CP-violating Processes Research Articles

Matter-antimatter asymmetry and non-inertial effects

We investigate non-inertial effects on CP-violating processes using a model, based on the framework of quantum field theory in curved spacetimes, devised to account for the decay of accelerated particles. We show that the CP violation parameter for the decay of accelerated kaons into two pions decreases very slightly as very high accelerations are achieved, implying decreased asymmetry between matter and antimatter in this regime. We discuss the relationship between these results and cosmological processes surrounding matter-antimatter asymmetry and argue that, due to the connection between non-inertial and thermal phenomena established by the Unruh effect, this kind of computation may prove useful in furthering the understanding of thermodynamical effects in curved spacetimes.

A comprehensive study on the semileptonic decay of heavy flavor mesons

The semileptonic decay of heavy flavor mesons offers a clean environment for extraction of the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements, which describes the CP-violating and flavor changing process in the Standard Model. The involved form factors where the dynamical information is encoded play an essential role in achieving any conclusive statement. That is, the knowledge of the form factors should be under good control, requiring one to examine more observables in addition to the branching fraction. In this paper, we provide the mean value and the q2-dependent shape for further observables [differential decay distribution (dΓ/dq2), forward-backward asymmetry left({mathcal{A}}_{FB}^{ls}right) , longitudinal left({P}_L^lright) and transverse left({P}_T^lright) polarization of a charged lepton, longitudinal polarization of a vector meson in the final state left({F}_L^l(V)right) , leptonic convexity parameter left({C}_F^lright) , and trigonometric moments left({W}_i^lright) in the decay of D(s) and B(s) to P/Vl+νl (l = e, μ or τ)], based on the predictions of the relevant form factors from the covariant light-front quark model. P and V denote the pseudoscalar and vector meson, respectively. As a comparison, we find a good agreement with the results from the covariant confining quark model and the relativistic quark model in the literature. As it has been observed that the {P}_L^l and {F}_L^l(V) are crucial quantities to discriminate various New Physics models, the reexamination of these observables from a different method is also essential and necessary.

Search for intermediate resonances and dark gauge bosons in J/ψ→γπ0η′

We report on an analysis of the decay $J/\psi\rightarrow\gamma\pi^0\eta^{\prime}$ using a sample of $(1310.6 \pm 7.0) \times ~10^6~ J/\psi$ events collected with the BESIII detector. We search for the CP-violating process $\eta_c\rightarrow\pi^0\eta^{\prime}$ and a dark gauge boson $U'$ in $J/\psi\rightarrow U^{\prime}\eta^{\prime},~U^{\prime}\rightarrow\gamma\pi^0,~\pi^0\rightarrow\gamma\gamma$. No evidence of an $\eta_{c}$ signal is observed in the $\pi^0\eta^{\prime}$ invariant-mass spectrum and the upper limit of the branching fraction is determined to be $7.2 \times~10^{-5}$ at the 90\% confidence level. We also find no evidence of $U'$ production and set upper limits at the 90\% confidence level on the product branching fraction $\mathcal{B}(J/\psi \rightarrow U^{\prime} \eta^{\prime}) \times \mathcal{B}(U^{\prime} \rightarrow \pi^{0} \gamma)$ in the range between $(0.8 - 6.5)\times 10^{-7}$ for 0.2 $\leq m_{U^{\prime}} \leq 2.1 $GeV$/c^{2}$. In addition, we study the process $J/\psi\rightarrow\omega\eta^{\prime}$ with $\omega\rightarrow\gamma\pi^0$. The branching fraction of $J/\psi\rightarrow\omega\eta^{\prime}$ is found to be $(1.87\pm0.09\pm0.12) \times 10^{-4}$, where the first uncertainty is statistical and the second is systematic, with a precision that is improved by a factor of 1.4 over the previously published BESIII measurement.

Unitarity and CP violation in leptogenesis at NLO: general considerations and top Yukawa contributions

With an emphasis on unitarity and CPT requirements, we study the inclusion of CP-violating processes in baryogenesis at next-to-leading order, particularly those involving the top Yukawa interaction in leptogenesis. We show that there are more contributions than previously considered, but also important cancellations. Some of these involve the interference of connected with disconnected diagrams. We also discuss on the application of the Kinoshita-Lee-Nauenberg theorem to treat the infrared divergences that are common at next-to-leading order. Finally, we calculate the CP asymmetry in the three-body decay of a sterile neutrino into a lepton and top quarks.

