Search

In this paper, we study the discovery potential of a Vector-Like $B$ quark (VLB) via the process $pp \to B(\to bZ)j\to b(Z \to \nu_l\bar{\nu_l})j$ at the Large Hadron Collider (LHC) with $\sqrt{s}=14$ TeV. In the framework of a simplified model, we perform a scan over its parameter space and test its viability following a Monte Carlo analysis developed to include all production and decay dynamics. We use cut-and-count combined with Extreme Gradient Boosting (XGBoost) methods to classify the signal and background events in order to improve the efficiency of signal identification and background rejection. We find that this approach can reduce background events significantly while the signal retention rate is much higher than that of traditional methods, thereby improving the VLB discovery potential. We then calculate the exclusion and discovery capabilities for VLBs and find that the advantages of the cut-and-count plus XGBoost method especially lie in the high-mass region, i.e., $m_B > 1500 \text{ GeV}$. We finally obtain the following LHC results in terms of the coupling and chiral structure of a singlet heavy VLB interactions: (i) for $g^{\ast}$=0.2 and $R_L=0$ with 3000 fb$^{-1}$, the $B$ quark mass can be be excluded (discovered) up to 3000 GeV (2500 GeV); (ii) for $g^{\ast}$=0.2 and $R_L=0.5$ with 3000 fb$^{-1}$, the exclusion (discovery) region can reach up to 4750 GeV (4250 GeV)., Comment: 26 pages, 7 figures, 5 tables

Vector-like quarks have been predicted in various new physics scenarios beyond the Standard Model (SM). In a simplified modelling of a $(B,Y)$ doublet including a vector-like quark $Y$, with charge $-\frac{4}{3}$e, there are only two free parameters: the $Y$ coupling $\kappa_{Y}$ and mass $m_Y$. In the five flavor scheme, we investigate the single production of the $Y$ state decaying into $Wb$ at the Large Hadron Collider (LHC) Run-III and High-Luminosity LHC (HL-LHC) operating at $\sqrt{s}$ = 14 TeV, the possible High-Energy LHC (HE-LHC) with $\sqrt{s}$ = 27 TeV as well as the Future Circular Collider in hadron-hadron mode (FCC-hh) with $\sqrt{s}$ = 100 TeV. Through detailed signal-to-background analyses and detector simulations, we assess the exclusion capabilities of the $Y$ state at the different colliders. We find that this can be improved significantly with increasing collision energy, especially at the HE-LHC and FCC-hh, both demonstrating an obvious advantage with respect to the HL-LHC in the case of high $m_Y$. Assuming a 10\% systematic uncertainty on the background event rate, the exclusion capabilities are summarized as follows: (1) the LHC Run-III can exclude the correlated regions of $\kappa_{Y} \in [0.06,0.5]$ and $m_{Y} \in [1500\text{ GeV},3800\text{ GeV}]$ with integrated luminosity $L = 300\text{ fb}^{-1}$; (2) the HL-LHC can exclude the correlated regions of $\kappa_{Y} \in [0.05,0.5]$ and $m_{Y} \in [1500\text{ GeV},3970\text{ GeV}]$ with $L = 3$ ab$^{-1}$; (3) the HE-LHC can exclude the correlated regions of $\kappa_Y \in [0.06,0.5]$ and $m_{Y} \in [1500\text{ GeV} , 6090\text{ GeV}]$ with $L = 3$ ab$^{-1}$; (4) the FCC-hh can exclude the correlated regions of $\kappa_{Y} \in [0.08,0.5]$ and $m_{Y} \in [1500\text{ GeV} , 10080\text{ GeV}]$ with $L = 3$ ab$^{-1}$., Comment: 28 pages + references, 7 figures, 5 tables; matches version published in PRD

Searches for new particles beyond the Standard Model (SM) are an important task for the Large Hadron Collider (LHC). In this paper, we investigate the properties of the heavy non-SM Higgs bosons in the $\mu$-term extended Next-to-Minimal Supersymmetric Standard Model ($\mu$NMSSM). We scan the parameter space of the $\mu$NMSSM considering the basic constraints from Higgs data, dark matter (DM) relic density, and LHC searches for sparticles. And we also consider the constraints from the LZ2022 experiment and the muon anomaly constraint at 2$\sigma$ level. We find that the LZ2022 experiment has a strict constraint on the parameter space of the $\mu$NMSSM, and the limits from the DM-nucleon spin-independent (SI) and spin-dependent (SD) cross-sections are complementary. Then we discuss the exotic decay modes of heavy Higgs bosons decaying into SM-like Higgs boson. We find that for doublet-dominated Higgs $h_3$ and $A_2$, the main exotic decay channels are $h_3\rightarrow Z A_1$, $h_3\rightarrow h_1 h_2$, $A_2\rightarrow A_1 h_1$ and $A_2\rightarrow Z h_2$, and the branching ratio can reach to about 23$\%$, 10$\%$, 35$\%$ and 10$\%$ respectively. At the 13 TeV LHC, the production cross-section of $ggF\rightarrow h_3\rightarrow h_1 h_2$ and $ggF\rightarrow A_2\rightarrow A_1 h_1$ can reach to about $10^{-11}$pb and $10^{-10}$pb, respectively.

