Engineering topics
Liu, F.
Publications and source records attributed to Liu, F..
Amplitude Analysis of B0 to K^ pi^-pi^0 and Evidence of Direct CP Violation in B to K^* pi decays
We analyze the decay B{sup 0} {yields} K{sup +} {pi}{sup -} {pi}{sup 0} with a sample of 454 million B{bar B} events collected by the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC, and extract the complex amplitudes of seven interfering resonances over the Dalitz plot. These results are combined with amplitudes measured in B{sup 0} {yields} K{sup 0}{sub s}{pi}{sup +}{pi}{sup -} decays to construct isospin amplitudes from B{sup 0} {yields} K{sup *}{pi} and B{sup 0} {yields} {rho}K decays. We measure the phase of the isospin amplitude {Phi}{sub 3/2}, useful in constraining the CKM unitarity triangle angle {gamma} and evaluate a CP rate asymmetry sum rule sensitive to the presence of new physics operators. We measure direct CP violation in B{sup 0} {yields} K{sup *+}{pi}{sup -} decays at the level of 3 {sigma} when measurements from both B{sup 0} {yields} K{sup +}{pi}{sup -}{pi}{sup 0} and B{sup 0} {yields} K{sup 0}{sub s}{pi}{sup +}{pi}{sup -} decays are combined.
Measurement of the γγ*→η and γγ*→η' transition form factors
We study the reactions e⁺e⁻→e⁺e⁻η (') in the single-tag mode and measure the γγ*→η (') transition form factors in the momentum-transfer range from 4 to 40 GeV². The analysis is based on 469 fb⁻¹ of integrated luminosity collected at PEP-II with the BABAR detector at e⁺e⁻ center-of-mass energies near 10.6 GeV.
Search for CP Violation in the Decay D+/- to Ks pi+/-
We report on a search for CP violation in the decay D{sup {+-}} {yields} K{sub S}{sup 0}{pi}{sup {+-}} using a data set corresponding to an integrated luminosity of 469 fb{sup -1} collected with the BABAR detector at the PEP-II asymmetric energy e{sup +}e{sup -} storage rings. The CP-violating decay rate asymmetry A{sub CP} is determined to be (-0.44 {+-} 0.13(stat) {+-} 0.10(syst))%, consistent with zero at 2.7 {sigma} and with the standard model prediction of (-0.332 {+-} 0.006)%. This is currently the most precise measurement of this parameter.
Measurement of the Mass and Width of the Ds1(2536)+ Meson
The decay width and mass of the D{sub s1}(2536){sup +} meson are measured via the decay channel D{sub s1}{sup +} {yields} D*{sup +} K{sub S}{sup 0} using 385 fb{sup -1} of data recorded with the BABAR detector in the vicinity of the {Upsilon}(4S) resonance at the PEP-II asymmetric-energy electron-positron collider. The result for the decay width is {Gamma}(D{sub s1}{sup +}) = 0.92 {+-} 0.03 (stat.) {+-} 0.04 (syst.)MeV. For the mass, a value of m(D{sub s1}{sup +}) = 2535.08 {+-} 0.01 (stat.) {+-} 0.15 (syst.)MeV/c{sup 2} is obtained. The mass difference between the D{sub s1}{sup +} and the D*{sup +} is measured to be m(D{sub s1}{sup +})-m(D*{sup +}) = 524.83 {+-} 0.01 (stat.) {+-} 0.04 (syst.)MeV/c{sup 2}, representing a significant improvement compared to the current world average. The unnatural spin-parity assignment for the D{sub s1}{sup +} meson is confirmed.
