SEARCH FOR A THRESHOLD ENHANCEMENT IN THE γ P → CHARMED BARYON + CHARMED MESON CROSS-SECTION
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Abe, K.↗
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Search for doubly charmed baryons and study of charmed strange baryons at Belle
We report results of a study of doubly charmed baryons and charmed strange baryons. The analysis is performed using a 980 fb –1 data sample collected with the Belle detector at the KEKB asymmetric-energy e + e – collider. Here, we search for doubly charmed baryons Ξ$^{+(+)}_{cc}$ with the Λ$^{+}_{c}$K – π + (π + ) and Ξ$^{0}_{c}$π + (π + ) final states. No significant signal is observed. We also search for two excited charmed strange baryons, Ξ c (3055) + and Ξ c (3123) + with the Σ$^{++}_{c}$(2455)K – and Σ$^{++}_{c}$(2520)K – final states. Here, the Ξ c (3055) + signal is observed with a significance of 6.6 standard deviations including systematic uncertainty, while no signature of the Ξ c (3123) + is seen. We also study properties of the Ξ c (2645) + and measure a width of 2.6 ± 0.2(stat) ± 0.4(syst) MeV/c 2 , which is the first significant determination.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Multiplicity dependence of charm baryon and charm meson production in pPb collisions at $\sqrt{s_{NN}} = 8.16$ TeV
Measurements of the production yields of charm baryons (Λ$^+_c$ ) and charm mesons (D 0 ) in proton-lead collisions at a nucleon-nucleon center-of-mass energy of 8.16 TeV are presented. The data were collected in 2016 with the CMS experiment and correspond to an integrated luminosity of 186 nb -1 . The Λ$^+_c$ baryon is reconstructed from the decay channel Λ$^+_c$ → K$^0_S$p , while the D 0 meson is reconstructed via D 0 → K - π + . The Λ$^+_c$ baryon and D 0 meson yields are extracted in several charged-particle multiplicity classes. No strong multiplicity dependence of the Λ$^+_c$-to-D 0 yield ratio is observed, unlike the observed strange baryon to strange meson yield ratio of $Λ/\bar{Λ}$to K$^0_S$, which shows a strong multiplicity dependence. This observation indicates different mechanisms for the multiplicity evolution of hadronization processes for charm and strange quarks and provides new constraints to the understanding of heavy flavor production and collectivity in small collision systems.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Spectroscopy of doubly charmed baryons from lattice QCD
This study presents the ground and excited state spectra of doubly charmed baryons from lattice QCD with dynamical quark fields. Calculations are performed on anisotropic lattices of size 16³ × 128, with inverse spacing in temporal direction a t ⁻¹=5.67(4) GeV and with a pion mass of about 390 MeV. A large set of baryonic operators that respect the symmetries of the lattice yet which retain a memory of their continuum analogues are used. These operators transform as irreducible representations of SU(3) F symmetry for flavor, SU(4) symmetry for Dirac spins of quarks and O(3) for spatial symmetry. The distillation method is utilized to generate baryon correlation functions which are analyzed using the variational fitting method to extract excited states. The lattice spectra obtained have baryonic states with well-defined total spins up to 7/2 and the pattern of low-lying states does not support the diquark picture for doubly charmed baryons. On the contrary the calculated spectra are remarkably similar to the expectations from models with an SU(6)×O(3) symmetry. Various spin-dependent energy splittings between the extracted states are also evaluated.
Padmanath, M.↗
First Observation of the Doubly Cabibbo-Suppressed Decay of a Charmed Baryon: Λ c + → p K + π -
We report the first observation of the decay Λ c + → p K + π - using a 980 fb - 1 data sample collected by the Belle detector at the KEKB asymmetric-energy e + e - collider. This is the first observation of a doubly Cabibbo-suppressed decay of a charmed baryon. We measure the branching ratio of this decay with respect to its Cabibbo-favored counterpart to be B ( Λ c + → p K + π - ) / B ( Λ c + → p K - π + ) = ( 2.35 ± 0.27 ± 0.21 ) × 10 - 3 , where the uncertainties are statistical and systematic, respectively.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Spectroscopy of charmed baryons
Apresent-day classification of charmed baryons is presented, a quark model for ground states is briefly described, and the energy levels of excited states are analyzed. In addition, a survey of experimentally observed states of charmed baryons is given.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Charmed baryons in electron-positron collisions
Charmed baryons are classified, and the experimental data on charmed-baryon states are reviewed paying special attention to those obtained at the electron-positron colliders.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Charm-baryon semileptonic decays and the strange Λ * resonances: New insights from lattice QCD
Not Available
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Charm Baryon Results from BaBar
We present experimental results from the BaBar experiment on charm baryon spectroscopy and production studies, including studies of excited cascades produced in charm baryon decays. We review the discovery of new decay modes of known states and searches for predicted states.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Study of strange charmed baryons in electron–positron collisions
A modern classification of charmed baryons is presented, and the quark model is briefly described for the ground states and energy levels of excited states. In addition, a survey of experimentally observed states of strange charmed baryons is given.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Possible molecular bound state of two charmed baryons
