64 research outputs found
Top quark spin in ep collision
We discuss the degree of spin polarization of single top quarks produced via
fusion process in collision at TESLA+HERAp and CLIC+LHC energies
and 5.3 TeV. A description on how to combine the cross sections
of and processes is given.
-beam direction is taken to be the favorite top quark spin decomposition
axis in its rest frame and it is found to be comparable with the ones in
collision. It is argued that theoretical simplicity and experimental clearness
are the advantage of collision.Comment: 2 eps figure
Search for electromagnetic properties of the neutrinos at the LHC
Exclusive production of neutrinos via photon-photon fusion provides an
excellent opportunity to probe electromagnetic properties of the neutrinos at
the LHC. We explore the potential of processes pp-> p gamma gamma p -> p nu
anti-nu p and pp -> p gamma gamma p -> p nu anti-nu Z p to probe
neutrino-photon and neutrino-two photon couplings. We show that these reactions
provide more than seven orders of magnitude improvement in neutrino-two photon
couplings compared to LEP limits.Comment: 11 pages, 4 tables, New backgrounds have been adde
Electroweak radiative corrections to the three channels of the process f_1 bar-f_1 ZA --> 0
We have calculated the electroweak radiative corrections at the O(alpha)
level to the three channels of the process f_1 bar-f_1 Z A --> 0 and
implemented them into the SANC system. Here A stands for the photon and f_1 for
a first generation fermion whose mass is neglected everywhere except in
arguments of logarithmic functions. The symbol --> 0 means that 4-momenta of
all the external particles flow inwards. We present the complete analytical
results for the covariant and helicity amplitudes for three cross channels: f_1
+ bar-f_1 --> Z + gamma, Z --> f_1 + bar-f_1 + gamma and f_1 + gamma --> f_1 +
Z. The one-loop scalar form factors of these channels are simply related by an
appropriate permutation of their arguments s,t,u. To check the correctness of
our results we first of all observe the independence of the scalar form factors
on the gauge parameters and the validity of the Ward identity, i.e. external
photon transversality, and, secondly, compare our numerical results with the
other independent calculations available to us.Comment: 19 pages, 6 figures, 10 table
Anomalous single production of the fourth SM family quarks at Tevatron
Possible single productions of fourth family u_{4} and d_{4} quarks via
anomalous q_{4}qV interactions at Tevatron are studied. Signature of such
processes are discussed and compared with the recent results from Tevatron.Comment: 6 pages, 1 figure, 4 table
Lepton distribution as a probe of new physics in production and decay of the t quark and its polarization
We investigate the possibilities of studying new physics in various processes
of t-quark production using kinematical distributions of the secondary lepton
coming from decay of t quarks. We show that the angular distributions of the
secondary lepton are insensitive to the anomalous tbW vertex and hence are pure
probes of new physics in a generic process of t-quark production. The energy
distribution of the lepton is distinctly affected by anomalous tbW couplings
and can be used to analyze them independent of the production process of t
quarks. The effects of t polarization on the distributions of the decay lepton
are demonstrated for top-pair production process at a gamma-gamma collider
mediated by a heavy Higgs boson.Comment: 15 pages, 7 figures, uses axodraw.sty (included), references added.
v3 to appear in Journal of High Energy Physics. Incorporates minor changes in
the discussion on radiative corrections which do not affect the results. Typo
in reference correcte
Resonant Production of Scalar Diquarks at the Next Generation Electron-Positron Colliders
We investigate the potential of TESLA and JLC/NLC electron-positron linear
collider designs to observe diquarks produced resonantly in processes involving
hard photons.Comment: 14 pages, 8 figures, coded in RevTEX, uses epsfi
Anomalous Single Production of the Fourth Generation Neutrino at Future ep Colliders
Possible single productions of the fourth standard model generation neutrino
via anomalous interactions at the future ep colliders are studied. Signatures
of such anomalous processes and backgrounds are discussed in detail. Discovery
limits for neutrino mass and achievable values of anomalous coupling strength
are determined.Comment: 11 pages, 6 figures, 5 table
Fourth Generation Pseudoscalar Quarkonium Production and Observability at Hadron Colliders
The pseudoscalar quarkonium state, eta_4 1^S_0, formed by the Standard Model
(SM) fourth generation quarks, is the best candidate among the fourth
generation quarkonia to be produced at the LHC and VLHC. The production of this
J^{PC} = 0^{-+} resonance is discussed and the background processes are studied
to obtain the integrated luminosity limits for the discovery, depending on its
mass.Comment: 13 pages, 4 figures, 5 table
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