Heavy Quarkonium Spectroscopy

This paper reviews the experimental status of the Heavy Quarkonium Spectroscopy and highlights the measurements that hint at the existence of a new form of quark and gluon aggregation beyond the mesons and the baryons.Comment: 7 pages, 9 postscript figures, contributed to the Proceedings of Lepton-Photon 200

Reassessing Labor Market Reforms: Temporary Contracts as a Screening Device

Standard models of temporary contracts are either inconclusive, or fail to account for the positive correlation between temporary contracts and the employment rate, and for the high transition rates into permanent employment measured in Europe. This paper shows that a matching model in which firms use temporary contracts to screen workers for permanent positions can successfully fulfill this task. When the model is calibrated to the Italian economy, it accounts for salient statistics including the worker turnover rate, the transition rates into permanent employment, and the drop in the unemployment rate following the reforms implemented in the late 1990s. When temporary contracts are used as a screening device, they can increase both productivity and welfare. Their quantitative impact crucially hinges on dismissal costs and minimum wages.job-search, temporary contracts, labor market institutions, screening, hiring procedures, turnover rates, wage di¤erentials.

Unemployment and Within-Group Wage Inequality: Can Information Explain the Trade-Off?

In Italy, following WWII, specific hiring procedures were developed that prevented firms from screening workers. More in particular, these institutions characterized the Italian labor market with respect to the US labor market, and were gradually removed during the 1990s. A simple matching model in which the usual Nash bargaining criterion is replaced by a game of incomplete information, shows that such hiring procedures endogenously generate wage compression within groups of observationally equivalent workers, as well as higher unemployment rates. Both the estimated behavior of within-group wage inequality in Italy, computed from the micro-data of the SHIW panel of the Bank of Italy, and the behavior of the unemployment rate in the late 1990s, are consistent with the predictions of the model.job-search, labor market institutions, within-group wage inequality, bargaining with incomplete information, screening

Changes in output, employment and wages during recessions in the United Kingdom

Employment has fallen during this recession but by much less than the fall in output. This article examines how the behaviour of the labour market compares with previous recessions. A number of factors, including greater flexibility in real wages, may have helped to mitigate the fall in employment to date. But there is considerable uncertainty about how the labour market will evolve.

Exotic Hadrons with Hidden Charm and Strangeness

We investigate on exotic tetraquark hadrons of the kind [cs][cbar sbar] by computing their spectrum and decay modes within a constituent diquark-antidiquark model. We also compare these predictions with the present experimental knowledge.Comment: 6 pages, 2 figures, minor changes made, references adde

Labor-Market Volatility in the Search-and-Matching Model: The Role of Investment-Specific Technology Shocks

Shocks to investment-specific technology have been identified as a main source of U.S. aggregate output volatility. In this paper we assess the contribution of these shocks to the volatility of labor market variables, namely, unemployment, vacancies, tightness and the job-finding rate. Thus, our paper contributes to a recent body of literature assessing the ability of the search-and-matching model to account for the large volatility observed in labor market variables. To this aim, we solve a neoclassical economy with search and matching in the labor market, where neutral and investment-specific technologies are subject to shocks. The three key features of our model economy are: i) Firms are large, in the sense that they employ many workers. ii) Adjusting capital and labor is costly. iii) Wages are the outcome of an intra-firm Nash-bargaining problem between the firm and its workers. In our calibrated economy, we find that shocks to investment-specific technology explain 40 percent of the observed volatility in U.S. labor productivity. Moreover, these shocks generate relative volatilities in vacancies and the workers' job finding rate which match those observed in U.S. data. Relative volatilities in unemployment and labor market tightness are 55 and 75 percent of their empirical values, respectively.Business Cycles; Labor Market Fluctuations; Investment-Specific Technical Change; Search and Matching; Adjustment Costs; Wage Bargaining.

Does cointegration matter? An analysis in a RBC perspective

The aim of this paper is to verify if a proper SVEC representation of a standard Real Business Cycle model exists even when the capital stock series is omitted. The argument is relevant as the common unavailability of su¢ ciently long medium-frequency capital series prevent researchers from including capital in the widespread structural VAR (SVAR) representations of DSGE models - which is supposed to be the cause of the SVAR biased estimates. Indeed, a large debate about the truncation and small sample bias a¤ecting the SVAR performance in approximating DSGE models has been recently rising. In our view, it might be the case of a smaller degree of estimates distorsions when the RBC dynamics is approximated through a SVEC model as the information provided by the cointegrating relations among some variables might compensate the exclusion of the capital stock series from the empirical representation of the model.RBC, SVAR, SVEC model, cointegration

Charmed Baryonium

We re-analyze the published data on the Y(4630) --> Lambda_c Lambdabar_c and the Y(4660) --> psi(2S) pi pi with a consistent Ansatz and we find that the two observations are likely to be due to the same state Y_B with M_{Y_B} = 4660.7 +- 8.7 MeV and Gamma_{Y_B} = 61 +- 23 MeV. Under this hypothesis and reanalizing also the e+e- --> J/psi pi pi gamma_ISR spectrum we extract B(Y_B --> Lambda_c Lambdabar_c) / B(Y_B --> psi(2S) pi pi) = 25 +- 7, B(Y_B --> J/psi pi pi) / B(Y_B --> psi(2S) pi pi) J/psi pi pi) / B(Y(4350) --> psi(2S) pi pi) psi(2S) sigma) / B (Y_B --> psi(2S) f_0)=2.0 +- 0.3. These conclusions strongly support the hypothesis of Y_B being the first observation of a charmed baryonium constituted by four quarks. From the analysis of the mass spectrum and the decay properties we show that Y(4350) and Y_B are respectively consistent with the ground state and first radial excitation of the L=1 state.Comment: Corrected phase space normalization in the fit

On the Spin of the X(3872)

Whether the much studied X(3872) is an axial or tensor resonance makes an important difference to its interpretation. A recent paper by the BaBar collaboration raised the viable hypothesis that it might be a 2-+ state based on the 3 pions spectrum in the X -> J/psi omega decays. Furthermore, the Belle collaboration published the 2 pions invariant mass and spin-sensitive angular distributions in X -> J/psi rho decays. Starting from a general parametrization of the decay amplitudes for the axial and tensor quantum numbers of the X, we re-analyze the whole set of available data. The level of agreement of the two spin hypotheses with data is interpreted with a rigorous statistical approach based on Monte Carlo simulations in order to be able to combine all the distributions regardless of their different levels of sensitivity to the spin of the X. Our analysis returns a probability of 5.5% and 0.1% for the agreement with data of the 1++ and 2-+ hypotheses, respectively, once we combine the whole information (angular and mass distributions) from both channels. On the other hand, the separate analysis of J/psi rho (angular and mass distributions) and J/psi omega (mass distribution) indicates that the 2-+ assignment is excluded at the 99.9% C.L. by the former case, while the latter excludes at the same level the 1++ hypothesis. There are therefore indications that the two decay modes behave in a different way.Comment: 12 pages, 9 figures, 2 tables. Added angular distributions, which lead to different conclusion