118594751
Status of low energy SUSY models confronted with the LHC 125 GeV Higgs data
A bstractConfronted with the LHC data of a Higgs boson around 125 GeV, different models of low energy SUSY show different behaviors: some are favored, some are marginally survived and some are strongly disfavored or excluded. In this note we update our previous scan over the parameter space of various low energy SUSY models by considering the latest experimental limits like the LHCb data for Bs → μ+μ− and the XENON 100 (2012) data for dark matter-nucleon scattering. Then we confront the predicted properties of the SM-like Higgs boson in each model with the combined 7TeV and 8TeV Higgs search data ofthe LHC. For a SM-like Higgs boson around 125 GeV, we have the following observations: (i) The most favored model is the NMSSM, whose predictions about the Higgs boson can naturally (without any fine tuning) agree with the experimental data at 1σ level, better than the SM; (ii) The MSSM can fit the LHC data quite well but suffer from some extent of fine tuning; (iii) The nMSSM is excluded at 3σ level after considering all the available Higgs data; (iv) The CMSSM is quite disfavored since it is hard to give a 125 GeV Higgs boson mass and at the same time cannot enhance the di-photon signal rate.
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
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.
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.
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.
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).
117009475
Quantum effect on luminosity-redshift relation
There are many different proposals for a theory of quantum gravity. Even leaving aside the fundamental difference among theories such as the string theory and the non-perturbative quantum gravity, we are still left with many ambiguities (and/or parameters to be determined) with regard to the choice of variables, the choice of related groups, etc. Loop quantum gravity is also in such a state. It is interesting to search for experimental observables to distinguish these quantum schemes. This paper investigates the loop quantum gravity effect on luminosity-redshift relation. The quantum bounce behavior of loop quantum cosmology is found to result in multivalued correspondence in luminosity-redshift relation. And the detail multivalued behavior can tell the difference of different quantum parameters. The inverse volume quantum correction does not result in bounce behavior in this model, but affects luminosity-redshift relation also significantly.
118389942
DYNAMICAL BEHAVIOR OF INTERACTING DARK ENERGY IN LOOP QUANTUM COSMOLOGY
The dynamical behaviors of interacting dark energy in loop quantum cosmology are discussed in this paper. Based on three defined dimensionless variables, we simplify the equations of the fixed points. The fixed points for interacting dark energy can be determined by the Friedmann equation coupled with the dynamical equations in Einstein cosmology. But in loop quantum cosmology, besides the Friedmann equation, the conversation equation also gives a constrain on the fixed points. The difference of stability properties for the fixed points in loop quantum cosmology and the ones in Einstein cosmology are also discussed.
109816638
The RPC-based proposal for the ATLAS forward muon trigger upgrade in view of super-LHC
The innermost station of the present ATLAS forward muon detector needs to be upgraded for the super-LHC. We present a proposal to replace it with a sandwiched detector composed of several layers of small-radius Monitored Drift Tube chambers (sMDT) for precision tracking measurement and two stations of multi-gap Resistive Plate Chambers (mRPC) for triggering purpose. We describe the layout of the upgraded detector and the trigger strategy. Several modifications to the RPCs used in the ATLAS barrel region are needed to satisfy the super-LHC requirements. Various studies with the proposed mRPC timing resolution, spatial resolution and rate capability have been performed.
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.
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.