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the complexity of quantum chromodynamics ( qcd ) , the quantum field theory of the strong interaction , has prevented so far a rigorous deduction of its predictions even for the simplest hadronic systems . in the meantime while lattice qcd starts providing reliable results , qcd - inspired models are useful tools to get some insight into many of the phenomena of the hadronic world .
one of the central issues to be addressed is a quantitative description of the low - energy phenomena , from the baryon - baryon interaction to the baryon spectra , still one of the major challenges in hadronic physics .
nowadays , we have at our disposal realistic quark models accounting for most part of the one- and two - body low - energy hadron phenomenology . among the quark models found in the literature@xcite
, the ambitious project of a simultaneous description of the baryon - baryon interaction and the hadron spectra in all the flavor sectors has only been undertaken by the constituent quark model of ref.@xcite .
the success in describing the properties of the strange and non - strange one and two - hadron systems encourages its use as a guideline in order to assign parity and spin quantum numbers to already determined baryon states as well as to predict still non - observed resonances .
the results we are going to present have been obtained by solving exactly the schrdinger equation by the faddeev method in momentum space .
the results are of similar quality to others present in the literature based on models specifically designed for the study of the baryon spectra@xcite . in the constituent quark model used in this work
the hyperfine splitting is shared between pseudoscalar forces and perturbative qcd contributions , provided by the one - gluon exchange . in table [ t2 ]
we give the contribution of different pieces of the interacting hamiltonian to the energy of several octet and decuplet baryons .
one observes that the hyperfine splittings are controlled by the one - gluon exchange ( oge ) and one - pion exchange ( ope ) [ one - kaon exchange ( oke ) ] potentials in the non - strange [ strange ] sector .
the oge and ope generate almost the experimental hyperfine splitting , the one - eta ( oee ) and one - sigma exchange ( ose ) given a final small tune .
the expectation value of the ope flavor operator for two light quarks is replaced by the similar effect of the oke when a light and a strange quarks are involved .
they enhance in a similar way the hyperfine splitting produced by the oge .
the important effect of the oge is observed when table [ t2 ] is compared to table ii of ref.@xcite .
the contribution of the pseudoscalar forces is much smaller in our case , generating decuplet - octet mass differences of the order of 100@xmath0200 mev , the remaining mass difference given by the oge .
.eigenvalue , in mev , of the kinetic energy combined with different contributions of the interacting potential .
the subindexes in the potential stand for : @xmath1 , @xmath2 , @xmath3 , @xmath4 , @xmath5 , @xmath6 , @xmath7 .
experimental date is taken from the pdg . [
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constituent quark models of baryon structure are based on the assumption of effective quark degrees of freedom so that a baryon is a three - quark color - singlet state .
lattice qcd in the quenched approximation shows out a @xmath8 confining potential linearly rising with the interquark distance@xcite .
this potential produces an infinite discrete hadron spectrum .
the implementation of this confining force with oge and/or goldstone boson exchanges derived from chiral symmetry breaking , or other effective interactions , turns out to be fruitful in the construction of quark potential models providing a precise description of baryon spectroscopy .
however an outstanding problem remains unsolved : all models predict a proliferation of baryon states at excitation energies above 1 gev which are not experimentally observed as resonances .
this difference between the quark model prediction and the data about the number of physical resonances is known as the missing resonance problem .
unquenched lattice qcd points out a string breaking in the static potential between two quarks@xcite what should be properly incorporated in the phenomenological description of the high energy hadronic spectrum .
the spontaneous creation of a quark - antiquark pair at the breaking point may give rise to a breakup of the color flux tube between two quarks in such a way that the quark - quark potential does not rise with the interquark distance but it reaches a maximum saturation value .
the simplest quark - quark screened potential , containing confinement and one - gluon exchange terms , reads : @xmath9 \left ( \frac{1-e^{-\mu \,\,r_{ij}}}{\mu \,\,r_{ij}}\right ) + \frac{\overline{m_{0}}}{3 }   \label{eq1}\ ] ] where @xmath10 is the interquark distance , @xmath11 the masses of the constituent quarks , @xmath12 the spin pauli operators , and @xmath13 is a constant .
the screening multiplicative factor appears between parenthesis on the right hand side .
@xmath14 , the screening parameter , is the inverse of the saturation distance and its effective value is fitted together with the other parameters , @xmath15 , @xmath16 , and @xmath17 , to the spectrum .    for nonstrange baryons
the model predicts quite approximately the number and ordering of the experimental states up to a mass of @xmath18 gev@xcite .
more recent lattice calculations@xcite show that the @xmath19 potential saturates sharply for a breaking distance of the order of 1.25 fm corresponding to a saturation energy of about twice the @xmath20 meson ( @xmath21 mass , indicating that the formation of two heavy - light subsystems is energetically favored .
a saturated quark - quark potential incorporating this effect can be parametrized as :    @xmath22    where @xmath23 + \frac{% m_0}{3}\ ] ]    whose parameters are given in ref.@xcite .
the calculation of the spectrum proceeds exactly in the same manner as in ref.@xcite , to which we refer for technical details .
it is worth to remark that the presence , in the three - body problem , of two - body thresholds ( for only one quark to be released ) , apart from the absolute three - body ones ( saturation energy ) , may represent further constraints in the applicability limit of the model to any particular channel .
the results obtained are represented in fig .
