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TOPIC: Higgs Particles
Blobrana


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New light spin-zero boson
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Title: Evidence for a new light spin-zero boson from cosmological gamma-ray propagation?
Authors: Alessandro De Angelis, Marco Roncadelli, Oriana Mansutti
(Version v2)

Recent findings by Imaging Atmospheric Cherenkov Telescopes indicate a large transparency of the Universe to gamma rays, which can be hardly explained within the current models of extragalactic background light. We show that the observed transparency is naturally produced by an oscillation mechanism -- which can occur inside intergalactic magnetic fields -- whereby a photon can become a new spin-zero boson with mass m << 10^(-10) eV. Because the latter particle travels unimpeded throughout the Universe, photons can reach the observer even if the distance from the source considerably exceeds their mean free path. We compute the expected flux of gamma rays from blazar 3C279 at different energies. Our predictions can be tested in the near future by the gamma-ray telescopes H.E.S.S., MAGIC, CANGAROO and VERITAS. Moreover, our result provides an important observational test for models of dark energy wherein quintessence is coupled to the photon through an effective dimension-five operator.

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Blobrana


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RE: Higgs Particles
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Search for Neutral Higgs Bosons at High tan ß in multi-jet Events
The DŘ Collaboration

The full RunIIa data sample recorded at DŘ has been analysed to search for Neutral Higgs bosons produced in association with b-quarks at high tan  within the MSSM framework. The search has been performed in the three b-quarks channel using multi-jet triggered events corresponding to an integrated luminosity of ~ 0:9 fb^-1. No excess of events with respect to the predicted background is observed in the final selected three b-tag sample, so limits are set in the MSSM parameter space.



Leading order Feynman diagrams for neutral Higgs boson production in the five-flavour scheme (top) and four-flavour scheme (bottom).

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Blobrana


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Some call the Higgs boson the Holy Grail of particle physics. As the only undetected element of the field's theoretical masterpiecethe "standard model"the Higgs guarantees a Nobel Prize for the experimenters who find it first. Now the European Union has spent an estimated $8 billion to build the world's largest particle accelerator, the large hadron collider, to finally track it down.

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A anonymous physicist left a comment to a recent post here mentioning that the Dzero experiment is allegedly observing an excess of multi-b-quark events, asking me whether I have more details on the matter. Since I am not a member of the Dzero collaboration, it is too bad that the simple answer is NO. Too bad since I would not fear of being crucified if I did leak restricted information, as it would happen if it came from the CDF experiment.
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Blobrana


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WARNINGLABImage1

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Blobrana


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Posts: 131433
Date:
Higgs Field
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The problems in understanding the true nature of the vacuum of space were discussed by theoretical physicist Alvaro de Rújula from CERN (the European Council for Nuclear Research) in Geneva, Switzerland, and a professor of physics at Boston University at the EPL symposium, Physics In Our Times held today (10 May) at the Fondation Del Duca de lInstitut de France, Paris.

As it turns out, the vacuum is not empty - there is a difference between the vacuum and nothingness. Surprisingly, of all known substances, the vacuum is the least well understood - Alvaro de Rújula.

From the point of view of cosmology, the vacuum appears to have an energy density, which is sometimes called dark energy or the cosmological constant, responsible for the observed accelerated expansion of the universe. From a particle physics viewpoint, the vacuum is permeated by a Higgs Field - named after physicist Peter Higgs. In the Standard Model of particle physics (which has mapped the subatomic world with remarkable success for over 30 years), the masses of all particles are generated as a result of their interactions with this field.
It should also be possible to detect excitations of the Higgs field in the form of a particle known as the Higgs boson. Detecting the Higgs - the only particle in the Standard Model that has not been observed experimentally - is therefore one of the outstanding challenges in particle physics today. Scientists hope to detect the Higgs using CERNs Large Hadron Collider (LHC), due to come online in November this year. The LHC will be the worlds largest particle accelerator, colliding protons on protons at a total energy of 16 TeV (16x1012 eV) to generate what physicists hope will be a slew of new particles, including the Higgs.
The LHC will also search for many hypothetical particles other than the Higgs boson in what is called physics beyond the Standard Model, with supersymmetry being a promising candidate idea. Supersymmetric extensions of the Standard Model predict that all fundamental particles - such as quarks, photons and electrons - have cousins: their so-called `superpartners, yet to be discovered.
Dr. de Rújulas favourite achievement to date, in collaboration with Sheldon Glashow and Howard Georgi, has been understanding the masses of particles made of quarks.