One-boson-exchange approach is widely used in the study of baryon-baryon interactions. Because of the higher masses, charmed baryons are likely to form molecular bound states. We here investigate this possibility in the {Lambda}{sub c{Lambda}c}(J{sup P} = 0{sup +}, I = 0) system, which may be the lowest mass state composed of two charmed baryons. Since the long-range interactions must play an important role for the formation of possible molecular bound states, we consider the one-pion-exchange potential explicitly and embed the short-range effects into a phenomenological cutoff parameter. As single pion exchange does not occur between two {Lambda}{sub c}'s, couplings to the nearby {Sigma}{sub c{Sigma}c}, {Sigma}{sub c{Sigma}c}* and {Sigma}{sub c}*{Sigma}{sub c}{sup *} channels may be crucial in binding two {Lambda}{sub c}'s. We find that it is possible to have a molecular bound state of two {Lambda}{sub c}'s, where the tensor force plays a crucial role, although the predicted binding energies are sensitive to the cutoff parameter.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Charm Baryon Results from BaBar
We present experimental results from the BaBar experiment on charm baryon spectroscopy and production studies, including studies of excited cascades produced in charm baryon decays. We review the discovery of new decay modes of known states and searches for predicted states.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Intrinsic charm production of doubly charmed baryons: Collider vs. fixed-target
We report the LHCb Collaboration has measured the doubly charmed baryon, $\Xi^{++}_{cc} (ucc)$, through two different decay channels in $p + p$ collisions at center-of-mass energies of 7, 8 and 13 TeV. While they have performed similar searches for the doubly charmed baryon $\Xi^{+}_{cc} (dcc)$, it has not yet been observed by LHCb. However, the fixed-target experiment, SELEX, at Fermilab, reported the observation of the $\Xi^{+}_{cc}$ in two different decay channels with a 600 GeV charged hyperon beam. The beam was composed of an admixture of $π^{±}, p, \overline p $ components as well as the $Σ^–$ hyperon. Much discussion has arisen over the fact that the fixed-target observations have not been easily reproduced by the collider experiments at higher energies, where one might have expected the production rates to be much higher due to the orders of magnitude increase in the center of mass energy with LHCb.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Spectroscopy of doubly and triply-charmed baryons from lattice QCD
We present the ground and excited state spectra of doubly and triply-charmed baryons by using lattice QCD with dynamical clover fermions. A large set of baryonic operators that respect the symmetries of the lattice and are obtained after subduction from their continuum analogues are utilized. Using novel computational techniques correlation functions of these operators are generated and the variational method is exploited to extract excited states. The lattice spectra that we obtain have baryonic states with well-defined total spins up to 7/2 and the low lying states remarkably resemble the expectations of quantum numbers from SU(6) Ⓧ O(3) symmetry. Various energy splittings between the extracted states, including splittings due to hyperfine as well as spin-orbit coupling, are considered and those are also compared against similar energy splittings at other quark masses. Using those splittings for doubly-charmed baryons, and taking input of experimental Bc meson mass, we predict the mass splittings of B*c-Bc to be about 80 ± 8 MeV and mΩccb=8050±10 MeV.
Padmanath, M.↗
Magnetic moments of charmed baryons. I, II
The magnetic moments of all charmed baryons belonging to the totally symmetric 20 (underlined) representation, the mixed symmetry 20 prime (underlined) and the totally antisymmetric 4 (underlined) representation have been compared under U(4) symmetry, assuming that the magnetic-moment operator is proportional to the charge operator. The magnetic moments of all charmed particles have been expressed in terms of the moments of proton, neutron and delta particles in the case of U(4) symmetry. Then assuming that the magnetic moment operator is a tensor transforming as the (15,3) members of a 63 (underlined) representation of U(8) or SU(8), the magnetic moments of all the baryons belonging to the 120 (underlined) representation are compared.
Choudhury, A. L.↗
Search for the doubly charmed baryon $\Xi_{cc}^+$
A search for the doubly charmed baryon $\Xi_{cc}^+$ is performed through its decay to the $Λ$ $^{+}_{c}$ 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 $\Xi_{cc}^+$ production cross-section times the branching fraction to that of $Λ$ $^{+}_{c}$ and $\Xi_{cc}^{++}$ baryons. The limits are determined as functions of the $\Xi_{cc}^+$ 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.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Spectroscopy of charmed baryons from lattice QCD
We present the ground and excited state spectra of singly, doubly and triply charmed baryons by using dynamical lattice QCD. A large set of baryonic operators that respect the symmetries of the lattice and are obtained after subduction from their continuum analogues are utilized. Using novel computational techniques correlation functions of these operators are generated and the variational method is exploited to extract excited states. The lattice spectra that we obtain have baryonic states with well-defined total spins up to 7/2 and the low lying states remarkably resemble the expectations of quantum numbers from SU(6) x O(3) symmetry. Various energy splittings between the extracted states, including splittings due to hyperfine as well as spin-orbit coupling, are considered and those are also compared against similar energy splittings at other quark masses.
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
Spectroscopy of triply charmed baryons from lattice QCD
The spectrum of excitations of triply-charmed baryons is computed using lattice QCD including dynamical light quark fields. The spectrum obtained has baryonic states with well-defined total spin up to 7/2 and the low-lying states closely resemble the expectation from models with an SU(6) x O(3) symmetry. As a result, energy splittings between extracted states, including those due to spin-orbit coupling in the heavy quark limit are computed and compared against data at other quark masses.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