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DOE OSTI2020

Higgs troika for baryon asymmetry

To explain the baryon asymmetry of the Universe, we extend the Standard Model (SM) with two additional Higgs doublets with small vacuum expectation values. The additional Higgs fields interact with SM fermions through complex Yukawa couplings, leading to new sources of $CP$ violation. We propose a simple flavor model with $\mathcal{O}$(1) or less Yukawa couplings for quarks and charged leptons, consistent with current flavor constraints. To generate neutrino masses and the baryon asymmetry, right-handed neutrinos in the ~ 0.1 - 10 TeV range couple to the "Higgs Troika." The new Higgs doublet masses are at or above the TeV scale, allowing for asymmetric decays into SM lepton doublets and right-handed neutrinos. The asymmetry in lepton doublets is then processed into a baryon asymmetry, similar to leptogenesis. Since the masses of the new fields could be near the TeV scale, there is potentially a rich high energy collider phenomenology, including observable deviations in the 125 GeV Higgs decay into muons and taus, as well as detectable low energy signals such as the electron EDM or $µ → eγ$. Hence, this is in principle a testable model for generation of baryon asymmetry.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Heavy Higgs signal–background interference in $gg\rightarrow VV$ in the Standard Model plus real singlet

For the Standard Model extended with a real scalar singlet field, the modification of the heavy Higgs signal due to interference with the continuum background and the off-shell light Higgs contribution is studied for gg → ZZ, WW → 4 lepton processes at the Large Hadron Collider. Interference effects can range from O(10%) to O(1) effects for integrated cross sections. Despite a strong cancellation between the heavy Higgs–continuum and the heavy Higgs–light Higgs interference, the full interference is clearly non-negligible and modifies the heavy Higgs line shape. A |M VV –M h2 | < Γ h2 cut mitigates interference effects to O(10%) or less. A public program that allows one to simulate the full interference is presented.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

The Higgs and Supersymmetry at Run II of the LHC

Prof. David Shih was supported by DOE grant DE-SC0013678 from April 2015 to April 2016. His research during this year focused on the phenomenology of super-symmetry (SUSY) and maximizing its future discovery potential at Run II of the LHC. SUSY is one of the most well-motivated frameworks for physics beyond the Standard Model. It solves the "naturalness" or "hierarchy" problem by stabilizing the Higgs mass against otherwise uncontrolled quantum corrections, predicts "grand unification" of the fundamental forces, and provides many potential candidates for dark matter. However, after decades of null results from direct and indirect searches, the viable parameter space for SUSY is increasingly constrained. Also, the discovery of a Standard Model-like Higgs with a mass at 125 GeV places a stringent constraint on SUSY models. In the work supported on this grant, Shih has worked on four different projects motivated by these issues. He has built natural SUSY models that explain the Higgs mass and provide viable dark matter; he has studied the parameter space of "gauge mediated supersymmetry breaking" (GMSB) that satisfies the Higgs mass constraint; he has developed new tools for the precision calculation of flavor and CP observables in general SUSY models; and he has studied new techniques for discovery of supersymmetric partners of the top quark.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Higgs mass, superconnections, and the TeV-scale left-right symmetric model

We discuss the physical implications of formulating the Standard Model (SM) in terms of the superconnection formalism involving the superalgebra su(2/1). In particular, we discuss the prediction of the Higgs mass according to the formalism and point out that it is ~170 GeV, in clear disagreement with experiment. To remedy this problem, we extend the formalism to the superalgebra su(2/2), which extends the SM to the left-right symmetric model (LRSM) and accommodates a ~126 GeV Higgs. Both the SM in the su(2/1) case and the LRSM in the su(2/2) case are argued to emerge at ~4 TeV from an underlying theory in which the spacetime geometry is modified by the addition of a discrete extra dimension. The formulation of the exterior derivative in this model space suggests a deep connection between the modified geometry, which can be described in the language of non-commutative geometry (NCG), and the spontaneous breaking of the gauge symmetries. The implication is that spontaneous symmetry breaking could actually be geometric/quantum gravitational in nature. The non-decoupling phenomenon seen in the Higgs sector can then be reinterpreted in a new light as due to the mixing of low energy (SM) physics and high energy physics associated with quantum gravity, such as string theory. In conclusion, the phenomenology of a TeV scale LRSM is also discussed, and we argue that some exciting discoveries may await us at the LHC, and other near-future experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Anatomizing Exotic Production of the Higgs Boson

