TESLA Technical Design Report Part III: Physics at an e+e- Linear Collider
The TESLA Technical Design Report Part III: Physics at an e+e- Linear Collider
hep-ph↗
arXiv subjects
S. Y. Choi
Publications and source records attributed to S. Y. Choi.
Higgs Boson Decays in the Minimal Supersymmetric Standard Model with Radiative Higgs Sector CP Violation
We re-evaluate the decays of the Higgs bosons in the minimal supersymmetric standard model (MSSM) where the tree-level CP invariance of the Higgs potential is explicitly broken by the loop effects of the third-generation squarks with CP-violating soft-breaking Yukawa interactions. This study is based on the mass matrix of the neutral Higgs bosons that is valid for arbitrary values of all the relevant MSSM parameters. It extends the previous work considerably by including neutral Higgs-boson decays into virtual gauge bosons and those into top-squark pairs, by implementing squark-loop contributions to the two-gluon decay channel, and by incorporating the decays of the charged Higgs boson. The constraints from the electron electric dipole moment on the CP phases are also discussed. We find that the branching fractions of both the neutral and charged Higgs-boson decays and their total decay widths depend strongly on the CP phases of the top (and bottom) squark sectors through the loop-induced neutral Higgs boson mixing as well as the direct couplings of the neutral Higgs bosons to top squark pairs.
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Measuring the Spin of the Higgs Boson
By studying the threshold dependence of the excitation curve and the angular distribution in Higgs-strahlung at e+e- colliders, e+e- -> HZ, the spin of the Higgs boson in the Standard Model and related extensions can be determined unambiguously in a model-independent way.
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Neutralino-Nucleus Elastic Cross Section in the Minimal Supersymmetric Standard Model with Explicit CP Violation
We study the elastic scattering of the lightest neutralino with a nucleus in the framework of the minimal supersymmetric standard model (MSSM) with explicit flavor preserving CP violation, including the one-loop CP-violating neutral Higgs-boson mixing effects induced dominantly by the CP phases in the top and bottom (s)quark sectors. We construct the most general form of the effective Lagrangian for the neutralino-nucleus scattering in the limit of vanishing momentum transfers and then we perform a comprehensive analysis of the effects of the complex CP phases on the mass spectra of the lightest neutralino, neutral Higgs bosons and top squarks, and on the the spin-dependent and spin-independent neutralino-nucleus scattering cross section for three neucleus targets F, Si and Ge. The CP phases can reduce or enhance the neutralino-nucleus cross sections significantly, depending on the values of the real parameters in the MSSM.
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Probing the MSSM Higgs Boson Sector with Explicit CP Violation through Third Generation Fermion Pair Production at Muon Colliders
We perform a systematic study of the production of a third-generation fermion-pair, $μ^+μ^-\to f\bar{f}$ for $f=τ^-,b$, and t in the minimal supersymmetric standard model (MSSM) with explicit CP violation, which is induced radiatively by soft trilinear interactions related to squarks of the third generation. We classify all the observables for probing the CP property of the Higgs bosons constructed by the initial muon beam polarization along with the unpolarized final fermions and with the final-fermion polarization configuration of equal helicity, respectively. The observables allow for complete determination of CP property of the neutral Higgs bosons. The interference between the Higgs boson and gauge boson contributions also could provide a powerful method for the determination of the CP property of two heavy Higgs bosons in the top-quark pair production near the energy region of the Higgs-boson resonances. For the lightest Higgs-boson mass there is no sizable interference between scalar and vector contributions for the determination of the CP property of the lightest Higgs boson. We give a detailed numerical analysis to show how the radiatively-induced CP violation in the Higgs sector of the MSSM can be measured.
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Measuring MSSM CP-violating Phases through Spin Correlated Supersymmetric Tri-lepton Signatures at the Tevatron
We provide a detailed analysis of the supersymmetric tri-lepton signals for sparticle searches at the Tevatron in the minimal supersymmetric standard model with general CP-violating phases but without flavor mixing among sfermions of different generation. The stringent experimental constraints on the CP-violating phases from the electron and neutron electric dipole moments are included in the analysis for two exemplary scenarios of the SUSY parameters; one with decoupled first two generation sfermions and the other with non-decoupled sfermions. In both scenarios, the production cross section and the branching fractions of the leptonic chargino and neutralino decays are sensitive to CP-violating phases. The production-decay spin correlations lead to several non-trivial CP-even observables such as the lepton invariant mass distribution and the lepton angular distribution, and several interesting T-odd (CP-odd) momentum triple products. The possibility of measuring the CP-violating phases directly through those T-odd observables is investigated in detail.
