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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 325 records · Page 18
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DOE OSTI2011

Ground state and excitations of a Bose gas: From a harmonic trap to a double well

We determine the low-energy properties of a trapped Bose gas split in two by a potential barrier over the whole range of barrier heights and asymmetry between the wells. For either weak or strong coupling between the wells, our two-mode theory yields a two-site Bose-Hubbard Hamiltonian with the tunneling, interaction, and bias parameters calculated simply using an explicit form of two mode functions. When the potential barrier is relatively low, most of the particles occupy the condensate mode and our theory reduces to a two-mode version of the Bogoliubov theory, which gives a satisfactory estimate of the spatial shape and energy of the lowest collective excitation. When the barrier is high, our theory generalizes the standard two-site Bose-Hubbard model into the case of asymmetric modes, and correctly predicts a full separation of the modes in the limit of strong separation of the wells. We provide explicit analytic forms for the number squeezing and coherence as a function of particle number and temperature. We compare our theory to other two-mode theories for bosons in a double well and discuss their validity in different parameter regimes.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Updated constraints on self-interacting dark matter from Supernova 1987A

Here we revisit SN1987A constraints on light, hidden sector gauge bosons (“dark photons”) that are coupled to the standard model through kinetic mixing with the photon. These constraints are realized because excessive bremsstrahlung radiation of the dark photon can lead to rapid cooling of the SN1987A progenitor core, in contradiction to the observed neutrinos from that event. The models we consider are of interest as phenomenological models of strongly self-interacting dark matter. We clarify several possible ambiguities in the literature and identify errors in prior analyses. We find constraints on the dark photon mixing parameter that are in rough agreement with the early estimates of Dent et al. [arXiv:1201.2683.], but only because significant errors in their analyses fortuitously canceled. Our constraints are in good agreement with subsequent analyses by Rrapaj & Reddy [Phys. Rev. C 94, 045805 (2016).] and Hardy & Lasenby [J. High Energy Phys. 02 (2017) 33.]. We estimate the dark photon bremsstrahlung rate using one-pion exchange (OPE), while Rrapaj & Reddy use a soft radiation approximation (SRA) to exploit measured nuclear scattering cross sections. We find that the differences between mixing parameter constraints obtained through the OPE approximation or the SRA approximation are roughly a factor of ~2–3. Hardy & Laseby [J. High Energy Phys. 02 (2017) 33.] include plasma effects in their calculations finding significantly weaker constraints on dark photon mixing for dark photon masses below ~10 MeV. We do not consider plasma effects. Lastly, we point out that the properties of the SN1987A progenitor core remain somewhat uncertain and that this uncertainty alone causes uncertainty of at least a factor of ~2–3 in the excluded values of the dark photon mixing parameter. Further refinement of these estimates is unwarranted until either the interior of the SN1987A progenitor is more well understood or additional, large, and heretofore neglected effects, such as the plasma interactions studied by Hardy & Lasenby [J. High Energy Phys. 02 (2017) 33.], are identified.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

On the renormalization of nucleon-nucleon interaction by one rho-meson exchange

The nature of the nucleon-nucleon interaction has always been a subject of intense discussion in the low-energy hadron physics literature. In the last decades, the research related to chiral perturbation theory developed by Gasser, Leutwyler and Weinberg have gained attention due to the advances in using chiral symmetry to describe nuclear interactions. In this work we discuss aspects of the renormalizability of the interaction between two nucleons by one ρ and one π mesons exchange. The results give us important hints on the required short-distance cancellations of the singular tensor potential due to pion exchange.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Constraints on supersymmetric dark matter for heavy scalar superpartners

Here we study the constraints on neutralino dark matter in minimal low energy supersymmetry models and the case of heavy lepton and quark scalar superpartners. For values of the Higgsino and gaugino mass parameters of the order of the weak scale, direct detection experiments are already putting strong bounds on models in which the dominant interactions between the dark matter candidates and nuclei are governed by Higgs boson exchange processes, particularly for positive values of the Higgsino mass parameter mu. For negative values of mu, there can be destructive interference between the amplitudes associated with the exchange of the standard CP-even Higgs boson and the exchange of the nonstandard one. This leads to specific regions of parameter space which are consistent with the current experimental constraints and a thermal origin of the observed relic density. In this article, we study the current experimental constraints on these scenarios, as well as the future experimental probes, using a combination of direct and indirect dark matter detection and heavy Higgs and electroweakino searches at hadron colliders

