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.Comment: 10 pages, 8 eps figures, LaTeX, uses JHEP3.cls; talk given at the International Workshop on Astroparticle and High Energy Physics (AHEP), Valencia, Spain, 14-18 Oct. 200

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 \mu and 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.Comment: 23 pages, 7 figure

Quantum response of dephasing open systems

We develop a theory of adiabatic response for open systems governed by Lindblad evolutions. The theory determines the dependence of the response coefficients on the dephasing rates and allows for residual dissipation even when the ground state is protected by a spectral gap. We give quantum response a geometric interpretation in terms of Hilbert space projections: For a two level system and, more generally, for systems with suitable functional form of the dephasing, the dissipative and non-dissipative parts of the response are linked to a metric and to a symplectic form. The metric is the Fubini-Study metric and the symplectic form is the adiabatic curvature. When the metric and symplectic structures are compatible the non-dissipative part of the inverse matrix of response coefficients turns out to be immune to dephasing. We give three examples of physical systems whose quantum states induce compatible metric and symplectic structures on control space: The qubit, coherent states and a model of the integer quantum Hall effect.Comment: Article rewritten, two appendices added. 16 pages, 2 figure

T-odd Correlations in the Decay of Scalar Fermions

We define a CP sensitive asymmetry in the sfermion decays \ti f \to f \ti\chi^0_j \ell \bar \ell, f \ti\chi^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 $\mu$ and $M_1$. The leading contribution stems from the decay chain \ti f\to f \ti\chi^0_j\to f \ti\chi^0_1 Z\to f \ti\chi^0_1 \ell \bar \ell (f \ti\chi^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 \ti\chi^0_1 \ell \bar \ell, and up to 20% for \ti f\to f \ti\chi^0_1 q \bar q. We also estimate the rates necessary to measure the asymmetry.Comment: 18 pages, 5 figures, 2 tables; comments and references added; two tables added; version to appear in Eur. Phys.

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 \mu the 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.Comment: 10 pages, 3 figure

CP asymmetries in neutralino production in e+e- collisions

We study two CP sensitive triple-product asymmetries for neutralino production e+e- \to\tilde\chi^0_i \tilde\chi^0_j and the subsequent leptonic two-body decay \tilde\chi^0_i \to \tilde l l, \tilde l \to \tilde\chi^0_1 l, for \l= e,\mu,\tau. We calculate the asymmetries, cross sections and branching ratios in the Minimal Supersymmetric Standard Model with complex parameters \mu and 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.Comment: 22 pages, 7 figures; typos corrected, version to appear in Phys. Rev.

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 \mu and 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.Comment: 21 pages, 8 figures, comments and references added; version to appear in Eur. Phys. J.

CP-odd observables in neutralino production with transverse e+ and e- beam polarization

We consider neutralino production and decay e^+e^ --> chi^0_i chi^0_j, chi^0_j --> chi^0_1 f \bar{f} at a linear collider with transverse e^+ and e^- beam polarization. We propose CP asymmetries by means of the azimuthal distribution of the produced neutralinos and of that of the final leptons, while taking also into account the subsequent decays of the neutralinos. We include the complete spin correlations between production and decay. Our framework is the Minimal Supersymmetric Standard Model with complex parameters. In a numerical study we show that there are good prospects to observe these CP asymmetries at the International Linear Collider and estimate the accuracy expected for the determination of the phases in the neutralino sector.Comment: 30 pages, minor changes in the introduction, references adde

From Deep Inelastic Scattering to Photoproduction: A Unified Approach

The strikingly different high energy behaviours of real photoabsorption cross-sections with Q^2 = 0 and the low x proton structure function at large Q^2 are studied from a laboratory frame viewpoint, in which the x and Q^2 dependence reflects the space-time structure of the interaction. This is done using a simple model which incorporates hadron dominance, but attributes the striking enhancement observed at HERA at very low x and high Q^2 to contributions from heavy long-lived fluctuations of the incoming photon. Earlier published predictions of the model for the then unknown behaviour of the structure function at small x and intermediate Q^2 are shown to be strikingly confirmed by recent experimental data. A simultaneous analysis of real photoabsorption data and structure function data for 0 <= x < 0.1 and 0 <= Q^2 <= 15 GeV^2 is then reported. An excellent fit is obtained, with all parameters in the restricted ranges allowed by other physical requirements.Comment: 23 pages, LaTex, 11 figures, Submitted to Physical Revie