This paper presents a systematic investigation of the electromagnetic properties of the hidden-charm molecular pentaquarks within the constituent quark model. Specifically, it focuses on two types of pentaquarks: the $Ξ_c^{(\prime,*)} \bar{D}_s^{*}$-type pentaquarks with double strangeness and the $Ω_{c}^{(*)}\bar D_s^{*}$-type pentaquarks with triple strangeness. The study explores various electromagnetic properties, including the magnetic moments, the transition magnetic moments, and the radiative decay behavior of these pentaquarks. To ensure realistic calculations, the $S$-$D$ wave mixing effect and the coupled channel effect are taken into account. By examining the electromagnetic properties of the hidden-charm molecular pentaquarks with double and triple strangeness, this research contributes to the deeper understanding of their spectroscopic behavior. These findings form a valuable addition to the ongoing investigation into the broader spectrum of properties exhibited by the hidden-charm molecular pentaquarks.
The observation of anomalies in the charged current $b\rightarrow c\bar{\ell}ν_{\ell}$ transitions hints the possibility of the existence of new physics beyond the standard model. Inspired by the work done in the beauty quark sector, we explore new physics in the charm quark sector with $c \rightarrow (s,d)\bar{\ell}ν_{\ell}$ charged current transitions. We analyze the decay modes $D_{(s)}^+ \to η^{(')} \bar{\ell} ν_{\ell}$ within an effective Lagrangian framework which includes both standard model and new physics contributions. We use the available experimental measurements of the semileptoni…
Stimulated by the new discovery of $P_{c}(4312)^{+}$ by LHCb Collaboration, we endeavor to perform the study of $P_{c}(4312)^{+}$ as a $Σ_{c}\bar{D}$ state in the framework of QCD sum rules. Taking into account the results from two sum rules, a conservative mass range $4.07\sim4.97~\mbox{GeV}$ is presented for the $Σ_{c}\bar{D}$ hadronic system, which agrees with the experimental data of $P_{c}(4312)^{+}$ and could support its interpretation as a $Σ_{c}\bar{D}$ state.
In the $B^+\to D^+ D^-K^+$ decay, LHCb has reported the observation of the open-charm exotic states $X_{0,1}^0\equiv X_{0,1}(2900)^0$ with four different quark flavors~$(ud\bar s \bar c)$, where the subscripts (0,1) denote the spins. To confirm the discovery, we propose $Λ_b\to Σ_c^{0(++)} X_{0,1}^{\prime\,0(--)}$ in the final state interaction, where $X_{0,1}^{\prime\,0(--)}$ with $s u\bar d \bar c$ ($ds\bar u \bar c$) are the new $X_{0,1}$-like exotic states. More specifically, $Λ_c^+D_s^-$ in $Λ_b\to Λ_c^+D_s^-$ are transformed as $Σ_c^{0(++)} X_{0,1}^{\prime\,0(--)}$, by exchanging $π^{+(-…
Very recently, the LHCb Collaboration observed distinct structures with the $cc\bar{c}\bar{c}$ in the $J/Ψ$-pair mass spectrum. In this work, we construct four scalar ($J^{PC} = 0^{++}$) $[8_c]_{Q\bar{Q^\prime}}\otimes [8_c]_{Q^\prime \bar{Q}}$ type currents to investigate the fully-heavy tetraquark state $Q Q^\prime \bar{Q} \bar{Q^\prime}$ in the framework of QCD sum rules, where $Q=c, b$ and $Q^\prime = c, b$. Our results suggest that the broad structure around 6.2-6.8 GeV can be interpreted as the $0^{++}$ octet-octet tetraquark states with masses $6.44\pm 0.11$ GeV and $6.52\pm 0.10$ GeV, …
$QQ^{\prime} \bar u \bar d$ bound state in the Bethe-Salpeter equation approach
在重夸克极限下,我们建立了含有一个重双夸克$QQ^{\prime}$($Q, Q^{\prime}=b$或$c$)和一个轻反双夸克$\bar u \bar d$的基态$QQ^{\prime} \bar u \bar d$的Bethe-Salpeter方程.我们在协变瞬时近似下数值求解了Bethe-Salpeter方程,其核包含一个标量禁闭项和一个胶子交换项。数值解的Bethe-Salpeter波函数。结果表明,$bb \bar u \bar d$、$bc \bar u \bar d$和$cc \bar u \bar d$束缚态的质量分别低于$\bar{B}^{*0}\,B^-$或$B^0\,{B^*}^-$、$B^-D^+$或$\bar{B}^{0} D^0$、$D^+\,{D^*}^0$或${D^*}^+\,D^0$介子的阈值.基态$QQ^{\prime} \bar u \bar d$可能存在,我们预计即将到来的实验数据将证实它们。
Angular and invariant-mass observables in the four-body Higgs decay $h\to\ell\barν_\ell\bar{\ell}^\primeν_{\ell^\prime}$