We present an application, EasyScan_HEP, for connecting programs to scan the parameter space of High Energy Physics (HEP) models using various sampling algorithms. We develop EasyScan_HEP according to the principle of flexibility and usability. EasyScan_HEP allows us to connect different programs that calculate physical observables, and apply constraints by one human-readable configuration file. All programs executed through command lines can be connected to EasyScan_HEP by setting input and output parameters of the programs. The current version offers the sampling algorithms of Random, Grid, Markov chain Monte Carlo and MultiNest. We also implement features such as resume function, parallelization, post-processing, and quick analysis., Comment: 42 pages, 4 figures, 5 tables, 10 listings, version accepted by Computer Physics Communications

Based on a simplified model including a singlet vector-like top quark $T$ with charge $|Q|=2/3$, we analyze the prospects of observing $T$ via the single $T$ production in the $tZ$ channel with $Z$ decaying to neutrinos at the hadron-hadron colliders. This simplified model only includes two free parameters, the coupling constant $g^*$ and the $T$ quark mass $m_T$. To investigate the observability of the single $T$ production, we perform a detailed background analysis and detector simulation for the collision energies 14~TeV, 27~TeV, and 100~TeV. We scan the $g^*-m_T$ parameter space and show the exclusion and discovery capabilities on the $T$ quark with the highest integrated luminosity designed at these colliders. Moreover, the limits from the narrow-width approximation and electroweak precision observables are considered., Comment: 17 pages, 7 figures. References added

The $Z_3$-invariant next-to-minimal supersymmetric standard model (NMSSM) can provide a candidate for dark matter (DM). It can also be used to explain the hypothesis that the Higgs signal observed on the Large Hadron Collider (LHC) comes from the contribution of the two lightest CP-even Higgs bosons, whose masses are near 125 GeV. At present, XENON1T, LUX, and PandaX experiments have imposed very strict restrictions on direct collision cross sections of {dark matter}. In this paper, we consider a scenario that the observed Higgs signal is the superposition of two mass-degenerate Higgs in the $Z_3$-invariant NMSSM and scan the seven-dimension parameter space composing of $\lambda, \kappa, \tan\beta, \mu, A_k, A_t, M_1$ via the Markov chain Monte Carlo (MCMC) method. We find that the DM relic density, as well as the LHC searches for sparticles, especially the DM direct detections, has provided a strong limit on the parameter space. %Please check intended meaning has been retained. The allowed parameter space is featured by a relatively small $\mu \le 300$ GeV and about $\tan\beta\in(10,20)$. In addition, the DM is Higgsino-dominated because of $|\frac{2\kappa}{\lambda}|>1$. Moreover, the co-annihilation between $\tilde{\chi}_1^0$ and $\tilde{\chi}_1^\pm$ must be taken into account to obtain the reasonable DM relic density.

The new measurement of $W$-boson mass by the CDF collaboration revealed a remarkable $7\sigma$ disagreement with the Standard Model (SM) prediction. If confirmed by other experiments, then the disagreement strongly indicates the existence of new physics beyond the SM. In this work, seven vectorlike quark (VLQ) extensions of the SM are investigated to interpret the anomaly, and it is found that three can explain the anomaly in broad parameter space. The explanations are consistent with the constraints from oblique parameters, the LHC search for VLQs, the measurements of the properties for the top quark, bottom quark, and Higgs boson, and the perturbativity criterion. The typical size of the involved Yukawa coupling is around 1, which is comparable to the top quark Yukawa coupling in the SM. The other extensions, however, either predict a negative correction to the mass in reasonable parameter space or explain the anomaly by unnatural theoretical input parameters., Comment: This article should be an updated version of 2204.09477

The new measurement of $W$-boson mass by the CDF collaboration revealed a remarkable $7\sigma$ disagreement with the Standard Model (SM) prediction. If confirmed by other experiments, then the disagreement strongly indicates the existence of new physics beyond the SM. In this work, seven vectorlike quark (VLQ) extensions of the SM are investigated to interpret the anomaly, and it is found that three can explain the anomaly in broad parameter space. The explanations are consistent with the constraints from oblique parameters, the LHC search for VLQs, the measurements of the properties for the top quark, bottom quark, and Higgs boson, and the perturbativity criterion. The typical size of the involved Yukawa coupling is around 1, which is comparable to the top quark Yukawa coupling in the SM. The other extensions, however, either predict a negative correction to the mass in reasonable parameter space or explain the anomaly by unnatural theoretical input parameters., Comment: 33 pages, 7 figures. A factor 1/2 is added to Eq. 17 (thanks to the comments of Dr. S. P. He), all figures are updated, and the conclusions in the previous version are unchanged. Published in PRD 106 (2022) 5, 055042

We chose the $\mu$-term extended next-to-minimal supersymmetric standard model ($\mu$NMSSM) for this work, and the phenomenological research is based on the assumption of double Higgs resonance state as the Standard Model (SM)-like Higgs considering the recent $(g-2)_\mu$ result. The study also take into account a variety of experimental results, including direct detection of dark matter (DM) and searching results for sparticles at the Large Hadron Collider (LHC). We study the characteristic of DM confronted with limitations of direct detection experiments. Following that, we concentrate on the properties of the mass-degenerate SM-like Higgs bosons and explaining the anomaly of $(g-2)_\mu$. We conclude that the anomaly of $(g-2)_\mu$ can be explained in the scenario with two mass-degenerate SM-like Higgs, and there are samples that meet all current constraints and outperform SM in fitting Higgs data.

