1,277 research outputs found
Chargino Pair Production at Colliders with Polarized Beams
The chargino system can be reconstructed completely
in collisions. By measuring the total cross sections and the
asymmetries with polarized beams in , the chargino masses and the gaugino-higgsino mixing angles of these
states can be determined very accurately. If only the lightest charginos
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 ,
the modulus and the cosine of the CP-violating phase of the higgsino mass
parameter , and , 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.]Comment: 19 pages including 4 figure
Determining tan(beta) in \tau\tau Fusion to SUSY Higgs Bosons at a Photon Collider
We investigate \tau\tau fusion to light h and heavy H and A Higgs bosons in
the Minimal Supersymmetric Standard Model (MSSM) at a photon collider as a
promising channel for measuring large values of tan(beta). For standard design
parameters of a photon collider an error \Delta tan(beta) \sim 1, uniformly for
tan(beta) \gsim 10, may be expected, improving on complementary measurements at
the LHC and e+e- linear colliders.Comment: 12 pages, 5 figure
Analysis of the neutralino system in supersymmetric theories
Charginos [(c)\tilde]± and neutralinos [(c)\tilde]0 in supersymmetric theories can be produced copiously at e+e- colliders and their properties can be measured with high accuracy. Consecutively to the chargino system, in which the SU(2) gaugino parameter M2, the higgsino mass parameter m and tanb can be determined, the remaining fundamental supersymmetry parameter in the gaugino/higgsino sector of the minimal supersymmetric extension of the Standard Model, the U(1) gaugino mass M1, can be analyzed in the neutralino system, including its modulus and its phase in CP-noninvariant theories. The CP properties of the neutralino system are characterized by unitarity quadrangles. Analytical solutions for the neutralino mass eigenvalues and the mixing matrix are presented for CP-noninvariant theories in general. They can be written in compact form for large supersymmetric mass parameters. The closure of the neutralino and chargino systems can be studied by exploiting sum rules for the pair-production processes in e+e- collisions. Thus the picture of the non-colored gaugino and higgsino complex in supersymmetric theories can comprehensively be reconstructed in these experiments
The Neutralino Sector of the Next-to-Minimal Supersymmetric Standard Model
The Next-to-Minimal Supersymmetric Standard Model (NMSSM) includes a Higgs
iso-singlet superfield in addition to the two Higgs doublet superfields of the
minimal extension. If the Higgs fields remain weakly coupled up to the GUT
scale, as naturally motivated by the concept of supersymmetry, the mixing
between singlet and doublet fields is small and can be treated perturbatively.
The mass spectrum and mixing matrix of the neutralino sector can be analyzed
analytically and the structure of this 5-state system is under good theoretical
control. We also determine decay modes and production channels in sfermion
cascade decays to these particles at the LHC and pair production in e+e-
colliders.Comment: 27 pages, 8 figure
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.Comment: 10 pages, 1 Postscript figure, sign typo correcte
Spin Analysis of Supersymmetric Particles
The spin of supersymmetric particles can be determined at colliders
unambiguously. This is demonstrated for a characteristic set of non-colored
supersymmetric particles -- smuons, selectrons, and charginos/neutralinos. The
analysis is based on the threshold behavior of the excitation curves for pair
production in collisions, the angular distribution in the production
process and decay angular distributions. In the first step we present the
observables in the helicity formalism for the supersymmetric particles.
Subsequently we confront the results with corresponding analyses of
Kaluza-Klein particles in theories of universal extra space dimensions which
behave distinctly different from supersymmetric theories. It is shown in the
third step that a set of observables can be designed which signal the spin of
supersymmetric particles unambiguously without any model assumptions. Finally
in the fourth step it is demonstrated that the determination of the spin of
supersymmetric particles can be performed experimentally in practice at an
collider.Comment: 39 pages, 14 figure
Reconstruction of superoperators from incomplete measurements
We present strategies how to reconstruct (estimate) properties of a quantum
channel described by the map E based on incomplete measurements. In a
particular case of a qubit channel a complete reconstruction of the map E can
be performed via complete tomography of four output states E[rho_j ] that
originate from a set of four linearly independent test states j (j = 1, 2, 3,
4) at the input of the channel. We study the situation when less than four
linearly independent states are transmitted via the channel and measured at the
output. We present strategies how to reconstruct the channel when just one, two
or three states are transmitted via the channel. In particular, we show that if
just one state is transmitted via the channel then the best reconstruction can
be achieved when this state is a total mixture described by the density
operator rho = I/2. To improve the reconstruction procedure one has to send via
the channel more states. The best strategy is to complement the total mixture
with pure states that are mutually orthogonal in the sense of the Bloch-sphere
representation. We show that unitary transformations (channels) can be uniquely
reconstructed (determined) based on the information of how three properly
chosen input states are transformed under the action of the channel.Comment: 13 pages, 6 figure
The Neutralino Sector in the U(1)-Extended Supersymmetric Standard Model
Motivated by grand unified theories and string theories we analyze the
general structure of the neutralino sector in the USSM, an extension of the
Minimal Supersymmetric Standard Model that involves a broken extra U(1) gauge
symmetry. This supersymmetric U(1)-extended model includes an Abelian gauge
superfield and a Higgs singlet superfield in addition to the standard gauge and
Higgs superfields of the MSSM. The interactions between the MSSM fields and the
new fields are in general weak and the mixing is small, so that the coupling of
the two subsystems can be treated perturbatively. As a result, the mass
spectrum and mixing matrix in the neutralino sector can be analyzed
analytically and the structure of this 6-state system is under good theoretical
control. We describe the decay modes of the new states and the impact of this
extension on decays of the original MSSM neutralinos, including radiative
transitions in cross-over zones. Production channels in cascade decays at the
LHC and pair production at colliders are also discussed.Comment: 50 pages, 9 figures, equations.sty include
SUSY Parameter Analysis at TeV and Planck Scales
Coherent analyses at future LHC and LC experiments can be used to explore the
breaking mechanism of supersymmetry and to reconstruct the fundamental theory
at high energies, in particular at the grand unification scale. This will be
exemplified for minimal supergravity.Comment: 7 pages, 3 figures, uses espcrc2.sty (included), Proceedings, Loops
and Legs 2004, Zinnowitz on Usedo
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