Douglas Wright

Geant4 is a software toolkit for the simulation of the passage of particles through matter. It is used by a large number of experiments and projects in a variety of application domains, including high energy physics, astrophysics and space science, medical physics and radiation protection. Over the past several years, major changes have been made to the toolkit in order to accommodate the needs of these user communities, and to efficiently exploit the growth of computing power made available by advances in technology. The adaptation of Geant4 to multithreading, advances in physics, detector modeling and visualization, extensions to the toolkit, including biasing and reverse Monte Carlo, and tools for physics and release validation are discussed here.

We search for single-photon events in 53 fb^{-1} of e^{+}e^{-} collision data collected with the BABAR detector at the PEP-II B-Factory. We look for events with a single high-energy photon and a large missing momentum and energy, consistent with production of a spin-1 particle A^{'} through the process e^{+}e^{-}→γA^{'}; A^{'}→invisible. Such particles, referred to as "dark photons," are motivated by theories applying a U(1) gauge symmetry to dark matter. We find no evidence for such processes and set 90% confidence level upper limits on the coupling strength of A^{'} to e^{+}e^{-} in the mass range m_{A^{'}}≤8 GeV. In particular, our limits exclude the values of the A^{'} coupling suggested by the dark-photon interpretation of the muon (g-2)_{μ} anomaly, as well as a broad range of parameters for the dark-sector models.

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 ${Z}^{\ensuremath{'}}$ coupling only to the second and third generations of leptons in the reaction ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}{Z}^{\ensuremath{'}},{Z}^{\ensuremath{'}}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ using $514\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of data collected by the BABAR experiment. No significant signal is observed for ${Z}^{\ensuremath{'}}$ masses in the range 0.212--10 GeV. Limits on the coupling parameter ${g}^{\ensuremath{'}}$ as low as $7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ are derived, leading to improvements in the bounds compared to those previously derived from neutrino experiments.

An angular analysis of the decay B[over ¯]→D^{*}ℓ^{-}ν[over ¯]_{ℓ}, ℓ∈{e,μ}, is reported using the full e^{+}e^{-} collision data set collected by the BABAR experiment at the ϒ(4S) resonance. One B meson from the ϒ(4S)→BB[over ¯] decay is fully reconstructed in a hadronic decay mode, which constrains the kinematics and provides a determination of the neutrino momentum vector. The kinematics of the semileptonic decay is described by the dilepton mass squared, q^{2}, and three angles. The first unbinned fit to the full four-dimensional decay rate in the standard model is performed in the so-called Boyd-Grinstein-Lebed approach, which employs a generic q^{2} parametrization of the underlying form factors based on crossing symmetry, analyticity, and QCD dispersion relations for the amplitudes. A fit using the more model-dependent Caprini-Lellouch-Neubert (CLN) approach is performed as well. Our form factor shapes show deviations from previous fits based on the CLN parametrization. The latest form factors also provide an updated prediction for the branching fraction ratio R(D^{*})≡B(B[over ¯]→D^{*}τ^{-}ν[over ¯]_{τ})/B(B[over ¯]→D^{*}ℓ^{-}ν[over ¯]_{ℓ})=0.253±0.005. Finally, using the well-measured branching fraction for the B[over ¯]→D^{*}ℓ^{-}ν[over ¯]_{ℓ} decay, a value of |V_{cb}|=(38.36±0.90)×10^{-3} is obtained that is consistent with the current world average for exclusive B[over ¯]→D^{(*)}ℓ^{-}ν[over ¯]_{ℓ} decays and remains in tension with the determination from inclusive semileptonic B decays to final states with charm.

We report on the development of high-sensitivity and compact Compton imaging systems built of large and position-sensitive Si(Li) and HPGe detectors. The primary goal of this effort is to provide improved capabilities in the passive detection of nuclear materials for homeland security. Our detectors are implemented in double-sided strip configuration, which—along with digital signal processing—provides energies and three-dimensional position information of individual γ-ray interactions. γ-Ray tracking algorithms then determine the scattering sequence of the γ-ray, which in turn allows us—employing the Compton scattering formula—to reconstruct a cone of possible incident angles and ultimately an image. This Compton imaging concept enables large-field-of-view γ-ray imaging without the use of a heavy collimator or aperture. The intrinsically high-energy resolution of the detectors used, the excellent position resolution we have demonstrated, both combined with the high efficiency of large-volume detectors is the basis for high Compton imaging sensitivity. These capabilities are being developed to identify and localize potential threat sources and to potentially increase the sensitivity in detecting weak sources out of the midst of natural, medical, or commercial sources. γ-ray imaging provides a new degree of freedom to distinguish between spatial and temporal background fluctuations and compact threat sources.

We study the processes $\gamma \gamma \to \eta_c \to \eta' K^+ K^-$, $\eta' \pi^+ \pi^-$, and $\eta \pi^+ \pi^-$ 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 $\Upsilon(nS)$ ($n = 2,3,4$) resonances. This is the first observation of the decay $\eta_c \to \eta' K^+ K^-$ and we measure the branching fraction $\Gamma(\eta_c \to \eta' K^+ K^-)/(\Gamma(\eta_c \to \eta' \pi^+ \pi^-)=0.644\pm 0.039_{\rm stat}\pm 0.032_{\rm sys}$. Significant interference is observed between $\gamma \gamma \to \eta_c\to \eta \pi^+ \pi^-$ and the non-resonant two-photon process $\gamma \gamma \to \eta \pi^+ \pi^-$. A Dalitz plot analysis is performed of $\eta_c$ decays to $\eta' K^+ K^-$, $\eta' \pi^+ \pi^-$, and $\eta \pi^+ \pi^-$. Combined with our previous analysis of $\eta_c \to K \bar K \pi$, we measure the $K^*_0(1430)$ parameters and the ratio between its $\eta' K$ and $\pi K$ couplings. The decay $\eta_c \to \eta' \pi^+ \pi^-$ is dominated by the $f_0(2100)$ resonance, also observed in $J/\psi$ radiative decays. A new $a_0(1700) \to \eta \pi$ resonance is observed in the $\eta_c \to \eta \pi^+ \pi^-$ channel. We also compare $\eta_c$ decays to $\eta$ and $\eta'$ final states in association with scalar mesons as they relate to the identification of the scalar glueball.