In the natural realization of the Next-to-minimal Supersymmetric Standard Model, Higgsinos tend to be lighter than about several hundred GeVs, which can induce detectable leptonic signals at the LHC as well as large DM-nucleon scattering cross section. We explore the constraints from the direct searches for electroweakino and slepton at the LHC Run II and the latest DM direct detection experiments on the scenario with low fine tuning indicator $\Delta_{Z/h} \leq 50$. We find that these experiments are complementary to each other in excluding the scenario, and as far as each kind of experiment is concerned, it is strong enough to exclude a large portion of the parameter space. As a result, the scenario with Bino- or Higgsino-dominated DM is disfavored, and that with Singlino-dominated DM is tightly limited. There are two regions in natural NMSSM parameter space surviving in the current experimental limits. One is featured with a decoupled Singlino-dominated LSP with $\mu \simeq m_{\widetilde{\chi}_1^0}$, which cannot be explored by neither DM detections or collider searches. The other parameter space region is featured by $10^{-47}~{\rm cm^2} \lesssim \sigma^{SI}_{\widetilde{\chi}-p} \lesssim 10^{-46}~{\rm cm^2}$ and the correlation $\mu \simeq m_{\widetilde{\chi}_1^0}$, which will be explored by near future DM detection experiments., Comment: 21 figures, 30 pages

In the Next-to-Minimal Supersymmetric Standard Model (NMSSM) with extra heavy neutrino superfields, neutrino may acquire its mass via a seesaw mechanism and sneutrino may act as a viable dark matter (DM) candidate. Given the strong tension between the naturalness for $Z$ boson mass and the DM direct detection experiments for customary neutralino DM candidate, we augment the NMSSM with Type-I seesaw mechanism, which is the simplest extension of the theory to predict neutrino mass, and study the scenarios of sneutrino DM. We construct likelihood function with LHC Higgs data, B-physics measurements, DM relic density and its direct and indirect search limits, and perform a comprehensive scan over the parameter space of the theory by Nested Sampling method. We adopt both Bayesian and frequentist statistical quantities to illustrate the favored parameter space of the scenarios, the DM annihilation mechanism as well as the features of DM-nucleon scattering. We find that the scenarios are viable over broad parameter regions, especially the Higgsino mass $\mu$ can be below about $250 {\rm GeV}$ for a significant part of the region, which predicts $Z$ boson mass in a natural way. We also find that the DM usually co-annihilated with the Higgsinos to get the measured relic density, and consequently the DM-nucleon scattering rate is naturally suppressed to coincide with the recent XENON-1T results even for light Higgsinos. Other issues, such as the LHC search for the Higgsinos, are also addressed., Comment: accepted version by PRD

The Weakly Interacting Massive Particle (WIMP) has been one of the most attractive candidates for Dark Matter (DM), and the lightest neutralino ($\widetilde{\chi}^0_1$) in the Next-to-Minimal Supersymmetric Standard Model (NMSSM) is an interesting realization of WIMP. The Galactic Center Excess (GCE) can be explained by WIMP DM annihilations in the sky. In this work we consider the $Z_3$-NMSSM where the singlet $S$ and Singlino $\widetilde{S}^0$ components play important roles in the Higgs and DM sector. Guided by our analytical arguments, we perform a numerical scan over the NMSSM parameter space for the GCE explanation by considering various observables such as the Standard Model (SM) Higgs data measured by the ATLAS and CMS experiments, and the $B$-physics observables $BR(B_s\rightarrow X_s\gamma)$ and $BR(B_s\rightarrow \mu^+\mu^-)$. We find that the correlation between the coupling $C_{A_1 b\bar{b}}$ in $\langle \sigma_{b\bar{b}} v \rangle _{0}$ and the coupling $C_{Z \widetilde{\chi}^0_1 \widetilde{\chi}^0_1}$ in DM-neutron Spin Dependent (SD) scattering rate $\sigma^{SD}_{\widetilde{\chi}^0_1-N}$ makes all samples we obtain for GCE explanation get excluded by the PandaX-II results. Although the DM resonant annihilation scenarios may be beyond the reach of our analytical approximations and scan strategy, the aforementioned correlation can be a reasonable motivation for future experiments such as PandaX-nT to further test the NMSSM interpretation of GCE., Comment: 11 pages, 4 figures, meeting the published version by EPJC

