Faculty Publications: December, 2017
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Title: | 4d N=2 SCFT and singularity theory Part III: Rigid singularity | |
Authors: | Chen, Bingyi; Xie, Dan; Yau, Stephen S.-T.; Yau, Shing-Tung; Zuo, Huaiqing | |
Publication: | eprint arXiv:1712.00464 | |
Publication Date: | 12/2017 | |
Origin: | ARXIV | |
Keywords: | High Energy Physics - Theory, Mathematics - Algebraic Geometry | |
Comment: | 17 pages, 1 figure | |
Bibliographic Code: | 2017arXiv171200464C |
Abstract
We classify three fold isolated quotient Gorenstein singularity $C^3/G$. These singularities are rigid, i.e. there is no non-trivial deformation, and we conjecture that they define 4d $\mathcal{N}=2$ SCFTs which do not have a Coulomb branch.
Title: | The deformed Hermitian-Yang-Mills equation in geometry and physics | |
Authors: | Collins, Tristan C.; Xie, Dan; Yau, Shing-Tung | |
Publication: | eprint arXiv:1712.00893 | |
Publication Date: | 12/2017 | |
Origin: | ARXIV | |
Keywords: | Mathematics - Differential Geometry, High Energy Physics - Theory, Mathematics - Algebraic Geometry | |
Comment: | 20 pages | |
Bibliographic Code: | 2017arXiv171200893C |
Abstract
We provide an introduction to the mathematics and physics of the deformed Hermitian-Yang-Mills equation, a fully nonlinear geometric PDE on Kahler manifolds which plays an important role in mirror symmetry. We discuss the physical origin of the equation, and some recent progress towards its solution. In dimension 3 we prove a new Chern number inequality and discuss the relationship with algebraic stability conditions.
Title: | The Weak Gravity Conjecture and Emergence from an Ultraviolet Cutoff | |
Authors: | Heidenreich, Ben; Reece, Matthew; Rudelius, Tom | |
Publication: | eprint arXiv:1712.01868 | |
Publication Date: | 12/2017 | |
Origin: | ARXIV | |
Keywords: | High Energy Physics - Theory, High Energy Physics - Phenomenology | |
Comment: | 48 pages, 5 figures | |
Bibliographic Code: | 2017arXiv171201868H |
Abstract
We study ultraviolet cutoffs associated with the Weak Gravity Conjecture (WGC) and Sublattice Weak Gravity Conjecture (sLWGC). There is a magnetic WGC cutoff at the energy scale $e G_N^{-1/2}$ with an associated sLWGC tower of charged particles. A more fundamental cutoff is the scale at which gravity becomes strong and field theory breaks down entirely. By clarifying the nature of the sLWGC for nonabelian gauge groups we derive a parametric upper bound on this strong gravity scale for arbitrary gauge theories. Intriguingly, we show that in theories approximately saturating the sLWGC, the scales at which loop corrections from the tower of charged particles to the gauge boson and graviton propagators become important are parametrically identical. This suggests a picture in which gauge fields emerge from the quantum gravity scale by integrating out a tower of charged matter fields. We derive a converse statement: if a gauge theory becomes strongly coupled at or below the quantum gravity scale, the WGC follows. We sketch some phenomenological consequences of the UV cutoffs we derive.
Title: | Parton theory of magnetic polarons: Mesonic resonances and signatures in dynamics | |
Authors: | Grusdt, Fabian; Kanasz-Nagy, Marton; Bohrdt, Annabelle; Chiu, Christie S.; Ji, Geoffrey; Greiner, Markus; Greif, Daniel; Demler, Eugene | |
Publication: | eprint arXiv:1712.01874 | |
Publication Date: | 12/2017 | |
Origin: | ARXIV | |
Keywords: | Condensed Matter - Quantum Gases, Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Superconductivity, High Energy Physics - Theory, Quantum Physics | |
Comment: | 30 pages, 4 appendices, 26 figures | |
Bibliographic Code: | 2017arXiv171201874G |
Abstract
When a mobile hole is moving in an anti-ferromagnet it distorts the surrounding Neel order and forms a magnetic polaron. Such interplay between hole motion and anti-ferromagnetism is believed to be at the heart of high-Tc superconductivity in cuprates. We study a single hole described by the t-Jz model with Ising interactions between the spins in 2D. This situation can be experimentally realized in quantum gas microscopes. When the hole hopping is much larger than couplings between the spins, we find strong evidence that magnetic polarons can be understood as bound states of two partons, a spinon and a holon carrying spin and charge quantum numbers respectively. We introduce a microscopic parton description which is benchmarked by comparison with results from advanced numerical simulations. Using this parton theory, we predict a series of excited states that are invisible in the spectral function and correspond to rotational excitations of the spinon-holon pair. This is reminiscent of mesonic resonances observed in high-energy physics, which can be understood as rotating quark antiquark pairs. We also apply the strong coupling parton theory to study far-from equilibrium dynamics of magnetic polarons observable in current experiments with ultracold atoms. Our work supports earlier ideas that partons in a confining phase of matter represent a useful paradigm in condensed-matter physics and in the context of high-Tc superconductivity. While direct observations of spinons and holons in real space are impossible in traditional solid-state experiments, quantum gas microscopes provide a new experimental toolbox. We show that, using this platform, direct observations of partons in and out-of equilibrium are possible. Extensions of our approach to the t-J model are also discussed. Our predictions in this case are relevant to current experiments with quantum gas microscopes for ultracold atoms.
Title: | Mordell-Weil Torsion, Anomalies, and Phase Transitions | |
Authors: | Esole, Mboyo; Jinwoo Kang, Monica; Yau, Shing-Tung | |
Publication: | eprint arXiv:1712.02337 | |
Publication Date: | 12/2017 | |
Origin: | ARXIV | |
Keywords: | High Energy Physics - Theory, Mathematics - Algebraic Geometry | |
Comment: | 57 pages+ references, 13 figures, 15 tables | |
Bibliographic Code: | 2017arXiv171202337E |
Abstract
We explore how introducing a non-trivial Mordell-Weil group changes the structure of the Coulomb phases of a five-dimensional gauge theory from an M-theory compactified on an elliptically fibered Calabi-Yau threefolds with a I$_2$+I$_4$ collision of singularities. The resulting gauge theory has a semi-simple Lie algebra $\mathfrak{su}(2)\oplus \mathfrak{sp}(4)$ or $\mathfrak{su}(2)\oplus \mathfrak{su}(4)$. We compute topological invariants relevant for the physics, such as the Euler characteristic, Hodge numbers, and triple intersection numbers. We determine the matter representation geometrically by computing weights via intersection of curves and fibral divisors. We fix the number of charged hypermultiplets transforming in each representations by comparing the triple intersection numbers and the one-loop prepotential. This condition is enough to fix the number of representation when the Mordell-Weil group is $\mathbb{Z}_2$ but not when it is trivial. The vanishing of the fourth power of the curvature forms in the anomaly polynomial is enough to fix the number of representations. We discuss anomaly cancellations of the six-dimensional uplifted. In particular, the gravitational anomaly is also considered as the Hodge numbers are computed explicitly without counting the degrees of freedom of the Weierstrass equation.
