Lifetime of Doubly Charmed Baryons

In this work, we evaluate the lifetimes of the doubly charmed baryons Ξcc^＋ ,Ξcc^＋＋, and Ωcc^＋. We carefully calculate the non-spectator contributions at the quark level, where the Cabibbo-suppressed diagrams are also included. The hadronic matrix elements are evaluated in the simple non-relativistic harmonic oscillator model. Our numerical results are generally consistent with that obtained by other authors who used the diquark model. However, all the theoretical predictions on the lifetimes are one order larger than the upper limit set by the recent SELEX measurement. This discrepancy would be clarified by the future experiment. If more accurate experiment still confirms the value of the SELEX collaboration, there must be some unknown mechanism to be explored.

Charmed baryons circa 2015

This is essentially an update of Ref. [1] [H. Y. Cheng, Int. J. Mod. Phys. A 24 （Suppl. 1）, 593 （2009）], a review of charmed baryon physics around 2007. Topics covered in this review include the spectroscopy, strong decays, lifetimes, nonleptonic and semileptonic weak decays, and electromagnetic decays of charmed baryons.

Discovery potentials of doubly charmed baryons

The existence of doubly heavy flavor baryons has not been well established experimentally so far. In this Letter we systematically investigate the weak decays of the doubly charmed baryons, Ξ;and Ξ;, which should be helpful for experimental searches for these particles. The long-distance contributions are first studied in the doubly heavy baryon decays, and found to be significantly enhanced. Comparing all the processes, Ξ;→Λ;K;π;π;andΞ;π;are the most favorable decay modes for experiments to search for doubly heavy baryons.

Search for the doubly charmed baryon ■

A search for the doubly charmed baryon ■^+cc is performed through its decay to theΛ^+c K^-π^+ final state,using proton-proton collision data collected with the LHCb detector at centre-of-mass energies of 7,8 and 13 TeV.The data correspond to a total integrated luminosity of 9 fb^-1.No significant signal is observed in the mass range from 3.4 to 3.8 GeV/c^2.Upper limits are set at 95%credibility level on the ratio of the ■^+cc production cross-section times the branching fraction to that ofΛ^+c and ■^++cc baryons.The limits are determined as functions of the ■^+cc mass for different lifetime hypotheses,in the rapidity range from 2.0 to 4.5 and the transverse momentum range from 4 to 15 GeV/c.

CHARMED BARYONS(C=+1)∧_c^+=udc,∑_c^(++)=uuc,∑_c^+=udc,∑_c^0=ddc,≡_c^+=usc,≡_c^0=dsc,Ω_c^0=ssc

CHARMED BARYONS Revised March 2012 by C.G. Wohl （LBNL）. There are 17 known charmed baryons, and four other candidates not well enough established to be promoted to the Summary Tables.＊ Fig. l（a） shows the mass spectrum,

Search for the doubly charmed baryon Ω_(cc)^(+)

A search for the doubly charmed baryon ?cc+ with the decay mode c Ω_(cc)^(+)→ Ξc+K-π+ is performed using proton-proton collision data at a centre-of-mass energy of 13 TeV collected by the LHCb experiment from 2016 to 2018, corresponding to an integrated luminosity of 5.4 fb-1. No significant signal is observed within the invariant mass range of 3.6 to 4.0 GeV/c2. Upper limits are set on the ratio R of the production cross-section times the total branching fraction of the Ω_(cc)^(+)→ Ξc+K-π+ decay with respect to the Ξcc++→ Λc+K-π+π+ decay. Upper limits at 95% credibility level for R in the range 0.005 to 0.11 are obtained for diferent hypotheses on the ?cc+ mass and lifetime in the rapidity range from 2.0 to 4.5 and transverse momentum range from 4 to 15 GeV/c.

Charmed baryon decay asymmetry in e^＋e^- annihilation

We propose to measure the decay asymmetry parameters in the hadronic weak decays of singly charmed baryons, such as Λc^＋ →Λπ^＋, Σ^0π^＋, pK0, Ξ0c →Ξ-π＋and Ω^0c →Ω^-π^＋. The joint angular formulae for these processes are presented, and are used to extract the asymmetry parameters in e^＋e^-annihilation data. Base on the currentΛ＋c data set collected at BESIII, we estimate the experimental sensitivities to measure the parameters αΛπ＋forΛ＋c →Λπ＋, αΣ＋π0for Λc^＋ →Σ＋π^0 and αΣ0π＋for Λc^＋ →Σ^0π^＋.

Charmed baryon resonances with heavy-quark symmetry

We study charmed baryon resonances that are generated dynamically from a coupled-channel unitary approach that implements heavy-quark symmetry. Some states can already be identified with experimental observations, such as Ac（2595）, Ac（2660）, Ec（2902） or Ac（2941）, while others need a compilation of more experimental data as well as an extension of the model to include higher order contributions. We also compare our model to previous SU（4） schemes.

