Measurement of the Direct CP-violating Charge Asymmetry in D-s(+/-) - greater than Phi pi(+/-) Decays
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72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
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Opportunistic CP violation
In the electroweak sector of the Standard Model, CP violation arises through a very particular interplay between the three quark generations, as described by the Cabibbo-Kobayashi-Maskawa (CKM) mechanism and the single Jarlskog invariant J 4 . Once generalized to the Standard Model Effective Field Theory (SMEFT), this peculiar pattern gets modified by higher-dimensional operators, whose associated Wilson coefficients are usually split into CP-even and odd parts. However, CP violation at dimension four, i.e., at the lowest order in the EFT expansion, blurs this distinction: any Wilson coefficient can interfere with J 4 and mediate CP violation. In this paper, we study such interferences at first order in the SMEFT expansion, $\mathcal{O}(1/Λ^2)$, and we capture their associated parameter space via a set of 1551 linear CP-odd flavor invariants. This construction describes both new, genuinely CP-violating quantities as well as the interference between J 4 and CP-conserving ones. We call this latter possibility opportunistic CP violation. Relying on an appropriate extension of the matrix rank to Taylor expansions, which we dub Taylor rank, we define a procedure to organize the invariants in terms of their magnitude, so as to retain only the relevant ones at a given precision. We explore how this characterization changes when different assumptions are made on the flavor structure of the SMEFT coefficients. Interestingly, some of the CP-odd invariants turn out to be less suppressed than J 4 , even when they capture opportunistic CPV, demonstrating that CP-violation in the SM, at dimension 4, is accidentally small.
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Up sector of minimal flavor violation: top quark properties and direct D meson CP violation
Minimal Flavor Violation in the up-type quark sector leads to particularly interesting phenomenology due to the interplay of flavor physics in the charm sector and collider physics from flavor changing processes in the top sector. We study the most general operators that can affect top quark properties and D meson decays in this scenario, concentrating on two CP violating operators for detailed studies. The consequences of these effective operators on charm and top flavor changing processes are generically small, but can be enhanced if there exists a light flavor mediator that is a Standard Model gauge singlet scalar and transforms under the flavor symmetry group. This flavor mediator can satisfy the current experimental bounds with a mass as low as tens of GeV and explain observed D-meson direct CP violation. Additionally, the model predicts a non-trivial branching fraction for a top quark decay that would mimic a dijet resonance.
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Measurement of branching fraction and search for C P violation in B → ϕ ϕ K
Not Available
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
Searches for New Physics in CP Violation from BABAR
Results of recent searches for new physics in CP violation in charm decays from the BABAR experiment are presented. These results include a measurement of D 0 - anti D 0 mixing and searches for CP violation in two-body D 0 decays, a search for CP violation in the charm decays D ± → K S 0 K ± and D s ± → K S 0 K ± , K S 0 π ± , and a search for direct CP violation in the singly-Cabibbo suppressed D ± → K + K - π ± decays. These studies are based on the final dataset collected by BABAR at the PEP-II B factory at SLAC in the period 1999-2008. No evidence of CP violation is found in these charm decays. The measured mixing parameter y CP = [0.72 ± 0.18(stat) ± 0.12(syst)]% excludes the no-mixing null hypothesis with a significance of 3.3σ .
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Complementarity of LHC and EDMs for exploring Higgs CP violation
We analyze the constraints on a CP-violating, flavor conserving, two Higgs doublet model from the measurements of Higgs properties and from the search for heavy Higgs bosons at LHC, and show that the stronger limits typically come from the heavy Higgs search channels. The limits on CP violation arising from the Higgs sector measurements are complementary to those from EDM measurements. Combining all current constraints from low energy to colliders, we set generic upper bounds on the CP violating angle which parametrizes the CP odd component in the 126 GeV Higgs boson.
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50 years of CP violation — What have we learned?
