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Pedlar, T. K.

Publications and source records attributed to Pedlar, T. K..

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Azimuthal asymmetries of back-to-back π ± - ( π 0 , η , π ± ) pairs in e + e - annihilation

This work reports the first observation of azimuthal asymmetries around the thrust axis in e + e – annihilation of pairs of back-to-back charged pions in one hemisphere, and π 0 and η mesons in the opposite hemisphere. These results are complemented by a new analysis of pairs of back-to-back charged pions. The π 0 and η asymmetries rise with the relative momentum z of the detected hadrons as well as with the transverse momentum with respect to the thrust axis. These asymmetries are sensitive to the Collins fragmentation function $H$ $^{1}_{⊥}$ and provide complementary information to previous measurements with charged pions and kaons in the final state. In particular, the η final states will provide additional information on the flavor structure of $H$ $^{1}_{⊥}$. This is the first measurement of the explicit transverse-momentum dependence of the Collins fragmentation function from Belle data. It uses a dataset of 980.4 fb –1 collected by the Belle experiment at or near a center- of-mass energy of 10.58 GeV.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2017

Measurement of the decays B → η ℓ ν ℓ and B → η ' ℓ ν ℓ in fully reconstructed events at Belle

We report branching fraction measurements of the decays B + → ηℓ + νℓ and B + → η'ℓ + νℓ based on 711 fb –1 of data collected near the Υ(4S) resonance with the Belle experiment at the KEKB asymmetric-energy e + e – collider. This data sample contains 772 million BB¯ events. One of the two B mesons is fully reconstructed in a hadronic decay mode. Among the remaining (“signal-B”) daughters, we search for the η meson in two decay channels, η → γγ and η → π + π – π 0 , and reconstruct the η' meson in η' → ηπ + π – with subsequent decay of the η into γγ. Combining the two η modes and using an extended maximum likelihood, the B + → ηℓ + νℓ branching fraction is measured to be (4.2 ± 1.1(stat.) ± 0.3(syst.)) × 10 –5 . For B + → η'ℓ + νℓ, we observe no significant signal and set an upper limit of 0.72 × 10 –4 at 90% confidence level.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

First Observation of the Hadronic Transition Υ ( 4 S ) → η h b ( 1 P ) and New Measurement of the h b ( 1 P ) and η b ( 1 S ) Parameters

Using a sample of 771.6 × 10 6 Υ Υ ( 4 S ) decays collected by the Belle experiment at the KEKB e + e - collider, we observe, for the first time, the transition Υ ( 4 S ) → η h b ( 1 P ) with the branching fraction B [ Υ ( 4 S ) → η h b ( 1 P ) ] = ( 2.18 ± 0.11 ± 0.18 ) × 10 - 3 and we measure the h b ( 1 P ) mass M h b ( 1 P ) = ( 9899.3 ± 0.4 ± 1.0 ) MeV / c 2 , corresponding to the hyperfine (HF) splitting Δ M HF ( 1 P ) = ( 0.6 ± 0.4 ± 1.0 ) MeV / c 2 . Using the transition h b ( 1 P ) → γ η b ( 1 S ) , we measure the η b ( 1 S ) mass M η b ( 1 S ) = ( 9400.7 ± 1.7 ± 1.6 ) MeV / c 2 , corresponding to Δ M HF ( 1 S ) = ( 59.6 ± 1.7 ± 1.6 ) MeV / c 2 , the η b ( 1 S ) width Γ η b ( 1 S ) = ( 8 - 5 + 6 ± 5 ) MeV / c 2 and the branching fraction B [ h b ( 1 P ) → γ η b ( 1 S ) ] = ( 56 ± 8 ± 4 ) % .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Measurement of e + e – → γ χ c J via initial state radiation at Belle

The process e + e – → γχ cJ (J = 1, 2) is studied via initial state radiation using 980 fb –1 of data at and around the Υ(nS) (n = 1, 2, 3, 4, 5) resonances collected with the Belle detector at the KEKB asymmetric-energy e + e – collider. Here, no significant signal is observed except from ψ(2S) decays. Upper limits on the cross sections between √s = 3.80 and 5.56 GeV are determined at the 90% credibility level, which range from a few pb to a few tens of pb. We also set upper limits on the decay rate of the vector charmonium [ψ(4040), ψ(4160), and ψ(4415)] and charmoniumlike [Y(4260), Y(4360), and Y(4660)] states to γχ cJ .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Search for the Dark Photon and the Dark Higgs Boson at Belle

