scholarly journals Threshold effects in SO(10) models with one intermediate breaking scale

2020 ◽  
Vol 80 (9) ◽  
Author(s):  
Davide Meloni ◽  
Tommy Ohlsson ◽  
Marcus Pernow
Keyword(s):  
Standard Model ◽  
Symmetry Breaking ◽  
Particle Physics ◽  
Gauge Coupling ◽  
Grand Unification ◽  
Threshold Effects ◽  
The Standard Model ◽  
Proton Lifetime ◽  
Supersymmetric Theories ◽  
Breaking Scale

AbstractDespite the successes of the Standard Model of particle physics, it is known to suffer from a number of deficiencies. Several of these can be addressed within non-supersymmetric theories of grand unification based on $$\text {SO}(10)$$ SO ( 10 ) . However, achieving gauge coupling unification in such theories is known to require additional physics below the unification scale, such as symmetry breaking in multiple steps. Many such models are disfavored due to bounds on the proton lifetime. Corrections arising from threshold effects can, however, modify these conclusions. We analyze all seven relevant breaking chains with one intermediate symmetry breaking scale, assuming the “survival hypothesis” for the scalar masses. Two are allowed by proton lifetime and two are disfavored by a failure to unify the gauge couplings. The remaining three unify at a too low scale, but can be salvaged by various amounts of threshold corrections. We parametrize this and thereby rank the models by the size of the threshold corrections required to save them.

scholarly journals Chiral anomaly in SU(2)R-axion inflation and the new prediction for particle cosmology

2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
Azadeh Maleknejad
Keyword(s):  
Standard Model ◽  
Symmetry Breaking ◽  
Particle Physics ◽  
Cosmological Parameters ◽  
Chiral Anomaly ◽  
Dark Matter Candidate ◽  
Neutrino Sector ◽  
Matter Creation ◽  
The Standard Model ◽  
Non Gaussian

Abstract Upon embedding the axion-inflation in the minimal left-right symmetric gauge extension of the SM with gauge group SU(2)L × SU(2)R × U(1)B−L, [1] proposed a new particle physics model for inflation. In this work, we present a more detailed analysis. As a compelling consequence, this setup provides a new mechanism for simultaneous baryogenesis and right-handed neutrino creation by the chiral anomaly of WR in inflation. The lightest right-handed neutrino is the dark matter candidate. This setup has two unknown fundamental scales, i.e., the scale of inflation and left-right symmetry breaking SU(2)R × U(1)B−L→ U(1)Y. Sufficient matter creation demands the left-right symmetry breaking scale happens shortly after the end of inflation. Interestingly, it prefers left-right symmetry breaking scales above 1010 GeV, which is in the range suggested by the non-supersymmetric SO(10) Grand Unified Theory with an intermediate left-right symmetry scale. Although WR gauge field generates equal amounts of right-handed baryons and leptons in inflation, i.e. B − L = 0, in the Standard Model sub-sector B − LSM ≠ 0. A key aspect of this setup is that SU(2)R sphalerons are never in equilibrium, and the primordial B − LSM is conserved by the Standard Model interactions. This setup yields a deep connection between CP violation in physics of inflation and matter creation (visible and dark); hence it can naturally explain the observed coincidences among cosmological parameters, i.e., ηB ≃ 0.3Pζ and ΩDM ≃ 5ΩB. The new mechanism does not rely on the largeness of the unconstrained CP-violating phases in the neutrino sector nor fine-tuned masses for the heaviest right-handed neutrinos. The SU(2)R-axion inflation comes with a cosmological smoking gun; chiral, non-Gaussian, and blue-tilted gravitational wave background, which can be probed by future CMB missions and laser interferometer detectors.

scholarly journals HIGGS MASS FROM A CASIMIR ENERGY INDUCED COSMOLOGICAL CONSTANT IN THE STANDARD MODEL

2004 ◽  
Vol 19 (13n16) ◽  
pp. 1195-1201
Author(s):  
XIAO-GANG HE
Keyword(s):  
Standard Model ◽  
Symmetry Breaking ◽  
Cosmological Constant ◽  
Spontaneous Symmetry Breaking ◽  
Particle Physics ◽  
Higgs Mass ◽  
Vacuum Energy ◽  
Casimir Energy ◽  
Renormalization Scale ◽  
The Standard Model

Casimir vacuum energy is divergent. It needs to be regularized. The regularization introduces a renormalization scale which may lead to a scale dependent cosmological constant. We show that the requirement of physical cosmological constant is renormalization scale independent provides important constraints on possible particle contents and their masses in particle physics models. In the Standard Model of strong and electroweak interactions, besides the Casimir vacuum energy there is also vacuum energy induced from spontaneous symmetry breaking. The requirement that the total vacuum energy to be scale independent dictates the Higgs mass to be [Formula: see text] where the summation is over fermions and Ni equals to 3 and 1 for quarks and leptons, respectively. The Higgs mass is predicted to be approximately 382 GeV.