The decay ${\ensuremath{\tau}}^{\ensuremath{-}}\ensuremath{\rightarrow}{K}^{\ensuremath{-}}{K}_{S}{\ensuremath{\nu}}_{\ensuremath{\tau}}$ has been studied using $430\ifmmode\times\else\texttimes\fi{}{10}^{6}$ ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\tau}}^{+}{\ensuremath{\tau}}^{\ensuremath{-}}$ events produced at a center-of-mass energy around 10.6 GeV at the PEP-II collider and studied with the BABAR detector. The mass spectrum of the ${K}^{\ensuremath{-}}{K}_{S}$ system has been measured and the spectral function has been obtained. The measured branching fraction $\mathcal{B}({\ensuremath{\tau}}^{\ensuremath{-}}\ensuremath{\rightarrow}{K}^{\ensuremath{-}}{K}_{S}{\ensuremath{\nu}}_{\ensuremath{\tau}})=(0.739\ifmmode\pm\else\textpm\fi{}0.011(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.020(\mathrm{syst}))\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ is found to be in agreement with earlier measurements.

A new mechanism has been proposed to simultaneously explain the presence of dark matter and the matter-antimatter asymmetry in the universe. This scenario predicts exotic $B$ meson decays into a baryon and a dark sector anti-baryon ($\psi_D$) with branching fractions accessible at $B$ factories. We present a search for $B \rightarrow \Lambda \psi_D$ decays using data collected by the $BABAR$ experiment at SLAC. This reaction is identified by fully reconstructing the accompanying $B$ meson and requiring the presence of a single $\Lambda$ baryon in the remaining particles. No significant signal is observed, and bounds on the $B \rightarrow \Lambda \psi_D$ branching fraction are derived in the range $0.13 - 5.2\times 10^{-5}$ for $1.0 < m_{\psi_D} < 4.2$ GeV/$c^{2}$. These results set strong constraints on the parameter space allowed by the theory.

Axionlike particles (ALPs) are predicted in many extensions of the standard model, and their masses can naturally be well below the electroweak scale. In the presence of couplings to electroweak bosons, these particles could be emitted in flavor-changing B meson decays. We report herein a search for an ALP, a, in the reaction B^{±}→K^{±}a, a→γγ using data collected by the BABAR experiment at SLAC. No significant signal is observed, and 90% confidence level upper limits on the ALP coupling to electroweak bosons are derived as a function of ALP mass, improving current constraints by several orders of magnitude in the range 0.175 GeV<m_{a}<4.78 GeV.

Based on the full BABAR data sample of 466.5 million $B\overline{B}$ 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 $B\ensuremath{\rightarrow}{X}_{u}e\ensuremath{\nu}$ decays from the CKM-favored $B\ensuremath{\rightarrow}{X}_{c}e\ensuremath{\nu}$ decays, and from various other backgrounds, and determine the total semileptonic branching fraction $\mathcal{B}(B\ensuremath{\rightarrow}Xe\ensuremath{\nu})=(10.34\ifmmode\pm\else\textpm\fi{}{0.04}_{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}0.2{6}_{\mathrm{syst}})%$, averaged over ${B}^{\ifmmode\pm\else\textpm\fi{}}$ and ${B}^{0}$ mesons. We determine the spectrum and branching fraction for charmless $B\ensuremath{\rightarrow}{X}_{u}e\ensuremath{\nu}$ 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 $2.1\text{ }\text{ }\mathrm{GeV}/c$ 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 $0.8\text{ }\text{ }\mathrm{GeV}/c$ to the kinematic endpoint. We determine $|{V}_{ub}|$ using each of these different calculations and find, $|{V}_{ub}|=(3.794\ifmmode\pm\else\textpm\fi{}{0.107}_{\mathrm{exp}}{\text{ }}_{\ensuremath{-}0.219\text{ }\mathrm{SF}}^{+0.292}{\text{ }}_{\ensuremath{-}0.068\text{ }\text{theory}}^{+0.078})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ (De Fazio and Neubert), $(4.563\ifmmode\pm\else\textpm\fi{}{0.126}_{\mathrm{exp}}{\text{ }}_{\ensuremath{-}0.208\text{ }\mathrm{SF}}^{+0.230}{\text{ }}_{\ensuremath{-}0.163\text{ }\text{theory}}^{+0.162})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ (Bosch, Lange, Neubert, and Paz), $(3.959\ifmmode\pm\else\textpm\fi{}{0.104}_{\mathrm{exp}}{\text{ }}_{\ensuremath{-}0.154\text{ }\mathrm{SF}}^{+0.164}{\text{ }}_{\ensuremath{-}0.079\text{ }\text{theory}}^{+0.042})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ (Gambino, Giordano, Ossola, and Uraltsev), $(3.848\ifmmode\pm\else\textpm\fi{}{0.108}_{\mathrm{exp}}{\text{ }}_{\ensuremath{-}0.070\text{ }\text{theory}}^{+0.084})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ (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.

