197 research outputs found
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 and . 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
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