LHC benchmarks from flavored gauge mediation

We present benchmark points for LHC searches from flavored gauge mediation models, in which messenger-matter couplings give flavor-dependent squark masses. Our examples include spectra in which a single squark - stop, scharm, or sup - is much lighter than all other colored superpartners, motivating improved quark flavor tagging at the LHC. Many examples feature flavor mixing; in particular, large stop-scharm mixing is possible. The correct Higgs mass is obtained in some examples by virtue of the large stop A-term. We also revisit the general flavor and CP structure of the models. Even though the A-terms can be substantial, their contributions to EDM's are very suppressed, because of the particular dependence of the A-terms on the messenger coupling. This holds regardless of the messenger-coupling texture. More generally, the special structure of the soft terms often leads to stronger suppression of flavor- and CP-violating processes, compared to naive estimates.

Flavor violating [formula omitted] from [formula omitted] SUSY GUT in High-Scale SUSY

We propose an SO(10) supersymmetric grand unified theory (SUSY GUT), where the SO(10) gauge symmetry breaks down to SU(3)c×SU(2)L×U(1)Y×U(1)X at the GUT scale and U(1)X is radiatively broken at the SUSY-braking scale. In order to achieve the observed Higgs mass around 126 GeV and also to satisfy constraints on flavor- and/or CP-violating processes, we assume that the SUSY-breaking scale is O(100) TeV, so that the U(1)X breaking scale is also O(100) TeV. One big issue in the SO(10) GUTs is how to realize realistic Yukawa couplings. In our model, not only 16-dimensional but also 10-dimensional matter fields are introduced to predict the observed fermion masses and mixings. The Standard-Model quarks and leptons are linear combinations of the 16- and 10-dimensional fields so that the U(1)X gauge interaction may be flavor-violating. We investigate the current constraints on the flavor-violating Z′ interaction from the flavor physics and discuss prospects for future experiments.

SUSY FLAVOR v2.5: A computational tool for FCNC and CP-violating processes in the MSSM

SUSY FLAVOR v2.5: A computational tool for FCNC and CP-violating processes in the MSSM

Test of CPT and Lorentz symmetry in entangled neutral kaons with the KLOE experiment

Neutral kaon pairs produced in ϕ decays in anti-symmetric entangled state can be exploited to search for violation of CPT symmetry and Lorentz invariance. We present an analysis of the CP-violating process ϕ→KSKL→π+π−π+π− based on 1.7 fb−1 of data collected by the KLOE experiment at the Frascati ϕ-factory DAΦNE. The data are used to perform a measurement of the CPT-violating parameters Δaμ for neutral kaons in the context of the Standard Model Extension framework. The parameters measured in the reference frame of the fixed stars are:Δa0=(−6.0±7.7stat±3.1syst)×10−18 GeV,ΔaX=(0.9±1.5stat±0.6syst)×10−18 GeV,ΔaY=(−2.0±1.5stat±0.5syst)×10−18 GeV,ΔaZ=(3.1±1.7stat±0.5syst)×10−18 GeV. These are presently the most precise measurements in the quark sector of the Standard Model Extension.

Flavor of gluino decay in high-scale supersymmetry

The discovery of the Higgs boson with a mass of about 125 GeV intimates us a possibility of a high-scale supersymmetry (SUSY) breaking model, where a sfermion mass scale is much higher than the electroweak scale. Although a general SUSY standard model can contribute to the low-energy flavor and/or CP-violating processes, the high-scale SUSY breaking model provides smaller signatures and therefore are less constrained, even in the presence of large flavor/CP violations of sfermions. However, a manner of gluino decay directly reflects the squark flavor structure and provides us a clue for the sfermion flavor structure. In this paper, we study the gluino decay in detail and discuss the interplay with the gluino decay and low-energy flavor and CP observation.

SUSY_FLAVOR v2: A computational tool for FCNC and CP-violating processes in the MSSM