Early after the discovery of CP violation, the explanation of how the Standard Model of particle physics could allow CP violation was quickly given, but it took many years for the original observation to be unequivocally explained on that basis. It was also proposed that this observation opened up the possibility that we could now explain the fact that the universe is made of matter. Remarkably, 50 years later we have no evidence in particle physics that there is any CP violation except that of the Kobayashi Maskawa mechanism of the standard model. Yet we fail completely to explain the baryon asymmetry of the Universe through that mechanism. After reviewing the main points in the history I describe the present experimental attempts to find CP violation beyond the standard model, and explain the theoretical attempts to explain the matter in the Universe.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Measurement of branching fraction and first evidence of C P violation in B 0 → a 1 ± ( 1260 ) π ∓ decays
Measurement of branching fraction and first evidence of CP violation in B-0 -> a(1)(+/-)(1260)pi(-/+) decays
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
Research in Theoretical Particle Physics: Neutrino Masses and The Origin of CP-Violation
The main goal of this project was to investigate the theories of neutrino masses at the low scale and the origin of CP-violation in physics beyond the Standard Model. The origin of neutrino masses is one of the most pressing issues in particle physics. In this proposal, we investigated the theories for neutrino masses based on local total lepton number. In these theories anomaly cancellation predicts the existence of extra fermions with lepton number, and one of them is a good dark matter (DM) candidate. The cosmological constraints on the DM relic density implies that the lepton number symmetry breaking scale must be below the multi-TeV scale. Therefore, one can hope to test the origin of neutrino masses in current or future experiments. We investigated in great detail the anomaly cancellation in these gauge theories, study the different mechanisms for neutrino masses, study the predictions for direct and indirect dark matter experiments. Since these theories predict new sources of CP violation, we investigated the predictions for the electric dipole moments (EDM). The Higgs decays and the different signatures at the Large Hadron Collider were investigated in great detail. Finally, we studied the possible baryogenesis mechanisms in these theories in agreement with the EDM, DM and collider constraints. The origin of CP violation in the Standard Model is unknown. In this proposal, we investigated the simplest mechanisms for spontaneous CP-violation to explain the CP-violation in the CKM matrix and the value of the QCD vacuum angle. We discussed the Nelson-Barr mechanism in gauge theories predicting vector-like quarks from anomaly cancellation such as theories for local baryon number. We discussed the Bento-Branco-Parada mechanism in gauge theories to explain the CP-Violation in the CKM matrix. We will investigate models with two Higgs doublets in the context of the minimal theory for quark-lepton unification. We will show the non-decoupling effects in the Higgs sector, the main constraints coming from flavour violating processes when the Yukawa couplings are related by the gauge symmetry in theories for quark-lepton unification. We will investigate the predictions for electric dipole moments in these theories. The possibility to have successful baryogenesis was investigated. Finally, we investigated the relation between CP-violation in the quark and leptonic sectors. The future results from these studies could help us to understand two main issues in physics beyond the Standard Model: The Origin of Neutrino Masses and CP-violation.
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Recent Results on T and CP Violation at BABAR
CP-violation (CPV) and Time-reversal violation (TRV) are intimately related through the CPT theorem: if one of these discrete symmetries is violated the other one has to be violated in such a way to conserve CPT. Although CPV in the B 0 B 0 -bar system has been established by the B-factories, implying indirectly TRV, there is still no direct evidence of TRV. We report on the observation of TRV in the B-meson system performed with a dataset of 468 × 10 6 BB-bar pairs produced in Υ(4S) decays collected by the BABAR detector at the PEP-II asymmetric-energy e + e - collider at the SLAC National Accelerator Laboratory. We also report on other CPV measurements recently performed on the B-meson system
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Study of CP Violation in Dalitz-Plot Analyses of B-Meson Decays to Three Kaons
The Standard Model (SM) explains CP violation in terms of the CKM matrix. The BABAR experiment was designed mainly to test the CKM model in B decays. B decays that proceed through b → s loop diagrams, of which B {yields} KKK decays are an example, are sensitive to new physics effects that could lead to deviations from the CKM predictions for CP violation. We present studies of CP violation in the decays B + → K + K - K + , B + → K S 0 K S 0 K + , and B 0 → K + K - K S 0 , using a Dalitz plot amplitude analysis. These studies are based on approximately 470 million B$\bar{B}$ decays collected by BABAR at the PEP-II collider at SLAC. We perform measurements of time-dependent CP violation in B 0 → K + K - K S 0 , including B 0 → ΦK S 0 . We measure a CP-violating phase β eff (ΦK S 0 ) = 0.36 ± 0.11 ± 0.04 rad., in agreement with the SM. This is the world's most precise measurement of this quantity. We also measure direct CP asymmetries in all three decay modes, including the direct CP asymmetry A CP (ΦK + ) = (12.8 ± 4.4 ± 1.3)%, which is 2.8 sigma away from zero. This measurement is in tension with the SM, which predicts an asymmetry of a few percent. We also study the resonant and nonresonant features in the B → KKK Dalitz plots. We find that the hypothetical scalar f X (1500) resonance, introduced by prior analyses to explain an unknown peak in the m KK spectrum, cannot adequately describe the data. We conclude instead that the f X (1500) can be explained as the sum of the f 0 (1500), f' 2 (1525), and f 0 (1710) resonances, removing the need for the hypothetical f X (1500). We also find that an exponential nonresonant model, used by previous analyses to describe the broad nonresonant feature seen in B → KKK decays, cannot fully model the data. We introduce a new nonresonant model that contains more free parameters, allows for phase motion, and contains both S-wave and P-wave components.
