International Journal of Modern Physics A

We scrutinize the parameter space of the SM-like Higgs boson in the minimal supersymmetric standard model (MSSM) under current experimental constraints. The constraints are from (i) the precision electroweak data and various flavor observables; (ii) the direct 22 separate ATLAS searches in Run-1; (iii) the latest LHC Run-2 Higgs data and tri-lepton search of electroweakinos. We perform a scan over the parameter space and find that the Run-2 data can further exclude a part of parameter space. For the property of the SM-like Higgs boson, its gauge couplings further approach to the SM values with a deviation below 0.1%, while its Yukawa couplings $hb\bar{b}$ and $h{\tau }^{+}{\tau }^{-}$ can still sizably differ from the SM predictions by several tens percent.

Under current LHC and dark matter constraints, the general NMSSM can have self-interacting dark matter to explain the cosmological small structure. In this scenario, the dark matter is the light singlino-like neutralino $(\chi )$ which self-interacts through exchanging the light singlet-like scalars $(h_1,a_1)$. These light scalars and neutralinos inevitably interact with the 125 GeV SM-like Higgs boson $(h_{\mathrm{\text{SM}}})$, which cause the Higgs exotic decays $h_{\mathrm{\text{SM}}}\to h_1{h}_1$, $a_1{a}_1$, $\chi \chi$. We first demonstrate the parameter space required by the explanation of the cosmological small structure and then display the Higgs exotic decays. We find that in such a parameter space the Higgs exotic decays can have branching ratios of a few percent, which should be accessible in the future $e^{+}{e}^{-}$ colliders.

The Georgi–Machacek (GM) model predicts the existence of the doubly-charged scalars $H_5^{\pm \pm }$, which can be seen the typical particles in this model and their diboson decay channels are one of the most promising ways to discover such new doubly-charged scalars. Based on the constraints of the latest combined ATLAS and CMS Higgs boson diphoton signal strength data at $2\sigma$ confidence level, we focus on the study of the triple scalar production in $\gamma \gamma$ collisions at the future International Linear collider (ILC): $\gamma \gamma \to h{H}_5^{++}{H}_5^{--}$, where the production cross-sections are very sensitive to the triple scalar coupling parameter $g_{\mathrm{\text{hHH}}}$. Considering the typical same-sign diboson decay modes for the doubly-charged scalars, the possible final signals might be detected via this process at the future ILC experiments.

Recent years have seen increased use of Bayesian model comparison to quantify notions such as naturalness, simplicity, and testability, especially in the area of supersymmetric model building. After demonstrating that Bayesian model comparison can resolve a paradox that has been raised in the literature concerning the naturalness of the proton mass, we apply Bayesian model comparison to GUTs, an area to which it has not been applied before. We find that the GUTs are substantially favored over the nonunifying puzzle model. Of the GUTs we consider, the $B-L$ MSSM GUT is the most favored, but the MSSM GUT is almost equally favored.

We investigate the Higgs boson production processes $e^{+}{e}^{-}\to ZH$, $e^{+}{e}^{-}\to \nu \bar{\nu }H$, $e^{+}{e}^{-}\to t\bar{t}H$, $e^{+}{e}^{-}\to ZHH$ and $e^{+}{e}^{-}\to \nu \bar{\nu }HH$ in the littlest Higgs model with T-parity (LHT) at the International Linear Collider (ILC). We calculate the LHT model predictions on the production rate of these processes at the ILC in the case of (un)polarized beams and the signal strengths of the production processes $ZH$ and $\nu \bar{\nu }H$ with Higgs decaying to $b\bar{b}(gg,\gamma \gamma )$. In the allowed parameter space, we find that the signal strengths ${\mu }_{gg}$ is most likely approach to the expected precision of the ILC.

We update the well-known BLNY fit to the low transverse momentum Drell–Yan lepton pair productions in hadronic collisions, by considering the constraints from the semi-inclusive hadron production in deep inelastic scattering (SIDIS) from HERMES and COMPASS experiments. We follow the Collins–Soper–Sterman (CSS) formalism with the $b_{\ast }$-prescription. A nonperturbative form factor associated with the transverse momentum dependent quark distributions is found in the analysis with a new functional form different from that of BLNY. This releases the tension between the BLNY fit to the Drell–Yan data with the SIDIS data from HERMES/COMPASS in the CSS resummation formalism.

