Higgs Mass Research Articles

QCD corrections to in Type-I THDM at electron positron colliders * * Supported in part by the National Natural Science Foundation of China (11775211, 11535002) and the CAS Center for Excellence in Particle Physics (CCEPP)

We investigate in detail the charged Higgs production associated with a W boson at electron-positron colliders within the framework of the Type-I two-Higgs-doublet model (THDM). We calculate the integrated cross section at the LO and analyze the dependence of the cross section on the THDM parameters and the colliding energy in a benchmark scenario of the input parameters of the Higgs sector. The numerical results show that the integrated cross section is sensitive to the charged Higgs mass, especially in the vicinity of at a collider, and decreases consistently with the increase of in the low region. The peak in the colliding energy distribution of the cross section arises from the resonance of the loop integrals, and it moves towards the low colliding energy with the increase of . We also study the two-loop NLO QCD corrections to both the integrated cross section and the angular distribution of the charged Higgs boson and find that the QCD relative correction is also sensitive to the charged Higgs mass and strongly depends on the final-state phase space. For , the QCD relative correction at a collider varies in the range of [-10%, 11%] as increases from 150 to 400 GeV.

The 7% rule: A maximum entropy prediction on new decays of the Higgs boson

The entropy of the Higgs boson decay probabilities distribution in the Standard Model (SM) is maximized for a Higgs mass value that is less than one standard deviation away from the current experimental measurement. This successful estimate of the Higgs mass encourages us to propose tests of the Maximum Entropy Principle (MEP) as a tool for theoretical inferences in other instances of Higgs physics. In this letter, we show that, irrespective of the extension of the SM predicting a new Higgs boson decay channel, its branching ratio can be inferred to be around 7% in such a way that the new entropy of decays still exhibits a maximum at the experimental Higgs mass. This 7% rule can be tested whenever a new Higgs decay channel is found. In order to illustrate the MEP predictions, we apply the MEP inference to Higgs portal models, Higgs-axion interactions, lepton flavor violating decays of the Higgs boson, and a dark gauge boson model.

Natural supersymmetric Twin Higgs

A new class of supersymmetric Twin Higgs (TH) models where new gauge symmetry is responsible for the TH mechanism is reviewed. In this class of models the Higgs mass is naturally in agreement with the LHC measurement while the electroweak symmetry breaking is realised without excessive tuning despite of strong lower bounds on masses of supersymmetric particles set by the LHC. Assuming particular non-abelian structure of the new gauge symmetry the model remains perturbative up to the energy scale of gravity, in contrast to all previously proposed UV completions of the TH model.

Vacuum Structure in the Standard Model with a Complex Scalar Singlet

We analyze the vacuum structure in an extension of the Standard Model with a complex singlet scalar field. Beyond the Standard Model, this model shows a much richer vacuum structure and a variety of interesting mass spectra. In this paper, we first show that the Higgs mass matrix can be simplified using the proper basis, and it can comprehensively reflect the change in the tadpole conditions due to the soft symmetry-breaking terms. Thus, this framework makes it easy to obtain a mass matrix through the corresponding tadpole conditions when considering new symmetry such as $\mathbb{Z}^\prime_2$. Finally, we introduce the Higgs potential for the trilinear and quartic Higgs self couplings, and summarize the vacuum structure taking into account all possible cases with a corresponding set of inputs and miscellaneous relations.

Natural Higgs inflation, gauge coupling unification, and neutrino masses

We present a class of nonsupersymmetric models in which the so-called critical Higgs inflation [Formula: see text] can be naturally realized without using specific values for Higgs and top quark masses. In these scenarios, the Standard Model (SM) vacuum stability problem, gauge coupling unification, neutrino mass generation and Higgs inflation mechanism are linked to each other. We adopt in our models Type I seesaw mechanism for neutrino masses. An appropriate choice of the Type I seesaw scale allows us to have an arbitrarily small but positive value of SM Higgs quartic coupling around the inflation scale. We present a few benchmark points where we show that the scalar spectral indices are around 0.9626 and 0.9685 for the number of [Formula: see text]-folding [Formula: see text] and [Formula: see text], respectively. The tensor-to-scalar ratios are of the order of [Formula: see text]. The running of the scalar spectral index is negative and is of the order of [Formula: see text].