Measurements of Branching Fractions and CP Asymmetries and Studies of Angular Distributions for B to phi phi K Decays
We present branching fraction and CP asymmetry measurements as well as angular studies of B {yields} {phi}{phi}K decays using 464 x 10{sup 6} B{bar B} events collected by the BABAR experiment. The branching fractions are measured in the {phi}{phi} invariant mass range below the {eta}{sub c} resonance (m{sub {phi}{phi}} < 2.85 GeV). We find {Beta}(B{sup +} {yields} {phi}{phi}K{sup +}) = (5.6 {+-} 0.5 {+-} 0.3) x 10{sup -6} and {Beta}(B{sup 0} {yields} {phi}{phi}K{sup 0}) = (4.5 {+-} 0.8 {+-} 0.3) x 10{sup -6}, where the first uncertaintiy is statistical and the second systematic. The measured direct CP asymmetries for the B{sup {+-}} decays are A{sub CP} = -0.10 {+-} 0.08 {+-} 0.02 below the {eta}{sub c} threshold (m{sub {phi}{phi}} < 2.85 GeV) and A{sub CP} = 0.09 {+-} 0.10 {+-} 0.02 in the {eta}{sub c} resonance region (m{sub {phi}{phi}} in [2.94,3.02] GeV). Angular distributions are consistent with J{sub P} = 0{sup -} in the {eta}{sub c} resonance region and favor J{sup P} = 0{sup +} below the {eta}{sub c} resonance.
Measurements of branching fractions, polarizations, and direct CP-violation asymmetries in B -> rho0 K* and B -> f0(980) K* decays
We present measurements of the branching fractions, longitudinal polarization, and direct CP-violation asymmetries for the decays B{sup +} {yields} {rho}{sup 0}K*{sup +} and B{sup +} f{sub 0}(980)K*{sup +} with a sample of (467 {+-} 5) x 10{sup 6} B{bar B} pairs collected with the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} collider at the SLAC National Accelerator Laboratory. We observe B{sup +} {yields} {rho}{sup 0}K*{sup +} with a significance of 5.3{sigma} and measure the branching fraction {Beta}(B{sup +} {yields} {rho}{sup 0}K*{sup +}) = (4.6 {+-} 1.0 {+-} 0.4) x 10{sup -6}, the longitudinal polarization f{sub L} = 0.78 {+-} 0.12 {+-} 0.03, and the CP-violation asymmetry A{sub CP} = 0.31 {+-} 0.13 {+-} 0.03. We observe B{sup +} {yields} f{sub 0}(980)K*{sup +} and measure the branching fraction {Beta}(B{sup +} {yields} f{sub 0}(980)K*{sup +}) x {Beta}(f{sub 0}(980) {yields} {pi}{sup +}{pi}{sup -}) = (4.2 {+-} 0.6 {+-} 0.3) x 10{sup -6} and the CP-violation asymmetry A{sub CP} = -0.15 {+-} 0.12 {+-} 0.03. The first uncertainty quoted is statistical and the second is systematic.
Observation of the Decay B- --> Ds(*) K- l- nubar
We report the observation of the decay B{sup -} {yields} D{sub s}{sup (*)+} K{sup -}{ell}{sup -}{bar {nu}}{sub {ell}} based on 342 fb{sup -1} of data collected at the {Upsilon}(4S) resonance with the BABAR detector at the PEP-II e{sup +}e{sup -} storage rings at SLAC. A simultaneous fit to three D{sub s}{sup +} decay chains is performed to extract the signal yield from measurements of the squared missing mass in the B meson decay. We observe the decay B{sup -} {yields} D{sub s}{sup (*)+} K{sup -}{ell}{sup -}{bar {nu}}{sub {ell}} with a significance greater than five standard deviations (including systematic uncertainties) and measure its branching fraction to be {Beta}(B{sup -} {yields} D{sub s}{sup (*)+} K{sup -}{ell}{sup -}{bar {nu}}{sub {ell}}) = [6.13{sub -1.03}{sup +1.04}(stat.) {+-} 0.43(syst.) {+-} 0.51({Beta}(D{sub s}))] x 10{sup -4}, where the last error reflects the limited knowledge of the D{sub s} branching fractions.