This article presents a model-independent search for an additional, mostly sterile, heavy neutral lepton (HNL), that is capable of mixing with the Standard Model $\ensuremath{\tau}$ neutrino with a mixing strength of $|{U}_{\ensuremath{\tau}4}{|}^{2}$, corresponding to the absolute square of the extended Pontecorvo-Maki-Nakagawa-Sakata matrix element. Data from the BABAR experiment, with a total integrated luminosity of $424\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$, are analyzed using a kinematic approach that makes no assumptions on the model behind the origins of the HNL, its lifetime or decay modes. No significant signal is found. Upper limits on $|{U}_{\ensuremath{\tau}4}{|}^{2}$ at the 95% confidence level, depend on the HNL mass hypothesis and vary from $2.31\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}2}$ to $5.04\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ (with all uncertainties considered), across the mass range $100&lt;{m}_{4}&lt;1300\text{ }\text{ }\mathrm{MeV}/{c}^{2}$; the more stringent limits being placed at higher masses.

We study the processes ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{K}^{+}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}\ensuremath{\gamma}$, ${K}_{S}^{0}{K}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\pi}}^{\ensuremath{\mp}}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}\ensuremath{\gamma}$, and ${K}_{S}^{0}{K}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\pi}}^{\ensuremath{\mp}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{\gamma}$ in which an energetic photon is radiated from the initial state. The data were collected with the BABAR detector at the SLAC National Accelerator Laboratory. About 1200, 2600, and 6000 events, respectively, are selected from a data sample corresponding to an integrated luminosity of $469\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$. The invariant mass of the hadronic final state defines the effective ${e}^{+}{e}^{\ensuremath{-}}$ center-of-mass energy. The center-of-mass energies range from threshold to 4.5 GeV. From the mass spectra, the first ever measurements of the ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{K}^{+}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}$, ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{K}_{S}^{0}{K}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\pi}}^{\ensuremath{\mp}}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}$, and ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{K}_{S}^{0}{K}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\pi}}^{\ensuremath{\mp}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ cross sections are performed. The contributions from the intermediate states that include $\ensuremath{\eta}$, $\ensuremath{\phi}$, $\ensuremath{\rho}$, ${K}^{*}(892)$, and other resonances are presented. We observe the $J/\ensuremath{\psi}$ and $\ensuremath{\psi}(2S)$ in most of these final states and measure the corresponding branching fractions, many of them for the first time.

A dedicated measurement of additional radiation in e+e−→μ+μ−γ and e+e−→π+π−γ initial-state-radiation events is presented using the full BABAR data sample. For the first time results are presented at next-to- and next-to-next-to-leading order, with one and two additional photons, respectively, for radiation from the initial and final states. Comparison with predictions from phokhara and afkqed Monte Carlo generators is performed, revealing discrepancies in the one-photon rates and angular distributions for the former. This disagreement has a negligible effect on the BABAR measurement of the e+e−→π+π−(γ) cross section, but could affect other measurements significantly. This study sheds a new light on the longstanding discrepancy in this channel that affects the theoretical prediction of hadronic vacuum polarization contributions to the muon magnetic moment anomaly.1 MoreReceived 11 August 2023Revised 16 October 2023Accepted 14 November 2023DOI:https://doi.org/10.1103/PhysRevD.108.L111103Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasElectroweak interactionQuantum electrodynamicsParticles & Fields

Small fiber neuropathy (SFN) is a widespread complication that leads to pain, burning, or loss of sensation in the distal limbs. A hallmark of SFN is a loss of intraepidermal nerve fibers (IENF). Currently, therapeutic options for humans with SFN are severely lacking. However, preclinical studies have identified numerous drugs that stimulate IENF regeneration in rodents but have not yet translated to human use. Here, we leveraged existing information from published articles to identify all drugs that have reported IENF regenerative effects in rodents. As part of a larger scoping review on IENF, we identified a subset of articles that reported increased IENF density in rodent models. Using PubMed, 323 initial articles were narrowed down using specific inclusion criteria. We analyzed 72 articles and categorized the successful drugs into seven groups based on implied mechanisms of action. The mechanistic categories include metabolic (38%), antioxidant (23%), hormonal (18%), anti-inflammatory (11%), stem cell (6%), electrophysiological (3%), and unknown mechanisms (1%). The models used to test these drugs include diabetic, chemotherapeutic, and toxic models, suggesting a narrow set of preclinical models to address IENF regeneration. There are additional diseases and conditions in which IENF loss has been reported, including neurodegenerative and autoimmune models that should be explored and may provide new perspectives. This information will identify critical roadblocks, allow us to focus on specific mechanisms, and narrow the areas where we should exert effort to identify new treatments or modify existing drugs to use in humans with SFN. Funding: R01NS043314-17, 5P20GM103418.

Using the initial-state radiation method, the ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{K}_{S}{K}_{L}$ cross section from 1.98 to 2.54 GeV is measured in a data sample of $469\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ collected with the BABAR detector. The results are used in conjunction with previous BABAR results for the ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{K}^{+}{K}^{\ensuremath{-}}$, ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$, ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{\eta}$, and ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\omega}\ensuremath{\pi}\ensuremath{\pi}$ cross sections to investigate the nature of the resonance structure recently observed by the BESIII experiment in the ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{K}^{+}{K}^{\ensuremath{-}}$ cross section.