Zhengzhou University(郑州大学);Chongqing University of Posts & Telecommunications(重庆邮电大学);Chongqing University(重庆大学);Chongqing University of Science and Technology(重庆科技大学)
Very recent experimental information obtained from the Belle experiment, along with that accumulated by the BABAR and LHCb experiments, has shown the existence of anomalies in the ratios $R(D)$ and $R(D^{*})$ associated with the charged-current transition $b \to c τ\barν_τ$. Although the Belle measurements are in agreement with the standard model (SM) predictions, the new experimental world averages still exhibit a tension. In addition, the $D^\ast$ longitudinal polarization $F_L(D^\ast)$ related with the channel $B \to D^\ast τ\barν_τ$ observed by the Belle Collaboration and the ratio $R(J/ψ)…
Motivated by the first search for the rare charged-current $B$ decay to four leptons, $\ell \barν_\ell \ell^{(\prime)} \bar{\ell}^{(\prime)}$, we calculate the decay amplitude with factorization methods. We obtain the $B\to γ^*$ form factors, which depend on the invariant masses of the two lepton pairs, at leading power in an expansion in $Λ_{\rm QCD}/m_b$ to next-to-leading order in $α_s$, and at $\mathcal{O}(α_s^0)$ at next-to-leading power. Our calculations predict branching fractions of a few times $10^{-8}$ in the $\ell^{(\prime)} \bar{\ell}^{(\prime)}$ mass-squared bin up to $q^2=1~\text…
Contributions of the subprocesses $ρ(770,1450,1700)\to K \bar{K}$ and $ω(782,1420,1650)\to K \bar{K}$ for the three-body decays $B\to η^{(\prime)} K\bar{K}$
Shanxi University(山西大学);Nanjing Institute of Technology(南京工程学院)
In this paper, we investigate the tree-dominated $\bar{B}^*_{u,d,s,c} \to V \ell^- \barν_\ell$ ($V=D^*_{u,d}\,,D^*_s\,,J/ψ$ and $\ell=e\,,μ\,,τ$) decays in the Standard Model with the relevant form factors obtained in the light-front quark model. These decays involve much more helicity states relative to the corresponding $\bar{B}^* \to P \ell^- \barν_\ell$ and $\bar{B} \to V \ell^- \barν_\ell$ decays, and moreover, the contribution of longitudinal polarization mode ($V$ meson) is relatively small, $\sim 30\%$, compared with the corresponding $B$ meson decays. We have also computed the branchi…
The new strange pentaquarks observed by LHCb are very likely hadronic molecules consisting of $Ξ_c \bar D$ and $Ξ_c \bar D^{*}.$ We discuss the experimental evidence supporting this conclusion, pointing out the similarities and differences with the $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$ pentaquarks in the non-strange sector. The latter clearly are hadronic molecules consisting of $Σ_c \bar D$ and $Σ_c \bar D^{*}.$ Following this line of thought, we predict three additional strange pentaquarks, consisting of $Ξ_c^{\prime} \bar D$ and $Ξ_c^{\prime} \bar D^{*}.$ The masses of these states are e…
Motivated by the LHCb observation of exotic states $X_{0,1}(2900)$ with four open quark flavors in the $D^- K^+$ invariant mass distribution in the decay channel $B^\pm \to D^+ D^- K^\pm$, we study the spectrum and decay properties of the open charm tetraquarks. Using the two-body chromomagnetic interactions, we find that the two newly observed states can be interpreted as a radial excited tetraquark with $J^P=0^+$ and an orbitally excited tetraquark with $J^P=1^-$, respectively. We then explore the mass and decays of the other flavor-open tetraquarks made of $su \bar d \bar c$ and $ d s \bar …
Exploring open-charm decay mode $Λ_c\barΛ_c$ of charmonium-like state $Y(4630)$
新观测到的$X, Y, Z$奇异态肯定不是标准的$Q\bar Q'$结构,因此它们的存在对我们对强子物理基本原理的理解构成了挑战。因此,对它们的衰变模式的研究必将对相关物理学的发展有所启发。一般来说,四夸克态可能是分子态、四夸克态或它们的混合态。在本工作中,我们采用了这样的假设:$Y(4630)$是由一个双夸克和一个反双夸克组成的类粲偶素四夸克态。如果这是真的,它的有利衰变模式应该是$Y(4630)$衰变成开魅重子对,因为这种跃迁是通过强相互作用发生的,并且是超OZI允许的。本文在夸克对产生模型的框架下计算了$Y(4630)\toΛ_c\barΛ_c$的衰变宽度。在一定的误差范围内,我们计算的四夸克组态的部分宽度的数值结果与Belle数据相吻合。
