Search results for "Higgs"
showing 10 items of 1127 documents
Light Composite Higgs from Higher Representations versus Electroweak Precision Measurements -- Predictions for LHC
2005
We investigate theories in which the technifermions in higher dimensional representations of the technicolor gauge group dynamically break the electroweak symmetry of the standard model. For the two-index symmetric representation of the gauge group the lowest number of techniflavors needed to render the underlying gauge theory quasi conformal is two. We confront the models with the recent electroweak precision measurements and demonstrate that the two technicolor theory is a valid candidate for a dynamical breaking of the electroweak symmetry. The electroweak precision measurements provide useful constraints on the relative mass splitting of the new leptons needed to cure the Witten anomaly…
Measurement of an excess ofB¯→D(*)τ−ν¯τdecays and implications for charged Higgs bosons
2013
The concept for this analysis is to a large degree based on earlier BABAR work and we acknowledge the guidance provided by M. Mazur. The authors consulted with theorists A. Datta, S. Westhoff, S. Fajfer, J. Kamenik, and I. Nisandzic on the calculations of the charged Higgs contributions to the decay rates. We are grateful for the extraordinary contributions of our PEP-II colleagues in achieving the excellent luminosity and machine conditions that have made this work possible. The success of this project also relied critically on the expertise and dedication of the computing organizations that support BABAR. The collaborating institutions wish to thank SLAC for its support and the kind hospi…
Combined search for the Higgs boson with the D0 experiment
2013
We perform a combination of searches for standard model Higgs boson production in $p\bar{p}$ collisions recorded by the D0 detector at the Fermilab Tevatron Collider at a center of mass energy of $\sqrt{s}=1.96$ TeV. The different production and decay channels have been analyzed separately, with integrated luminosities of up to 9.7 fb$^{-1}$ and for Higgs boson masses $90\leq M_H \leq 200$ GeV. We combine these final states to achieve optimal sensitivity to the production of the Higgs boson. We also interpret the combination in terms of models with a fourth generation of fermions, and models with suppressed Higgs boson couplings to fermions. The result excludes a standard model Higgs boson …
Update of the search for charginos nearly mass-degenerate with the lightest neutralino
2000
The data collected by DELPHI in 1998 at the centre-of-mass energy of 189 GeV have been used to update the search for charginos nearly mass-degenerate with the lightest supersymmetric particle, which is assumed to be the lightest neutralino. Mass differences below \Delta M = 3 GeV/c^2 are considered. No excess of events with respect to the Standard Model expectation has been observed, and exclusions in the plane of \Delta M versus chargino mass are given. The new \Delta M independent lower limit on the mass of the chargino is 62.4 GeV/c^2 in the higgsino scenario (which includes the gaugino mass unification scenario), if all sfermions are heavier than the lightest chargino. In the approximat…
A search for invisible Higgs bosons produced in e+e- interactions at LEP 2 energies
1999
Searches for HZ production with the Higgs boson decaying into an invisible final state have been performed with the data collected by the DELPHI experiment up to the centre-of-mass energy of 183 GeV. The hadronic and muon pair final states of the Z boson were analysed. From the absence of signal, upper limits on the cross-section and the corresponding Higgs boson mass limits were set at 95% confidence level. The results are interpreted as excluded parameter regions in the framework of the minimal supersymmetric standard model and in the simplest Majoron model with one Higgs doublet and one Higgs singlet field. (C) 1999 Elsevier Science B.V. All rights reserved.
The Hunt for New Physics at the Large Hadron Collider
2010
233 páginas.-- AHEP Group: et al..-- El Pdf del artículo es la versión pre-print: arXiv.1001.2693v1.-- Trabajo presentado al "The International Workshop on Beyond the Standard Model Physics and LHC Signatures (BSM-LHC) celebrado en Boston (USA) del 2 al 4 de junio de 2009.
Direct and indirect singlet scalar dark matter detection in the lepton-specific two-Higgs-doublet model
2011
A recent study of gamma-ray data from the Galactic Center motivates the investigation of light (~7-10 GeV) particle dark matter models featuring tau lepton pairs as dominant annihilation final state. The Lepton-Specific two-Higgs-doublet Model (2HDM-L) provides a natural framework where light, singlet scalar dark matter can pair-annihilate dominantly into tau leptons. We calculate the nucleon-dark matter cross section for singlet scalar dark matter within the 2HDM-L framework, and compare with recent results from direct detection experiments. We study how direct dark matter searches can be used to constrain the dark matter interpretation of gamma ray observations, for different dominant ann…
Higgs-Inflaton Mixing and Vacuum Stability
2019
The quartic and trilinear Higgs field couplings to an additional real scalar are renormalizable, gauge and Lorentz invariant. Thus, on general grounds, one expects such couplings between the Higgs and an inflaton in quantum field theory. In particular, the (often omitted) trilinear coupling is motivated by the need for reheating the Universe after inflation, whereby the inflaton decays into the Standard Model (SM) particles. Such a coupling necessarily leads to the Higgs-inflaton mixing, which could stabilize the electroweak vacuum by increasing the Higgs self-coupling. We find that the inflationary constraints on the trilinear coupling are weak such that the Higgs-inflaton mixing up to ord…
Search for di-muon decays of a low-mass Higgs boson in radiative decays of the Gamma(1S)
2013
We search for di-muon decays of a low-mass Higgs boson (A(0)) produced in radiative Gamma(1S) decays. The Gamma(1S) sample is selected by tagging the pion pair in the Gamma(2S, 3S) -> pi(+)pi(-) Gamma(1S) transitions, using a data sample of 92.8 x 10(6) Gamma(2S) and 116.8 x 10(6) Gamma(3S) events collected by the BABAR detector. We find no evidence for A(0) production and set 90% confidence level upper limits on the product branching fraction B(Gamma(1S) -> gamma Lambda(0)) x B(Lambda(0)->mu(+)mu(-)) in the range of (0.28 - 9.7) x 10(-6) for 0.212 gamma Lambda(0), Lambda(0) -> mu(+)mu(-) to set limits on the effective coupling of the b quark to the Lambda(0).
Measurements of the Lineshape of the $Z^{0}$ and Determination of Electroweak Parameters from its Hadronic and Leptonic Decays
1994
Abstract: During the LEP running periods in 1990 and 1991 DELPHI has accumulated approximately 450000 Z0 decays into hadrons and charged leptons. The increased event statistics coupled with improved analysis techniques and improved knowledge of the LEP beam energies permit significantly better measurements of the mass and width of the Z0 resonance. Model independent fits to the cross sections and leptonic forward-backward asymmetries yield the following Z0 parameters: the mass and total width M(Z) = 91.187 +/- 0.009 GeV, GAMMA(Z) = 2.486 +/- 0.012 GeV, the hadronic and leptonic partial widths GAMMA(had) = 1.725 +/- 0.012GeV, GAMMA(l) = 83.01 +/- 0.52 MeV, the invisible width GAMMA(inv) = 51…