Chinese Physics C

Antineutrino energy spectrum unfolding based on the Daya Bay measurement and its applications

F. P. An, A. B. Balantekin, M. Bishai, S. Blyth, G. F. Cao, J. Cao, J. F. Chang, Y. Chang, H. S. Chen, S. M. Chen, Y. Chen, Y. X. Chen, J. Cheng, Z. K. Cheng, J. J. Cherwinka, M. C. Chu, J. P. Cummings, O. Dalager, F. S. Deng, Y. Y. Ding, M. V. Diwan, T. Dohnal, D. Dolzhikov, J. Dove, M. Dvořák, D. A. Dwyer, J. P. Gallo, M. Gonchar, G. H. Gong, H. Gong, M. Grassi, W. Q. Gu, J. Y. Guo, L. Guo, X. H. Guo, Y. H. Guo, Z. Guo, R. W. Hackenburg, S. Hans, M. He, K. M. Heeger, Y. K. Heng, Y. K. Hor, Y. B. Hsiung, B. Z. Hu, J. R. Hu, T. Hu, Z. J. Hu, H. X. Huang, J. H. Huang, X. T. Huang, Y. B. Huang, P. Huber, D. E. Jaffe, K. L. Jen, X. L. Ji, X. P. Ji, R. A. Johnson, D. Jones, L. Kang, S. H. Kettell, S. Kohn, M. Kramer, T. J. Langford, J. Lee, J. H. C. Lee, R. T. Lei, R. Leitner, J. K. C. Leung, F. Li, H. L. Li, J. J. Li, Q. J. Li, R. H. Li, S. Li, S. C. Li, W. D. Li, X. N. Li, X. Q. Li, Y. F. Li, Z. B. Li, H. Liang, C. J. Lin, G. L. Lin, S. Lin, J. J. Ling, J. M. Link, L. Littenberg, B. R. Littlejohn, J. C. Liu,

2021, 45(7): 073001. doi: 10.1088/1674-1137/abfc38

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Abstract:
The prediction of reactor antineutrino spectra will play a crucial role as reactor experiments enter the precision era. The positron energy spectrum of 3.5 million antineutrino inverse beta decay reactions observed by the Daya Bay experiment, in combination with the fission rates of fissile isotopes in the reactor, is used to extract the positron energy spectra resulting from the fission of specific isotopes. This information can be used to produce a precise, data-based prediction of the antineutrino energy spectrum in other reactor antineutrino experiments with different fission fractions than Daya Bay. The positron energy spectra are unfolded to obtain the antineutrino energy spectra by removing the contribution from detector response with the Wiener-SVD unfolding method. Consistent results are obtained with other unfolding methods. A technique to construct a data-based prediction of the reactor antineutrino energy spectrum is proposed and investigated. Given the reactor fission fractions, the technique can predict the energy spectrum to a 2% precision. In addition, we illustrate how to perform a rigorous comparison between the unfolded antineutrino spectrum and a theoretical model prediction that avoids the input model bias of the unfolding method.