The dark photon A ' and the dark Higgs boson h ' are hypothetical constituents featured in a number of recently proposed dark sector models. Assuming prompt decays of both dark particles, we search for their production in the so-called Higgstrahlung channel e + e - → A ' h ' , with h ' → A ' A ' . We investigate ten exclusive final states with A ' → e + e - , μ + μ - , or π + π - in the mass ranges 0.1 GeV / c 2 < m A ' < 3.5 GeV / c 2 and 0.2 GeV / c 2 < m h ' < 10.5 GeV / c 2 . We also investigate three inclusive final states 2 ( e + e - ) X , 2 ( μ + μ - ) X , and ( e + e - ) ( μ + μ - ) X , where X denotes a dark photon candidate detected via missing mass, in the mass ranges 1.1 GeV / c 2 < m A ' < 3.5 GeV / c 2 and 2.2 GeV / c 2 < m h ' < 10.5 GeV / c 2 . Using the entire 977 fb - 1 data set collected by Belle, we determine no significant signal. Here, we obtain individual and combined 90% credibility level upper limits on the branching fraction times the Born cross section, B × σ Born , on the Born cross section σ Born , and on the dark photon coupling to the dark Higgs boson times the kinetic mixing between the standard model photon and the dark photon, α D × ε 2 . These limits improve upon and cover wider mass ranges than previous experiments. The limits from the final states 3 ( π + π - ) and 2 ( e + e - ) X are the first placed by any experiment. For α D equal to 1 / 137 , m h ' < 8 GeV / c 2 , and m A ' < 1 GeV / c 2 , we exclude values of the mixing parameter ε above ~ 8×10 -4 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Evidence of Υ ( 1 S ) → J / ψ + χ c 1 and search for double-charmonium production in Υ ( 1 S ) and Υ ( 2 S ) decays

Using data samples of 102 × 10 6 Υ ( 1 S ) and 158 × 10 6 Υ ( 2 S ) events collected with the Belle detector, a first experimental search has been made for double-charmonium production in the exclusive decays Υ ( 1 S , 2 S ) → J / ψ ( ψ ' ) + X , where X = η c , χ c J ( J = 0 , 1 , 2 ) , η c ( 2 S ) , X ( 3940 ) , and X ( 4160 ) . No significant signal is observed in the spectra of the mass recoiling against the reconstructed J / ψ or ψ ' except for the evidence of χ c 1 production with a significance of 4.6 σ for Υ ( 1 S ) → J / ψ + χ c 1 . The measured branching fraction B ( Υ ( 1 S ) → J / ψ + χ c 1 ) is [ 3.90 ± 1.21 ( stat ) ± 0.23 ( syst ) ] × 10 - 6 . The 90% C.L. upper limits on the branching fractions of the other modes having a significance of less than 3 σ are determined. In conclusion, these results are consistent with theoretical calculations using the nonrelativistic QCD factorization approach.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Observation of e + e – → π + π – π 0 χ b J and Search for X b → ω Y ( 1 S ) at s = 10.867 GeV

The e + e – → π + π – π 0 χ bJ (J = 0,1,2) processes are studied using a 118 fb –1 data sample acquired with the Belle detector at a center-of-mass energy of 10.867 GeV. Unambiguous π + π – π 0 χ bJ (J = 1,2), ωχ b1 signals are observed, and indication for ωχ b2 is seen, both for the first time, and the corresponding cross section measurements are presented. No significant π + π – π 0 χ b0 or ωχ b0 signals are observed, and 90% confidence level upper limits on the cross sections for these two processes are obtained. In the π + π – π 0 invariant mass spectrum, significant non-ω signals are also observed. In conclusion, we search for the X(3872)-like state (named X b ) decaying into ωΥ(1S); no significant signal is observed with a mass between 10.55 and 10.65 GeV/c 2 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Measurements of the masses and widths of the Σ c ( 2455 ) 0 / + + and Σ c ( 2520 ) 0 / + + baryons

