119087977
Model Study of a Quark Star
In this paper we apply the equation of state (EOS) of QCD at finite chemical potential and zero temperature proposed in H. S. Zong and W. M. Sun [Int. J. Mod. Phys. A 23, 3591 (2008)] to the study of properties of quark star. This EOS contains only one adjustable parameter m{sub D} which sets the scale of chiral symmetry breaking (in our calculation we have chosen two values of m{sub D}: m{sub D}=244 MeV and m{sub D}=239 MeV, which is fitted from the value of f{sub {pi}} and determined by e{sup +}e{sup -} annihilation experiment, respectively). From this EOS a model of quark star is established by applying the Tolman-Oppenheimer-Volkoff equation under two conditions: with the P({mu}=0) term and without the P({mu}=0) term. Our results show clearly that the P({mu}=0) term is an important quantity in the study of quark star. A comparison between our model and other models of quark star is made. In particular, we have compared our results with the most recent observational data measured using Shapiro delay reported in P. B. Demorest et al.[Nature (London) 467, 1081 (2010)].
124327174
The Renormalized Equation of State and Quark Star
By means of the EOS of QCD at zero temperature and finite quark chemical potential we proposed [Phys. Rev. D 78(2008)054001] in the framework of rainbow-ladder approximation of Dyson-Schwinger approach, we investigate the structure of quark star and its property. It is found that the mass-radius relation in our model is very different from that of usual quark star models, but similar to neutron star models. The obtained mass of quark star is about 1.75M⊙ ~ 2.2M⊙. The obtained radius of quark star is 22 ~ 26 km, which is obviously larger than the results in other models. The reason for this discrepancy is analyzed.
53688784
Locate QCD critical end point in a continuum model study
A bstractWith a modified chemical potential dependent effective model for the gluon propagator, we try to locate the critical end point (CEP) of strongly interacting matter in the framework of Dyson-Schwinger equations (DSE). Beyond the chiral limit, we find that Nambu solution and Wigner solution could coexist in some area. Using the CornwallJackiw-Tomboulis (CJT) effective action, we show that these two phases are connected by a first order phase transition. We then locate CEP as the end point of the first order phase transition line. Meanwhile, based on CJT effective action, we give a direct calculation for the chiral susceptibility and thereby study the crossover.
120263943
Quark-meson vertices and pion properties at finite chemical potential
Based on the rainbow-ladder approximation of the Dyson-Schwinger equations and the assumption of the analyticity of the quark-meson vertex in the neighborhood of zero chemical potential ({mu}=0) and neglecting the {mu}-dependence of the dressed gluon propagator, we use the method of studying the dressed quark propagator at finite chemical potential given in [H. S. Zong, L. Chang, F.Y. Hou, W. M. Sun, and Y. X. Liu, Phys. Rev. C 71, 015205 (2005)] to show that the axial-vector quark-meson vertex at finite {mu} can be obtained from the corresponding one at {mu}=0 by a shift of variable: {gamma}{sub 5{nu}}{sup j}[{mu}](k, p)={gamma}{sub 5{nu}}{sup j}(k{approx}, p), where k and p are the relative and total momentum of the quark-antiquark pair, respectively, and k{approx}=(k-vector, k{sub 4}+i{mu}). Similar relations hold for any other type of quark-meson vertex. This feature would facilitate the numerical calculations of the quark-meson vertex function at finite {mu} considerably. Based on these results and using the dressed quark propagator at {mu}=0 proposed in [R. Alkofer, W. Detmold, C. S. Fischer, and P. Maris, Phys. Rev. D 70, 014014 (2004)], we calculate the pion decay constant f{sub {pi}} and the pion mass m{sub {pi}} at finite {mu} and a comparison of ourmore » results with those in the literature is made.« less
122208724
The calculation of quark number susceptibility at finite chemical potential and temperature
Abstract In this paper, we calculate the quark number susceptibility (QNS) at finite chemical potential μ and finite temperature T in the framework of the Dyson-Schwinger approach using the meromorphic quark propagator proposed in [Phys. Rev. D 70 , 014014 (2004)]. Analysis and discussions of the calculated result of the QNS is given.