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Measuring the Higgs CP Property through Top Quark Pair Production at Photon Linear Colliders
We present a model-independent study of the effects of a neutral Higgs boson without definite CP-parity in the process $γγ\to t\bar{t}$ around the mass pole of the Higgs boson. Near the resonance pole, the interference between the Higgs-exchange and the continuum amplitudes can be sizable if the photon beams are polarized and helicities of the top and anti-top quarks are measured. Study of these interference effects enables one to determine the CP property of the Higgs boson completely. An example of the complete determination is demonstrated in the context of the minimal supersymmetric standard model.
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Loop Corrections to the Neutral Higgs Boson Sector of the MSSM with Explicit CP Violation
We compute one-loop corrections to the mass matrix of the neutral Higgs bosons of the Minimal Supersymmetric Standard Model with explicit CP violation. We use the effective potential method, allowing for arbitrary splitting between squark masses. We include terms O(g^2 h^2), where g and h stand for electroweak gauge and Yukawa couplings, respectively. Leading two-loop corrections are taken into account by means of appropriately defined running quark masses.
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s-Channel Production of MSSM Higgs Bosons at a Muon Collider with Explicit CP Violation
A muon collider with controllable energy resolution and transverse beam polarization provides a powerful probe of the Higgs sector in the minimal supersymmetric standard model with explicit CP violation, through s-channel production of Higgs bosons. The production rates and the CP-even and CP-odd transverse-polarization asymmetries are complementary in diagnosing CP violation in the Higgs sector.
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Probing MSSM Higgs Sector with Explicit CP Violation at a Photon Linear Collider
The CP properties of Higgs bosons can be probed through their s-channel resonance productions via photon-photon collisions by use of circularly and/or linearly polarized backscattered laser photons at a TeV-scale linear e^+ e^- collider. Exploiting this powerful tool, we investigate in detail the Higgs sector of the minimal supersymmetric Standard Model with explicit CP violation.
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Reconstructing the Chargino System at $e^+e^-$ Linear Colliders
In most supersymmetric theories charginos, $\tildeχ^\pm_{1,2}$, belong to the class of the lightest supersymmetric particles. The chargino system can be reconstructed completely in $e^+e^-$ collider experiments: $e^+e^-\to\tildeχ_i^+ \tildeχ_j^- [i,j=1,2]$. By measuring the total cross sections and the asymmetries with polarized beams, the chargino masses and the gaugino-higgsino mixing angles of these states can be determined accurately. If only the lightest charginos $\tildeχ_1^\pm$ are kinematically accessible in a first phase of the machine, transverse beam polarization or the measurement of chargino polarization in the final state is needed to determine the mixing angles. From these observables the fundamental SUSY parameters can be derived: the SU(2) gaugino mass $M_2$, the modulus and the cosine of the CP-violating phase of the higgsino mass parameter $μ$, and $\tanβ= v_2/v_1$, the ratio of the vacuum expectation values of the two neutral Higgs doublet fields. The remaining two-fold ambiguity of the phase can be resolved by measuring the normal polarization of the charginos. Sum rules of the cross sections can be exploited to investigate the closure of the two-chargino system.
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Chargino Pair Production at $e^+e^-$ Colliders with Polarized Beams
The chargino $\tildeχ^\pm_{1,2}$ system can be reconstructed completely in $e^+e^-$ collisions. By measuring the total cross sections and the asymmetries with polarized beams in $e^+e^-\to\tildeχ_i^+ \tildeχ_j^- [i,j=1,2]$, the chargino masses and the gaugino-higgsino mixing angles of these states can be determined very accurately. If only the lightest charginos $\tildeχ_1^\pm$ are kinematically accessible, transverse beam polarization is needed to determine the mixing angles unambiguously. From these observables the fundamental SUSY parameters can be derived: the SU(2) gaugino mass $M_2$, the modulus and the cosine of the CP-violating phase of the higgsino mass parameter $μ$, and $\tanβ= v_2/v_1$, the ratio of the vacuum expectation values of the two neutral Higgs doublet fields. [The remaining two-fold ambiguity of the phase can be resolved by measuring the normal polarization of the charginos.]
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MSSM Higgs-Boson Production at Hadron Colliders with Explicit CP Violation
Gluon fusion is the main production mechanism for Higgs bosons with masses up to several hundred GeV in $pp$ collisions at the CERN Large Hadron Collider. We investigate the effects of the CP-violating phases on the fusion process including both the sfermion-loop contributions and the one-loop induced CP-violating scalar-pseudoscalar mixing in the minimal supersymmetric standard model. With a universal trilinear parameter assumed, every physical observable involves only the sum of the phases of the universal trilinear parameter $A$ and the higgsino mass parameter $μ$. The phase affects the lightest Higgs-boson production rate significantly through the neutral Higgs-boson mixing and, for the masses around the lightest stop-pair threshold, it also changes the production rate of the heavy Higgs bosons significantly through both the stop and sbottom loops and the neutral Higgs-boson mixing.
