Highlights

Positivity in electronpositron scattering: testing the axiomatic quantum field theory principles and probing the existence of UV states
2021, 45(2): 023108. doi: 10.1088/16741137/abcd8cWe consider the positivity bounds on dimension8 fourelectron operators and study two related phenomenological aspects at future lepton colliders. First, if positivity is violated, probing such violations will revolutionize our understanding of the fundamental pillars of quantum field theory and the Smatrix theory. We observe that positivity violation at scales of 110 TeV can potentially be probed at future lepton colliders even if one assumes that dimension6 operators are also present. Second, the positive nature of the dimension8 parameter space often allows us to either directly infer the existence of UVscale particles together with their quantum numbers or exclude them up to certain scales in a modelindependent way. In particular, dimension8 positivity plays an important role in the test of the Standard Model. If no deviations from the Standard Model are observed, it allows for simultaneous exclusion limits on all kinds of potential UVcomplete models. Unlike the dimension6 case, these limits apply regardless of the UV model setup and cannot be removed by possible cancellations among various UV contributions. This thus consists of a novel and universal test to confirm the Standard Model. We demonstrate with realistic examples how all the previously mentioned possibilities, including the test of positivity violation, can be achieved. Hence, we provide an important motivation for studying dimension8 operators more comprehensively.

Diffuseness effect and radial basis function network for optimizing α decay calculations
2021, 45(2): 024105. doi: 10.1088/16741137/abcc5cA radial basis function network (RBFN) approach is adopted for the first time to optimize the calculation of
$ \alpha $ decay halflife in the generalized liquid drop model (GLDM), while concurrently incorporating the surface diffuseness effect. The calculations presented herein agree closely with the experimental halflives for 68 superheavy nuclei (SHN), achieving a remarkable reduction of 40% in the rootmeansquare (rms) deviations of halflives. Furthermore, using the RBFN method, the halflives for four SHN isotopes, ^{252288}Rf, ^{272310}Fl, ^{286316}119, and ^{292318}120, are predicted using the improved GLDM with the diffuseness correction and the decay energies from WS4 and FRDM as inputs. Therefore, we conclude that the diffuseness effect should be embodied in the proximity energy. Moreover, increased application of neural network methods in nuclear reaction studies is encouraged. 
Charmed and ϕ meson decay constants from 2+1flavor lattice QCD
2021, 45(2): 023109. doi: 10.1088/16741137/abcd8fOn a lattice with 2+1flavor dynamical domainwall fermions at the physical pion mass, we calculate the decay constants of
$ D_{s}^{(*)} $ ,$ D^{(*)} $ , and$ \phi $ . The lattice size is$ 48^3\times96 $ , which corresponds to a spatial extension of$ \sim5.5 $ fm, with a lattice spacing of$ a\approx 0.114 $ fm. For the valence light, strange, and charm quarks, we use overlap fermions at several mass points close to their physical values. Our results at the physical point are$ f_D = 213(5) $ MeV,$ f_{D_s} = 249(7) $ MeV,$ f_{D^*} = 234(6) $ MeV,$ f_{D_s^*} = 274(7) $ MeV, and$ f_\phi = 241(9) $ MeV. The couplings of$ D^* $ and$ D_s^* $ to the tensor current ($ f_V^T $ ) can be derived from ratios$ f_{D^*}^T/f_{D^*} = 0.91(4) $ and$ f_{D_s^*}^T/f_{D_s^*} = 0.92(4) $ , respectively, which are the first lattice quantum chromodynamics (QCD) results. We also obtain ratios$ f_{D^*}/f_D = 1.10(3) $ and$ f_{D_s^*}/f_{D_s} = 1.10(4) $ , which reflect the size of heavy quark symmetry breaking in charmed mesons. Ratios$ f_{D_s}/f_{D} = 1.16(3) $ and$ f_{D_s^*}/f_{D^*} = 1.17(3) $ can be taken as a measure of SU(3) flavor symmetry breaking.
Just Accepted
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An improved semiempirical relationship for cluster radioactivity
Published: 20210125

