¯ decays selected with partial reconstruction of the D*+ meson. The charged lepton identifies the flavor of one B meson at its decay time, the flavor of the other B is determined by kaon tagging. We determine a CP violating asymmetry ACP=(N(B0B0)-N(B¯ 0 B¯ 0 ))/(N(B 0 B 0 )+N(B¯ 0 B¯ 0 ))=(0.06±0.17 +0.38 -0.32 )% corresponding to Δ CP =1-|q/p|=(0.29±0.84 +1.88 -1.61 )×10 -3 . This measurement is consistent and competitive with those obtained at the B factories with dilepton events.

Experiment-HEP,HEPEX↗
DOE OSTI2016

Time-dependent analysis of B 0 → K S 0 π - π + γ decays and studies of the K + π - π + system in B + → K + π - π + γ decays

We measure the time-dependent CP asymmetry in the radiative-penguin decay B 0 → K S 0 π - π + γ , using a sample of 471×10 6 Υ(4S)→BB-events recorded with the BABAR detector at the PEP-II e+e- storage ring at SLAC. Using events with m Kππ < 1.8 GeV/c 2 , we measure the branching fractions of B+→K+π-π+γ and B0→K0π-π+γ, the branching fractions of the kaonic resonances decaying to K+π-π+, as well as the overall branching fractions of the B+→ρ0K+γ, B+→K*0π+γ and S-wave B+→(Kπ)0*0π+γ components. For events from the ρ mass band, we measure the CP-violating parameters SKS0π+π-γ=0.14±0.25±0.03 and CKS0π+π-γ=-0.39±0.20-0.02+0.03, where the first uncertainties are statistical and the second are systematic. We extract from this measurement the time-dependent CP asymmetry related to the CP eigenstate ρ0KS0 and obtain SKS0ργ=-0.18±0.32-0.05+0.06, which provides information on the photon polarization in the underlying b→sγ transition.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Observation of B ¯ → D ( * ) π + π - ℓ - ν ¯ Decays in e + e - Collisions at the Υ ( 4 S ) Resonance

We report on measurements of the decays of $\bar{B}$ mesons into the semileptonic final states $\bar{B}$→D(*)π + π - l - $\bar{v}$, where D(*) represents a D or D* meson and l - is an electron or a muon. These measurements are based on 471×10 6 B$\bar{B}$ pairs recorded with the BABAR detector at the SLAC asymmetric B factory PEP-II. We determine the branching fraction ratios R$(*)\atop{π+π-}$ = B($\bar{B}$→D(*)π + π - l - $\bar{v}$)/B($\bar{B}$→D(*)l - $\bar{v}$) using events in which the second B meson is fully reconstructed. We find R π+π- =0.067 ± 0.010 ± 0.008 and R$*\atop{π+π-}$ = 0.019 ± 0.005 ± 0.004, where the first uncertainty is statistical and the second is systematic. Lastly, based on these results and assuming isospin invariance, we estimate that $\bar{B}$→D(*)ππl - $\bar{v}$ decays, where π denotes either a π ± and π 0 meson, account for up to half the difference between the measured inclusive semileptonic branching fraction to charm hadrons and the corresponding sum of previously measured exclusive branching fractions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Collins asymmetries in inclusive charged K K and K π pairs produced in e + e - annihilation

Here, we present measurements of Collins asymmetries in the inclusive process e + e - →h 1 h 2 X, h 1 h 2 = KK, Kπ, ππ, at the center-of-mass energy of 10.6 GeV, using a data sample of 468 fb -1 collected by the BABAR experiment at the PEP-II B factory at SLAC National Accelerator Center. Considering hadrons in opposite thrust hemispheres of hadronic events, we observe clear azimuthal asymmetries in the ratio of unlike sign to like sign, and unlike sign to all charged h 1 h 2 pairs, which increase with hadron energies. The Kπ asymmetries are similar to those measured for the ππ pairs, whereas those measured for high-energy KK pairs are, in general, larger.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Measurement of initial-state–final-state radiation interference in the processes e + e – → μ + μ – γ and e + e – → π + π – γ [Measurement of ISR-FSR interference in the processes e + e – → μ + μ – γ and e + e – → π + π – γ ]

Charge asymmetry in the processes e + e – → μ + μ – γ and e + e – → π + π – γ is measured using 232 fb –1 of data collected with the BABAR detector at e + e – center-of-mass energies near 10.58 GeV. An observable is introduced and shown to be very robust against detector asymmetries while keeping a large sensitivity to the physical charge asymmetry that results from the interference between initial- and final-state radiation (FSR). The asymmetry is determined as a function of the invariant mass of the final-state tracks from production threshold to a few GeV/c 2 . It is compared to the expectation from QED for e + e – → μ + μ – γ, and from theoretical models for e + e – → π + π – γ. A clear interference pattern is observed in e + e – → π + π – γ, particularly in the vicinity of the f 2 (1270) resonance. As a result, the inferred rate of lowest-order FSR production is consistent with the QED expectation for e + e – → μ + μ – γ, and is negligibly small for e + e – → π + π – γ.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

Study of the e + e - → K + K - reaction in the energy range from 2.6 to 8.0 GeV

The e + e - →K + K - cross section and charged-kaon electromagnetic form factor are measured in the e + e - center-of-mass energy range (E) from 2.6 to 8.0 GeV using the initial-state radiation technique with an undetected photon. The study is performed using 469 fb-1 of data collected with the BABAR detector at the PEP-II2 e + e - collider at center-of-mass energies near 10.6 GeV. The form factor is found to decrease with energy faster than 1/E 2 and approaches the asymptotic QCD prediction. Production of the K + K - final state through the J/ψ and ψ(2S) intermediate states is observed. The results for the kaon form factor are used together with data from other experiments to perform a model-independent determination of the relative phases between electromagnetic (single-photon) and strong amplitudes in J/ψ and ψ(2S)→K + K - decays. The values of the branching fractions measured in the reaction e + e - →K + K - are shifted relative to their true values due to interference between resonant and nonresonant amplitudes. The values of these shifts are determined to be about ±5% for the J/ψ meson and ±15% for the ψ(2S) meson.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Search for Long-Lived Particles in e + e - Collisions

We present a search for a neutral, long-lived particle L that is produced in e + e - collisions and decays at a significant distance from the e + e - interaction point into various flavor combinations of two oppositely charged tracks. The analysis uses an e + e - data sample with a luminosity of 489.1 fb -1 collected by the BABAR detector at the γ (4S), γ (3S), and γ (2S) resonances and just below the γ (4S). Fitting the two-track mass distribution in search of a signal peak, we do not observe a significant signal, and set 90% confidence level upper limits on the product of the L production cross section, branching fraction, and reconstruction efficiency for six possible two-body L decay modes as a function of the L mass. The efficiency is given for each final state as a function of the mass, lifetime, and transverse momentum of the candidate, allowing application of the upper limits to any production model. In addition, upper limits are provided on the branching fraction B(B→X s L), where X s is a strange hadronic system.

Lees, J. P.↗