Physics Commons^™

Study Of The Reactions E+E-→Π+Π-Π0Π0Π0 And Π+Π-Π0Π0Η At Center-Of-Mass Energies From Threshold To 4.35 Gev Using Initial-State Radiation, J. P. Lees, V. Poireau, V. Tisserand, E. Grauges, A. Palano, G. Eigen, D. N. Brown, Yu G. Kolomensky, M. Fritsch, H. Koch, T. Schroeder, C. Hearty, T. S. Mattison, J. A. Mckenna, R. Y. So, V. E. Blinov, A. R. Buzykaev, V. P. Druzhinin, V. B. Golubev, E. A. Kozyrev, Milind Purohit, Et. Al.

Faculty Publications

We study the processes e⁺e⁻ → π⁺π⁻π⁰π⁰π⁰nγ in which an energetic photon is radiated from the initial state. The data are 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 e⁺e⁻ center-of-mass energy. From the mass spectra, the first precise measurement of the e⁺e⁻ → π⁺π^{− …}

Measurement Of The Branching Fraction And Time-Dependent Cp Asymmetry For B0→J/Ψπ0 Decays, B. Pal, A.J. Schwartz, H. Aihara, S. Al Said, D. M. Asner, H. Atmacan, V. Aulchenko, T. Aushev, R. Ayad, I. Badhrees, S. Bahinipati, V. Bansal, P. Behera, C. Beleño, B. Bhuyan, T. Bilka, J. Biswal, A. Bozek, M. Bračko, L. Cao, Milind Purohit, Et. Al.

Faculty Publications

We measure the branching fraction and time-dependent CP-violating asymmetry for B0 → J=ψπ0 decays using a data sample of 711 fb⁻¹ collected on the ϒ(4S) resonance by the Belle experiment running at the KEKB e⁺e⁻ collider. The branching fraction is measured to be B(B⁰ → J/_ψπ⁰) ¼ [1.62 ± 0.11(stat) ± 0.06(syst) × 10⁻⁵, which is the most precise measurement to date. The measured CP asymmetry parameters are S =−0.59 ±0.19(stat) 0.03(syst) and A = −0.15 ± 0.14(stat) ^+0.04 _−0.03 (syst). The mixing-induced CP asymmetry (S) differs …

Interactions Between Disciplinary Practices And Joint Work In Undergraduate Physics Research Experiences, Gina Quan, Chandra Turpen, Andrew Elby

Faculty Publications

We analyze how participating in undergraduate research experiences (UREs) influenced physics students’ trajectories of participation within the community of practice of physics researchers. Students in the study participated in an elective seminar in which they were paired with graduate student and faculty mentors on physics research projects and participated in weekly discussions about research. Using video data from student interviews and mentor interviews, we characterize two aspects of students’ engagement in the physics community of practice. First, we find variations in their engagement in physics practice, which we characterize as physics activities that are connected and purposeful. Second, we characterize …

Measurement Of The Γ*Γ* → Η' Transition Form Factor, J.P. Lees, V. Poireau, V. Tisserand, E. Grauges, A. Palano, G. Eigen, D. N. Brown, Yu G. Kolomensky, M. Fritsch, H. Koch, T. Schroeder, C. Hearty, T. S. Mattison, J. A. Mckenna, R. Y. So, V. E. Blinov, A. R. Buzykaev, V. P. Druzhinin, V. B. Golubev, Milind Purohit, Et. Al.

Faculty Publications

We study the process e⁺e⁻→e⁺e⁻η′ in the double-tag mode and measure for the first time the γ^*γ^*→ η′ transition form factor Fη′ (Q ² ₁ , Q² ₂) in the momentum-transfer range 2< Q ² ₁ , Q² ₂ 60 GeV ² . The analysis is based on a data sample corresponding to an integrated luminosity of around 469     fb^{− 1} collected at the PEP-II e ⁺e ⁻ collider with the BABAR detector at center-of-mass energies near 10.6 GeV.

