We study the electroweak phase transition in three scalar extension models beyond the Standard Model.Assuming new scalars are decoupled at some heavy scale, we use the covariant derivative expansion method to derive all of the dimension-6 effective operators, whose coefficients are highly correlated in a specific model. We provide bounds to the complete set of dimension-6 operators by including the electroweak precision test and recent Higgs measurements. We find that the parameter space of strong first-order phase transitions（induced by the ｜H｜~6 operator）can be probed extensively in Zh production at future electron-positron colliders.
Recently, many new dwarf spheroidal satellites（dSphs） have been discovered by the Dark Energy Survey（DES）. These dSphs are ideal candidates for probing for gamma-ray emissions from dark matter（DM） annihilation.However, no significant signature has been found by the Fermi-LAT dSph observations. In this work, we reanalyze the Fermi-LAT Pass 8 data from the direction of Reticulum II, where a slight excess has been reported by some previous studies. We treat Reticulum II（DES J0335.6-5403） as a spatially extended source, and find that no significant gamma-ray signature is observed. Based on this result, we set upper-limits on the DM annihilation cross section.
A pattern matching based tracking algorithm, named MdcPatRec, is used for the reconstruction of charged tracks in the drift chamber of the BESIII detector. This paper addresses the shortage of segment finding in the MdcPatRec algorithm. An extended segment construction scheme and the corresponding pattern dictionary are presented. Evaluation with Monte-Carlo and experimental data show that the new method can achieve higher efficiency for low transverse momentum tracks.
Gravitational waves （GW）, which were predicted by Einstein in 1916 based on the classical theory of General Relativ- ity （GR）, were recently detected by LIGO [1]. This break- through is expected to initiate a novel probe of cosmology, the nature of gravity as well as fundamental physics. In general, signals of GWs can be classified into two categories, which are waves from astro-physical and cosmological sources re- spectively. Accordingly, a number of astronomical and cos- mological experiments are under design across the world [2]. In particular, China is playing a very important role in this field by strengthening a series of fundamental scientific sub- iects, such as cosmic evolution, structure of matter,
Recently BICEP2 collaboration has announced the detection of the primordial gravitational waves at high confidence level. In light of the results of B-modes power spectrum from BICEP2 and using the based ACDM, a constraint on the tensor-to-scalar ratio r = 0.20-0.05＋0.07 （68% C.L.） can be obtained, however, this result is in apparent tension with the limit on standard inflation models from the recent PLANCK measurement, r 〈 0.11 （95% C.L.）. Herein we review the recent progress on the cosmological studies after BICEP2 and discuss on different ways of reconciling the tension between PLANCK and BICEP2 data. We will discuss possible modifications on the standard cosmological model, such as including the running of scalar spectral index or other cosmological parameters correlated with inflationary cosmological parameters, or tilting the primordial power spectrum at large scales by introducing a cut off which can be predicted by bouncing cosmology. We will also comment on another possibility of generating extra B-modes of CMB polarization, namely by a non-zero polarization rotation angle during its transferring from the last scattering surface.
LI HongLI MingZheQIU TaoTaoXIA JunQingPIAO YunSongZHANG XinMin
Using data samples collected at center-of-mass energies of √s=4.009, 4.230, 4.260, and 4.360 GeV with the BES0 detector operating at the BEPC/ collider, we perform a search for the process e＋e-→γχc,j （J =0, 1, 2） and find evidence for e＋e-→γχc1 and e＋e-→γχc2 with statistical significances of 3.0σ and 3.4σ, respectively. The Born cross sections σB（e＋e-→γχc,j）, as well as their upper limits at the 90% con dence level （C.L.） are determined at each center-of-mass energy.
Recently, a novel idea [1] has been proposed to relax the electroweak hierarchy problem through the cosmological inflation and the axion periotic potential. Here, we further assume that only the attractive inflation is needed to explain the light mass of the Higgs boson, where we do not need a specified periodic potential of the axion field. Attractive inflation during the early universe drives the Higgs boson mass from the large value in the early universe to the small value at present, where the Higgs mass is an evolving parameter of the Universe. Thus, the small Higgs mass can technically originate from the cosmological evolution rather than dynamical symmetry or anthropics. Further, we study the possible collider signals or constraints at a future lepton collier and the possible constraints from the muon anomalous magnetic moment. A concrete attractive relaxion model is also discussed, which is consistent with the data of Planck 2015.
The relative differences in coordinates of Cylindrical Gas Electron Multiplier Detector-based Inner Tracker（CGEM-IT） clusters are studied to search for track segments in CGEM-IT for the BESIII experiment.With the full simulation of single muon track samples, clear patterns are found and parameterized for the correct cluster combinations. The cluster combinations satisfying the patterns are selected as track segment candidates in CGEM-IT with an efficiency higher than 99%. The parameters of the track segments are obtained by a helix fitting.Some χ^2 quantities, evaluating the differences in track parameters between the track segments in CGEM-IT and the tracks found in the outer drift chamber, are calculated and used to match them. Proper χ^2 requirements are determined as a function of transverse momentum and the matching efficiency is found to be reasonable.