121136055
The equation of state of QCD under hard-dense-loop approximation
Based on the method proposed by Zong et al., we calculate the equation of state (EOS) of QCD at zero temperature and finite quark chemical potential under the hard-dense-loop (HDL) approximation. A comparison between the EOS under HDL approximation and the cold, perturbative EOS of QCD proposed by Fraga, Pisarski and Schaffner-Bielich is made. It is found that when µ is less than 4.7 GeV, the pressure density calculated using HDL approximation is much larger than that calculated using perturbation theory. This enhancement of the obtained pressure density with respect to that of perturbation theory can be regarded as a possible explanation for the strong coupled QGP. It is also expected that the obtained EOS can be applied in the study of neutron stars.
118998757
Constraints on and future prospects for Two-Higgs-Doublet Models in light of the LHC Higgs signal
We analyze the Two-Higgs-Doublet Models (2HDMs) of Type I and II for consistency with the latest measurements of the ~125.5 GeV Higgs-like signal at the LHC. To this end, we perform scans of the 2HDM parameter space taking into account all relevant pre-LHC constraints as well as the most recent limits coming from searches for heavy Higgs-like states at the LHC. The current status of the 2HDMs of Type I and II is discussed assuming that the observed 125.5 GeV state is one of the two CP-even Higgs bosons, either the lighter h or the heavier H. Implications for future experiments, including expectations regarding other lighter or heavier Higgs bosons are given. The possible importance of heavier Higgs bosons feeding the signals for the 125.5 GeV state is also evaluated.
54984617
Preliminary results from the Yale microwave cavity experiment
We present the first preliminary measurements from the Yale Microwave Cavity Experiment from a search for galactic halo axion like particles at about 34 GHz. The experiment can be run in two modes, a single cavity search or a two cavity search. We give estimated sensitivities for axions and axion like particles in this experimental setup.
119226921
Two-Higgs-doublet models and enhanced rates for a 125 GeV Higgs
A bstractWe examine the level of enhancement that can be achieved in the ZZ and γγ channels for a two-Higgs-doublet model Higgs boson (either the light h or the heavy H) with mass near 125 GeV after imposing all constraints from LEP data, B physics, precision electroweak data, vacuum stability, unitarity and perturbativity. The latter constraints restrict substantially the possibilities for enhancing the gg → h → γγ or gg → H → γγ signal relative to that for the SM Higgs, hSM. Further, we find that a large enhancement of the gg → h → γγ or gg → H → γγ signal in Type II models is possible only if the gg → h → ZZ or gg → H → ZZ mode is even more enhanced, a situation disfavored by current data. In contrast, in the Type I model one can achieve enhanced rates in the γγ final state for the h while having the ZZ mode at or below the SM rate — the largest [gg → h → γγ]/[gg → hSMγγ] ratio found is of order ~ 1.3 when the two Higgs doublet vacuum expectation ratio is tan β = 4 or 20 and the charged Higgs boson has its minimal LEP-allowed value of mH± = 90 GeV.
119275366
125 GeV Higgs bosons in two-Higgs-doublet models
Moriond 2013 ALTAS data at 125 GeV state appears to exhibit a substantial excess in the di-photon final state and in the ZZ decaying to four lepton channel, whereas which are more or less SM-like rate observed by CMS MVA analysis. We examine the maximum Higgs signal enhancements that can be achieved in the 2HDM when either a single Higgs or more than one Higgs have mass(es) near 125 GeV. In general, the constraints of vacuum stability, unitarity and perturbativity play the key role in restricting possibilities of signal enhancement. The Type II model allows for an enhancement in the di-photon rate (relative to the SM) of the order of 2-3 but associated with an even larger ZZ or too large \tau\tau signal. In contrast, the maximal value of the di-photon signal in the Type I model can reach the order of 1.3 for which the ZZ signal is of order 1.
125774679
The supersymmetric quantum effects at gamma gamma colliders