Left-Right symmetric model (LRSM) has been an attractive extension of the Standard Model (SM) which can address the origin of parity violation in the SM electroweak (EW) interactions, generate tiny neutrino masses, accommodate dark matter (DM) candidates and provide a natural framework for baryogenesis through leptogenesis. In this work we utilize the minimal LRSM to study the recently reported DAMPE results of cosmic $e^+e^-$ spectrum which exhibits a tentative peak around 1.4 TeV, while satisfying the current neutrino data. We propose to explain the DAMPE peak with a complex scalar DM $\chi$ in two scenarios: 1) $\chi\chi^* \to H_1^{++}H_1^{--} \to \ell_i^+\ell_i^+\ell_j^-\ell_j^-$; 2) $\chi\chi^* \to H_{k}^{++}H_{k}^{--} \to \ell_i^+\ell_i^+\ell_j^-\ell_j^-$ accompanied by $\chi\chi^* \to H_1^+ H_1^- \to \ell_i^+ \nu_{\ell_i} \ell_j^- \nu_{\ell_j}$ with $\ell_{i,j}=e,\mu,\tau$ and $k=1,2$. We fit the theoretical prediction on $e^+e^-$ spectrum to relevant experimental data to determine the scalar mass spectrum favored by the DAMPE excess. We also consider various constraints from theoretical principles, collider experiments as well as DM relic density and direct search experiments. We find that there are ample parameter space which can interpret the DAMPE data while passing the constraints. Our explanations, on the other hand, usually imply the existence of other new physics at the energy scale ranging from $10^7 {\rm GeV}$ to $10^{11} {\rm GeV}$. Collider tests of our explanations are also discussed., Comment: 25 pages, 4 figures, 4 Tables, refined discussions about motivation of introducing scalar DM to LRSM, partial 2-loop RGE

Inspired by the peak structure observed by recent DAMPE experiment in $e^+e^-$ cosmic-ray spectrum, we consider a scalar dark matter (DM) model with gauged $U(1)_{L_e-L_\mu}$ symmetry, which is the most economical anomaly-free theory to potentially explain the peak by DM annihilation in nearby subhalo. We utilize the process $\chi \chi \to Z^\prime Z^\prime \to l \bar{l} l^\prime \bar{l}^\prime$, where $\chi$, $Z^\prime$, $l^{(\prime)}$ denote the scalar DM, the new gauge boson and $l^{(\prime)} =e, \mu$, respectively, to generate the $e^+e^-$ spectrum. By fitting the predicted spectrum to the experimental data, we obtain the favored DM mass range $m_\chi \simeq 3060^{+80}_{-100} \, {\rm GeV}$ and $\Delta m \equiv m_\chi - m_{Z^\prime} \lesssim 14 \, {\rm GeV}$ at $68\%$ Confidence Level (C.L.). Furthermore, we determine the parameter space of the model which can explain the peak and meanwhile satisfy the constraints from DM relic abundance, DM direct detection and the collider bounds. We conclude that the model we consider can account for the peak, although there exists a tension with the constraints from the LEP-II bound on $m_{Z^\prime}$ arising from the cross section measurement of $e^+e^- \to Z^{\prime\ast} \to e^+ e^-$., Comment: 15 pages, 4 figures

Recently, DAMPE experiment released the new measurement of the total cosmic $e^+e^-$ flux between 25 GeV and 4.6 TeV which indicates a spectral softening at around 0.9 TeV and a tentative peak at around 1.4 TeV. We utilize the scalar dark matter (DM) annihilation scenario to explain the DAMPE peak by extending $G_{SM}\equiv SU(3)_C \times SU(2)_L \times U(1)_Y$ with additional $U(1)$ gauge symmetries while keeping anomaly free to generate $\chi \chi \to Z^\prime Z^\prime \to \ell\bar{\ell}\ell^\prime\overline{\ell^\prime}$, where $\chi, Z^\prime, \ell^{(^\prime)}$ denote the scalar DM, the new gauge boson and $\ell^{(^\prime)}=e,\mu,\tau$, respectively, with $m_\chi \sim m_{Z^\prime} \sim 2 \times 1.5$ (TeV). We first illustrate that the minimal framework $G_{SM} \times U(1)_{Y^\prime}$ with the above mass choices can explain the DAMPE excess but has been excluded by LHC constraints from the $Z^\prime$ searches. Then we study a non-minimal framework $G_{SM} \times U(1)_{Y^\prime} \times U(1)_{Y^{\prime \prime}}$ in which $U(1)_{Y^{\prime \prime}}$ mixes with $U(1)_{Y^\prime}$. We show that such a framework can interpret the DAMPE data while passing other constraints including the DM relic abundance, DM direct detection and collider bounds. We also investigate the predicted $e^+e^-$ spectrum in this framework and find that the mass splitting $\Delta m = m_\chi - m_{Z'}$ should be less than about 17 GeV to produce the peak-like structure., Comment: 15 pages, 6 figures, 3 tables

