arXiv subjects

A. Bartl

Publications and source records attributed to A. Bartl.

At least 55 records · Page 3Linked to original sources

arXiv2004

Effects of CP phases on the Phenomenology of SUSY Particles

We review our recent studies on the effects of CP-violating supersymmetric (SUSY) parameters on the phenomenology of neutralinos, charginos and third generation squarks. The CP-even branching ratios of the squarks show a pronounced dependence on the phases of A_t, A_b, mu and M_1 in a large region of the supersymmetric parameter space, which can be used to get information on these phases. In addition we have studied CP-odd observables, like asymmetries based on triple product correlations. In neutralino and chargino production with subsequent three-body decays these asymmetries can be as large as 20%.

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arXiv2004

CP sensitive observables in chargino production and decay into a W boson

We study CP sensitive observables in chargino production in electron-positron collisions with subsequent two-body decay of one chargino into a W boson. We identify the CP odd elements of the W boson density matrix and propose CP sensitive triple-product asymmetries of the chargino decay products. We calculate the density-matrix elements, the CP asymmetries and the cross sections in the Minimal Supersymmetric Standard Model with complex parameters μand M_1 for an e+ e- linear collider with \sqrt{s} = 800 GeV and longitudinally polarized beams. The asymmetries can reach 7% and we discuss the feasibility of measuring these asymmetries.

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arXiv2004

Impact of CP phases on the search for top and bottom squarks

We study the decays of top squarks (~t_{1,2}) and bottom squarks (~b_{1,2}) in the Minimal Supersymmetric Standard Model (MSSM) with complex parameters A_t, A_b, mu and M_1. We show that including the corresponding phases strongly affects the branching ratios of ~t_{1,2} and ~b_{1,2} decays in a large domain of the MSSM parameter space. This could have an important impact on the search for ~t_{1,2} and ~b_{1,2} and the determination of the underlying MSSM parameters at future colliders.

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arXiv2004

Physics Possibilities at a Linear Collider

We review some recent studies about the parameter determination of top quarks, W bosons, Higgs bosons, supersymmetric particles and in the ADD model of extra dimensions at a linear collider.

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arXiv2004

CP sensitive observables in chargino production with transverse $e^{\pm}$ beam polarization

We consider the process $e^+e^-\to\tiχ^+_i\tiχ^-_j$ at a linear collider with transverse $e^{\pm}$ beam polarization. We investigate the influence of the CP phases on azimuthal asymmetries in $e^+e^-\to\tiχ^+_i\tiχ^-_j$ with subsequent two-body decays $\tiχ^-_j\to \tiν_{\ell}\ell^-$ and $\tiχ^-_j\to W^-\tiχ^0_1$. We show that triple product correlations involving the transverse $e^{\pm}$ beam polarization vanish if at least one subsequent chargino decay is not observed. We derive this result within the Minimal Supersymmetric Standard Model (MSSM) with complex parameters, however, it holds also in the general MSSM with SUSY flavour violation.

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arXiv2004

CP violation in chargino production and decay into sneutrino

We study CP odd asymmetries in chargino production E+ E- --> ~Chi(+-)(1) Chi(-+)(2) and the subsequent two-body decay of one chargino into a sneutrino. We show that in the Minimal Supersymmetric Standard Model with complex parameter μthe asymmetries can reach 30 %. We discuss the feasibility of measuring these asymmetries at a linear collider with \sqrt{s} = 800 GeV and longitudinally polarized beams.

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arXiv2004

CP sensitive observables in e+e- -> neutralino_i neutralino_j and neutralino decay into the Z boson

We study CP sensitive observables in neutralino production e+e- -> neutralino_i neutralino_j and the subsequent two-body decays of the neutralino neutralino_i -> neutralino_n Z and of the Z boson Z -> l \bar l (q \bar q). We identify the CP odd elements of the Z boson density matrix and propose CP sensitive triple-product asymmetries. We calculate these observables and the cross sections in the Minimal Supersymmetric Standard Model with complex parameters μand M_1 for an e+e- linear collider with \sqrt{s}=800 GeV and longitudinally polarized beams. We show that the asymmetries can reach 3% for Z -> l \bar l and 18% for Z -> q \bar q and discuss the feasibility of measuring these asymmetries.

