Nucleon tensor charges in the SU(2) chiral quark-soliton model

Abstract

RUB-TPII-26/95 hep-ph/9509283We investigate the singlet g (0)T and isovector g (3)T tensor charges of the nucleon, which are deeply related to the first moment of the leading twist transversity quark distribution h1(x), in the SU(2) chiral quark-soliton model. With rotational O(1/Nc) corrections taken into account, we obtain g (0) T = 0.69 and g (3) T = 1.45 at a low normalization point of several hundreds MeV. Within the same approximation and parameters the model yields g (0) A = 0.36, g (3) A = 1.21 for axial charges and correct octetdecuplet mass splitting. We show how the chiral quark-soliton model interpolates between the nonrelativistic quark model and the Skyrme model. 11.15. Pg, 13.88.+e, 14.20.Dh The complete information about the quark structure of the nucleon in leading-order hard processes is contained in three twist-two parton distributions. Two of them f 1 (x) and g 1 (x) have been studied extensively theoretically and measured in deep-inelastic scattering experiments [1]. The third transversity quark distribution h 1 (x) is unaccessible for measurements in inclusive deepinelastic experiments. However the h 1 (x) plays an essential role in polarized Drell-Yan processes [2] and other exclusive hard reactions [3,4,5]. The measurement of the h 1 (x) has been proposed recently by the RHIC spin collaboration [6] and HERMES collaboration at HERA [7].The evolution equation for h 1 (x) has been derived in refs. [8,9]. Also it was shown by Jaffe and Ji [5] that the first moment of h 1 (x) is related to the nucleon tensor charge:where f is a flavor index (f = u, d, s, · · ·) and the tensor charge g f T is defined as the forward nucleon matrix element [5,10]:where U (p) is a standard Dirac spinor andIt is convenient to introduce singlet and isovector tensor charges:The tensor charges depend on the renormalization scale and the corresponding anomalous dimension at one loop has been calculated in refs. [2,9]: γ = 2α s /3π. Our aim is to calculate the tensor charges (2) in the chiral quark-soliton model (χQSM, often called the semibosonized Nambu-Jona-Lasinio model) at a low normalization point of several hundreds MeV.The χQSM has been successful in reproducing the static properties of the baryons such as the octet-decuplet mass splitting [11,12,13,14], axial charges [15,16,17,18] and magnetic moments [19,20] and their form factors [19,21] (for details, see the recent review [22]). The baryon in this model is regarded as a bound state of N c quarks bound by a non-trivial chiral field configuration. Such a semiclassical picture of baryons can be justified in the N c → ∞ limit in line with more general arguments by Witten [23]. A remarkable virtue of χQSM is that the model interpolates between the nonrelativistic quark model(NRQM) and the Skyrme model [24]. In particular, due to such an interplay, it enables us to examine the dynamical difference between the axial and tensor charges of the nucleon.In the following, we employ the effective QCD partition function from the instanton picture of QCD in the limit of...

Transverse spin distribution function of the nucleon in chiral theory

“…The result in the rhs coincides with the expression obtained in paper [26] for the tensor charge of nucleon so that the sum rule (17) automatically holds in the effective chiral theory.…”

Helicity and transversity distributions of the nucleon andΛhyperon fromΛfragmentation

“…Such a scenario should be able to reflect the bulk features of the valence quarks for the octet baryons, although it might be too rough for their sea content. The δU and δD so obtained are compatible with those from a chiral soliton model [25]. We may readjust the values when experimental constraints become available, or if we believe other models are more reasonable [21].…”

Tensor charges of the nucleon in the SU(3) chiral quark soliton model

“…This equation can be used to evolve the tensor charges from the low normalization point (several hundreds MeV) pertinent to the chiral quark-soliton model (χQSM) we are dealing with, to higher normalization points. Since the corresponding anomalous dimension is relatively small, the value of the tensor charge at a higher normalization point is insensitive to uncertainties of low normalization points relevant to our model [15].…”

“…The dynamical origin of the difference between the axial and tensor charges in our model can be related to the qualitatively different behaviour of the charges with soliton size [15].…”