2,638 research outputs found

    Classifying Reported and "Missing" Resonances According to Their P and C Properties

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    The Hilbert space H^3q of the three quarks with one excited quark is decomposed into Lorentz group representations. It is shown that the quantum numbers of the reported and ``missing'' resonances fall apart and populate distinct representations that differ by their parity or/and charge conjugation properties. In this way, reported and ``missing'' resonances become distinguishable. For example, resonances from the full listing reported by the Particle Data Group are accommodated by Rarita-Schwinger (RS) type representations (k/2,k/2)*[(1/2,0)+(0,1/2)] with k=1,3, and 5, the highest spin states being J=3/2^-, 7/2^+, and 11/2^+, respectively. In contrast to this, most of the ``missing'' resonances fall into the opposite parity RS fields of highest-spins 5/2^-, 5/2^+, and 9/2^+, respectively. Rarita-Schwinger fields with physical resonances as lower-spin components can be treated as a whole without imposing auxiliary conditions on them. Such fields do not suffer the Velo-Zwanziger problem but propagate causally in the presence of electromagnetic fields. The pathologies associated with RS fields arise basically because of the attempt to use them to describe isolated spin-J=k+1/ 2 states, rather than multispin-parity clusters. The positions of the observed RS clusters and their spacing are well explained trough the interplay between the rotational-like (k/2)(k/2 +1)-rule and a Balmer-like -(k+1)^{-2}-behavior

    The Search for Neutrino Oscillations numubar->nuebar with KARMEN

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    The neutrino experiment KARMEN is situated at the beam stop neutrino source ISIS. It provides numu's, nue's and numubar's in equal intensities from the pi+ mu+ decay at rest (DAR). The oscillation channel numub->nueb is investigated in the appearance mode with a 56t liquid scintillation calorimeter at a mean distance of 17.7m from the nu source looking for p(nue,e+)n reactions. The cosmic induced background for this oscillation search could be reduced by a factor of 40 due to an additional veto counter installed in 1996. In the data collected through 1997 and 1998 no potential oscillation event was observed. Using a unified approach to small signals this leads to an upper limit for the mixing angle of sin**2(2t) < 1.3x10^{-3} (90%CL) at large Dm**2. The excluded area in (sin**2(2t),Dm**2) covers almost entirely the favored region defined by the LSND numub->nueb evidence.Comment: Proceedings Contribution to Neutrino98 in Takayama, Japan, June 4-9, 1998; 13 pages, including 4 figure

    Baryon Masses in Chiral Perturbation Theory with Infrared Regularization

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    The baryon masses are examined in SU(3) chiral perturbation theory to third order using the recently proposed infrared regularization scheme. Fourth order is estimated by evaluating the dominant diagram. With this regularization the magnitude of the loop integrals is reduced so that the convergence of the series appears to be better than in the heavy baryon approach.Comment: The original third order calculation is supplemented by an estimate of fourth order using just the dominant diagram. The convergence still appears to be better than in the heavy baryon approach. To be published in Phys. Rev. C. 15 pages latex, 2 postscript figure

    Q-ball formation in the gravity-mediated SUSY breaking scenario

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    We study the formation of Q-balls which are made of flat directions that appear in the supersymmetric extension of the standard model in the context of gravity-mediated supersymmetry breaking. The full non-linear calculations for the dynamics of the complex scalar field are made. Since the scalar potential in this model is flatter than \phi^2, we have found that fluctuations develop and go non-linear to form non-topological solitons, Q-balls. The size of a Q-ball is determined by the most amplified mode, which is completely determined by the model parameters. On the other hand, the charge of Q-balls depends linearly on the initial charge density of the Affleck-Dine (AD) field. Almost all the charges are absorbed into Q-balls, and only a tiny fraction of the charges is carried by a relic AD field. It may lead to some constraints on the baryogenesis and/or parameters in the particle theory. The peculiarity of gravity-mediation is the moving Q-balls. This results in collisions between Q-balls. It may increase the charge of Q-balls, and change its fate.Comment: 9 pages, RevTex, 11 postscript figures included, to appear in Phys. Rev.