Spectra of charmed and bottom baryons with hyperfine interaction

Up to now, the excited charmed and bottom baryon states have still not been well studied experimentally or theoretically. In this paper, we predict the mass of Ωb, the only L=0 baryon state which has not been observed, to be 6069.2 MeV. The spectra of charmed and bottom baryons with the orbital angular momentum L= 1 are studied in two popular constituent quark models, the Goldstone boson exchange （GBE） model and the one gluon exchange （OGE） hyperfine interaction model. Inserting the latest experimental data from the ＂Review of Particle Physics＂, we find that in the GBE model, there exist some multiplets （∑c（b）, ≡c（b） and Ωc（b）） in which the total spin of the three quarks in their lowest energy states is 3/2, but in the OGE model there is no such phenomenon. This is the most important difference between the GBE and OGE models. These results can be tested in the near future. We suggest more efforts to study the excited charmed and bottom baryons both theoretically and experimentally, not only for the abundance of baryon spectra, but also for determining which hyperfine interaction model best describes nature.

Possible molecular states from interactions of charmed strange baryons

In this study,we investigate possible molecular states composed of two charmed strange baryons from theΞ_(c)^((′,∗))Ξ_(c)^((′,∗))interaction and their hidden-charm hidden-strange partners from theΞ_(c)^((′,∗))Ξ¯_(c)^((′,∗))interaction.With the aid of heavy quark chiral effective Lagrangians,the interactions of charmed strange baryons are described with light meson exchanges.The potential kernels are constructed and inserted into the quasipotential Bethe–Salpeter equation.The bound states are produced from most interactions considered,which suggests that strong attractions exist widely between the charmed strange baryons.Experimental search for these types of molecular states is suggested in future high-precision measurements.

Measurement of the lifetimes of promptly produced Ω_(c)^(0) and Ξ_(c)^(0) baryons

A measurement of the lifetimes of theΩ_(c)^(0)andΞ_(c)^(0)baryons is reported using proton-proton collision data at a centre-of-mass energy of 13 TeV,corresponding to an integrated luminosity of 5.4 fb;collected by the LHCb experiment.TheΩ_(c)^(0)andΞ_(c)^(0)baryons are produced directly from proton interactions and reconstructed in the p K^(-)K^(+)π^(+)nal state.TheΩ_(c)^(0)lifetime is measured to be 276.5±13.4±4.4±0.7 fs,and theΞ_(c)^(0)lifetime is measured to be 148.0±2.3±2.2±0.2 fs,where the first uncertainty is statistical,the second systematic,and the third due to the uncertainty on the D^(0)lifetime.These results con firm previous LHCb measurements based on semileptonic beauty-hadron decays,which disagree with earlier results of a four times shorterΩ_(c)^(0)lifetime,and provide the single most precise measurement of theΩ_(c)^(0)lifetime.

Dipion decays of heavy baryons

Compared with the charmed baryons, the bottom baryons are not very well known, either experimentally Or theoretically. In this paper, we investigate the dipion strong decays of the P-wave and D-wave excited bottom baryons in the framework of the QPC model. We also extend the same analysis to the charmed baryons.

Quark-diquark model description for double charm baryons

We report here the mass spectrum and magnetic moments of ccq（q ∈ u,d,s） systems in the potential model framework by assuming the inter-quark potential as the colour coulomb plus power form with power index ν varying between 0.1 to 2.0.Here the two charm quarks are considered for the diquark states.The conventional one gluon exchange interaction has been employed to get the hyperfine and the fine structure between different states.We have predicted many low-lying states whose experimental verification can exclusively support the quark-diquark structure of the baryons.

J^P assignments of Λ_c^+ baryons

The ＂good＂ diquark is employed to study A＋ baryons within a mass loaded flux tube model. The study indicates that all A＋ baryons candidates in the 2008 review by the Particle Data Group （PDG） are well described in the mass loaded flux model. The quantum numbers JP of these A＋ candidates are assigned. If Ac（2765）＋ is an orbitally excited A＋, it is likely the JP=3/2＋one. If ∧c（2765）＋ is an orbitally excited ∑c, there ought to be another JP=3/2＋∧c＋with mass ≈2770 MeV. In the model, there exists no JP=1/2＋∧c＋（≈2700）predicted in existing literature. Ac （2940）＋ is very possible the orbitally excited baryon with

Λ_c~* in a coupled-channel baryon-meson scattering

Possible structures and properties of some excited states of ∧^＋c dynamically generated in the coupled-channel P-wave meson-baryon scattering are studied by solving the Bethe-Salpeter（BS） equation in the framework of the Chiral Unitary Approach. It is shown that both ∧^＋c（2765） and ∧^＋c（2940） could be generated dynamically and could be compound states with multi-configuration molecular-like structures. The couplings of the generated states to various reaction channels are also calculated. Moreover, two highly excited states, ∧^＋c（3024） and ∧^＋c（3134）, are predicted.

