We analyze the inclusive $b(c) \to s(u) μ^+ μ^-$ and the exclusive $B(D^+) \to K(π^+) μ^+ μ^-$ flavour changing neutral current decays in the light of HyperCP boson $X^0$ of mass 214 MeV recently observed in the hyperon decay $Σ^+ \to p μ^+ μ^-$. Using the branching ratio data of the above inclusive and exclusive decays, we obtain constraints on $g_1 (h_1)$ and $g_2 (h_2)$, the scalar and pseudo-scalar coupling constants of the $b-s-X^0 (c-u-X^0)$ vertices.
HyperCP合作已经观察到三个衰变事件Sigma^+ -> p mu^+ mu^-，这可能被解释为质量为214.3 MeV的新粒子。然而，现有的数据从K介子和B介子衰变严重限制了这种解释，它是不平凡的，以建立一个模型与所有的数据一致。在这封信中，我们证明了“超CP粒子”可以与次最小超对称标准模型A_1^0中的轻赝标量希格斯玻色子等同。在这个模型中，存在一些参数空间区域，在这些区域中，A_1^0可以满足来自K介子和B介子衰变的所有现有约束，并在与HyperCP观测一致的水平上介导Sigma^+ -> p mu^+ mu^-。
Right-handed neutrinos with MeV to GeV mass are very promising candidates for dark matter (DM). Not only can they solve the missing satellite puzzle, the cusp-core problem of inner DM density profiles, and the too-big-to fail problem, {\it i.e.} that the unobserved satellites are too big to not have visible stars, but they can also account for the Standard Model (SM) neutrino masses at one loop. We perform a comprehensive study of the right-handed neutrino parameter space and impose the correct observed relic density and SM neutrino mass differences and mixings. We find that the DM masses are …
The meV frontier of neutrinoless double beta decay in the JUNO era
INFN Sezione di Roma Tre（罗马第三大学INFN分部）；SISSA/INFN（的里雅斯特国际高等研究学校/意大利国家核物理研究所）；Kavli IPMU (WPI), UTIAS, The University of Tokyo（东京大学 Kavli宇宙粒子与天体物理前沿研究中心（WPI））；Institute of Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences（保加利亚科学院核研究与核能研究所）
We study properties of pseudoscalar flavour-singlet mesons from Wilson twisted mass lattice QCD with Nf=2+1+1 dynamical quark flavors. Results for masses are presented at three values of the lattice spacing and light quark masses corresponding to values of the pion mass from 230 MeV to 500 MeV. We briefly discuss scaling effects and the light and strange quark mass dependence of the eta mass. In addition we present an exploratory study using Osterwalder-Seiler type strange and charm valence quarks. This approach avoids some of the complications of the twisted mass heavy doublet. We present fir…
We present calculations of the chemical freeze-out temperature (T_ch) based on particle yields from STAR and ALICE measured at collision energies ranging from sqrt{s_{NN}} = 11.5 GeV to 5.02 TeV. Employing the Grand Canonical Ensemble approach using the Thermal-FIST Hadron Resonance Gas model package, we show evidence for a flavour-dependent chemical freeze-out in the crossover region of the QCD phase diagram. At a vanishing baryochemical potential, we calculate light and strange flavour freeze-out temperatures T_L = 150.2 +- 2.6 MeV and T_S = 165.1 +- 2.7 MeV, respectively.
We estimate the values of Yukawa couplings of a light pseudoscalar A with a mass of about 17 MeV, which would explain the $^8Be$ anomaly observed in the Atomki pair spectrometer experiment. The resulting couplings of A to up and down type quarks are about 0.3 times the coupling of the standard Higgs boson. Then constraints from K and B decays require that loop contributions to flavour changing vertices cancel at least at the 10% level. Constraints from beam dump experiments require the coupling of A to electrons to be larger than about 4 times the coupling of the standard Higgs boson, leading …
We compute the spectral density of the (Hermitean) Dirac operator in Quantum Chromodynamics with two light degenerate quarks near the origin. We use CLS/ALPHA lattices generated with two flavours of O(a)-improved Wilson fermions corresponding to pseudoscalar meson masses down to 190 MeV, and with spacings in the range 0.05-0.08 fm. Thanks to the coverage of parameter space, we can extrapolate our data to the chiral and continuum limits with confidence. The results show that the spectral density at the origin is non-zero because the low modes of the Dirac operator do condense as expected in the…
