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At least 811 records · Page 45
All sourcesNASA NTRSDOE OSTI
DOE OSTI2011

Interim Design Report for the International Design Study for a Neutrino Factory

The starting point for the International Design Study for the Neutrino Factory (the IDS-NF) was the output of the earlier International Scoping Study for a future Neutrino Factory and super-beam facility (the ISS). The accelerator facility described in section 2 incorporates the improvements that have been derived from the substantial amount of work carried out within the Accelerator Working Group. Highlights of these improvements include: (1) Initial concepts for the implementation of the proton driver at each of the three example sites, CERN, FNAL, and RAL; (2) Detailed studies of the energy deposition in the target area; (3) A reduction in the length of the muon beam phase-rotation and bunching systems; (4) Detailed analyses of the impact of the risk that stray magnetic field in the accelerating cavities in the ionization cooling channel will reduce the maximum operating gradient. Several alternative ionization-cooling lattices have been developed as fallback options to mitigate this technical risk; (5) Studies of particle loss in the muon front-end and the development of strategies to mitigate the deleterious effects of such losses; (6) The development of more complete designs for the muon linac and re-circulating linacs; (7) The development of a design for the muon FFAG that incorporates insertions for injection and extraction; and (8) Detailed studies of diagnostics in the decay ring. Other sub-systems have undergone a more 'incremental' evolution; an indication that the design of the Neutrino Factory has achieved a degree of maturity. The design of the neutrino detectors described in section 3 has been optimized and the Detector Working Group has made substantial improvements to the simulation and analysis of the Magnetized Iron Neutrino Detector (MIND) resulting in an improvement in the overall neutrino-detection efficiency and a reduction in the neutrino-energy threshold. In addition, initial consideration of the engineering of the MIND has generated a design that is feasible and a finite element analysis of the toroidal magnetic field to produce a realistic field map has been carried out. Section 3 also contains, for the first time, a specification for the near-detector systems and a demonstration that the neutrino flux can be determined with a precision of 1% through measurements of inverse muon decay at the near detector. The performance of the facility, the work of the Physics and Performance Evaluation Group, is described in section 1. The effect of the improved MIND performance is to deliver a discovery reach for CP-invariance violation in the lepton sector, the determination of the mass hierarchy, and of {theta}{sub 13} that extends down to values of sin{sup 2} 2{theta}{sub 13} {approx} 5 x 10{sup -5} and is robust against systematic uncertainties. In addition, the improved neutrino-energy threshold has allowed an indicative analysis of the kind of re-optimization of the facility that could be carried out should {theta}{sub 13} be found close to the current upper bound. The results presented in section 1 demonstrate that the discovery reach as well as the precision with which the oscillation parameters can be measured at the baseline Neutrino Factory is superior to that of other proposed facilities for all possible values of sin{sup 2} 2{theta}{sub 13}.

43 PARTICLE ACCELERATORS↗
DOE OSTI2026

Updated constraints from electric dipole moments in the MSSM with R-parity violation

We revisit the electric dipole moments (EDMs) of quarks and leptons in the Minimal Supersymmetric Standard Model (MSSM) with trilinear R-parity violation (RPV). In this framework, EDMs are induced at the two-loop level via RPV interactions. We perform a comprehensive recalculation of several classes of Barr-Zee type diagrams in a general Rξ gauge. While we find general agreement with previous analytic results in the literature, our work provides a valuable independent cross-check of the complicated calculations. We also point out some subtleties in the intermediate steps and in the choice of the flavor basis for the numerical evaluation of the expressions. By confronting the theoretical predictions with the latest experimental limits on EDMs, we derive updated constraints on combinations of RPV couplings. We highlight an approximate, testable correlation between the proton and neutron EDM that emerges within the considered class of RPV models, offering a distinctive signature for future EDM experiments.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