We study the processes $\ensuremath{\gamma}\ensuremath{\gamma}\ensuremath{\rightarrow}{K}_{S}^{0}{K}^{\ifmmode\pm\else\textpm\fi{}}{\ensuremath{\pi}}^{\ensuremath{\mp}}$ and $\ensuremath{\gamma}\ensuremath{\gamma}\ensuremath{\rightarrow}{K}^{+}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}$ using a data sample of $519\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ recorded with the BABAR detector operating at the SLAC PEP-II asymmetric-energy ${e}^{+}{e}^{\ensuremath{-}}$ collider at center-of-mass energies at and near the $\mathrm{\ensuremath{\Upsilon}}(nS)$ ($n=2$, 3, 4) resonances. We observe ${\ensuremath{\eta}}_{c}$ 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 $I=1/2$ $K\ensuremath{\pi}\text{ }\mathcal{S}$-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 $1.5\text{ }\text{ }\mathrm{GeV}/{c}^{2}$. In contrast, the amplitudes show very marked differences. The data require the presence of a new ${a}_{0}(1950)$ resonance with parameters $m=1931\ifmmode\pm\else\textpm\fi{}14\ifmmode\pm\else\textpm\fi{}22\text{ }\text{ }\mathrm{MeV}/{c}^{2}$ and $\mathrm{\ensuremath{\Gamma}}=271\ifmmode\pm\else\textpm\fi{}22\ifmmode\pm\else\textpm\fi{}29\text{ }\text{ }\mathrm{MeV}$.

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

The BaBar experiment at PEPII relies on the instrumentation of the flux return (IFR) for both muon identification and KL detection. The active detector is composed of resistive plate chambers (RPCs) operated in streamer mode. Since the start of operation the RPCs have suffered persistent efficiency deterioration and dark current increase problems. The “autopsy” of bad BaBar RPCs revealed that in many cases uncured linseed oil droplets had formed on the inner surface of the Bakelite plates, leading to current paths from oil “stalagmites” bridging the 2 mm gap. In this paper, a possible model of this “stalagmite” formation and its effect on the dark current and efficiency of RPC chambers is presented. Laboratory test results strongly support this model. Based upon this model we are searching for solutions to eliminate the unfavorable effect of the oil stalagmites. The lab tests show that the stalagmite resistivity increases dramatically if exposed to the air, an observation that points to a possible way to remedy the damage and increase the efficiency. We have seen that flowing an oxygen gas mixture into the chamber helps to polymerize the uncured linseed oil. Consequently, the resistivity of the bridged oil stalagmites increases, as does that of the oil coating on the frame edges and spacers, significantly reducing the RPC dark currents and low-efficiency regions. We have tested this idea on two chambers removed from BaBar because of their low efficiency and high dark current. These test results are reported in the paper, and two other remediation methods also mentioned. We continue to study this problem, and try to find new treatments with permanent improvement.

The muon and neutral hadron detector (instrumented flux return or IFR) in the forward endcap of the BaBar detector at SLAC was upgraded by the installation of a new generation of resistive plate chambers (RPCs) and by increasing the absorber. The chamber replacement was made necessary by the rapid aging and efficiency loss of the original BaBar RPCs. Based on our experience with those original RPCs and 24 RPCs with thinner linseed oil treatments, improvements in the design, construction, and testing of the new generation RPCs were implemented and are described in detail.

Using a sample of (470.9 +- 2.8) x 10^6 BB-bar pairs, we measure the decay branching fraction B(B^0 -> D^*- pi^+ pi^- pi^+) = (7.26 +- 0.11 +- 0.31) x 10^-3, where the first uncertainty is statistical and the second is systematic. Our measurement will be helpful in studies of lepton universality by measuring B(B^0 -> D^*- tau^+ nu_tau) using tau^+ -> pi^+ pi^- pi^+ nu-bar_tau decays, normalized to B(B^0 -> D^*- pi^+ pi^- pi^+.

We present a search for seven lepton-flavor-violating neutral charm meson decays of the type D0→X0e±μ∓, where X0 represents a π0, K0S, ¯K*0, ρ0, ϕ, ω, or η meson. The analysis is based on 468 fb−1 of e+e− annihilation data collected at or close to the Υ(4S) resonance with the BABAR detector at the SLAC National Accelerator Laboratory. No significant signals are observed, and we establish 90% confidence level upper limits on the branching fractions in the range (5.0−22.5)×10−7. The limits are between 1 and 2 orders of magnitude more stringent than previous measurements.Received 21 April 2020Accepted 26 May 2020DOI:https://doi.org/10.1103/PhysRevD.101.112003Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.Published by the American Physical SocietyPhysics Subject Headings (PhySH)PropertiesSymmetriesParticles & Fields

With the nuclear weapons program moving to Science Based Stockpile Stewardship (SBSS), new diagnostic techniques are needed to replace weapons testing. Proton Radiography is being developed within the SBSS program as one such tool. It is analogous to transmission X-ray radiography, but uses protons instead of photons. Proton Radiography has high penetrating power, high detection efficiency, small-scattered background, inherent multi-pulse capability, and large standoff distances between test objects and detectors. Multiple images on a single axis through progressively smaller angle-cutting apertures can provide material identification. Proton Radiography can make multi-axis, multi-frame radiographs: i.e., 3D radiographic movies. This approach to SBSS is being developed at the Los Alamos National Laboratory (LANL) and the Lawrence Livermore National Laboratory (LLNL). This new method of radiography, as well as radiography experiments performed at the LANSCE accelerator at LANL and at the Alternating Gradient Synchrotron (AGS) at Brookhaven National Laboratory, are discussed.

We report on a precision measurement of the ratio ${\cal R}_{\tau\mu}^{\Upsilon(3S)} = {\cal B}(\Upsilon(3S)\to\tau^+\tau^-)/{\cal B}(\Upsilon(3S)\to\mu^+\mu^-)$ using data collected with the BaBar detector at the SLAC PEP-II $e^+e^-$ collider. The measurement is based on a 28 fb$^{-1}$ data sample collected at a center-of-mass energy of 10.355 GeV corresponding to a sample of 122 million $\Upsilon(3S)$ mesons. The ratio is measured to be ${\cal R}_{\tau\mu}^{\Upsilon(3S)} = 0.966 \pm 0.008_\mathrm{stat} \pm 0.014_\mathrm{syst}$ and is in agreement with the Standard Model prediction of 0.9948 within 2 standard deviations. The uncertainty in ${\cal R}_{\tau\mu}^{\Upsilon(3S)}$ is almost an order of magnitude smaller than the only previous measurement.

