The nature of the X(3915)/X(3930)X(3915)/X(3930) resonances from a coupled-channels approach

The positive parity $\chi_{cJ}(2P)$ charmonium states are expected to lie around the 3.9 GeV/$c^2$ energy region, according to the predictions of quark models. However, a plethora of states with difficult assignment and unconventional properties have been discovered over the years, i.e., the $X(3872)$, $X(3940)$, $Y(3940)$, $X(3915)$, $X(3860)$ and the $X(3930)$ resonances, which complicates the description of this intriguing region. In this work we analyze the $0^{++}$ and $2^{++}$ sectors, employing a coupled-channels formalism successfully applied to the $1^{++}$ sector, where the $X(3872)$ was described as a $D\bar D^\ast+h.c.$ molecule with a sizable $c\bar c$ $(2^3P_1)$ component. This coupled-channels formalism is based on a widely-used Constituent Quark Model, which describes the quark-quark interactions, and the $^3P_0$ quark pair creation mechanism, used to couple the two and four quark sectors. The recent controversy about the quantum numbers of the $X(3915)$ state, the properties of the $X(3930)$ one and the nature of the new $X(3860)$ resonance are analyzed in a unified theoretical framework, being all the parameters completely constrained from previous calculations in the low-lying heavy quarkonium phenomenology.Comment: 6 pages, 2 tables. XVII International Conference on Hadron Spectroscopy and Structure - Hadron201

Immigration and the Occupational Choice of Natives: a Factor Proportions Approach

This paper evaluates the impact of immigration on the labor market outcomes of natives in France over the period 1962-1999. Combining large (up to 25%) extracts from six censuses and data from Labor Force Surveys, we exploit the variation in the immigrant share across education/experience cells and over time to identify the impact of immigration. In the Borjas (2003) specification, we find that a 10% increase in immigration increases native wages by 3%. However, as the number of immigrants and the number of natives are positively and strongly correlated across cells, the immigrant share may not be a good measure of the immigration shock. When the log of natives and the log of immigrants are used as regressors instead, the impact of immigration on natives’ wages is still positive but much smaller, and natives’ wages are negatively related to the number of natives. To understand this asymmetry and the positive impact of immigration on wages, we explore the link between immigration and the occupational distribution of natives within education/experience cells. Our results suggest that immigration leads to the reallocation of natives to better-paid occupations within education/experience cells.Immigration, Impact, France.

Does X(3872)X(3872) count?

The question on whether or not weakly bound states should be effectively incorporated in a hadronic representation of the QCD partition function is addressed by analyzing the example of the $X(3872)$, a resonance close to the $D\bar D^*$ threshold which has been suggested as an example of a loosely bound molecule. This can be decided by studying the $D \bar D^*$ scattering phase-shifts in the $J^{PC}=1^{++}$ channel and their contribution to the level density in the continuum, which also gives information on its abundance in a hot medium. In this work, it is shown that, in a purely molecular picture, the bound state contribution cancels the continuum, resulting in a null occupation number density at finite temperature, which implies the $X(3872)$ does not count below the Quark-Gluon Plasma crossover ($T \sim 150$MeV). However, if a non-zero $c \bar c$ component is present in the $X(3872)$ wave function such cancellation does not occur for temperatures above $T\gtrsim 250$MeV.Comment: 4 pages, 2 figures. XVII International Conference on Hadron Spectroscopy and Structur

Labor-Market Exposure as a Determinant of Attitudes toward Immigration

This paper re-examines the role of labor-market competition as a determinant of attitudes toward immigration. We claim two main contributions. First, we use more sophisticated measures of the degree of exposure to competition from immigrants than previously done. Specifically, we focus on the protection derived from investments in job-specific human capital and from specialization in communication-intensive jobs, in addition to formal education. Second, we explicitly account for the potential endogeneity arising from job search. Methodologically, we estimate, by instrumental variables, an econometric model that allows for heterogeneity at the individual, regional, and country level. Drawing on the 2004 European Social Survey, we obtain three main results. First, our estimates show that individuals that are currently employed in less exposed jobs are relatively more pro-immigration. This is true for both our new measures of exposure. Second, we show that the protection granted by job-specific human capital is clearly distinct from the protection granted by formal education. Yet the positive effect of education on pro-immigration attitudes is greatly reduced when we control for the degree of communication intensity of respondents' occupations. Third, OLS estimates are biased in a direction that suggests that natives respond to immigration by switching to less exposed jobs. The latter finding provides indirect support for the endogenous job specialization hypothesis postulated by Peri and Sparber (2009).immigration attitudes, labor market, job-specific human capital, communication skills, international migration

Labor-market exposure as a determinant of attitudes toward immigration

This paper re-examines the role of labor-market competition as a determinant of attitudes toward immigration. We claim two main contributions. First, we use more sophisticated measures of the degree of exposure to competition from immigrants than previously done. Specifically, we focus on the protection derived from investments in job-specific human capital and from specialization in communication-intensive jobs, in addition to formal education. Second, we explicitly account for the potential endogeneity arising from job search. Methodologically, we estimate, by instrumental variables, an econometric model that allows for heterogeneity at the individual, regional, and country level. Drawing on the 2004 European Social Survey, we obtain three main results. First, our estimates show that individuals that are currently employed in less exposed jobs are relatively more pro-immigration. This is true for both our new measures of exposure. Second, we show that the protection granted by job-specific human capital is clearly distinct from the protection granted by formal education. Yet the positive effect of education on pro-immigration attitudes is greatly reduced when we control for the degree of communication intensity of respondents' occupations. Third, OLS estimates are biased in a direction that suggests that natives respond to immigration by switching to less exposed jobs. The latter finding provides indirect support for the endogenous job specialization hypothesis postulated by Peri and Sparber (2009).immigration attitudes; labor market; job-specific human capital; communication skills; international migration