In supersymmetric theories like the Next-to-Minimal Supersymmetric Standard Model (NMSSM), the lightest neutralino with bino or singlino as its dominant component is customarily taken as dark matter (DM) candidate. Since light Higgsinos favored by naturalness can strength the couplings of the DM and thus enhance the DM-nucleon scattering rate, the tension between naturalness and DM direct detection results becomes more and more acute with the improved experimental sensitivity. In this work, we extend the NMSSM by inverse seesaw mechanism to generate neutrino mass, and show that in certain parameter space the lightest sneutrino may act as a viable DM candidate, i.e. it can annihilate by multi-channels to get correct relic density and meanwhile satisfy all experimental constraints. The most striking feature of the extension is that the DM-nucleon scattering rate can be naturally below its current experimental bounds regardless of the higgsino mass, and hence it alleviates the tension between naturalness and DM experiments. Other interesting features include that the Higgs phenomenology becomes much richer than that of the original NMSSM due to the relaxed constraints from DM physics and also due to the presence of extra neutrinos, and that the signatures of sparticles at colliders are quite different from those with neutralino as DM candidate., Comment: 33 pages

Given the fact that the relatively light Higgsino mass $\mu$ favored in natural supersymmetry usually results in a sizable scattering cross section between the neutralino dark matter and the nucleon, we study the impact of the recently updated direct detection bounds from LUX experiment, including both Spin Independent (SI) and Spin Dependent (SD) measurements, on the parameter space of natural Next-to-Minimal Supersymmetric Standard Model (nNMSSM). Different from the common impression that the SI bound is stronger than the SD one, we find that the SD bound is complementary to the SI bound and in some cases much more powerful than the latter in limiting the nNMSSM scenarios. After considering the LUX results, nNMSSM is severely limited, e.g. for the peculiar scenarios of the NMSSM where the next-to-lightest CP-even Higgs corresponds to the $125 {\rm GeV}$ Higgs boson discovered at the LHC, the samples obtained in our random scan are excluded by more than $85\%$. By contrast, the monojet search at the LHC Run-I can not exclude any sample of nNMSSM. We also investigate the current status of nNMSSM and conclude that, although the parameter points with low fine tuning are still attainable, they are distributed in some isolated parameter islands which are difficult to get. Future dark matter direct search experiments such as XENON-1T will provide a better test of nNMSSM., Comment: 20 pages, 10 figures, meet JHEP published version

We investigate the impact of the direct searches for SUSY at LHC Run I on the naturalness of the Next-to-Minimal Supersymmetric Standard Model (NMSSM). For this end, we first scan the vast parameter space of the NMSSM to get the region where the fine tuning measures $\Delta_Z$ and $\Delta_h$ at the electroweak scale are less than about 50, then we implement by simulations the constraints of the direct searches on the parameter points in the region. Our results indicate that although the direct search experiments are effective in excluding the points, the parameter intervals for the region and also the minimum reaches of $\Delta_Z$ and $\Delta_h$ are scarcely changed by the constraints, which implies that the fine tuning of the NMSSM does not get worse after LHC Run I. Moreover, based on the results we propose a natural NMSSM scenario where the lightest neutralino $\tilde{\chi}_1^0$ as the dark matter (DM) candidate is Higgsino-dominated. In this scenario, $\Delta_Z$ and $\Delta_h$ may be as low as 2 without conflicting with any experimental constraints, and intriguingly $\tilde{\chi}_1^0$ can easily reach the measured DM relic density due to its significant Singlino component. We exhibit the features of the scenario which distinguish it from the other natural SUSY scenario, including the properties of its neutralino-chargino sector and scalar top quark sector. We emphasize that the scenario can be tested either through searching for $3 l + E_T^{miss}$ signal at 14 TeV LHC or through future DM direct detection experiments., Comment: 26 pages, 5 figures

We try to interpret the 750 GeV diphoton excess in the Minimal Dilaton Model, which extends the SM by adding one linearized dilaton field and vector-like fermions. We first show by analytic formulae in this framework that the production rates of the $\gamma \gamma$, $gg$, $Z\gamma$, $ZZ$, $WW^\ast$, $t\bar{t}$ and $hh$ signals at the $750 {\rm GeV}$ resonance are only sensitive to the dilaton-Higgs mixing angle $\theta_S$ and the parameter $\eta \equiv v N_X/f$, where $f$ is the dilaton decay constant and $N_X$ denotes the number of the fermions. Then we scan the two parameters by considering various theoretical and experimental constraints to find the solutions to the diphoton excess. We conclude that the model can predict the central value of the diphoton rate without conflicting with any constraints. The signatures of our explanation at the LHC Run II and the vacuum stability at high energy scale are also discussed., Comment: Accepted by EPJC