F. P. An, A. B. Balantekin, M. Bishai, S. Blyth, G. F. Cao, J. Cao, J. F. Chang, Y. Chang, H. S. Chen, S. M. Chen, Y. Chen, Y. X. Chen, J. Cheng, Z. K. Cheng, J. J. Cherwinka, M. C. Chu, J. P. Cummings, O. Dalager, F. S. Deng, Y. Y. Ding, M. V. Diwan, T. Dohnal, D. Dolzhikov, J. Dove, M. Dvořák, D. A. Dwyer, J. P. Gallo, M. Gonchar, G. H. Gong, H. Gong, M. Grassi, W. Q. Gu, J. Y. Guo, L. Guo, X. H. Guo, Y. H. Guo, Z. Guo, R. W. Hackenburg, S. Hans, M. He, K. M. Heeger, Y. K. Heng, Y. K. Hor, Y. B. Hsiung, B. Z. Hu, J. R. Hu, T. Hu, Z. J. Hu, H. X. Huang, J. H. Huang, X. T. Huang, Y. B. Huang, P. Huber, D. E. Jaffe, K. L. Jen, X. L. Ji, X. P. Ji, R. A. Johnson, D. Jones, L. Kang, S. H. Kettell, S. Kohn, M. Kramer, T. J. Langford, J. Lee, J. H. C. Lee, R. T. Lei, R. Leitner, J. K. C. Leung, F. Li, H. L. Li, J. J. Li, Q. J. Li, R. H. Li, S. Li, S. C. Li, W. D. Li, X. N. Li, X. Q. Li, Y. F. Li, Z. B. Li, H. Liang, C. J. Lin, G. L. Lin, S. Lin, J. J. Ling, J. M. Link, L. Littenberg, B. R. Littlejohn, J. C. Liu, J. L. Liu, J. X. Liu, C. Lu, H. Q. Lu, K. B. Luk, B. Z. Ma, X. B. Ma, X. Y. Ma, Y. Q. Ma, R. C. Mandujano, C. Marshall, K. T. McDonald, R. D. McKeown, Y. Meng, J. Napolitano, D. Naumov, E. Naumova, T. M. T. Nguyen, J. P. Ochoa-Ricoux, A. Olshevskiy, H.-R. Pan, J. Park, S. Patton, J. C. Peng, C. S. J. Pun, F. Z. Qi, M. Qi, X. Qian, N. Raper, J. Ren, C. Morales Reveco, R. Rosero, B. Roskovec, X. C. Ruan, H. Steiner, J. L. Sun, T. Tmej, K. Treskov, W.-H. Tse, C. E. Tull, B. Viren, V. Vorobel, C. H. Wang, J. Wang, M. Wang, N. Y. Wang, R. G. Wang, W. Wang, W. Wang, X. Wang, Y. Wang, Y. F. Wang, Z. Wang, Z. Wang, Z. M. Wang, H. Y. Wei, L. H. Wei, L. J. Wen, K. Whisnant, C. G. White, H. L. H. Wong, E. Worcester, D. R. Wu, F. L. Wu, Q. Wu, W. J. Wu, D. M. Xia, Z. Q. Xie, Z. Z. Xing, H. K. Xu, J. L. Xu, T. Xu, T. Xue, C. G. Yang, L. Yang, Y. Z. Yang, H. F. Yao, M. Ye, M. Yeh, B. L. Young, H. Z. Yu, Z. Y. Yu, B. B. Yue, V. Zavadskyi, S. Zeng, Y. Zeng, L. Zhan, C. Zhang, F. Y. Zhang, H. H. Zhang, J. W. Zhang, Q. M. Zhang, S. Q. Zhang, X. T. Zhang, Y. M. Zhang, Y. X. Zhang, Y. Y. Zhang, Z. J. Zhang, Z. P. Zhang, Z. Y. Zhang, J. Zhao, R. Z. Zhao, L. Zhou, H. L. Zhuang, J. H. Zou and (Daya Bay Collaboration). Antineutrino Energy Spectrum Unfolding Based on the Daya Bay Measurement and Its Applications[J]. Chinese Physics C. doi: 10.1088/1674-1137/abfc38.

Factorization of radiative leptonic D-meson decay with sub-leading power corrections

Long-Sheng Lu

2021, 45(7): 073101. doi: 10.1088/1674-1137/abf5c9

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Abstract:
In this work, we calculate the sub-leading power contributions to radiative leptonic

\begin{document}$ D\to\gamma \,\ell \,\nu $\end{document}

decay. For the first time, we provide the analytic expressions of next-to-leading power contributions and the error estimation associated with the power expansion of

\begin{document}$ {\cal O}(\Lambda_{\rm QCD}/m_c) $\end{document}

. In our calculation, we adopt two different models of the D-meson distribution amplitudes

\begin{document}$ \phi_{D,\rm I}^+ $\end{document}

and

\begin{document}$ \phi_{D,\rm II}^+ $\end{document}

. Within the framework of QCD factorization as well as the dispersion relation, we evaluate the soft contribution up to the next-to-leading logarithmic accuracy and also consider the higher-twist contribution from the two-particle and three-particle distribution amplitudes. Finally, we find that all the sub-leading power contributions are significant at