Dynamics of kessence in loop quantum cosmology
Published: 20210125

Origin of the hardening in AMS02 nuclei spectra at a few hundred GV
Published: 20210125
In Press
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Exotic ΩΩ dibaryon states in a molecular picture
Published: 20210126Show AbstractWe investigate the exotic
$\Omega\Omega$ dibaryon states with$J^P=0^+$ and$2^+$ in a molecular picture. We construct a tensor$\Omega$ $\Omega$ molecular interpolating current and calculate the twopoint correlation function within the method of QCD sum rules. Our calculations indicate that the masses of the scalar and tensor dibaryon states are$m_{\Omega\Omega, \, 0^+} = $ $ (3.33\pm 0.51) \,{\rm{GeV}}$ and$m_{\Omega\Omega,\, 2^+}=(3.15\pm0.33)\, {\rm{GeV}}$ , respectively, which are below the$2m_\Omega$ threshold. Within error, these results do not negate the existence of loosely bound molecular$\Omega\Omega$ dibaryon states. These exotic strangeness$S=6$ and doublycharged$\Omega\Omega$ dibaryons, if they exist, may be identified in heavyion collision processes in the future. 
Probing tqZ anomalous couplings in the trilepton signal at the HLLHC, HELHC, and FCChh
Published: 20210126Show AbstractWe investigate the prospect of discovering the Flavour Changing Neutral Current (FCNC)
$ tqZ $ couplings via two production processes yielding trilepton signals: top quark pair production$ pp\to t\bar{t} $ with one top quark decaying to the Z boson and one light jet and the anomalous single top quark plus Z boson production process$ pp\to tZ $ . We study these channels at various successors of the Large Hadron Collider (LHC), i.e., the approved HighLuminosity LHC (HLLHC) as well as the proposed HighEnergy LHC (HELHC) and Future Circular Collider in hadronhadron mode (FCChh). We perform a full simulation for the signals and the relevant Standard Model (SM) backgrounds and obtain limits on the Branching Ratios (BRs) of$ t\to qZ\; (q = u,c) $ , eventually yielding a trilepton final state through the decay modes$ t\to b W^{+}\to b\ell^{+}\nu_{\ell} $ and$ Z\to \ell^{+}\ell^{} $ . The upper limits on these FCNC BRs at 95% Confidence Level (CL) are obtained at the HLLHC with$ \sqrt s = 14 $ TeV and 3 ab^{−1}, at the HELHC with$ \sqrt s = 27 $ TeV and 15 ab^{−1}, and at the FCChh with$ \sqrt s = 100 $ TeV and 30 ab^{−1}. 
Diagonal reflection symmetries and universal fourzero texture
Published: 20210126Show AbstractIn this paper, we consider a set of new symmetries in the SM: diagonal reflection symmetries
$R \, m_{u,\nu}^{*} \, R = m_{u,\nu}, m_{d,e}^{*} = m_{d,e}$ with$R =$ diag$(1,1,1)$ . These generalized$CP$ symmetries predict the Majorana phases to be$\alpha_{2,3} /2 = 0$ or$\pi /2$ . Realization of diagonal reflection symmetries implies a broken chiral$U(1)_{\rm{PQ}}$ symmetry only for the first generation. The axion scale is suggested to be$\langle {\theta_{u,d}} \rangle \sim \Lambda_{\rm{GUT}} \, \sqrt{m_{u,d} \, m_{c,s}} / v \sim 10^{12} $ [GeV]. By combining the symmetries with the fourzero texture, the mass eigenvalues and mixing matrices of quarks and leptons are reproduced well. This scheme predicts the normal hierarchy, the Dirac phase$\delta _{CP} \simeq 203^{\circ},$ and$m_{1} \simeq 2.5$ or$6.2 $ [meV]. In this scheme, the typeI seesaw mechanism and a given neutrino Yukawa matrix$Y_{\nu}$ completely determine the structure of the righthanded neutrino mass$M_{R}$ . A$u\nu$ unification predicts the mass eigenvalues to be$ (M_{R1} \, , M_{R2} \, , M_{R3}) = (O (10^{5}) \, , O (10^{9}) \, , O (10^{14})) $ [GeV].
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ISSN 16741137 CN 115641/O4
Original research articles, Ietters and reviews Covering theory and experiments in the fieids of
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