Title: | Model-Independent Predictions for Smooth Cosmic Acceleration Scenarios | |
Authors: | Miranda, Vinicius; Dvorkin, Cora | |
Publication: | eprint arXiv:1712.04289 | |
Publication Date: | 12/2017 | |
Origin: | ARXIV | |
Keywords: | Astrophysics - Cosmology and Nongalactic Astrophysics, High Energy Physics - Phenomenology, High Energy Physics - Theory | |
Comment: | 18 pages, 16 figures (v2: typo corrected in the conclusions) | |
Bibliographic Code: | 2017arXiv171204289M |
Abstract
Through likelihood analyses of both current and future data that constrain both the expansion history of the universe and the clustering of matter fluctuations, we provide falsifiable predictions for three broad classes of models that explain the accelerated expansions of the universe: $\Lambda$CDM, the quintessence scenario and a more general class of smooth dark energy models that can cross the phantom barrier $w(z)=-1$. Our predictions are model independent in the sense that we do not rely on a specific parametrization, but we instead use a principal component (PC) basis function constructed a priori from a noise model of supernovae and Cosmic Microwave Background observations. For the supernovae measurements, we consider two type of surveys: the current JLA and the upcoming WFIRST surveys. We show that WFIRST will be able to improve growth predictions in curved models significantly. The remaining degeneracy between spatial curvature and $w(z)$ could be overcome with improved measurements of $\sigma_8 \Omega_m^{1/2}$, a combination that controls the amplitude of the growth of structure. We also point out that a PC-based Figure of Merit reveals that the usual two-parameter description of $w(z)$ does not exhaust the information that can be extracted from current data (JLA) or future data (WFIRST).
Title: | Fundamental Physics with the Hubble Space Telescope | |
Authors: | Dalal, Neal; Dvorkin, Cora; Heyl, Jeremy; Jain, Bhuvnesh; Kamionkowski, Marc; Marshall, Phil; Weinberg, David | |
Publication: | eprint arXiv:1712.04928 | |
Publication Date: | 12/2017 | |
Origin: | ARXIV | |
Keywords: | Astrophysics - Cosmology and Nongalactic Astrophysics | |
Comment: | Report of the HST and Fundamental Physics Working Group, constituted by STScI Director Ken Sembach to identify ways that HST could enable advances in fundamental physics | |
Bibliographic Code: | 2017arXiv171204928D |
Abstract
Cosmology is intrinsically intertwined with questions in fundamental physics. The existence of non-baryonic dark matter requires new physics beyond the Standard Model of elemenatary-particle interactions and Einstein's general relativity, as does the accelerating expansion of the universe. Current tensions between various cosmological measurements may be harbingers of yet more new physics. Progress on understanding dark matter and cosmic acceleration requires long term, high-precision measurements and excellent control of systematics, demanding observational programs that are often outside the discovery/characterization mode that drives many areas of astronomy. We outline potential programs through which the Hubble Space Telescope (HST) could have a major impact on issues in fundamental physics in the coming years. To realize this impact, we suggest the introduction of a "HST Fundamental Physics" observational program that would be subject to a modified proposal and review process.
Title: | Magnetotransport in a model of a disordered strange metal | |
Authors: | Patel, Aavishkar A.; McGreevy, John; Arovas, Daniel P.; Sachdev, Subir | |
Publication: | eprint arXiv:1712.05026 | |
Publication Date: | 12/2017 | |
Origin: | ARXIV | |
Keywords: | Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Disordered Systems and Neural Networks, High Energy Physics - Theory | |
Comment: | 18+epsilon pages + Appendices + References, 4 figures | |
Bibliographic Code: | 2017arXiv171205026P |
Abstract
We engineer a microscopic model of two-dimensional conduction electrons locally and randomly scattering off impurity sites which are described by Sachdev-Ye-Kitaev (SYK) models. For a particular choice of the scattering interaction, this model realizes a controlled description of a diffusive marginal-Fermi liquid (MFL) without momentum conservation, which has a linear-in-$T$ resistivity and a $T\ln T$ specific heat as $T \rightarrow 0$. By tuning the strength of the scattering interaction relative to the bandwidth of the conduction electrons, we can additionally obtain a finite-$T$ crossover to a fully incoherent regime that also has a linear-in-$T$ resistivity. We describe the magnetotransport properties of this model. We then consider a macroscopically disordered sample with domains of such MFLs with varying electron and impurity densities. Using an effective-medium approximation, we obtain a macroscopic electrical resistance that scales linearly in the magnetic field $B$ applied perpendicular to the plane of the sample, at large $B$. The resistance also scales linearly in $T$ at small $B$, and as $T f(B/T)$ at intermediate $B$. We consider implications for recent experiments reporting linear transverse magnetoresistance in the strange metal phases of the pnictides and cuprates.
Title: | Quantum optics with diamond color centers coupled to nanophotonic devices | |
Authors: | Sipahigil, Alp; Lukin, Mikhail D. | |
Publication: | eprint arXiv:1712.06693 | |
Publication Date: | 12/2017 | |
Origin: | ARXIV | |
Keywords: | Quantum Physics, Physics - Optics | |
Comment: | Lecture notes for the Les Houches Summer School, Session CVII--Current Trends in Atomic Physics, July 2016. 35 pages and 9 figures | |
Bibliographic Code: | 2017arXiv171206693S |
Abstract
We review recent advances towards the realization of quantum networks based on atom-like solid-state quantum emitters coupled to nanophotonic devices. Specifically, we focus on experiments involving the negatively charged silicon-vacancy color center in diamond. These emitters combine homogeneous, coherent optical transitions and a long-lived electronic spin quantum memory. We discuss optical and spin properties of this system at cryogenic temperatures and describe experiments where silicon-vacancy centers are coupled to nanophotonic devices. Finally, we discuss experiments demonstrating quantum nonlinearities at the single-photon level and two-emitter entanglement in a single nanophotonic device.
Title: | Quantum state engineering of a Hubbard system with ultracold fermions | |
Authors: | Chiu, Christie S.; Ji, Geoffrey; Mazurenko, Anton; Greif, Daniel; Greiner, Markus | |
Publication: | eprint arXiv:1712.07114 | |
Publication Date: | 12/2017 | |
Origin: | ARXIV | |
Keywords: | Condensed Matter - Quantum Gases | |
Comment: | 6+2 pages, 4+2 figures | |
Bibliographic Code: | 2017arXiv171207114C |
Abstract
Accessing new regimes in quantum simulation requires development of new techniques for quantum state preparation. We demonstrate quantum state engineering of a strongly-correlated many-body state of the two-component repulsive Fermi-Hubbard model on a square lattice. Our scheme makes use of an ultra-low entropy doublon band insulator created through entropy redistribution. After isolating the band insulator, we change the underlying potential to expand it into a half-filled system. The final many-body state realized shows strong antiferromagnetic correlations and a temperature below the exchange energy. We observe an increase in entropy, which we find is likely caused by the many-body physics in the last step of the scheme. This technique is promising for low-temperature studies of cold-atom-based lattice models.
