119294466
Little Higgs theory confronted with the LHC Higgs data
We confront the little Higgs theory with the LHC Higgs search data (up to 17 fb(-1) of the combined 7 and 8 TeV run). Considering some typical models, namely, the littlest Higgs model, the littlest Higgs model with T parity (LHT-A and LHT-B), and the simplest little Higgs model, we scan over the parameter space in the region allowed by current experiments. We find that in these models the inclusive and exclusive (via gluon-gluon fusion) diphoton and ZZ* signal rates of the Higgs boson are always suppressed and approach the standard model predictions for a large-scale f. Thus, the ZZ* signal rate is within the 1 sigma range of the experimental data while the inclusive diphoton signal rate is always outside the 2 sigma range. Especially, in the LHT-A the diphoton signal rate is outside the 3 sigma range of the experimental data for f < 800 GeV. We also perform a global chi(2) fit to the available LHC and Tevatron Higgs data, and find that these models provide no better global fit to the whole data set (only for some special channels a better fit can be obtained, especially in the LHT-B). DOI: 10.1103/PhysRevD.87.055004
118462765
Dark matter in the little Higgs model under current experimental constraints from the LHC, Planck, and Xenon data
We examine the status of dark matter (heavy photon) in the littlest Higgs model with T parity (LHT) in light of the new results from the LHC Higgs search, the Planck dark matter relic density, and the XENON100 limit on the dark matter scattering off the nucleon. We obtain the following observations: (i) For the LHC Higgs data, the LHT can well be consistent with the CMS results but disfavored by the ATLAS observation of diphoton enhancement; (ii) for the dark matter relic density, the heavy photon in the LHT can account for the Planck data for the small mass splitting of mirror lepton and heavy photon; (iii) for the dark matter scattering off the nucleon, the heavy photon can give a spin-independent cross section below the XENON100 upper limit for m(AH) > 95 GeV (f > 665 GeV); (iv) a fit using the CMS Higgs data gives the lowest chi square of 2.63 (the standard model value is 4.75) at f similar or equal to 1120 GeV and m(AH) similar or equal to 170 GeV (at this point, the dark matter constraints from Planck and XENON100 can also be satisfied). Such a best point and its nearby favored region (even for an f value up to 3.8 TeV) can be covered by the future XENON1T (2017) experiment.
118505781
A SM-like Higgs near 125 GeV in low energy SUSY: a comparative study for MSSM and NMSSM
A bstractMotivated by the recent LHC hints of a Higgs boson around 125 GeV, we assume a SM-like Higgs with the mass 123-127 GeV and study its implication in low energy SUSY by comparing the MSSM and NMSSM. We consider various experimental constraints at 2σ level (including the muon g − 2 and the dark matter relic density) and perform a comprehensive scan over the parameter space of each model. Then in the parameter space which is allowed by current experimental constraints and also predicts a SM-like Higgs in 123-127 GeV, we examine the properties of the sensitive parameters (like the top squark mass and the trilinear coupling At) and calculate the rates of the di-photon signal and the V V* (V = W, Z) signals at the LHC. Our typical findings are: (i) In the MSSM the top squark and At must be large and thus incur some fine-tuning, which can be much ameliorated in the NMSSM; (ii) In the MSSM a light stau is needed to enhance the di- photon rate of the SM-like Higgs to exceed its SM prediction, while in the NMSSM the di-photon rate can be readily enhanced in several ways; (iii) In the MSSM the signal rates of pp → h → V V* at the LHC are never enhanced compared with their SM predictions, while in the NMSSM they may get enhanced significantly; (iv) A large part of the parameter space so far survived will be soon covered by the expected XENON100(2012) sensitivity (especially for the NMSSM).
53520209
Pair production of 125 GeV Higgs boson in the SM extension with color-octet scalars at the LHC
A bstractAlthough 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 experimental 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 103 times prediction in the SM. (ii) Moreover, the sizable enhancement comes from the contributions of the CP-odd color-octet scalar $ S_I^A $. For lighter scalar $ S_I^A $ and larger values of |λI|, 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.