1; Q2 2Þ in the …

Estimation Of Atmospheric Turbulence Using Differential Motion Of Extended Features In Time-Lapse Imagery, Santasri Bose-Pillai, Jack E. Mccrae, Christopher A. Rice, Ryan A. Wood, Conner E. Murphy, Steven T. Fiorino

Faculty Publications

We address the design, development, and testing of a pointer/tracker as a probe beam for the purpose of making high-speed, aero-optical measurements of the flow over a scaled beam director turret. The tracker uses retro-reflection of the probe beam off of a Reflexite annulus surrounding the turret. The constraints of the design required a near-total-commercial off the shelf system that could be quickly installed and removed in a rented aircraft. Baseline measurements of environmental vibrations are used to predict pointing performance; mitigation of line-of-sight jitter on the probe beam is achieved through passive isolation and the design of relay optics. …

Search For The Lepton-Flavour Violating Decays B0→K∗0Μ ± E ∓, S. Sandilya, K. Trabelsi, A.J. Schwartz, I. Adachi, H. Aihara, S. Al Said, D. M. Asner, H. Atmacan, V. Aulchenko, T. Aushev, R. Ayad, V. Babu, I. Badhrees, S. Bahinipati, A. M. Bakich, V. Bansal, P. Behera, C. Beleño, V. Bhardwaj, B. Bhuyan, Milind Purohit, Et. Al.

Faculty Publications

We have searched for the lepton-flavor-violating decay B⁰ → K^*0μ ^±e∓ using a data sample of 711 fb⁻¹ that contains 772 × 10⁶ B B̅ pairs. The data were collected near the ϒð4SÞresonance with the Belle detector at the KEKB asymmetric-energy eþe− collider. No signals were observed, and we set 90% confidence level upper limits on the branching fractions of B(B⁰ →K^*0μ⁺e⁻)<1.2×10⁻⁷, B(B⁰ → K^*0μ⁻e⁺) < 1.6 × 10⁻⁷, and, for both decays combined, B(B⁰ → K …

Linear Least Squares Curve Fitting, R. Steven Turley

Faculty Publications

This article is a review of the theory and practice behind linear least squares curve fitting. It outlines how to find the optimal parameters to match experimental data with theory and how to estimate the uncertainty in those parameters. The article demonstrates and validates these calculations in Excel, MATLAB, Mathematica, Python, and Julia.

Cubic Interpolation With Irregularly-Spaced Points In Julia 1.4, R. Steven Turley

Faculty Publications

This article shows how to interpolate between regularly- or irregularly-spaced points in Julia 1.4. It has derivations of the theory behind cubic splines, and piece-wise cubic hermite polynomial interpolation. The spline interpolants are continuous and have continuous first and second derivatives. The hermite polynomial interpolants are continuous and have continuous first derivatives. Three techniques are implemented to determine the slope at the data points for the interpolation (knots). One uses the average slope of the neighboring segments. Another use the quadratic polynomial passing through the point and its two neighbors. The third, PCHIP, is similar to the first method, but …

Measurement Of The Spectral Function For The Τ− → K−KSΝΤ Decay, J.P. Lees, V. Porieau, V. Tisserand, E. Grauges, A. Palano, G. Eigen, D. N. Brown, Yu G. Kolomensky, M. Fritsch, H. Koch, T. Schroeder, C. Hearty, T. S. Mattison, J. A. Mckenna, R. Y. So, V. E. Blinov, A. R. Buzykaev, V. P. Druzhinin, V. B. Golubev, Milind Purohit, Et. Al.

Faculty Publications

The decay τ−→K−KSντ has been studied using 430 × 10⁶ e+e− → _τ⁺_τ⁻ 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−K_S system has been measured and the spectral function has been obtained. The measured branching fraction B(_τ− → K−K_{Sντ) =}(0.739 ± 0.011(stat) ± 0.020(syst)) × 10⁻³ is found to be in agreement with earlier measurements.

The Multimodal Interactional Work Of Having Wonderful Ideas, Benedikt Harrer

Faculty Publications

Learning physics is socially organized through interactions with peers and more competent others. Instructors' and peers' assessment of and responsiveness to learners' ideas in the moment is critical for the collaborative construction of knowledge in physics. However, we still know little about how instructors and learners negotiate the value and productiveness of ideas. While to an outsider, some of the ideas physics learners discuss do not seem immediately valuable or productive for the problem being solved, Duckworth encourages us to pursue an 'insider's view' on how a learner experiences their ideas. Building on Duckworth, I pursue an 'insider's view' to …

Pondering Zeros: Uncovering Hidden Inequities Within A Decade Of Grades, Cassandra Paul

Faculty Publications

When assessing student work, graders will often find that some students will leave one or more problems blank on assessments. Since there is no work shown, the grader has no means to evaluate the student's understanding of a particular problem, and thus awards zero points. This practice punishes the student behavior of leaving a problem blank, but this zero is not necessarily an accurate assessment of student understanding of a particular topic. While some might argue that this grading practice is "fair" in that students know that they can't receive points for answers they don't submit, we share evidence that …

Fluctuating Hydrodynamics Of Reactive Liquid Mixtures, Changho Kim, Andy. Nonaka, John Bell, Alejandro Garcia, Aleksandar Donev