scholarly journals An approach to Grand Unification

2021 ◽  
Vol 2081 (1) ◽  
pp. 012010
Author(s):  
Peter Rowlands
Keyword(s):  
Standard Model ◽  
Particle Physics ◽  
Grand Unification ◽  
Planck Mass ◽  
The Standard Model

Abstract Around the time of the completion of the Standard Model of particle physics in the 1970s, schemes were put forward for unifying the three gauge interactions (electric, strong and weak) using the renormalization equations at an energy approaching the Planck mass. Though these looked promising, the exact unification never materialised, and doubts have been raised about whether this Grand Unification can be achieved. It may be possible, however, to create Grand Unification at the Planck mass if we start with a radical examination of the nature of the colour model of quarks.

scholarly journals Current Issues in the Phenomenology of Particle Physics

1997 ◽  
Vol 12 (31) ◽  
pp. 5531-5554 ◽  
Author(s):  
John Ellis
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Present Status ◽  
Particle Physics ◽  
Neutrino Oscillations ◽  
Experimental Tests ◽  
Grand Unification ◽  
The Standard Model

The present status of the Standard Model and its experimental tests are reviewed, including indications on the likely mass of the Higgs boson. Also discussed are the motivations for supersymmetry and grand unification, searches for sparticles at LEP, neutrino oscillations, and the prospects for physics at the LHC.

scholarly journals SMART U(1)$$_X$$: standard model with axion, right handed neutrinos, two Higgs doublets and U(1)$$_X$$ gauge symmetry

2020 ◽  
Vol 80 (11) ◽  
Author(s):  
Nobuchika Okada ◽  
Digesh Raut ◽  
Qaisar Shafi
Keyword(s):  
Dark Matter ◽  
Gauge Symmetry ◽  
Domain Wall ◽  
Standard Model ◽  
Particle Physics ◽  
Inflection Point ◽  
Baryon Asymmetry ◽  
Grand Unification ◽  
The Standard Model ◽  
The Universe

AbstractTo address five fundamental shortcomings of the Standard Model (SM) of particle physics and cosmology, we propose a phenomenologically viable framework based on a $$U(1)_X \times U(1)_{PQ}$$ U ( 1 ) X × U ( 1 ) PQ extension of the SM, that we call “SMART U(1)$$_X$$ X ”. The $$U(1)_X$$ U ( 1 ) X gauge symmetry is a well-known generalization of the $$U(1)_{B-L}$$ U ( 1 ) B - L symmetry and $$U(1)_{PQ}$$ U ( 1 ) PQ is the global Peccei–Quinn (PQ) symmetry. Three right handed neutrinos are added to cancel $$U(1)_X$$ U ( 1 ) X related anomalies, and they play a crucial role in understanding the observed neutrino oscillations and explaining the observed baryon asymmetry in the universe via leptogenesis. Implementation of PQ symmetry helps resolve the strong CP problem and also provides axion as a compelling dark matter (DM) candidate. The $$U(1)_X$$ U ( 1 ) X gauge symmetry enables us to implement the inflection-point inflation scenario with $$H_{inf} \lesssim 2 \times 10^{7}$$ H inf ≲ 2 × 10 7  GeV, where $$H_{inf}$$ H inf is the value of Hubble parameter during inflation. This is crucial to overcome a potential axion domain wall problem as well as the axion isocurvature problem. The SMART U(1)$$_X$$ X framework can be successfully implemented in the presence of SU(5) grand unification, as we briefly show.

scholarly journals RENORMALIZATION GROUP AND GRAND UNIFICATION WITH 331 MODELS

2007 ◽  
Vol 22 (10) ◽  
pp. 1849-1874 ◽  
Author(s):  
RODOLFO A. DIAZ ◽  
D. GALLEGO ◽  
R. MARTINEZ
Keyword(s):  
Renormalization Group ◽  
Symmetry Breaking ◽  
Group Analysis ◽  
Coupling Constants ◽  
Grand Unification ◽  
Renormalization Group Analysis ◽  
Running Coupling ◽  
The Standard Model ◽  
Split Supersymmetry ◽  
Breaking Scale

