2019 Vol. 43, No. 4

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Constraining the anomalous Higgs boson coupling in ${\bf H+\gamma} $ production
Liaoshan Shi, Zhijun Liang, Bo Liu, Zhenhui He
2019, 43(4): 043001. doi: 10.1088/1674-1137/43/4/043001
Higgs boson production in association with a photon (H+\begin{document}$ \gamma $\end{document}) offers a promising channel to test the Higgs boson to photon coupling at various energy scales. Its potential sensitivity to anomalous couplings of the Higgs boson has not been explored with the proton-proton collision data. In this paper, we reinterpret the latest ATLAS H+\begin{document}$ \gamma $\end{document} resonance search results within the Standard Model effective field theory (EFT) framework, using 36.1 fb−1 of proton-proton collision data recorded with the ATLAS detector at \begin{document}$ \sqrt{s}=13 $\end{document} TeV. Constraints on the Wilson coefficients of dimension-six EFT operators related to the Higgs boson to photon coupling are provided for the first time in the H+\begin{document}$ \gamma $\end{document} final state at the LHC.
Precision Higgs physics at the CEPC
Fenfen An, Yu Bai, Chunhui Chen, Xin Chen, Zhenxing Chen, Joao Guimaraes da Costa, Zhenwei Cui, Yaquan Fang, Chengdong Fu, Jun Gao, Yanyan Gao, Yuanning Gao, Shaofeng Ge, Jiayin Gu, Fangyi Guo, Jun Guo, Tao Han, Shuang Han, Hongjian He, Xianke He, Xiaogang He, Jifeng Hu, Shih-Chieh Hsu, Shan Jin, Maoqiang Jing, Susmita Jyotishmati, , Chia-Ming Kuo, Peizhu Lai, Boyang Li, Congqiao Li, Gang Li, Haifeng Li, Liang Li, Shu Li, Tong Li, Qiang Li, Hao Liang, Zhijun Liang, Libo Liao, Bo Liu, Jianbei Liu, Tao Liu, Zhen Liu, Xinchou Lou, Lianliang Ma, Bruce Mellado, Xin Mo, Mila Pandurovic, Jianming Qian, Zhuoni Qian, Nikolaos Rompotis, Manqi Ruan, Alex Schuy, Lianyou Shan, Jingyuan Shi, Xin Shi, Shufang Su, Dayong Wang, Jin Wang, Liantao Wang, Yifang Wang, Yuqian Wei, Yue Xu, Haijun Yang, Ying Yang, Weiming Yao, Dan Yu, Kaili Zhang, Zhaoru Zhang, Mingrui Zhao, Xianghu Zhao, Ning Zhou
2019, 43(4): 043002. doi: 10.1088/1674-1137/43/4/043002
The discovery of the Higgs boson with its mass around 125 GeV by the ATLAS and CMS Collaborations marked the beginning of a new era in high energy physics. The Higgs boson will be the subject of extensive studies of the ongoing LHC program. At the same time, lepton collider based Higgs factories have been proposed as a possible next step beyond the LHC, with its main goal to precisely measure the properties of the Higgs boson and probe potential new physics associated with the Higgs boson. The Circular Electron Positron Collider (CEPC) is one of such proposed Higgs factories. The CEPC is an e+e circular collider proposed by and to be hosted in China. Located in a tunnel of approximately 100 km in circumference, it will operate at a center-of-mass energy of 240 GeV as the Higgs factory. In this paper, we present the first estimates on the precision of the Higgs boson property measurements achievable at the CEPC and discuss implications of these measurements.
