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Schubert, K. R.

Publications and source records attributed to Schubert, K. R..

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Measurement of the e + e - → π + π - π 0 π 0 cross section using initial-state radiation at BABAR

Here, the process e + e – →π + π – 2π 0 γ is investigated by means of the initial-state radiation technique, where a photon is emitted from the incoming electron or positron. Using 454.3 fb –1 of data collected around a center-of-mass energy of √s=10.58 GeV by the BABAR experiment at SLAC, approximately 150000 signal events are obtained. The corresponding nonradiative cross section is measured with a relative uncertainty of 3.6% in the energy region around 1.5 GeV, surpassing all existing measurements in precision. Using this new result, the channel’s contribution to the leading order hadronic vacuum polarization contribution to the anomalous magnetic moment of the muon is calculated as (gπ + π – 2π 0 μ –2)/2=(17.9 ± 0.1 stat ± 0.6 syst )×10–10 in the energy range 0.85 GeV < E CM < 1.8 GeV. In the same energy range, the impact on the running of the fine-structure constant at the Z 0 -pole is determined as Δαπ + π – 2π 0 (M 2 Z )=(4.44 ± 0.02 stat ± 0.14 syst ) × 10 –4 . Furthermore, intermediate resonances are studied and especially the cross section of the process e + e – →ωπ 0 →π + π – 2π 0 is measured.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Measurement of the D * ( 2010 ) + - D + Mass Difference

Here, we measure the mass difference, Δm + , between the D* (2010) + and the D + using the decay chain D* (2010) + → D + π 0 with D + → K - π + π + . The data were recorded with the BABAR detector at center-of-mass energies at and near the Υ(4S) resonance, and correspond to an integrated luminosity of approximately 468 fb -1 . We measure Δm + = (140 601.0 ± 6.8 [stat] ± 12.9 [syst] ) keV . We combine this result with a previous BABAR measurement of Δm 0 ≡ m(D* (2010) + ) - m (D 0 ) to obtain Δm D = m (D + ) - m (D 0 ) = ( 4824.9 ± 6.8 [stat] ± 12.9 [syst]) keV . These results are compatible with and approximately five times more precise than the Particle Data Group averages.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Measurement of the inclusive electron spectrum from B meson decays and determination of | V u b |

Based on the full BABAR data sample of 466.5 million $B\bar{B}$ pairs, we present measurements of the electron spectrum from semileptonic B meson decays. We fit the inclusive electron spectrum to distinguish Cabibbo-Kobayashi-Maskawa (CKM) suppressed B → X u eν decays from the CKM-favored B → X c eν decays, and from various other backgrounds, and determine the total semileptonic branching fraction B (B → Xeν) = ( 10.34 ± 0.04 stat ± 0.2 6 syst )%, averaged over B ± and B 0 mesons. We determine the spectrum and branching fraction for charmless B → X u eν decays and extract the CKM element | V ub | , by relying on four different QCD calculations based on the heavy quark expansion. While experimentally, the electron momentum region above 2.1 GeV / c is favored, because the background is relatively low, the uncertainties for the theoretical predictions are largest in the region near the kinematic endpoint. Detailed studies to assess the impact of these four predictions on the measurements of the electron spectrum, the branching fraction, and the extraction of the CKM matrix element |V ub | are presented, with the lower limit on the electron momentum varied from 0.8 GeV / c to the kinematic endpoint. We determine |V ub | using each of these different calculations and find, |V ub | = ( 3.794 ± 0.107 exp $+ 0.292\atop{ - 0.219 SF}$ $+ 0.078 \atop{- 0.068 theory}$ ) × 10 - 3 (De Fazio and Neubert), (4.563 ± 0.126 exp $+ 0.230\atop {- 0.208 SF}$ $+ 0.162\atop{- 0.163 theory}$ ) ×10 -3 (Bosch, Lange, Neubert, and Paz), (3.959 ± 0.104 exp $+ 0.164\atop{- 0.154 SF}$ $+ 0.042\atop{ - 0.079 theory}$ ) × 10 -3 (Gambino, Giordano, Ossola, and Uraltsev), (3.848 ± 0.108 exp $+ 0.084\atop{ - 0.070 theory}$) × 10 -3 (dressed gluon exponentiation), where the stated uncertainties refer to the experimental uncertainties of the partial branching fraction measurement, the shape function parameters, and the theoretical calculations.