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The Lightest Neutralino Annihilation in NMSSM with CP Violation
We discuss the violation of CP invariance in the Higgs sector and its impact on the physical characteristics of the neutralino, and its implication in the processes of annihilation. The process of pair annihilation of the lightest neutralinos into two photons for NMSSM in the one-loop approximation considering the violation of CP-invariance in the extended scalar Higgs sector is calculated. The analysis of the obtained results and the comparison are given.
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New observables for $CP$ violation in Higgs decays
Current experimental data on the 125 GeV Higgs boson still allow room for large $CP$ violation. The observables usually considered in this context are triple product asymmetries, which require an input of four visible particles after imposing momentum conservation. Here, we point out a new class of $CP$ -violating observables in Higgs physics which require only three reconstructed momenta. They may arise if the process involves an interference of amplitudes with different intermediate particles, which provide distinct “strong phases” in the form of the Breit-Wigner widths, in addition to possible “weak phases” that arise from $CP$ -violating couplings of the Higgs in the Lagrangian. As an example, we propose a forward-backward asymmetry of the charged lepton in the three-body Higgs decay, h → ℓ $-$ ℓ + γ , as a probe for $CP$ -violating Higgs couplings to Zγ and γγ pairs. In conclusion, we also discuss other processes exhibiting this type of $CP$ violation.
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Earth mover’s distance as a measure of CP violation
We introduce a new unbinned two sample test statistic sensitive to CP violation utilizing the optimal transport plan associated with the Wasserstein (earth mover’s) distance. The efficacy of the test statistic is shown via two examples of CP asymmetric distributions with varying sample sizes: the Dalitz distributions of B 0 → K + π – π 0 and of D 0 → π + π – π 0 decays. The windowed version of the Wasserstein distance test statistic is shown to have comparable sensitivity to CP violation as the commonly used energy test statistic, but also retains information about the localized distributions of CP asymmetry over the Dalitz plot. For large statistic datasets we introduce two modified Wasserstein distance based test statistics — the binned and the sliced Wasserstein distance statistics, which show comparable sensitivity to CP violation, but improved computing time and memory scalings. Finally, general extensions and applications of the introduced statistics are discussed.
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Search for C P Violation in D 0 → π 0 π 0 Decays
We search for CP violation in neutral charm meson decays using a data sample with an integrated luminosity of 966 fb –1 collected with the Belle detector at the KEKB e + e – asymmetric-energy collider. The asymmetry obtained in the rate of D 0 and D 0 ¯ decays to the π 0 π 0 final state, [–0.03±0.64(stat)±0.10(syst)]%, is consistent with no CP violation. This constitutes an order of magnitude improvement over the existing result. Here, we also present an updated measurement of the CP asymmetry in the D0→K$^{0}_{S}$π 0 decay: ACP(D 0 → K$^{0}_{S}$π 0 ) = [–0.21±0.16(stat)±0.07(syst)]%.
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The role of CP violating scatterings in baryogenesis—case study of the neutron portal
Many baryogenesis scenarios invoke the charge parity (CP) violating out-of-equilibrium decay of a heavy particle in order to explain the baryon asymmetry. Such scenarios will in general also allow CP violating scatterings. We study the effect of these CP violating scatterings on the final asymmetry in a neutron portal scenario. We solve the Boltzmann equations governing the evolution of the baryon number numerically and show that the CP violating scatterings play a dominant role in a significant portion of the parameter space.
73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
Search for CP Violation in the Decay ${D^{+}}\to K_S^0{K^{+}}$
We search for CP violation in the decay ${D^{+}}\to K_S^0{K^{+}}$ using a data sample with an integrated luminosity of 977 fb -1 collected with the Belle detector at the KEKB e + e - asymmetric-energy collider. No CP violation has been observed and the CP asymmetry in ${D^{+}}\to K_S^0{K^{+}}$ decay is measured to be (-0.25±0.28±0.14), which is the most sensitive measurement to date. After subtracting CP violation due to $K^0$-$\bar{K}^0$ mixing, the CP asymmetry in $D^+$→$\bar{K}^0$$K^+$ decay is found to be (+0.08±0.28±0.14).
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