By making a renormalization group analysis we explore the possibility of having a 331 model as the only intermediate gauge group between the standard model and the scale of unification of the three coupling constants. We shall assume that necessarily there is no group of grand unification at the scale of convergence of the couplings. With this scenario, different 331 models and their corresponding supersymmetric versions are considered, and we find the versions that allow the symmetry breaking described above. Besides, the allowed interval for the 331 symmetry breaking scale, and the behavior of the running coupling constants are obtained. It is worth saying that some of the supersymmetric scenarios could be natural frameworks for split supersymmetry. Finally, we look for possible 331 models with a simple group at the grand unification scale that could fit the symmetry breaking scheme described above.

scholarly journals Probing Anomalous Quartic Interactions at the LHC with proton tagging

2018 ◽  
Vol 172 ◽  
pp. 06002
Author(s):  
Cristian Baldenegro
Keyword(s):  
Large Hadron Collider ◽  
Standard Model ◽  
Particle Physics ◽  
Hadron Collider ◽  
Center Of Mass ◽  
Gauge Coupling ◽  
New Physics ◽  
Interaction Point ◽  
The Standard Model ◽  
Discovery Potential

One of the main goals of the Large Hadron Collider is to find signatures of physics Beyond the Standard Model of particle physics. One way to do this is by studying with high precision the interactions of the Standard Model. In this talk, we address the discovery potential of New Physics in the exclusive channel pp → p X p which relies on the general purpose detectors at the Large Hadron Collider and their respective forward proton detector stations, located at about ~ 210 m w.r.t. the interaction point. These reactions are highly sensitive to quartic electroweak gauge interactions. As a proof of concept, we discuss the exclusive diphoton production at high diphoton invariant mass. We quote sensitivities on the anomalous γγγγ coupling for an integrated luminosity of 300 fb1 at the center-of-mass energy of 14 TeV.We also discuss the discovery potential of 3γZ anomalous quartic gauge coupling by measuring the pp → p(γγ → Zγ)p reaction.

scholarly journals SU(8) family unification with boson–fermion balance

2014 ◽  
Vol 29 (22) ◽  
pp. 1450130 ◽  
Author(s):  
Stephen L. Adler
Keyword(s):  
Perturbation Theory ◽  
Standard Model ◽  
Symmetry Breaking ◽  
Gauge Field ◽  
Gauge Coupling ◽  
Dynamical Symmetry ◽  
Gauge Fields ◽  
Yukawa Couplings ◽  
Gauge Symmetries ◽  
The Standard Model

We formulate an SU(8) family unification model motivated by requiring that the theory should incorporate the graviton, gravitinos, and the fermions and gauge fields of the standard model, with boson–fermion balance. Gauge field SU(8) anomalies cancel between the gravitinos and spin ½ fermions. The 56 of scalars breaks SU(8) to SU(3) family × SU(5) × U(1)/Z5, with the fermion representation content needed for "flipped" SU(5) with three families, and with residual scalars in the 10 and [Formula: see text] representations that break flipped SU(5) to the standard model. Dynamical symmetry breaking can account for the generation of 5 representation scalars needed to break the electroweak group. Yukawa couplings of the 56 scalars to the fermions are forbidden by chiral and gauge symmetries, so in the first stage of SU(8) breaking fermions remain massless. In the limit of vanishing gauge coupling, there are N = 1 and N = 8 supersymmetries relating the scalars to the fermions, which restrict the form of scalar self-couplings and should improve the convergence of perturbation theory, if not making the theory finite and "calculable." In an Appendix we give an analysis of symmetry breaking by a Higgs component, such as the (1, 1)(-15) of the SU(8) 56 under SU(8) ⊃ SU(3) × SU(5) × U(1), which has nonzero U(1) generator.

Indirect measurements in micro-space with the EM

1995 ◽  
Vol 53 ◽  
pp. 598-599
Author(s):  
Sterling P. Newberry
Keyword(s):  
Electron Microscope ◽  
Standard Model ◽  
Particle Physics ◽  
Information Storage ◽  
Storage Space ◽  
Indirect Measurements ◽  
Storage And Retrieval ◽  
Adequate Information ◽  
Compelling Reason ◽  
The Standard Model

At the 1958 meeting of our society, then known as EMSA, the author introduced the concept of microspace and suggested its use to provide adequate information storage space and the use of electron microscope techniques to provide storage and retrieval access. At this current meeting of MSA, he wishes to suggest an additional use of the power of the electron microscope.The author has been contemplating this new use for some time and would have suggested it in the EMSA fiftieth year commemorative volume, but for page limitations. There is compelling reason to put forth this suggestion today because problems have arisen in the “Standard Model” of particle physics and funds are being greatly reduced just as we need higher energy machines to resolve these problems. Therefore, any techniques which complement or augment what we can accomplish during this austerity period with the machines at hand is worth exploring.

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