We propose to interpret the 750 GeV diphoton excess in a typical topflavor seesaw model. The new resonance X can be identified as a CP-even scalar emerging from a certain bi-doublet Higgs field. Such a scalar can couple to charged scalars, fermions as well as heavy gauge bosons predicted by the model, and consequently all of the particles contribute to the diphoton decay mode of the X. Numerical analysis indicates that the model can predict the central value of the diphoton excess without contradicting any constraints from 8 TeV LHC, and among the constraints, the tightest one comes from the Z \gamma channel, \sigma_{8 {\rm TeV}}^{Z \gamma} \lesssim 3.6 {\rm fb}, which requires \sigma_{13 {\rm TeV}}^{\gamma \gamma} \lesssim 6 {\rm fb} in most of the favored parameter space., Comment: Major changes, 17 pages, 4 figure, typos corrected, calculation details added

The evidence of a new scalar particle $X$ from the 750 GeV diphoton excess, and the absence of any other signal of new physics at the LHC so far suggest the existence of new colored scalars, which may be moderately light and thus can induce sizable $X g g$ and $X \gamma \gamma$ couplings without resorting to very strong interactions. Motivated by this speculation, we extend the Manohar-Wise model by adding one gauge singlet scalar field. The resulting theory then predicts one singlet dominated scalar $\phi$ as well as three kinds of color-octet scalars, which can mediate through loops the $\phi gg$ and $\phi \gamma \gamma$ interactions. After fitting the model to the diphoton data at the LHC, we find that in reasonable parameter regions the excess can be explained at $1\sigma$ level by the process $ g g \to \phi \to \gamma \gamma$, and the best points predict the central value of the excess rate with $\chi_{min}^2=2.32$, which corresponds to a $p$-value of $0.68$. We also consider the constraints from various LHC Run I signals, and we conclude that, although these constraints are powerful in excluding the parameter space of the model, the best points are still experimentally allowed., Comment: 19 pages, 3 figures

In the light dark matter (DM) scenario of the MSSM, the DM relic density puts non-trivial requirements on the spectrum of supersymmetric particles. As a result, the direct search for multi-lepton signals at the LHC has great impact on the scenario. In this work, we concentrate on the searches for sleptons and electroweak-inos at the LHC, and investigate the constraints on the light DM scenario from the 8 TeV LHC data as well as the capability of the 14 TeV LHC to test the scenario. We first get the samples of the scenario by scanning the vast parameter space of the MSSM and considering some easily available constraints, such as those from the DM relic density, the LUX experiment and the Higgs searches at colliders. Then for the surviving samples, we simulate the $2l+E_T^{miss}$ signal from slepton pair production process and the $2l+E_T^{miss}$ and $3l+E_T^{miss}$ signals from chargino and neutralino associated production processes at both the 8 TeV LHC and the 14 TeV LHC. Our simulations indicate that the 8 TeV LHC has excluded a sizable portion of the samples, and the 14 TeV LHC can be even much more powerful in testing the scenario. For example, in case that no multi-lepton signals are observed at the 14 TeV LHC, most samples of the light DM scenario will be excluded, especially a lower limit on the lightest neutralino mass will be set at 42 GeV and 44 GeV with 30 $fb^{-1}$ and 100 $fb^{-1}$ data respectively, and this limit can be further pushed up to $55\ {\rm GeV}$ with 300 $fb^{-1}$ data., Comment: 20 pages, 4 figures

The ATLAS collaboration recently reported a $3\sigma$ excess in the leptonic-$Z+jets+E_{T}^{miss}$ channel. We intend to interpret this excess by squark pair production in the Next-to-Minimal Supersymmetric Standard Model (NMSSM). The decay chain we employ is $\tilde{q} \to q \tilde{\chi}_2^0 \to q \tilde{\chi}_1^0 Z$, where $\tilde{\chi}_1^0$ and $\tilde{\chi}_2^0$ denote the lightest and the next-to-lightest neutralinos with singlino and bino as their dominant components respectively. Our simulations indicate that after considering the constraints from the ATLAS searches for $jets + E_{T}^{miss}$ signal the central value of the excess can be obtained for $m_{\tilde{q}} \lesssim 1.2 {\rm TeV}$, and if the constraint from the CMS on-$Z$ search is further considered, more than 10 signal events are still attainable for $m_{\tilde{q}} \lesssim 750 {\rm GeV}$. Compared with the interpretation by gluino pair production, the squark explanation allows for a significantly wider range of $m_{\tilde{q}}$ as well as a less compressed SUSY mass spectrum. We also show that the squark explanation will be readily tested at the initial stage of the 14 TeV LHC., Comment: 19 pages, 4 figures

