Application of Al-Cu-W-Ta graded density impactors in dynamic ramp compression experiments

Graded density impactors (GDIs) are used to dynamically compress materials to extreme conditions. Two modifications to a previously developed Mg-Cu-W GDI are made in this work before using it in a dynamic compression experiment: Mg is replaced with Al and a Ta disk is glued to the back. The Mg phase is replaced by Al because FCC Al remains solid to higher pressure along its Hugoniot compared to Mg. The addition of the Ta disk creates a constant particle velocity regime and facilitates a definition of peak pressure states. Microstructure analysis, profilometry, and ultrasonic C-scans of the Al-Cu-W GDI all confirm excellent uniformity. We evaluated signal variation in the radial direction of a dynamically compressed Al-LiF bilayer target to evaluate the contribution of spatial nonuniformity to errors. Velocity traces from five photon Doppler velocimetry (PDV) probes located at different radial distances from the center of the target varied at most by 1.1% with a root mean square of 0.3% during the compression ramp, demonstrating low PDV measurement error over a relatively large experimental area. The experimental PDV data also agrees well with 1D simulations that use inputs from predictive characterization models developed for the material properties resulting from tape casting, laminating, and powder consolidation processes. Low measurement error during quasi-isentropic compression, leading to better precision, ensures a robust platform to reach extreme compression and low-temperature recovery states and facilitates discovery via synthesis, quenching, and preservation of new high-pressure phases

Application of Al-Cu-W-Ta graded density impactors in dynamic ramp compression experiments

Graded density impactors (GDIs) are used to dynamically compress materials to extreme conditions. Two modifications to a previously developed Mg-Cu-W GDI are made in this work before using it in a dynamic compression experiment: Mg is replaced with Al and a Ta disk is glued to the back. The Mg phase is replaced by Al because FCC Al remains solid to higher pressure along its Hugoniot compared to Mg. The addition of the Ta disk creates a constant particle velocity regime and facilitates a definition of peak pressure states. Microstructure analysis, profilometry, and ultrasonic C-scans of the Al-Cu-W GDI all confirm excellent uniformity. We evaluated signal variation in the radial direction of a dynamically compressed Al-LiF bilayer target to evaluate the contribution of spatial nonuniformity to errors. Velocity traces from five photon Doppler velocimetry (PDV) probes located at different radial distances from the center of the target varied at most by 1.1% with a root mean square of 0.3% during the compression ramp, demonstrating low PDV measurement error over a relatively large experimental area. The experimental PDV data also agrees well with 1D simulations that use inputs from predictive characterization models developed for the material properties resulting from tape casting, laminating, and powder consolidation processes. Low measurement error during quasi-isentropic compression, leading to better precision, ensures a robust platform to reach extreme compression and low-temperature recovery states and facilitates discovery via synthesis, quenching, and preservation of new high-pressure phases

Measurement of Branching Fraction and Dalitz Distribution for B0->D(*)+/- K0 pi-/+ Decays

We present measurements of the branching fractions for the three-body decays B0 -> D(*)-/+ K0 pi^+/-$and their resonant submodes$B0 -> D(*)-/+ K*+/- using a sample of approximately 88 million BBbar pairs collected by the BABAR detector at the PEP-II asymmetric energy storage ring. We measure: B(B0->D-/+ K0 pi+/-)=(4.9 +/- 0.7(stat) +/- 0.5 (syst)) 10^{-4} B(B0->D*-/+ K0 pi+/-)=(3.0 +/- 0.7(stat) +/- 0.3 (syst)) 10^{-4} B(B0->D-/+ K*+/-)=(4.6 +/- 0.6(stat) +/- 0.5 (syst)) 10^{-4} B(B0->D*-/+ K*+/-)=(3.2 +/- 0.6(stat) +/- 0.3 (syst)) 10^{-4} From these measurements we determine the fractions of resonant events to be : f(B0-> D-/+ K*+/-) = 0.63 +/- 0.08(stat) +/- 0.04(syst) f(B0-> D*-/+ K*+/-) = 0.72 +/- 0.14(stat) +/- 0.05(syst)Comment: 7 pages, 3 figures submitted to Phys. Rev. Let

Study of e+e- --> pi+ pi- pi0 process using initial state radiation with BABAR

The process e+e- --> pi+ pi- pi0 gamma has been studied at a center-of-mass energy near the Y(4S) resonance using a 89.3 fb-1 data sample collected with the BaBar detector at the PEP-II collider. From the measured 3pi mass spectrum we have obtained the products of branching fractions for the omega and phi mesons, B(omega --> e+e-)B(omega --> 3pi)=(6.70 +/- 0.06 +/- 0.27)10-5 and B(phi --> e+e-)B(phi --> 3pi)=(4.30 +/- 0.08 +/- 0.21)10-5, and evaluated the e+e- --> pi+ pi- pi0 cross section for the e+e- center-of-mass energy range 1.05 to 3.00 GeV. About 900 e+e- --> J/psi gamma --> pi+ pi- pi0 gamma events have been selected and the branching fraction B(J/psi --> pi+ pi- pi0)=(2.18 +/- 0.19)% has been measured.Comment: 21 pages, 37 postscript figues, submitted to Phys. Rev.