\begin{document}$ \lambda_D(\mu_0) = 354 $\end{document}

MeV, and the next-to-leading power contributions lead to 143% in

\begin{document}$ \phi_{D,\rm I}^+ $\end{document}

and 120% in

\begin{document}$ \phi_{D,\rm II}^+ $\end{document}

corrections to leading power vector form factors with

\begin{document}$ E_{\gamma} = 0.5 $\end{document}

GeV. As the corrections from the higher-twist and local sub-leading power contributions are enhanced with increasing inverse moment, it is difficult to extract an appropriate inverse moment of the D-meson distribution amplitude. The predicted branching fractions are

\begin{document}$ (1.88_{-0.29}^{+0.36})\times10^{-5} $\end{document}

for

\begin{document}$ \phi_{D,\rm I}^+ $\end{document}

and

\begin{document}$ (2.31_{-0.54}^{+0.65})\times10^{-5} $\end{document}

for

\begin{document}$ \phi_{D,\rm II}^+ $\end{document}

.

Effective field theory approach to lepton number violating τ decays

Yi Liao, Xiao-Dong Ma, Hao-Lin Wang

2021, 45(7): 073102. doi: 10.1088/1674-1137/abf72e

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Abstract:
We continue our endeavor to investigate lepton number violating (LNV) processes at low energies in the framework of effective field theory (EFT). In this work we study the LNV tau decays

\begin{document}$ \tau^+\rightarrow \ell^-P_i^{+}P_j^{+} $\end{document}

, where

\begin{document}$ \ell = e,\; \mu $\end{document}

and

\begin{document}$ P^+_{i,j} $\end{document}

denote the lowest-lying charged pseudoscalars

\begin{document}$ \pi^+,\; K^+ $\end{document}

. We analyze the dominant contributions in a series of EFTs from high to low energy scales, namely the standard model EFT (SMEFT), the low-energy EFT (LEFT), and the chiral perturbation theory (

\begin{document}$ \chi{{\rm{PT}}} $\end{document}

). The decay branching ratios are expressed in terms of the Wilson coefficients of dimension-five and -seven operators in SMEFT and the hadronic low-energy constants. These Wilson coefficients involve the first and second generations of quarks and all generations of leptons; thus, they cannot be explored in low-energy processes such as nuclear neutrinoless double beta decay or LNV kaon decays. Unfortunately, the current experimental upper bounds on the branching ratios are too weak to set useful constraints on these coefficients. Alternatively, if we assume the new physics scale is larger than 1 TeV, the branching ratios are well below the current experimental bounds. We also estimate the hadronic uncertainties incurred in applying

\begin{document}$ \chi{{\rm{PT}}} $\end{document}

to

\begin{document}$ \tau $\end{document}

decays by computing one-loop chiral logarithms and attempt to improve the convergence of chiral perturbation by employing dispersion relations in the short-distance part of the decay amplitudes.

Dependence of overlap topological charge density on Wilson mass parameter

Zhen Cheng, Jian-bo Zhang

2021, 45(7): 073103. doi: 10.1088/1674-1137/abf827

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Abstract:
In this paper, we analyze the dependence of the topological charge density from the overlap operator on the Wilson mass parameter in the overlap kernel by the symmetric multi-probing source (SMP) method. We observe that non-trivial topological objects are removed as the Wilson mass is increased. A comparison of topological charge density calculated by the SMP method using the fermionic definition with that of the gluonic definition by the Wilson flow method is shown. A matching procedure for these two methods is used. We find that there is a best match for topological charge density between the gluonic definition with varied Wilson flow time and the fermionic definition with varied Wilson mass. By using the matching procedure, the proper flow time of Wilson flow in the calculation of topological charge density can be estimated. As the lattice spacing a decreases, the proper flow time also decreases, as expected.

Detecting anomalies in vector boson scattering

Jinmian Li, Shuo Yang, Rao Zhang

2021, 45(7): 073104. doi: 10.1088/1674-1137/abf829

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Measuring vector boson scattering (VBS) precisely is an important step toward understanding the electroweak symmetry breaking of and detecting new physics beyond the standard model (SM). Herein, we propose a neural network that compresses the features of the VBS data into a three-dimensional latent space. The consistency of the SM predictions and experimental data is tested via binned log-likelihood analysis in the latent space. We show that the network is capable of distinguishing different polarization modes of WWjj production in both di- and semi-leptonic channels. The method is also applied to constrain the effective field theory and two Higgs Doublet Model. The results demonstrate that the method is sensitive to general new physics contributing to the VBS.

