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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Spontaneous CP violation and horizontal symmetry in the MSSM: toward lepton flavor naturalness

We study the contributions of supersymmetric models with a U(1) horizontal symmetry and only spontaneous CP breaking to various lepton flavor observables, such as μ → eγ and the electron electric dipole moment. We show that both a horizontal symmetry and a lack of explicit CP violation can alleviate the existing bounds from such observables. The undetermined \( \mathcal{O} \) (1) coefficients in such mass matrix models muddle the interpretation of the bounds from various flavor observables. To overcome this, we define a new fine-tuning measure for different observables in such setups. This allows us to study how naturally the observed IR flavor observables can emerge from a given mass matrix model. We use our flavor-naturalness measure in study of our supersymmetric models and quantify the degree of fine tuning required by the bounds from various lepton flavor observables at each mass scale of sleptons, neutralinos, and charginos.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2010

Precision Measurement of CP Violation in $D^0\to\pi^+\pi^-$ at CDF

We report a preliminary measurement of the CP violating asymmetry in D{sup 0} {yields} {pi}{sup +}{pi}{sup -} using approximately 215,000 decays reconstructed in about 5.94/fb of CDF data. We use the strong D* {+-} D{sup 0}{pi}{sup +} decay (D* tag) to identify the flavor of the charmed meson at production time and exploit CP-conserving strong c-{bar c} pair-production in p-{bar p} collisions. Higher statistic samples of Cabibbo-favored D{sup 0} {yields} K{sup -}{pi}{sup +} decays with and without D* tag are used to highly suppress systematic uncertainties due to detector effects. The result is the world's most precise measurement to date.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Probing CP violation in $h\rightarrow\gamma\gamma$ with converted photons

We study Higgs diphoton decays, in which both photons undergo nuclear conversion to electron- positron pairs. The kinematic distribution of the two electron-positron pairs may be used to probe the CP violating (CPV) coupling of the Higgs to photons, that may be produced by new physics. Detecting CPV in this manner requires interference between the spin-polarized helicity amplitudes for both conversions. We derive leading order, analytic forms for these amplitudes. In turn, we obtain compact, leading-order expressions for the full process rate. While performing experiments involving photon conversions may be challenging, we use the results of our analysis to construct experimental cuts on certain observables that may enhance sensitivity to CPV. We show that there exist regions of phase space on which sensitivity to CPV is of order unity. As a result, the statistical sensitivity of these cuts are verified numerically, using dedicated Monte-Carlo simulations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Search for the CP-violating strong decays η → π + π - and η' (958)→ π + π -

A search for the CP-violating strong decays η→π + π - and η'(958)→π + π - has been performed using approximately 2.5×10 7 events of each of the decays D + →π + π + π - and D$+\atop{s}$→π + π + π - , recorded by the LHCb experiment. The data set corresponds to an integrated luminosity of 3.0 fb -1 of pp collision data recorded during LHC Run 1 and 0.3 fb -1 recorded in Run 2. No evidence is seen for D$+\atop{s}$→π + η(') with η(')→π + π - , and upper limits at 90% confidence level are set on the branching fractions, B(η→π + π - )<1.6×10 -5 and B(η'→π + π - )<1.8×10 -5 . The limit for the η decay is comparable with the existing one, while that for the η' is a factor of three smaller than the previous limit.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2026

CP Violation in the Neutrino Sector

his talk presents an overview of current and future measurements of CP Violation in the neutrino sector

Norrick, Anne [Fermilab] (ORCID:0000000199321012)↗
DOE OSTI2026

CP Violation in the Neutrino Sector

his talk presents an overview of current and future measurements of CP Violation in the neutrino sector

Norrick, Anne [Fermilab] (ORCID:0000000199321012)↗
DOE OSTI2014

Recent Tevatron Results on CP-Violation

Using their full Tevatron Run II data sets, the CDF and D0 Experiments present measurements of CP -violating asymmetries in the charmless decays of bottom baryons Λ0 → pπ-, Λ0 → pK-, and also for B0 → K-π+, B0 → K+π-, b b s Ds → φπ± , and for single muons and like-sign dimuons in pp collisions. Except for the like-sign dimuon asymmetry, these asymmetry measurements are consistent with available predictions of the standard model.

