The weak electroweak phase transition

We present a detailed analysis of the phase transition in the standard model at finite temperature. Using an improved perturbation theory, where plasma masses are determined from a set of one-loop gap equations, we evaluate the effective potential $V_{eff}(\varphi,T)$ in next-to-leading order, i.e., including terms cubic in the gauge coupling $g$, the scalar self-coupling $\lambda^{1/2}$ and the top-quark Yukawa coupling $f_t$. The gap equations yield a non-vanishing magnetic plasma mass for the gauge bosons, originating from the non-abelian self-interactions. We discuss in detail size and origin of higher order effects and conclude that the phase transition is weakly first-order up to Higgs masses of about $70\ GeV$, above which our calculation is no longer self-consistent. For larger Higgs masses even an approximation containing all $g^4$ contributions to $V_{eff}$ is not sufficient, at least a full calculation to order $g^6$ is needed. These results turn out to be rather insensitive to the top-quark mass in the range $m_t=100\ -\ 180\ GeV$. Using Langer's theory of metastability we calculate the nucleation rate of critical droplets and discuss some aspects of the cosmological electroweak phase transition.Comment: LaTeX, 45 pages, 13 figures [not included, can be sent upon request],DESY 93-02

Hidden charm dynamically generated resonances and the e+e−→J/ψDDˉe^+e^-\to J/\psi D \bar D, J/ψDDˉ∗J/\psi D\bar D^* reactions

We analyze two recent reactions of Belle, producing $D\bar D$ and $D\bar D^*$ states that have an enhancement of the invariant $D\bar D$, $D\bar D^*$ mass distribution close to threshold, from the point of view that they might be indicative of the existence of a hidden charm scalar and an axial vector meson states below $D\bar D$ or $D\bar D^*$ thresholds, respectively. We conclude that the data is compatible with the existing prediction of a hidden charm scalar meson with mass around 3700 MeV, though other possibilities cannot be discarded. The peak seen in the $D\bar D^*$ spectrum above threshold is, however, unlikely to be due to a threshold enhancement produced by the presence, below threshold, of the hidden charm axial vector meson X(3872).Comment: 5 pages, 5 figures, 2 table

From visualization to legal design : a collaborative and creative process

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Dynamics of topological solitons in two-dimensional ferromagnets

Dynamical topological solitons are studied in classical two-dimensional Heisenberg easy-axis ferromagnets. The properties of such solitons are treated both analytically in the continuum limit and numerically by spin dynamics simulations of the discrete system. Excitation of internal mode causes orbital motion. This is confirmed by simulations.Comment: LaTeX, 15 pages, 6 figure

Exotic baryon multiplets at large number of colours

We generalize the usual octet, decuplet and exotic antidecuplet and higher baryon multiplets to any number of colours Nc. We show that the multiplets fall into a sequence of bands with O(1/Nc) splittings inside the band and O(1)splittings between the bands characterized by "exoticness", that is the number of extra quark-antiquark pairs needed to compose the multiplet. Each time one adds a pair the baryon mass is increased by the same constant which can be interpreted as a mass of a quark-antiquark pair. At the same time, we prove that masses of exotic rotational multiplets are reliably determined at large Nc from collective quantization of chiral solitons.Comment: 13 p., 5 figs. New section and references adde

Strangeness, charm and bottom in a chiral quark-meson model

In this paper we investigate an SU(3) extension of the chiral quark-meson model. The spectra of baryons with strangeness, charm and bottom are considered within a "rigid oscillator" version of this model. The similarity between the quark part of the Lagrangian in the model and the Wess-Zumino term in the Skyrme model is noted. The binding energies of baryonic systems with baryon number B=2 and 3 possessing strangeness or heavy flavor are estimated. The results obtained are in good qualitative agreement with those obtained previously in the topological soliton (Skyrme) model.Comment: 12 pages, no figures. Journal ref: submitted to Nucl.Phys.

Beyond CP violation: hadronic physics at BaBar

I report on recent studies of hadronic physics performed by the BaBar Collaboration. Emphasis is given to the measurement of the properties of newly discovered charmed hadrons and to the searches for light and heavy pentaquarks.Comment: 14 pages, 20 postscript figues, contributed to the Proceedings of the First APS Topical Group Meeting on Hadron Physics, Fermilab, Batavia, IL (October 24-26, 2004

Evidence for the positive-strangeness pentaquark Θ+\Theta^+ in photoproduction with the SAPHIR detector at ELSA

The positive--strangeness baryon resonance $\Theta^+$ is observed in photoproduction of the $\rm nK^+K^0_s$ final state with the SAPHIR detector at the Bonn ELectron Stretcher Accelerator ELSA. It is seen as a peak in the $\rm nK^+$ invariant mass distribution with a $4.8\sigma$ confidence level. We find a mass $\rm M_{\Theta^+} = 1540\pm 4\pm 2$ MeV and an upper limit of the width $\rm \Gamma_{\Theta^+} < 25$ MeV at 90% c.l. From the absence of a signal in the $\rm pK^+$ invariant mass distribution in $\rm\gamma p\to pK^+K^-$ at the expected strength we conclude that the $\Theta^+$ must be isoscalar.Comment: 9 pages, 4 figure

Phenomenology of the Pentaquark Antidecuplet

We consider the mass splittings and strong decays of members of the lowest-lying pentaquark multiplet, which we take to be a parity-odd antidecuplet. We derive useful decompositions of the quark model wave functions that allow for easy computation of color-flavor-spin matrix elements. We compute mass splittings within the antidecuplet including spin-color and spin-isospin interactions between constituents and point out the importance of hidden strangeness in rendering the nucleon-like states heavier than the S=1 state. Using recent experimental data on a possible S=1 pentaquark state, we make decay predictions for other members of the antidecuplet.Comment: 12 pages LaTeX, 1 eps figur

Flavored exotic multibaryons and hypernuclei in topological soliton models

The energies of baryon states with positive strangeness, or anti-charm (-beauty) are estimated in chiral soliton approach, in the "rigid oscillator" version of the bound state soliton model proposed by Klebanov and Westerberg. Positive strangeness states can appear as relatively narrow nuclear levels (Theta-hypernuclei), the states with heavy anti-flavors can be bound with respect to strong interactions in the original Skyrme variant of the model (SK4 variant). The binding energies of anti-flavored states are estimated also in the variant of the model with 6-th order term in chiral derivatives in the lagrangian as solitons stabilizer (SK6 variant). The latter variant is less attractive, and nuclear states with anti-charm or anti-beauty can be unstable relative to strong interactions. The chances to get bound hypernuclei with heavy antiflavors are greater within "nuclear variant" of the model with rescaled model parameter (Skyrme constant e or e' decreased by ~30%) which is expected to be valid for baryon numbers greater than B ~10. The rational map approximation is used to describe multiskyrmions with baryon number up to ~30 and to calculate the quantities necessary for their quantization (moments of inertia, sigma-term, etc.).Comment: 24 pages, 7 table