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arXiv2004

Top Squarks and Bottom Squarks in the MSSM with Complex Parameters

We present a phenomenological study of top squarks (~t_1,2) and bottom squarks (~b_1,2) in the Minimal Supersymmetric Standard Model (MSSM) with complex parameters A_t, A_b, μand M_1. In particular we focus on the CP phase dependence of the branching ratios of (~t_1,2) and (~b_1,2) decays. We give the formulae of the two-body decay widths and present numerical results. We find that the effect of the phases on the (~t_1,2) and (~b_1,2) decays can be quite significant in a large region of the MSSM parameter space. This could have important implications for (~t_1,2) and (~b_1,2) searches and the MSSM parameter determination in future collider experiments. We have also estimated the accuracy expected in the determination of the parameters of ~t_i and ~b_i by a global fit of the measured masses, decay branching ratios and production cross sections at e^+ e^- linear colliders with polarized beams. Analysing two scenarios, we find that the fundamental parameters apart from A_t and A_b can be determined with errors of 1% to 2%, assuming an integrated luminosity of 1 ab^-1 and a sufficiently large c.m.s. energy to produce also the heavier ~t_2 and ~b_2 states. The parameter A_t can be determined with an error of 2 - 3%, whereas the error on A_b is likely to be of the order of 50%.

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arXiv2004

Transverse beam polarization and CP-violating triple-gauge-boson couplings in e+e- -> gamma Z

We show that an anomalous CP-violating gamma-gamma-Z vertex gives rise to a novel asymmetry with transversely polarized electron and positron beams in the process e+e- -> gamma Z. This asymmetry, which is odd under naive time reversal, is proportional to the real part of the gamma-gamma-Z CP-violating coupling. This is in contrast to the simple forward-backward asymmetry of the gamma (or Z) with unpolarized or longitudinally polarized beams studied earlier, which is even under naive time reversal, and is proportional to the imaginary part. We estimate the sensitivity of future experiments to the determination of CP-odd gamma-gamma-Z and gamma-Z-Z couplings using these asymmetries and transversely polarized beams.

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arXiv2003

Impact of CP phases on SUSY particle production and decays

We report on the results of a phenomenological study of top squarks (stop_{1,2}) and bottom squarks (sbottom_{1,2}) in the Minimal Supersymmetric Standard Model (MSSM) with complex parameters A_t, A_b, mu and M_1. In particular we focus on the CP phase dependence of the branching ratios of stop_{1,2} and sbottom_{1,2} decays. We find that the effect of the phases on the stop_{1,2} and sbottom_{1,2} decays can be quite significant in a large region of the MSSM parameter space. We also study a CP asymmetry in sfermion decays.

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arXiv2003

CP asymmetries in neutralino production in e+e- collisions

We study two CP sensitive triple-product asymmetries for neutralino production e+e- \to\tildeχ^0_i \tildeχ^0_j and the subsequent leptonic two-body decay \tildeχ^0_i \to \tilde l l, \tilde l \to \tildeχ^0_1 l, for ł= e,μ,τ. We calculate the asymmetries, cross sections and branching ratios in the Minimal Supersymmetric Standard Model with complex parameters μand M_1. We present numerical results for the asymmetries to be expected at a linear electron-positron collider in the 500 GeV range. The asymmetries can go up to 25 %. We estimate the event rates which are necessary to observe the asymmetries. Polarized electron and positron beams can significantly enhance the asymmetries and cross sections. In addition, we show how the two decay leptons can be distinguished by making use of their energy distributions.