Title: | A New Light Higgs Boson and Short-Baseline Neutrino Anomalies | |
Authors: | Asaadi, J.; Church, E.; Guenette, R.; Jones, B. J. P.; Szelc, A. M. | |
Publication: | eprint arXiv:1712.08019 | |
Publication Date: | 12/2017 | |
Origin: | ARXIV | |
Keywords: | High Energy Physics - Phenomenology, High Energy Physics - Experiment | |
Comment: | 11 pages, 6 figures, submitted to PRD | |
Bibliographic Code: | 2017arXiv171208019A |
Abstract
The low-energy excesses observed by the MiniBooNE experiment have, to date, defied a convinc- ing explanation under the standard model even with accommodation for non-zero neutrino mass. In this paper we explore a new oscillation mechanism to explain these anomalies, invoking a light neu- trinophilic Higgs boson, conceived to induce a low Dirac neutrino mass in accord with experimental limits. Beam neutrinos forward-scattering off of a locally over-dense relic neutrino background give rise to a novel matter-effect with an energy-specific resonance. An enhanced oscillation around this resonance peak produces flavor transitions which are highly consistent with the MiniBooNE neutrino- and antineutrino-mode data sets. The model provides substantially improved $\chi^2$ values beyond either the no-oscillation hypothesis or the more commonly explored 3+1 sterile neutrino hy- pothesis. This mechanism would introduce distinctive signatures at each baseline in the upcoming SBN program at Fermilab, presenting opportunities for further exploration.
Title: | A search for the exotic meson $X(5568)$ with the Collider Detector at Fermilab | |
Authors: | CDF Collaboration; Aaltonen, T.; Amerio, S.; Amidei, D.;... Franklin, M.;... and 393 coauthors | |
Publication: | eprint arXiv:1712.09620 | |
Publication Date: | 12/2017 | |
Origin: | ARXIV | |
Keywords: | High Energy Physics - Experiment | |
Comment: | 13 pages, 3 figures | |
Bibliographic Code: | 2017arXiv171209620C |
Abstract
A search for the exotic meson $X(5568)$ decaying into the $B^0_s \pi^{\pm}$ final state is performed using data corresponding to $9.6 \textrm{fb}^{-1}$ from $p{\bar p}$ collisions at $\sqrt{s} = 1960$ GeV recorded by the Collider Detector at Fermilab. No evidence for this state is found and an upper limit of 6.7\% at the 95\% confidence level is set on the fraction of $B^0_s$ produced through the $X(5568) \rightarrow B^0_s \, \pi^{\pm}$ process.
Title: | Determination of the strong coupling constant α _{s} from transverse energy-energy correlations in multijet events at √{s} = 8 TeV using the ATLAS detector | |
Authors: | Aaboud, M.; Aad, G.; Abbott, B.; Abdallah, J.;... Franklin, M.;... Huth, J.;... Morii, M.; ... ATLAS Collaboration | |
Publication: | The European Physical Journal C, Volume 77, Issue 12, article id. #872, 34 pp. (EPJC Homepage) | |
Publication Date: | 12/2017 | |
Origin: | SPRINGER | |
Abstract Copyright: | (c) 2017: CERN for the benefit of the ATLAS collaboration | |
DOI: | 10.1140/epjc/s10052-017-5442-0 | |
Bibliographic Code: | 2017EPJC...77..872A |
Abstract
Measurements of transverse energy-energy correlations and their associated asymmetries in multi-jet events using the ATLAS detector at the LHC are presented. The data used correspond to √{s} = 8 TeV proton-proton collisions with an integrated luminosity of 20.2 fb^{-1}. The results are presented in bins of the scalar sum of the transverse momenta of the two leading jets, unfolded to the particle level and compared to the predictions from Monte Carlo simulations. A comparison with next-to-leading-order perturbative QCD is also performed, showing excellent agreement within the uncertainties. From this comparison, the value of the strong coupling constant is extracted for different energy regimes, thus testing the running of α s(μ ) predicted in QCD up to scales over 1 TeV. A global fit to the transverse energy-energy correlation distributions yields α s(m_Z) = 0.1162 ± 0.0011 (exp.) ^{+0.0084}_{-0.0070} (theo.) , while a global fit to the asymmetry distributions yields a value of α s(m_Z) = 0.1196 ± 0.0013 (exp.) ^{+0.0075}_{-0.0045} (theo.).
Title: | Search for direct top squark pair production in final states with two leptons in √{s} = 13 TeV pp collisions with the ATLAS detector | |
Authors: | Aaboud, M.; Aad, G.; Abbott, B.; Abdinov, O.;... Franklin, M.;... Huth, J.;... Morii, M.;... | |
Publication: | The European Physical Journal C, Volume 77, Issue 12, article id. #898, 41 pp. (EPJC Homepage) | |
Publication Date: | 12/2017 | |
Origin: | SPRINGER | |
Abstract Copyright: | (c) 2017: CERN for the benefit of the ATLAS collaboration | |
DOI: | 10.1140/epjc/s10052-017-5445-x | |
Bibliographic Code: | 2017EPJC...77..898A |
Abstract
The results of a search for direct pair production of top squarks in events with two opposite-charge leptons (electrons or muons) are reported, using 36.1 fb^{-1} of integrated luminosity from proton-proton collisions at √{s}=13 TeV collected by the ATLAS detector at the Large Hadron Collider. To cover a range of mass differences between the top squark \tilde{t} and lighter supersymmetric particles, four possible decay modes of the top squark are targeted with dedicated selections: the decay \tilde{t} → b \tilde{χ }_{1}^{± } into a b-quark and the lightest chargino with \tilde{χ}_{1}^{± } → W \tilde{χ }_{1}^{0}, the decay \tilde{t} → t \tilde{χ }_{1}^{0} into an on-shell top quark and the lightest neutralino, the three-body decay \tilde{t} → b W \tilde{χ}_{1}^{0} and the four-body decay \tilde{t} → b ℓ ν \tilde{χ }_{1}^{0}. No significant excess of events is observed above the Standard Model background for any selection, and limits on top squarks are set as a function of the \tilde{t} and \tilde{χ }_{1}^{0} masses. The results exclude at 95% confidence level \tilde{t} masses up to about 720 GeV, extending the exclusion region of supersymmetric parameter space covered by previous searches.
