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Results for “UNITARITY”

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At least 307 records · Page 17
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DOE OSTI2018

Enhanced di-Higgs boson production in the complex Higgs singlet model

Here, we consider the standard model (SM) extended by the addition of a complex scalar singlet, with no assumptions about additional symmetries of the potential. This model provides for resonant di-Higgs production of Higgs particles with different masses. We demonstrate that regions of parameter space allowed by precision electroweak measurements, experimental limits on single Higgs production, and perturbative unitarity allow for large di-Higgs production rates relative to the SM rates. In this scenario, the dominant production mechanism of the new scalar states is di-Higgs production. Results are presented for $\sqrt{s}$ = 13, 27 and 100 TeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Precision Measurement of the Ratio B(t{yields}Wb)/B(t{yields}Wq) and Extraction of V{sub tb}

We present a measurement of the ratio of top quark branching fractions R=B(t{yields}Wb)/B(t{yields}Wq), where q can be a d, s, or b quark, in the lepton+jets and dilepton tt final states. The measurement uses data from 5.4 fb{sup -1} of pp collisions collected with the D0 detector at the Fermilab Tevatron Collider. We measure R=0.90{+-}0.04, and we extract the Cabibbo-Kobayashi-Maskawa (CKM) matrix element |V{sub tb}| as |V{sub tb}|=0.95{+-}0.02, assuming unitarity of the 3x3 CKM matrix.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Onset of a Pseudogap Regime in Ultracold Fermi Gases

We show, using an ab initio approach based on Quantum Monte Carlo technique, that the pseudogap regime emerges in ultracold Fermi gases close to the unitary point. We locate the onset of this regime at a value of the interaction strength corresponding to (k{sub F}a){sup -1}{approx_equal}-0.05 (a--scattering length). We determine the evolution of the gap as a function of temperature and interaction strength in the Fermi gas around the unitary limit and show that our results exhibit a remarkable agreement with the recent wave-vector resolved radio frequency spectroscopy data. Our results indicate that a finite temperature structure of the Fermi gas around unitarity is more complicated and involves the presence of the phase with preformed Cooper pairs, which, however, do not contribute to the long range order.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

Lattice QCD Calculation of Electroweak Box Contributions to Superallowed Nuclear and Neutron Beta Decays

We present the first lattice QCD calculation of the universal axial γ W -box contribution □ γ W V A to both superallowed nuclear and neutron beta decays. This contribution emerges as a significant component within the theoretical uncertainties surrounding the extraction of | V u d | from superallowed decays. Our calculation is conducted using two domain wall fermion ensembles at the physical pion mass. To construct the nucleon four-point correlation functions, we employ the random sparsening field technique. Furthermore, we incorporate long-distance contributions to the hadronic function using the infinite-volume reconstruction method. Upon performing the continuum extrapolation, we arrive at □ γ W V A = 3.65 ( 7 ) lat ( 1 ) PT × 10 − 3 . Consequently, this yields a slightly higher value of | V u d | = 0.973 86 ( 11 ) exp ( 9 ) RC ( 27 ) NS , reducing the previous 2.1 σ tension with the CKM unitarity to 1.8 σ . Additionally, we calculate the vector γ W -box contribution to the axial charge g A , denoted as □ γ W V V , and explore its potential implications. Published by the American Physical Society 2024

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Universal Phase Diagram and Scaling Functions of Imbalanced Fermi Gases

We discuss the phase diagram and the universal scaling functions of attractive Fermi gases at finite imbalance. The existence of a quantum multicritical point for the unitary gas at vanishing chemical potential μ and effective magnetic field h, first discussed by Nikolić and Sachdev, gives rise to three different phase diagrams, depending on whether the inverse scattering length 1/a is negative, positive or zero. Within a Luttinger–Ward formalism, the phase diagram and pressure of the unitary gas is calculated as a function of the dimensionless scaling variables T/μ and h/μ. The results indicate that beyond the Clogston–Chandrasekhar limit at (h/μ){sub c} ≃ 1.09, the unitary gas exhibits an inhomogeneous superfluid phase with FFLO order that can reach critical temperatures near unitarity of ≃0.03T{sub F }.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2011

Check of the gluon-reggeization condition in the next-to-leading order: Quark part