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

On the control of spin-boson systems

In this paper, we study the so-called spin-boson system, namely, a two-level system in interaction with a distinguished mode of a quantized bosonic field. We give a brief description of the controlled Rabi and Jaynes–Cummings models and we discuss their appearance in the mathematics and physics literature. We then study the controllability of the Rabi model when the control is an external field acting on the bosonic part. Applying geometric control techniques to the Galerkin approximation and using perturbation theory to guarantee non-resonance of the spectrum of the drift operator, we prove approximate controllability of the system, for almost every value of the interaction parameter.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2012

Contraction of electroweak model and neutrino

The electroweak model, which lepton sector correspond to the contracted gauge group SU(2; j) Multiplication-Sign U(1), j {yields} 0, whereas boson and quark sectors are standard one, is suggested. The field space of the model is fibered under contraction in such a way that neutrino fields are in the fiber and all other fields are in the base. Properties of the fibered field space are understood in context of semi-Riemannian geometry. This model describes in a natural manner why neutrinos so rarely interact with matter, as well as why neutrino cross section increase with the energy. Dimensionfull parameter of the model is interpreted as neutrino energy. Dimensionless contraction parameter j at low energy is connected with the Fermi constant of weak interactions and is approximated as j{sup 2} Almost-Equal-To 10{sup -5}.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Gamma ray tests of Minimal Dark Matter

We reconsider the model of Minimal Dark Matter (a fermionic, hypercharge-less quintuplet of the EW interactions) and compute its gamma ray signatures. We compare them with a number of gamma ray probes: the galactic halo diffuse measurements, the galactic center line searches and recent dwarf galaxies observations. We find that the original minimal model, whose mass is fixed at 9.4 TeV by the relic abundance requirement, is constrained by the line searches from the Galactic Center: it is ruled out if the Milky Way possesses a cuspy profile such as NFW but it is still allowed if it has a cored one. Observations of dwarf spheroidal galaxies are also relevant (in particular searches for lines), and ongoing astrophysical progresses on these systems have the potential to eventually rule out the model. We also explore a wider mass range, which applies to the case in which the relic abundance requirement is relaxed. Most of our results can be safely extended to the larger class of multi-TeV WIMP DM annihilating into massive gauge bosons.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Aspects of nonlinear effect on black hole superradiance

Under some conditions, light boson fields grow exponentially around a rotating black hole, called the superradiance instability. We discuss effects of nonlinear interactions of the boson on the instability. In particular, we focus on the effect of the particle production and show that the growth of the boson cloud may be saturated much before the black hole spin is extracted by the boson cloud, while the nonlinear interactions also induce the boson emission. For application, we revisit the superradiant instability of the standard model photon, axion and hidden photon.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2012

Searches for BSM and Higgs boson at LHC

This article reviews the recent results from the two energy frontier experiments, ATLAS and CMS at the large hadron collider (LHC), using the data collected during 2011 corresponding up to 4.9 fb{sup -1} integrated luminosity of {radical}(s) = 7TeV proton proton collisions. The recent results of searches for the Standard Model Higgs boson, and searches for beyond Standard Model physics based on supersymmetry and other new exotic models are presented.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Landau-Zener extension of the Tavis-Cummings model: Structure of the solution

We explore the recently discovered solution of the driven Tavis-Cummings model (DTCM). It describes interaction of an arbitrary number of two-level systems with a bosonic mode that has linearly time-dependent frequency. We derive compact and tractable expressions for transition probabilities in terms of the well-known special functions. In this form, our formulas are suitable for fast numerical calculations and analytical approximations. As an application, we obtain the semiclassical limit of the exact solution and compare it to prior approximations. Furthermore, we also reveal connection between DTCM and q -deformed binomial statistics.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2019