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

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 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

Search for a muonic dark force at BaBar

Many models of physics beyond the standard model predict the existence of new Abelian forces with new gauge bosons mediating interactions between "dark sectors" and the standard model. We report a search for a dark boson Z' coupling only to the second and third generations of leptons in the reaction e+e-→μ+μ-Z',Z'→μ+μ- using 514 fb -1 of data collected by the BABAR experiment. No significant signal is observed for Z' masses in the range 0.212-10 GeV. Lastly, limits on the coupling parameter g' as low as 7×10 -4 are derived, leading to improvements in the bounds compared to those previously derived from neutrino experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Tests of C P T symmetry in B 0 - B ¯ 0 mixing and in B 0 → c c ¯ K 0 decays

Here, using the eight time dependences e- Γt (1 + C i cos Δmt + S i sin Δmt) for the decays Y(4S)→B 0 $\bar{B}$ 0 →f j f k , with the decay into a flavor-specific state f j = ± X before or after the decay into a CP eigenstate f k =c$\bar{c}$ K S,L , as measured by the BABAR experiment, we determine the three CPT-sensitive parameters Re(z) and Im(z) in B 0 $\bar{B}$ 0 mixing and |$\bar{A}$/A| in B 0 →c$\bar{c}$ K 0 decays. We find Im(z) = 0.010 ± 0.030 ± 0.013, Re(z) = -0.065 ± 0.028 ± 0.014, and |$\bar{A}$/A|=0.999±0.023±0.01, in agreement with CPT symmetry.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Measurement of the neutral D meson mixing parameters in a time-dependent amplitude analysis of the D 0 → π + π - π 0 decay

Here we perform the first measurement on the D 0 -D 0 mixing parameters using a time-dependent amplitude analysis of the decay D 0 →π + π - π 0 . The data were recorded with the BABAR detector at center-of-mass energies at and near the $Y$(4S) resonance, and correspond to an integrated luminosity of approximately 468.1 fb -1 . The neutral D meson candidates are selected from D*(2010) + →D 0 π$+\atop{s}$ decays where the flavor at the production is identified by the charge of the low-momentum pion, π$+\atop{s}$. The measured mixing parameters are x=(1.5±1.2±0.6)% and y=(0.2±0.9±0.5)%, where the quoted uncertainties are statistical and systematic, respectively.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Measurement of the I = 1 / 2 K π S -wave amplitude from Dalitz plot analyses of η c → K K ¯ π in two-photon interactions

Here we study the processes γγ→K$0\atop{S}$K ± π ∓ and γγ→K + K - π 0 using a data sample of 519 fb -1 recorded with the BABAR detector operating at the SLAC PEP-II asymmetric-energy e + e - collider at center-of-mass energies at and near the Υ(nS) (n=2, 3, 4) resonances. We observe ηc decays to both final states and perform Dalitz plot analyses using a model-independent partial wave analysis technique. This allows a model-independent measurement of the mass-dependence of the I=1/2 Kπ S-wave amplitude and phase. A comparison between the present measurement and those from previous experiments indicates similar behavior for the phase up to a mass of 1.5 GeV/c 2 . In contrast, the amplitudes show very marked differences. Lastly, the data require the presence of a new a 0 (1950) resonance with parameters m=1931±14±22 MeV/c 2 and Γ=271±22±29 MeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Search for C P Violation in B 0 - B ¯ 0 Mixing Using Partial Reconstruction of B 0 → D * - X ℓ + ν ℓ and a Kaon Tag

We present results of a search for CP violation in B 0 -B¯ 0 mixing with the BABAR detector. We select a sample of B 0 →D* - Xℓ+ν decays with a partial reconstruction method and use kaon tagging to assess the flavor of the other B meson in the event. We determine the CP violating asymmetry ACP≡[N(B 0 B 0 )-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 ΔCP=1-|q/p|=(0.29±0.84 +1.88 -1.61 )×10 -3 .

43 PARTICLE ACCELERATORS↗