We build a highly predictive 3-3-1 model, where the field content is extended by including several $SU(3)_{L}$ scalar singlets and six right handed Majorana neutrinos. In our model the $SU(3)_{C}\times SU\left( 3\right) _{L}\times U\left( 1\right) _{X}$ gauge symmetry is supplemented by the $A_{4}\times Z_{4}\times Z_{6}\times Z_{16}\times Z_{16}^{\prime }$ discrete group, which allows to get a very good description of the low energy fermion flavor data. In the model under consideration, the $A_{4}\times Z_{4}\times Z_{6}\times Z_{16}\times Z_{16}^{\prime }$ discrete group is broken at very hi…
We calculate the decay of $τ^-\toπ^-γν_τ$ in the framework of Resonance Chiral Theory ($RχT$). By demanding the high energy constraints from QCD on the related form factors, we could predict the various physical observables of $τ^-\toπ^-γν_τ$ without any free parameter. Our results show that for a realistic cut on the photon energy (around $100$ MeV) this mode gives a branching ratio of roughly $0.1%$ that should have already been detected at the heavy-flavour factories. Another interesting subject we have studied based on our calculation of the decay $τ^-\toπ^-γν_τ$ is the experimental backgr…
Machine learning unveils the quark mass dependence of the pseudoscalar meson decay constants in three-flavour N$^2$LO ChPT
Departamento de Física Teórica and IFIC, Centro Mixto Universidad de Valencia-CSIC（瓦伦西亚大学-西班牙国家科学研究委员会联合中心理论物理系与IFIC）；School of Physics, University of Electronic Science and Technology of China（电子科技大学物理学院）
We compute the hadronic matrix elements of the four-quark operators needed for the study of neutral kaon mixing beyond the Standard Model (SM). We use nf=2+1 flavours of domain-wall fermions (DWF) which exhibit good chiral-flavour symmetry. The renormalization is performed non-perturbatively through the RI-MOM scheme and our results are converted perturbatively to MSbar. The computation is performed on a single lattice spacing a=0.086 fm with a lightest unitary pion mass of 290 MeV. The various systematic errors, including the discretisation effects, are estimated and discussed. Our results co…
Neutrino oscillations and signals in beta and 0nu2beta experiments
假设Majorana中微子，我们推断振荡数据的预期值的参数m_{nu_e}和m_{ee}探测β和0 nu 2 β衰变实验。如果中微子有一个“正常的层次”，我们得到90%的CL范围|m_{ee}| =（0.7 - 4.6）meV，并讨论在这种情况下，未来的实验可以测试这种可能性。对于“逆层次”，我们得到|m_{ee}| =（12 - 57）meV和m_{ν_e} =（40 - 57）meV。0 nu 2beta的数据意味着，几乎简并中微子轻于1.05 h eV在90% CL，与β衰变约束的竞争。我们批判性地重新分析了最近用于声称0 nu 2beta证据的数据，并讨论了它们的含义。最后，我们回顾了m_{ee}和theta_{13}的风味模型的预测。
Extending the Constituent Gluon Model to Heavy-Flavour Hybrids: A Unified Study of $c\bar{c}g$ Mesons
Nanjing Normal University（南京师范大学）；Hunan Normal University（湖南师范大学）；Changzhou Vocational Institute of Engineering（常州工程职业技术学院）；Yancheng Institute of Technology（盐城工学院）；Lanzhou University（兰州大学）
We revisit QCD sum rules for the decay constants of heavy-light mesons. In the sum rules for the vector mesons B^*_(s) and D^*_(s) we improve the accuracy of OPE, taking into account the O(alpha_s^2) terms in the perturbative part and calculating the O(alpha_s) corrections to the quark-condensate contribution. With this accuracy, we obtain the ratios of decay constants: f_B^*/f_B=1.02 +0.07 -0.03, f_D^*/f_D=1.20 +0.10 -0.07. The sum rule predictions for the decay constants of pseudoscalar mesons are updated with the results f_B=(207 +17 -9) MeV, f_B_s=(242 +17 -12) MeV, f_D=(201 +12 -13) MeV, …
Heavy-quark symmetry as applied to heavy hadron systems implies that their interactions are independent of their heavy-quark spin (heavy-quark spin symmetry) and heavy flavour contents (heavy flavour symmetry). In the molecular hypothesis the $X(3872)$ resonance is a $1^{++}$ $D^*\bar{D}$ bound state. If this is the case, the application of heavy-quark symmetry to a molecular $X(3872)$ suggests the existence of a series of partner states, the most obvious of which is a possible $2^{++}$ $D^*\bar{D}^*$ bound state for which the two-body potential is identical to that of the $1^{++}$ $D^*\bar{D}…
In this paper we derive constraints on the emission of a massive (pseudo)scalar $S$ from annihilation of neutrinos in the core of supernovae through the dimension-4 coupling $ννS$, as well as the effective dimension-5 operator $\frac{1}Λ(νν)(SS)$. While most of earlier studies have focused on massless or ultralight scalars, our analysis involves scalar with masses of order $\mathrm{eV- GeV}$ which can be copiously produced during the explosion of supernovae, whose core temperature is generally of order $T\sim \mathcal{O}(10)$ MeV. From the luminosity and deleptonization arguments regarding the…