Faculty Publications

Fluctuating hydrodynamics (FHD) provides a framework for modeling microscopic fluctuations in a manner consistent with statistical mechanics and nonequilibrium thermodynamics. This paper presents an FHD formulation for isothermal reactive incompressible liquid mixtures with stochastic chemistry. Fluctuating multispecies mass diffusion is formulated using a Maxwell–Stefan description without assuming a dilute solution, and momentum dynamics is described by a stochastic Navier–Stokes equation for the fluid velocity. We consider a thermodynamically consistent generalization for the law of mass action for non-dilute mixtures and use it in the chemical master equation (CME) to model reactions as a Poisson process. The FHD approach provides remarkable …

Large And Realistic Models Of Amorphous Silicon, Dale Ingram, Bishal Bhattarai, Parthapratim Biswas, David A. Drabold

Faculty Publications

Amorphous silicon (a-Si) models are analyzed for structural, electronic and vibrational characteristics. Several models of various sizes have been computationally fabricated for this analysis. It is shown that a recently developed structural modeling algorithm known as force-enhanced atomic refinement (FEAR) provides results in agreement with experimental neutron and X-ray diffraction data while producing a total energy below conventional schemes. We also show that a large model (∼ 500 atoms) and a complete basis is necessary to properly describe vibrational and thermal properties. We compute the density for a-Si, and compare with experimental results.

Arrhenius Rate Chemistry-Informed Inter-Phase Source Terms (Arciist), Matthew J. Schwaab, Robert B. Greendyke, Bryan J. Steward

Faculty Publications

Currently, in macro-scale hydrocodes designed to simulate explosive material undergoing shock-induced ignition, the state of the art is to use one of numerous reaction burn rate models. These burn models are designed to estimate the bulk chemical reaction rate. Unfortunately, these burn rate models are largely based on empirical data and must be recalibrated for every new material being simulated. We propose that the use of Arrhenius Rate Chemistry-Informed Interphase Source Terms (ARCIIST) in place of empirically derived burn models will improve the accuracy for these computational codes. A reacting chemistry model of this form was developed for the cyclic …

Enabling Autonomous Navigation For Affordable Scooters, Kaikai Liu, Rajathswaroop Mulky

Faculty Publications

Despite the technical success of existing assistive technologies, for example, electric wheelchairs and scooters, they are still far from effective enough in helping those in need navigate to their destinations in a hassle-free manner. In this paper, we propose to improve the safety and autonomy of navigation by designing a cutting-edge autonomous scooter, thus allowing people with mobility challenges to ambulate independently and safely in possibly unfamiliar surroundings. We focus on indoor navigation scenarios for the autonomous scooter where the current location, maps, and nearby obstacles are unknown. To achieve semi-LiDAR functionality, we leverage the gyros-based pose data to compensate …

Improved Space Object Detection Using Short-Exposure Image Data With Daylight Background, David J. Becker, Stephen C. Cain

Faculty Publications

No abstract provided.

Out-Of-Plane Electron Transport In Finite Layer Mos2, R Holzapfel, Jake Weber, Pavel Lukashev, Andrew Stollenwerk

Faculty Publications

Ballistic electron emission microscopy (BEEM) has been used to study the processes affecting electron transport along the [0001] direction of finite layer MoS2 flakes deposited onto the surface of Au/Si(001) Schottky diodes. Prominent features present in the differential spectra from the MoS2 flakes are consistent with the density of states of finite layer MoS2 calculated using density functional theory. The ability to observe the electronic structure of the MoS2 appears to be due to the relatively smooth density of states of Si in this energy range and a substantial amount of elastic or quasi-elastic scattering along the MoS2/Au/Si(001) path. Demonstration …

Magnetic And Magnetocaloric Properties Of Co2-Xfexvga Heusler Alloys, K. Schroeder, J. Waybright, P. Kharel, W. Zhang, S. Valloppilly, J. Herran, P. Lukashev, Y. Huh, R. Skomsk, D. J. Sellmyer

Faculty Publications

The magnetic and magnetocaloric properties of iron-substituted Co₂VGa alloys, Co_2-xFe_xVGa (x = 0, 0.1, 0.15, 0.2, 0.3), were investigated. The Fe-substituted samples, prepared by arc melting, melt spinning, and annealing, crystallized in the L2(1) Heusler structure, without any secondary phases. The Curie temperature and high-field magnetization at 50 K decreased from 345 K and 44 emu/g (1.90 mu(B)/f.u.) for Co₂VGa to 275 K and 39 emu/g (1.66 mu(B)/f.u.) for Co_1.7Fe_0.3VGa, respectively, but the maximum entropy change remained almost insensitive to Fe concentration for x 1.85Fe_0.15VGa. First-principle …

