In view of the discovery of a new boson by the ATLAS and CMS Collaborations at the LHC, we present an update of the global Standard Model (SM) fit to electroweak precision data. Assuming the new ...particle to be the SM Higgs boson, all fundamental parameters of the SM are known allowing, for the first time, to overconstrain the SM at the electroweak scale and assert its validity. Including the effects of radiative corrections and the experimental and theoretical uncertainties, the global fit exhibits a
p
-value of 0.07. The mass measurements by ATLAS and CMS agree within 1.3
σ
with the indirect determination
. Within the SM the
W
boson mass and the effective weak mixing angle can be accurately predicted to be
M
W
=80.359±0.011 GeV and
from the global fit. These results are compatible with, and exceed in precision, the direct measurements. For the indirect determination of the top quark mass we find
, in agreement with the kinematic and cross-section-based measurements.
We present an update of the Standard Model fit to electroweak precision data. We include newest experimental results on the top-quark mass, the
W
mass and width, and the Higgs-boson mass bounds from ...LEP, Tevatron and the LHC. We also include a new determination of the electromagnetic coupling strength at the
Z
pole. We find for the Higgs-boson mass
and
when not including and including the direct Higgs searches, respectively. From the latter fit we indirectly determine the
W
mass to be
. We exploit the data to determine experimental constraints on the oblique vacuum polarisation parameters, and confront these with predictions from the Standard Model (SM) and selected SM extensions. By fitting the oblique parameters to the electroweak data we derive allowed regions in the BSM parameter spaces. We revisit and consistently update these constraints for a fourth fermion generation, two Higgs doublet, inert Higgs and littlest Higgs models, models with large, universal or warped extra dimensions and technicolour. In most of the models studied a heavy Higgs boson can be made compatible with the electroweak precision data.
We present an update of the global fit of the Standard Model electroweak sector to latest experimental results. We include new kinematic top quark and
W
boson mass measurements from the LHC, a
sin
2
...θ
eff
ℓ
result from the Tevatron, and a new evaluation of the hadronic contribution to
α
(
M
Z
2
)
. We present tests of the internal consistency of the electroweak Standard Model and updated numerical predictions of key observables. The electroweak data combined with measurements of the Higgs boson coupling strengths and flavour physics observables are used to constrain parameters of two-Higgs-doublet models.
For a long time, global fits of the electroweak sector of the standard model (SM) have been used to exploit measurements of electroweak precision observables at lepton colliders (LEP, SLC), together ...with measurements at hadron colliders (Tevatron, LHC) and accurate theoretical predictions at multi-loop level, to constrain free parameters of the SM, such as the Higgs and top masses. Today, all fundamental SM parameters entering these fits are experimentally determined, including information on the Higgs couplings, and the global fits are used as powerful tools to assess the validity of the theory and to constrain scenarios for new physics. Future measurements at the Large Hadron Collider (LHC) and the International Linear Collider (ILC) promise to improve the experimental precision of key observables used in the fits. This paper presents updated electroweak fit results using the latest NNLO theoretical predictions and prospects for the LHC and ILC. The impact of experimental and theoretical uncertainties is analysed in detail. We compare constraints from the electroweak fit on the Higgs couplings with direct LHC measurements, and we examine present and future prospects of these constraints using a model with modified couplings of the Higgs boson to fermions and bosons.
The global fit of the Standard Model to electroweak precision data, routinely performed by the LEP electroweak working group and others, demonstrated impressively the predictive power of electroweak ...unification and quantum loop corrections. We have revisited this fit in view of (i) the development of the new generic fitting package,
Gfitter
, allowing for flexible and efficient model testing in high-energy physics, (ii) the insertion of constraints from direct Higgs searches at LEP and the Tevatron, and (iii) a more thorough statistical interpretation of the results. Gfitter is a modular fitting toolkit, which features predictive theoretical models as independent plug-ins, and a statistical analysis of the fit results using toy Monte Carlo techniques. The state-of-the-art electroweak Standard Model is fully implemented, as well as generic extensions to it. Theoretical uncertainties are explicitly included in the fit through scale parameters varying within given error ranges.
This paper introduces the Gfitter project, and presents state-of-the-art results for the global electroweak fit in the Standard Model (SM), and for a model with an extended Higgs sector (2HDM). Numerical and graphical results for fits with and without including the constraints from the direct Higgs searches at LEP and Tevatron are given. Perspectives for future colliders are analysed and discussed.
In the SM fit including the direct Higgs searches, we find
M
H
=116.4
−1.3
+18.3
GeV, and the 2
σ
and 3
σ
allowed regions 114,145 GeV and 113,168 and 180,225 GeV, respectively. For the strong coupling strength at fourth perturbative order we obtain
α
S
(
M
Z
2
)=0.1193
−0.0027
+0.0028
(exp )±0.0001 (theo). Finally, for the mass of the top quark, excluding the direct measurements, we find
m
t
=178.2
−4.2
+9.8
GeV. In the 2HDM we exclude a charged-Higgs mass below 240 GeV at 95% confidence level. This limit increases towards larger tan
β
, e.g.,
is excluded for tan
β
=70.
ZFITTER is a Fortran program for the calculation of fermion pair production and radiative corrections at high energy
e
+
e
−
colliders; it is also suitable for other applications where electroweak ...radiative corrections appear.