The BaBar Collaboration has operated an instrumented flux return (IFR) system covering over 2000m2 with resistive plate chambers (RPCs) for nearly 3 years. The chambers are constructed of bakelite sheets separated by 2mm. The inner surfaces are coated with linseed oil. This system provides muon and neutral hadron detection for BaBar. Installation and commissioning were completed in 1998, and operation began mid-year 1999. While initial performance of the system reached design, over time, a significant fraction of the RPCs demonstrated significant degradation, marked by increased currents and reduced efficiency. A coordinated effort of investigations have identified many of the elements responsible for the degradation. This article presents our current understanding of the aging process of the BaBar RPCs along with the action plan to combat performance degradation of the IFR system.

At Lawrence Livermore National Laboratory, we are pursuing the development of a gamma-ray imaging system using the Compton effect. We have built our first generation hybrid Compton imaging system, and we have conducted initial calibration and image measurements using this system. In this paper, we present the details of the hybrid Compton imaging system and initial calibration and image measurements

Background: Previously reported fusion-evaporation cross sections of residues in $^{45}\mathrm{Sc}$-induced reactions with lanthanide targets are much smaller than $^{48}\mathrm{Ca}$-induced reactions on the same targets. $^{44}\mathrm{Ca}$ is one proton removed from $^{45}\mathrm{Sc}$ and could be used to produce nuclei with a relative neutron content between those produced in the $^{45}\text{Sc-}$ and $^{48}\mathrm{Ca}$-induced reactions.Purpose: Several experiments worldwide have attempted to discover elements beyond the currently heaviest known element, oganesson ($Z=118$). Due to a lack of appropriate targets, these efforts focused on projectiles other than $^{48}\mathrm{Ca}$, which has been widely used for a number of successful element discovery experiments. The present study continues our previous work to understand the influence of various projectiles on the compound nucleus in fusion-evaporation reactions, and addresses the influence of target neutron number on fusion-evaporation cross sections.Methods: In experiments performed at the Cyclotron Institute at Texas A University, a beam of $^{44}\mathrm{Ca}^{6+}$ with an energy of $\ensuremath{\approx}5\phantom{\rule{0.16em}{0ex}}\mathrm{MeV}/u$ was delivered by the K500 superconducting cyclotron to the Momentum Achromat Recoil Spectrometer (MARS). The $^{44}\mathrm{Ca}$ projectiles bombarded various isotopically enriched Gd targets in the MARS target chamber to create evaporation residues, which were spatially separated from unreacted projectiles by MARS and identified via their characteristic $\ensuremath{\alpha}\text{\ensuremath{-}}\mathrm{decay}$ energies. Excitation functions for the reactions of $^{44}\mathrm{Ca}$ with $^{154,156,157,160}\mathrm{Gd}$ were measured at several projectile energies each.Results: The maximum $4n$ cross sections in the $^{44}\mathrm{Ca}{+}^{154,156,157,160}\mathrm{Gd}$ reactions were $0.038\ifmmode\pm\else\textpm\fi{}0.008, 0.83\ifmmode\pm\else\textpm\fi{}0.08, 3.8\ifmmode\pm\else\textpm\fi{}0.2$, and $3.0\ifmmode\pm\else\textpm\fi{}0.5$ mb, respectively. Production cross sections for the more neutron-rich targets were surprisingly constant even given the substantial changes in the difference in neutron binding energy and fission barrier of the compound nuclei.Conclusions: Collective enhancements to level density caused a reduction in compound nucleus survivability for all targets. While this effect was required to obtain good agreement between theoretical calculations and experimental data, it was not sufficient to explain the cross sections for the reaction with the most neutron-deficient target studied $(^{154}\mathrm{Gd})$. Instead, it appears that the difference in the fission barrier and neutron binding energy is the dominant factor affecting the survival of the compound nucleus in this case.

The muon and neutral hadron detector of the BaBar experiment for the PEP-II Asymmetric B-factory at SLAC uses Resistive Plate Counters (RPCs) as active detectors. A large fraction of the total system, which consists of approximately 800 chambers for an overall surface of 2000 m2, has already been built and tested in cosmic rays. Preliminary results of the operating characteristics with a new non-flammable and environmentally safe gas mixture are reported.

With the nuclear weapons program moving to Science Based Stockpile Stewardship (SBSS), new diagnostic techniques are needed to replace weapons testing. Proton Radiography is being developed within the SBSS program as one such tool. It is analogous to transmission X-ray radiography, but uses protons instead of photons. Proton Radiography has high penetrating power, high detection efficiency, small-scattered background, inherent multi-pulse capability, and large standoff distances between test objects and detectors. Multiple images on a single axis through progressively smaller angle-cutting apertures can provide material identification. Proton Radiography can make multi-axis, multi-frame radiographs: i.e., 3D radiographic movies. This approach to SBSS is being developed at the Los Alamos National Laboratory (LANL) and the Lawrence Livermore National Laboratory (LLNL). This new method of radiography, as well as radiography experiments performed at the LANSCE accelerator at LANL and at the Alternating Gradient Synchrotron (AGS) at Brookhaven National Laboratory, are discussed.