LFV decays of Z boson in Minimal R-symmetric Supersymmetric Standard Model
Ke-Sheng Sun, Jian-Bin Chen, Xiu-Yi Yang, Sheng-Kai Cui
2019, 43(4): 043101. doi: 10.1088/1674-1137/43/4/043101
A future Z-factory will offer the possibility of studying rare Z decays \begin{document}$ Z\rightarrow l_1l_2 $\end{document}, such as those leading to lepton flavor violation (LFV) final states. In this work, by considering the constraints from radiative two-body decays \begin{document}$ l_2\rightarrow l_1\gamma $\end{document}, we investigate the LFV decays \begin{document}$ Z\rightarrow l_1l_2 $\end{document} in the framework of the Minimal R-symmetric Supersymmetric Standard Model with two benchmark points from the existing literature. The flavor-violating off-diagonal entries \begin{document}$ \delta^{12} $\end{document}, \begin{document}$ \delta^{13} $\end{document} and \begin{document}$ \delta^{23} $\end{document} are constrained by the current experimental bounds of \begin{document}$ l_2\rightarrow l_1\gamma $\end{document}. Considering recent experimental constraints, we also investigate Br(\begin{document}$ Z\rightarrow l_1l_2 $\end{document}) as a function of \begin{document}$ M_D^W $\end{document}. The numerical results show that the theoretical predictions of Br(\begin{document}$ Z\rightarrow l_1l_2 $\end{document}) in the MRSSM are several orders of magnitude below the current experimental bounds. The LFV decays \begin{document}$ Z\rightarrow e\tau $\end{document} and \begin{document}$ Z\rightarrow \mu\tau $\end{document} may be promising observation targets in future experiments.
Angular distribution coefficients of Z (W) boson produced in ${{e^+e^-}} $ collisions at ${{\sqrt{s}=240}} $ GeV
Yu-Dong Wang, Jian-Xiong Wang
2019, 43(4): 043102. doi: 10.1088/1674-1137/43/4/043102
At the designed circular electron-positron collider (CEPC), similar to the hadron collider, the angular distribution coefficients of the decay lepton pair from the produced Z(W) boson in \begin{document}$ e^+ e^- $\end{document} collisions are predicted. Their dependence on cos\begin{document}$ \theta_Z $\end{document} (cos\begin{document}$ \theta_W $\end{document}) are presented in four different polarization frames. Furthermore, the value of the angular distribution coefficients in different bins of cos\begin{document}$ \theta_Z $\end{document} are presented in the C-S frame. In comparison with the case at the hadron collider, better accurate measurement for Z(W) is expected because there is less background, and W could be reconstructed from its leptonic decay channel. This works provides a method to precisely test the electroweak production mechanism or some effect induced from new physics in the future measurements at the CEPC.
Effective field theory of the Majorana dark matter
Hua-Yong Han, Hong-Yan Wu, Si-Bo Zheng
2019, 43(4): 043103. doi: 10.1088/1674-1137/43/4/043103
We revisit the thermal Majorana dark matter from the viewpoint of the minimal effective field theory. In this framework, analytical results for dark matter annihilation into Standard Model particles are derived. The dark matter parameter space, subject to the latest LUX, PandaX-II and Xenon-1T limits, is presented in a model-independent way. Applications to the singlet-doublet and MSSM are presented.
Global constraints from RHIC and LHC on transport properties of QCD fluids in CUJET/CIBJET framework
Shuzhe Shi, Jinfeng Liao, Miklos Gyulassy
2019, 43(4): 044101. doi: 10.1088/1674-1137/43/4/044101
We report results of a comprehensive global \begin{document}$ \chi^2 $\end{document} analysis of nuclear collision data from RHIC (0.2 ATeV), LHC1 (2.76 ATeV), and recent LHC2 (5.02 ATeV) energies using the updated CUJET framework. The framework consistently combines viscous hydrodynamic fields predicted by VISHNU2+1 (validated with soft \begin{document}$ p_T<2 $\end{document} GeV bulk observables) and the DGLV theory of jet elastic and inelastic energy loss generalized to QGP fluids with an sQGMP color structure, including effective semi-QGP color electric quark and gluon as well as emergent color magnetic monopole degrees of freedom constrained by lattice QCD data. We vary the two control parameters of the model (the maximum value of the running QCD coupling, \begin{document}$ \alpha_c $\end{document}, and the ratio \begin{document}$ c_m $\end{document} of color magnetic to electric screening scales) and calculate the global \begin{document}$ \chi^2(\alpha_c,c_m) $\end{document} compared with available jet fragment observables (\begin{document}$ R_{{\rm AA}}, v_2 $\end{document}). A global \begin{document}$ \chi^2<2 $\end{document} minimum is found with \begin{document}$ \alpha_c \approx 0.9\pm 0.1 $\end{document} and \begin{document}$ c_m\approx 0.25\pm 0.03 $\end{document}. Using CIBJET, the event-by-event (ebe) generalization of the CUJET framework, we show that ebe fluctuations in the initial conditions do not significantly alter our conclusions (except for \begin{document}$ v_3 $\end{document}). An important theoretical advantage of the CUJET and CIBJET frameworks is not only its global \begin{document}$ \chi^2 $\end{document} consistency with jet fragment observables at RHIC and LHC and with non-perturbative lattice QCD data, but also its internal consistency of the constrained jet transport coefficient, \begin{document}$ \hat{q}(E,T)/T^3 $\end{document}, with the near-perfect fluid viscosity to entropy ratio (\begin{document}$ \eta/s \sim T^3/\hat{q}\sim 0.1-0.2 $\end{document}) property of QCD fluids near \begin{document}$ T_c $\end{document} needed to account for the low \begin{document}$ p_T<2 $\end{document} GeV flow observables. Predictions for future tests at LHC with 5.44 ATeV Xe + Xe and 5.02 ATeV Pb + Pb are also presented.
