ON THE ABSENCE OF PENTAQUARK STATES FROM DYNAMICS IN STRONGLY COUPLED LATTICE QCD

2011 ◽  
Vol 26 (01) ◽  
pp. 71-133 ◽  
Author(s):  
PAULO A. FARIA DA VEIGA ◽  
MICHAEL O'CARROLL ◽  
ANTÔNIO FRANCISCO NETO ◽  
PETRUS H. R. DOS ANJOS
Keyword(s):  
Lattice Qcd ◽  
Bound States ◽  
Threshold Value ◽  
Negative Energy ◽  
Functional Integral ◽  
Ladder Approximation ◽  
Exchange Potential ◽  
Strong Coupling Regime ◽  
Strongly Coupled ◽  
Spinless Case

We consider an imaginary time functional integral formulation of a two-flavor, 3+1 lattice QCD model with Wilson's action and in the strong coupling regime (with a small hopping parameter, κ > 0, and a much smaller plaquette coupling, [Formula: see text], so that the quarks and glueballs are heavy). The model has local SU (3)c gauge and global SU (2)f flavor symmetries, and incorporates the corresponding part of the eightfold way particles: baryons (mesons) of asymptotic mass ≈-3 ln κ(≈-2 ln κ). We search for pentaquark states as meson–baryon bound states in the energy–momentum spectrum of the model, using a lattice Bethe–Salpeter equation. This equation is solved within a ladder approximation, given by the lowest nonvanishing order in κ and β of the Bethe–Salpeter kernel. It includes order κ2 contributions with a [Formula: see text] exchange potential together with a contribution that is a local-in-space, energy-dependent potential. The attractive or repulsive nature of the exchange interaction depends on the spin of the meson–baryon states. The Bethe–Salpeter equation presents integrable singularities, forcing the couplings to be above a threshold value for the meson and the baryon to bind in a pentaquark. We analyzed all the total isospin sectors, I = 1/2, 3/2, 5/2, for the system. For all I, the net attraction resulting from the two sources of interaction is not strong enough for the meson and the baryon to bind. Thus, within our approximation, these pentaquark states are not present up to near the free meson–baryon energy threshold of ≈-5 ln κ. This result is to be contrasted with the spinless case for which our method detects meson–baryon bound states, as well as for Yukawa effective baryon and meson field models. A physical interpretation of our results emerges from an approximate correspondence between meson–baryon bound states and negative energy states of a one-particle lattice Schrödinger Hamiltonian.

ISOSPIN–SPIN INTERCHANGE SYMMETRY AND TWO-BARYON BOUND STATES IN (3+1)-DIMENSIONAL LATTICE QCD WITH TWO-FLAVORS AND STRONG COUPLING

2011 ◽  
Vol 26 (25) ◽  
pp. 4387-4404
Author(s):  
PAULO A. FARIA DA VEIGA ◽  
MICHAEL O'CARROLL ◽  
ANTÔNIO FRANCISCO NETO
Keyword(s):  
Binding Energy ◽  
Lattice Qcd ◽  
Strong Coupling ◽  
Bound States ◽  
Spin Symmetry ◽  
Exchange Potential ◽  
Strong Coupling Regime ◽  
Spectral Structure ◽  
Lattice Action ◽  
Baryon Spectrum

We determine two-baryon bound states in a 3+1 lattice QCD model with improved Wilson action and two flavors. We work in the strong coupling regime: small hopping parameter κ > 0 and much smaller plaquette coupling β > 0. In this regime, it is known that the low-lying energy–momentum spectrum is comprised of baryons and mesons with asymptotic masses -3 ln κ and -2 ln κ, respectively. We show that the dominant baryon–baryon interaction is an order κ2 space-range-one [Formula: see text]-exchange potential. We also show that this interaction has an important and novel isospin–spin interchange symmetry relating the various possible bound states, and then governing the two-baryon spectral structure. Letting S(I) denote the total spin (total isospin) of the two-baryon bound states, S, I = 0, 1, 2, 3, we find bound states with asymptotic binding energy κ2/4, for I+S = 1, 3, and 4 (here, with I = S = 2); κ2/12, for I+S = 0, 2, 4 and 3 (here, with I = 1, 2). In particular, we show that the two-baryon spectrum contains deuteron (I = 0), diproton (I = 1) and dineutron (I = 1)-like bound states. Using the isospin–spin symmetry, we can circumvent the lack of spin symmetry of the lattice action and show they all have the same asymptotic binding energy, namely κ2/4. Our analysis uses convenient two and four-baryon correlations, their spectral representations and a lattice Bethe–Salpeter equation, which is solved in a ladder approximation. For the isospin, spin part of the interaction, we obtain a permanent representation which describes the interaction of the individual spins and isospins of the quarks of one baryon with those of the other baryon.

