The lattice QCD simulation of NJ/ψ and Nηc scattering is performed at mπ 266 MeV in channels with all possible JP. This includes JP=3/2± and 5/2± where LHCb discovered Pc(4380) and Pc(4450) ...pentaquark states in proton-J/ψ decay. This is the first lattice simulation that reaches the energies 4.3–4.5 GeV where pentaquarks reside. Several decay channels are open in this energy region, and we explore the fate of Pc in the one-channel approximation in this work. Energies of eigenstates are extracted for the nucleon-charmonium system at zero total momentum for all quantum numbers, i.e., six lattice irreducible representations. No significant energy shifts are observed. The number of the observed lattice eigenstates agrees with the number expected for noninteracting charmonium and nucleon. Thus, we do not find any strong indication for a resonance or a bound state in these exotic channels within one-channel approximation. This possibly indicates that the coupling of the NJ/ψ channel with other two-hadron channels might be responsible for Pc resonances in experiment. One of the challenges of this study is that up to six degenerate J/ψ(p)N(−p) eigenstates are expected in the noninteracting limit due nonzero spins of J/ψ and N, and we establish all of them in the spectra.
We present a lattice QCD study of Nπ scattering in the positive-parity nucleon channel, where the puzzling Roper resonance N*(1440) resides in experiment. The study is based on the PACS-CS ensemble ...of gauge configurations with Nf=2+1 Wilson-clover dynamical fermions, mπ≃156 MeV and L≃2.9 fm. In addition to a number of qqq interpolating fields, we implement operators for Nπ in p-wave and Nσ in s-wave. In the center-of-momentum frame we find three eigenstates below 1.65 GeV. They are dominated by N(0), N(0)π(0)π(0) mixed with N(0)σ(0) and N(p)π(−p) with p≃2π/L, where momenta are given in parentheses. This is the first simulation where the expected multi-hadron states are found in this channel. The experimental Nπ phase shift would-in the approximation of purely elastic Nπ scattering-imply an additional eigenstate near the Roper mass mR≃1.43 GeV for our lattice size. We do not observe any such additional eigenstate, which indicates that Nπ elastic scattering alone does not render a low-lying Roper. Coupling with other channels, most notably with Nππ, seems to be important for generating the Roper resonance, reinforcing the notion that this state could be a dynamically generated resonance. Our results are in line with most of the previous lattice studies based just on qqq interpolators, which did not find a Roper eigenstate below 1.65 GeV. The study of the coupled-channel scattering including a three-particle decay Nππ remains a challenge.
We perform a reanalysis of the energy levels obtained in a recent lattice QCD simulation, from where the existence of bound states of KD and KD are induced and identified with the narrow D s0 (2317) ...and D s1 (2460) resonances. The reanalysis is done in terms of an auxiliary potential, employing a single-channel basis KD, and a two-channel basis KD, eta D s super(()). By means of an extended Luescher method we determine poles of the continuum t-matrix, bound by about 40 MeV with respect to the KD and KD thresholds, which we identify with the D s0 (2317) and D s1 (2460) resonances. Using a sum rule that reformulates Weinberg compositeness condition we can determine that the state D s0 (2317) contains a KD component in an amount of about 70%, while the state D s1 (2460) contains a similar amount of KD . We argue that the present lattice simulation results do not still allow us to determine which are the missing channels in the bound state wave functions and we discuss the necessary information that can lead to answer this question.
Two Zb hadrons with exotic quark structure b¯bd¯u were discovered by Belle experiment. We present a lattice QCD study of the b¯bd¯u system in the approximation of static b quarks, where the total ...spin of heavy quarks is fixed to one. The energies of eigenstates are determined as a function of the separation r between b and b¯. The lower eigenstates are related to a bottomonium and a pion. The eigenstate dominated by BB¯⁎ has energy significantly below mB+mB⁎, which points to a sizable attraction for small r. The attractive potential V(r) between B and B¯⁎ is extracted assuming that this eigenstate is related exclusively to BB¯⁎. The Schrödinger equation for BB¯⁎ within the extracted potential leads to one bound state below BB¯⁎ threshold, whose mass depends on the parametrization of the lattice potential. For certain parametrizations, the bound state is very close to the BB¯⁎ threshold and renders a narrow peak in the BB¯⁎ rate above threshold - these features could be related to Zb(10610) in the experiment.
