About
Lu Zhang is an Assistant Professor of Computational Applied Mathematics and Operations Research at Rice University, having joined the department in 2023. She previously held the position of Ju Tang Chu and Wu Ping Chu Assistant Professor in the Department of Applied Physics and Applied Mathematics at Columbia University. She earned her Ph.D. in computational and applied mathematics from Southern Methodist University in 2020, where she also worked as a graduate student. Her research interests focus on the numerical and theoretical analysis of partial differential equations (PDEs) and applied mathematics. She specializes in developing high-order discontinuous Galerkin methods to study various PDEs with physical and biological backgrounds, including advective wave equations, seismic imaging problems, chemotaxis models, and population dynamics models. Her work addresses the challenges posed by the structural complexity and computational intensity of these systems, aiming to create high-order, computationally efficient, and energy-stable numerical methods. Additionally, she develops efficient and robust algorithms for inverse problems, contributing to the understanding of the spatio-temporal dynamics of phenomena in the physical and biological sciences.
Research topics
- Particle physics
- Nuclear physics
- Physics
- Quantum mechanics
- Astrophysics
- Mechanical engineering
- Optics
- Economics
- Geography
- Engineering
Selected publications
Differential cross section measurements for the production of top quark pairs and of additional jets using dilepton events from pp collisions at $$ \sqrt{s} $$ = 13 TeV
OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information) · 2025 · 8 citations
- Physics
- Particle physics
- Nuclear physics
A bstract Differential cross sections for top quark pair ( $$ \textrm{t}\overline{\textrm{t}} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>t</mml:mi> <mml:mover> <mml:mi>t</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> </mml:math> ) production are measured in proton-proton collisions at a center-of-mass energy of 13 TeV using a sample of events containing two oppositely charged leptons. The data were recorded with the CMS detector at the CERN Large Hadron Collider and correspond to an integrated luminosity of 138 fb − 1 . The differential cross sections are measured as functions of kinematic observables of the $$ \textrm{t}\overline{\textrm{t}} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>t</mml:mi> <mml:mover> <mml:mi>t</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> </mml:math> system, the top quark and antiquark and their decay products, as well as of the number of additional jets in the event. The results are presented as functions of up to three variables and are corrected to the parton and particle levels. When compared to standard model predictions based on quantum chromodynamics at different levels of accuracy, it is found that the calculations do not always describe the observed data. The deviations are found to be largest for the multi-differential cross sections.
HAL (Le Centre pour la Communication Scientifique Directe) · 2023 · 7 citations
- Physics
- Particle physics
- Nuclear physics
A data sample containing top quark pairs ($t\overline{t}$) produced in association with a Lorentz-boosted $Z$ or Higgs boson is used to search for signs of new physics using effective field theory. The data correspond to an integrated luminosity of $138\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of proton-proton collisions produced at a center-of-mass energy of 13 TeV at the LHC and collected by the CMS experiment. Selected events contain a single lepton and hadronic jets, including two identified with the decay of bottom quarks, plus an additional large-radius jet with high transverse momentum identified as a $Z$ or Higgs boson decaying to a bottom quark pair. Machine learning techniques are employed to discriminate between $t\overline{t}Z$ or $t\overline{t}H$ events and events from background processes, which are dominated by $t\overline{t}+\text{jets}$ production. No indications of new physics are observed. The signal strengths of boosted $t\overline{t}Z$ and $t\overline{t}H$ production are measured, and upper limits are placed on the $t\overline{t}Z$ and $t\overline{t}H$ differential cross sections as functions of the $Z$ or Higgs boson transverse momentum. The effects of new physics are probed using a framework in which the standard model is considered to be the low-energy effective field theory of a higher energy scale theory. Eight possible dimension-six operators are added to the standard model Lagrangian, and their corresponding coefficients are constrained via fits to the data.
