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TOPIC: Higgs Particles


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New Higgs detection 'closes circle

Physicists who detected a version of the Higgs Boson in a superconductor say their discovery closes a "historical circuit".
They also stressed that the low-energy work was completely separate" from the famous evidence gathered by the Large Hadron Collider.

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Title: Probable or Improbable Universe? Correlating Electroweak Vacuum Instability with the Scale of Inflation
Author: Anson Hook, John Kearney, Bibhushan Shakya, Kathryn M. Zurek

Measurements of the Higgs boson and top quark masses indicate that the Standard Model Higgs potential becomes unstable around \Lambda_I ~ 10^{11} GeV. This instability is cosmologically relevant since quantum fluctuations during inflation can easily destabilise the electroweak vacuum if the Hubble parameter during inflation is larger than \Lambda_I (as preferred by the recent BICEP2 measurement). We perform a careful study of the evolution of the Higgs field during inflation, obtaining different results from those currently in the literature. We consider both tunneling via a Coleman-de Luccia or Hawking-Moss instanton, valid when the scale of inflation is below the instability scale, as well as a statistical treatment via the Fokker-Planck equation appropriate in the opposite regime. We show that a better understanding of the post-inflation evolution of the unstable AdS vacuum regions is crucial for determining the eventual fate of the universe. If these AdS regions devour all of space, a universe like ours is indeed extremely unlikely without new physics to stabilise the Higgs potential; however, if these regions crunch, our universe survives, but inflation must last a few e-folds longer to compensate for the lost AdS regions. Lastly, we examine the effects of generic Planck-suppressed corrections to the Higgs potential, which can be sufficient to stabilize the electroweak vacuum during inflation.

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Baby universe rumbled with thunder of Higgs bubbles

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Higgsogenesis
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Title: Baryogenesis through split Higgsogenesis
Author: Sacha Davidson, Ricardo Gonzalez Felipe, H. Serodio, Joao P. Silva

We study the cosmological evolution of asymmetries in the two-Higgs doublet extension of the Standard Model, prior to the electroweak phase transition. If Higgs flavour-exchanging interactions are sufficiently slow, then a relative asymmetry among the Higgs doublets corresponds to an effectively conserved quantum number. Since the magnitude of the Higgs couplings depends on the choice of basis in the Higgs doublet space, we attempt to formulate basis-independent out-of-equilibrium conditions. We show that an initial asymmetry between the Higgs scalars, which could be generated by CP violation in the Higgs sector, will be transformed into a baryon asymmetry by the sphalerons, without the need of B-L violation. This novel mechanism of baryogenesis through (split) Higgsogenesis is exemplified with simple scenarios based on the out-of-equilibrium decay of heavy singlet scalar fields into the Higgs doublets.

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Higgs boson
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Higgs boson: Call to rename particle to acknowledge other scientists

One of the scientists who helped develop the theory of the Higgs boson says the particle should be renamed.
Carl Hagen believes the name should acknowledge the work of others - not just UK physicist Peter Higgs.
The long-running debate has been rekindled following speculation that this year's Nobel Prize for Physics will be awarded for the Higgs theory.
The detection of a particle thought to be the Higgs was announced at the Large Hadron Collider in June last year.

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Have Scientists Found Two Different Higgs Bosons?

A month ago scientists at the Large Hadron Collider released the latest Higgs boson results. And although the data held few obvious surprises, most intriguing were the results that scientists didn't share.
The original Higgs data from back in July had shown that the Higgs seemed to be decaying into two photons more often than it should - an enticing though faint hint of something new, some sort of physics beyond our understanding. In November, scientists at the Atlas and LHC experiments updated everything except the two-photon data. This week we learned why.

