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Chang, P.

Publications and source records attributed to Chang, P..

At least 109 records · Page 6
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DOE OSTI2014

The Physics of the B Factories

This work is on the Physics of the B Factories. Part A of this book contains a brief description of the SLAC and KEK B Factories as well as their detectors, BaBar and Belle, and data taking related issues. Part B discusses tools and methods used by the experiments in order to obtain results. The results themselves can be found in Part C. Please note that version 3 on the archive is the auxiliary version of the Physics of the B Factories book. This uses the notation alpha, beta, gamma for the angles of the Unitarity Triangle. The nominal version uses the notation phi_1, phi_2 and phi_3. Please cite this work as Eur. Phys. J. C74 (2014) 3026.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Observation of the decay B 0 → η ' K * ( 892 ) 0

In this paper, we report a search for charmless hadronic decays of neutral B mesons to η ' K * ( 892 ) 0 . The results are based on a 711 fb - 1 data sample that contains 772 × 10 6 B B ¯ pairs, collected at the Y ( 4 S ) resonance with the Belle detector at the KEKB asymmetric energy e + e - collider. We observe the decay for the first time with a significance of 5.0 standard deviations and obtain its branching fraction B [ B 0 → η ' K * ( 892 ) 0 ] = [ 2.6 ± 0.7 ( stat ) ± 0.2 ( syst ) ] × 10 - 6 . We also measure the C P -violating asymmetry as A C P [ B 0 → η ' K * ( 892 ) 0 ] = - 0.22 ± 0.29 ( stat ) ± 0.07 ( syst ) .

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

Temperature dependent Raman scattering and far-infrared reflectance spectra of MgO modified Pb{sub 0.99}(Zr{sub 0.95}Ti{sub 0.05}){sub 0.98}Nb{sub 0.02}O{sub 3} ceramics: A composition effect

Lattice dynamics and phase transition of MgO modified Pb{sub 0.99}(Zr{sub 0.95}Ti{sub 0.05}){sub 0.98}Nb{sub 0.02}O{sub 3} (PZTN-x wt. % MgO, x = 0, 0.1, 0.2, 0.5) ceramics have been investigated by far-infrared (FIR) reflectance in the temperature range of 5.5–300 K and Raman spectra between 77 and 300 K, respectively. With the aid of above complementary methods, the structure of all ceramics was defined as low-temperature ferroelectric rhombohedral phase [F{sub R(LT)}] at room temperature. The FIR dielectric functions were extracted from the multi-Lorentz oscillator dispersion model. The lowest frequency phonon mode, which is related to Pb-BO{sub 3} (B = Zr, Ti, Nb) vibration, mainly dominates the FIR dielectric response. With increasing MgO composition, the dielectric constants ε(0) at room temperature are estimated to 85.4, 73.4, 73.9, and 41.9, respectively. The decreasing trend can be due to the doubly ionized oxygen vacancies induced by Mg substitution for B-site. The order-disorder phase transition located around 120 K can be clearly clarified from temperature evolution of phonon frequency, damping, and intensity. It decreases slightly with increasing MgO composition, which influence the distortion due to the broken correlation chains and local permanent dipoles creation. Moreover, the transformation from antiferroelectric orthorhombic A{sub O} to [ F{sub R(LT)} ] phase has been observed around 250 K, which is associated with the antiferroelectric displacement of Pb atoms along 〈 110 〉 and coupled rotations of the corner-connected oxygen octahedral. Furthermore, the transition from [ F{sub R(LT)} ] to [ F{sub R(HT)} ] (high-temperature ferroelectric rhombohedral phase) was identified around 290 K for MgO-doped PZTN ceramics. It arises from the shift of cation (Pb and Zr/Ti/Nb/Mg ions) along the 〈 111 〉 direction and the transition temperature slightly decreases compared to the pure ceramic.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Spin-phonon interactions of multiferroic Bi{sub 4}Ti{sub 3}O{sub 12}-BiFeO{sub 3} ceramics: Low-temperature Raman scattering and infrared reflectance spectra investigations

Optical phonons of multiferroic Bi{sub 4}Ti{sub 3}O{sub 12}-BiFeO{sub 3} ceramic have been investigated by low temperature Raman scattering and infrared reflectance spectra. Anomalies at about 85 K can be observed from the temperature dependence of the Raman and infrared modes, which arise from spin-phonon interaction during antiferromagnetic to paramagnetic phase transition. It was found that the change of exchange interaction in magnetic phase transition can be induced by Fe-O-Fe octahedral tilting driven from the A-site atoms. Moreover, ferroelectricity-related displacement of Bismuth atoms suggests the coupling of magnetic and ferroelectric orders.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
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