Weak decays of doubly heavy baryons:B_(cc)→BD^(*)

The discovery of Ξ_(cc)^(++)has inspired new interest in studying doubly heavy baryons.In this study,the weak decays of a doubly charmed baryon B_(cc)to a light baryon B and a charm meson D^(*)(either a pseudoscalar or a vector one)are calculated.Following our previous work,we calculate the short distance contributions under the factorization hypothesis,whereas the long distance contributions are modeled as the final state interactions,which are calculated with the one particle exchange model.We find that the B_(cc)→BD^(*)decays'branching ratios are obviously larger,as they receive contributions of more polarization states.Among the decays that we investigate,the following have the largest branching fractions:BR(Ξ_(cc)^(++)→∑^(+)D^(*+))∈[0.46%,3.33%]estimated with τΞ_(cc)^(++)=256 fs;BR(Ξ_(cc)^(+)→AD^(*+))∈[0.38%,2.63%]and BR(Ξ_(cc)^(+)→∑^(0)D^(*+))∈[0.45%,3.16%]with τΞ_(cc)^(++)=45 fs;and BR(Ω_(cc)^(+)→Ξ^(0)D^(+))∈[0.27%,1.03%),BR(Ω_(cc)^(+)→∑^(0)D^(*+))∈[0.07%,0.44%],and BR(Ω_(cc)^(+)→∑^(0)D^(*+))∈[0.06%,0.45%] with τ_(Ω_(cc))^(+)=75 fs.By comparing the decay widths of pure color commensurate channels with those of pure bow-tie ones we find that the bow-tie mechanism plays an important role in charm decays.

Measurement of Ξcc++ production in pp collisions at s1/2=13 TeV

The production of ■baryons in proton-proton collisions at a centre-of-mass energy of √s = 13 TeV is measured in the transverse-momentum range 4<pT<15GeV/c and the rapidity range2.0<y<4.5.The data used in this measurement correspond to an integrated luminosity of 1.7fb^-1,recorded by the LHCb experiment during 2016.The ratio of the ■ production cross-section times the branching fraction of the■→∧^+cK^-π^+ π^+decay relative to the prompt ∧^+c production cross-section is found to be(2.22±0.27±0.29)×10^-4,assuming the central value of the measured lifetime,where the first uncertainty is statistical and the second systematic.

Λ_(c)^(+)→Λh^(+)和Λc+→∑^(0)h^(+)(h=K,π)衰变道CP破坏的寻找和其分支比与衰变不对称参数的测量

本文报告了粲重子Λ_(c)^(+)的四个弱衰变道Λ_(c)^(+)→Λh^(+)和Λ_(c)^(+)→∑^(0)h^(+)(h=K,π)的系列研究.基于在KEKB能量不对称的正负电子对撞机上的Belle探测器收集的980 fb-1数据样本,作者测量了粲重子两体单卡比玻压低(SCS)衰变过程中的直接电荷共轭-宇称(CP)不对称:ACPdir(Λ_(c)^(+)→ΛK^(+))=+0.021±0.026±0.001和ACPdir(Λ_(c)^(+)→∑^(0)K^(+))=+0.025±0.054±0.004;精确测量了衰变不对称参数(α)和其引起的CP不对称度:AC^(α)_(P)(Λ_(c)^(+)→ΛK^(+))=-0.023±0.086±0.071和AC^(α)_(P)(Λ_(c)^(+)→∑^(0)K^(+))=+0.08±0.035±0.14.这是粲重子SCS衰变的第一个AC^(α)_(P)结果;其次,作者在实验上利用粲重子衰变来寻找超子CP破坏,即利用Λ_(c)^(+)→(Λ,∑^(0))π^(+)衰变获得AC^(α)_(P)(Λ→pπ-)=+0.013±0.007±0.011.以上测量均未发现重子CP破坏的证据.此外,该文还报告了Λ_(c)^(+)两个SCS衰变道的分支比测量:B(Λ_(c)^(+)-ΛK^(+))=(6.57±0.17±0.11±0.35)×10^(-4)和B(Λ_(c)^(+)→∑^(0)K^(+))=(3.58±0.19±0.06±0.19)×10^(-4),这些均为目前最精确的结果.

Exotic pentaquarks as Gamov-Teller resonances

If the number of colors N c is taken large,baryons and their excitations can be considered in a mean-field approach.We argue that the mean field in baryons breaks spontaneously the spherical and SU（3） flavor symmetries,but retains the SU（2） symmetry of simultaneous rotations in space and isospace.The one-quark and quark-hole excitations in the mean field,together with the SU（3） rotational bands about them determine the spectrum of baryon resonances,which turns out to be in good accordance with reality when one puts N c =3.A by-product of this scheme is a confirmation of the light pentaquark Θ ＋ baryon uudds as a typical Gamov–Teller resonance long known in nuclear physics.An extension of the same large-N c logic to charmed baryons leads to a prediction of a anti-decapenta （15）-plet of charmed pentaquarks,two of which,B ＋＋ c = cuuds and B ＋ c = cudds,may be light and stable with respect to strong decays.

Polarization in ■ decays

Measurements of decay asymmetry parameters of charmed baryons,e.g.,■,provide more data to test the W-emission and W-exchange mechanisms controlled by strong and weak interactions.Taking advantage of the spin polarization in charmed baryon decays,we investigate the possibility to measure weak decay asymmetry parameters in thee^+e^-→■ process.We analyze the transverse polarization spontaneously produced in this process and the spin transfer in the subsequent■ decays.The sensitivity to measure the asymmetry parameters is estimated for the decay■→■.