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Gradl, W.

Publications and source records attributed to Gradl, W..

At least 361 records · Page 20
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DOE OSTI2017

Measurement of the ω → π 0 e + e - and η → e + e - γ Dalitz decays with the A2 setup at the Mainz Microtron

The Dalitz decays η → e + e - γ and ω → π 0 e + e - have been measured in the γp → ηp and γp → ωp reactions, respectively, with the A2 tagged-photon facility at the Mainz Microtron. The value obtained for the slope parameter of the electromagnetic transition form factor of η, Λ$-2\atop{η}$ = (1.97 ± 0.11 tot ) GeV -2 , is in good agreement with previous measurements of the η → e + e - γ and η → μ + μ - γ decays. The uncertainty obtained in the value of Λ$-2\atop{η}$ is lower than in previous results based on the η → e + e - γ decay. The value obtained for the ω slope parameter, Λ$-2\atop{ωπ^0}$ = (1.99 ± 0.21 tot ) GeV -2 , is somewhat lower than previous measurements based on ω → π 0 μ + μ - , but the results for the ω transition form factor are in better agreement with theoretical calculations, compared to earlier experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Cross sections for the reactions e + e - → K S 0 K L 0 π 0 , K S 0 K L 0 η , and K S 0 K L 0 π 0 π 0 from events with initial-state radiation

Here, we study the processes e + e - → K$0\atop{S}$ K$0\atop{L}$ π 0 γ , K $0\atop{S}$ K$0\atop{L}$ η γ , and K$0\atop{S}$ K$0\atop{L}$ π 0 π 0 γ , where the photon is radiated from the initial state, providing cross section measurements for the hadronic final states over a continuum of center-of-mass energies. The results are based on 469 fb -1 of data collected at or near the Υ ( 4 S ) resonance with the BABAR detector at SLAC. We present the first measurements of the e + e - → K$0\atop{S}$ K$0\atop{L}$ π 0 , K$0\atop{S}$ K$0\atop{L}$ η , and K$0\atop{S}$ K$0\atop{L}$ π 0 π 0 cross sections up to a center-of-mass energy of 4 GeV and study their intermediate resonance structures. We observe J / ψ decays to all of these final states for the first time, present measurements of their J / ψ branching fractions, and search for ψ (2S) decays.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Precise Measurement of the e + e - → π + π - J / ψ Cross Section at Center-of-Mass Energies from 3.77 to 4.60 GeV

The statistical significance of this resonance is estimated to be larger than 7.6 σ . The mass and width of the second resonance agree with the Y(4360) resonance reported by the BABAR and Belle experiments within errors. Finally, the Y ( 4008 ) resonance previously observed by the Belle experiment is not confirmed in the description of the BESIII data.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Evidence of Two Resonant Structures in e + e - → π + π - h c

The cross sections of e + e - →π + π - h c at center-of-mass energies from 3.896 to 4.600 GeV are measured using data samples collected with the BESIII detector operating at the Beijing Electron Positron Collider. The cross sections are found to be of the same order of magnitude as those of e + e - →π + π - J/ψ and e + e - →π + π - ψ (2S), but the line shape is inconsistent with the Y states observed in the latter two modes. Two structures are observed in the e + e - → π + π - h c cross sections around 4.22 and 4.39 GeV / c 2 , which we call Y ( 4220 ) and Y ( 4390 ) , respectively. A fit with a coherent sum of two Breit-Wigner functions results in a mass of (4218.4 $+5.5\atop{-4.5 ± 0.9) MeV/c 2 and a width of 66.0$+12.3\atop-8.3$±0.4 MeV for the Y (4220), and a mass of (4391.5 $+6.3\atop-16.8$ ± 1.0) MeV/c 2 and a width of (139.5$+16.2\atop-20.6 ± 0.6) MeV for the Y (4390), where the first uncertainties are statistical and the second ones systematic. The statistical significance of Y ( 4220 ) and Y(4390) is 10σ over one structure assumption.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Measurement of the π 0 → e + e - γ Dalitz decay at the Mainz Microtron

The Dalitz decay π 0 → e + e - γ has been measured in the γp → π 0 p reaction with the A2 tagged-photon facility at the Mainz Microtron, MAMI. The value obtained for the slope parameter of the π 0 electromagnetic transition form factor, a π = 0.030 ± 0.010 tot , is in agreement with existing measurements of this decay and with recent theoretical calculations. The uncertainty obtained in the value of a π is lower than in previous results based on the π 0 → e + e - γ decay.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Luminosity measurements for the R scan experiment at BESIII

By analyzing the large-angle Bhabha scattering events e + e - → (γ)e + e - and diphoton events e + e - → (γ)γγ for the data sets collected at center-of-mass (c.m.) energies between 2.2324 and 4.5900 GeV (131 energy points in total) with the upgraded Beijing Spectrometer (BESIII) at the Beijing Electron-Positron Collider (BEPCII), the integrated luminosities have been measured at the different c.m. energies, individually. Finally, the results are important inputs for the R value and J/ψ resonance parameter measurements.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Search for B + → K + τ + τ - at the BaBar Experiment