43 PARTICLE ACCELERATORS↗
DOE OSTI2014

Search for CP violation in $D^0 \to h^+h^-$ decays at CDF

I report on a measurement of \CP-violating asymmetries ($A_{\Gamma}$) between effective lifetimes of $D^0$ or $\bar{D}^0$ in fully reconstructed $D^0\to K^+ K^-$ and $D^0\to \pi^+\pi^-$ decays collected in $p\bar{p}$ collisions by the Collider Detector at Fermilab experiment. The full CDF data set corresponding to $9.7$ fb$^{-1}$ of integrated luminosity is used. The flavor of the charm meson at production is determined by exploiting the strong-interaction decay $D^{*+} \to D^0 \pi^+$, while the contamination from mesons originated in $b$-hadron decays is evaluated and subtracted from the sample. Signal yields as functions of the observed decay-time distributions are extracted from maximum likelihood fits and used to measure the asymmetries. The results, $A_\Gamma (K^+K^-) = \bigl(-1.9 \pm 1.5 \mathrm{(stat)} \pm 0.4 \mathrm{(syst)} \bigr)\times10^{-3}$ and $A_\Gamma (\pi^+\pi^-)= \bigl(-0.1 \pm 1.8 \mathrm{(stat)} \pm 0.3 \mathrm{(syst)} \bigr)\times10^{-3}$, and their combination, $A_\Gamma = \bigl(-1.2 \pm 1.2\bigr)\times10^{-3}$, are consistent with the SM predictions and other experimental determinations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Missing energy and the measurement of the CP-violating phase in neutrino oscillations

In the next generation of long-baseline neutrino oscillation experiments aiming to determine the charge-parity-violating phase δ CP in the appearance channel, fine-grained time-projection chambers are expected to play an important role. In this study, we analyze an influence of realistic detector capabilities on the δ CP sensitivity for a setup similar to that of the Deep Underground Neutrino Experiment. We find that the effect of the missing energy carried out by undetected particles is sizable. Although the reconstructed neutrino energy can be corrected for the missing energy, the accuracy of such procedure has to exceed 20%, to avoid a sizable bias in the extracted δ CP value.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Neutrino properties in E{sub 6} Multiplication-Sign SU(2){sub F} SUSY GUT with spontaneous CP violation

We examined the neutrino sector in E{sub 6} Multiplication-Sign SU(2){sub F} SUSY GUT with spontaneous CP violation. At a first glance, the discrete symmetry, which is introduced in order to solve the SUSY CP problem, constrains the allowed operators too strongly for the neutrino sector to be consistent with the experimental data, i.e., the {mu} neutrino becomes massless as commented in the previous work. We showed that this issue can be solved if some operators are taken into account. The predictions on the neutrino masses and mixings are the same as the E{sub 6} models, which are consistent with various experiments on the neutrino oscillations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Impact of indirect CP violation on Br( K S → μ + μ – ) ℓ=0

The decay K S → μ + μ – ) ℓ=0 , with the final muon pair in an angular-momentum zero state, is a sensitive probe of short-distance physics. It has recently been shown how to extract this branching ratio from neutral kaon decay data. We point out that the impact of indirect CP violation on the standard-model prediction of this mode, while nominally of order $\vert$ε K $\vert$ ~ 10 -3 , is enhanced by a large amplitude ratio and leads to a shift of the branching ratio Br( K S → μ + μ – ) ℓ=0 by a few percent, depending on the size of a relative phase that can be extracted from data. We also update the standard-model prediction of the short-distance contribution.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Leptogenesis from low energy CP violation