[ f1 ] . as in ref.@xcite
we have also included the predicted states close above the thresholds .
( lower part ) spectra for the screened potential of eq .
( [ eq2 ] ) with the parameters of ref.@xcite .
the thick solid lines represent our results .
the shaded region , whose size stands for the experimental uncertainty , represents the experimental data for those states cataloged as @xmath24 or @xmath25 states in the particle data book .
experimental data cataloged as @xmath26 or @xmath27 states are shown by short thin solid lines with stars over them and by vertical lines with arrows standing for the experimental uncertainties . finally , we show by a dashed line the @xmath28 ionization threshold and by a long thin solid line the total threshold.,title="fig : " ]   ( lower part ) spectra for the screened potential of eq .
( [ eq2 ] ) with the parameters of ref.@xcite .
the thick solid lines represent our results .
the shaded region , whose size stands for the experimental uncertainty , represents the experimental data for those states cataloged as @xmath24 or @xmath25 states in the particle data book .
experimental data cataloged as @xmath26 or @xmath27 states are shown by short thin solid lines with stars over them and by vertical lines with arrows standing for the experimental uncertainties .
finally , we show by a dashed line the @xmath28 ionization threshold and by a long thin solid line the total threshold.,title="fig : " ]    the quality of the description of the light baryon spectra is remarkable since apart from keeping the same level of quality than in the low and medium - lying spectrum a perfect one to one correspondence between our predicted states and the experimental resonances for any @xmath29 is obtained .
similar results are obtained using the screeend potential given in eq.[eq1 ] .
the number and ordering of states remains unaltered .
the sharp potential tends quite generally to push upward the highest energy states . in other words
the screened potential is quite similar to the closest physical approach to a nonscreened potential , represented by the sharp interaction , that takes effectively into account the effect of the baryon decay to open channels in order to select the observed resonances .
since the discovery at bnl@xcite and posterior confirmation at fermilab@xcite of the existence of charmed baryons in the late 70 s , an increasing interest on heavy baryon spectroscopy arose .
it became evident that baryons containing heavy flavors @xmath30 or @xmath31 could play an important role in our understanding of qcd .
since then , several new hadrons containing a single charm or bottom quark have been identified@xcite .
while the mass of these particles is usually measured as part of the discovery process , other quantum numbers such as the spin or parity have often proved to be more elusive . for heavy baryons ,
no spin or parity quantum numbers of a given state have been measured directly .
therefore , a powerful guideline for assigning quantum numbers to new states or even to indicate new states to look for is required by experiment .     for two different confinement strengths compared to experiment .
( b ) same as ( a ) for @xmath32 states.,title="fig : " ]   for two different confinement strengths compared to experiment .
( b ) same as ( a ) for @xmath32 states.,title="fig : " ]    several criteria can be chosen to fit the confinement strength in the baryon spectra , being the most usual ones to fit the energy splitting between the nucleon and its first radial excitation ( roper resonance ) or to fit the splitting with its lowest orbital excitation ( negative parity ) .
we show the differences using both criteria in fig .
[ fig1 ] . on the left hand side
we show the spectra obtained in the first case , named [ a ] , and on the right hand side the results obtained for the later , named [ b ] .
a better agreement is observed with the model reproducing the orbital excitations of the light baryon sector@xcite .
there is no experimental state that we do not predict and there is no low - lying theoretical resonance that has not been observed .
the recently discovered @xmath33@xcite would correspond to an orbital excitation with @xmath34 or @xmath35 , any other correspondence being definitively excluded . for @xmath36 baryons ,
the recently confirmed as a @xmath36 state , @xmath37@xcite , and the new state @xmath38@xcite may constitute the second orbital excitation of the @xmath36 baryon . finally , there is an state with a mass of 2765 mev reported in ref.@xcite as a possible @xmath36 or @xmath32 state and also observed in ref.@xcite . while the first reference ( and also the pdg ) are not able to decide between a @xmath36 or a @xmath32 state , the second one prefers a @xmath36 assignment . as seen in fig .
[ fig1 ] , this state may constitute the second member of the first orbital excitation of @xmath32 states or the first radial excitation of @xmath36 baryons .
an experimental effort to confirm the existence of this state and its decay modes would help on the symbiotic process between experiment and theory to disentangle the details of the structure of heavy baryons .
we present a study of the baryon spectra for all flavor sectors within a constituent quark model . 
 we address some of the outstanding problems in baryon spectroscopy , as for example the spin splitting evolution for te different flavor sectors , the flavor independence of confinement and the missing state problem .    
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