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arXiv2003

T-odd Correlations in the Decay of Scalar Fermions

We define a CP sensitive asymmetry in the sfermion decays $\ti f \to f \tiχ^0_j \ell \bar \ell, f \tiχ^0_j q \bar q$, based on triple product correlations between the momenta of the outgoing fermions. We study this asymmetry in the MSSM with complex parameters. We show that the asymmetry is sensitive to the phases of the parameters $μ$ and $M_1$. The leading contribution stems from the decay chain $\ti f\to f \tiχ^0_j\to f \tiχ^0_1 Z\to f \tiχ^0_1 \ell \bar \ell (f \tiχ^0_1 q \bar q)$, for which we obtain analytic formulae for the amplitude squared. The asymmetry can go up to 3% for $\ti f\to f \tiχ^0_1 \ell \bar \ell$, and up to 20% for $\ti f\to f \tiχ^0_1 q \bar q$. We also estimate the rates necessary to measure the asymmetry.

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arXiv2003

Testing the Mechanism of R-parity Breaking with Slepton LSP Decays

In supersymmetric models R-parity can be violated through either bilinear or trilinear terms in the superpotential, or both. If charged scalar leptons are the lightest supersymmetric particles, their decay properties can be used to obtain information about the relative importance of these couplings. We show that in some specific scenarios it is even possible to decide whether bilinear or trilinear terms give the dominant contribution to the neutrino mass matrix.

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arXiv2003

Impact of beam polarization on CP asymmetries in neutralino pair production

We analyze the dependence of CP-odd asymmetries on longitudinally polarized e+ and e- beams in neutralino production and subsequent leptonic two-body decays. We give numerical examples of the asymmetries and of the cross sections in the Minimal Supersymmetric Standard Model with complex parameters mu, M_1 and A_{tau} for a collider with sqrt{s}=500 GeV. We show that longitudinally polarized electron and positron beams can enhance considerably both the asymmetries and the cross sections.

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arXiv2003

A CP asymmetry in e^+e^- \to χ^0_iχ^0_j \to χ^0_j τstau_k with tau polarization

We propose a CP-odd asymmetry in the supersymmetric process e^+e^- \to χ^0_i χ^0_j \to χ^0_j τstau_k by means of the transverse τpolarization. We calculate the asymmetry and cross sections at a future linear collider in the 500 GeV c.m.s. energy range with longitudinal polarized beams and high luminosity. We work in the Minimal Supersymmetric Standard Model with complex parameters μ, M_1 and A_τ. The asymmetry can reach values up to 60 %. We also estimate the sensitivity for measuring the τpolarization necessary to probe the CP asymmetry.

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arXiv2003

Impact of SUSY CP Phases on Stop and Sbottom Decays in the MSSM

We study the decays of top squarks and bottom squarks in the Minimal Supersymmetric Standard Model with complex parameters A_t, A_b and mu. In a large region of the supersymmetric parameter space the branching ratios of stop_1 and sbottom_1 show a pronounced phase dependence. This could have an important impact on the search for stop_1 and sbottom_1 at a future linear collider and on the determination of the supersymmetric parameters.

hep-ph↗

arXiv2003

CP asymmetries in neutralino production

We study two CP sensitive triple-product asymmetries for neutralino production e+e- \to \tildeχ^0_i \tildeχ^0_j and the subsequent leptonic two-body decays \tildeχ^0_i \to \tilde{l} l of one of the neutralinos and of the slepton \tilde{l} \to \tildeχ^0_1 l at an e+e--linear collider with \sqrt{s} = 500 GeV. We calculate the asymmetries in the Minimal Supersymmetric Standard Model with complex parameters μand M_1. We show that the largest asymmetries are 10% or 25% and estimate the event rates which are necessary to measure the asymmetries. Polarized electron and positron beams can significantly enhance the asymmetries and cross sections. In addition, we show how the two decay leptons can be distinguished by making use of their energy distributions.

hep-ph↗

arXiv2003

Impact of CP phases on stop and sbottom searches

We study the decays of top squarks (stop_{1,2}) and bottom squarks (sbottom_{1,2}) in the Minimal Supersymmetric Standard Model (MSSM) with complex parameters A_t, A_b, mu and M_1. We show that including the corresponding phases substantially affects the branching ratios of stop_{1,2} and sbottom_{1,2} decays in a large domain of the MSSM parameter space. We find that the branching ratios can easily change by a factor of 2 and more when varying the phases. This could have an important impact on the search for stop_{1,2} and sbottom_{1,2} and the determination of the MSSM parameters at future colliders.

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