In the Next-to-Minimal Supersymmetric Standard Model (NMSSM), all singlet-dominated particles including one neutralino, one CP-odd Higgs boson and one CP-even Higgs boson can be simultaneously lighter than about 100 GeV. Consequently, dark matter (DM) in the NMSSM can annihilate into multiple final states to explain the galactic center gamma-ray excess (GCE). In this work we take into account the foreground and background uncertainties for the GCE and investigate these explanations. We carry out a sophisticated scan over the NMSSM parameter space by considering various experimental constraints such as the Higgs data, $B$-physics observables, DM relic desnity, LUX experiment and the dSphs constraints. Then for each surviving parameter point we perform a fit to the GCE spectrum by using the correlation matrix that incorporates both the statistical and systematic uncertainties of the measured excess. After examining the properties of the obtained GCE solutions, we conclude that the GCE can be well explained by the pure annihilations $\tilde{\chi}_1^0 \tilde{\chi}_1^0 \to b \bar{b} $ and $\tilde{\chi}_1^0 \tilde{\chi}_1^0 \to A_1 H_i $ with $A_1$ being the lighter singlet-dominated CP-odd Higgs boson and $H_i$ denoting the singlet-dominated CP-even Higgs boson or SM-like Higgs boson, and it can also be explained by the mixed annihilation $\tilde{\chi}_1^0 \tilde{\chi}_1^0 \to W^+ W^-, A_1 H_1$. Among these annihilation channels, $\tilde{\chi}_1^0 \tilde{\chi}_1^0 \to A_1 H_i $ can provide the best interpretation with the corresponding $p$-value reaching 0.55. We also discuss to what extent the future DM direct detection experiments can explore the GCE solutions and conclude that the XENON-1T experiment is very promising in testing nearly all the solutions., Comment: 31 pages, 7 figures

Recently the ATLAS collaboration reported a $3\sigma$ excess in the leptonic-$Z+jets+E_{T}^{miss}$ channel. This may be interpreted in the Next-to-Minimal Supersymmetric Standard Model (NMSSM) by gluino pair production with the decay chain $\tilde{g} \to q \bar{q} \tilde{\chi}_2^0 \to q \bar{q} Z \tilde{\chi}_1^0$, where $\tilde{\chi}_1^0$ and $\tilde{\chi}_2^0$ denote the lightest and the next-to-lightest neutralinos with singlino and bino as their dominant components respectively. After exploring the relevant parameter space of the NMSSM by considering the constraints from the ATLAS searches for $jets + E_{T}^{miss}$ signals, we conclude that the NMSSM is able to explain the excess at $1 \sigma$ level with the number of the signal events reaching its measured central value in optimal cases, and the best explanation comes from a compressed spectrum such as $m_{\tilde{g}} \simeq 650 {\rm GeV}$, $m_{\tilde{\chi}_2^0} \simeq 565 {\rm GeV}$ and $m_{\tilde{\chi}_1^0} \simeq 465 {\rm GeV}$. We also check the consistency of the ATLAS results with the null result of the CMS on-$Z$ search. We find that under the CMS limits at $95\%$ C.L., the event number of the ATLAS on-$Z$ signal can still reach 11 in our scenario, which is about $1.2 \sigma$ away from the measured central value., Comment: 18 pages, 2 figures

We explore the explanation of the Fermi Galactic Center Excess (GCE) in the Next-to-Minimal Supersymmetric Standard Model. We systematically consider various experimental constraints including the Dark Matter (DM) relic density, DM direct detection results and indirect searches from dwarf galaxies. We find that, for DM with mass ranging from $30 {\rm GeV}$ to $40 {\rm GeV}$, the GCE can be explained by the annihilation $\chi \chi \to a^\ast \to b \bar{b}$ only when the CP-odd scalar satisfies $m_a \simeq 2 m_\chi$, and in order to obtain the measured DM relic density, a sizable $Z$-mediated contribution to DM annihilation must intervene in the early universe. As a result, the higgsino mass $\mu$ is upper bounded by about 350 GeV. Detailed Monte Carlo simulations on the $3\ell+ E_T^{miss}$ signal from neutralino/chargino associated production at 14-TeV LHC indicate that the explanation can be mostly (completely) excluded at $95\%$ C.L. with an integrated luminosity of 100(200) fb$^{-1}$. We also discuss the implication of possible large $Z$ coupling to DM for the DM-nucleon spin dependent (SD) scattering cross section, and find that although the current experimental bounds on $\sigma^{\rm SD}_p$ is less stringent than the spin independent (SI) results, the future XENON-1T and LZ data may be capable of testing most parts of the GCE-favored parameter region., Comment: 6 pages, 3 figures

As a most natural realization of the Next-to Minimal Supersymmetry Standard Model (NMSSM), {\lambda}-SUSY is parameterized by a large {\lambda} around one and a low tan$\beta$ below 10. In this work, we first scan the parameter space of {\lambda}-SUSY by considering various experimental constraints, including the limitation from the Higgs data updated by the ATLAS and CMS collaborations in the summer of 2014, then we study the properties of the Higgs bosons. We get two characteristic features of {\lambda}-SUSY in experimentally allowed parameter space. One is the triple self coupling of the SM-like Higgs boson may get enhanced by a factor over 10 in comparison with its SM prediction. The other is the pair production of the SM-like Higgs boson at the LHC may be two orders larger than its SM prediction. All these features seems to be unachievable in the Minimal Supersymmetric Standard Model and in the NMSSM with a low {\lambda}. Moreover, we also find that naturalness plays an important role in selecting the parameter space of {\lambda}-SUSY, and that the Higgs $\chi^2$ obtained with the latest data is usually significantly smaller than before due to the more consistency of the two collaboration measurements.

