70 research outputs found
Contact interaction probes at the Linear Collider with polarized electron and positron beams
For contact-interaction searches at the Linear Collider, we discuss the
advantages of polarizing both the electron and the positron beams as compared
with polarizing only the electron beam. In particular, for the processes
e^+e^-\to \mu^+\mu^-, \tau^+\tau^-, b\bar{b} and c\bar{c} at a future e^+e^-
collider with \sqrt{s}=0.5 TeV we derive model-independent bounds on the
four-fermion contact interaction parameters from studies of the helicity cross
sections.Comment: 1+15 pages, LaTeX2e, including 7 figure
New physics signatures at a Linear Collider: model-independent analysis from `conventional' polarized observables
We discuss four-fermion contact-interaction searches in the processes
e^+e^-\to\mu^+\mu^-, c{\bar c} and b{\bar b} at a future e^+e^- Linear Collider
with c.m. energy \sqrt{s}=0.5 TeV and with both beams longitudinally polarized.
Our analysis is based on the measurements of familiar polarized observables
such as the total cross section and the forward-backward/left-right
asymmetries, and accounts for the general set of contact interaction couplings
as independent, non-zero, parameters thus avoiding simplifying,
model-dependent, assumptions. We derive the corresponding model-independent
constraints on the above-mentioned coupling constants, and evaluate the
corresponding reach at the Linear Collider, emphasizing the role of beam
polarization. We compare the results with a model-dependent procedure where
only one coupling is varied at a time.Comment: 13 pages, including 3 figure
Polarized observables to probe Z' at the e+e- linear collider
We study the sensitivity to the Z' couplings of the processes and at the linear collider with
with initial beam polarization, for typical extended model examples. To this
aim, we use suitable integrated, polarized, observables directly related to the
helicity cross sections that carry information on the individual Z' chiral
couplings to fermions. We discuss the derivation of separate, model-independent
limits on the couplings in the case of no observed indirect Z' signal within
the expected experimental accuracy. In the hypothesis that such signals were,
indeed, observed we assess the expected accuracy on the numerical determination
of such couplings and the consequent range of Z' masses where the individual
models can be distinguished from each other as the source of the effect.Comment: 14 pages, 4 figures, LaTe
Model-independent limits on four-fermion contact interactions at LC with polarization
Fermion compositeness, and other types of new physics that can be described
by the exchange of very massive particles, can manifest themselves as the
result of an effective four-fermion contact interaction. In the case of the
processes and at future
colliders with TeV, we examine the sensitivity to
four-fermion contact interactions of two new integrated observables,
and , conveniently defined for such kind of analysis. We find that,
if longitudinal polarization of the electron beam were available, these
observables would offer the opportunity to separate the helicity cross sections
and, in this way, to derive model-independent bounds on the relevant
parameters.Comment: 13 pages, LaTe
Investigation of Nanostructured Thermoelectric Material Si0.8Ge0.2P0.022 for Application in Multisectional Legs of Thermoelectric Elements
Complex investigations of high-temperature thermoelectric material nanostructured Si0.8Ge0.2P0.022 n-type were carried out. Temperature dependencies of conductivity, thermoelectric coefficient and thermal conductivity were studied. Obtained data were used for the calculation of temperature dependence of ZT. Maximum value of ZT =1.04 is observed at 900 °C. Differential scanning calorimetry indicates on the high thermal stability of the nanostructured material. It was established that optimal temperature range for the application of the material in the multisectional legs of thermoelements is 600-900 °C
Search for new physics indirect effects in at linear colliders with polarized beams
We discuss the potential of a linear collider to explore
manifestations of extended (or alternative) electroweak models of current
interest, through measurements of the reaction with both
initial and final states polarization. Specifically, we consider the
possibility to put stringent constraints on lepton mixing (or extended lepton
couplings) and mixing, showing in particular the usefulness of
polarization in order to disentangle these effects.Comment: 12 pages, latex, seven figures (available from [email protected]
Model independent constraints on contact interactions from LEP2
We quantitatively discuss the possibility of deriving model-independent
constraints on the general four-fermion contact interaction couplings, from the
currently available data on the two-fermion production processes
, and with unpolarized initial
beams. The method is essentially based on particular, simple, combinations of
the measured total cross section and forward-backward asymmetry that allow
partial separation of the helicity cross sections, and the combination of
experimental data obtained at the different energies of TRISTAN, LEP1 and LEP2.Comment: 9 pages (Latex) with 6 figures and 1 tabl
Role of beam polarization in the determination of and couplings from
We evaluate the constraints on anomalous trilinear gauge-boson couplings that
can be obtained from the study of electron-positron annihilation into pairs
at a facility with either the electron beam longitudinally polarized or both
electron and positron beams transversely polarized. The energy ranges
considered in the analysis are the ones relevant to the next-linear collider
and to LEP~200. We discuss the possibilities of a model independent analysis of
the general conserving anomalous effective Lagrangian, as well as its
restriction to some specific models with reduced number of independent
couplings. The combination of observables with initial and final state
polarizations allows to separately constrain the different couplings and to
improve the corresponding numerical bounds.Comment: 24 pages, LaTeX, 9 figures (available on request from the authors
Gap generation in the XXZ model in a transverse magnetic field
The ground state phase diagram of the 1D XXZ model in transverse magnetic
field is obtained. It consists of the gapped phases with different types of
long range order (LRO) and critical lines at which the gap and the LRO vanish.
Using scaling estimations and a mean-field approach as well as numerical
results we found critical indices of the gap and the LRO in the vicinity of all
critical lines.Comment: 4 pages, 1 figure, Late
Identification of extra neutral gauge bosons at the International Linear Collider
Heavy neutral gauge bosons, Z's, are predicted by many theoretical schemes of
physics beyond the Standard Model, and intensive searches for their signatures
will be performed at present and future high energy colliders. It is quite
possible that Z's are heavy enough to lie beyond the discovery reach expected
at the CERN Large Hadron Collider LHC, in which case only indirect signatures
of Z' exchanges may occur at future colliders, through deviations of the
measured cross sections from the Standard Model predictions. We here discuss in
this context the foreseeable sensitivity to Z's of fermion-pair production
cross sections at an e^+e^- linear collider, especially as regards the
potential of distinguishing different Z' models once such deviations are
observed. Specifically, we assess the discovery and identification reaches on
Z' gauge bosons pertinent to the E_6, LR, ALR and SSM classes of models, that
should be attained at the planned International Linear Collider (ILC). With the
high experimental accuracies expected at the ILC, the discovery and the
identification reaches on the Z' models under consideration could be increased
substantially. In particular, the identification among the different models
could be achieved for values of Z' masses in the discovery (but beyond the
identification) reach of the LHC. An important role in enhancing such reaches
is played by the electron (and possibly the positron) longitudinally polarized
beams. Also, although the purely leptonic processes are experimentally cleaner,
the measurements of c- and b-quark pair production cross sections are found to
carry important, and complementary, information on these searches.Comment: 21 page
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