1,246 research outputs found

    Hyperfine Mass Splittings of Baryons Containing a Heavy Quark in Large N QCD

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    The hyperfine mass splittings of baryons containing a heavy quark are derived at leading order in large NN QCD. Hyperfine splittings either preserve or violate heavy quark spin symmetry. Previous work proves that the splittings which preserve heavy quark spin symmetry are proportional to J2{\bf J}^2 at order 1/N1/N, where JJ is the angular momentum of the light degrees of freedom of the baryon. This work proves that the splittings which violate heavy quark spin symmetry are proportional to JSQ{\bf J} \cdot {\bf S_Q} at order 1/(NmQ)1/(N m_Q) in the 1/N1/N and 1/mQ1/m_Q expansions.Comment: (8 pages, no figures, uses harvmac), UCSD/PTH 93-2

    Heavy Baryon Masses in Large N_c HQET

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    We argue that in the large N_c HQET, the masses of the s-wave low-spin heavy baryons equal to the heavy quark mass plus proton mass approximately. To the subleading order, the heavy baryon mass 1/N_c expansion not only has the same form, but also has the same coefficients as that of the light baryon. Based on this, numerical analysis is made.Comment: 7 pages, latex, no figures, to appear in Phys. Lett.

    Chiral solitons from dimensional reduction of Chern-Simons gauged non-linear Schr\"odinger model of FQHE: classical and quantum aspects

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    The soliton structure of a gauge theory recently proposed to describe chiral excitations in the Fractional Quantum Hall Effect is investigated. A new type of non-linear derivative Schr\"odinger equation emerges as an effective description of the system that supports novel chiral solitons. We discuss the classical properties of solutions with vanishing and non-vanishing boundary conditions (dark solitons) and we explain their relation to integrable systems. The quantum analysis is also addressed in the framework of a semiclassical approximation improved by Renormalization Group arguments.Comment: 39 page, RevTeX, 6 figure

    Large-N Baryons, Chiral Loops, and the Emergence of the Constituent Quark

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    Meson loop corrections to baryon axial currents are computed in the 1/N expansion. It is already known that the one-loop corrections are suppressed by a factor 1/N; here it is shown that the two-loop corrections are suppressed by (1/N)^2. To leading order, these corrections are exactly what would be calculated in the constituent quark model. Some applications are discussed

    Naturalness of the Coleman-Glashow Mass Relation in the 1/N_c Expansion: an Update

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    A new measurement of the Xi^0 mass verifies the accuracy of the Coleman-Glashow relation at the level predicted by the 1/N_c expansion. Values for other baryon isospin mass splittings are updated, and continue to agree with the 1/N_c hierarchy.Comment: 6 pages, revte

    Baryon masses at second order in large-NN chiral perturbation theory

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    We consider flavor breaking in the the octet and decuplet baryon masses at second order in large-NN chiral perturbation theory, where NN is the number of QCD colors. We assume that 1/N1/NFms/Λmu,d/Λ,αEM1/N \sim 1/N_F \sim m_s / \Lambda \gg m_{u,d}/\Lambda, \alpha_{EM}, where NFN_F is the number of light quark flavors, and mu,d,s/Λm_{u,d,s} / \Lambda are the parameters controlling SU(NF)SU(N_F) flavor breaking in chiral perturbation theory. We consistently include non-analytic contributions to the baryon masses at orders mq3/2m_q^{3/2}, mq2lnmqm_q^2 \ln m_q, and (mqlnmq)/N(m_q \ln m_q) / N. The mq3/2m_q^{3/2} corrections are small for the relations that follow from SU(NF)SU(N_F) symmetry alone, but the corrections to the large-NN relations are large and have the wrong sign. Chiral power-counting and large-NN consistency allow a 2-loop contribution at order mq2lnmqm_q^2 \ln m_q, and a non-trivial explicit calculation is required to show that this contribution vanishes. At second order in the expansion, there are eight relations that are non-trivial consequences of the 1/N1/N expansion, all of which are well satisfied within the experimental errors. The average deviation at this order is 7 \MeV for the \De I = 0 mass differences and 0.35 \MeV for the \De I \ne 0 mass differences, consistent with the expectation that the error is of order 1/N210%1/N^2 \sim 10\%.Comment: 19 pages, 2 uuencoded ps figs, uses revte

    Properties of "35" Spin-(5/2) Baryon Resonances in a Model with Broken SU(3)

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    We investigate the properties of a set of J =(5/2)^+ resonances appearing in a 35-dimensional representation of SU(3), as proposed by Abers, Balázs, and Hara. A simple dynamical calculation gives an estimate for the mass differences within the supermultiplet. The matrix elements for the SU(3) allowed decays into meson plus resonance are given in terms of one parameter and the SU(3)-violating matrix elements for decay into meson plus baryon are given by two parameters

    General S-Matrix Methods for Calculation of Perturbations on the Strong Interactions

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    Recently, the authors proposed an on-the-mass-shell, S-matrix method for computing the effects of small perturbations on the masses and coupling constants of strongly interacting particles. In the present paper, the method is generalized to the multichannel case. The use of group-theoretical techniques in reducing the complexity of the method is described in detail

    Large N_c Limit of Spin-Flavor Breaking in Excited Baryon Levels

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    Spin-flavor symmetry breaking in the levels of excited Baryons are studied to leading order in the 1/NcN_c expansion. This breaking occurs at zeroth order. For non-strange Baryons with a single quark excited, it is shown that to first order of perturbation theory the breaking is given by one 1-body operator (spin-orbit), and three 2-body operators, all involving the orbital angular momentum of the excited quark. Higher-body operators can be reduced to that set of operators. As illustration, p-wave Baryons are briefly discussed.Comment: 16 pages, one table, Latex file; title changed, some omitted operators have been included and corrections to the results have been mad
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