FCC-ee: The Lepton Collider

Particle physics has arrived at an important moment of its history. The discovery of the Higgs boson, with a mass of 125 GeV, completes the matrix of particles and interactions that has constituted the “Standard Model” for several decades. This model is a consistent and predictive theory, which has so far proven successful at describing all phenomena accessible to collider experiments. On the other hand, several experimental facts do require the extension of the Standard Model and explanations are needed for observations such as the domination of matter over antimatter, the evidence for dark matter and the non-zero neutrino masses. Theoretical issues that need to be addressed include the hierarchy problem, the neutrality of the Universe, the stability of the Higgs boson mass upon quantum corrections and the strong CP problem. This report contains the description of a novel research infrastructure based on a highest-luminosity energy frontier electron-positron collider (FCC-ee) to address the open questions of modern physics. It will be a general precision instrument for the continued in-depth exploration of nature at the smallest scales, optimised to measure precisely the properties of the Higgs boson at the per-cent level, the Z and W bosons, the top quark and the Higgs coupling to the Z at the per-mil level. FCC-ee will provide unprecedented sensitivity to signs of new physics appearing either in the form of small deviations from the Standard Model or as rare decay processes. This collider will be implemented in stages, successively spanning the entire energy range from the Z pole over the WW threshold and H production peak to the t"t" ̅ threshold. Most of the infrastructure (e.g. underground structures, surface sites, electrical distribution, cooling & ventilation, RF systems) can be directly re-used for a subsequent highest-energy hadron collider (described in the FCC conceptual design report volume 3), serving the world-wide particle-physics community in a highly synergetic and cost-effective manner throughout the 21st century. The European Strategy for Particle Physics (ESPP) update 2013 stated “To stay at the forefront of particle physics, Europe needs to be in a position to propose an ambitious post-LHC accelerator project at CERN by the time of the next Strategy update”. The FCC study has implemented the ESPP recommendation by developing a long-term vision for an “accelerator project in a global context”. This document describes the detailed design and preparation of a construction project for a post-LHC circular lepton collider “in collaboration with national institutes, laboratories and universities worldwide”, and enhanced by a strong participation of industrial partners. Now, a coordinated preparation effort can be based on a core of an ever-growing consortium of already more than 135 institutes worldwide. The technology for constructing a high-energy, highest-luminosity circular lepton collider exists today. The FCC-ee concept comprises a power-saving twin-aperture magnet system, a continuous top-up injection scheme for stable operation and maximum integrated luminosity. Combined with an energy staging scheme, the FCC-ee represents the most efficient and most sustainable route for executing the research required to discover signs of new physics beyond the Standard Model. The step-wise energy increase of the FCC-ee does not require any additional civil engineering activities. Strategic R&D for FCC-ee aims at minimising construction cost and energy consumption, while maximising the socio-economic impact. It will mitigate residual technology-related risks and ensure that industry can benefit from an acceptable economic utility. Concerning the implementation, a preparatory phase of about eight years is both necessary and adequate to establish the project governance and organisation structures, building the international machine and experiment consortia, developing a territorial implementation plan in agreement with the host-states’ requirements, optimising the disposal of land and underground volumes and preparing the civil engineering project. Such a large-scale, international fundamental research infrastructure, tightly involving industrial partners and providing training at all education levels, will be a strong motor of economic and societal development in all participating nations. The FCC study has implemented a set of actions towards a coherent vision for the world-wide high-energy and particle physics community, providing a collaborative framework for topically complementary and geographically well-balanced contributions. This conceptual design report lays the foundation for a subsequent infrastructure preparatory and technical design phase.