QCD chiral phase transition and critical exponents within the nonextensive Polyakov-Nambu-Jona-Lasinio model

Ya-Peng Zhao, Shu-Yu Zuo, Cheng-Ming Li

2021, 45(7): 073105. doi: 10.1088/1674-1137/abf8a2

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Abstract:
We present a nonextensive version of the Polyakov-Nambu-Jona-Lasinio model that is based on nonextentive statistical mechanics. This new statistics model is characterized by a dimensionless nonextensivity parameter q that accounts for all possible effects violating the assumptions of the Boltzmann-Gibbs (BG) statistics (for

\begin{document}$q\rightarrow 1$\end{document}

, it returns to the BG case). Based on the nonextensive Polyakov-Nambu-Jona-Lasinio model, we discussed the influence of nonextensive effects on the curvature of the phase diagram at

\begin{document}$\mu=0$\end{document}

and especially on the location of the critical end point (CEP). A new and interesting phenomenon we found is that with an increase in q, the CEP position initially shifts toward the direction of larger chemical potential and lower temperature. However, when q is larger than a critical value

\begin{document}$q_{c}$\end{document}

, the CEP position moves in the opposite direction. In other words, as q increases, the CEP position moves in the direction of smaller chemical potential and higher temperature. This U-turn phenomenon may be important for the search of CEP in relativistic heavy-ion collisions, in which the validity of BG statistics is questionable due to strong fluctuations and long-range correlations, and nonextensive effects begin to manifest themselves. In addition, we calculated the influence of the nonextensive effects on the critical exponents and found that they remain almost constant with q.

Exact relations for two-photon-exchange effect in elastic ep scattering by dispersion relation and hadronic model

Hui-Yun Cao, Hai-Qing Zhou

2021, 45(7): 073106. doi: 10.1088/1674-1137/abf913

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The two-photon-exchange (TPE) effect plays a key role in extracting the form factors (FFs) of the proton. In this work, we discuss several exact properties of the TPE effect in the elastic

\begin{document}$ep$\end{document}

scattering. By taking four low energy interactions as examples, we analyze kinematical singularities, asymptotic behaviors, and branch cuts of TPE amplitudes. The analytical expressions clearly indicate several exact relations between the dispersion relation (DR) and hadronic model (HM) methods. This suggests that the two methods must be modified to general forms, while novel forms yield the same results. After the modification, new DRs include a non-trivial term with two singularities. Furthermore, new DRs automatically include contributions due to the seagull interaction, meson-exchange effect, contact interactions, and off-shell effect. To analyze the elastic

\begin{document}$e^{\pm}p$\end{document}

scattering data sets, the new forms must be used.

Analysis of Z_cs(3985) as the axialvector tetraquark state

Zhi-Gang Wang

2021, 45(7): 073107. doi: 10.1088/1674-1137/abfa83

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Abstract:
In this study, we choose the scalar and axialvector diquark operators in the color antitriplet as the fundamental building blocks to construct four-quark currents and investigate the diquark-antidiquark type axialvector tetraquark states

\begin{document}$ c\bar{c}u\bar{s} $\end{document}

in the framework of the QCD sum rules. The predicted tetraquark mass

\begin{document}$ M_Z = 3.99\pm0.09\;\rm{GeV} $\end{document}

is in excellent agreement with the experimental value

\begin{document}$ 3985.2^{+2.1}_{-2.0}\pm1.7\;\rm{MeV} $\end{document}

from the BESIII collaboration, which supports identifying

\begin{document}$ Z_{cs}(3985) $\end{document}

as the cousin of

\begin{document}$ Z_c(3900) $\end{document}

with quantum numbers

\begin{document}$ J^{PC} = 1^{+-} $\end{document}

. We take into account the light flavor

\begin{document}$ SU(3) $\end{document}

mass-breaking effect to estimate the mass spectrum of the diquark-antidiquark type hidden-charm tetraquark states with strangeness according to previous studies.