Baryon-baryon bound states in strongly coupled lattice QCD

2007 ◽  
Vol 75 (7) ◽  
Author(s):  
Paulo A. Faria da Veiga ◽  
Michael O’Carroll
Keyword(s):  
Lattice Qcd ◽  
Bound States ◽  
Strongly Coupled

EXACT DYNAMICAL EIGHTFOLD WAY BARYON SPECTRUM AND CONFINEMENT IN STRONGLY COUPLED LATTICE QCD

2009 ◽  
Vol 24 (16n17) ◽  
pp. 3053-3072 ◽  
Author(s):  
PAULO A. FARIA DA VEIGA ◽  
MICHAEL O'CARROLL
Keyword(s):  
Lattice Qcd ◽  
Rotational Symmetry ◽  
Mass Difference ◽  
Dispersion Curves ◽  
Momentum Spectrum ◽  
Functional Integral ◽  
Strong Coupling Regime ◽  
Partial Restoration ◽  
Baryon Spectrum ◽  
The Masses

We obtain from the quark–gluon dynamics the eightfold way baryon spectrum exactly in an imaginary time functional integral formulation of 3+1 lattice QCD with Wilson's action in the strong coupling regime (small hopping parameter 0 < κ ≪ 1 and much smaller plaquette coupling [Formula: see text]). The model has SU(3)c local gauge and global SU(3)f flavor symmetries. A decoupling of the hyperplane method naturally unveils the form of the baryon composite fields. In the subspace of the physical Hilbert space of vectors with an odd number of quarks, the baryons are associated with isolated dispersion curves in the energy–momentum spectrum. Spectral representations are derived for the two-baryon correlations, which allow us to detect the energy–momentum spectrum and particles as complex momentum space singularities. The spin 1/2 octet and spin 3/2 decuplet baryons have asymptotic mass -3ln κ and for each baryon there is an antibaryon with identical spectral properties. An auxiliary function method is used to obtain convergent expansions for the masses after subtracting the singular part -3ln κ. The nonsingular part of the mass is analytic in κ and β, i.e. the expansions are controlled to all orders. For β = 0, all the masses have the form M = -3ln κ - 3κ3/4 + κ6r(κ), with r(κ) real analytic. Although we have no Lorentz symmetry in our lattice model, we show that there is a partial restoration of the continuous rotational symmetry at zero spatial momentum, which implies that for all members of the octet (decuplet) r(κ) is the same. So, there is no mass splitting within the octet and within the decuplet. However, there is an octet–decuplet mass difference of [Formula: see text] at β = 0; the splitting persists for β ≠ 0. We also obtain the (anti)baryon dispersion curves which admit the representation [Formula: see text], where [Formula: see text] and [Formula: see text] is of [Formula: see text]. For the octet, [Formula: see text] is jointly analytic in κ and in each pj, for small [Formula: see text]. A new local symmetry, which we call spin flip, is used to establish constraints for the matrix-valued two-baryon correlation and show that all the octet dispersion curves are the same and that the four decuplet dispersion curves are pairwise-identical and depend only on the modulus of the spin z-component. Using a correlation subtraction method we show that the spectrum generated by the baryon and antibaryon fields is the only spectrum, in the odd quark subspace of physical states, up to near the baryon–meson threshold of ≈ -5ln κ. Combining this result with a similar result for the mesons, with mass ≈ -2ln κ, shows that the only spectrum in the entire space of states, up to near the two-meson threshold of ≈ -4ln κ, is generated by the eightfold way hadrons. Hence, for 0 < κ ≪ β ≪ 1, we have shown confinement up to near this threshold.

