Minimal Dilaton Model Research Articles

95 GeV light Higgs in the top-pair-associated diphoton channel at the LHC in the minimal dilaton model* *Supported by the National Natural Science Foundation of China (12275066, 11605123)

Motivated by experimental hints and theoretical frameworks indicating the existence of an extended Higgs sector, we explore the feasibility of detecting a 95 GeV light Higgs boson decaying into a diphoton within the minimal dilaton model at the 14 TeV LHC. Initially, we identify the correlations between the production cross section, decay branching ratios, and model parameters, e.g., the scalar mixing angle . Subsequently, we utilize Monte Carlo simulations to generate the signal of the light Higgs boson via the process, along with the corresponding backgrounds. To effectively separate the signal from the dominant backgrounds , we employ a meticulous cut-based selection process. Ultimately, we find that with an integrated luminosity of , the regions of can be covered over the level.

A light scalar in the Minimal Dilaton Model in light of the LHC constraints * * Supported by the National Natural Science Foundation of China (NNSFC)(11605123, 11547103, 11674253, 11547310), the China Scholarship Council (CSC) (201706275160) and the US National Science Foundation (NSF) (PHY-0855561)

Whether an additional light scalar exists is an interesting topic in particle physics beyond the Standard Model (SM), as we do not know as yet the nature of physics beyond the SM in the low mass region in view of the inconsistent results of the ATLAS and CMS collaborations in their search for light resonances around 95 GeV in the diphoton channel. We study a light scalar in the Minimal Dilaton Model (MDM). Under the theoretical and the latest experimental constraints, we sort the selected data samples into two scenarios according to the diphoton rate of the light scalar: the large-diphoton scenario (with ) and the small-diphoton scenario (with ), which are favored by the CMS and ATLAS results, respectively. We compare the two scenarios, test the characteristics of the model parameters, the scalar couplings, production and decay, and consider how they could be further discerned at colliders. We draw the following conclusions for the two scenarios: (i) The large-diphoton scenario has in general a small Higgs-dilaton mixing angle ( ) and a small dilaton vacuum expectation value (VEV) ( ), and the small-diphoton scenario has large mixing ( ) or large VEV ( ). (ii) The large-diphoton scenario in general predicts small coupling ( ) and large coupling ( ), while the small-diphoton scenario predicts small coupling ( ). (iii) The large-diphoton scenario can interpret the small diphoton excess seen by CMS at its central value, when GeV, and . (iv) The large-diphoton scenario in general predicts a negative correlation between the Higgs couplings and , while the small-diphoton scenario predicts that both couplings are smaller than 1, or .

Minimal dilaton model and the diphoton excess

In light of the recent 750 GeV diphoton excesses reported by the ATLAS and CMS collaborations, we investigate the possibility of explaining this excess using the Minimal Dilaton Model. We find that this model is able to explain the observed excess with the presence of additional top partner(s), with same charge as the top quark, but with mass in the TeV region. First, we constrain model parameters using in addition to the 750 GeV diphoton signal strength, precision electroweak tests, single top production measurements, as well as Higgs signal strength data collected in the earlier runs of the LHC. In addition we discuss interesting phenomenolgy that could arise in this model, relevant for future runs of the LHC.

Interpreting the 750 GeV diphoton excess in the minimal dilaton model

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.

Radiative Corrections to e+e− → Zh at Future Higgs Factory in the Minimal Dilaton Model

The minimal dilaton model (MDM) extends the Standard Model by one singlet scalar called dilaton and one top quark partner called t′. In this work we investigate the t′-induced radiative correction to the Higgs-strahlung production process e+e− → Zh at future Higgs factory. We first present the analytical calculations in detail and show how to handle the ultraviolet divergence. Then we calculate the correction numerically by considering the constraints from precision electroweak data. We find that, for sinθL = 0.2 and mt′ = 1200 GeV, the correction is 0.26% and 2.1% for , 1 TeV respectively, and a larger value can be achieved as sin θL increases.

Higgs-strahlung production process e + e − → Zh at the future Higgs factory in the Minimal Dilaton Model

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\%.

Higgs phenomenology in the Minimal Dilaton Model after Run I of the LHC

The Minimal Dilaton Model (MDM) extends the Standard Model (SM) by a singlet scalar, which can be viewed as a linear realization of general dilaton field. This new scalar field mixes with the SM Higgs field to form two mass eigenstates with one of them corresponding to the 125 GeV SM-like Higgs boson reported by the LHC experiments. In this work, under various theoretical and experimental constrains, we perform fits to the latest Higgs data and then investigate the phenomenology of Higgs boson in both the heavy dilaton scenario and the light dilaton scenario of the MDM. We find that: (i) If one considers the ATLAS and CMS data separately, the MDM can explain each of them well, but refer to different parameter space due to the apparent difference in the two sets of data. If one considers the combined data of the LHC and Tevatron, however, the explanation given by the MDM is not much better than the SM, and the dilaton component in the 125-GeV Higgs is less than about 20% at 2 sigma level. (ii) The current Higgs data have stronger constrains on the light dilaton scenario than on the heavy dilaton scenario. (iii) The heavy dilaton scenario can produce a Higgs triple self coupling much larger than the SM value, and thus a significantly enhanced Higgs pair cross section at hadron colliders. With a luminosity of 100 fb^{-1} (10 fb^{-1}) at the 14-TeV LHC, a heavy dilaton of 400 GeV (500 GeV) can be examined. (iv) In the light dilaton scenario, the Higgs exotic branching ratio can reach 43% (60%) at 2 sigma (3 sigma) level when considering only the CMS data, which may be detected at the 14-TeV LHC with a luminosity of 300 fb^{-1} and the Higgs Factory.

Minimal dilaton model

Both the ATLAS and CMS experiments at the LHC have reported the observation of the particle of mass around 125 GeV which is consistent to the Standard Model (SM) Higgs boson, but with an excess of events beyond the SM expectation in the diphoton decay channel at each of them. There still remains room for a logical possibility that we are not seeing the SM Higgs but something else. Here we introduce the minimal dilaton model in which the LHC signals are explained by an extra singlet scalar of the mass around 125 GeV that slightly mixes with the SM Higgs heavier than 600 GeV. When this scalar has a vacuum expectation value well beyond the electroweak scale, it can be identified as a linearly realized version of a dilaton field. Though the current experimental constraints from the Higgs search disfavors such a region, the singlet scalar model itself still provides a viable alternative to the SM Higgs in interpreting its search results.