The bootstrap condition for gluon production in multi-Regge kinematics is considered in the next-to-leading order. Bootstrap conditions follow fromthe requirement that the Regge formof amplitudes in QCD be consistent with s-channel unitarity and are nonlinear relations between the Reggeized-gluon trajectory and vertex functions. Their fulfillment ensures the Reggeization of gluons-that is, the Regge form of both elastic and inelastic amplitudes. This condition is the only one that has not yet been verified. The demonstration of its fulfillment is the ultimate step in proving the Reggeization of gluons in the next-to-leading logarithmic approximation. In the present article, this is done for the quark part of the bootstrap condition.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

The influence of pairing correlations on the isospin symmetry breaking corrections of superallowed Fermi beta decays

Within the framework of quasi-particle random phase approximation, the isospin breaking correction of superallowed 0{sup +} {yields} 0{sup +} beta decay and unitarity of Cabibbo-Kobayashi-Maskawa mixing matrix have been investigated. The broken isotopic symmetry of nuclear part of Hamiltonian has been restored by Pyatov's method. The isospin symmetry breaking correction with pairing correlations has been compared with the previous results without pairing. The effect of pairing interactions has been examined for nine superallowed Fermi beta decays; their parent nuclei are {sup 26}Al, {sup 34}Cl, {sup 38}K, {sup 42}Sc, {sup 46}V, {sup 50}Mn, {sup 54}Co, {sup 62}Ga, {sup 74}Rb.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2013

Elastic scattering of hadrons outside the diffraction cone

The model-independent solution of the s-channel unitarity condition for the imaginary part of the hadronic elastic scattering amplitude outside the diffraction peak allows to make conclusions about the shape of the differential cross sections in this region. The eigensolution of the homogeneous linear integral equation and the iterative solutions of the inhomogeneous equation with different assumptions about the behavior of the overlap function and the real part of the amplitude are presented. The properties of the overlap function and of the ratio of the real-to-imaginary part of the amplitude are discussed. In particular, it is explicitly shown that the ratio changes its sign at a definite value of the transferred momentum. Some comments concerning the present day experimental results about the behavior of the differential cross section of elastic scattering outside the diffraction cone are given.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Some problems in heavy-quarkonium decays

Problems proposed by the present authors for studies at c-τ, b, super-c-τ, and super-b factories are formulated. First, a comparison of the mechanisms of light-scalar-meson production in the process D{sub s}{sup +}→ss̄e{sup +}ν→[σ(600)+f{sub 0}(980)]e{sup +}ν→π{sup +}π{sup −}e{sup +}ν with the mechanisms of light-pseudoscalar-meson production in the process D{sub s}{sup +}→ss̄e{sup +}ν→(η/η{sup ′})e{sup +}ν reveals that the transition ss̄→σ(600) is negligible in relation to the transition ss̄→f{sub 0}(980). As for f{sub 0}(980), ss̄→f{sub 0}(980) is not more than 30% of ss̄→η{sub s}(η{sub s}=ss̄). It is proposed to study light scalar mesons in the semileptonic decays of D{sup +}(D{sup −}) D{sup 0}(D̄{sup 0}), B{sup +}(B{sup −}), and B{sup 0}(B̄{sup 0}). Second, interference phenomena observed in the ψ(3770)-resonance region in the reaction e{sup +}e{sup −}→DD̄ are described on the basis of models satisfying the elastic-unitarity requirement. As a model, we propose the model of mixed ψ(3770) and ψ(2S) resonances. In order to select theoretical models, it is proposed to employ non-DD̄ decay channels such as e{sup +}e{sup −} → ψ(3770) → γχ{sub c0}, J/ψη, and ϕη. Third, branching ratios are calculated for ψ(3770) and ϒ(10580) decays proceeding to light (non-DD̄ and non-BB̄) hadrons owing to the contributions of real DD̄ and BB̄ intermediate states. The predictions obtained for these branching ratios lie in the range of 1% ≲ BR ≲ 15%. The lower boundary of this range is ten times higher than the branching ratio for annihilation to three gluons.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Determinations of Vus using inclusive hadronic τ decay data