Based on a complete set of J = 0 and J = 1 spatial isovector correlation functions calculated with NF = 2 domain wall fermions we identify an intermediate temperature regime of T~220–500 MeV ...(1.2Tc–2.8Tc), where chiral symmetry is restored but the correlators are not yet compatible with a simple free quark behavior. More specifically, in the temperature range T~220–500 MeV we identify a multiplet structure of spatial correlators that suggests emergent SU(2)CS and SU(4) symmetries, which are not symmetries of the free Dirac action. The symmetry breaking effects in this temperature range are less than 5%. Our results indicate that at these temperatures the chromomagnetic interaction is suppressed and the elementary degrees of freedom are chirally symmetric quarks bound into color-singlet objects by the chromoelectric component of the gluon field. At temperatures between 500 and 660 MeV the emergent SU(2)CS and SU(4) symmetries disappear and one observes a smooth transition to the regime above T~1 GeV where only chiral symmetries survive, which are finally compatible with quasifree quarks.
A
bstract
We perform a reanalysis of the energy levels obtained in a recent lattice QCD simulation, from where the existence of bound states of
KD
and
KD
∗
are induced and identified with the narrow
...D
s
0
∗
(2317) and
D
s
1
∗
(2460) resonances. The reanalysis is done in terms of an auxiliary potential, employing a single-channel basis
KD
(
∗
), and a two-channel basis
KD
(
∗
),
ηD
s
(∗)
. By means of an extended Lüscher method we determine poles of the continuum
t
-matrix, bound by about 40 MeV with respect to the
KD
and
KD
∗
thresholds, which we identify with the
D
s
0
∗
(2317) and
D
s
1
∗
(2460) resonances. Using a sum rule that reformulates Weinberg compositeness condition we can determine that the state
D
s
0
∗
(2317) contains a
KD
component in an amount of about 70%, while the state
D
s
1
∗
(2460) contains a similar amount of
KD
∗
. We argue that the present lattice simulation results do not still allow us to determine which are the missing channels in the bound state wave functions and we discuss the necessary information that can lead to answer this question.
We study spatial isovector meson correlators in Nf=2 QCD with dynamical domain-wall fermions on 323×8 lattices at temperatures T=220–380 MeV. We measure the correlators of spin-one (J=1) operators ...including vector, axial-vector, tensor and axial-tensor. Restoration of chiral U(1)A and SU(2)L×SU(2)R symmetries of QCD implies degeneracies in vector–axial-vector (SU(2)L×SU(2)R) and tensor–axial-tensor (U(1)A) pairs, which are indeed observed at temperatures above Tc. Moreover, we observe an approximate degeneracy of all J=1 correlators with increasing temperature. This approximate degeneracy suggests emergent SU(2)CS and SU(4) symmetries at high temperatures, that mix left- and right-handed quarks.
A
bstract
We construct operators for simulating the scattering of two hadrons with spin on the lattice. Three methods are shown to give the consistent operators for
P N
,
P V
,
V N
and
N N
...scattering, where
P
,
V
and
N
denote pseudoscalar, vector and nucleon. Explicit expressions for operators are given for all irreducible representations at lowest two relative momenta. Each hadron has a good helicity in the first method. The hadrons are in a certain partial wave
L
with total spin
S
in the second method. These enable the physics interpretations of the operators obtained from the general projection method. The correct transformation properties of the operators in all three methods are proven. The total momentum of two hadrons is restricted to zero since parity is a good quantum number in this case.
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