We discuss exotic production modes of the Higgs boson and how their phenomenology can be probed in current Higgs analyses. We highlight the importance of differential distributions in disentangling standard production mechanisms from exotic modes. We present two model benchmarks for exotic Higgs production arising from chargino-neutralino production and study their impact on the current Higgs dataset. As a corollary, we emphasize that current Higgs coupling fits do not fully explore the space of new physics deviations possible in Higgs data.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Naturalness confronts nature: searches for supersymmetry with the CMS detector in pp collisions at √s = 8 and $13$ TeV

In this thesis, we present two inclusive searches for supersymmetric particles at √s = 8 and 13 TeV using the razor variables and guided by the principle of naturalness. We build a framework to explore the natural supersymmetry parameter space of gluino and top squark masses and branching ratios, which is a unique attempt to cover this parameter space in a more complete way than ever before using LHC data. With this approach, the production of top squarks and gluinos are excluded below ~ 700 GeV and ~ 1.6 TeV, respectively, independent of the branching ratios, constituting one of the tightest constraints on natural supersymmetry from the LHC. Motivated by the need to mitigate the effects of multiple interactions per bunch crossing (pileup), an essential feature of present and future hadron colliders, in this thesis we also study the precision timing capabilities of a LYSO-based sampling calorimeter, and achieve a time resolution of ~ 30 ps in electron test beam measurements. The achieved resolution corresponds to the precision needed to significantly reduce the inclusion of pileup particles in the reconstruction of the event of interest. This study is foundational in building an R&D program on precision timing for the high-luminosity LHC and other future hadron colliders. We also propose alternative simplified models to study Higgs-plus-jets events at the LHC, and reinterpret an excess observed at 8 TeV in the context of these models. Finally, we discuss a search for narrow resonances in the dijet mass spectrum at 13 TeV using the data-scouting technique at CMS, which records a smaller event format to increase the maximum recordable rate. For the benchmark models with a vector or axial-vector mediator that couples to quarks and dark matter particles, the dijet search excludes mediator masses from 0.5 TeV up to ~ 2.7 TeV largely independent of the dark matter particle mass, which constitutes a larger exclusion than traditional mono-X searches at the LHC. In the plane of the dark matter-nucleon interaction cross section versus dark matter mass, the dijet search is also more sensitive than direct detection experiments for spin-dependent cross sections.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Generating non-topological solitons via thermal corrections: Higgs balls

Scalar fields which carry charge can generally form non-topological solitons (Q-balls), if the energy in the extended configuration is less than the energy of an equivalent number of free quanta. For global Q-balls, such solitons exist whenever the potential grows slower than quadratically. We show that even in the absence of attractive interactions, finite temperature corrections can generate Q-ball solutions, as the coefficient of cubic corrections is generally negative. As an illustration of this, we consider the possibility of constructing Q-balls using the Higgs field. We first show that the finite temperature corrections would enable the existence of Higgs balls if the Standard Model symmetry was ungauged. We then consider gauged Q-balls, following [1], and demonstrate that Higgs self-interactions mediated by the Standard Model gauge bosons are sufficient to prevent the existence of these states in the actual Standard Model. However, these states can exist in a variety of extensions, as we show explicitly through an example.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

The discrete family symmetries as the possible solution to the flavour problem

In order to explain the fermions’ masses and mixing parameters appearing in the lepton sector of the Standard Model, one proposes the extension of its symmetry. A discrete, non-Abelian subgroup of U(3) is added to the gauge group SU(3){sub C} × SU(2){sub L} × U(1){sub Y}. Apart from that, one assumes the existence of one extra Higgs doublet. This article focuses mainly on the mathematical theorems and computational techniques which brought us to the results.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Search for a multi-Higgs-boson cascade in W + W - b b ¯ events with the ATLAS detector in p p collisions at s = 8 TeV