43 PARTICLE ACCELERATORS↗
DOE OSTI2017

Study of direct photon production with heavy flavor jets in $p\overline{p}$ collisions at $\sqrt{s}=1.96$ TeV with DZero detector

In hadronic collisions, photons ($\gamma$) with high energies emerge unaltered from the hard parton-parton interaction and therefore provide a clean probe of the underlying hard-scattering dynamics. Photons produced in these interactions (called direct or prompt) in association with one or more bottom ($b$)-quark jets provide an important test of perturbative Quantum Chromodynamics (QCD) predictions at large hard-scattering scales $Q$ and over a wide range of parton momentum fractions. In addition, the study of these processes also provides information about the parton density functions of $b$ quarks and gluons ($g$), which still have substantial uncertainties. In $p\bar{p}$ collisions, \gb-jet events are produced primarily through the Compton process $gb\to \gamma b$, which dominates for low and moderate photon transverse momenta ($\Ptg$), and through quark-antiquark anni hilation followed by $g \to b\bar{b}$ gluon splitting $q\bar{q}\to \gamma g \to \gamma b\bar{b}$, which dominates at high $\Ptg$. The final state with $b$-quark pair production, $p\bar{p} \rightarrow \gamma+b\bar{b}$, is mainly produced via $q\bar{q}\to \gamma b\bar{b}$ and $gg\to \gamma b\bar{b}$ scatterings. The $\gamma+2~b$-jet process is a crucial component of background in measurements of, for example, $t\bar{t} \gamma$ coupling and in some searches for new phenomena.\\ This thesis presents the first measurements of the differential cross section ${\rm d}\sigma/{\rm d}\Ptg$ for the production of an isolated photon in association with at least two $b$-quark jets. The ratio of differential production cross sections for $\gamma+2~b$-jets to $\gamma+b$-jet as a function of \ptg is also presented. The measurement of the ratio of cross sections leads to cancellation of various experimental and theoretical uncertainties, allowing a more precise comparison with the theoretical predictions. The results are based on the proton-antiproton ! collision data corresponding to an integrated luminosity of $8.7$~fb$^{-1}$ at $\sqrt{s}=$1.96~\TeV collected with the \DO detector at the Fermilab Tevatron Collider. %In this measurement, we follow an inclusive approach by allowing the final state with any additional jet(s) on top of the studied $b$-quark jets. Inclusive $\gamma+2~b$-jet production may also originate from partonic subprocesses involving parton fragmentation into a photon. However, photon isolation requirements significantly reduces the contributions from such processes. The large data sample and use of advanced photon and $b$-jet identification tools enable us to measure the $\gamma+2~b$-jet production cross section differentially as a function of $\Ptg$. This allows for probing the dynamics of the production process over a wide kinematic range not studied before in other measurements of a vector boson + $b$-jet final state. The measured cross sections and their ratios are compared to the NLO perturbative Q CD calculations as well as predictions based on the $k_{\rm T}$-factorization approach and those from the {\sc sherpa} and {\sc pythia} Monte Carlo event generators. We also measure the ratio of cross sections, $\sigma(p\bar{p}\rightarrow Z+2~b~\text{jets})$/$\sigma(p\bar{p}\rightarrow Z+\text{2~jets})$, for associated production of a $Z$ boson with at least two jets. This measurement uses data corresponding to an integrated luminosity of 9.7 fb$^{-1}$ collected by the \DO experiment. The measured integrated ratio is in agreement with predictions from NLO perturbative QCD and the Monte Carlo event generators {\sc alpgen} and {\sc pythia}. A good theoretical description of this process is essential since it forms a major background for a variety of physics processes, including standard model Higgs boson production in association with a $Z$ boson, $ZH(H\rightarrow b\bar{b})$, and searches for supersymmetric partners of the $b$ quark. These results will improve our theoretical understanding as we search for phenomena beyond the standard! model us! ing the data from similar collider experiments in the case where the final states of the interaction involved the production of vector bosons in association with two $b$-quark jets.\\ This work has been done in collaboration with \DO experiment but the analyses and results presented in this thesis are my contribution.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Prediction of narrow N* and {Lambda}* with hidden charm

The interaction between various charmed mesons and charmed baryons, such as D-bar{Sigma}{sub c}-D-bar{Lambda}{sub c}, D-bar*{Sigma}{sub c}-D-bar*{Lambda}{sub c}, and related strangeness channels, are studied within the framework of the coupled channel unitary approach with the local hidden gauge formalism. Six narrow N* and {Lambda}* resonances are dynamically generated with mass above 4 GeV and width smaller than 100 MeV. These predicted new resonances definitely cannot be accommodated by quark models with three constituent quarks. We make estimates of production cross sections of these predicted resonances in p-barp collisions for PANDA at the forthcoming FAIR facility.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Results of a higgs boson searches in the ATLAS and CMS experiments at the large hadron collider at energies 7 and 8 TeV