Title: | Summary talk — SCGT15 | |
Authors: | Georgi, Howard | |
Publication: | International Journal of Modern Physics A, Volume 32, Issue 36, id. 1747027-414 (IJMPA Homepage) | |
Publication Date: | 12/2017 | |
Origin: | WSPC | |
Keywords: | Conformal, strong-couple gauge theories, Higgs, dilaton, Pseudo-Goldstone | |
Abstract Copyright: | (c) 2017: World Scientific Publishing Company | |
DOI: | 10.1142/S0217751X17470273 | |
Bibliographic Code: | 2017IJMPA..3247027G |
Abstract
In this brief talk, I will try to focus on the things that happened at the conference that seemed very important, but that I didn’t understand.
Title: | A force-matching Stillinger-Weber potential for MoS2: Parameterization and Fisher information theory based sensitivity analysis | |
Authors: | Wen, Mingjian; Shirodkar, Sharmila N.; Plecháč, Petr; Kaxiras, Efthimios; Elliott, Ryan S.; Tadmor, Ellad B. | |
Publication: | Journal of Applied Physics, Volume 122, Issue 24, id.244301 (JAP Homepage) | |
Publication Date: | 12/2017 | |
Origin: | AIP | |
Abstract Copyright: | 2017: Author(s) | |
DOI: | 10.1063/1.5007842 | |
Bibliographic Code: | 2017JAP...122x4301W |
Abstract
Two-dimensional molybdenum disulfide (MoS2) is a promising material for the next generation of switchable transistors and photodetectors. In order to perform large-scale molecular simulations of the mechanical and thermal behavior of MoS2-based devices, an accurate interatomic potential is required. To this end, we have developed a Stillinger-Weber potential for monolayer MoS2. The potential parameters are optimized to reproduce the geometry (bond lengths and bond angles) of MoS2 in its equilibrium state and to match as closely as possible the forces acting on the atoms along a dynamical trajectory obtained from ab initio molecular dynamics. Verification calculations indicate that the new potential accurately predicts important material properties including the strain dependence of the cohesive energy, the elastic constants, and the linear thermal expansion coefficient. The uncertainty in the potential parameters is determined using a Fisher information theory analysis. It is found that the parameters are fully identified, and none are redundant. In addition, the Fisher information matrix provides uncertainty bounds for predictions of the potential for new properties. As an example, bounds on the average vibrational thickness of a MoS2 monolayer at finite temperature are computed and found to be consistent with the results from a molecular dynamics simulation. The new potential is available through the OpenKIM interatomic potential repository at https://openkim.org/cite/MO_201919462778_000.
Title: | Point sources from dissipative dark matter | |
Authors: | Agrawal, Prateek; Randall, Lisa | |
Publication: | Journal of Cosmology and Astroparticle Physics, Issue 12, article id. 019 (2017). (JCAP Homepage) | |
Publication Date: | 12/2017 | |
Origin: | IOP | |
DOI: | 10.1088/1475-7516/2017/12/019 | |
Bibliographic Code: | 2017JCAP...12..019A |
Abstract
If a component of dark matter has dissipative interactions, it can cool to form compact astrophysical objects with higher density than that of conventional cold dark matter (sub)haloes. Dark matter annihilations might then appear as point sources, leading to novel morphology for indirect detection. We explore dissipative models where interaction with the Standard Model might provide visible signals, and show how such objects might give rise to the observed excess in gamma rays arising from the galactic center.
Title: | Analysis of the Wtb vertex from the measurement of triple-differential angular decay rates of single top quarks produced in the t-channel at √{s}=8 TeV with the ATLAS detector | |
Authors: | Aaboud, M.; Aad, G.; Abbott, B.; Abdallah, J.;... Franklin, M.;... Huth, J.;... Morii, M.;... | |
Publication: | Journal of High Energy Physics, Volume 2017, Issue 12, article id. #17, 60 pp. | |
Publication Date: | 12/2017 | |
Origin: | SPRINGER | |
Keywords: | Electroweak interaction, Hadron-Hadron scattering (experiments), Top physics | |
Abstract Copyright: | (c) 2017: The Author(s) | |
DOI: | 10.1007/JHEP12(2017)017 | |
Bibliographic Code: | 2017JHEP...12..017A |
Abstract
The electroweak production and subsequent decay of single top quarks in the t-channel is determined by the properties of the Wtb vertex, which can be described by the complex parameters of an effective Lagrangian. An analysis of a triple-differential decay rate in t-channel production is used to simultaneously determine five generalised helicity fractions and phases, as well as the polarisation of the produced top quark. The complex parameters are then constrained. This analysis is based on 20.2 fb^{-1} of proton-proton collision data at a centre-of-mass energy of 8 TeV collected with the ATLAS detector at the LHC. The fraction of decays containing transversely polarised W bosons is measured to be f _{1} = 0.30 ± 0.05. The phase between amplitudes for transversely and longitudinally polarised W bosons recoiling against left-handed b-quarks is measured to be δ _{-} = 0.002 π _{+ 0.017 π } ^{+ 0.016 π } , giving no indication of CP violation. The fractions of longitudinal or transverse W bosons accompanied by right-handed b-quarks are also constrained. Based on these measurements, limits are placed at 95% CL on the ratio of the complex coupling parameters Re [g_{R}/V_{ L } ∈ [-0.12, 0.17] and Im [g_{R}/V_{L} ∈ [-0.07, 0.06]. Constraints are alsoplaced on the ratios | V _{R}/ V _{L}| and | g_{L}/ V _{L}|. In addition, the polarisation of singletop quarks in the t-channel is constrained to be P > 0.72 (95% CL). None of the above measurements make assumptions about the value of any of the other parameters or couplings and all of them are in agreement with the Standard Model. [Figure not available: see fulltext.]
Title: | Evidence for the H\to b\overline{b} decay with the ATLAS detector | |
Authors: | Aaboud, M.; Aad, G.; Abbott, B.; Abdinov, O.;... Franklin, M.;... Huth, J.;... Morii, M.;... | |
Publication: | Journal of High Energy Physics, Volume 2017, Issue 12, article id. #24, 71 pp. | |
Publication Date: | 12/2017 | |
Origin: | SPRINGER | |
Keywords: | Hadron-Hadron scattering (experiments), Higgs physics | |
Abstract Copyright: | (c) 2017: The Author(s) | |
DOI: | 10.1007/JHEP12(2017)024 | |
Bibliographic Code: | 2017JHEP...12..024A |
Abstract
A search for the decay of the Standard Model Higgs boson into a b\overline{b} pair when produced in association with a W or Z boson is performed with the ATLAS detector. The analysed data, corresponding to an integrated luminosity of 36.1 fb^{-1}, were collected in proton-proton collisions in Run 2 of the Large Hadron Collider at a centre-of-mass energy of 13 TeV. Final states containing zero, one and two charged leptons (electrons or muons) are considered, targeting the decays Z → νν, W → ℓν and Z → ℓℓ. For a Higgs boson mass of 125 GeV, an excess of events over the expected background from other Standard Model processes is found with an observed significance of 3.5 standard deviations, compared to an expectation of 3.0 standard deviations. This excess provides evidence for the Higgs boson decay into b-quarks and for its production in association with a vector boson. The combination of this result with that of the Run 1 analysis yields a ratio of the measured signal events to the Standard Model expectation equal to 0.90 ± 0.18(stat.) _{- 0.19} ^{+ 0.21} (syst.). Assuming the Standard Model production cross-section, the results are consistent with the value of the Yukawa coupling to b-quarks in the Standard Model. [Figure not available: see fulltext.]