We search for the rare flavor-changing neutral current process B + → K + τ + τ - using data from the BABAR experiment. The data sample, collected at the center-of-mass energy of the Υ ( 4 S ) resonance, corresponds to a total integrated luminosity of 424 fb - 1 and to 471 × 1 0 6 B$\bar{B}$ pairs. We reconstruct one B meson, produced in the Υ ( 4 S ) → B + B - decay, in one of many hadronic decay modes and search for activity compatible with a B + → K + τ + τ - decay in the rest of the event. Each τ lepton is required to decay leptonically into an electron or muon and neutrinos. Comparing the expected number of background events with the data sample after applying the selection criteria, we do not find evidence for a signal. The resulting upper limit, at the 90% confidence level, is B ( B + → K + τ + τ - ) < 2.25 × 10 - 3 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Amplitude Analysis of the Decays η ' → π + π - π 0 and η ' → π 0 π 0 π 0

Based on a sample of 1.31 × 10 9 J / ψ events collected with the BESIII detector, an amplitude analysis of the isospin-violating decays η'→ π + π - π 0 and η' → π 0 π 0 π 0 is performed. A significant P-wave contribution from η'→ ρ ± π ∓ is observed for the first time in η' → π + π - π 0 . The branching fraction is determined to be B ( η'→ ρ ± π ∓ ) = ( 7.44 ± 0.60 ± 1.26 ± 1.84 ) × 10 -4 , where the first uncertainty is statistical, the second systematic, and the third model dependent. In addition to the nonresonant S -wave component, there is a significant σ meson component. The branching fractions of the combined S -wave components are determined to be B ( η' → π + π - π 0 ) S = ( 37.63 ± 0.77 ± 2.22 ± 4.48 ) × 10 -4 and B ( η' → π 0 π 0 π 0 ) = ( 35.22 ± 0.82 ± 2.54 ) × 10 -4 , respectively. Finally, the latter one is consistent with previous BESIII measurements.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Determination of the scalar polarizabilities of the proton using beam asymmetry $\Sigma_{3}$ in Compton scattering

The scalar dipole polarizabilities, α E1 and β M1 , are fundamental properties related to the internal dynamics of the nucleon. The currently accepted values of the proton polarizabilities were determined by fitting to unpolarized proton Compton scattering cross section data. The measurement of the beam asymmetry Σ 3 in a certain kinematical range provides an alternative approach to the extraction of the scalar polarizabilities. At the Mainz Microtron (MAMI) the beam asymmetry was measured for Compton scattering below pion photoproduction threshold for the first time. Finally, the results are compared with model calculations and the influence of the experimental data on the extraction of the scalar polarizabilities is determined.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Photon asymmetry measurements of $\overrightarrow{\gamma}p \rightarrow \pi^{0} p$ γ → p → π 0 p for $E_{\gamma}=$ 320-650 MeV

High-statistics measurements of the photon asymmetry Σ for the $\overrightarrow{\gamma}p \rightarrow \pi^{0} p$ reaction have been made in the center-of-mass energy range W = 1214–1450 MeV. The data were measured with the MAMI A2 real photon beam and Crystal Ball/TAPS detector systems in Mainz, Germany. The resulting measurements significantly improve the existing world data and are shown to be in good agreement with previous measurements, and with the MAID, SAID, and Bonn-Gatchina predictions. We have also combined the photon asymmetry results with recent cross-section measurements from Mainz to calculate the profile functions, $\check{Σ}$ (= σ 0 Σ), and perform a moment analysis. Comparison with calculations from the Bonn-Gatchina model shows that the precision of the data is good enough to further constrain the higher partial waves, and there is an indication of interference between the very small F-waves and the N(1520)3/2 - and N(1535)1/2 - resonances.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Measurement of the B 0 → D * - π + π - π + branching fraction

When using a sample of ( 470.9 ± 2.8 ) × 10 6 B$\bar{B}$ pairs, we measure the decay branching fraction B ( B 0 → D * - π + π - π + ) = ( 7.26 ± 0.11 ± 0.31 ) × 10 -3 , where the first uncertainty is statistical and the second is systematic. These measurement will be helpful in studies of lepton universality by measuring B ( B 0 → D * - τ + ν τ ) using τ + → π + π - π + ¯ ν τ decays, normalized to B ( B 0 → D * - π + π - π + ) .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Measurement of the absolute branching fraction of D + → $\bar{K}$ 0 e + ν e via $\bar{K}$ 0 → π 0 π 0

By analyzing 2.93 fb–1 data collected at the center-of-mass energy with the BESIII detector, we measure the absolute branching fraction of the semileptonic decay D+ → $\bar{K}$0 e+νe to be Β(D + → $\bar{K}$ 0 e + ν e ) = (8.59 ± 0.14 ± 0.21)% using $\bar{K}$ 0 → K 0 s → π 0 π 0 , where the first uncertainty is statistical and the second systematic. Finally, our result is consistent with previous measurements within uncertainties..

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