Test of lepton universality in beauty-quark decays
Nature Physics · 2022 · 367 citations
- Physics
- Particle physics
- Nuclear physics
Abstract The standard model of particle physics currently provides our best description of fundamental particles and their interactions. The theory predicts that the different charged leptons, the electron, muon and tau, have identical electroweak interaction strengths. Previous measurements have shown that a wide range of particle decays are consistent with this principle of lepton universality. This article presents evidence for the breaking of lepton universality in beauty-quark decays, with a significance of 3.1 standard deviations, based on proton–proton collision data collected with the LHCb detector at CERN’s Large Hadron Collider. The measurements are of processes in which a beauty meson transforms into a strange meson with the emission of either an electron and a positron, or a muon and an antimuon. If confirmed by future measurements, this violation of lepton universality would imply physics beyond the standard model, such as a new fundamental interaction between quarks and leptons.
arXiv (Cornell University) · 2022 · 2 citations
- Physics
- Particle physics
- Nuclear physics
The first search is presented for vector-like leptons (VLLs) in the context of the '4321 model', an ultraviolet-complete model with the potential to explain existing B physics measurements that are in tension with standard model predictions. The analyzed data, corresponding to an integrated luminosity of 96.5 fb$^{-1}$, were recorded in 2017 and 2018 with the CMS detector at the LHC in proton-proton collisions at $\sqrt{s}$ =13 TeV. Final states with ${\geq}$3 b-tagged jets and two third-generation leptons ($\tau\tau$, $\tau\nu_\tau$, or $\nu_\tau\nu_\tau$) are considered. Upper limits are derived on the VLL production cross section in the VLL mass range 500-1050 GeV. The maximum likelihood fit prefers the presence of signal at the level of 2.8 standard deviations, for a representative VLL mass point of 600 GeV. As a consequence, the observed upper limits are approximately double the expected limits.
Identification of hadronic tau lepton decays using a deep neural network
Journal of Instrumentation · 2022 · 51 citations
- Physics
- Particle physics
- Nuclear physics
A new algorithm is presented to discriminate reconstructed hadronic decays of tau leptons (τ h) that originate from genuine tau leptons in the CMS detector against τ h candidates that originate from quark or gluon jets, electrons, or muons. The algorithm inputs information from all reconstructed particles in the vicinity of a τ h candidate and employs a deep neural network with convolutional layers to efficiently process the inputs. This algorithm leads to a significantly improved performance compared with the previously used one. For example, the efficiency for a genuine τ h to pass the discriminator against jets increases by 10-30% for a given efficiency for quark and gluon jets. Furthermore, a more efficient τ h reconstruction is introduced that incorporates additional hadronic decay modes. The superior performance of the new algorithm to discriminate against jets, electrons, and muons and the improved τ h reconstruction method are validated with LHC proton-proton collision data at s = 13 TeV.
Measurement of the Higgs boson width and evidence of its off-shell contributions to ZZ production
HAL (Le Centre pour la Communication Scientifique Directe) · 2022 · 5 citations
- Physics
- Particle physics
- Nuclear physics
Since the discovery of the Higgs boson in 2012, detailed studies of its properties have been ongoing. Besides its mass, its width - related to its lifetime - is an important parameter. One way to determine this quantity is by measuring its off-shell production, where the Higgs boson mass is far away from its nominal value, and relating it to its on-shell production, where the mass is close to the nominal value. Here, we report evidence for such off-shell contributions to the production cross section of two Z bosons with data from the CMS experiment at the CERN Large Hadron Collider. We constrain the total rate of the off-shell Higgs boson contribution beyond the Z boson pair production threshold, relative to its standard model expectation, to the interval [0.0061, 2.0] at 95% confidence level. The scenario with no off-shell contribution is excluded at a $p$-value of 0.0003 (3.6 standard deviations). We measure the width of the Higgs boson as $\Gamma_{\mathrm{H}}$ = 3.2 $_{-1.7}^{+2.4}$ MeV, in agreement with the standard model expectation of 4.1 MeV. In addition, we set constraints on anomalous Higgs boson couplings to W and Z boson pairs.