Title: | Search for new phenomena with large jet multiplicities and missing transverse momentum using large-radius jets and flavour-tagging at ATLAS in 13 TeV pp collisions | |
Authors: | Aaboud, M.; Aad, G.; Abbott, B.; Abdinov, O.;... Franklin, M.;... Huth, J.;... Morii, M.;... | |
Publication: | Journal of High Energy Physics, Volume 2017, Issue 12, article id. #34, 52 pp. | |
Publication Date: | 12/2017 | |
Origin: | SPRINGER | |
Keywords: | Beyond Standard Model, Hadron-Hadron scattering (experiments), Supersymmetry | |
Abstract Copyright: | (c) 2017: The Author(s) | |
DOI: | 10.1007/JHEP12(2017)034 | |
Bibliographic Code: | 2017JHEP...12..034A |
Abstract
A search is presented for particles that decay producing a large jet multiplicity and invisible particles. The event selection applies a veto on the presence of isolated electrons or muons and additional requirements on the number of b-tagged jets and the scalar sum of masses of large-radius jets. Having explored the full ATLAS 2015-2016 dataset of LHC proton-proton collisions at √{s}=13 TeV, which corresponds to 36.1 fb^{-1} of integrated luminosity, no evidence is found for physics beyond the Standard Model. The results are interpreted in the context of simplified models inspired by R-parity-conserving and R-parity-violating supersymmetry, where gluinos are pair-produced. More generic models within the phenomenological minimal supersymmetric Standard Model are also considered. [Figure not available: see fulltext.]
Title: | Pileup Mitigation with Machine Learning (PUMML) | |
Authors: | Komiske, Patrick T.; Metodiev, Eric M.; Nachman, Benjamin; Schwartz, Matthew D. | |
Publication: | Journal of High Energy Physics, Volume 2017, Issue 12, article id. #51, 20 pp. | |
Publication Date: | 12/2017 | |
Origin: | SPRINGER | |
Keywords: | Jets | |
Abstract Copyright: | (c) 2017: The Author(s) | |
DOI: | 10.1007/JHEP12(2017)051 | |
Bibliographic Code: | 2017JHEP...12..051K |
Abstract
Pileup involves the contamination of the energy distribution arising from the primary collision of interest (leading vertex) by radiation from soft collisions (pileup). We develop a new technique for removing this contamination using machine learning and convolutional neural networks. The network takes as input the energy distribution of charged leading vertex particles, charged pileup particles, and all neutral particles and outputs the energy distribution of particles coming from leading vertex alone. The PUMML algorithm performs remarkably well at eliminating pileup distortion on a wide range of simple and complex jet observables. We test the robustness of the algorithm in a number of ways and discuss how the network can be trained directly on data.
Title: | Measurement of the Drell-Yan triple-differential cross section in pp collisions at √{s}=8 TeV | |
Authors: | Aaboud, M.; Aad, G.; Abbott, B.; Abdinov, O.;... Franklin, M.;... Huth, J.;... Morii, M.;... | |
Publication: | Journal of High Energy Physics, Volume 2017, Issue 12, article id. #59, 80 pp. | |
Publication Date: | 12/2017 | |
Origin: | SPRINGER | |
Keywords: | Hadron-Hadron scattering (experiments) | |
Abstract Copyright: | (c) 2017: The Author(s) | |
DOI: | 10.1007/JHEP12(2017)059 | |
Bibliographic Code: | 2017JHEP...12..059A |
Abstract
This paper presents a measurement of the triple-differential cross section for the Drell-Yan process Z/ γ ^{*} → ℓ^{+} ℓ^{-} where ℓ is an electron or a muon. The measurement is performed for invariant masses of the lepton pairs, m_{ℓℓ}, between 46 and 200 GeV using a sample of 20.2 fb^{-1} of pp collisions data at a centre-of-mass energy of √{s}=8 TeV collected by the ATLAS detector at the LHC in 2012. The data are presented in bins of invariant mass, absolute dilepton rapidity, | y_{ℓℓ}|, and the angular variable cos θ^{*} between the outgoing lepton and the incoming quark in the Collins-Soper frame. The measurements are performed in the range | y_{ℓℓ}| < 2.4 in the muon channel, and extended to | y _{ℓℓ}| < 3.6 in the electron channel. The cross sections are used to determine the Z boson forward-backward asymmetry as a function of | y _{ ℓℓ}| and m _{ℓℓ}. The measurements achieve high-precision, below the percent level in the pole region, excluding the uncertainty in the integrated luminosity, and are in agreement with predictions. These precision data are sensitive to the parton distribution functions and the effective weak mixing angle.
Title: | Search for a scalar partner of the top quark in the jets plus missing transverse momentum final state at √{s}=13 TeV with the ATLAS detector | |
Authors: | Aaboud, M.; Aad, G.; Abbott, B.; Abdinov, O.;... Franklin, M.;... Huth, J.;... Morii, M.;... | |
Publication: | Journal of High Energy Physics, Volume 2017, Issue 12, article id. #85, 56 pp. | |
Publication Date: | 12/2017 | |
Origin: | SPRINGER | |
Keywords: | Hadron-Hadron scattering (experiments) | |
Abstract Copyright: | (c) 2017: The Author(s) | |
DOI: | 10.1007/JHEP12(2017)085 | |
Bibliographic Code: | 2017JHEP...12..085A |
Abstract
A search for pair production of a scalar partner of the top quark in events with four or more jets plus missing transverse momentum is presented. An analysis of 36.1 fb^{-1} of √{s}=13 TeV proton-proton collisions collected using the ATLAS detector at the LHC yields no significant excess over the expected Standard Model background. To interpret the results a simplified supersymmetric model is used where the top squark is assumed to decay via {\tilde{t}}_1\to {t}^{(\ast )}{\tilde{\upchi}}_1^0 and {\tilde{t}}_1\to b{\tilde{\upchi}}_1^{±}\to b{W}^{(\ast )}{\tilde{\upchi}}_1^0 , where χ 1^{0} (χ 1^{±} ) denotes the lightest neutralino (chargino). Exclusion limits are placed in terms of the top-squark and neutralino masses. Assuming a branching ratio of 100% to t{\tilde{\upchi}}_1^0 , top-squark masses in the range 450-1000 GeV are excluded for {\tilde{\upchi}}_1^0 masses below 160 GeV. In the case where {m}_{{\tilde{t}}_1}˜ {m}_t+{m}_{{\tilde{χ}}_1^0} , top-squark masses in the range 235-590 GeV are excluded.