Recent achievements of the ATLAS and CMS experiments at the Large Hadron Collider searching for a Higgs boson are summarized. A new particle with the mass of 125 GeV and properties expected for the Standard Model Higgs boson was discovered three years ago in these experiments in proton-proton collisions when analyzing part of the data taken at the centre-of-mass energies 7 TeV and 8 TeV in 2011 and 2012 year exposures. Today all the data are processed and fully analyzed. Experimental results of studies of individual Higgs boson decay channels as well as their combination to extract such properties as mass, signal strength, coupling constants, spin and parity are reviewed. All experimental results are found to be compatible with the Standard Model predictions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Photoproduction of the rho meson and its magnetic moments

We study photoproduction of {rho} meson in a model of hidden local symmetry. We introduce the {rho} meson on a hidden gauge boson and phenomenological {rho} meson-nucleon Lagrangian is constructed respecting chiral symmetry. It turns out that the {sigma}-exchange interaction plays an important role in neutral {rho} meson photoproduction to reproduce the experimental cross sections. In charged {rho} meson photoproduction, the model takes into account the {rho} meson magnetic moments from the three-point vertex in the kinetic terms. We show that the magnetic moment of the charged {rho} meson has a significant effect on the total cross sections in proportion to the photon energies.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

II. The standard model in the isotopic Foldy-Wouthuysen representation without higgs bosons in the fermion sector

The Standard Model with massive fermions is formulated in the isotopic Foldy-Wouthuysen representation. SU (1) × U (1) — invariance of the theory in this representation is independent of whether fermions possess mass or not, and, consequently, it is not necessary to introduce interactions between Higgs bosons and fermions. The study discusses a possible relation between spontaneous breaking of parity in the isotopic Foldy-Wouthuysen representation and the composition of elementary particles of “dark matter”.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Hadron collider potential for excited bosons search

The e {sup +} e {sup −} and μ{sup +}μ{sup −} dilepton final states are the most clear channels for a new heavy neutral resonance search. Their advantage is that usually in the region of expected heavy-mass resonance peak the main irreducible background, from the Standard Model Drell-Yan process, contributes two orders of magnitude smaller than the signal. In this paper we consider the future prospects for search for the excited neutral Z*-bosons. The bosons can be observed as a Breit-Wigner resonance peak in the dilepton invariant mass distributions in the same way as the well-known extra gauge Z′ bosons. However, the Z* bosons have unique signatures in transverse momentum, angular and pseudorapidity distributions of the final leptons, which allow to distinguish them from the other heavy neutral resonances. At present only the ATLAS Collaboration has looked for such new excitations at the Large Hadron Collider and has published its results for 7 TeV collision energy. After successful comparison of our evaluation with these official results we present our estimations for the discovery potential and the exclusion limits on the Z*-boson search in pp collisions at higher centre-of-mass energies and different luminosities. In particular, LHC Run 2 can discover Z*-boson with its mass up to 5.3 TeV, while the High Luminosity LHC can extend that reach to 6.2 TeV. The High Energy LHC (with collision energy of 33 TeV) will be able to probe two times heavier resonance masses at the same integrated luminosities.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Search for Dark Matter in Events with a Hadronically Decaying W or Z Boson and Missing Transverse Momentum in p p Collisions at s = 8 TeV with the ATLAS Detector

A search is presented for dark matter pair production in association with a W or Z boson in pp collisions representing 20.3 fb -1 of integrated luminosity at $ \sqrt{s} $ = 8 TeV using data recorded with the ATLAS detector at the Large Hadron Collider. Events with a hadronic jet with the jet mass consistent with a W or Z boson, and with large missing transverse momentum are analyzed. The data are consistent with the standard model expectations. Limits are set on the mass scale in effective field theories that describe the interaction of dark matter and standard model particles, and on the cross section of Higgs production and decay to invisible particles. In addition, cross section limits on the anomalous production of W or Z bosons with large missing transverse momentum are set in two fiducial regions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