We study the processes $e^+e^-\to 2(\pi^+\pi^-)\pi^0\pi^0\pi^0\gamma$ and $2(\pi^+\pi^-)\pi^0\pi^0\eta\gamma$ in which an energetic photon is radiated from the initial state. The data were collected with the \babar~ detector at SLAC. About 14\,000 and 4700 events, respectively, are selected from a data sample corresponding to an integrated luminosity of 469 fb^{-1}. The invariant mass of the hadronic final state defines the effective \epem center-of-mass energy. The center-of-mass energies range from threshold to 4.5 GeV. From the mass spectra, the first ever measurements of the $e^+e^-\to 2(\pi^+\pi^-)\pi^0\pi^0\pi^0$ and the $e^+e^-\to2(\pi^+\pi^-)\pi^0\pi^0\eta$ cross sections are performed. The contributions from $\omega\pi^+\pi^-\pi^0\pi^0$, $\eta2(\pi^+\pi^-)$, and other intermediate states are presented. We observe the $J/\psi$ and $\psi(2S)$ in most of these final states and measure the corresponding branching fractions, many of them for the first time.

We present a new technique, ``tau polarimetry,'' for measuring the longitudinal beam polarization present in an ${e}^{+}{e}^{\ensuremath{-}}$ collider through the analysis of ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\tau}}^{+}{\ensuremath{\tau}}^{\ensuremath{-}}$ events. By exploiting the sensitivity of $\ensuremath{\tau}$ decay kinematics to the longitudinal polarization of the beams, we demonstrate that the longitudinal polarization can be measured with a 3 per mil systematic uncertainty at the interaction point using a technique that is independent of spin and beam transport modeling. Using $424.2\ifmmode\pm\else\textpm\fi{}1.8\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of BABAR data at $\sqrt{s}=10.58\text{ }\text{ }\mathrm{GeV}$, the average longitudinal polarization of the PEP-II ${e}^{+}{e}^{\ensuremath{-}}$ collider has been measured to be $⟨P⟩=0.0035\ifmmode\pm\else\textpm\fi{}0.002{4}_{\mathrm{stat}}\ifmmode\pm\else\textpm\fi{}0.002{9}_{\mathrm{sys}}$. The systematic uncertainty studies are described in detail, which can serve as a guide for future applications of tau polarimetry. A proposed ${e}^{\ensuremath{-}}$ beam longitudinal polarization upgrade to the SuperKEKB ${e}^{+}{e}^{\ensuremath{-}}$ collider would benefit from this technique.

A new dark sector antibaryon, denoted ψD, could be produced in decays of B mesons. This Letter presents a search for B+→ψD+p (and the charge conjugate) decays in e+e− annihilations at 10.58 GeV, using data collected in the BABAR experiment. Data corresponding to an integrated luminosity of 398 fb−1 are analyzed. No evidence for a signal is observed. Branching fraction upper limits in the range from 10−7–10−5 are obtained at 90% confidence level for masses of 1.0<mψD<4.3 GeV/c2. The result is also reinterpreted to provide the first limits on a supersymmetric model with R-parity violation and a light neutralino.Received 19 June 2023Accepted 12 October 2023DOI:https://doi.org/10.1103/PhysRevLett.131.201801Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBaryogenesis & leptogenesisParticle dark matterSupersymmetryParticles & Fields

Using the entire BaBar $Υ(4S)$ data set, the first two-dimensional unbinned angular analysis of the semileptonic decay $\overline{B} \rightarrow D \ell^- \overlineν_\ell$ is performed, employing hadronic reconstruction of the tag-side $B$ meson from $Υ(4S)\to B\overline{B}$. Here, $\ell$ denotes the light charged leptons $e$ and $μ$. A novel data-driven signal-background separation procedure with minimal dependence on simulation is developed. This procedure preserves all multi-dimensional correlations present in the data. The expected $\sin^2θ_\ell$ dependence of the differential decay rate in the Standard Model is demonstrated, where $θ_\ell$ is the lepton helicity angle. Including input from the latest lattice QCD calculations and previously available experimental data, the underlying form factors are extracted using both model-independent (BGL) and dependent (CLN) methods. Comparisons with lattice calculations show flavor SU(3) symmetry to be a good approximation in the $B_{(s)}\to D_{(s)}$ sector. Using the BGL results, the CKM matrix element $|V_{cb}|=(41.09\pm 1.16)\times 10^{-3}$ and the Standard Model prediction of the lepton-flavor universality violation variable $\mathcal{R}(D)=0.300\pm 0.004$, are extracted. The value of $|V_{cb}|$ from $\overline{B} \rightarrow D \ell^- \overlineν_\ell$ tends to be higher than that extracted using $\overline{B} \rightarrow D \ell^- \overlineν_\ell$. The Standard Model $\mathcal{R}(D)$ calculation is at a $1.97σ$ tension with the latest HFLAV experimental average.

We describe how protons with energies of 800 MeV or greater can be used as radiographic probes for material characterization. A feature which distinguishes protons from x-rays is their charge, which results in multiple Coulomb scattering effects in proton radiographs. Magnetic lensing can ameliorate these effects and even allow mixed substances to be disentangled. We illustrate some of these effects using 800 MeV protons radiographs of a composite step wedge composed of Aluminum, Foam, and Graphite. We discuss how proton radiographs must be manipulated in order to use standard tomographic reconstruction algorithms. We conclude with a brief description of an upcoming experiment, which will be performed at Brookhaven National Laboratory at 25 GeV.

