Neutrinos, axions and conformal symmetryMeissner, Krzysztof A.;Nicolai, Hermann
doi: 10.1140/epjc/s10052-008-0760-xpmid: N/A
Abstract We demonstrate that radiative breaking of conformal symmetry (and simultaneously electroweak symmetry) in the standard model with right-chiral neutrinos and a minimally enlarged scalar sector induces spontaneous breaking of lepton number symmetry, which naturally gives rise to an axion-like particle with some unusual features. The couplings of this ‘axion’ to standard model particles, in particular photons and gluons, are entirely determined (and computable) via the conformal anomaly, and their smallness turns out to be directly related to the smallness of the masses of the light neutrinos.
Lee-Yang circle analysis of e + e − and $p\overline{p}$ generalized multiplicity distributionDewanto, A.;Chan, A. H.;Oh, C. H.;Chen, R.;Sitaram, K.
doi: 10.1140/epjc/s10052-008-0750-zpmid: N/A
Abstract We study the evolution of Lee-Yang zeros structure of generalized multiplicity distribution (GMD) in high energy collision. Starting our study with electron-positron e + e − scattering data, we extend the study by Chan and Chew (Z. Phys. C 55:503, 1992) on TASSO and AMY multiplicity data for \(\sqrt{s}=14\) , 22, 34.8, 43.6 and 57 GeV to the ones from DELPHI and OPAL Collaboration for \(\sqrt{s}=91\) , 133, 161, 172, 183 and 189 GeV. We compare the results with the Lee-Yang structure for proton-antiproton \(p\overline{p}\) at \(\sqrt{s}=200\) , 546 and 900 GeV from UA5 Collaboration. Our preliminary result shows that there is indeed a change in the shape and size of the Lee-Yang zeros with increasing energy, accompanied by the development of the so-called “ear”-like structure in the Lee-Yang plot. We expect that the development of this “ear”-like structure is related to the “shoulder” structure in the multiplicity data, which further indicates an ongoing phase transition from soft to semihard scattering. We also extend our prediction to LHC’s \(\sqrt{s}=14\) TeV. Insert your abstract here.
Towards a measurement of the two-photon decay width of the Standard Model Higgs boson at a Photon ColliderMönig, K.;Rosca, A.
doi: 10.1140/epjc/s10052-008-0765-5pmid: N/A
Abstract A study of the measurement of the two photon decay width times the branching ratio of the Standard Model Higgs boson with a mass of 120 GeV in photon–photon collisions is presented, assuming a γ γ integrated luminosity of 80 fb−1 in the high energy part of the spectrum. The analysis is based on the reconstruction of the Higgs events produced in the γ γ→H process, followed by the decay of the Higgs into a \(\mathrm{b}\bar{\mathrm{b}}\) pair. A statistical error of the measurement of the two-photon width, Γ(H→γ γ), times the branching ratio of the Higgs boson, BR \((\mathrm{H}\to \mathrm{b}\bar{\mathrm{b}})\) is found to be 2.1% for one year of data taking.
Chiral properties of baryon interpolating fieldsNagata, Keitaro;Hosaka, Atsushi;Dmitrašinović, V.
doi: 10.1140/epjc/s10052-008-0692-5pmid: N/A
Abstract We study the chiral transformation properties of all possible local (non-derivative) interpolating field operators for baryons consisting of three quarks with two flavors, assuming good isospin symmetry. We derive and use the relations/identities among the baryon operators with identical quantum numbers that follow from the combined color, Dirac and isospin Fierz transformations. These relations reduce the number of independent baryon operators with any given spin and isospin. The Fierz identities also effectively restrict the allowed baryon chiral multiplets. It turns out that the non-derivative baryons’ chiral multiplets have the same dimensionality as their Lorentz representations. For the two independent nucleon operators the only permissible chiral multiplet is the fundamental one, \((\frac{1}{2},0)\oplus(0,\frac{1}{2})\) . For the Δ, admissible Lorentz representations are \((1,\frac{1}{2})\oplus(\frac{1}{2},1)\) and \((\frac{3}{2},0)\oplus(0,\frac{3}{2})\) . In the case of the \((1,\frac{1}{2})\oplus (\frac{1}{2},1)\) chiral multiplet, the \(I(J)=\frac{3}{2}(\frac{3}{2})\) Δ field has one \(I(J)=\frac{1}{2}(\frac{3}{2})\) chiral partner; otherwise it has none. We also consider the Abelian (U A(1)) chiral transformation properties of the fields and show that each baryon comes in two varieties: (1) with Abelian axial charge +3; and (2) with Abelian axial charge −1. In case of the nucleon these are the two Ioffe fields; in case of the Δ, the \((1,\frac{1}{2})\oplus(\frac{1}{2},1)\) multiplet has an Abelian axial charge −1 and the \((\frac{3}{2},0)\oplus(0,\frac{3}{2})\) multiplet has an Abelian axial charge +3.
AdS-QCD quark–antiquark potential, meson spectrum and tetraquarksCarlucci, M. V.;Giannuzzi, F.;Nardulli, G.;Pellicoro, M.;Stramaglia, S.
doi: 10.1140/epjc/s10052-008-0687-2pmid: N/A
Abstract The AdS/QCD correspondence predicts the structure of the quark–antiquark potential in the static limit. We use this piece of information together with the Salpeter equation (Schrödinger equation with relativistic kinematics) and a short range hyperfine splitting potential to determine quark masses and the quark potential parameters from the meson spectrum. The agreement between theory and experimental data is satisfactory, provided one considers only mesons comprising at least one heavy quark. We use the same potential (in the one-gluon-exchange approximation) and these data to estimate the constituent diquark masses. Using these results as input we compute tetraquark masses using a diquark–antidiquark model. The masses of the states X(3872) or Y(3940) are predicted rather accurately. We also compute tetraquark masses with open charm and strangeness. Our result is that tetraquark candidates such as D s (2317), D s (2457) or X(2632) can hardly be interpreted as diquark–antidiquark states within the present approach.
Lowest-lying tetra-quark hadrons in anisotropic lattice QCDLoan, Mushtaq;Luo, Zhi-Huan;Lam, Yu Yiu
doi: 10.1140/epjc/s10052-008-0689-0pmid: N/A
Abstract We present a detailed study of the lowest-lying \(q^{2}\bar{q}^{2}\) hadrons in quenched improved anisotropic lattice QCD. Using the π π and diquark–antidiquark local and smeared operators, we attempt to isolate the signal for I(J P)=0(0+),2(0+) and 1(1+) states in two flavour QCD. In the chiral limit of the light-quark mass region, the lowest scalar 4q state is found to have a mass, m I=04q =927(12) MeV, which is slightly lower than the experimentally observed f 0(980). The results from our variational analysis do not indicate a signature of a tetraquark resonance in I=1 and I=2 channels. After the chiral extrapolation the lowest 1(1+) state is found to have a mass m I=14q =1358(28) MeV. We analysed the static 4q potential extracted from a tetraquark Wilson loop and illustrated the behaviour of the 4q state as a bound state, unbinding at some critical diquark separation. From our analysis we conclude that the scalar 4q system appears as a two-pion scattering state and that there is no spatially-localised 4q state in the light-quark mass region.