The $Ξ^-_\mathrm{b} π^+ π^-$ invariant mass spectrum is investigated with an event sample of proton-proton collisions at $\sqrt{s} = $ 13 TeV, collected by the CMS experiment at the LHC in 2016-2018 and corresponding to an integrated luminosity of 140 fb$^{-1}$. The ground state $Ξ^-_\mathrm{b}$ is reconstructed via its decays to J$/ψ$ $Ξ^-$ and J$/ψ$ $Ξ^-$ $Λ$ K$^-$. A narrow resonance, labeled $Ξ_\mathrm{b}$(6100)$^-$, is observed at a $Ξ^-_\mathrm{b} π^+ π^-$ invariant mass of 6100.3 $\pm$ 0.2 (stat) $\pm$ 0.1 (syst) $\pm$ 0.6 ($Ξ^-_\mathrm{b}$) MeV, where the last uncertainty reflects the precision of the $Ξ^-_\mathrm{b}$ baryon mass. The upper limit on the $Ξ_\mathrm{b}$(6100)$^-$ natural width is determined to be 1.9 MeV at 95% confidence level. Following analogies with the established excited $Ξ_\mathrm{c}$ baryon states, the new $Ξ_\mathrm{b}$(6100)$^-$ resonance and its decay sequence are consistent with the orbitally excited $Ξ^-_\mathrm{b}$ baryon, with spin and parity quantum numbers $J^P$ $=$ 3/2$^-$.
Beauty quarks are considered as one of the best probes of the strongly interacting medium created in relativistic heavy-ion collisions because they are predominantly produced via initial hard scatterings. Our measurements of B mesons productions provide information on the diffusion of beauty quarks and the flavor dependence of in-medium energy loss. In these studies, clarifying the hadronization mechanism is crucial for understanding the transport properties of beauty quarks. We propose to show our experimental results on three sets of particles: nonprompt $J/ψ$ and $D^0$, $B^0_s$ and $B^+$, a…
The recent discovery, by the LHCb collaboration, of the $Ξ_{cc}^{++}$ doubly charmed baryon, has renewed interest in the spectroscopy of doubly heavy hadrons. Experimentally, however, searches for such states appear highly challenging. The reconstructed final states tend to involve multiple heavy flavoured (beauty or charm) hadrons, so the yield for any exclusive decay mode will be suppressed to unobservably low levels by the product of several branching fractions, each of which is typically $10^{-3}$--$10^{-2}$. Noting that decays of double beauty hadrons are the only possible source of $B_c^…
Chiral Doubling of Heavy-Light Hadrons and the New Beauty--Strange $B_{s0}^*(5700)^0$ Candidate
Institute of Theoretical Physics and Mark Kac Center for Complex Systems Research, Jagiellonian University（雅盖隆大学理论物理研究所和马克·卡克复杂系统研究中心）；Center for Nuclear Theory, Department of Physics and Astronomy, Stony Brook University（石溪大学物理与天文学系核理论中心）
The new LHCb beauty-strange state as the bottom partner of the $D_{s0}^*(2317)$: a LQCD constrained coupled-channel chiral analysis
Instituto de Física Corpuscular, Centro Mixto Universidad de Valencia-CSIC（瓦伦西亚大学-西班牙国家研究委员会联合物理粒子研究所）；Departamento de Física Teórica and IFIC, Centro Mixto Universidad de Valencia-CSIC（瓦伦西亚大学-西班牙国家研究委员会联合理论物理系及IFIC）
The $p_\mathrm{T}$-differential production cross sections of prompt and non-prompt (produced in beauty-hadron decays) D mesons were measured by the ALICE experiment at midrapidity ($|y|<0.5$) in proton--proton collisions at $\sqrt{s}=5.02~\mathrm{TeV}$. The data sample used in the analysis corresponds to an integrated luminosity of $(19.3\pm0.4)~\mathrm{nb^{-1}}$. D mesons were reconstructed from their decays $\mathrm{D^0 \to K^-π^+}$, $\mathrm{D^+\to K^-π^+π^+}$, and $\mathrm{D_s^+\to ϕπ^+\to K^-K^+π^+}$ and their charge conjugates. Compared to previous measurements in the same rapidity regio…
Search for light charged Higgs bosons decaying to charm and strange quarks in $\mathrm{t\bar{t}}$ events in proton-proton collisions at $\sqrt{s}$ = 13 TeV
EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN)（欧洲核子研究组织（CERN））
One of the outstanding problems in physics is to explain the baryon-anti-baryon asymmetry observed in nature. According to the well-known Sakharov criterion for explaining the observed asymmetry, it is essential that $CP$ violation exist. Even though $CP$ violation has been observed in meson decays and is an integral part of the standard model (SM), measurements in meson decays indicate that $CP$ violation in the SM is insufficient to explain the observed baryon-anti-baryon asymmetry. SM predicts the existence of yet to be observed $CP$ violation in baryon decays. A critical test of the SM req…
It has been recently suggested that the charged charmoniumlike resonances $Z_c(4100)$ and $Z_c(4200)$ are two states of hadrocharmonium, related by the charm quark spin symmetry in the same way as the lowest charmonium states $η_c$ and $J/ψ$. It is pointed out here that in this picture one might expect existence of their somewhat heavier strange counterparts, $Z_{cs}$, decaying to $η_c K$ and $J/ψK$. Some expected properties of such charmoniumlike strange resonances are discussed that set benchmarks for their search in the decays of the strange $B_s$ mesons.