The point spread function (PSF) of a fully-instrumented silicon/germanium Compton telescope has been measured as a function of energy and angle. Overall, the resolution was 3deg to 4deg FWHM over most of the energy range and field of view. The various contributions to the resolution have been quantified. These contributions include the energy and position uncertainty of the detector; source energy; Doppler broadening; and the 1/r broadening characteristic of Compton back-projection. Furthermore, a distortion of the PSF is observed for sources imaged off-axis from the detector. These contributions are discussed and compared to theory and simulations

We study the processes ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}\ensuremath{\gamma}$ and ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}\ensuremath{\eta}\ensuremath{\gamma}$ in which an energetic photon is radiated from the initial state. The data were collected with the BABAR detector at the SLAC National Accelerator Laboratory. About 7300 and 870 events, respectively, are selected from a data sample corresponding to an integrated luminosity of $469\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$. The invariant mass of the hadronic final state defines the effective ${e}^{+}{e}^{\ensuremath{-}}$ center-of-mass energy. The center-of-mass energies range from threshold to 4.5 GeV. From the mass spectra, the first ever measurements of the ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}$ and the ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}\ensuremath{\eta}$ cross sections are performed. The contributions from $\ensuremath{\omega}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}$, $\ensuremath{\eta}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}$, $\ensuremath{\omega}\ensuremath{\eta}$, and other intermediate states are presented. We observe the $J/\ensuremath{\psi}$ and $\ensuremath{\psi}(2S)$ in most of these final states and measure the corresponding branching fractions, many of them for the first time.

Collider searches for dark sectors, new particles interacting only feebly with ordinary matter, have largely focused on identifying signatures of new mediators, leaving much of dark sector structures unexplored. In particular, the existence of dark matter bound states (darkonia) remains to be investigated. This possibility could arise in a simple model in which a dark photon (${A}^{\ensuremath{'}}$) is light enough to generate an attractive force between dark fermions. We report herein a search for a ${J}^{PC}={1}^{\ensuremath{-}\ensuremath{-}}$ darkonium state, the ${\mathrm{\ensuremath{\Upsilon}}}_{D}$, produced in the reaction ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\ensuremath{\gamma}{\mathrm{\ensuremath{\Upsilon}}}_{D}$, ${\mathrm{\ensuremath{\Upsilon}}}_{D}\ensuremath{\rightarrow}{A}^{\ensuremath{'}}{A}^{\ensuremath{'}}{A}^{\ensuremath{'}}$, where the dark photons subsequently decay into pairs of leptons or pions, using $514\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of data collected with the BABAR detector. No significant signal is observed, and we set bounds on the $\ensuremath{\gamma}\ensuremath{-}{A}^{\ensuremath{'}}$ kinetic mixing as a function of the dark sector coupling constant for $0.001&lt;{m}_{{A}^{\ensuremath{'}}}&lt;3.16\text{ }\text{ }\mathrm{GeV}$ and $0.05&lt;{m}_{{\mathrm{\ensuremath{\Upsilon}}}_{D}}&lt;9.5\text{ }\text{ }\mathrm{GeV}$.

We report on the first search for electron-muon lepton flavor violation (LFV) in the decay of a b quark and b antiquark bound state. We look for the LFV decay ϒ(3S)→e^{±}μ^{∓} in a sample of 118 million ϒ(3S) mesons from 27 fb^{-1} of data collected with the BABAR detector at the SLAC PEP-II e^{+}e^{-} collider operating with a 10.36 GeV center-of-mass energy. No evidence for a signal is found, and we set a limit on the branching fraction B[ϒ(3S)→e^{±}μ^{∓}]<3.6×10^{-7} at 90% C. L. This result can be interpreted as a limit Λ_{NP}/g_{NP}^{2}>80 TeV on the energy scale Λ_{NP} divided by the coupling-squared g_{NP}^{2} of relevant new physics (NP).

We report a Dalitz plot analysis of charmless hadronic decays of charged $B$ mesons to the final state $K_{\rm S}^{0}\pi^{+}\pi^{0}$ using the full BaBar dataset of $470.9\pm2.8$ million $B\bar{B}$ events collected at the $\Upsilon(4S)$ resonance. We measure the overall branching fraction and $CP$ asymmetry to be ${\cal B}\left(B^{+}\to K^{0}\pi^{+}\pi^{0}\right) = \left(45.9 \pm 2.6 \pm 3.0^{+8.6}_{-0.0}\right)\times10^{-6}$ and $A_{CP}\left(B^{+}\to K^{0}\pi^{+}\pi^{0}\right) = 0.07 \pm 0.05 \pm 0.03^{+0.02}_{-0.03}$, where the uncertainties are statistical, systematic, and due to the signal model, respectively. This is the first measurement of the branching fraction for $B^{+} \to K^{0}\pi^{+}\pi^{0}$. We find first evidence of a $CP$ asymmetry in $B^{+}\to K^{*}(892)^{+}\pi^{0}$ decays: $A_{CP}\left(B^{+}\to K^{*}(892)^{+}\pi^{0}\right)=-0.52 \pm 0.14 \pm 0.04^{+0.04}_{-0.02}$. The significance of this asymmetry, including systematic and model uncertainties, is $3.4$ standard deviations. We also measure the branching fractions and $CP$ asymmetries for three other intermediate decay modes.

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.

We have studied how often incoming photons interact via a Compton interaction and/or a photoelectric interaction as a function of energy and detector material Results are using a 1m{sup 3} detector, and discrete energy photons from 0.1 MeV up to 10 MeV. Essentially all of the lower energy photons interact at least once in a detector of this size. This is not the case at higher energies. Each detector, photon energy combination was simulated with 2000 photons.

We study the performance of a large-scale Compton imaging detector placed in a low-flying aircraft, used to search wide areas for rad/nuc threat sources. In this paper we investigate the performance potential of equipping aerial platforms with gamma-ray detectors that have photon sensitivity up to a few MeV. We simulate the detector performance, and present receiver operating characteristics (ROC) curves for a benchmark scenario using a {sup 137}Cs source. The analysis uses a realistic environmental background energy spectrum and includes air attenuation.

We perform simulations of two types of large-scale Compton imaging detectors. The first type uses silicon and germanium detector crystals, and the second type uses silicon and CdZnTe (CZT) detector crystals. The simulations use realistic detector geometry and parameters. We analyze the performance of each type of detector, and we present results using receiver operating characteristics (ROC) curves.