Hadronic Lorentz Violation In Chiral Perturbation Theory Including The Coupling To External Fields, Rasha Kamand, Brett Altschul, Matthias R. Schindler

Faculty Publications

If any violation of Lorentz symmetry exists in the hadron sector, its ultimate origins must lie at the quark level. We continue the analysis of how the theories at these two levels are connected, using chiral perturbation theory. Considering a 2-flavor quark theory, with dimension-4 operators that break Lorentz symmetry, we derive a low-energy theory of pions and nucleons that is invariant under local chiral transformations and includes the coupling to external fields. The pure meson and baryon sectors, as well as the couplings between them and the couplings to external electromagnetic and weak gauge fields, contain forms of Lorentz …

Hadronic Lorentz Violation In Chiral Perturbation Theory Including The Coupling To External Fields, Rasha Kamand, Brett David Altschul, Matthias R. Schindler

Faculty Publications

If any violation of Lorentz symmetry exists in the hadron sector, its ultimate origins must lie at the quark level. We continue the analysis of how the theories at these two levels are connected, using chiral perturbation theory. Considering a 2-flavor quark theory, with dimension-4 operators that break Lorentz symmetry, we derive a low-energy theory of pions and nucleons that is invariant under local chiral transformations and includes the coupling to external fields. The pure meson and baryon sectors, as well as the couplings between them and the couplings to external electromagnetic and weak gauge fields, contain forms of Lorentz …

Fitting Als Reflectance Data Using Python, R. Steven Turley

Faculty Publications

This article describes how to use the python refl library in https://bitbucket.org/steve_turley/reflectance-fitting to fit thin film reflectance data from the Advanced Light Source (ALS) at Lawrence Berkeley National Labs. It uses data taken for a thin film of aluminum capped by a thin film of aluminum fluoride on a silicon nitride substrate. The single fit in the example shown here shows the importance of taking into account the oxidation of the aluminum layer as part of the fit.

Unconventional Pairing Symmetry Of Interacting Dirac Fermions On A Π -Flux Lattice, Huaiming Guo, Ehsan Khatami, Yao Wang, Thomas Devereaux, Rajiv Singh, Richard Scalettar

Faculty Publications

The pairing symmetry of interacting Dirac fermions on the π-flux lattice is studied with the determinant quantum Monte Carlo and numerical linked-cluster expansion methods. The s∗- (i.e., extended s-) and d-wave pairing symmetries, which are distinct in the conventional square lattice, are degenerate under the Landau gauge. We demonstrate that the dominant pairing channel at strong interactions is an unconventional ds∗-wave phase consisting of alternating stripes of s∗- and d-wave phases. A complementary mean-field analysis shows that while the s∗- and d-wave symmetries individually have nodes in the energy spectrum, the ds∗ channel is fully gapped. The results represent a …

Strange And Non-Strange Distributions From The Collider Data, Sergey Alekhin, Johannes Blümlein, Sergey Kulagin, Sven-Olaf Moch, Roberto Petti

Faculty Publications

We check the stability of the ABMP16 fit with respect to modifications of quark PDFs suggested in the recent literature: the strange sea enhancement and a positive non-vanishing d/u ratio at x → 1. These possibilities are examined using test versions of the ABMP16 PDF fit which demonstrate no need of those changes. Furthermore, we localize peculiar features in other analyses which are responsible for a different behaviour of the PDFs obtained. The strange sea enhancement can be explained by a choice of the PDF shapes being not flexible enough and therefore leading to an over-suppressed d-quark distribution. This …

Reference Dependence Of The Two-Determinant Coupled-Cluster Method For Triplet And Open-Shell Singlet States Of Biradical Molecules, Jesse J. Lutz, Marcel Nooijen, Ajith Perera, Rodney J. Bartlett

Faculty Publications

We study the performance of the two-determinant (TD) coupled-cluster (CC) method which, unlike conventional ground-state single-reference (SR) CC methods, can, in principle, provide a naturally spin-adapted treatment of the lowest-lying open-shell singlet (OSS) and triplet electronic states. Various choices for the TD-CC reference orbitals are considered, including those generated by the multi-configurational self-consistent field method. Comparisons are made with the results of high-level SR-CC, equation-of-motion (EOM) CC, and multi-reference EOM calculations performed on a large test set of over 100 molecules with low-lying OSS states. It is shown that in cases where the EOMCC reference function is poorly described, TD-CC …

Mode Analysis For Energetics Of A Moving Charge In Lorentz- And Cpt-Violating Electrodynamics, Richard Decosta, Brett David Altschul