We investigate the Higgs-strahlung production process e^+ e^- \to Z h at the future Higgs factory such as TLEP by including radiative corrections in the Minimal Dilaton Model (MDM), which extends the SM by one singlet scalar called dilaton. We consider various theoretical and experimental constraints on the model, and perform fits to the Higgs data taken from ATLAS, CMS and CDF+D0. Then for the 1\sigma surviving samples, we calculate the MDM predictions on the inclusive production rate \sigma(e^+e^-\to Zh) at the 240-GeV Higgs factory, and also the signal rates of e^+e^-\to Zh with the Higgs boson decaying to b\bar b and \gamma\gamma. We have following observations: (1) In the heavy dilaton scenario, the deviation of \sigma(e^+e^-\to Zh) from its SM prediction can vary from -15\% to 85\%, which mainly arises from the modification of the tree-level hZZ coupling and also the radiative correction induced by possibly large Higgs self-couplings. (2) The processes e^+e^-\to Zh at the Higgs factory and pp\to hh at 14-TeV LHC are complementary in limiting the MDM parameter space. Requiring the deviation of \sigma(e^+e^-\to Zh) from its SM prediction to be less than 1\% and that of \sigma(p p \to h h) to be less than 50\%, \tan \theta_S in the MDM will be limited to be -0.1<\tan\theta_S<0.3, and the deviations of the signal rates are constrained to be |R_{b\bar b}|<2\% and |R_{\gamma\gamma}|<7\%. Especially, the Higgs self-coupling normalized to its SM prediction is now upper bounded by about 4. (3) In the light dilaton scenario, the deviation of \sigma(e^+e^-\to Zh) may reach -7\%, and requiring its size to be less than 1\% will result in 0<\tan\theta_S<0.1, and -10\% < R_{b\bar b}, R_{\gamma\gamma} < 1\%., Comment: 18pages, 8 fiugres, References added

Although the Higgs boson mass and single production rate have been determined more or less precisely, its other properties may deviate significantly from its predictions in the standard model (SM) due to the uncertainty of Higgs data. In this work we study the Higgs pair production at the LHC in the Manohar-Wise model, which extends the SM by one family of color-octet and isospin-doublet scalars. We first scanned over the parameter space of the Manohar-Wise model considering exprimental constraints and performed fits in the model to the latest Higgs data by using the ATLAS and CMS data separately. Then we calculated the Higgs pair production rate and investigated the potential of its discovery at the LHC14. We conclude that: (i) Under current constrains including Higgs data after Run I of the LHC, the cross section of Higgs pair production in the Manohar-Wise model can be enhanced up to even $10^3$ times prediction in the SM. (ii) Moreover, the sizable enhancement comes from the contributions of the CP-odd color-octet scalar $S^A_I$. For lighter scalar $S^A_I$ and larger values of $|\lambda_I|$, the cross section of Higgs pair production can be much larger. (iii) After running again of LHC at 14 TeV, most of the parameter spaces in the Manohar-Wise model can be test. For an integrated luminosity of 100 fb$^{-1}$ at the LHC14, when the normalized ratio $R=10$, the process of Higgs pair production can be detected., Comment: 13 pages, 4 figures

In this work we investigate the Higgs pair production in the MSSM and NMSSM at the photon-photon collision of the ILC. We consider various experimental constraints and scan over the parameter space of the MSSM and NMSSM. Then we calculate the cross section of Higgs pair production in the allowed parameter space and compare the results with the predictions in the SM. We find that the large enhancement of the cross section in the MSSM is mainly due to the contributions from the loops mediated by the stau, while in the NMSSM it is mainly due to the contributions from the top-squark loops. For light $m_{\tilde{\tau}_1}$ and large $\mu\tan\beta$, the production rate can be enhanced by a factor of 18 in the MSSM (relative to the SM prediction). And for a large trilinear soft breaking parameter $A_t$ and a moderately light top-squark, it can also be enhanced by a factor of 2 in the NMSSM. Moreover, we also calculate the $\chi^2$ values with the LHC Higgs data and display the results for the parameter space with $\chi^2$ better than the SM value., Comment: 14 pages, 6 figures

In light of the recent LHC Higgs search data, we investigate the pair production of a SM-like Higgs boson around 125 GeV in the MSSM and NMSSM. We first scan the parameter space of each model by considering various experimental constraints, and then calculate the Higgs pair production rate in the allowed parameter space. We find that in most cases the dominant contribution to the Higgs pair production comes from the gluon fusion process and the production rate can be greatly enhanced, maximally 10 times larger than the SM prediction (even for a TeV-scale stop the production rate can still be enhanced by a factor of 1.3). We also calculate the chi-square value with the current Higgs data and find that in the most favored parameter region the production rate is enhanced by a factor of 1.45 in the MSSM, while in the NMSSM the production rate can be enhanced or suppressed (\sigma_{SUSY}/\sigma_{SM} varies from 0.7 to 2.4)., Comment: 15 pages, 5 figures