Two methods for determining |V us | employing inclusive hadronic ττ decay data are discussed. The first is the conventional flavor-breaking sum rule determination whose usual implementation produces results ~3σ low compared to three-family unitary expectations. The second is a novel approach combining experimental strange hadronic ττ distributions with lattice light-strange current–current two-point function data. In preliminary explorations of the latter show the method promises |V us | determinations are competitive with those from K ℓ3 and Γ[π μ2 ]/Γ[π μ2 ]. For the former, systematic issues in the conventional implementation are investigated. Unphysical dependences of |V us | on the choice of sum rule weight, w, and upper limit, s 0 , of the weighted experimental spectral integrals are observed, the source of these problems identified and a new implementation which overcomes these problems developed. The lattice results are shown to provide a tool for quantitatively assessing truncation uncertainties for the slowly converging D=2 OPE series. Our results for |V us | from this new implementation are shown to be free of unphysical w- and s0-dependences, and ~0.0020 higher than those produced by the conventional implementation. With preliminary new Kπ branching fraction results as input, we find |V us | in excellent agreement with that obtained from K ℓ3 , and compatible within errors with expectations from three-family unitarity.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Testing Lepton Flavor Universality with Pion, Kaon, Tau, and Beta Decays

We present an overview of searches for violation of lepton flavor universality with a focus on low energy precision probes using π, K, τ, and nuclear beta decays. We review the current experimental results, summarize the theoretical status within the context of the Standard Model, and discuss future prospects (both experimental and theoretical). We review the implications of these measurements for physics beyond the Standard Model by performing a global model-independent fit to modified W couplings to leptons and four-fermion operators. We also discuss new physics in the context of simplified models and review Standard Model extensions with a focus on those that can explain a possible deviation from unitarity of the Cabibbo–Kobayashi–Maskawa quark mixing matrix.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Search for b-->u transitions in B- --> DK- and B- --> D*K- Decays

We report results from an updated study of the suppressed decays B{sup -} --> DK{sup -} and B{sup -} --> D*K{sup -} followed by D --> K{sup +}{pi}{sup -}, where D{sup (*)} indicates a D{sup (*)0} or a {anti D}{sup (*)0} meson, and D{sup *} --> D{tau}{sup 0} or D{sup *} --> D{gamma}. These decays are sensitive to the CKM unitarity triangle angle {gamma} due to interference between the b --> c transition B{sup -} --> D{sup (*)0}K{sup -} followed by the double Cabibbo-suppressed decay D{sup 0} --> K{sup +}{pi}{sup -}, and the b --> u transition B{sup -} --> {anti D}{sup (*)0}K{sup -} followed by the Cabibbo-favored decay {anti D}{sup 0} --> K{sup +}{pi}{sup -}. We also report an analysis of the decay B{sup -} --> D{sup (*)}{pi}{sup -} with the D decaying into the doubly Cabibbo-suppressed mode D --> K{sup +}{pi}{sup -}. Our results are based on 467 million {Upsilon}(4S) --> B{anti B} decays collected with the BABAR detector at SLAC. We measure the ratios R{sup (*)} of the suppressed ([K{sup +}{pi}{sup -}]{sub D}K{sup -}/{pi}{sup -}) to favored ([K{sup -}{pi}{sup +}]{sub D}K{sup -}/{pi}{sup -}) branching fractions as well as the CP asymmetries A{sup (*)} of those modes. We see indications of signals for the B{sup -} --> DK{sup -} and B{sup -} --> D{sup *}{sub D{pi}{sup 0}}K{sup -} suppressed modes, with statistical significances of 2.1 and 2.2{sigma}, respectively, and we measure: R{sub DK} = (1.1 {+-} 0.6 {+-} 0.2) x 10{sup -2}, A{sub DK} = -0.86 {+-} 0.47 {sup +0.12}{sub -0.16}, R{sup *}{sub (D{pi}{sup 0})K} = (1.8 {+-} 0.9 {+-} 0.4) x 10{sup -2}, A{sup *}{sub (D{pi}{sup 0})K} = +0.77 {+-} 0.35 {+-} 0.12, R{sup *}{sub (D{gamma})K} = (1.3 {+-} 1.4 {+-} 0.8) x 10{sup -2}, A{sup *}{sub (D{gamma})K} = +0.36 {+-} 0.94 {sup +0.25}{sub -0.41}, where the first uncertainty is statistical and the second is systematic. we use a frequentist approach to obtain the magnitude of the ratio r{sub B} {equivalent_to} {vert_bar}A(B{sup -} --> {anti D}{sup 0}K{sup -})/A(B{sup -} --> D{sup 0}K{sup -}){vert_bar} = (9.5{sup +5.1}{sub -4.1})%, with r{sub B} < 16.7% at 90% confidence level. In the case of B{sup -} --> D{sup *}K{sup -} we find r{sup *}{sub B} {equivalent_to} {vert_bar}A(B{sup -} --> {anti D}{sup *0}K{sup -})/A(B{sup -} --> D{sup *0}K{sup -}){vert_bar} = (9.6{sup +3.5}{sub 5.1})%, with r{sup *}{sub B} < 15.0% at 90% confidence level.