Evidence for semileptonic B - → p p ¯ ℓ - ν ¯ ℓ decays

Evidence for the semileptonic baryonic decay B - → p p ¯ ℓ - ν ¯ ℓ ( ℓ = e , μ ), based on a data sample of 772 million B B ¯ pairs collected at the Υ ( 4 S ) resonance with the Belle detector at the KEKB asymmetric-energy electron-positron collider is collected. A neural-network based hadronic B -meson tagging method is used in this study. The branching fraction of B - → p p ¯ ℓ - ν ¯ ℓ is measured to be ( 5. 8 - 2.1 + 2.4 (stat) ± 0.9 (syst) ) × 10 - 6 with a significance of 3.2 σ , where lepton universality is assumed. We also estimate the corresponding upper limit: B ( B - → p p ¯ ℓ - ν ¯ ℓ ) < 9.6 × 10 - 6 at the 90% confidence level. This measurement helps constrain the baryonic transition form factor in B decays.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Evidence for the suppressed decay B – → D K – , D → K + π – π 0

We report a study of the suppressed decay B – → DK – , D → K + π – π 0 , where D denotes either a D 0 or a D 0 ¯ meson. The decay is sensitive to the CP-violating parameter Φ 3 . Using a data sample of 772 × 10 6 BB¯ pairs collected at the Υ(4S) resonance with the Belle detector, we measure the ratio of branching fractions of the above suppressed decay to the favored decay B – → DK – , D → K – π + π 0 . Our result is R DK = [1.98 ± 0.62(stat) ± 0.24(syst)] × 10 –2 , which indicates the first evidence of the signal for this suppressed decay with a significance of 3.2 standard deviations. We measure the direct CP asymmetry between the suppressed B – and B + decays to be A DK = 0.41 ± 0.30(stat) ± 0.05(syst). We also report measurements for the analogous quantities R Dπ and A Dπ for the decay B – → Dπ – , D → K + π – π 0 .

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

Measurements of branching fractions of leptonic and hadronic $ D_s^{+} $ meson decays and extraction of the $ D_s^{+} $ meson decay constant

We present measurements of absolute branching fractions of hadronic and lep-tonic \( D_s^{+} \) decays to K - K + π + , \( {{\overline{K}}^0} \) K + , ηπ + , μ + ν μ and τ + ν τ and report a search for the leptonic \( D_s^{+} \) → e + ν e decays. The results are obtained from a data sample of 913 fb -1 collected at or near the \( \varUpsilon \) (4 S ) and \( \varUpsilon \) (5 S ) resonances with the Belle detector at the KEKB asymmetric-energy e + e - collider. The branching fractions of hadronic decays are measured to be $$ \begin{array}{*{20}{c}} {\mathcal{B}\left( {D_s^{+}\ \to\ {K^{-}}{K^{+}}{\pi^{+}}} \right) = \left( {5.06\pm 0.15\pm 0.21} \right)\%,} \\ {\mathcal{B}\left( {D_s^{+}\ \to\ {{\overline{K}}^0}{K^{+}}} \right) = \left( {2.95\pm 0.11\pm 0.09} \right)\%,} \\ {\mathcal{B}\left( {D_s^{+}\ \to\ \eta {\pi^{+}}} \right) = \left( {1.82\pm 0.14\pm 0.07} \right)\%,} \\ \end{array} $$ where the first and second uncertainties are statistical and systematic, respectively. The branching fractions of leptonic decays are measured to be $$ \begin{array}{*{20}{c}} {\mathcal{B}\left( {D_s^{+}\ \to\ {\mu^{+}}{\nu_{\mu }}} \right)=\left( {0.531\pm 0.028\pm 0.020} \right)\%,} \\ {\mathcal{B}\left( {D_s^{+}\to {\tau^{+}}{\nu_{\tau }}} \right)=\left( {5.70\pm 0.21_{-0.30}^{-0.31 }} \right)\%,} \\ \end{array} $$ which are combined to determine the \( D_s^{+} \) meson decay constant $$ {f_{{{D_s}}}}=\left( {255.5\pm 4.2\pm 5.1} \right)\ \mathrm{MeV}. $$ We find no significant signal for \( D_s^{+} \) → e + ν e decays and set an upper limit of \( \mathcal{B}\left( {D_s^{+}\ \to\ {e^{+}}{\nu_e}} \right) \) < 1 . 0(0 . 83) × 10 -4 at 95% (90%) confidence level.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

First observation of the Z b 0 ( 10610 ) in a Dalitz analysis of Υ ( 10860 ) → Υ ( n S ) π 0 π 0