Single top partner production in the tZ channel at eγ collision in the littlest Higgs model with T-parity

Introducing the top partner is a common way to cancel the largest quadratically divergent contribution to the Higgs mass induced by the top quark. In this work, we study single top partner production in the tZ channel at eγ collision in the littlest Higgs model with T-parity (LHT). Since it is well known that polarized beams can enhance the cross section, we analyze the signal via polarized electron beams, and photon beams. we have selected two decay modes for comparison, based on the leptonic or the hadronic decays of the W and Z from the top partner. We then construct a detailed detector simulation, and choose a set of cuts to enhance signal significance. For mode A(B), the capacity for exclusion in this process at = 3 TeV is comparable to the current experimental limits with L = 1000 (500) fb−1. If the integrated luminosity can be increased to 3000 fb−1, the top partner mass can be excluded up to 1350 (1440) GeV at 2σ level. We also considered the initial state radiation effect, and find that this effect reduces the excluding ability of the eγ collision on the the top partner mass by approximately 10 GeV. Moreover, the ability to exclude the LHT parameter space at eγ collision complements the existing research.

Cornering Spontaneous CP Violation with Charged-Higgs-Boson Searches

Decades of precision measurements have firmly established the Kobayashi-Maskawa phase as the dominant source of the charge-parity (CP) violation observed in weak quark decays. However, it is still unclear whether CP violation is explicitly encoded in complex Yukawa matrices or instead stems from spontaneous symmetry breaking with underlying CP-conserving Yukawa and Higgs sectors. Here we study the latter possibility for the case of a generic two-Higgs-doublet model. We find that theoretical constraints limit the ratio t_{β} of the vacuum expectation values (vevs) to the range 0.22≤t_{β}≤4.5 and imply the upper bounds M_{H^{±}}≤435 GeV, M_{H_{2}^{0}}≤485 GeV and M_{H_{3}^{0}}≤545 GeV for the charged and extra neutral Higgs masses. We derive lower bounds on charged-Higgs couplings to bottom quarks which provide a strong motivation to study the nonstandard production and decay signatures pp→qbH^{±}(→q^{'}b) with all flavors q,q^{'}=u, c, t in the search for the charged Higgs boson. We further present a few benchmark scenarios with interesting discovery potential in collider analyses.

Confinement in the two-dimensional yukawa theory with the Higgs mass generation mechanism

We considered the two-dimensional theoretical field model of interaction of scalar and fermion fields with the Higgs potential. Contribution of instanton effects to total fermion propagator is calculated. Mass correction to the propagator in the presence of an instanton field is determined. The obtained results can be interpreted as confinement.

Improved MSSM Higgs mass calculation using the 3-loop FlexibleEFTHiggs approach including xt-resummation

We present an improved calculation of the light CP-even Higgs boson pole mass in the MSSM based on the FlexibleEFTHiggs hybrid method. The calculation resums large logarithms to all orders and includes power-suppressed terms at fixed order. It uses state-of-the-art 2- and 3-loop matching of the quartic Higgs coupling and renormalization group running up to 4-loop, resulting in a resummation of large logarithmic corrections up to N3LL level. A conceptually novel ingredient is the expansion of the matching conditions in terms of high-scale MSSM parameters instead of SM parameters. In this way leading QCD-enhanced terms in the stop-mixing parameter are effectively resummed, leading to an improved numerical convergence of the perturbative expansion. Furthermore, the avoidance of double counting of loop corrections is more transparent than in other approaches and more independent of the high-scale model. We present numerical results and a detailed discussion of theoretical uncertainties for standard benchmark scenarios.

Probing the relaxed relaxion at the luminosity and precision frontiers

Cosmological relaxation of the electroweak scale is an attractive scenario addressing the gauge hierarchy problem. Its main actor, the relaxion, is a light spin-zero field which dynamically relaxes the Higgs mass with respect to its natural large value. We show that the relaxion is generically stabilized at a special position in the field space, which leads to suppression of its mass and potentially unnatural values for the model’s effective low-energy couplings. In particular, we find that the relaxion mixing with the Higgs can be several orders of magnitude above its naive naturalness bound. Low energy observers may thus find the relaxion theory being fine-tuned although the relaxion scenario itself is constructed in a technically natural way. More generally, we identify the lower and upper bounds on the mixing angle. We examine the experimental implications of the above observations at the luminosity and precision frontiers. A particular attention is given to the impressive ability of future nuclear clocks to search for rapidly oscillating scalar ultra-light dark matter, where the future projected sensitivity is presented.

Prediction of the Higgs and Top Quark Masses by Discrete Dimensions Revisited

A new metric structure of the discretized Kaluza-Klein theory can give us new knowledge about extra-dimension . It can provide the new predictions of the top quark and Higgs mass that studied by Viet [15 , 16] in another model. Compare the results of two approaches we can see that the new model is more agreement with experimental data.