We consider a simple solution to explain the recent diboson excess observed by ATLAS and CMS Collaborations in models with custodial symmetry $SU{(2)}_L\times SU{(2)}_R\to SU{(2)}_c$. The $SU{(2)}_L$ triplet vector boson $\rho$ with mass range of $1.8\sim 2$ TeV would be produced through the Drell–Yan process with sizable diboson decay branching to account for the excess. The other $SU{(2)}_L\times SU{(2)}_R$ bidoublet axial vector boson $a$ would cancel all deviations of electroweak obervables induced by $\rho$ even if the SM fermions mix with some heavy vector-like (composite) fermions which couple to $\rho$ (“nonuniversally partially composite”), therefore allows arbitrary couplings between each SM fermion and $\rho$. We present our model in the “General Composite Higgs” framework with $SO(5)\times U{(1)}_X\to SO(4)\times U{(1)}_X$ breaking at scale $f$ and demand the first Weinberg sum rule and positive gauge boson form factors as the theoretical constraints. We find that our model can fit the diboson excess very well if the left-handed SM light quarks, charged leptons and tops have zero, zero/moderately small and moderate/large composite components for reasonable values of $g_{\rho }$ and $f$. The correlation between tree level $S$ parameter and the $h\to Z\gamma$ suggest a large $a$ contribution to $h\to Z\gamma$ and it is indeed a ${𝒪}(1)$ effect in our parameter space which provides a strong hint for our scenario if this diboson excess is confirmed by the $13\sim 14$ TeV LHC Run II.

Guided us by the scenario of weak scale naturalness and the possible existence of exotic resonances, we have explored in a $SO(5)$ Composite Higgs setup the interplay among three matter sectors: elementary, top partners and vector resonances. We parametrize it through explicit interactions of spin-1 $SO(4)$-resonances, coupled to the $SO(5)$-invariant fermionic currents and tensors presented in this work. Such invariants are built upon the Standard Model fermion sector as well as top partners sourced by the unbroken $SO(4)$. The mass scales entailed by the top partner and vector resonance sectors will control the low energy effects emerging from our interplaying model. Its phenomenological impact and parameter spaces have been considered via flavor-dijet processes and electric dipole moments bounds. Finally, the strength of the Nambu–Goldstone symmetry breaking and the extra couplings implied by the top partner mass scales are measured in accordance with expected estimations.

We find exact differential mean numbers of fermions and bosons created from the vacuum due to a composite electric field of special configuration. This configuration imitates a finite switching-on and -off regime and consists of fields that switch on exponentially from the infinitely remote past, remains constant during a certain interval $T$ and switch off exponentially to the infinitely remote future. We show that calculations in the slowly varying field approximation are completely predictable in the framework of a locally constant field approximation. Beyond the slowly varying field approximation, we study effects of fast switching on and off in a number of cases when the size of the dimensionless parameter $\sqrt{eE}T$ is either close or exceeds the threshold value that determines the transition from a regime sensitive to on–off parameters to the slowly varying regime for which these effects are secondary.

As the Higgs bosons were observed on the LHC in 2012, a two-stage particle collider program named CEPC-SPPC is proposed for precise measurement of Higgs properties and exploring the new physics models. In order to deliver a 2.1-TeV proton beam into the Super Proton–Proton Collider (SPPC), the injector chain will use a 1.2-GeV proton linac (p-Linac) and three synchrotrons of p-RCS, MSS and SS. This paper focuses on the preliminary conceptual design of the DTL within the p-Linac and mainly concerns about the beam dynamics studies. Taking advantages of the KONUS principle and LORASR code, a 325 MHz, 50.65 MeV DTL design which is composed of three tanks in 15.6 m will be presented. The whole DTL contains 129 gaps for beam acceleration, one quadruple doublet which is behind the buncher and eight quadruple triplets of which three are located after each tank, respectively. The aims of this pre-study are to optimize the acceleration electric field distribution together with the focusing magnetic field parameters, enhance the beam transmission quality of beam envelopes, particle distribution and energy spread, then improve the DTL performance in terms of transmission efficiency and so on. The results of the analyses show that the DTL pre-design achieves 16.8 times high energy gain and meets all the p-Linac requirements well.

We review the general heat kernel method for the Dirac spinor field as an elementary example in any arbitrary background. We, then compute the first three Seeley–DeWitt coefficients for the massless free spin-3/2 Rarita–Schwinger field without imposing any limitations on the background geometry.

We find exact, simple solutions to the Proca version of Maxwell’s equations with magnetic sources. Several properties of these solutions differ from the usual case of magnetic charge with a massless photon: (i) the string singularities of the usual 3-vector potentials become real singularities in the magnetic fields; (ii) the different 3-vector potentials become gauge inequivalent and physically distinct solutions; (iii) the magnetic field depends on r and $𝜃$ and thus is no longer rotationally symmetric; (iv) a combined system of electric and magnetic charge carries a field angular momentum even when the electric and magnetic charges are located at the same place (i.e. for dyons); (v) for these dyons, one recovers the standard Dirac condition despite the photon being massive. We discuss the reason for this. We conclude by proposing that the string singularity in the magnetic field of an isolated magnetic charge suggests a confinement mechanism for magnetic charge, similar to the flux tube confinement of quarks in QCD.