𝑇-invariance violation in neutrino oscillations and matter effects

We investigate the impact of matter effects on 𝑇 (time-reversal)-odd observables, making use of the quantum-mechanical formalism of neutrino-flavor evolution. We attempt to be comprehensive and pedagogical. Matter-induced 𝑇-invariance violation (TV) is qualitatively different from, and more subtle than, matter-induced 𝐶⁢𝑃 (charge-parity)-invariance violation. If the matter distribution is symmetric relative to the neutrino production and detection points, matter effects will not introduce any new TV. However, if there is intrinsic TV, matter effects can modify the size of the 𝑇-odd observable. On the other hand, if the matter distribution is not symmetric, there is genuine matter-induced TV. For Earth-bound long-baseline oscillation experiments, these effects are small. This remains true for unrealistically-asymmetric matter potentials (for example, we investigate the effects of “hollowing out” 50% of the DUNE neutrino trajectory). More broadly, we explore consequences, or lack thereof, of asymmetric matter potentials on oscillation probabilities. While fascinating in their own right, 𝑇-odd observables are currently of limited practical use, due in no small part to a dearth of intense, well-characterized, high-energy electron-neutrino beams. Further in the future, however, intense, high-energy muon storage rings might become available and allow for realistic studies of 𝑇-invariance in neutrino oscillations.

CP violation↗
DOE OSTI2024

Search for 𝐶⁢𝑃-Violating Neutrino Nonstandard Interactions with the NOvA Experiment

This Letter reports a search for charge-parity (𝐶⁢𝑃) symmetry violating nonstandard interactions (NSI) of neutrinos with matter using the NOvA Experiment, and examines their effects on the determination of the standard oscillation parameters. Data from 𝜈 𝜇 ⁡($\bar{𝜈}$ 𝜇 ) → 𝜈 𝜇 ⁡($\bar{𝜈}$ 𝜇 ) and 𝜈 𝜇 ⁡($\bar{𝜈}$ 𝜇 ) → 𝜈 𝑒 ⁡( $\bar{𝜈}$ 𝑒 ) oscillation channels are used to measure the effect of the NSI parameters 𝜖 𝑒⁢𝜇 and 𝜖 𝑒⁢𝜏 . With 90% CL the magnitudes of the NSI couplings are constrained to be |𝜖 𝑒⁢𝜇 | ≲0.3 and |𝜖 𝑒⁢𝜏 | ≲ 0.4. A degeneracy at |𝜖 𝑒⁢𝜏 | ≈ 1.8 is reported, and we observe that the presence of NSI limits sensitivity to the standard 𝐶⁢𝑃 phase 𝛿 𝐶⁢𝑃 .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

New graph-neural-network flavor tagger for Belle II and measurement of sin 2⁢𝜙 1 in 𝐵 0 → 𝐽/𝜓⁢𝐾$^0_ S$ decays

We present GFlaT, a new algorithm that uses a graph-neural-network to determine the flavor of neutral 𝐵 mesons produced in ϒ⁡(4⁢𝑆) decays. It improves previous algorithms by using the information from all charged final-state particles and the relations between them. We evaluate its performance using 𝐵 decays to flavor-specific hadronic final states reconstructed in a 362 fb −1 sample of electron-positron collisions collected at the ϒ⁡(4⁢𝑆) resonance with the Belle II detector at the SuperKEKB collider. We achieve an effective tagging efficiency of (37.40 ± 0.43 ± 0.36%), where the first uncertainty is statistical and the second systematic, which is 18% better than the previous Belle II algorithm. Demonstrating the algorithm, we use 𝐵 0 →𝐽/𝜓⁢𝐾$^0_ S$ decays to measure the mixing-induced and direct 𝐶⁢𝑃 violation parameters, 𝑆 = (0.724 ± 0.035 ± 0.009) and 𝐶 = (−0.035 ± 0.026 ± 0.029).

CP violation↗
DOE OSTI2017

The photo-philic QCD axion

Here, we propose a framework in which the QCD axion has an exponentially large coupling to photons, relying on the “clockwork” mechanism. We discuss the impact of present and future axion experiments on the parameter space of the model. In addition to the axion, the model predicts a large number of pseudoscalars which can be light and observable at the LHC. In the most favorable scenario, axion Dark Matter will give a signal in multiple axion detection experiments and the pseudo-scalars will be discovered at the LHC, allowing us to determine most of the parameters of the model.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