A search is presented for new particles in an extension to the Standard Model that includes a heavy Higgs boson (H 0 ), an intermediate charged Higgs-boson pair ( H &plusmn; ), and a light Higgs boson (h 0 ). The analysis searches for events involving the production of a single heavy neutral Higgs boson which decays to the charged Higgs boson and a W boson, where the charged Higgs boson subsequently decays into a W boson and the lightest neutral Higgs boson decaying to a bottom-antibottom-quark pair. Such a cascade results in a W -boson pair and a bottom-antibottom-quark pair in the final state. Events with exactly one lepton, missing transverse momentum, and at least four jets are selected from a data sample corresponding to an integrated luminosity of 20.3 fb -1 , collected by the ATLAS detector in proton-proton collisions at $ \sqrt{s}$ = 8 TeV at the LHC. The data are found to be consistent with Standard Model predictions, and 95% confidence-level upper limits are set on the product of cross section and branching ratio. Lastly, these limits range from 0.065 to 43 pb as a function of H 0 and H &plusmn; masses, with m h 0 fixed at 125 GeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Cosmic strings in hidden sectors: 1. Radiation of standard model particles

In hidden sector models with an extra U(1) gauge group, new fields can interact with the Standard Model only through gauge kinetic mixing and the Higgs portal. After the U(1) is spontaneously broken, these interactions couple the resultant cosmic strings to Standard Model particles. We calculate the spectrum of radiation emitted by these ''dark strings'' in the form of Higgs bosons, Z bosons, and Standard Model fermions assuming that string tension is above the TeV scale. We also calculate the scattering cross sections of Standard Model fermions on dark strings due to the Aharonov-Bohm interaction. These radiation and scattering calculations will be applied in a subsequent paper to study the cosmological evolution and observational signatures of dark strings.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Probing light thermal dark matter with a Higgs portal mediator

We systematically study light (<few GeV) dark matter (DM) models that thermalize with visible matter through the Higgs portal and identify the remaining gaps in the viable parameter space. Such models require a comparably light scalar mediator that mixes with the Higgs to avoid DM overproduction and can be classified according to whether this mediator decays (in)visibly. In a representative benchmark model with Dirac fermion DM, we find that, even with conservative assumptions about the DM-mediator coupling and mass ratio, the regime in which the mediator is heavier than the DM is fully ruled out by a combination of collider, rare meson decay, and direct detection limits; future and planned experiments including NA62 can further improve sensitivity to scenarios in which the Higgs portal interaction does not determine the DM abundance. The opposite regime in which the mediator is lighter than the DM and the latter annihilates to pairs of visibly decaying mediators is still viable, but much of the parameter space is covered by rare meson decay, supernova cooling, beam dump, and direct detection constraints. Nearly all of these conclusions apply broadly to the simplest variations (e.g., scalar or asymmetric DM). Future experiments including SHiP, NEWS, and Super-CDMS SNOLAB can greatly improve coverage to this class of models.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Loop suppressed electroweak symmetry breaking and naturally heavy superpartners

In this article, a model is presented in which O ( 10 TeV ) stop masses, typically required by the Higgs boson mass in supersymmetric models, do not originate from soft supersymmetry breaking terms that would drive the Higgs mass squared parameter to large negative values but rather from the mixing with vectorlike partners. Their contribution to the Higgs mass squared parameter is reduced to threshold corrections and, thus, it is one loop suppressed compared to usual scenarios. New fermion and scalar partners of the top quark with O ( 10 TeV ) masses are predicted.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Higgs-mass predictions in the MSSM and beyond