Proton emission from the drip-line nuclei I-Bi using the WKB approximation with relativistic mean-field densities
T. Sahoo, R. N. Panda, S. K. Patra
2019, 43(4): 044102. doi: 10.1088/1674-1137/43/4/044102
We study the properties of proton rich nuclei reported as proton emitters in the region from I to Bi with Z = 53 to 83 and N = 56 to 102 as a crucial application to the existence of exotic nuclei. The effective relativistic mean-field formalism (E-RMF), with NL3, FSUGarnet, G3 and IOPB-I interactions, is adopted for analysis of the ground state properties of proton emitters. Furthermore, in the E-RMF background, the Wentzel-Karmers-Brillouin (WKB) barrier penetration method is used for the calculation of proton emission half-lives. It is found that the calculated half-lives are in good agreement with the experimental results for all emitters considered in this study.
In-medium nucleon-nucleon elastic cross-sections determined from the nucleon induced reaction cross-section data
Li Ou, Xue-ying He
2019, 43(4): 044103. doi: 10.1088/1674-1137/43/4/044103
Within the framework of the improved quantum molecular dynamics model, the medium modifications of the free nucleon-nucleon elastic cross-sections are investigated. By using various in-medium nucleon-nucleon elastic cross-sections in the model, the nucleon induced reactions on various targets are simulated, and the excitation functions of reaction cross-sections in the energy range from 25 MeV to 1 GeV are calculated. By comparing the calculations with the experimental data, the isospin, density, and momentum dependence of the medium correction factors of free nucleon-nucleon elastic cross-sections are determined.
Probing cold nuclear matter effects with the productions of isolated-${\gamma} $ and ${\gamma} $+jet in p+Pb collisions at ${\sqrt{{s}_{{NN}}}}= $ 8.16 TeV
Guo-Yang Ma, Wei Dai, Ben-Wei Zhang
2019, 43(4): 044104. doi: 10.1088/1674-1137/43/4/044104
We investigate cold nuclear matter (CNM) effects on the productions of isolated prompt photons and \begin{document}$ \gamma+ $\end{document}jet in proton-lead collisions at \begin{document}$ \rm 8.16 $\end{document} TeV under next-to-leading order perturbative quantum chromodynamics calculations with four parameterizations for nuclear parton distribution functions (nPDFs), i.e., DSSZ, EPPS16, nCTEQ15, and nIMParton. Our theoretical calculations provide good descriptions of the pp baseline in the ATLAS collaboration and make predictions for future experimental results at \begin{document}$ \rm p $\end{document}+\begin{document}$ \rm Pb $\end{document} collisions. We calculate the dependence of the nuclear modification factor of isolated prompt photons on transverse momentum \begin{document}$ p_{\rm T}^{\gamma} $\end{document} and pseudo-rapidity \begin{document}$ \eta^{\gamma} $\end{document} at very forward and backward rapidity regions, and we demonstrate that the forward-to-backward yield asymmetries \begin{document}$ Y_{\rm pPb}^{\rm asym} $\end{document} as a function of \begin{document}$ p_{\rm T}^{\gamma} $\end{document} with different nPDF parameterizations have diverse behaviors. Furthermore, the nuclear modification factor of isolated-\begin{document}$ \gamma+ $\end{document}jet \begin{document}$ R_{\rm pPb}^{\gamma\rm Jet} $\end{document} as a function of \begin{document}$ \gamma+ $\end{document}jet's pseudo-rapidity \begin{document}$ \eta_{\gamma \rm Jet}=\displaystyle\frac{1}{2}(\eta_{\gamma}+\eta_{\rm Jet}) $\end{document} at different average transverse momenta \begin{document}$ p_{\rm T}^{\rm avg}=\displaystyle\frac{1}{2}(p_{\rm T}^{\gamma}+ p_{\rm T}^{\rm Jet}) $\end{document} has been discussed. This can facilitate a tomographic study of CNM effects with precise locations in a rather wide kinematic region by varying the transverse momenta and rapidities of both isolated photons and jets in p+A collisions.