X-ray polarization signals from magnetars with axion-like-particles

Axion-like-particles (ALPs) produced in the core of a magnetar can convert to photons in the magnetosphere, giving rise to novel features in the X-ray spectrum. Since ALPs only mix with the parallel mode of the photon, the polarization of the soft and hard X-ray spectra is predicted to have an O-mode component, in addition to the mainly X-mode component given by most astrophysical models. The relative strength of the O-mode component depends on the intensity of ALPs produced in the core and the probability of conversion. We quantify our results by considering X-ray emission produced both by astrophysical processes and by ALP-photon conversion, in an uncorrelated fashion, and in different relative proportions, which we parametrize by the angle χ o . We then define a normalized astrophysics-subtracted Stokes parameter R which only acquires non-zero values in the presence of ALP-photon conversion. We find, remarkably, that the parameter R factorizes into a product of the ALP-to-photon conversion probability and cos(2χ o ) and display R, as well as the usual Stokes parameter Q, as a function of the photon energy and relative fractions of ALP and photon intensities. For benchmark points currently allowed by the CAST experiment, the O-mode prediction can be tested in future X-ray polarimeters and used either to constrain ALPs or find evidence for them.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Yukawa sector of minimal SO(10) unification

Here, we show that in SO(10) models, a Yukawa sector consisting of a real 10H, a real 120 H and a complex 126 H of Higgs fields can provide a realistic fit to all fermion masses and mixings, including the neutrino sector. Although the group theory of SO(10) demands that the 10 H and 120 H be real, most constructions complexify these fields and impose symmetries exterior to SO(10) to achieve predictivity. The proposed new framework with real 10H and real 120 H relies only on SO(10) gauge symmetry, and yet has a limited number of Yukawa parameters. Our analysis shows that while there are restrictions on the observables, a good fit to the entire fermion spectrum can be realized. Unification of gauge couplings is achieved with an intermediate scale Pati-Salam gauge symmetry. Proton decay branching ratios are calculable, with the leading decay modes being p→ $\bar{v}$π + and p→ e + π 0 .

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2020

Local SU(2) × U(1) quark flavor symmetry in the RS bulk

We propose a model of quark flavor based on an additional SU(2) × U(1) local symmetry in a warped extra dimensional bulk. In contrast to other works, we break the additional gauge symmetry in the bulk via two complex scalars which acquire bulk vevs, rather than relying on brane-localized symmetry breaking. A gauge-covariant Kaluza-Klein decomposition of a theory with a bulk spontaneously broken gauge symmetry is performed, and exact expressions for the bulk profiles of all physical particles in such systems are given. The SM quark masses and mixings are then recreated using gauge-covariant bulk quark mass terms and Yukawa-like couplings to the new bulk scalars. A numerical sampling of points in the model parameter space that recreate the quark masses and mixings is performed at a KK scale of M KK = 5 TeV. We then compute the ΔF = 2 4-quark operators arising from our new flavor gauge bosons and scalars, and those arising from Kaluza-Klein modes of SM gauge bosons. By decoupling one of our bulk scalar fields to all quark fields except the right-handed up-like sector, we find that it is possible to greatly suppress tree-level contributions to the highly constrained Kaon mixing parameters. Instead, the dominant constraints on the model emerge from neutral Bd and D meson mixing. These constraints are explored with our numerical sampling of the model parameter space, and the specific contribution of the new flavor gauge bosons and scalars is discussed. We find that for a significant range of realistic flavor gauge couplings, the new gauge bosons compete with the normally dominant gluon flavor-changing currents, but flavor-changing operators emerging from the bulk scalar fields are highly suppressed. Finally, we briefly comment on flavor constraints that are independent of the flavor gauge sector arising from the Z$\overline{b}$ L b L coupling and rare top decays.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Non-Standard Interactions in propagation at the Deep Underground Neutrino Experiment

Here, we study the sensitivity of current and future long-baseline neutrino oscillation experiments to the effects of dimension six operators affecting neutrino propagation through Earth, commonly referred to as Non-Standard Interactions (NSI). All relevant parameters entering the oscillation probabilities (standard and non-standard) are considered at once, in order to take into account possible cancellations and degeneracies between them. We find that the Deep Underground Neutrino Experiment will significantly improve over current constraints for most NSI parameters. Most notably, it will be able to rule out the so-called LMA-dark solution, still compatible with current oscillation data, and will be sensitive to off-diagonal NSI parameters at the level of ε ~ $ \mathcal{O} $ (0.05 – 0.5). We also identify two degeneracies among standard and non-standard parameters, which could be partially resolved by combining T2HK and DUNE data.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