Measurement of Branching Fractions for B0 ->K*2(1430)0 gamma and B+ -> K*2(1430)+ gamma

We have investigated the exclusive, radiative B-meson decay to K_2^*(1430) in 88.5 * 10^6 BBbar events. We present a preliminary measurement of the branching fractions BR(B->K^*_2(1430)^0 gamma) = (1.22+-0.25+-0.11) * 10^{-5} and BR(B->K^*_2(1430)^+ gamma) = (1.44+-0.40+-0.13) * 10^{-5}.Comment: 17 pages, 7 postscript figures, contributed to the 21st International Symposium on Lepton and Photon Interactions at High Energies, 8/11-8/16/2003, Fermilab, Illinois US

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

A search for the decay B+→K+ννˉB^+ \to K^+ \nu \bar{\nu}

We search for the rare flavor-changing neutral-current decay $B^+ \to K^+ \nu \bar{\nu}$ in a data sample of 82 fb$^{-1}$ collected with the {\sl BABAR} detector at the PEP-II B-factory. Signal events are selected by examining the properties of the system recoiling against either a reconstructed hadronic or semileptonic charged-B decay. Using these two independent samples we obtain a combined limit of ${\mathcal B}(B^+ \to K^+ \nu \bar{\nu})<5.2 \times 10^{-5}$ at the 90% confidence level. In addition, by selecting for pions rather than kaons, we obtain a limit of ${\mathcal B}(B^+ \to \pi^+ \nu \bar{\nu})<1.0 \times 10^{-4}$ using only the hadronic B reconstruction method.Comment: 7 pages, 8 postscript figures, submitted to Phys. Rev. Let

High-reflectivity broadband distributed Bragg reflector lattice matched to ZnTe

We report on the realization of a high quality distributed Bragg reflector with both high and low refractive index layers lattice matched to ZnTe. Our structure is grown by molecular beam epitaxy and is based on binary compounds only. The high refractive index layer is made of ZnTe, while the low index material is made of a short period triple superlattice containing MgSe, MgTe, and ZnTe. The high refractive index step of Delta_n=0.5 in the structure results in a broad stopband and the reflectivity coefficient exceeding 99% for only 15 Bragg pairs.Comment: 4 pages, 3 figure

Search for D0-D0bar Mixing Using Semileptonic Decay Modes

Based on an 87-fb$^{-1}$ dataset collected by the Babar detector at the PEP-II asymmetric-energy $B$-Factory, a search for $D^{0}$--$\bar{D}^{0}$ mixing has been made using the semileptonic decay modes $D^{*+} \to \pi^{+} D^{0}, D^{0} \to K^{(*)}e\nu$ (+c.c.). The use of these modes allows unambiguous flavor tagging and a combined fit of the $D^{0}$ decay time and $D^{*+}$--$D^{0}$ mass difference ($\Delta M$) distributions. The high-statistics sample of unmixed semileptonic $D^{0}$ decays is used to model the $\Delta M$ distribution and time-dependence of mixed events directly from the data. Neural networks are used to select events and reconstruct the $D^{0}$. A result consistent with no charm mixing has been obtained, $R_{\rm{mix}}=0.0023 \pm 0.0012 \pm 0.0004$. This corresponds to an upper limit of $R_{\rm{mix}}<0.0042$ (90% CL).Comment: submitted to Phys. Rev. D (Rapid Communications

Observation of the Decay B=> J/psi eta K and Search for X(3872)=> J/psi eta

We report the observation of the $B$ meson decay $B^\pm\to J/\psi \eta K^\pm$ and evidence for the decay $B^0\to J/\psi \eta K^0_S$, using {90} million $BBbar$ events collected at the \ensuremath{\Upsilon{(4S)}}\xspace resonance with the $BaBar$ detector at the PEP-II $e^+ e^-$ asymmetric-energy storage ring. We obtain branching fractions of $\cal{B}$$(B^\pm\to J/\psi \eta K^{\pm}$)=$(10.8\pm 2.3(\rm{stat.})\pm 2.4(\rm{syst.}))\times 10^{-5}$ and $\cal{B}$$(B^0\to J/\psi\eta K_{\rm{S}}^{0}$)=$(8.4\pm 2.6(\rm{stat.})\pm 2.7(\rm{syst.}))\times 10^{-5}$. We search for the new narrow mass state, the X(3872), recently reported by the Belle Collaboration, in the decay B^\pm\to X(3872)K^\pm, X(3872)\to \jpsi \eta and determine an upper limit of $\cal{B}$(B^\pm \to X(3872) K^\pm \to \jpsi \eta K^\pm) $<7.7\times 10^{-6}$ at 90% C.L.Comment: 7 pages and two figures, submitted to Phys. Rev. Lett