Basic characteristics of nuclear landscape by improved Weizsäcker-Skyrme-type nuclear mass model
Na-Na Ma, Hai-Fei Zhang, Xiao-Jun Bao, Hong-Fei Zhang
2019, 43(4): 044105. doi: 10.1088/1674-1137/43/4/044105
Atomic Mass Evaluation (AME2016) has replenished the latest nuclear binding energy data. Other physical observables, such as the separated energies, decay energies, and the pairing gaps, were evaluated based on the new mass table. An improved Weizsäcker-Skyrme-type (WS-type) nuclear mass model with only 13 parameters was presented, including the correction from two combinatorial radial basis functions (RBFs), where shell and pairing effects are simultaneously dealt with using a Strutinsky-like method. The RBFs code had 2267 updated experimental binding energies as inputs, and their correspondent root-mean square (rms) deviations dropped to 149 keV. For the training of other mass models by RBFs correction, rms deviations are clustered between 100 keV to 200 keV. Compared with other experimental quantities, the rms deviations calculated within the improved WS-type model falls between 100 keV and 250 keV. We extrapolate the binding energies to 12435 nuclei, which covers the ranges \begin{document}$ 8\leqslant Z\leqslant128 $\end{document} and \begin{document}$ 8\leqslant N\leqslant251 $\end{document} in the framework of the WS-type model with RBFs correction. Simultaneously, the ground state deformations \begin{document}$ \beta_{2, \; 4, \; 6} $\end{document} and all parts in the WS-type mass formula are presented in this paper. Finally, we tabulated all calculated characteristics within the improved formula and linked them to https://github.com/lukeronger/NuclearData-LZU: nuclear binding energies, one-nucleon and two-nucleon separation energies (\begin{document}$ S_{\rm{n, \; p, \; 2n, \; 2p}} $\end{document}), \begin{document}$ \alpha $\end{document} and \begin{document}$ \beta $\end{document}-decay energies (\begin{document}$ Q_{\alpha} $\end{document} and \begin{document}$ Q_{\rm{\beta^-, \; \beta^+, \; EC}} $\end{document}), and the pairing gap \begin{document}$ \Delta_{\rm{n}} $\end{document} and \begin{document}$ \Delta_{\rm{p}} $\end{document}.
Dark matter, neutrino mass, cutoff for cosmic-ray neutrino, and the Higgs boson invisible decay from a neutrino portal interaction
Wen Yin
2019, 43(4): 045101. doi: 10.1088/1674-1137/43/4/045101
We study an effective theory beyond the standard model (SM) where either of the two additional gauge singlets, a Majorana fermion and a real scalar, constitutes all or some fraction of dark matter. In particular, we focus on the masses of the two singlets in the range of \begin{document}$ {\cal{O}} $\end{document}(10) MeV-\begin{document}$ {\cal{O}} $\end{document}(10) GeV with a neutrino portal interaction, which plays an important role not only in particle physics but also in cosmology and astronomy. We point out that the thermal dark matter abundance can be explained by (co-)annihilation, where the dark matter with a mass greater than 2 GeV can be tested in future lepton colliders, CEPC, ILC, FCC-ee and CLIC, in the light of the Higgs boson invisible decay. When the gauge singlets are lighter than \begin{document}$ {\cal{O}} $\end{document}(100) MeV, the interaction can affect the neutrino propagation in the universe due to its annihilation with cosmic background neutrino into the gauge singlets. Although in this case it can not be the dominant dark matter, the singlets are produced by the invisible decay of the Higgs boson at such a rate which is fully within reach of future lepton colliders. In particular, a high energy cutoff of cosmic-ray neutrino, which may account for the non-detection of Greisen-Zatsepin-Kuzmin (GZK) neutrino or the non-observation of the Glashow resonance, can be set. Interestingly, given the cutoff and the mass (range) of WIMPs, a neutrino mass can be " measured” kinematically.