118371318
The SM extension with color-octet scalars: diphoton enhancement and global fit of LHC Higgs data
A bstractIn light of the significant progress of the LHC to determine the properties of the Higgs boson, we investigate the capability of the Manohar-Wise model in explaining the Higgs data. This model extends the SM by one family of color-octet and isospin-doublet scalars, and it can sizably alter the coupling strengths of the Higgs boson with gluons and photons. We first examine the current constraints on the model, which are from unitarity, the LHC searches for the scalars and the electroweak precision data (EWPD). In implementing the unitarity constraint, we use the properties of the SU(3) group to simplify the calculation. Then in the allowed parameter space we perform a fit of the model, using the latest ATLAS and CMS data, respectively. We find that the Manohar-Wise model is able to explain the data with χ2 significantly smaller than the SM value. We also find that the current Higgs data, especially the ATLAS data, are very powerful in further constraining the parameter space of the model. In particular, in order to explain the γγ enhancement reported by the ATLAS collaboration, the sign of the hgg coupling is usually opposite to that in the SM.
118683449
Higgs phenomenology in the Minimal Dilaton Model after Run I of the LHC
A bstractThe 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 2σ 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 2σ (3σ) 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.
118012906
Electroweak and QCD Results from the Tevatron
The Tevatron collider has been remarkably successful and has so far delivered more than 11 fb{sup -1} of data to both the CDF and D0 experiments. Though the LHC has replaced the Tevatron as the world's most powerful collider, years of detector calibration, the huge size of the dataset and the nature of pp collisions will keep the Tevatron competitive in many selected topics in the near future. More than 10 fb{sup -1} of data has been collected by each experiment. Good understanding of the detector performance has been demonstrated by the high precision W boson mass ({Delta}M{sub W} = 31 MeV) and top quark mass ({Delta}M{sub t} = 1.06 GeV) measurements. We report the latest electroweak and QCD results from both experiments. Most analyses presented here used 4-6 fb{sup -1} of data.
120210800
Hawking radiation and black hole entropy in a gravity’s rainbow
In the context of gravity’s rainbow, Planck scale correction on Hawking radiation and black hole entropy in Parikh and Wilczk’s tunneling framework is studied. We calculate the tunneling probability of massless particles in the modified Schwarzschild black holes from gravity’s rainbow. In the tunneling process, when a particle gets across the horizon, the metric fluctuation must be taken into account, not only due to energy conservation but also to spacetime Planck scale effect. Our results show that the emission rate is related to changes of the black hole’s quantum corrected entropies before and after the emission. In the same time, for the modified black holes, a series of correction terms including a logarithmic term to Bekenstein–Hawking entropy are obtained. Correspondingly, the spectrum of Planck scale corrected emission is obtained and it deviates from the thermal spectrum. In addition, a specific form of modified dispersion relation is proposed and applied.
118675674
THE DYNAMICS OF TACHYON FIELD WITH AN INVERSE SQUARE POTENTIAL IN LOOP QUANTUM COSMOLOGY
The dynamical behavior of tachyon field with an inverse potential is investigated in loop quantum cosmology. It reveals that the late-time behavior of tachyon field with this potential leads to a power-law expansion. In addition, an additional barotropic perfect fluid with the adiabatic index 0 < γ < 2 is added and the dynamical system is shown to be an autonomous one. The stability of this autonomous system is discussed using phase plane analysis. There exist up to five fixed points with only two of them possibly stable. The two stable node (attractor) solutions are specified and their cosmological indications are discussed. For the tachyon dominated solution, the further discussion is stretched to the possibility of considering tachyon field as a combination of two parts which respectively behave like dark matter and dark energy.
124126688
A dynamical evolution model on the quantum Black Hole
16593749
Recent Electroweak Results from the Tevatron
W and Z bosons are mainly produced via quark-antiquark annihilations at the Fermilab Tevatron collider. Precision measurements with these gauge bosons provide us with high precision tests of the Standard Model (SM) as well as indirect search for possible new physics beyond the SM. I present the recent electroweak measurements related to single W, Z boson and diboson productions from the CDF and D0 experiments at the Fermilab Tevatron collider.