Journal of High Energy Physics · 2022 · 36 citations
- Physics
- Particle physics
- Nuclear physics
A bstract The first measurement of the CP structure of the Yukawa coupling between the Higgs boson and τ leptons is presented. The measurement is based on data collected in proton-proton collisions at $$ \sqrt{s} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> </mml:math> = 13 TeV by the CMS detector at the LHC, corresponding to an integrated luminosity of 137 fb − 1 . The analysis uses the angular correlation between the decay planes of τ leptons produced in Higgs boson decays. The effective mixing angle between CP -even and CP -odd τ Yukawa couplings is found to be − 1 ± 19°, compared to an expected value of 0 ± 21° at the 68.3% confidence level. The data disfavour the pure CP -odd scenario at 3.0 standard deviations. The results are compatible with predictions for the standard model Higgs boson.
A portrait of the Higgs boson by the CMS experiment ten years after the discovery
Nature · 2022 · 320 citations
- Physics
- Particle physics
- Nuclear physics
In July 2012, the ATLAS and CMS collaborations at the CERN Large Hadron Collider announced the observation of a Higgs boson at a mass of around 125 gigaelectronvolts. Ten years later, and with the data corresponding to the production of a 30-times larger number of Higgs bosons, we have learnt much more about the properties of the Higgs boson. The CMS experiment has observed the Higgs boson in numerous fermionic and bosonic decay channels, established its spin-parity quantum numbers, determined its mass and measured its production cross-sections in various modes. Here the CMS Collaboration reports the most up-to-date combination of results on the properties of the Higgs boson, including the most stringent limit on the cross-section for the production of a pair of Higgs bosons, on the basis of data from proton-proton collisions at a centre-of-mass energy of 13 teraelectronvolts. Within the uncertainties, all these observations are compatible with the predictions of the standard model of elementary particle physics. Much evidence points to the fact that the standard model is a low-energy approximation of a more comprehensive theory. Several of the standard model issues originate in the sector of Higgs boson physics. An order of magnitude larger number of Higgs bosons, expected to be examined over the next 15 years, will help deepen our understanding of this crucial sector.
Physical review. D/Physical review. D. · 2020 · 476 citations
- Physics
- Particle physics
- Nuclear physics
Combined measurements of Higgs boson production and decay using up to 80
Journal of High Energy Physics · 2020 · 158 citations
- Physics
- Particle physics
- Nuclear physics
A bstract A search for new resonances decaying into a pair of jets is reported using the dataset of proton-proton collisions recorded at $$ \sqrt{s} $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msqrt> <mml:mi>s</mml:mi> </mml:msqrt> </mml:math> = 13 TeV with the ATLAS detector at the Large Hadron Collider between 2015 and 2018, corresponding to an integrated luminosity of 139 fb − 1 . The distribution of the invariant mass of the two leading jets is examined for local excesses above a data-derived estimate of the Standard Model background. In addition to an inclusive dijet search, events with jets identified as containing b -hadrons are examined specifically. No significant excess of events above the smoothly falling background spectra is observed. The results are used to set cross-section upper limits at 95% confidence level on a range of new physics scenarios. Model-independent limits on Gaussian-shaped signals are also reported. The analysis looking at jets containing b -hadrons benefits from improvements in the jet flavour identification at high transverse momentum, which increases its sensitivity relative to the previous analysis beyond that expected from the higher integrated luminosity.
Frequent coauthors
- 2674 shared
T. Beau
Consejo Nacional de Investigaciones Científicas y Técnicas
- 2569 shared
J. Ocariz
Université Paris Cité
- 2538 shared
L. Roos
Laboratoire de Physique Nucléaire et de Hautes Énergies
- 2506 shared
S. De Cecco
Radboud University Nijmegen
- 2485 shared
S. Trincaz-Duvoid
Laboratoire de Physique Nucléaire et de Hautes Énergies
- 2480 shared
M. Ridel
Université Paris Cité
- 2354 shared
L. Li
- 2193 shared
B. Trocmé
Laboratoire AstroParticule et Cosmologie
Labs
Education
- 2021
Master&PHD
Shanghai Institute of Applied Physics Chinese Academy of Sciences
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