The purpose of this study was to estimate the effect of measurement errors in the position and energy of the observed interactions on the angular resolution of a Compton-ring imaging type detector. In a Compton interaction, if one can measure the energy of the scattered photon and the energy of the Compton electron, then one can determine the scattering angle between the incoming and outgoing photon using the well-known Compton formula.

The purpose of this study was to estimate the intrinsic physics limitations on the angular and energy resolution of electron-tracking type gamma-ray detectors. In a Compton interaction, one can completely determine the direction and energy of the incoming gamma ray, without measuring the scattered photon's energy, if one can measure the direction and energy of the scattered electron, and the direction of the scattered photon. Multiple scattering of the Compton electron will quickly destroy the information of the electron's initial direction, so practical devices must be able to resolve the original electron direction, i.e., have tracking resolution mucic h smaller than the typical radiation length in the material.

This paper describes the derivation of analytic expressions for the angular resolution of reconstructing gamma rays detected via Compton interactions. We consider two types of gamma-ray detectors: Compton-ring and electron-tracking devices. In Compton-ring devices, the direction of the scattered electron is not resolved, only the total energy (electron and scattered photon) and the scattered photon direction are measured. The measured quantities define a cone about the axis of the scattered photon direction. The initial photon direction lies along this cone. Thus for single events there is a ring-like ambiguity in the photon direction. By combining multiple events, the intersection of the reconstructed rings will resolve the initial direction of the photon source. In this paper, we derive the resolution of the cone angle for individual rings. Electron-tracking type devices resolve the electron path. Although the scattered electron subsequently undergoes multiple-Coulomb scattering, it is possible to measure the initial electron direction with sufficiently high tracking resolution. By measuring the direction and energy of the electron and the direction of the scattered photon, the initial photon direction can be uniquely determined. The challenge for this type of detector is achieving the high tracking resolution. In Section 2 we derive the well-known Compton formula for Compton-ring devices, an analytic expression for the angular resolution of the cone angle, and discuss the limits for applying the error formula. In Section 3 we repeat the derivation of the error function for the algebraically more complicated electron-tracking device. In the final section (Section 4) we derive the effect of position measurement error on the angular resolution, which applies to both detector types. All of the analytic results are cross-checked against empirical fits to a simple Monte Carlo simulation. Doppler broadening, the effect due to the initial (and intrinsically unknown) momentum of the atomic electron, can be ignored for gamma rays with initial energy greater than a few hundred keV. For all kinematic calculations in this paper, the electron is taken to be initially at rest.

We present updated results on time-dependent CP-violating asymmetries in neutral B decays to several CP eigenstates containing charmonium. In the Standard Model, the amplitude of these asymmetries is proportional to sin2β. We measure sin2β = 0.741 ± 0.067 (stat) ± 0.034 (syst) from a data sample of about 88 million γ(4S) → BB decays collected with the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. We have also measured CP-violating asymmetries in open charm, and penguin modes sensitive to sin2β, which provide important consistency tests of the Standard Model.

&lt;p&gt;The resulting thesis asks, ‘how can architecture curate our experience of site to facilitate placemaking’. It finds that architecture can create distinctive and diverse ‘places’ in large landscapes by enabling new ways for people to engage with the site. These places result in a deeply felt experience and, when positioned in a series, they highlight the significance of the landscape. The thesis examines a significant route within the Tararua Forest Park known as the Southern Crossing. The thesis explores how architecture can curate this experience to better connect us to place. This is facilitated by a series of nine architectural interventions that test and refine methods for situating, orientating, temporalising and contextualising one’s experience of space. Starting with site analysis, the thesis finds that subjectivity can provide deeper insights and more powerful concepts when related to experience. It finds that narrative methodologies enable the study of actuality and this is accompanied with the ability to interpret spatial elements which affect this experience. This is opposed to contemporary approaches which are focused on objectivity and fact. Through evolving narrative techniques, a way for the architecture to curate one’s experience of each site is discovered. The design methodology does away with contemporary abstract views. Instead, the process focuses on understanding how the architectonic elements influence the spatial experience to better connect us to place.&lt;/p&gt;

&lt;p&gt;The resulting thesis asks, ‘how can architecture curate our experience of site to facilitate placemaking’. It finds that architecture can create distinctive and diverse ‘places’ in large landscapes by enabling new ways for people to engage with the site. These places result in a deeply felt experience and, when positioned in a series, they highlight the significance of the landscape. The thesis examines a significant route within the Tararua Forest Park known as the Southern Crossing. The thesis explores how architecture can curate this experience to better connect us to place. This is facilitated by a series of nine architectural interventions that test and refine methods for situating, orientating, temporalising and contextualising one’s experience of space. Starting with site analysis, the thesis finds that subjectivity can provide deeper insights and more powerful concepts when related to experience. It finds that narrative methodologies enable the study of actuality and this is accompanied with the ability to interpret spatial elements which affect this experience. This is opposed to contemporary approaches which are focused on objectivity and fact. Through evolving narrative techniques, a way for the architecture to curate one’s experience of each site is discovered. The design methodology does away with contemporary abstract views. Instead, the process focuses on understanding how the architectonic elements influence the spatial experience to better connect us to place.&lt;/p&gt;

After investigating a number of materials, we discovered that an ABS plastic doped with a conducting polymer performs well as the resistive electrode in a narrow gap RPC (resistive plate chamber). Operating in the streamer mode, we find efficiencies of 90-96% with low noise and low strip multiplicities. We have also studied a variety of operating gases and found that a mixture containing SF{sub 6}, a non-ozone depleting gas, argon and isobutane gives good streamer mode performance, even with isobutane concentrations of 20% or less.