ZFITTER is based on a semi-analytical approach to the calculation of radiative corrections in the Standard Model. We present a summary of new features of the
ZFITTER program version 6.42 compared to version 6.21. The most important additions are: (i) some higher-order QED corrections to fermion pair production, (ii) electroweak one-loop corrections to atomic parity violation, (iii) electroweak one-loop corrections to
ν
¯
e
ν
e
production, (iv) electroweak two-loop corrections to the
W boson mass and the effective weak mixing angle.
Title of program:
ZFITTER version 6.42 (18 May 2005)
Catalogue identifier:ADMJ_v2_0
Program summary URL:
http://cpc.cs.qub.ac.uk/summaries/ADMJ_v2_0
Authors of original program: D. Bardin, P. Christova, M. Jack, L. Kalinovskaya, A. Olshevski, S. Riemann, T. Riemann
Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland
Reference for
ZFITTER version 6.21:
D. Bardin et al., Comput. Phys. Comm. 133 (2001) 229–395
Operating system:
UNIX/LINUX, program tested under, e.g.,
HP-UX and
PC/Linux
Programming language used:
FORTRAN 77
High speed storage required: <2 MB
No. of lines in distributed program, including test data, etc.:29 164
No. of bytes in distributed program, including test data, etc.:185 824
Distribution format:tar.gz
Does the new version supersede the previous version:Yes
Nature of the physical problem: Fermion pair production is an important reaction for precision tests of the Standard Model, at LEP/SLC and future linear colliders at higher energies. For this purpose, QED, electroweak and QCD radiative corrections have to be calculated with high precision, including higher order effects. Multi parameter fits used to extract model parameters from experimental measurements require a program of sufficient flexibility and high calculational speed.
ZFITTER combines these two aspects by employing analytical integrations of matrix elements and at most one-dimensional numerical integration, as well as a variety of flags defining the physics content used. The calculated predictions are typically at the per mille precision level, sometimes better.
Method of solution: Numerical integration of analytical formulae.
Reasons for new version:Addition of substantial material into the code: covering of more reactions; more accurate description of existing reactions.
Summary of revisions:New parts for predicting atomic parity violation and for neutrino pair production; more accurate higher order QED corrections for fermion pair production; two-loop corrections to the predictions of
W mass and of the weak mixing angle.
Restrictions on the complexity of the problem: Fermion pair production is described below the top quark pair production threshold. Photonic corrections are taken into account with simple cuts on photon energy, or the energies and acollinearity of the two fermions, and
one fermion production angle. The treatment of Bhabha scattering is less advanced.
Typical running time: On a Pentium IV PC installation (2.8 GHz) using g77 under Linux 2.4.21, approximately 23 s are needed to run the standard test of subroutine
ZFTEST. This result is for a
default/recommended setting of the input parameters, with
all corrections in the Standard Model switched
on.
ZFTEST computes 12 cross-sections and cross-section asymmetries for 8 energies with 5 interfaces, i.e. about 360 cross-sections in 23 s.
Design study of an optical cavity for a future photon collider at ILC Klemz, G.; Mönig, K.; Will, I.
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
08/2006, Letnik:
564, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Hard photons well above 100
GeV have to be generated in a future photon collider which essentially will be based on the infrastructure of the planned
International Linear Collider (ILC). The energy ...of near-infrared laser photons will be boosted by Compton backscattering against a high-energy relativistic electron beam. For high effectiveness, a very powerful laser system is required that exceeds today's state-of-the-art capabilities. In this paper a design of an auxiliary passive cavity is discussed that resonantly enhances the peak-power of the laser. The properties and prospects of such a cavity are addressed on the basis of the specifications for the European
TeV Energy Superconducting Linear Accelerator (TESLA) proposal. Those of the ILC are expected to be similar.
A study of the measurement of the two photon decay width times the branching ratio of the Standard Model Higgs boson with a mass of 120 GeV in photon–photon collisions is presented, assuming a
γ
γ
...integrated luminosity of 80 fb
−1
in the high energy part of the spectrum. The analysis is based on the reconstruction of the Higgs events produced in the
γ
γ
→H process, followed by the decay of the Higgs into a
pair. A statistical error of the measurement of the two-photon width,
Γ
(H→
γ
γ
), times the branching ratio of the Higgs boson, BR
is found to be 2.1% for one year of data taking.
We present a study of the sensitivity of the International Linear Collider (ILC) to electroweak parameters in the absence of a light Higgs boson. In particular, we consider those parameters that have ...been inaccessible at previous colliders, quartic gauge couplings. Within a generic effective-field theory context we analyze all processes that contain quasi-elastic weak-boson scattering, using complete six-fermion matrix elements in unweighted event samples, fast simulation of the ILC detector, and a multi-dimensional parameter fit of the set of anomalous couplings. The analysis does not rely on simplifying assumptions such as custodial symmetry or approximations such as the equivalence theorem. We supplement this by a similar new study of triple weak-boson production, which is sensitive to the same set of anomalous couplings. Including the known results on triple gauge couplings and oblique corrections, we thus quantitatively determine the indirect sensitivity of the ILC to new physics in the electroweak symmetry-breaking sector, conveniently parameterized by real or fictitious resonances in each accessible spin/isospin channel.
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