Title: | Toda theory from six dimensions | |
Authors: | Córdova, Clay; Jafferis, Daniel L. | |
Publication: | Journal of High Energy Physics, Volume 2017, Issue 12, article id. #106, 33 pp. | |
Publication Date: | 12/2017 | |
Origin: | SPRINGER | |
Keywords: | Effective Field Theories, Field Theories in Higher Dimensions, Supersymmetric Gauge Theory, Topological Field Theories | |
Abstract Copyright: | (c) 2017: The Author(s) | |
DOI: | 10.1007/JHEP12(2017)106 | |
Bibliographic Code: | 2017JHEP...12..106C |
Abstract
We describe a compactification of the six-dimensional (2,0) theory on a foursphere which gives rise to a two-dimensional Toda theory at long distances. This construction realizes chiral Toda fields as edge modes trapped near the poles of the sphere. We relate our setup to compactifications of the (2,0) theory on the five and six-sphere. In this way, we explain a connection between half-BPS operators of the (2,0) theory and twodimensional W-algebras, and derive an equality between their conformal anomalies. As we explain, all such relationships between the six-dimensional (2,0) theory and Toda field theory can be interpreted as statements about the edge modes of complex Chern-Simons on various three-manifolds with boundary.Title: | Traversable wormholes via a double trace deformation | |
Authors: | Gao, Ping; Jafferis, Daniel Louis; Wall, Aron C. | |
Publication: | Journal of High Energy Physics, Volume 2017, Issue 12, article id. #151, 25 pp. | |
Publication Date: | 12/2017 | |
Origin: | SPRINGER | |
Keywords: | Black Holes, Gauge-gravity correspondence | |
Abstract Copyright: | (c) 2017: The Author(s) | |
DOI: | 10.1007/JHEP12(2017)151 | |
Bibliographic Code: | 2017JHEP...12..151G |
Abstract
After turning on an interaction that couples the two boundaries of an eternal BTZ black hole, we find a quantum matter stress tensor with negative average null energy, whose gravitational backreaction renders the Einstein-Rosen bridge traversable. Such a traversable wormhole has an interesting interpretation in the context of ER=EPR, which we suggest might be related to quantum teleportation. However, it cannot be used to violate causality. We also discuss the implications for the energy and holographic entropy in the dual CFT description.
Title: | Study of the material of the ATLAS inner detector for Run 2 of the LHC | |
Authors: | Aaboud, M.; Aad, G.; Abbott, B.; Abdallah, J.;... Franklin, M.;... Huth, J.;... Morii, M.;... | |
Publication: | Journal of Instrumentation, Volume 12, Issue 12, pp. P12009 (2017). | |
Publication Date: | 12/2017 | |
Origin: | IOP | |
DOI: | 10.1088/1748-0221/12/12/P12009 | |
Bibliographic Code: | 2017JInst..12P2009A |
Abstract
The ATLAS inner detector comprises three different sub-detectors: the pixel detector, the silicon strip tracker, and the transition-radiation drift-tube tracker. The Insertable B-Layer, a new innermost pixel layer, was installed during the shutdown period in 2014, together with modifications to the layout of the cables and support structures of the existing pixel detector. The material in the inner detector is studied with several methods, using a low-luminosity √s=13 TeV pp collision sample corresponding to around 2.0 nb^{-1} collected in 2015 with the ATLAS experiment at the LHC. In this paper, the material within the innermost barrel region is studied using reconstructed hadronic interaction and photon conversion vertices. For the forward rapidity region, the material is probed by a measurement of the efficiency with which single tracks reconstructed from pixel detector hits alone can be extended with hits on the track in the strip layers. The results of these studies have been taken into account in an improved description of the material in the ATLAS inner detector simulation, resulting in a reduction in the uncertainties associated with the charged-particle reconstruction efficiency determined from simulation.
Title: | Measurement of cosmic-ray reconstruction efficiencies in the MicroBooNE LArTPC using a small external cosmic-ray counter | |
Authors: | Acciarri, R.; Adams, C.; An, R.;...Guenette, R.;... | |
Publication: | Journal of Instrumentation, Volume 12, Issue 12, pp. P12030 (2017). | |
Publication Date: | 12/2017 | |
Origin: | IOP | |
DOI: | 10.1088/1748-0221/12/12/P12030 | |
Bibliographic Code: | 2017JInst..12P2030A |
Abstract
The MicroBooNE detector is a liquid argon time projection chamber at Fermilab designed to study short-baseline neutrino oscillations and neutrino-argon interaction cross-section. Due to its location near the surface, a good understanding of cosmic muons as a source of backgrounds is of fundamental importance for the experiment. We present a method of using an external 0.5 m (L) × 0.5 m (W) muon counter stack, installed above the main detector, to determine the cosmic-ray reconstruction efficiency in MicroBooNE. Data are acquired with this external muon counter stack placed in three different positions, corresponding to cosmic rays intersecting different parts of the detector. The data reconstruction efficiency of tracks in the detector is found to be epsilondata=(97.1±0.1 (stat) ± 1.4 (sys))%, in good agreement with the Monte Carlo reconstruction efficiency epsilonMC = (97.4±0.1)%. This analysis represents a small-scale demonstration of the method that can be used with future data coming from a recently installed cosmic-ray tagger system, which will be able to tag ≈80% of the cosmic rays passing through the MicroBooNE detector.
Title: | Metallic atomic hydrogen at a pressure of 300-500 GPa | |
Authors: | Degtyarenko, N. N.; Mazur, E. A. | |
Publication: | Journal of Physics: Conference Series, Volume 941, Issue 1, article id. 012060 (2017). | |
Publication Date: | 12/2017 | |
Origin: | IOP | |
DOI: | 10.1088/1742-6596/941/1/012060 | |
Bibliographic Code: | 2017JPhCS.941a2060D |
Abstract
Atomic metallic hydrogen with a symmetry FDDD of a lattice cell is shown to have a stable crystalline structure under hydrostatic compression in the pressure range of 350-500 GPa. The resulting phase is shown to have a stable structure regarding the collapse of the phonon spectrum. Ab-initio simulation method has been used to calculate the structural, electronic, phonon and other characteristics of the normal FDDD metallic phase of hydrogen at a pressure of 350-500 GPA.
Title: | Observation of Electron Coherence and Fabry–Perot Standing Waves at a Graphene Edge | |
Authors: | Allen, Monica T.; Shtanko, Oles; Fulga, Ion C.; Wang, Joel I.-J.; Nurgaliev, Daniyar; Watanabe, Kenji; Taniguchi, Takashi; Akhmerov, Anton R.; Jarillo-Herrero, Pablo; Levitov, Leonid S.; Yacoby, Amir | |
Publication: | Nano Letters, vol. 17, issue 12, pp. 7380-7386 | |
Publication Date: | 12/2017 | |
Origin: | CROSSREF | |
DOI: | 10.1021/acs.nanolett.7b03156 | |
Bibliographic Code: | 2017NanoL..17.7380A |
Abstract
Not Available
Title: | 2D materials: Curved paths of electron-hole pairs | |
Authors: | Jauregui, Luis A.; Kim, Philip | |
Publication: | Nature Materials, Volume 16, Issue 12, pp. 1169-1170 (2017). | |
Publication Date: | 12/2017 | |
Origin: | NATURE | |
Abstract Copyright: | (c) 2017: Nature Publishing Group, a division of Macmillan Publishers Limited. All Rights Reserved. | |
DOI: | 10.1038/nmat5046 | |
Bibliographic Code: | 2017NatMa..16.1169J |
Abstract
The Hall effect with excitons is observed in monolayers of transition metal dichalcogenides.