Abstract Predictions for the Higgs masses are a distinctive feature of supersymmetric extensions of the Standard Model, where they play a crucial role in constraining the parameter space. The discovery of a Higgs boson and the remarkably precise measurement of its mass at the LHC have spurred new efforts aimed at improving the accuracy of the theoretical predictions for the Higgs masses in supersymmetric models. The “ Precision SUSY Higgs Mass Calculation Initiative ” (KUTS) was launched in 2014 to provide a forum for discussions between the different groups involved in these efforts. This report aims to present a comprehensive overview of the current status of Higgs-mass calculations in supersymmetric models, to document the many advances that were achieved in recent years and were discussed during the KUTS meetings, and to outline the prospects for future improvements in these calculations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

XXVIIth International Conference on Supersymmetry and Unification of Fundamental Interactions (SUSY 2019) (Final Report)

Supersymmetry (SUSY) is one of most elegant extensions of the Standard Model (SM) and explains the puzzles of the SM by providing a candidate to explain the dark matter content of the universe, allowing scientists to understand the origin of the electroweak scale requiring the top mass to be around 170 GeV and leading to the unification of forces at a grand unified scale. Further the minimal supersymmetric standard model (MSSM) predicts the Higgs boson mass to be less than 135 GeV. The discovery of the Higgs Boson with mass around 125 GeV at the LHC has provided a major support to SUSY ideas. Searches for SUSY are ongoing at the Large Hadron Collider (LHC). Direct and indirect dark matter experiments are searching for a particle dark matter candidate which arises most naturally in SUSY models. Proton decay predicted by SUSY grand unified theories is being searched for at deep underground experiments. In addition, recent advances in neutrino and dark matter physics, observational astrophysics, precision cosmology and the promising new window into the cosmos opened by the direct detection of gravitational waves, have brought new ideas on the potential connections between new fundamental particles and our understanding of their impact on the early universe and its evolution. At present, the major questions include: Is SUSY still the best candidate for models beyond the SM? Do we have any well motivated alternative to SUSY? Have we exhausted all possibilities to search for new physics at high and low energy scales? XXVIIth International Conference on Supersymmetry and Unification of Fundamental Interactions (SUSY 2019), hosted by Texas A&M University – Corpus Christi during May 20-24, 2019, provided a unique venue to discus and understand the status of SUSY, connection between particle physics and cosmology, supersymmetry and its alternative, Higgs sector, neutrino sector, flavor sector, dark matter, electroweak phase transition, astroparticle physics, gravitational waves and string theory. Discussion of results from the LHC, recent neutrino experiments and observations, direct and indirect dark matter detection experiments, detection of gravitational waves, data from particle colliders, as well as measurements of the CMB and Large Scale Structure were an integral part of SUSY 2019. To ensure the younger participants will benefit from the conference the most, the conference was preceded by the 4 day long pre-SUSY summer school for graduate students and postdocs. The invited speakers were leading scientists in the fields of SUSY interest. The school took place on Texas A&M University – Corpus Christi campus during the week prior the SUSY 2019 conference (May 15 – 18, 2019). Since its inception in 1993, SUSY has become one of the most important and widely attended international meetings in high energy physics, devoted to new ideas in fundamental particle physics. SUSY 2019 brought together approximately 250 scientists, theorists, phenomenologists, experimentalists and cosmologists, (including over 60 graduate students and 70 postdocs) representing 22 nations: Australia, Belgium, Canada, Chile, China, Colombia, France, Germany, India, Italy, Japan, Mexico, Peru, Portugal, Romania, South Korea, Spain, Sweden, Switzerland, Taiwan, United Kingdom and United States. SUSY 2019 provided a stimulating venue for the exchange of scientific ideas among experts in dark matter, neutrino physics, particle physics, astrophysics and cosmology. The following scientific topics were delivered during SUSY 2019 in form of 44 plenary talks and over 200 parallel talks: Unification of Forces; Electroweak, Top and Higgs Physics; Precision Calculations and MC tools; BSM in Flavor Physics; Neutrino Masses: Models and Phenomenology; Cosmology and Gravitational Waves; Dark Matter, Astroparticle Physics; Formal Field Theory and Strings; Alternatives to Supersymmetry; Quantum Information: Machine Learning/Big Data. 28 talks were given during the pre-SUSY program related to the following topics: Neutrino Physics; Big Data; Collider Physics & SUSY; String Phenomenology; Cosmology; Dark Matter; SUSY Models and Phenomenology