    The B→Xsl+l−B\to X_sl^+l^- and B→XsγB\to X_s \gamma decays with the fourth generation

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    If the fourth generation fermions exist, the new quarks could influence the branching ratios of the decays of B→XsÎłB\to X_s \gamma and B→Xsl+l−B\to X_sl^+l^-. We obtain two solutions of the fourth generation CKM factor Vtâ€Čs∗Vtâ€ČbV^{*}_{t^{'}s}V_{t^{'}b} from the decay of B→XsÎłB\to X_s \gamma. We use these two solutions to calculate the new contributions of the fourth generation quark to Wilson coefficients of the decay of B→Xsl+l−B\to X_sl^+l^-. The branching ratio and the forward-backward asymmetry of the decay of B→Xsl+l−B\to X_sl^+l^- in the two cases are calculated. Our results are quite different from that of SM in one case, almost same in another case. If Nature chooses the formmer, the BB meson decays could provide a possible test of the forth generation existence.Comment: 10 pages, 5 figure

    New Uncertainties in QCD-QED Rescaling Factors using Quadrature Method

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    In this paper we briefly outline the quadrature method for estimating uncertainties in a function of several variables and apply it to estimate the numerical uncertainties in QCD-QED rescaling factors. We employ here the one-loop order in QED and three-loop order in QCD evolution equations of fermion mass renormalization. Our present calculations are found to be new and also reliable compared to the earlier values employed by various authors.Comment: 14 page

    Signatures of HyperCharge Axions in Colliders

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    If in addition to the standard model fields, a new pseudoscalar field that couples to hypercharge topological number density, the hypercharge axion, exists, it can be produced in colliders in association with photons or Z bosons, and detected by looking for its decay into photons or Z's. For a range of masses below a TeV and coupling above a fraction of 1/TeV, existing data from LEP II and the Tevatron can already put interesting constraints, and in future colliders accessible detection range is increased significantly. The hypercharge axion can help in explaining the matter-antimatter asymmetry in the universe.Comment: 11 pages, 8 figures, uses axodraw.st

    CP violation in gauge theories

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    We define the CP transformation properties of scalars, fermions and vectors in a gauge theory and show that only three types of interactions can lead to CP violation: scalar interactions, fermion-scalar interactions and FF~ F \tilde F associated with the strong CP problem and which involve only the gauge fields. For technicolor theories this implies the absence of CP violation within perturbation theory.Comment: 5 pages, 1 figure, revtex and epsf require

    Sixth-Order Vacuum-Polarization Contribution to the Lamb Shift of the Muonic Hydrogen

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    The sixth-order electron-loop vacuum-polarization contribution to the 2P1/2−2S1/22P_{1/2} - 2S_{1/2} Lamb shift of the muonic hydrogen (Ό−p+\mu^{-} p^+ bound state) has been evaluated numerically. Our result is 0.007608(1) meV. This eliminates the largest uncertainty in the theoretical calculation. Combined with the proposed precision measurement of the Lamb shift it will lead to a very precise determination of the proton charge radius.Comment: 4 pages, 5 figures the totoal LS number is change

    Infrared Quasi Fixed Points and Mass Predictions in the MSSM

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    We consider the infrared quasi-fixed point solutions of the renormalization group equations for the top-quark Yukawa coupling and soft supersymmetry breaking parameters in the MSSM. The IR quasi-fixed points together with the values of the gauge couplings, the top-quark and Z-boson masses allow one to predict masses of the Higgs bosons, the stop squarks and the lightest chargino as functions of the only free parameter m1/2m_{1/2} or the gluino mass. The mass of the lightest Higgs boson for ÎŒ>0\mu>0 and MSUSY≈1M_{SUSY} \approx 1 TeV is found to be mh=(94.3+1.6+0.6±5±0.4)m_h=(94.3+1.6+0.6\pm5\pm0.4) GeV. The case with ÎŒ<0\mu<0 is excluded by experimental data.Comment: 17 pages, LateX file with 13 eps figures, Corrected version, references are added. Final version to be published in Modern Physics Letters
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