Observation of η c (1S) and η c (2S) decays to K + K - π + π - π 0 in two-photon interactions
Not Available
Dalitz Analysis of Ds -> K K- pi-
We perform a Dalitz plot analysis of about 100,000 D{sub s}{sup +} decays to K{sup +}K{sup -}{pi}{sup +} and measure the complex amplitudes of the intermediate resonances which contribute to this decay mode. We also measure the relative branching fractions of D{sub s}{sup +} {yields} K{sup +}K{sup +}{pi}{sup -} and D{sub s}{sup +} {yields} K{sup +}K{sup +}K{sup -}. For this analysis we use a 384 fb{sup -1} data sample, recorded by the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} collider running at center-of-mass energies near 10.58 GeV.
Search for b→u transitions in B ± →[K ∓ π ± π⁰] D K ± decays
We present a study of the decays B ± →DK ± with D mesons reconstructed in the K⁺π⁻π⁰ or K⁻π⁺π⁰ final states, where D indicates a D⁰ or a D¯¯¯0 meson. Using a sample of 474×10⁶ BB¯¯¯ pairs collected with the BABAR detector at the PEP-II asymmetric-energy e⁺e⁻ collider at SLAC, we measure the ratios R ± ≡((Γ(B ± →[K ∓ π ± π⁰]DK ± ))/((Γ(B ± →[K ± π ∓ π⁰]DK ± )). We obtain R⁺=(5 ⁺12 ⁻10 (stat) ⁺2 ⁻4 (syst))×10⁻³ and R⁻=(12 ⁺12 ⁻10 (stat) ⁺3 ⁻5 (syst))×10⁻³, from which we extract the upper limits at 90% probability: R⁺<23×10⁻³ and R⁻<29×10⁻³. Using these measurements, we obtain an upper limit for the ratio r B of the magnitudes of the b→u and b→c amplitudes r B <0.13 at 90% probability.
Search for Production of Invisible Final States in Single-Photon Decays of Υ ( 1 S )
We search for single-photon decays of the Υ(1S) resonance, Υ → γ + invisible, where the invisible state is either a particle of definite mass, such as a light Higgs boson A 0 , or a pair of dark matter particles, χ¯χ. Both A 0 and χ are assumed to have zero spin. We tag Υ(1S) decays with a dipion transition Υ(2S) → π + π – Υ(1S) and look for events with a single energetic photon and significant missing energy. Here, we find no evidence for such processes in the mass range m A 0 ≤ 9.2 GeV and m χ ≤ 4.5 GeV in the sample of 98 × 10 6 Υ(2S) decays collected with the BABAR detector and set stringent limits on new physics models that contain light dark matter states.
Searches for the baryon- and lepton-number violating decays B 0 → Λ c + l − , B − → Λ l − , and B − → Λ ¯ l −
Not Available
Measurement of the B⁰→π⁻l⁺ν and B⁺→η (') l⁺ν branching fractions, the B⁰→π⁻l⁺ν and B⁺→ηl⁺ν form-factor shapes, and determination of |V ub |
We report the results of a study of the exclusive charmless semileptonic decays, B⁺→η (') l⁺ν and B⁰→π⁻l⁺ν, undertaken with approximately 464×10⁶ BB¯¯ pairs collected at the Υ(4S) resonance with the BABAR detector. The analysis uses events in which the signal B decays are reconstructed with a loose neutrino reconstruction technique. We obtain partial branching fractions for B⁺→ηl⁺ν and B⁰→π⁻l⁺ν decays in three and 12 bins of q², respectively, from which we extract the f+(q²) form-factor shapes and the total branching fractions B(B⁺→ηl⁺ν)=(0.36±0.05 stat ±0.04 syst )×10⁻⁴ and B(B⁰→π⁻l⁺ν)=(1.42±0.05 stat ±0.07 syst )×10⁻⁴. We also measure B(B+→η'l⁺ν)=(0.24±0.08 stat ±0.03 syst )×10⁻⁴. We obtain values for the magnitude of the CKM matrix element |Vub| using three different QCD calculations.
The low temperature microgravity physics facility: progress and status
JPL is developing the Low Temperature Microgravity Physics Facility. The LTMPF is a multiple user and multiple flight facility that will provide a long duration low temperature environment for performing state of the art experiments at the International Space Station.