Meson-meson bound states in a(2+1)-dimensional strongly coupled lattice QCD model

2004 ◽  
Vol 69 (9) ◽  
Author(s):  
Paulo A. Faria da Veiga ◽  
Michael O’Carroll ◽  
Antônio Francisco Neto
Keyword(s):  
Lattice Qcd ◽  
Bound States ◽  
Strongly Coupled

Analytic Binding Energies for Two-Baryon Bound States in 2 + 1 Strongly Coupled Lattice QCD With Two-Flavors

2013 ◽  
Vol 321 (1) ◽  
pp. 249-282 ◽  
Author(s):  
Michael O’Carroll ◽  
Paulo A. Faria da Veiga ◽  
Antônio Francisco Neto
Keyword(s):  
Lattice Qcd ◽  
Bound States ◽  
Binding Energies ◽  
Strongly Coupled

scholarly journals Isospin-1/2 Dπ scattering and the lightest $$ {D}_0^{\ast } $$ resonance from lattice QCD

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Luke Gayer ◽  
Nicolas Lang ◽  
Sinéad M. Ryan ◽  
David Tims ◽  
Christopher E. Thomas ◽  
...  
Keyword(s):  
Scattering Amplitudes ◽  
Lattice Qcd ◽  
Quark Mass ◽  
Light Quark ◽  
Energy Levels ◽  
Experimental Result ◽  
Infinite Volume ◽  
Resonance Pole ◽  
Strongly Coupled ◽  
Light Quark Mass

Abstract Isospin-1/2 Dπ scattering amplitudes are computed using lattice QCD, working in a single volume of approximately (3.6 fm)3 and with a light quark mass corresponding to mπ ≈ 239 MeV. The spectrum of the elastic Dπ energy region is computed yielding 20 energy levels. Using the Lüscher finite-volume quantisation condition, these energies are translated into constraints on the infinite-volume scattering amplitudes and hence enable us to map out the energy dependence of elastic Dπ scattering. By analytically continuing a range of scattering amplitudes, a $$ {D}_0^{\ast } $$ D 0 ∗ resonance pole is consistently found strongly coupled to the S-wave Dπ channel, with a mass m ≈ 2200 MeV and a width Γ ≈ 400 MeV. Combined with earlier work investigating the $$ {D}_{s0}^{\ast } $$ D s 0 ∗ , and $$ {D}_0^{\ast } $$ D 0 ∗ with heavier light quarks, similar couplings between each of these scalar states and their relevant meson-meson scattering channels are determined. The mass of the $$ {D}_0^{\ast } $$ D 0 ∗ is consistently found well below that of the $$ {D}_{s0}^{\ast } $$ D s 0 ∗ , in contrast to the currently reported experimental result.

INDICATIONS OF A ΔI=1/2 RULE IN THE STRONG COUPLING REGIME

1988 ◽  
Vol 03 (06) ◽  
pp. 1385-1412
Author(s):  
IAN G. ANGUS
Keyword(s):  
Lattice Qcd ◽  
Strong Coupling ◽  
Computer Algebra ◽  
Free Parameter ◽  
Hamiltonian Formalism ◽  
Strong Coupling Expansion ◽  
Calculation Scheme ◽  
Strong Coupling Regime ◽  
Weak Decays ◽  
The One

We will attempt to understand the ΔI=1/2 pattern of the nonleptonic weak decays of the kaons. The calculation scheme employed is the Strong Coupling Expansion of lattice QCD. Kogut-Susskind fermions are used in the Hamiltonian formalism. We will describe in detail the methods used to expedite this calculation, all of which was done by computer algebra. The final result is very encouraging. Even though an exact interpretation is clouded by the presence of irrelevant operators, and questions of lattice artifacts, a signal of the ΔI=1/2 rule appears to be observable. With an appropriate choice of the one free parameter, enhancements greater than those observed experimentally can be obtained. We also point out a number of surprising results which we turn up in the course of the calculation.

Dynamical eightfold way mesons in strongly coupled lattice QCD

2008 ◽  
Vol 77 (5) ◽  
Author(s):  
Antônio Francisco Neto ◽  
Michael O’Carroll ◽  
Paulo A. Faria da Veiga
Keyword(s):  
Lattice Qcd ◽  
Strongly Coupled
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