We revisit the possibility of producing the observed baryon asymmetry of the Universe via thermal leptogenesis, where CP violation comes exclusively from the low-energy phases of the neutrino mixing matrix. We demonstrate the viability of thermal flavoured leptogenesis across seven orders of magnitude (10$^{6}$< T (GeV) < 10$^{13}$), using modern numerical machinery, where the lower bound can be reached only if flavour effects are taken into account and its value depends on the allowed degree of cancellation between the tree-level and radiative contributions to the light neutrino masses. At very high scales (T >>10$^{12}$ GeV), we clarify that thermal leptogenesis is sensitive to the low-energy phases, in contradiction with what is usually claimed in the literature. In particular we demonstrate that Majorana-phase leptogenesis is in general viable while Dirac-phase leptogenesis requires some level of fine-tuning.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Measurement of the direct CP violating charge asymmetry in $B^\pm \rightarrow \mu^\pm \nu_\mu D^{0}$ decays

We present the first measurement of the CP violating charge asymmetry in B±→μ±νμD0 decays using the full Run II integrated luminosity of 10.4 fb-1 in proton-antiproton collisions collected with the D0 detector at the Fermilab Tevatron Collider. We measure a difference in the yield of B- and B+ mesons in these decays by fitting the reconstructed invariant mass distributions. This results in an asymmetry of AμD0=[-0.14±0.20]%, which is consistent with standard model predictions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Recent Tevatron Results on CP-Violation

Using their full Tevatron Run II data sets, the CDF and D0 Experiments present measurements of CP-violating asymmetries in the charmless decay of bottom baryons Lambda-b => p pi-, Lambda-b => p K-, and also for Bs0 => K- pi+, B0 => K+ pi-, Ds => phi pi, and for single muons and like-sign dimuons in p-pbar collisions. Except for the like-sign dimuon asymmetry, these asymmetry measurements are consistent with available predictions of the standard model.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Quantifying limits on CP violating phases from EDMs in supersymmetry

We revisit the calculation of the electron, neutron, and proton electric dipole moments (EDMs) in the constrained minimal supersymmetric standard model (CMSSM). The relatively large mass of the Higgs boson, m H ≃ 125 GeV coupled with the (as yet) lack of discovery of any supersymmetric particle at the LHC, has pushed the supersymmetry breaking scale to several TeV or higher. Though one might expect this decoupling to have relaxed completely any bounds on the two CP violating phases in the CMSSM (θ μ and θ A ), the impressive experimental improvements in the limits on the EDMs (particularly the electron EDM) still allow us to set constraints of order (0.01–0.1)π on θ A and (0.001–0.1)π on θ μ . We also discuss the impact of future improvements in the experimental limits on supersymmetric models.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

The MOMENT to search for CP violation

In this letter, we analyze for the first time the physics reach in terms of sensitivity to leptonic CP violation of the proposed MuOn-decay MEdium baseline NeuTrino beam (MOMENT) experiment, a novel neutrino oscillation facility that would operate with neutrinos from muon decay. Apart from obtaining a sufficiently intense flux, the bottlenecks to the physics reach of this experiment will be achieving a high enough suppression of the atmospheric background and, particularly, attaining a sufficient level of charge identification. We thus present our results as a function of these two factors. We consider a very massive Gd-doped Water Cherenkov detector. We also find that MOMENT will be competitive with other currently planned future oscillation experiments if a charge identification of at least 80 % can be achieved at the same time that the atmospheric background can be suppressed by at least a factor of ten. We also find a large synergy of MOMENT with the current generation of neutrino oscillation experiments, T2K and NOvA, which significantly enhances its final sensitivity.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Baryogenesis via leptonic CP-violating phase transition

Here, we propose a new mechanism to generate a lepton asymmetry based on the vacuum CP-violating phase transition (CPPT). This approach differs from classical thermal leptogenesis as a specific seesaw model, and its UV completion, need not be specified. The lepton asymmetry is generated via the dynamically realised coupling of the Weinberg operator during the phase transition. This mechanism provides a connection with low-energy neutrino observables.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