The topcolor-assisted technicolor model （TC2） predicts a non-universal Z′ gauge boson, which couples to the third generation fermions with enhanced strength. We study the effects of this non-universal gauge boson o...The topcolor-assisted technicolor model （TC2） predicts a non-universal Z′ gauge boson, which couples to the third generation fermions with enhanced strength. We study the effects of this non-universal gauge boson on the cross section and spin correlation of top quark pair production through the process gg → tt at the LHC. We find that the total cross section and the spin correlation can be reduced by-4.7% and -1.4% respectively in the allowed parameter space.展开更多
In the simplest little Higgs model （SLH）, we study the spin correlations in the top quark pair production at the LHC and ILC. We find that the SLH always suppresses the tt spin correlations compared to the SM values...In the simplest little Higgs model （SLH）, we study the spin correlations in the top quark pair production at the LHC and ILC. We find that the SLH always suppresses the tt spin correlations compared to the SM values. At the LHC, the suppression can be over 10% for mz, 〈 750 GeV. The SLH prediction value is outside the 1σ range of the experimental data from ATLAS, and within 1σ range of the experimental data from CMS. At the ILC, the SLH can sizably suppress the tt spin correlation for mz, approaching the center-of-mass energy √s. For example, the maximal suppression can reach -22.5%, -14.5%, and -9.5% for √s = 500 Ge V, 800 Ge V, and 1000 GeV, respectively. Therefore, the tt spin correlation at the ILC can be a sensitive probe for the SLH.展开更多
As a sister work of[Phys. Rev. D 79 （2009） 094004], we incorporate the color-screening effect due to light quark pair creation into the heavy quark-antiquark potential, and investigate the effects of screened potent...As a sister work of[Phys. Rev. D 79 （2009） 094004], we incorporate the color-screening effect due to light quark pair creation into the heavy quark-antiquark potential, and investigate the effects of screened potential on the spectrum of bottomonimn. We calculate the masses, electromagnetic decays, and E1 transitions of bottomonium states. We find that the fine splittings between χbJ （J = 0, 1, 2） states are in good agreement with experimental data, and the E1 transition rates of γ（2S） → γχbJ（1P） and γ（3S） →γχbJ（2P） （J = 0, 1, 2） all agree with data within experimental errors. In particular, the mass of γ（6S） is lowered down to match that of the γ（11020）, which is smaller than the predictions of the linear potential models by more than 100 MeV. Comparison between charmonium and bottomonium in some related problems is also discussed.展开更多
在不进行量子色动力学(quantum chromodynamics,QCD)整体分析的情况下,估算新数据对部分子分布函数(parton distribution functions,PDF)的影响,以及用更新的部分子分布函数预测其他可观测量不确定度的贡献是一项非常有用的工作。首先,...在不进行量子色动力学(quantum chromodynamics,QCD)整体分析的情况下,估算新数据对部分子分布函数(parton distribution functions,PDF)的影响,以及用更新的部分子分布函数预测其他可观测量不确定度的贡献是一项非常有用的工作。首先,用更新和优化的部分子分布函数软件ePump(error PDF updating method package)研究由CMS 8 TeV顶夸克对产生的微分散射截面(1/σ)dσ/dy_(t-t)、(1σ)dσ/dm_(t-t)、(1/σ)dσ/dy_(t)和(1/σ)dσ/dp^(t)T等实验数据对CT18NNLO胶子部分子分布函数的影响,然后,用更新后的部分子分布函数计算(1/σ)dσ/dy_(t-t)、(1/σ)dσ/dm_(t-t)、(1/σ)dσ/dy_(t)和(1/σ)dσ/dp^(t)T,并将计算所得理论值与实验值进行比较。结果表明,随着实验测量技术的发展,可获取的由顶夸克对产生的微分散射截面数据点越多,其对胶子部分子分布函数的确定作用越大。展开更多
文摘The topcolor-assisted technicolor model （TC2） predicts a non-universal Z′ gauge boson, which couples to the third generation fermions with enhanced strength. We study the effects of this non-universal gauge boson on the cross section and spin correlation of top quark pair production through the process gg → tt at the LHC. We find that the total cross section and the spin correlation can be reduced by-4.7% and -1.4% respectively in the allowed parameter space.
基金Supported by the National Natural Science Foundation of China under Grant Nos.11005089 and 11105116
文摘In the simplest little Higgs model （SLH）, we study the spin correlations in the top quark pair production at the LHC and ILC. We find that the SLH always suppresses the tt spin correlations compared to the SM values. At the LHC, the suppression can be over 10% for mz, 〈 750 GeV. The SLH prediction value is outside the 1σ range of the experimental data from ATLAS, and within 1σ range of the experimental data from CMS. At the ILC, the SLH can sizably suppress the tt spin correlation for mz, approaching the center-of-mass energy √s. For example, the maximal suppression can reach -22.5%, -14.5%, and -9.5% for √s = 500 Ge V, 800 Ge V, and 1000 GeV, respectively. Therefore, the tt spin correlation at the ILC can be a sensitive probe for the SLH.
基金Supported in part by the National Natural Science Foundation of China under Grant Nos.10675003 and 10721063the Ministry of Science and Technology of China under Grant No.2009CB825200
文摘As a sister work of[Phys. Rev. D 79 （2009） 094004], we incorporate the color-screening effect due to light quark pair creation into the heavy quark-antiquark potential, and investigate the effects of screened potential on the spectrum of bottomonimn. We calculate the masses, electromagnetic decays, and E1 transitions of bottomonium states. We find that the fine splittings between χbJ （J = 0, 1, 2） states are in good agreement with experimental data, and the E1 transition rates of γ（2S） → γχbJ（1P） and γ（3S） →γχbJ（2P） （J = 0, 1, 2） all agree with data within experimental errors. In particular, the mass of γ（6S） is lowered down to match that of the γ（11020）, which is smaller than the predictions of the linear potential models by more than 100 MeV. Comparison between charmonium and bottomonium in some related problems is also discussed.
文摘在不进行量子色动力学(quantum chromodynamics,QCD)整体分析的情况下,估算新数据对部分子分布函数(parton distribution functions,PDF)的影响,以及用更新的部分子分布函数预测其他可观测量不确定度的贡献是一项非常有用的工作。首先,用更新和优化的部分子分布函数软件ePump(error PDF updating method package)研究由CMS 8 TeV顶夸克对产生的微分散射截面(1/σ)dσ/dy_(t-t)、(1σ)dσ/dm_(t-t)、(1/σ)dσ/dy_(t)和(1/σ)dσ/dp^(t)T等实验数据对CT18NNLO胶子部分子分布函数的影响,然后,用更新后的部分子分布函数计算(1/σ)dσ/dy_(t-t)、(1/σ)dσ/dm_(t-t)、(1/σ)dσ/dy_(t)和(1/σ)dσ/dp^(t)T,并将计算所得理论值与实验值进行比较。结果表明,随着实验测量技术的发展,可获取的由顶夸克对产生的微分散射截面数据点越多,其对胶子部分子分布函数的确定作用越大。