Here, we highlight measurements of the masses and decay widths of the baryonic states Σ c ( 2455 ) 0 / + + and Σ c ( 2520 ) 0 / + + using a data sample corresponding to an integrated luminosity of 711 fb - 1 collected with the Belle detector at the KEKB e + e - asymmetric-energy collider operating at the Υ ( 4 S ) resonance. We report the mass differences with respect to the Λ c + baryon M ( Σ c ( 2455 ) 0 ) - M ( Λ c + ) = 167.29 ± 0.01 ± 0.02 MeV / c 2 , M ( Σ c ( 2455 ) + + ) - M ( Λ c + ) = 167.51 ± 0.01 ± 0.02 MeV / c 2 , M ( Σ c ( 2520 ) 0 ) - M ( Λ c + ) = 231.98 ± 0.11 ± 0.04 MeV / c 2 , M ( Σ c ( 2520 ) + + ) - M ( Λ c + ) = 231.99 ± 0.10 ± 0.02 MeV / c 2 , and the decay widths Γ ( Σ c ( 2455 ) 0 ) = 1.76 ± 0.0 4 - 0.21 + 0.09 MeV / c 2 , Γ ( Σ c ( 2455 ) + + ) = 1.84 ± 0.0 4 - 0.20 + 0.07 MeV / c 2 , Γ ( Σ c ( 2520 ) 0 ) = 15.41 ± 0.4 1 - 0.32 + 0.20 MeV / c 2 , Γ ( Σ c ( 2520 ) + + ) = 14.77 ± 0.2 5 - 0.30 + 0.18 MeV / c 2 , where the first uncertainties are statistical and the second are systematic. The isospin mass splittings are measured to be M ( Σ c ( 2455 ) + + ) - M ( Σ c ( 2455 ) 0 ) = 0.22 ± 0.01 ± 0.01 MeV / c 2 and M ( Σ c ( 2520 ) + + ) - M ( Σ c ( 2520 ) 0 ) = 0.01 ± 0.15 ± 0.03 MeV / c 2 . These results are the most precise to date.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Search for B 0 → p Λ ¯ π – γ at Belle

We search for the charmless B 0 decay with final state particles p¯Λπ – γ using the full data sample that contains 772 × 10 6 BB¯ pairs collected at the Υ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e + e – collider. Here, this decay is predicted to proceed predominantly via the b → sγ radiative penguin process with a high energy photon. No significant signal is found. As a result, we set an upper limit of 6.5 × 10 –7 for the branching fraction of B 0 → p¯Λπ – γ at the 90% confidence level.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Measurement of the τ -lepton Lifetime at Belle

We report that the lifetime of the τ lepton is measured using the process e + e - → τ + τ - , where both τ leptons decay to 3 π ν τ . The result for the mean lifetime, based on 711 fb - 1 of data collected with the Belle detector at the Y ( 4 S ) resonance and 60 MeV below, is τ = ( 290 . 17 ± 0.53 ( stat ) ± 0.33 ( syst ) ) × 10 - 15 s . The first measurement of the lifetime difference between τ + and τ - is performed. The upper limit on the relative lifetime difference between positive and negative τ leptons is | Δ τ | / τ < 7.0 × 10 - 3 at 90% C.L.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Angular analysis of B 0 → φ K * decays and search for C P violation at Belle

Here, we report the measurements of branching fractions and C P violation asymmetries in B 0 → φ K * decays obtained in an angular analysis using the full data sample of 772 × 10 6 B B ¯ pairs collected at the Υ ( 4 S ) resonance with the Belle detector at the KEKB asymmetric-energy e + e - collider. Furthermore, we perform a partial wave analysis to distinguish among scalar [ B 0 → φ ( K π ) 0 * ], vector [ B 0 → φ K * ( 892 ) 0 ] and tensor [ B 0 → φ K 2 * ( 1430 ) 0 ] components, and determine the corresponding branching fractions to be B [ B 0 → φ ( K π ) 0 * ] = ( 4.3 ± 0.4 ± 0.4 ) × 10 - 6 , B [ B 0 → φ K * ( 892 ) 0 ] = ( 10.4 ± 0.5 ± 0.6 ) × 10 - 6 and B [ B 0 → φ K 2 * ( 1430 ) 0 ] = ( 5.5 - 0.7 + 0.9 ± 1.0 ) × 10 - 6 . We also measure the longitudinal polarization fraction f L in B 0 → φ K * ( 892 ) 0 and B 0 → φ K 2 * ( 1430 ) 0 decays to be 0.499 ± 0.030 ± 0.018 and 0.918 - 0.060 + 0.029 ± 0.012 , respectively. The first quoted uncertainties are statistical and the second are systematic. In total, we measure 26 parameters related to branching fractions, polarization and C P violation in the B 0 → φ K * system. No evidence for C P violation is found.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Evidence for B ¯ s 0 → Λ c + Λ ¯ π -

Using 121.4 fb -1 of data collected with the Belle detector at the Υ(5S) resonance at the KEKB asymmetric-energy e + e - collider, we report evidence for the $\bar{B}$ 0 s → Λ$+\atop{c}$$\bar{Λ}$π - source decay mode with a measured branching fraction (3.6±1.1[stat] $+0.3\atop{-0.5}$± 0.9 [Λ$+\atop{c}$] ±0.7[N $\bar{B}$ 0 s ]) x 10 -4 and a significance of 4.4 standard deviations. This is the first evidence for a baryonic $\bar{B}$ 0 s decay.

43 PARTICLE ACCELERATORS↗