What does a change in the quark condensate say about restoration of chiral symmetry in matter?

The contribution of nucleons to the quark condensate in nuclear matter includes a piece of first order in $m_\pi$, arising from the contribution of low-momentum virtual pions to the $\pi N$ sigma commutator. Chiral symmetry requires that no term of this order appears in the $NN$ interaction. The mass of a nucleon in matter thus cannot depend in any simple way on the quark condensate alone. More generally, pieces of the quark condensate that arise from low-momentum pions should not be associated with partial restoration of chiral symmetry.Comment: 9 pages (RevTeX). Definition of effective mass changed; numerical value of leading nonanalytic term corrected, along with various misprint

Contributions of order O(mquark2){\cal O}(m_{\rm quark}^2) to Kℓ3K_{\ell 3} form factors and unitarity of the CKM matrix

The form factors for the $K_{\ell 3}$ semileptonic decay are computed to order $O(p^4)$ in generalized chiral perturbation theory. The main difference with the standard $O(p^4)$ expressions consists in contributions quadratic in quark masses, which are described by a single divergence-free low-energy constant, $A_3$. A new simultaneous analysis is presented for the CKM matrix element $V_{us}$, the ratio $F_K/F_{\pi}$, $K_{\ell 3}$ decay rates and the scalar form factor slope $\lambda_0$. This framework easily accommodates the precise value for $V_{ud}$ deduced from superallowed nuclear $\beta$-decays

Classical limit for semi-relativistic Hartree systems

We consider the three-dimensional semi-relativistic Hartree model for fast quantum mechanical particles moving in a self-consistent field. Under appropriate assumptions on the initial density matrix as a (fully) mixed quantum state we prove, using Wigner transformation techniques, that its classical limit yields the well known relativistic Vlasov-Poisson system. The result holds for the case of attractive and repulsive mean-field interaction, with an additional size constraint in the attractive case.Comment: 10 page

Central Nucleon-Nucleon Potential and Chiral Scalar Form Factor

The central two-pion exchange NN potential at large distances is studied in the framework of relativistic chiral symmetry and related directly to the nucleon scalar form factor, which describes the mass density of its pion cloud. This relationship is well supported by phenomenology and allows the dependence of the asymptotic potential on the nucleon mass to be assessed. Results in the heavy baryon limit are about 25% larger than those corresponding to the empirical nucleon mass in the region of physical interest. This indicates that it is very important to keep this mass finite in precise descriptions of the NN system and supports the efficacy of the relativistic chiral framework. One also estimates the contribution of subleading effects and presents a simple discussions of the role of the quark condensate in this problem.Comment: 16 pages, 8 figure

The electromagnetic effects in isospin symmetry breakings of q{\bar q} systems

The isospin symmetry breakings of q{\bar q} are investigated in the QCD sum rule method. The electromagnetic effects are evaluated following the procedure requiring that the electromagnetic effects for charged meson be gauge invariant. We find that the electromagnetic effects are also dominant in the isospin violations of rho meson, which have been shown to be the case in the mass splittings of pions. The numerical results for the difference of pion decay constants and the masses of rho mesons are presented, which are consistent with the data.Comment: To appear in Phys. Rev. D (1997

The Decuplet Revisited in χ\chiPT

The paper deals with two issues. First, we explore the quantitiative importance of higher multiplets for properties of the $\Delta$ decuplet in chiral perturbation theory. In particular, it is found that the lowest order one--loop contributions from the Roper octet to the decuplet masses and magnetic moments are substantial. The relevance of these results to the chiral expansion in general is discussed. The exact values of the magnetic moments depend upon delicate cancellations involving ill--determined coupling constants. Second, we present new relations between the magnetic moments of the $\Delta$ decuplet that are independent of all couplings. They are exact at the order of the chiral expansion used in this paper.Comment: 7 pages of double column revtex, no figure

Light quarks masses and condensates in QCD

We review some theoretical and phenomenological aspects of the scenario in which the spontaneous breaking of chiral symmetry is not triggered by a formation of a large condensate . Emphasis is put on the resulting pattern of light quark masses, on the constraints arising from QCD sum rules and on forthcoming experimental tests.Comment: 23 pages, 12 Postscript figures, LaTeX, uses svcon2e.sty, to be published in the Proceedings of the Workshop on Chiral Dynamics 1997, Mainz, Germany, Sept. 1-5, 199

Chiral Perturbation Theory for SU(3) Breaking in Heavy Meson Systems

The SU(3) breaking effects due to light quark masses on heavy meson masses, decay constants ($F_{D}, F_{D_{s}}$) and the form factor for semileptonic $\overline{B}\rightarrow D^{(\ast)} l\bar{\nu}_{l}$ transitions are formulated in chiral perturbation theory, using a heavy meson effective Lagrangian and expanding in inverse powers of the heavy meson mass. To leading order in this expansion, the leading chiral logarithms and the required counterterms are determined. At this level, a non-analytic correction to the mass splittings of ${\cal O}(p^3)$ appears, similar the the one found in light baryons. The correction to $F_{D_{s}}/F_{D}$ is roughly estimated to be of the order of $10\%$ and, therefore, experimentally accessible, while the correction to the form factor is likely to be substantially smaller. We explicitly check that the heavy quark symmetry is preserved by the chiral loops.Comment: 21 page

Genetic control of the immune response in mice: V. Minor genes involved in the response to H-Y and Ea-1 antigens

Murine responses to both the male specific histocompatibility antigen H-Y and the erythrocyte alloantigen Ea-1 are regulated by genetic factors. In each case a single major gene that controls the immune response has been identified, but additional modifying factors can be demonstrated if appropriate strain combinations are studied. A single gene controlling the response to Ea-1 antigens, which segregates when strains YBR and B10.D2 are crossed, has been shown not to be an allele of the Ir-2 locus. A new phenomenon has also been observed in the control of anti-Ea-1 antibody production in that the mating of two responding strains, YBR and HTG, produces an F 1 generation of complete nonresponders. By linkage tests it was shown that the responding strain HTG possesses the nonresponder allele at the Ir- 2 locus, so there appear to be recessive genes in the background which are able to overcome the suppressive influence of this allele.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46729/1/251_2005_Article_BF01564054.pd

Sigma-term physics in the perturbative chiral quark model

We apply the perturbative chiral quark model (PCQM) at one loop to analyse meson-baryon sigma-terms. Analytic expressions for these quantities are obtained in terms of fundamental parameters of low-energy pion-nucleon physics (weak pion decay constant, axial nucleon coupling, strong pion-nucleon form factor) and of only one model parameter (radius of the nucleonic three-quark core). Our result for the piN sigma term of about 45 MeV is in good agreement with the value deduced by Gasser, Leutwyler and Sainio using dispersion-relation techniques and exploiting the chiral symmetry constraints.Comment: 19 pages, LaTeX-file, 2 Figure