Partial widths for the decays eta(1295) -> gamma gamma and eta(1440) -> gamma gamma

We discuss gamma gamma partial widths of pseudoscalar/isoscalar mesons eta(M) in the mass region M = 1000-1500 MeV. The transition amplitudes eta(1295) -> gamma gamma and eta(1440) -> gamma gamma are studied within an assumption that the decaying mesons are the members of the first radial excitation nonet 2^1S_0 q\bar q. The calculations show that partial widths being of the order of 0.1 keV are dominantly due to the n\bar n meson component while the contribution of the s\bar s component is small.Comment: 3 pages, LaTeX, 4 EPS figures, epsfig.st

Pulsar Bound on the Photon Electric Charge Reexamined

If photons had a small electric charge $Q_\gamma$ their path in the galactic magnetic field would be curved, leading to a time delay between photons of different frequency from a distant source. Cocconi's previous application of this argument led to a limit which is too restrictive by a factor of about 200; the corrected bound is Q_\gamma/e\lapprox10^{-29}.Comment: 3 pages, LaTe

Top quark loop corrections to the decay H+→h0W+H^+ \to h^0 W^+ in the Two Higgs Doublet Model

We calculate the decay width for the process $H^+ \to h^0 W^+$ up to order $g^4$ in the framework of the Two Higgs Doublet Model. We argue that for some reasonable choice of the free parameters the contribution from the one-loop graphs can be as large as 40%.Comment: 9 pages (in a4wide), tex with figures attached, uuencoded tared gzip file Postscript file also available at http://thep.physik.uni-mainz.de/~brueche

Sum rules for charmed baryon masses

The measured masses of the three charge states of the charmed $\Sigma_c$ baryon are found to be in disagreement with a sum rule based on the quark model, but relying on no detailed assumptions about the form of the interaction. This poses a significant problem for the charmed baryon sector of the quark model. Other relations among charmed baryon masses are also discussed.Comment: 5 pages, latex, no figure

Octet Magnetic Moments with Null Instantons and Semibosonized Nambu-Jona-Lasinio Model

It is shown that the difference between the magnetic moment results in the quark model with null instantons and semibosonized Nambu-Jona-Lasinio model lies in the description of the magnetic moment of the $\Lambda$-hyperon.Comment: RevTex, 6 pages, submitted to Progr.Theor.Phy

Baryon anomaly and strong color fields in Pb+Pb collisions at 2.76A TeV at the CERN Large Hadron Collider

With the HIJING/BBbar v2.0 heavy ion event generator, we explore the phenomenological consequences of several high parton density dynamical effects predicted in central Pb+Pb collisions at the Large Hadron Collider (LHC) energies. These include (1) jet quenching due to parton energy loss (dE/dx), (2) strangeness and hyperon enhancement due to strong longitudinal color field (SCF), and (3) enhancement of baryon-to-meson ratios due to baryon-anti-baryon junctions (JJbar) loops and SCF effects. The saturation/minijet cutoff scale p0(s)and effective string tension kappa(s,A) are constrained by our previous analysis of LHC p+p data and recent data on the charged multiplicity for Pb+Pb collisions reported by the ALICE collaboration. We predict the hadron flavor dependence (mesons and baryons) of the nuclear modification factor RAA(pT)$ and emphasize the possibility that the baryon anomaly could persist at the LHC up to pT=10 GeV, well beyond the range observed in central Au+Au collisions at RHIC energies.Comment: 25 pages, 8 figures, revtex4, text modifications, added references, accepted for publication Phys. Rev. C (2011