43 PARTICLE ACCELERATORS↗
DOE OSTI2014

Renormalization of a two-loop neutrino mass model

We analyze the renormalization group structure of a radiative neutrino mass model consisting of a singly charged and a doubly charged scalar fields. Small Majorana neutrino masses are generated by the exchange of these scalars via two-loop diagrams. We derive boundedness conditions for the Higgs potential and show how they can be satisfied to energies up to the Planck scale. Combining boundedness and perturbativity constraints with neutrino oscillation phenomenology, new limits on the masses and couplings of the charged scalars are derived. These in turn lead to lower limits on the branching ratios for certain lepton flavor violating (LFV) processes such as μ→eγ, μ→3e and μ – e conversion in nuclei. Improved LFV measurements could test the model, especially in the case of inverted neutrino mass hierarchy where these are more prominent.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

The International Linear Collider. A Global Project

A large, world-wide community of physicists is working to realise an exceptional physics program of energy-frontier, electron-positron collisions with the International Linear Collider (ILC). This program will begin with a central focus on high-precision and model-independent measurements of the Higgs boson couplings. This method of searching for new physics beyond the Standard Model is orthogonal to and complements the LHC physics program. The ILC at 250 GeV will also search for direct new physics in exotic Higgs decays and in pair-production of weakly interacting particles. Polarised electron and positron beams add unique opportunities to the physics reach. The ILC can be upgraded to higher energy, enabling precision studies of the top quark and measurement of the top Yukawa coupling and the Higgs self-coupling. The key accelerator technology, superconducting radio-frequency cavities, has matured. Optimised collider and detector designs, and associated physics analyses, were presented in the ILC Technical Design Report, signed by 2400 scientists. There is a strong interest in Japan to host this international effort. A detailed review of the many aspects of the project is nearing a conclusion in Japan. Now the Japanese government is preparing for a decision on the next phase of international negotiations, that could lead to a project start within a few years. The potential timeline of the ILC project includes an initial phase of about 4 years to obtain international agreements, complete engineering design and prepare construction, and form the requisite international collaboration, followed by a construction phase of 9 years.

43 PARTICLE ACCELERATORS↗
NASA NTRS1986

The behavior of the Higgs field in the new inflationary universe

Answers are provided to questions about the standard model of the new inflationary universe (NIU) which have raised concerns about the model's validity. A baby toy problem which consists of the study of a single particle moving in one dimension under the influence of a potential with the form of an upside-down harmonic oscillator is studied, showing that the quantum mechanical wave function at large times is accurately described by classical physics. Then, an exactly soluble toy model for the behavior of the Higgs field in the NIU is described which should provide a reasonable approximation to the behavior of the Higgs field in the NIU. The dynamics of the toy model is described, and calculative results are reviewed which, the authors claim, provide strong evidence that the basic features of the standard picture are correct.

Guth, Alan H.↗
DOE OSTI2016

CP violation in heavy MSSM Higgs scenarios

We introduce and explore new heavy Higgs scenarios in the Minimal Supersymmetric Standard Model (MSSM) with explicit CP violation, which have important phenomenological implications that may be testable at the LHC. For soft supersymmetry-breaking scales M S above a few TeV and a charged Higgs boson mass M H + above a few hundred GeV, new physics effects including those from explicit CP violation decouple from the light Higgs boson sector. However, such effects can significantly alter the phenomenology of the heavy Higgs bosons while still being consistent with constraints from low-energy observables, for instance electric dipole moments. To consider scenarios with a charged Higgs boson much heavier than the Standard Model (SM) particles but much lighter than the supersymmetric particles, we revisit previous calculations of the MSSM Higgs sector. We compute the Higgs boson masses in the presence of CP violating phases, implementing improved matching and renormalization-group (RG) effects, as well as two-loop RG effects from the effective two-Higgs Doublet Model (2HDM) scale M H ± to the scale M S . Here, we illustrate the possibility of non-decoupling CP-violating effects in the heavy Higgs sector using new benchmark scenarios named.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