Here, we report the first observation of Υ ( 10860 ) → Υ ( 1 , 2 , 3 S ) π 0 π 0 decays. The neutral partner of the Z b ± ( 10610 ) , the Z b 0 ( 10610 ) decaying to Υ ( 2 , 3 S ) π 0 , is observed for the first time with a 6.5 σ significance using a Dalitz analysis of Υ ( 10860 ) → Υ ( 2 , 3 S ) π 0 π 0 decays. The findings are obtained with a 121.4 fb - 1 data sample collected with the Belle detector at the Υ ( 10860 ) resonance at the KEKB asymmetric-energy e + e - collider.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Search for B → h ( * ) ν ν ¯ with the full Belle Υ ( 4 S ) data sample

This report is of a search for the rare decays B → h ( * ) ν ν ¯ , where h ( * ) stands for K + , K S 0 , K * + , K * 0 , π + , π 0 , ρ + , ρ 0 and Φ . The results are obtained from a 711 fb - 1 data sample that contains 772 × 10 6 B B ¯ pairs collected at the Υ ( 4 S ) resonance with the Belle detector at the KEKB e + e - collider. We search for signal candidates by fully reconstructing a hadronic decay of the accompanying B meson and requiring a single h ( * ) meson left on the signal side. No significant signal is observed and we set upper limits on the branching fractions at 90% confidence level. The measurements of B + → K * + ν ν ¯ , B + → π + ν ν ¯ , B 0 → π 0 ν ν ¯ and B 0 → ρ 0 ν ν ¯ provide the world’s currently most restrictive limits.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Study of e + e - → π + π - J / ψ and Observation of a Charged Charmoniumlike State at Belle

The cross section for $e^+e^-→π^+π^-J/ψ$ between 3.8 GeV and 5.5 GeV is measured with a 967 fb -1 data sample collected by the Belle detector at or near the $\Upsilon(nS)$ ($n=1, 2, ..., 5$) resonances. The $\Upsilon$(4260) state is observed, and its resonance parameters are determined. In addition, an excess of $π^+π^-J/ψ$ production around 4 GeV is observed. This feature can be described by a Breit-Wigner parameterization with properties that are consistent with the $\Upsilon$(4008) state that was previously reported by Belle. In a study of $\Upsilon$(4260)→$π^+π^-J/ψ$ decays, a structure is observed in the $M(\pi^{\pm}J/ψ)$ mass spectrum with 5.2$σ$ significance, with mass M=(3894.5±6.6±4.5)MeV/$c^2$ and width $Γ$=(63±24±26) MeV/$c^2$, where the errors are statistical and systematic, respectively. This structure can be interpreted as a new charged charmonium-like state.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Evidence for the decay B 0 → K + K - π 0

We report a search for charmless hadronic decays of neutral B mesons to the final state K + K - π 0 0. The results are based on a 711 fb -1 data sample that contains 772x10 6 $B$$\bar{B}$ pairs, and was collected at the Y(4S) resonance with the Belle detector at the KEKB asymmetric-energy e + e - collider. We find the first evidence for this decay with a significance of 3.5 standard deviations and measure its branching fraction as $\mathscr{B}$(B 0 --> K + K - π 0 ) = [2.17 ± 0.60(stat) ± 0.24 (syst)]x10 -6 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Measurement of the inclusive semileptonic branching fraction B ( B s 0 → X - ℓ + ν ℓ ) at Belle

Here, we report a measurement of the inclusive semileptonic B s 0 branching fraction in a 121 fb - 1 data sample collected near the Υ ( 5 S ) resonance with the Belle detector at the KEKB asymmetric energy e + e - collider. Events with B s 0 ( * ) B ¯ s 0 ( * ) pairs are selected by reconstructing a tag side D s + and identifying a signal side lepton ℓ + ( ℓ = e , μ ) that is required to have the same-sign charge to ensure that both originate from different B s 0 mesons. The B s 0 → X - ℓ + ν ℓ branching fraction is extracted from the ratio of the measured yields of D s + mesons and D s + ℓ + pairs and the known production and branching fractions. The inclusive semileptonic branching fraction is measured to be [ 10.6 ± 0.5 ( stat ) ± 0.7 ( syst ) ] % .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Search for heavy neutrinos at Belle

We report on a search for heavy neutrinos in B-meson decays. The results are obtained using a data sample that contains 772x10 6 BB-bar pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. No signal is observed and upper limits are set on mixing of heavy neutrinos with left-handed neutrinos of the Standard Model in the mass range 0.5 - 5.0 GeV/c 2 .

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