Faculty Publications

In isotropic but Lorentz- and CPT-violating electrodynamics, it is known that a charge in uniform motion does not lose any energy to Cerenkov radiation. This presents a puzzle, since the radiation appears to be kinematically allowed for many modes. Studying the Fourier transforms of the most important terms in the modified magnetic field and Poynting vector, we confirm the vanishing of the radiation rate. Moreover, we show that the Fourier transform of the field changes sign between small and large wave numbers. This enables modes with very long wavelengths to carry negative energies, which cancel out the positive energies carried …

Comparison Of Plume Dynamics For Laser Ablated Metals: Al And Ti, William A. Bauer, Glen P. Perram, Timothy Haugan

Faculty Publications

Emissive plumes from pulsed laser ablation of bulk Ti and Al from KrF laser irradiation at laser fluence up to 3.5 J/cm² and argon background pressures of 0–1 Torr have been observed using gated intensified charged-coupled device imagery. Mass loss for Ti increases from 0.1 to 0.8 μg/pulse as pulse energy increase from 174 to 282 mJ/pulse (35–170 photons/atom) and decreases by ∼30% as pressure increases from vacuum to 1 Torr. Early plume energies are described by the free expansion velocities of 1.57 ± 0.02 and of 1.81 ± 0.07 cm/μs for Ti and Al, respectively, …

Demonstration Of Versatile Whispering-Gallery Micro-Lasers For Remote Refractive Index Sensing, Lei Wan, Hengky Chandrahalim, Jian Zhou

Faculty Publications

We developed chip-scale remote refractive index sensors based on Rhodamine 6G (R6G)-doped polymer micro-ring lasers. The chemical, temperature, and mechanical sturdiness of the fused-silica host guaranteed a flexible deployment of dye-doped polymers for refractive index sensing. The introduction of the dye as gain medium demonstrated the feasibility of remote sensing based on the free-space optics measurement setup. Compared to the R6G-doped TZ-001, the lasing behavior of R6G-doped SU-8 polymer micro-ring laser under an aqueous environment had a narrower spectrum linewidth, producing the minimum detectable refractive index change of 4 x 10⁻⁴ RIU. The maximum bulk refractive index sensitivity (BRIS) …

Influence Of Basis-Set Size On The X2Σ+1/2, A2Π1/2, A2Π3/2, And B2Σ1/2 Potential-Energy Curves, A2Π3/2 2 Vibrational Energies, And D1 And D2 Line Shapes Of Rb+He, L. Aaron Blank, Amit R. Sharma, David E. Weeks

Faculty Publications

The X 2 Σ + 1 / 2 , A 2 Π 1 / 2 , A 2 Π 3 / 2 , and B 2 Σ + 1 / 2 potential-energy curves for Rb+He are computed at the spin-orbit multireference configuration interaction level of theory using a hierarchy of Gaussian basis sets at the double-zeta (DZ), triple-zeta (TZ), and quadruple-zeta (QZ) levels of valence quality. Counterpoise and Davidson-Silver corrections are employed to remove basis-set superposition error and ameliorate size-consistency error. An extrapolation is performed to obtain a final set of potential-energy curves in the complete basis-set (CBS) limit. This …

Mode Analysis For Energetics Of A Moving Charge In Lorentz- And Cpt -Violating Electrodynamics, Richard Decosta, Brett Altschul

Faculty Publications

In isotropic but Lorentz- and CPT -violating electrodynamics, it is known that a charge in uniform motion does not lose any energy to Cerenkov radiation. This presents a puzzle, since the radiation appears to be kinematically allowed for many modes. Studying the Fourier transforms of the most important terms in the modified magnetic field and Poynting vector, we confirm the vanishing of the radiation rate. Moreover, we show that the Fourier transform of the field changes sign between small and large wave numbers. This enables modes with very long wavelengths to carry negative energies, which cancel out the positive energies …

Monte Carlo Simulations Of Three-Dimensional Electromagnetic Gaussian Schell-Model Sources, Milo W. Hyde Iv, Santasri Bose-Pillai, Olga Korotkova

Faculty Publications

This article presents a method to simulate a three-dimensional (3D) electromagnetic Gaussian-Schell model (EGSM) source with desired characteristics. Using the complex screen method, originally developed for the synthesis of two-dimensional stochastic electromagnetic fields, a set of equations is derived which relate the desired 3D source characteristics to those of the statistics of the random complex screen. From these equations and the 3D EGSM source realizability conditions, a single criterion is derived, which when satisfied guarantees both the realizability and simulatability of the desired 3D EGSM source. Lastly, a 3D EGSM source, with specified properties, is simulated; the Monte Carlo simulation …