Title: | Search for new phenomena in high-mass diphoton final states using 37 fb^{-1} of proton-proton collisions collected at √{ s } = 13 TeV with the ATLAS detector | |
Authors: | Aaboud, M.; Aad, G.; Abbott, B.; Abdinov, O.;... Franklin, M.;... Huth, J.;... Morii, M.;... | |
Publication: | Physics Letters B, Volume 775, p. 105-125. | |
Publication Date: | 12/2017 | |
Origin: | ELSEVIER | |
Abstract Copyright: | (c) 2017 Elsevier Science B.V. All rights reserved. | |
DOI: | 10.1016/j.physletb.2017.10.039 | |
Bibliographic Code: | 2017PhLB..775..105A |
Abstract
Searches for new phenomena in high-mass diphoton final states with the ATLAS experiment at the LHC are presented. The analysis is based on pp collision data corresponding to an integrated luminosity of 36.7 fb-1 at a centre-of-mass energy √{ s } = 13 TeV recorded in 2015 and 2016. Searches are performed for resonances with spin 0, as predicted by theories with an extended Higgs sector, and for resonances with spin 2, using a warped extra-dimension model as a benchmark model, as well as for non-resonant signals, assuming a large extra-dimension scenario. No significant deviation from the Standard Model is observed. Upper limits are placed on the production cross section times branching ratio to two photons as a function of the resonance mass. In addition, lower limits are set on the ultraviolet cutoff scale in the large extra-dimensions model.
AbstractThe cross-section for the production of two jets in association with a leptonically decaying Z boson (Zjj) is measured in proton-proton collisions at a centre-of-mass energy of 13 TeV, using data recorded with the ATLAS detector at the Large Hadron Collider, corresponding to an integrated luminosity of 3.2 fb-1. The electroweak Zjj cross-section is extracted in a fiducial region chosen to enhance the electroweak contribution relative to the dominant Drell-Yan Zjj process, which is constrained using a data-driven approach. The measured fiducial electroweak cross-section is σEWZjj = 119 ± 16 (stat .) ± 20 (syst .) ± 2 (lumi .) fb for dijet invariant mass greater than 250 GeV, and 34.2 ± 5.8 (stat .) ± 5.5 (syst .) ± 0.7 (lumi .) fb for dijet invariant mass greater than 1 TeV. Standard Model predictions are in agreement with the measurements. The inclusive Zjj cross-section is also measured in six different fiducial regions with varying contributions from electroweak and Drell-Yan Zjj production.
AbstractTwo-dimensional atomic arrays exhibit a number of intriguing quantum optical phenomena, including subradiance, nearly perfect reflection of radiation, and long-lived topological edge states. Studies of emission and scattering of photons in such lattices require complete treatment of the radiation pattern from individual atoms, including long-range interactions. We describe a systematic approach to perform the calculations of collective energy shifts and decay rates in the presence of such long-range interactions for arbitrary two-dimensional atomic lattices. As applications of our method, we investigate the topological properties of atomic lattices both in free space and near plasmonic surfaces.
AbstractAtoms in transversely pumped optical cavities "self-organize" by forming a density wave and emitting superradiantly into the cavity mode(s). For a single-mode cavity, the properties of this self-organization transition are well characterized both theoretically and experimentally. Here, we explore the self-organization of a Bose-Einstein condensate in the presence of two cavity modes—a system that recently was realized experimentally [Léonard et al., Nature (London) 543, 87 (2017), 10.1038/nature21067]. We argue that this system can exhibit a "vestigially ordered" phase in which neither cavity mode exhibits superradiance but the cavity modes are mutually phase locked by the atoms. We argue that this vestigially ordered phase should generically be present in multimode cavity geometries.
AbstractThe anomalous surface states of symmetry protected topological (SPT) phases are usually thought to be only possible in conjunction with the higher-dimensional topological bulk. However, it has recently been realized that a class of anomalous SPT surface states can be realized in the same dimension if symmetries are allowed to act in a nonlocal fashion. An example is the particle-hole symmetric half-filled Landau level, which effectively realizes the anomalous surface state of a 3 d chiral topological insulator (class AIII). A dual description in terms of Dirac composite fermions has also been discussed. Here we explore generalizations of these constructions to multicomponent quantum Hall states. Our results include a duality mapping of the bilayer case to composite bosons with Kramers degeneracy and the possibility of a particle-hole symmetric integer quantum Hall state when the number of components is a multiple of eight. Next, we make a further extension by half-filling other classes of topological bands and imposing particle-hole symmetry. When applied to time-reversal invariant topological insulators, we realize a different chiral class (CII) topological surface state. Notably, half-filling a 3 d TI band allows for the realization of the surface of the otherwise inaccessible 4 d topological insulator, which supports an anomalous 3 d Dirac cone. Surface topological orders equivalent to the 3 d Dirac cone (from the global anomaly standpoint) are constructed and connections to Witten's SU(2) anomaly are made. These observations may also be useful for numerical simulations of topological surface states and of Dirac fermions without fermion doubling.
AbstractGoncharov and Geballe reanalyze [Phys. Rev. B 96, 157101 (2017), 10.1103/PhysRevB.96.157101] experimental data using a finite element analysis and cannot reproduce our experimental heating curves; they use incomplete and incorrect material properties. They analyze optical data at the onset of the insulator-to-metal transition to show that it cannot be fit to a Drude model, not realizing that the Drude model does not describe metallic hydrogen in this transition region. Yet, they ignore the region where the reflectance is saturated and the data can be fit to the Drude model. They suggest that we observe semiconducting behavior rather than metallic behavior, but a straightforward calculation shows that reflectance from a semiconductor cannot explain our observed reflectance.
AbstractHowie, Dalladay-Simpson, and Gregoryanz Phys. Rev. B 96, 157102 (2017), 10.1103/PhysRevB.96.157102 comment on our observation of liquid metallic hydrogen (LMH). All of their objections are answered in our response. The experimental observation of LMH at static pressures stands on firm ground.