Observation in astronomy suggests that our Universe contains an abundance of matter over antimatter, which can only be explained if the combined CP symmetry is violated. Studies of CP violation have driven the flavor physics with the aim of testing the Standard Model of particle physics and searching for physics beyond. CP violation is discovered in strange, beauty and charm meson systems, however no conclusive sign of CP violation in baryon decays has been observed yet. This review summarizes CP violation studies performed by the LHCb experiment in charmless decays and rare decays of beauty b…
Inclusive semileptonic decays of beauty baryons are studied using the heavy quark expansion to ${\cal O}(1/m_b^3)$, at leading order in $α_s$. The case of a polarized decaying baryon is examined, with reference to $Λ_b$. An extension of the Standard Model effective Hamiltonian inducing $b \to U \ell {\bar ν}_ \ell$ transitions ($U=u,\,c$ and $\ell=e,\,μ,\,τ$) is considered, which comprises the full set of D=6 semileptonic operators with left-handed neutrinos. The effects of the new operators in several observables are described.
A search is conducted for a low-mass charged Higgs boson produced in a top quark decay and subsequently decaying into a charm and a strange quark. The data sample was recorded in proton-proton collisions at $\sqrt{s} =$ 13 TeV by the CMS experiment at the LHC and corresponds to an integrated luminosity of 35.9 fb$^{-1}$. The search is performed in the process of top quark pair production, where one top quark decays to a bottom quark and a charged Higgs boson, and the other to a bottom quark and a W boson. With the W boson decaying to a charged lepton (electron or muon) and a neutrino, the fina…
Using a data sample of $e^+e^-$ collision data corresponding to an integrated luminosity of 108 pb$^{-1}$ collected with the BESIII detector at a center-of-mass energy of 2.125 GeV, we study the process $e^+e^-\rightarrow ϕππ$ and search for a strangeoniumlike structure $Z_s$ decaying into $ϕπ$. No signal is observed in the $ϕπ$ mass spectrum. Upper limits on the cross sections for $Z_s$ production at the 90\% confidence level are determined. In addition, the cross sections of $e^+e^-\rightarrowϕπ^{+}π^{-}$ and $e^+e^-\rightarrowϕπ^{0}π^{0}$ at 2.125 GeV are measured to be $(436.2\pm6.4\pm30.1…
Studies of beauty baryon decays to $D^0 p h^-$ and $Λ_c^+ h^-$ final states
利用LHCb探测器收集的积分光度为1.0 fb $^{-1}$的$pp$碰撞数据样本，研究了美重子衰变到$D^0 p h^-$和$Λ_c^+ h^-$末态（其中$h$表示π介子或K介子）的过程.观察到Cabibbo抑制的衰变$Λ_b^0\to D^0 p K^-$和$Λ_b^0\to Λ_c^+ K^-$，并测量了它们相对于衰变$Λ_b^0\to D^0 p π^-$和$Λ_b^0\to Λ_c^+ π^-$的分支分数。此外，首次观测到中性美奇异重子$Ξ_b^0$衰变到$D^0 p K^-$末态，并测量了$Ξ_b^0$的质量。还报告了$Ξ_b^0\to Λ_c^+ K^-$衰变的证据。
A measurement of the elliptic flow ($v_2$) of prompt J/$ψ$ mesons in high-multiplicity pPb collisions is reported using data collected by the CMS experiment at a nucleon-nucleon center-of-mass energy $\sqrt{s_\mathrm{NN}} =$ 8.16 TeV. Prompt J/$ψ$ mesons decaying into two muons are reconstructed in the rapidity region in the nucleon-nucleon center-of-mass frame ($y_\mathrm{cm}$), corresponding to either $-$2.86 $\lt y_{\mathrm{cm}} <$ $-$1.86 or 0.94 $\lt y_{\mathrm{cm}} <$ 1.94. The average $v_2$ result from the two rapidity ranges is reported over the transverse momentum (p$_\mathrm{T}$) ran…
Search for resonant and nonresonant production of pairs of dijet resonances with b jets in the final state in proton-proton collisions at $\sqrt{s}$ = 13 TeV
EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH (CERN)（欧洲核子研究中心）
The Lambda(1405) baryon resonance plays an outstanding role in various aspects in hadron and nuclear physics. It has been considered that the Lambda(1405) resonance is generated by the attractive interaction of the antikaon and the nucleon, as a quasi-bound state below the threshold decaying into the pi Sigma channel. Thus, the structure of Lambda(1405) is closely related to the Kbar N interaction which is the fundamental ingredient to study few-body systems with antikaon. In this paper, after reviewing the basic properties of the Lambda(1405) resonance, we introduce the dynamical coupled-chan…
The Standard Model of particle physics currently provides our best description of fundamental particles and their interactions. The theory predicts that the different charged leptons, the electron, muon and tau, have identical electroweak interaction strengths. Previous measurements have shown a wide range of particle decays are consistent with this principle of lepton universality. This article presents evidence for the breaking of lepton universality in beauty-quark decays, with a significance of 3.1 standard deviations, based on proton-proton collision data collected with the LHCb detector …