My colleagues Arnon Dar and Shlomo Dado and I also believe we have recently solved the two main problems of high-energy astrophysics, gamma ray bursts and cosmic rays, but astrophysicists do not (yet) agree with this - Alvaro de Rújula.

Looking to the future, Dr. de Rújula believes that the LHC will teach us something fundamental. Apart from finding the Higgs, it is possible that the collider will produce the dark matter particles indirectly observed in the universe.

However, even if the LHC finds nothing this would also be very interesting because it would tell us that we havent understood anything about the vacuum. A complete lack of understanding often precedes a scientific revolution - Alvaro de Rújula.

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Blobrana


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RE: Higgs Particles
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Title: Significant Gamma Lines from Inert Higgs Dark Matter
Authors: Michael Gustafsson, Erik Lundstrom, Lars Bergstrom, Joakim Edsjo

If one has to explain dark matter by something else than supersymmetry, one of the most minimal solutions is adding another doublet of Higgs bosons. It has recently been noted, that if an unbroken discrete symmetry forbids the coupling to fermions of the new doublet, then the particle playing the role of the usual Higgs particle may naturally be very heavy, of the order of 500 GeV, without violating electroweak precision bounds. The lightest of the new scalar particles is a natural dark matter candidate, and for a mass between 10 and 80 GeV it can give the correct cosmic abundance as measured by WMAP. It would not yet have shown up in direct detection experiments, and for high Higgs masses also the indirect rates would seem rather small, in particular since tree-level processes giving W and Z final states are kinematically forbidden. However, we show that the loop-induced monochromatic \gamma\gamma and Z\gamma final states would be exceptionally strong for this dark matter candidate. The energy range and rates for these line processes make them ideal to search for in the soon upcoming GLAST satellite experiment.

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Blobrana


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Title: The Higgs field can be expressed through the lepton and quark fields
Authors: Ruslan Sharipov

The Higgs field is a central point of the Standard Model supplying masses to other fields through the symmetry breaking mechanism. However, it is associated with an elementary particle which is not yet discovered experimentally. In this short note I suggest a way for expressing the Higgs field through other fields of the Standard Model. If this is the case, being not an independent field, the Higgs field does not require an elementary particle to be associated with it.

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Blobrana


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Higgs boson: Glimpses of the God particle
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If the blips in the debris of the Tevatron particle smasher really are signs of the Higgs boson then it's not what we expected. It might mean that it's time to replace the standard model with a more complex picture of the universe
On 9 December last year, as John Conway looked at the results of his experiment, a chill ran down his neck. For 20 years he has been searching for one of the most elusive things in the universe, the Higgs boson - aka the God particle - which gives everything in the cosmos its mass. And here, buried in the debris generated by the world's largest particle smasher, were a few tantalising hints of its existence.
Conway first revealed the news of his experiment earlier this year in a blog. Experimental particle physicists are sceptics by nature, loath to claim the discovery of any new particle, let alone a particle of the Higgs's stature, and in his blog Conway dismissed hints of its existence as an aberration, just as many other supposed signs of the elusive particle have proved to be after closer examination. The tiny blips in Conway's data have so far simply refused to go away.

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Blobrana


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RE: Higgs Particles
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Scientists may be closing in on the most sought-after particle in physics.
The hypothetical Higgs boson, often dubbed the "God particle", is fundamental to our understanding of the Universe but has yet to be detected.
Now, data from the Tevatron particle collider at Fermilab, in the US, has enabled the most precise calculation yet to be made for its predicted mass.

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Blobrana


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W boson
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Scientists from around the World, including the UK, participating in the Collider Detector at Fermilab (CDF) collaboration at the Fermi National Accelerator Laboratory in Illinois announced today (8 January, 2007) the world's most precise measurement by a single experiment of the mass of the W boson, the carrier of the weak nuclear force and a key parameter of the Standard Model of particles and forces.
The new W-mass value leads to an estimate for the mass of the yet-undiscovered Higgs boson that is lighter than previously predicted, in principle making observation of this elusive particle more likely by experiments at the Tevatron particle collider at Fermilab.
Scientists working at the Collider Detector at Fermilab measured the mass of the W boson to be 80,413 ± 48 MeV/c˛, determining the particle's mass with a precision of 0.06 percent. Calculations based on the Standard Model intricately link the masses of the W boson and the top quark, a particle discovered at Fermilab in 1995, to the mass of the Higgs boson. By measuring the W-boson and top-quark masses with ever greater precision, physicists can restrict the allowable mass range of the Higgs boson, the missing keystone of the Standard Model.

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