260 research outputs found
Branching Fraction Measurements of the SM Higgs with a Mass of 160 GeV at Future Linear \ee Colliders
Assuming an integrated luminosity of 500 fb and a center-of-mass
energy of 350 GeV, we examine the prospects for measuring branching fractions
of a Standard Model-like Higgs boson with a mass of 160 GeV at the future
linear \ee collider TESLA when the Higgs is produced via the Higgsstrahlung
mechanism, \ee \pfr HZ. We study in detail the precisions achievable for the
branching fractions of the Higgs into WW, ZZ and \bb. However, the
measurement of BF(H \pfr \gaga) remains a great challence. Combined with the
expected error for the inclusive Higgsstrahlung production rate the uncertainty
for the total width of the Higgs is estimated.Comment: 17 pages Latex, including 7 figure
Probe of the Wtb coupling in pair production at Linear Colliders
The Wtb vertex can be probed on future colliders in the processes of single
top production (LHC, pp mode, NLC, mode) and of top pair production
(NLC, e^+ e^- mode). We analyse observables sensitive to anomalous Wtb
couplings in the top pair production process of e^+ e^- collisions. In
particular, forward-backward and spin-spin asymmetries of the top decay
products and the asymmetry of the lepton energy spectum are considered.
Possible bounds on anomalous couplings obtained are competitive to those
expected from the upgraded Tevatron and LHC. The validity of the infinitely
small width approximation for the three-body top decay is also studied in
detail.Comment: 23 pages, 6 figures, uses axodraw.st
Higgs and Top Production in the Reaction at TeV Linear Collider Energies
For an electron-photon collider the complete tree-level cross sections of the
reaction are computed at center-of-mass
energies between 0.5 and 2.0 TeV, for top masses of 160 to 200 GeV and Higgs
masses between 80 and 140 GeV within the Standard Model. It is shown that most
of the events are due to Higgs and production
(with decay) while top production (with
decay) is about 50% smaller. Multiperipheral background and
interferences are small, respectively negligible, in the energy range studied.
By convoluting the basic cross sections with an energy spectrum of the
backscattered photon beam, and inserting linear collider luminosities as
anticipated in present designs, realistic event rates are
estimated. This results in large event rates for
and . We estimate that the CKM matrix element
, can be probed from the final state to an accuracy of 1-3%
at . Assuming an effective Lagrangian based on
dimension-6 operators we discuss the sensitivity for detecting deviations of
the HWW coupling from the Standard Model in the reaction .Comment: 18 pages Latex, including 8 eps-figures To be appear in Zeitschrift
f. Physik
Single Top Production in , , and Collisions
Single top quark cross section evaluations for the complete sets of
tree-level diagrams in the , , and
modes of the next linear collider with unpolarized and polarized beams are
performed within the Standard Model and beyond. From comparison of all
possibilities we conclude that the process is
extremely favoured due to large cross section, no background, high
degrees of beam polarization, and exceptional sensitivities to and
anomalous couplings. Similar reasons favour the process for probing top quark properties despite a considerably lower
cross section. Less favourable are processes like . Three processes were chosen to probe their sensitivity to
anomalous couplings, with best bounds found for and .Comment: 23 pages, 13 figure
Higgs Search in the WW* Decay Mode at Photon Linear Colliders
We present the results of calculations for the process gamma gamma -> W + 2
fermions at a future Photon Linear Collider (PLC). The calculations include at
the same time the next-to-leading order Higgs signal and the complete tree
level gauge boson background. We present numerical results in the intermediate
mass Higgs region 140 GeV < M_H < 2M_W. We propose strategies for the
determination of Higgs properties using the leptonic and hadronic final states
for both polarized and unpolarized photon beams.Comment: 14 pages, LaTeX (using amsmath.sty), 4 EPS figures include
An analytical program for fermion pair production in e+e- annihilation
We describe how to use {\tt ZFITTER}, a program based on a semi-analytical approach to fermion pair production in e^+ e^- annihilation and Bhabha scattering. A flexible treatment of complete {\cal O}(\alpha) QED corrections, also including higher orders, allows for three calculational {\bf chains} with different realistic sets of restrictions in the photon phase space. {\tt ZFITTER} consists of several {\bf branches} with varying assumptions on the underlying hard scattering process. One includes complete {\cal O}(\alpha) weak loop corrections with a resummation of leading higher-order terms. Alternatively, an ansatz inspired from S-matrix theory, or several model-independent effective Born cross sections may be convoluted. The program calculates cross sections, forward-backward asymmetries, and for \tau~pair production also the final-state polarization. Various {\bf interfaces} allow fits to be performed with different sets of free parameters
TESLA Technical Design Report Part III: Physics at an e+e- Linear Collider
The TESLA Technical Design Report Part III: Physics at an e+e- Linear
ColliderComment: 192 pages, 131 figures. Some figures have reduced quality. Full
quality figures can be obtained from http://tesla.desy.de/tdr. Editors -
R.-D. Heuer, D.J. Miller, F. Richard, P.M. Zerwa
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