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Title: Observing Higgs boson production through its decay into gamma-rays: A messenger for Dark Matter candidates
Authors: Nicolas Bernal, Celine Boehm, Sergio Palomares-Ruiz, Joseph Silk, Takashi Toma

In this Letter, we study the gamma-ray signatures subsequent to the production of a Higgs boson in space by dark matter annihilations. We investigate the cases where the Higgs boson is produced at rest or slightly boosted and show that such configurations can produce characteristic bumps in the gamma-ray data. These results are relevant in the case of the Standard Model-like Higgs boson provided that the dark matter mass is about 63 GeV, 109 GeV or 126 GeV, but can be generalised to any other Higgs boson masses. Here, we point out that it may be worth looking for a 63 GeV line since it could be the signature of the decay of a Standard Model-like Higgs boson produced in space, as in the case of a di-Higgs final state if m_DM ~ 126 GeV. We show that one can set generic constraints on the Higgs boson production rates using its decay properties. In particular, using the Fermi-LAT data from the galactic center, we find that the dark matter annihilation cross section into gamma + a Standard Model-like Higgs boson produced at rest or near rest cannot exceed <sigma v> ~ a few 10^-25 cm/s or <sigma v> ~ a few 10^-27 cm/s respectively, providing us with information on the Higgs coupling to the dark matter particle. We conclude that Higgs bosons can indeed be used as messengers to explore the dark matter mass range.

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Title: A 125.5 GeV Higgs Boson in F-SU(5): Imminently Observable Proton Decay, A 130 GeV Gamma-ray Line, and SUSY Multijets & Light Stops at the LHC8
Authors: Tianjun Li, James A. Maxin, Dimitri V. Nanopoulos, Joel W. Walker

We establish that the light Higgs boson mass in the context of the No-Scale Flipped SU(5) GUT with TeV scale vector-like matter multiplets (flippons) is consistent with m_h = 125.50.5 GeV in the region of the best supersymmetry (SUSY) spectrum fit to low statistics data excesses observed by ATLAS in multijet and light stop 5/fb SUSY searches at the LHC7. Simultaneous satisfaction of these disparate goals is achieved by employing a minor decrease in the SU(5) partial unification scale M_{32} to lower the flippon mass, inducing a larger Higgs boson mass shift from the flippon loops. The reduction in M_{32}, which is facilitated by a phenomenologically favourable reduction of the low-energy strong coupling constant, moreover suggests an imminently observable (e|mu)^+ pi^0 proton decay with a central value time scale of 1.7x10^34 years. At the same point in the model space, we find a lightest neutralino mass of m_{\chi} = 145 GeV, which is suitable for the production of 130 GeV monochromatic gamma-rays through annihilations yielding associated Z-bosons; a signal with this energy signature has been identified within observations of the galactic center by the FERMI-LAT Space Telescope. In conjunction with direct correlations to the fate of the ATLAS multijet and light stop production channels presently being tested at the LHC8, we suggest that the reality of a 125.5 GeV Higgs boson affords a particularly rich company of specific and imminently testable associated observables.

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Title: Higgs Physics and Supersymmetry
Authors: Pran Nath

A brief overview of Higgs physics and of supersymmetry is given. The central theme of the overview is to explore the implications of the recent discovery of a Higgs like particle regarding the prospects for the discovery of supersymmetry assuming that it is indeed the spin 0 CP even boson that enters in the spontaneous breaking of the electroweak symmetry. The high mass of the Higgs like boson at \sim 125 GeV points to the weak scale of supersymmetry that enters in the loop correction to the Higgs boson mass, to be relatively high, i.e., in the TeV region. However, since more than one independent mass scales enter in softly broken supersymmetry, the allowed parameter space of supersymmetric models can allow a small Higgs mixing parameter \mu and light gaugino masses consistent with a \sim 125 GeV Higgs boson mass. Additionally some light third generation sfermions, i.e., the stop and the stau are also permissible. Profile likelihood analysis of a class of SUGRA models indicates that m_A> 300 GeV which implies one is in the decoupling phase and the Higgs couplings are close to the standard model in this limit. Thus a sensitive measurement of the Higgs couplings with fermions and with the vector bosons is needed to detect beyond the standard model effects. Other topics discussed include dark matter, proton stability, and the Stueckelberg extended models as probes of new physics. A brief discussion of the way forward in the post Higgs discovery era is given.

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CERN News: The Higgs or not the Higgs?

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