We apply the method of QCD sum rules to study the structure $X$ newly observed by the BESIII Collaboration in the $ϕη^\prime$ mass spectrum in 2.0-2.1 GeV region in the $J/ψ\rightarrow ϕηη^\prime$ decay. We construct all the $s s \bar s \bar s$ tetraquark currents with $J^{PC} = 1^{+-}$, and use them to perform QCD sum rule analyses. One current leads to reliable QCD sum rule results and the mass is extracted to be $2.00^{+0.10}_{-0.09}$ GeV, suggesting that the structure $X$ can be interpreted as an $s s \bar s \bar s$ tetraquark state with $J^{PC} = 1^{+-}$. The $Y(2175)$ can be interpreted …
We present compact analytic results for the one-loop amplitude for the process $0 \rightarrow q \bar{q} \ell \bar\ell \ell^\prime \bar{\ell}^\prime g$, relevant for both the production of a pair of $Z$ and $W$-bosons in association with a jet. We focus on the gauge-invariant contribution mediated by a loop of quarks. We explicitly include all effects of the loop-quark mass $m$, appropriate for the production of a pair of $Z$-bosons. In the limit $m \to 0$, our results are also applicable to the production of $W$-boson pairs, mediated by a loop of massless quarks. Implemented in a numerical cod…
In this work, the strong decay behaviors of the $λ-$mode low-lying $Ξ_{b}$ and $Ξ_{b}^\prime$ baryons are investigated within the $^3P_0$ model. Our results suggest that all of the low-lying $\bar 3_F$ states $Ξ_b(2S)$, $Ξ_b(1P)$, and $Ξ_b(1D)$ have small decay widths of less than 20 MeV, and these states have good potentials to be observed in the $Ξ_b^\prime π$ and $Ξ_b^{\prime *} π$ invariant masses. Further, most of the $6_F$ multiplets are relatively narrow and may decay into the $Ξ_b π$, $Ξ_b^\prime π$, $Ξ_b^{\prime *} π$, and $Λ_b \bar K$ final states. Considering the masses and strong d…
Within $Z^\prime$ models, neutral meson mixing severely constrains beyond the Standard Model (SM) effects in flavour changing neutral current (FCNC) processes. However, in certain regions of the $Z^\prime$ parameter space, the contributions to meson mixing observables become negligibly small even for large $Z^\prime$ couplings. While this a priori allows for significant new physics (NP) effects in FCNC decays, we discuss how large $Z^\prime$ couplings in one neutral meson sector can generate effects in meson mixing observables of other neutral mesons, through correlations stemming from $\text{…
In the present work, the mass spectra of doubly heavy tetraquarks $T_{QQ^\prime}$ are systematically investigated in a relativized quark model. The four-body systems including the Coulomb potential, confining potential, spin-spin interactions, and relativistic corrections are solved within the variational method. Our results suggest that the $IJ^P=01^+$ $bb \bar u \bar d$ state is 54 MeV below the relevant $\bar B \bar B$ and $\bar B \bar B^*$ thresholds, which indicates that both strong and electromagnetic decays are forbidden, and thus this state can be a stable one. Its large hidden color c…
We use the results of CMS and ATLAS searches for resonances that decay to $τν$ or $tb$ and $τ^+τ^-$ or $t\bar t$ final states to constrain the parameters of non-universal $W^\prime$ and $Z^\prime$ gauge bosons that couple preferentially to the third generation. For the former we consider production from $c\bar{b}$ annihilation and find very weak constraints on the strength of the interaction and only for the mass range between 800 and 1100 GeV from the $pp \to τ_h p_T^{\rm miss}$ channel. The constraints on the latter are much stronger and arise from both $t\bar t$ and $τ^+τ^-$ production. Tre…
We investigate Majorana dark matter in a new variant of $U(1)_{L_μ-L_τ}$ gauge extension of Standard Model, where the scalar sector is enriched with an inert doublet and a $(\bar{3},1,1/3)$ scalar leptoquark. We compute the WIMP-nucleon cross section in leptoquark portal and the relic density mediated by inert doublet components, leptoquark and the new $Z^{\prime}$ boson. We constrain the parameter space consistent with Planck limit on relic density, PICO-60 and LUX bounds on spin-dependent direct detection cross section. Furthermore, we constrain the new couplings from the present experimenta…