AbstractWe theoretically discover a family of nonequilibrium fractional topological phases in which time-periodic driving of a 2D system produces excitations with fractional statistics, and produces chiral quantum channels that propagate a quantized fractional number of qubits along the sample edge during each driving period. These phases share some common features with fractional quantum Hall states, but are sharply distinct dynamical phenomena. Unlike the integer-valued invariant characterizing the equilibrium quantum Hall conductance, these phases are characterized by a dynamical topological invariant that is a square root of a rational number, inspiring the label: radical chiral Floquet phases. We construct solvable models of driven and interacting spin systems with these properties, and identify an unusual bulk-boundary correspondence between the chiral edge dynamics and bulk "anyon time-crystal" order characterized by dynamical transmutation of electric-charge into magnetic-flux excitations in the bulk.
AbstractBose-Einstein correlations between identified charged pions are measured for p +Pb collisions at √{s_{NN}}=5.02 TeV using data recorded by the ATLAS detector at the CERN Large Hadron Collider corresponding to a total integrated luminosity of 28 nb^{-1}. Pions are identified using ionization energy loss measured in the pixel detector. Two-particle correlation functions and the extracted source radii are presented as a function of collision centrality as well as the average transverse momentum (k_{T}) and rapidity (y_{π}^{π ★}) of the pair. Pairs are selected with a rapidity -2 <y_{π}^{π ★}<1 and with an average transverse momentum 0.1 <k_{T}<0.8 GeV . The effect of jet fragmentation on the two-particle correlation function is studied, and a method using opposite-charge pair data to constrain its contributions to the measured correlations is described. The measured source sizes are substantially larger in more central collisions and are observed to decrease with increasing pair k_{T}. A correlation of the radii with the local charged-particle density is demonstrated. The scaling of the extracted radii with the mean number of participating nucleons is also used to compare a selection of initial-geometry models. The cross term R_{ol} is measured as a function of rapidity, and a nonzero value is observed with 5.1 σ combined significance for -1 <y_{π}^{π ★}<1 in the most central events.
AbstractA search for dark matter in association with a Higgs boson decaying to two photons is presented. This study is based on data collected with the ATLAS detector, corresponding to an integrated luminosity of 36.1 fb-1 of proton-proton collisions at the LHC at a center-of-mass energy of 13 TeV in 2015 and 2016. No significant excess over the expected background is observed. Upper limits at 95% confidence level are set on the visible cross section for beyond the Standard Model physics processes, and the production cross section times branching fraction of the Standard Model Higgs boson decaying into two photons in association with missing transverse momentum in three different benchmark models. Limits at 95% confidence level are also set on the observed signal in two-dimensional mass planes. Additionally, the results are interpreted in terms of 90% confidence-level limits on the dark-matter-nucleon scattering cross section, as a function of the dark-matter particle mass, for a spin-independent scenario.
AbstractThe results of a search for squarks and gluinos in final states with an isolated electron or muon, multiple jets and large missing transverse momentum using proton-proton collision data at a center-of-mass energy of √{s }=13 TeV are presented. The data set used was recorded during 2015 and 2016 by the ATLAS experiment at the Large Hadron Collider and corresponds to an integrated luminosity of 36.1 fb^{-1}. No significant excess beyond the expected background is found. Exclusion limits at 95% confidence level are set in a number of supersymmetric scenarios, reaching masses up to 2.1 TeV for gluino pair production and up to 1.25 TeV for squark pair production.
AbstractThe negatively charged silicon-vacancy (SiV- ) color center in diamond has recently emerged as a promising system for quantum photonics. Its symmetry-protected optical transitions enable the creation of indistinguishable emitter arrays and deterministic coupling to nanophotonic devices. Despite this, the longest coherence time associated with its electronic spin achieved to date (˜250 ns ) has been limited by coupling to acoustic phonons. We demonstrate coherent control and suppression of phonon-induced dephasing of the SiV- electronic spin coherence by 5 orders of magnitude by operating at temperatures below 500 mK. By aligning the magnetic field along the SiV- symmetry axis, we demonstrate spin-conserving optical transitions and single-shot readout of the SiV- spin with 89% fidelity. Coherent control of the SiV- spin with microwave fields is used to demonstrate a spin coherence time T2 of 13 ms and a spin relaxation time T1 exceeding 1 s at 100 mK. These results establish the SiV- as a promising solid-state candidate for the realization of quantum networks.
AbstractThe pseudogap metal phase of the hole-doped cuprate superconductors has two seemingly unrelated characteristics: a gap in the electronic spectrum in the "antinodal" region of the square lattice Brillouin zone and discrete broken symmetries. We present a SU(2) gauge theory of quantum fluctuations of magnetically ordered states which appear in a classical theory of square lattice antiferromagnets, in a spin-density wave mean field theory of the square lattice Hubbard model, and in a CP 1 theory of spinons. This theory leads to metals with an antinodal gap and topological order which intertwines with the observed broken symmetries.
AbstractA transient color flux across null infinity in classical Yang-Mills theory is considered. It is shown that a pair of test "quarks" initially in a color singlet generically acquire net color as a result of the flux. A nonlinear formula is derived for the relative color rotation of the quarks. For a weak color flux, the formula linearizes to the Fourier transform of the soft gluon theorem. This color memory effect is the Yang-Mills analog of the gravitational memory effect.
AbstractThe graphene/MoS2 heterojunction formed by joining the two components laterally in a single plane promises to exhibit a low-resistance contact according to the Schottky-Mott rule. Here we provide an atomic-scale description of the structural, electronic, and magnetic properties of this type of junction. We first identify the energetically favorable structures in which the preference of forming C-S or C-Mo bonds at the boundary depends on the chemical conditions. We find that significant non-carrier related charge transfer between graphene and undoped MoS2 is localized at the boundary. We show that the abundant 1D boundary states substantially pin the Fermi level in the lateral contact between graphene and MoS2, in close analogy to the effect of 2D interfacial states in the contacts between 3D materials. Furthermore, we propose specific ways in which these effects can be exploited to achieve spin-polarized currents.
AbstractWe propose and analyze a new method for quantum metrology based on stable non-equilibrium states of quantum matter. Our approach utilizes quantum correlations stabilized by strong interactions and periodic driving. As an example, we present an explicit protocol to perform Floquet enhanced measurements of an oscillating magnetic field in Ising-interacting spin systems. Our protocol allows one to circumvent the interaction-induced decoherence associated with high density spin ensembles and is robust to the presence of noise and imperfections. Applications to nanoscale magnetic sensing and precision measurements are discussed.
AbstractWe present experimental observations and a study of quantum dynamics of strongly interacting electronic spins, at room temperature in the solid state. In a diamond substrate, a single nitrogen vacancy (NV) center coherently interacts with two adjacent S = 1/2 dark electron spins. We quantify NV-electron and electron-electron couplings via detailed spectroscopy, with good agreement to a model of strongly interacting spins. The electron-electron coupling enables an observation of coherent flip-flop dynamics between electronic spins in the solid state, which occur conditionally on the state of the NV. Finally, as a demonstration of coherent control, we selectively couple and transfer polarization between the NV and the pair of electron spins. These results demonstrate a key step towards full quantum control of electronic spin registers in room temperature solids. go to Most Recent Faculty Publications |