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Reconstruction of Basic Parameters from Chargino Production
The event characteristics of chargino pair production at e+e- collisions are explored to determine gaugino-higgsino mixing angles. We demonstrate that by measuring total cross sections and left-right asymmetries with polarized beams or angular correlations among chargino decay products the fundamental SUSY parameters M_2, μand tan(beta) can be uniquely determined in a model independent way.
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Determining SUSY Parameters in Chargino Pair Production in e^+e^- Collisions
In most supersymmetric theories, charginos $\tildeχ^\pm_{1,2}$ belong to the class of the lightest supersymmetric particles and they are easy to observe at e^+e^- colliders. By measuring the total cross sections and the left-right asymmetries with polarized beams as well as the angular correlations of the decay products of the charginos in $e^+e^-\to\tildeχ^-_i\tildeχ^+_j [i,j=1,2]$, the chargino masses and the gaugino-higgsino mixing angles can be determined. From these observables the relevant fundamental SUSY parameters can be derived: M_2, $|μ|$, $\cosΦ_μ$, and $\tanβ=v_2/v_1$. The solutions are unique.
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Decays of the MSSM Higgs Bosons with Explicit CP Violation
We study Higgs boson decays in the minimal supersymmetric standard model where the tree-level CP invariance of the Higgs potential is explicitly broken by loop effects of soft CP-violating Yukawa interactions related to scalar quarks of the third generation. The scalar-pseudoscalar mixing among two neutral CP-even Higgs bosons and one CP-odd Higgs boson due to explicit CP violation modifies their tree-level couplings to fermions, to the W^\pm and Z bosons and to Higgs bosons themselves significantly. We analyze the phenomenological impact of explicit CP violation on the branching ratios of the neutral Higgs boson decays in detail and discuss how to directly confirm the existence of explicit CP violation through τ^+ τ^- and t \bar{t} spin correlations in the decays of the neutral Higgs bosons into a tau-lepton pair and a top-quark pair.
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Neutralino-Nucleus Elastic Scattering in the MSSM with Explicit CP Violation
We re-investigate the neutralino-nucleus elastic scattering as a promising dark matter detection mechanism including contributions from the scalar-pseudoscalar mixing of neutral Higgs states and the induced phase between two Higgs doublets due to the CP-violating phases of the scalar top and bottom sectors in the minimal supersymmetric standard model. The spin-dependent part of the cross section turns out to be hardly affected by the CP-violating induced phase due to a mutually destructive unavoidable suppression mechanism of various relevant supersymmetric parameters. On the other hand, although the phase $Φ_μ$ of the higgsino mass parameter is set to be zero, the spin-independent part, which can dominate over the spin-dependent part for heavy nuclei, can be strongly dependent on the CP-violating scalar-pseudoscalar mixing and the induced phase, in particular, for a large $|μ|$, a small charged Higgs boson mass, and a large trilinear term $|A|$ compared to the SUSY breaking scale. For a small $\tanβ$ and a large $|μ|$, the spin-independent cross section is enhanced by an order of magnitude as the phase $Φ_A$ of the trilinear term increases up to $π$, while for a large $\tanβ$ and a large $|μ|$ the spin-independent cross section is significantly suppressed for non-zero values of the phase $Φ_A$.
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CP Phases in Correlated Production and Decay of Neutralinos in the Minimal Supersymmetric Standard Model
We investigate the associated production of neutralinos $e^+e^-\to\tildeχ^0_1\tildeχ^0_2$ accompanied by the neutralino leptonic decay $\tildeχ^0_2\to\tildeχ^0_1 \ell^+\ell^-$, taking into account initial beam polarization and production-decay spin correlations in the minimal supersymmetric standard model with general CP phases but without generational mixing in the slepton sector. The stringent constraints from the electron EDM on the CP phases are also included in the discussion. Initial beam polarizations lead to three CP--even distributions and one CP--odd distribution, which can be studied independently of the details of the neutralino decays. We find that the production cross section and the branching fractions of the leptonic neutralino decays are very sensitive to the CP phases. In addition, the production--decay spin correlations lead to several CP--even observables such as lepton invariant mass distribution, and lepton angular distribution, and one interesting T--odd (CP--odd) triple product of the initial electron momentum and two final lepton momenta, the size of which might be large enough to be measured at the high--luminosity future electron--positron collider or can play a complementary role in constraining the CP phases with the EDM constraints.
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