Production of scalar KKˉK\bar K molecules in ϕ\phi radiative decays

The potentialities of the production of the scalar $K\bar K$ molecules in the $\phi$ radiative decays are considered beyond the narrow resonance width approximation. It is shown that $BR(\phi\rightarrow\gamma f_0(a_0)\rightarrow\gamma\pi\pi(\pi\eta))\approx (1\div 2)\times 10^{-5}\ ,\BR(\phi\rightarrow\gamma (f_0+a_0)\rightarrow\gamma K^+K^-)\alt 10^{-6}$and$BR(\phi\rightarrow\gamma (f_0+a_0) \to \gamma K^0\bar K^0)\alt 10^{-8}$. The mass spectra in the$\pi\pi\ ,\ \pi\eta\ ,\ K^+K^-\ ,\ K^0\bar K^0$channels are calculated. The imaginary part of the amplitude$\phi\rightarrow\gamma f_0(a_0)$is calculated analytically. It is obtained the phase of the scalar resonance production amplitude that causes the interference patterns in the reaction$e^+e^-\rightarrow\gamma \pi^+\pi^-$in the$\phi$ meson mass region.Comment: 19 pages, revtex, 4 eps files of figure

Diquark-Antidiquarks with Hidden or Open Charm and the Nature of X(3872)

Heavy-light diquarks can be the building blocks of a rich spectrum of states which can accommodate some of the newly observed charmonium-like resonances not fitting a pure c-cbar assignment. We examine this possibility for hidden and open charm diquark-antidiquark states deducing spectra from constituent quark masses and spin-spin interactions. Taking the X(3872) as input we predict the existence of a 2++ state that can be associated to the X(3940) observed by Belle and re-examine the state claimed by SELEX, X(2632). The possible assignment of the previously discovered states D_s(2317) and D_s(2457) is discussed. We predict X(3872) to be made of two components with a mass difference related to (m_u-m_d) and discuss the production of X(3872) and of its charged partner X^(+-) in the weak decays of B^(+,0).Comment: 11 pages, 2 figures, revtex, minor typos correcte

A Multi-Phase Transport Model for Relativistic Heavy Ion Collisions

We describe in detail how the different components of a multi-phase transport (AMPT) model, that uses the Heavy Ion Jet Interaction Generator (HIJING) for generating the initial conditions, Zhang's Parton Cascade (ZPC) for modeling partonic scatterings, the Lund string fragmentation model or a quark coalescence model for hadronization, and A Relativistic Transport (ART) model for treating hadronic scatterings, are improved and combined to give a coherent description of the dynamics of relativistic heavy ion collisions. We also explain the way parameters in the model are determined, and discuss the sensitivity of predicted results to physical input in the model. Comparisons of these results to experimental data, mainly from heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC), are then made in order to extract information on the properties of the hot dense matter formed in these collisions.Comment: 33 pages, 38 figures, revtex. Added 9 figures, version published in Phys. Rev. C. The full source code of the AMPT model in the Fortran 77 language and instructions for users are available from the EPAPS ftp site (ftp://ftp.aip.org/epaps/phys_rev_c/E-PRVCAN-72-781512/) and the OSCAR website (http://www-cunuke.phys.columbia.edu/OSCAR/

Weak Hyperon Production in ep Scattering

We study the kinematics and cross section of the scattering process $e p \rightarrow e \Sigma^+$. The cross section is expressed in terms of complex form factors characterizing the hadron vertices. We estimate the cross section for small momentum transfer using known experimental information. To first order in the momentum transfer, we obtain a model independent result for the photon-exchange part of the cross section, which is completely determined by the decay width $\Gamma(\Sigma^+ \rightarrow p\gamma)$. For the kinematics of the parity violation experiment at MAMI, this first order result gives rise to a ratio of $(d\sigma/d\Omega)_{ep\rightarrow e\Sigma^+}$ $/(d\sigma/d\Omega)_{ep\rightarrow ep} \simeq 4.0\times 10^{-15}$. The $Z^0$-exchange and interference parts give much smaller contributions due to the suppression of the flavor changing weak neutral current in the standard model. Feasibility of the experimental measurement is briefly discussed.Comment: ReVTeX, 9 pages, one figure embedde