Precision unification and Higgsino dark matter in GUT scale supersymmetry

Even if the concerns related to the naturalness of the electroweak scale are repressed, the Higgs mass and stability of the electroweak vacuum do not allow arbitrarily large supersymmetry breaking scale, $M_S$, in the minimal models with split or high-scale supersymmetry. We show that $M_S$ can be raised to the GUT scale if the theory below $M_S$ contains a Higgs doublet, a pair of TeV scale Higgsino and widely separated gauginos in addition to the Standard Model particles. The presence of wino and gluino below ${\cal O}(100)$ TeV leads to precision unification of the gauge couplings consistent with the current limits on the proton lifetime. Wino, at this scale, renders the Higgsino as pseudo-Dirac dark matter which in turn evades the existing constraints from the direct detection experiments. Bino mass scale is required to be $\gtrsim 10^{10}$ GeV to get the observed Higgs mass respecting the current limit on the charged Higgs mass. The framework predicts, $1 \lesssim \tan\beta \lesssim 2.2$ and $\tau[p\to e^+\, \pi^0] < 7 \times 10^{35}$ years, almost independent of values of the other parameters. The electroweak vacuum is found to be stable or metastable. The underlying framework provides an example of a viable sub-GUT scale theory of supersymmetric grand unified theory in which supersymmetry and unified gauge symmetry are broken at a common scale.

A novel scenario in the semi-constrained NMSSM

In this work, we develop a novel efficient scan method, combining the Heuristically Search (HS) and the Generative Adversarial Network (GAN), where the HS can shift marginal samples to perfect samples, and the GAN can generate a huge amount of recommended samples from noise in a short time. With this efficient method, we find a new scenario in the semi-constrained Next-to Minimal Supersymmetric Standard Model (scNMSSM), or NMSSM with non-universal Higgs masses. In this scenario, (i) Both muon g-2 and right relic density can be satisfied, along with the high mass bound of gluino, etc. As far as we know, that had not been realized in the scNMSSM before this work. (ii) With the right relic density, the lightest neutralinos are singlino-dominated, and can be as light as 0-12 GeV. (iii) The future direct detections XENONnT and LUX-ZEPLIN (LZ-7 2T) can give strong constraints to this scenario. (iv) The current indirect constraints to Higgs invisible decay {h}_2to {tilde{chi}}_1^0{tilde{chi}}_1^0 are weak, but the direct detection of Higgs invisible decay at the future HL-LHC may cover half of the samples, and that of the CEPC may cover most. (v) The branching ratio of Higgs exotic decay h2→ h1h1, a1a1 can be over 20 percent, while their contributions left({h}_2to 4{tilde{chi}}_1^0right) to the invisible decay are very small.

Relaxing the Higgs mass and its vacuum energy by living at the top of the potential

We consider an ultra-light scalar coupled to the Higgs in the presence of heavier new physics. In the electroweak broken phase the Higgs gives a tree-level contribution to the light-scalar potential, while new physics contributes at loop level. Thereby, the theory has a cosmologically meta-stable phase where the light scalar is around the top of its potential, and the Higgs is a loop factor lighter than new physics. Such regions with precarious naturalness are anthropically and environmentally selected, as regions with heavier Higgs crunch quickly. We expect observable effects of rolling in the dark-energy equation of state. Furthermore, vacuum energies up to the weak scale can be canceled down to anthropically small values.

Power meets precision to explore the symmetric Higgs portal

We perform a comprehensive study of collider aspects of a Higgs portal scenario that is protected by an unbroken Z2 symmetry. If the mass of the Higgs portal scalar is larger than half the Higgs mass, this scenario becomes very difficult to detect. We provide a detailed investigation of the model's parameter space based on analyses of the direct collider sensitivity at the LHC as well as at future lepton and hadron collider concepts and analyse the importance of these searches for this scenario in the context of expected precision Higgs and electroweak measurements. In particular we also consider the associated electroweak oblique corrections that we obtain in a first dedicated two-loop calculation for comparisons with the potential of, e.g., GigaZ. The currently available collider projections corroborate an FCC-hh 100 TeV as a very sensitive tool to search for such a weakly-coupled Higgs sector extension, driven by small statistical uncertainties over a large range of energy coverage. Crucially, however, this requires good theoretical control. Alternatively, Higgs signal-strength measurements at an optimal FCC-ee sensitivity level could yield comparable constraints.