Di-Higgs production as a probe of flavor changing neutral Yukawa couplings

Shi-Ping He

2021, 45(7): 073108. doi: 10.1088/1674-1137/abfb50

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Top partners are well motivated in many new physics models. Usually, vector like quarks,

\begin{document}$T_{\rm L,R}$\end{document}

, are introduced to circumvent the quantum anomaly. Therefore, it is crucial to probe their interactions with standard model particles. However, flavor changing neutral couplings are always difficult to detect directly in current and future experiments. In this paper, we demonstrate how to constrain the flavor changing neutral Yukawa coupling

\begin{document}$Tth$\end{document}

indirectly, via the di-Higgs production. We consider the simplified model, including a pair of gauge singlet

\begin{document}$T_{\rm L,R}$\end{document}

. Under the perturbative unitarity and experimental constraints, we select

\begin{document}$m_T=400~{\rm{GeV}},s_{\rm L}=0.2$\end{document}

, and

\begin{document}$m_T= $\end{document}

\begin{document}$ 800~{\rm{GeV}},s_{\rm L}=0.1$\end{document}

as benchmark points. After the analysis on the amplitude and evaluation of the numerical cross sections, we infer that the present constraints from di-Higgs production have already surpassed the unitarity bound because of the

\begin{document}$(y_{\rm L,R}^{tT})^4$\end{document}

behavior. For the case of

\begin{document}$m_T=400~{\rm{GeV}}$\end{document}

and

\begin{document}$s_{\rm L}=0.2$\end{document}

,

\begin{document}${\rm{Re}}y_{\rm L,R}^{tT}$\end{document}

and

\begin{document}${\rm{Im}}y_{\rm L,R}^{tT}$\end{document}

can be bounded optimally in the range

\begin{document}$(-0.4, 0.4)$\end{document}

at the HL-LHC with

\begin{document}$2\sigma$\end{document}

CL. For the case of

\begin{document}$m_T=800~{\rm{GeV}}$\end{document}

and

\begin{document}$s_{\rm L}=0.1$\end{document}

,

\begin{document}${\rm{Re}}y_{\rm L,R}^{tT}$\end{document}

and

\begin{document}${\rm{Im}}y_{L,R}^{tT}$\end{document}

can be bounded optimally in the range

\begin{document}$(-0.5, 0.5)$\end{document}

at the HL-LHC with

\begin{document}$2\sigma$\end{document}

CL. The anomalous triple Higgs coupling

\begin{document}$\delta_{hhh}$\end{document}

can also affect the constraints on

\begin{document}$y_{\rm L,R}^{tT}$\end{document}

. Finally, we determine that the top quark electric dipole moment can provide stronger

\begin{document}$y_{\rm L,R}^{tT}$\end{document}

bounds in the off-axis regions for some scenarios.

Chiral symmetry restoration and deconfinement in the contact interaction model of quarks with parallel electric and magnetic fields

Aftab Ahmad

2021, 45(7): 073109. doi: 10.1088/1674-1137/abfb5f

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Abstract:
We study the impact of steady, homogeneous, and external parallel electric and magnetic field strengths (

\begin{document}$ eE\parallel eB $\end{document}

) on the chiral symmetry breaking-restoration and confinement-deconfinement phase transition. We also sketch the phase diagram of quantum chromodynamics (QCD) at a finite temperature T and in the presence of background fields. The unified formalism for this study is based on the Schwinger-Dyson equations, symmetry preserving vector-vector contact interaction model of quarks, and an optimal time regularization scheme. At

\begin{document}$ T = 0 $\end{document}

, in the purely magnetic case (i.e.,

\begin{document}$ eE\rightarrow 0 $\end{document}

), we observe the well-known magnetic catalysis effect. However, in a pure electric field background (

\begin{document}$ eB\rightarrow 0 $\end{document}

), the electric field tends to restore the chiral symmetry and deconfinement above the pseudo-critical electric field

\begin{document}$ eE^{\chi, C}_c $\end{document}

. In the presence of both

\begin{document}$ eE $\end{document}

and