We present SUSY_FLAVOR version 2 — a Fortran 77 program that calculates low-energy flavor observables in the general R-parity conserving MSSM. For a set of MSSM parameters as input, the code gives predictions for: 1.Electric dipole moments of the leptons and the neutron.2.Anomalous magnetic moments (i.e. g−2) of the leptons.3.Radiative lepton decays (μ→eγ and τ→μγ,eγ).4.Rare Kaon decays (KL0→π0ν̄ν and K+→π+ν̄ν).5.Leptonic B decays (Bs,d→l+l−, B→τν and B→Dτν).6.Radiative B decays (B→X̄sγ).7.ΔF=2 processes (K̄0–K0, D̄–D, B̄d–Bd and B̄s–Bs mixing). Comparing to SUSY_FLAVOR v1, where the matching conditions were calculated strictly at one-loop level, SUSY_FLAVOR v2 performs the resummation of all chirally enhanced corrections, i.e. takes into account the enhanced effects from tanβ and/or large trilinear soft mixing terms to all orders in perturbation theory. Also, in SUSY_FLAVOR v2 new routines calculation of B→(D)τν, g−2, radiative lepton decays and Br(l→l′γ) were added. All calculations are done using exact diagonalization of the sfermion mass matrices. The program can be obtained from http://www.fuw.edu.pl/susy_flavor. Program summaryProgram title:SUSY_FLAVOR v2Catalogue identifier: AEGV_v2_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEGV_v2_0.htmlProgram obtainable from: CPC Program Library, Queen’s University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 15683No. of bytes in distributed program, including test data, etc.: 89130Distribution format: tar.gzProgramming language: Fortran 77.Computer: Any.Operating system: Any, tested on Linux.Classification: 11.6.Does the new version supersede the previous version?: YesCatalogue identifier of previous version: AEGV_v1_0Journal reference of previous version: Comput. Phys. Comm. 181 (2010) 2180Nature of problem:Predicting CP-violating observables, meson mixing parameters and branching ratios for set of rare processes in the general R-parity conserving MSSM.Solution method:We use standard quantum theoretical methods to calculate Wilson coefficients in MSSM and at one loop including QCD corrections at higher orders when this is necessary and possible. The input parameters can be read from an external file in SLHA format.Reasons for new version:A major rewrite of the internal code structure to accommodate higher order corrections; new observables added.Summary of revisions:1.SUSY_FLAVOR v2.0 is able to perform resummation of chirally enhanced corrections to all orders of perturbation expansion (v1.0 included 1-loop terms only).2.Routines calculating new observables are added: g-2 lepton magnetic moment anomaly, μ to eγ and τ to eγ,μγ decays, B to Dτν decays, B to μe,τe,τμ decays.3.Parameter initialization in the sfermion sector is simplified and follows, by default, the SLHA2 conventions.Restrictions: The results apply only to the case of MSSM with R-parity conservation.Running time: For a single parameter set approximately 1 s in double precision on a PowerBook Mac G4.

SUSY_FLAVOR: A computational tool for FCNC and CP-violating processes in the MSSM

We present SUSY_FLAVOR – a Fortran 77 program that calculates important leptonic and semi-leptonic low-energy observables in the general R-parity conserving MSSM. For a set of input MSSM parameters, the code gives predictions for the K ¯ 0 K 0 , D ¯ D , B ¯ d B d and B ¯ s B s mixing parameters; B → X s γ , B s , d → l + l − , K L 0 → π 0 ν ¯ ν and K + → π + ν ¯ ν decay branching ratios; and the electric dipole moments of the leptons and the neutron. All these quantities are calculated at one-loop level (with some higher-order QCD corrections included) in the exact sfermion mass eigenbasis, without resorting to mass insertion approximations. The program can be obtained from http://www.fuw.edu.pl/susy_flavor. Program summary Program title: SUSY_FLAVOR Catalogue identifier: AEGV_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEGV_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 14 603 No. of bytes in distributed program, including test data, etc.: 82 126 Distribution format: tar.gz Programming language: Fortran 77 Computer: PCs and workstations Operating system: Any, tested on Linux Classification: 11.6 Nature of problem: Predicting CP-violating observables, meson mixing parameters and branching ratios for a set of rare processes in the general R-parity conserving MSSM. Solution method: We use standard quantum theoretical methods to calculate Wilson coefficients in MSSM and at one loop including QCD corrections at higher orders when this is necessary and possible. The input parameters can be read from an external file in SLHA format. Restrictions: The results apply only to the case of MSSM with R-parity conservation. Running time: For single parameter set approximately 1 s in double precision on a PowerBook Mac G4.

Gaugino anomaly mediated SUSY breaking: phenomenology and prospects for the LHC

We examine the supersymmetry phenomenology of a novel scenario of supersymmetry (SUSY) breaking which we call Gaugino Anomaly Mediation, or inoAMSB. This is suggested by recent work on the phenomenology of flux compactified type IIB string theory. The essential features of this scenario are that the gaugino masses are of the anomaly-mediated SUSY breaking (AMSB) form, while scalar and trilinear soft SUSY breaking terms are highly suppressed. Renormalization group effects yield an allowable sparticle mass spectrum, while at the same time avoiding charged LSPs; the latter are common in models with negligible soft scalar masses, such as no-scale or gaugino mediation models. Since scalar and trilinear soft terms are highly suppressed, the SUSY induced flavor and CP-violating processes are also suppressed. The lightest SUSY particle is the neutral wino, while the heaviest is the gluino. In this model, there should be a strong multi-jet +etmiss signal from squark pair production at the LHC. We find a 100 fb^{-1} reach of LHC out to m_{3/2}\sim 118 TeV, corresponding to a gluino mass of \sim 2.6 TeV. A double mass edge from the opposite-sign/same flavor dilepton invariant mass distribution should be visible at LHC; this, along with the presence of short-- but visible-- highly ionizing tracks from quasi-stable charginos, should provide a smoking gun signature for inoAMSB.