A measurement of the CP asymmetry difference between Λ c + → pK – K + and pπ – π + decays

The difference between the CP asymmetries in the decays Λ c + → pK – K + and Λ c + → pπ – π + is presented. Proton-proton collision data taken at centre-of-mass energies of 7 and 8 TeV collected by the LHCb detector in 2011 and 2012 are used, corresponding to an integrated luminosity of 3 fb –1 . The Λ c + candidates are reconstructed as part of the Λ b o → Λ c + μ – X decay chain. In order to maximize the cancellation of production and detection asymmetries in the difference, the final-state kinematic distributions of the two samples are aligned by applying phase-space-dependent weights to the Λ c + → pπ – π + sample. This alters the definition of the integrated CP asymmetry to A CP wgt (pπ – π + ).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

The one-loop impact of a dependent mass: the role of m 3 in the C2HDM

In the complex 2-Higgs-Doublet Model (C2HDM), the mass m 3 of the heaviest neutral scalar h 3 is usually chosen as a derived parameter. We investigate one-loop corrections to m 3 and their impact on decays of h 3 . Very fine-tuned regions of the parameter space can be found where such corrections are large, not due to subtraction schemes, but rather due to the particular dependence of m 3 on the independent parameters. We show that even moderate corrections can have a significant impact on decays of h 3 , as they may be several times enhanced by leading-order factors.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

WIMP dark matter in the parity solution to the strong CP problem

We extend the Standard Model (SM) with parity symmetry, motivated by the strong CP problem and dark matter. In our model, parity symmetry is conserved at high energy by introducing a mirror sector with the extra gauge symmetry, SU(2) R × U(1) R . The charges of SU(2) R × U(1) R are assigned to the mirror fields in the same way as in the SM, but the chiralities of the mirror fermions are opposite to respect the parity symmetry. The strong CP problem is resolved, since the mirror quarks are also charged under the SU(3) c in the SM. In the minimal setup, the mirror gauge symmetry leads to stable colored particles which would be inconsistent with the observed data, so that we introduce two scalars in order to deplete the stable colored particles. Interestingly, one of the scalars becomes stable because of the gauge symmetry and therefore can be a good dark matter candidate. We especially study the phenomenology relevant to the dark matter, i.e. thermal relic density, direct and indirect searches for the dark matter. The bounds from the LHC experiment and the Landau pole are also taken into account. As a result, we find that a limited region is viable: the mirror up quark mass is around [600 GeV, 3 TeV] and the relative mass difference between the dark matter and the mirror up quark or electron is about O(1–10%). We also discuss the neutrino sector and show that the right-handed neutrinos in the mirror sector can increase the effective number of neutrinos or dark radiation by 0.14.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Measurement of CP observables in B ± → D (*) K ± and B ± → D (*) π ± decays using two-body D final states

Measurements of CP observables in B ± → D (*) K ± and B ± → D (*) π ± decays are presented, where D (∗) indicates a neutral D or D ∗ meson that is an admixture of meson and anti-meson states. Decays of the D (∗) meson to the Dπ 0 and Dγ final states are partially reconstructed without inclusion of the neutral pion or photon. Decays of the D meson are reconstructed in the K ± π ∓ , K + K - , and π + π - final states. The analysis uses a sample of charged B mesons produced in proton-proton collisions and collected with the LHCb experiment, corresponding to integrated luminosities of 2.0, 1.0, and 5.7 fb -1 taken at centre-of-mass energies of 7, 8, and 13 TeV, respectively. The measurements of partially reconstructed B ± → D (*) K ± and B ± → D (∗) π ± with D → K ∓ π ± decays are the first of their kind, and a first observation of the B ± → (Dπ 0 ) D ∗ π ± decay is made with a significance of 6.1 standard deviations. All CP observables are measured with world-best precision, and in combination with other LHCb results will provide strong constraints on the CKM angle γ.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