43 PARTICLE ACCELERATORS↗
DOE OSTI2011

CKM-UT Angles: Mixing And CP Violation at the B Factories

We review the experimental status of the angles of the Unitarity Triangle of the CKM matrix, as measured by the BABAR and Belle experiments. The B Factories have demonstrated since the beginning of this decade that CP violation in the B meson system is consistent with the Standard Model (SM) description in terms of the complex phase in the three-by-three Cabibbo-Kobayashi-Maskawa (CKM) matrix. With one single phase, the SM predicts clear patterns for quark mixing and CP violations, to be satisfied by all processes.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Recent Results on Semileptonic Decays at Babar

Some recent BABAR results on semileptonic decays are presented. They focus on the determination of the CKM matrix elements |V{sub ub}| and |V{sub cb}| in inclusive and exclusive b {yields} u{ell}v and b {yields} c{ell}v decays, and on form factors measurement in exclusive c {yields} s{ell}v decays. Semileptonic decays play a crucial role in the determination of the unitarity triangle parameters: decays of the b quark give access to the CKM matrix elements |V{sub ub}| and |V{sub cb}|, while charm decays provide a way to validate lattice QCD computations through form factors measurements. Such calculations provide theoretical inputs that are used, especially, in the b sector. A lot of new results have been obtained by the BABAR collaboration during the last years, thanks to the large b{bar b} and c{bar c} production cross-sections and to the large recorded statistics. Some of these measurements are presented here.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

Semileptonic B to D Decays at Nonzero Recoil with 2+1 Flavors of Improved Staggered Quarks

The Fermilab Lattice-MILC collaboration is completing a comprehensive program of heavy-light physics on the MILC (2+1)-flavor asqtad ensembles with lattice spacings as small as 0.045 fm and light-to-strange-quark mass ratios as low as 1/20. We use the Fermilab interpretation of the clover action for heavy valence quarks and the asqtad action for light valence quarks. The central goal of the program is to provide ever more exacting tests of the unitarity of the CKM matrix. We give a progress report on one part of the program, namely the analysis of the semileptonic decay B to D at both zero and nonzero recoil. Although final results are not presented, we discuss improvements in the analysis methods, the statistical errors, and the parameter coverage that we expect will lead to a significant reduction in the final error for |V{sub cb}| from this decay channel.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

B and D meson decay constants from 2+1 flavor improved staggered simulations

We give an update on simulation results for the decay constants f{sub B}; f{sub B{sub s}}, f{sub D} and f{sub D{sub s}}. These decay constants are important for precision tests of the standard model, in particular entering as inputs to the global CKM unitarity triangle fit. The results presented here make use of the MILC (2+1)-flavor asqtad ensembles, with heavy quarks incorporated using the clover action with the Fermilab method. Partially quenched, staggered chiral perturbation theory is used to extract the decay constants at the physical point. In addition, we give error projections for a new analysis in progress, based on an extended data set.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Results From B Factories

Recent results from B factories are reviewed. A summary of measurements related to the angles and sides of the CKM Unitarity Triangle is shown. Measurements of rare B decays, sensitive to new physics processes, as well as the recent evidence for neutral D meson mixing, are also reported.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Hartree-Fock-Bogoliubov solution of the pairing Hamiltonian in finite nuclei

We present an overview of the Hartree-Fock-Bogoliubov (HFB) theory of nucleonic superfluidity for finite nuclei. After introducing basic concepts related to pairing correlations, we show how the correlated pairs are incorporated into the HFB wave function. Thereafter, we present derivation and structure of the HFB equations within the superfluid nuclear density functional formalism and discuss several aspects of the theory, including the unitarity of the Bogoliubov transformation in truncated single-particle and quasiparticle spaces, form of the pairing functional, structure of the HFB continuum, regularization and renormalization of pairing fields, and treatment of pairing in systems with odd particle numbers.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