Funnel annihilations of light dark matter and the invisible decay of the Higgs boson

The semi-constrained NMSSM (scNMSSM), or NMSSM with non-universal Higgs masses, can naturally predict a light dark matter under current constraints including Higgs data, sparticle-mass bounds, dark matter searches, and muon g-2, etc. In this work, we take this scenario of scNMSSM as an example to study the funnel-annihilation mechanisms of light dark matter ($1\!\thicksim\!62$ GeV) and the invisible Higgs decay. In this scenario we found that: (i) There can be four funnel-annihilation mechanisms for the LSP $\tilde{\chi}^0_1$, which are the $h_2$, $Z$, $h_1$ and $a_1$ funnel. (ii) For the $h_1$ and $a_1$ funnel with right relic density, the $\tilde{\chi}^0_1$ mass is lighter than 12 GeV, and the invisible Higgs decay can be $2\%$ at most. (iii) For the $h_2$ and $Z$ funnel with right relic density, the invisible Higgs decay can be about $0.4\%$ and $1\%$ respectively at most. (iv) If the invisible Higgs decay was discovered at the HL-LHC, the four funnel-annihilation mechanisms of light dark matter may be all excluded with $\tilde{\chi}^0_1$ as the only dark matter source. Four benchmark points, one for each mechanism, are proposed for future checking with updated experimental results.

Scalegenesis and fermionic dark matters in the flatland scenario

We propose an extension of the standard model with Majorana-type fermionic dark matters based on the flatland scenario where all scalar coupling constants, including scalar mass terms, vanish at the Planck scale, i.e. the scalar potential is flat above the Planck scale. This scenario could be compatible with the asymptotic safety paradigm for quantum gravity. We search the parameter space so that the model reproduces the observed values such as the Higgs mass, the electroweak vacuum and the relic abundance of dark matter. We also investigate the spin-independent elastic cross section for the Majorana fermions and a nucleon. It is shown that the Majorana fermions as dark matter candidates could be tested by dark matter direct detection experiments such as XENON, LUX and PandaX-II. We demonstrate that within the minimal setup compatible with the flatland scenario at the Planck scale or asymptotically safe quantum gravity, the extended model could have a strong predictability.

An inflationary probe of cosmic Higgs switching

A scalar Higgs field can be repeatedly switched on and off when it couples to a classically oscillating scalar modulus field. The modulus flips the Higgs mass term between stable and tachyonic values. We study a cosmological scenario in which such repeated phase transitions occur during inflation. An irrelevant operator coupling the Higgs field to the inflaton can then imprint the pattern of phase transitions in the correlation functions of the inflaton. Using both numerical and analytic studies, we show that the inflaton 2-point function carries characteristic imprints of the modulus oscillation and its effect on the Higgs boson. We briefly remark on the potential observability of such patterns and how they might be distinguished from other dynamics in the early universe.

Light higgsino-dominated NLSPs in semi-constrained NMSSM * * Supported by the National Natural Science Foundation of China (NNSFC) (11605123)

In the semi-constrained next-to minimal supersymmetric standard model (scNMSSM, or NMSSM with non-universal Higgs mass) under current constraints, we consider a scenario where is the SM-like Higgs, is a singlino-dominated LSP; and are mass-degenerated, light, and higgsino-dominated next-to-lightest supersymmetric particles (NLSPs). We investigate the constraints of these NLSPs by searching for supersymmetry particles at the LHC Run-I and Run-II and discuss the possibility of discovering these NLSPs in the future. We arrive at the following conclusions: (i) With all data of Run I and up to data of Run II at the LHC, the search results by ATLAS and CMS still cannot exclude the higgsino-dominated NLSPs of . (ii) When the mass difference with is smaller than , and have opposite preferences with regard to decaying to or . (iii) When the mass difference between NLSP and LSP is larger than , most samples can be verified at the level with future data at the LHC. Meanwhile, with data at high-luminosity LHC (HL-LHC), almost all of the samples can be verified at the level, even if the mass difference is insufficient. (iv) The funnel and the funnel mechanisms for the singlino-dominated LSP annihilation cannot be distinguished by searching for NLSPs.

Alternative scale-invariant Higgs mass generation using hidden sector SU(Nc)xU(1)3

Spontaneous Symmetry Breaking (SSB) is a method to generate mass for all elementary particles in the Standard Model (SM). Even so, it turns out that the Higgs mass term in the Higgs potential, which responsible for the SSB, does not scale invariant. Based on this problem, instead of using SSB from the SM to explain the origin of mass, we erase Higgs’s mass term from the SM Lagrangean and introduce a hidden sector Lagrangean to produce an alternative way to generate Higgs mass. We use Scalar Bilinear Condensate ineffective theory to obtain Higgs mass via the Higgs portal and generate the SSB. The hidden sector in this alternative model is described by an SU(N C A) gauge theory with U(1)3 flavor. In the calculation, we use the Mean-Field Approximation Lagrangean in obtaining the vacuum of the potential to get a Higgs mass term in this model.