LEPTOGENESIS: THE ELECTROMAGNETIC VERSION

In this work, we explore the possibility of leptogenesis beyond the standard Yukawa-mediated decays by considering a scenario where effective electromagnetic dipole operators that connect the light and heavy neutrinos play an important role. Through these operators, new decay channels for the postulated heavy neutrinos are opened up, and consequently, such L- and CP-violating processes can lead to the generation of the correct baryon asymmetry of the universe. In addition, it has been found that the relationship of the leptogenesis scale to the light neutrino masses is very similar to that for the standard leptogenesis setup.

About detecting CP-violating processes in J/Ψ → K0K̄0 decay

Questions about detecting the CP-violating decay process of J/ψ → K0K̄0 → KSKS are discussed. Possible background and material regeneration effects are analyzed. The discussion can be directly extended to other vector quarkonium decays, like γ, ψ(2S), ψ(2S) and ψ → KSKS.

Messages on Flavour Physics Beyond the Standard Model

I present a brief summary of the main results on flavour physics beyond the Standard Model that have been obtained in 2008 by my collaborators and myself at the TUM. In particular I list main messages coming from our analyses of flavour and CP-violating processes in Supersymmetry, the Littlest Higgs model with T-Parity and a warped extra dimension model with custodial protection for flavour violating $Z$ boson couplings.

Flavor physics of leptons and dipole moments

This chapter of the report of the “Flavor in the era of the LHC” Workshop discusses the theoretical, phenomenological and experimental issues related to flavor phenomena in the charged lepton sector and in flavor conserving CP-violating processes. We review the current experimental limits and the main theoretical models for the flavor structure of fundamental particles. We analyze the phenomenological consequences of the available data, setting constraints on explicit models beyond the standard model, presenting benchmarks for the discovery potential of forthcoming measurements both at the LHC and at low energy, and exploring options for possible future experiments.

Status of the LHCb Experiment

LHCb is a dedicated experiment to study CP violation and other rare processes in the B meson system at the LHC. This paper reports on the progress of the construction and installation of the detector that is expected to be ready for data taking at the beginning of LHC operation in late 2007.

Sensitivity to new supersymmetric thresholds through flavor andCPviolating physics

Treating the MSSM as an effective theory below a threshold scale {lambda}, we study the consequences of having dimension-five operators in the superpotential for flavor and CP-violating processes. Below the supersymmetric threshold such terms generate flavor changing and/or CP-odd effective operators of dimension six composed from the standard model fermions, that have the interesting property of decoupling linearly with the threshold scale, i.e. as 1/({lambda}m{sub soft}), where m{sub soft} is the scale of soft supersymmetry breaking. The assumption of weak-scale supersymmetry, together with the stringent limits on electric dipole moments and lepton flavor-violating processes, then provides sensitivity to {lambda} as high as 10{sup 7}-10{sup 9} GeV. We discuss the varying sensitivity to these scales within several MSSM benchmark scenarios and also outline the classes of UV physics which could generate these operators.

Flavor- andCP-Violating Physics from New Supersymmetric Thresholds

Treating the minimal supersymmetric standard model as an effective theory, we study the implications of having dimension-five operators in the superpotential for flavor- and CP-violating processes, exploiting the linear decoupling of observable effects with respect to the new threshold scale c. We show that the assumption of weak-scale supersymmetry, when combined with the stringent limits on electric dipole moments and lepton-flavor-violating processes, provides sensitivity to Lambda as high as 10(7)-10(9) GeV (and up to 10(17) GeV through the theta term), while the next generation of experiments could directly probe the high-energy scales suggested by neutrino physics.

SoftCPviolation inK-meson systems

We consider a model with soft CP violation which accommodate the CP violation in the neutral kaons even if we assume that the Cabibbo-Kobayashi-Maskawa mixing matrix is real and the sources of CP violation are three complex vacuum expectation values and a trilinear coupling in the scalar potential. We show that for some reasonable values of the masses and other parameters the model allows to explain all the observed CP violation processes in the $K^0$-$\bar{K}^0$ system.