Study of the e+e− → π+π−ψ(2S) reaction at centre-of-mass energies above 4.600 GeV and search for the charged Zc(4430) exotic state at BESIII

Using six data samples with a total integrated luminosity of ∼5 fb−1 collected by the BESIII detector, the e+e− → π+π−ψ(2S) process is studied at centre-of-mass energies ranging from 4.6121 GeV to 4.6984 GeV. The measured cross-section of the e+e− → π+π−ψ(2S) reaction is consistent with published results and an enhancement can be seen around the 4.660 GeV, identified as the Y(4660) state. This represents an independent analysis of the previous BESIII results, fortifying the observation. The e+e− → π+π−ψ(2S) process is then studied via the π+π− invariant mass to search for the e+e− → f0(980)ψ(2S) interaction. The contribution of the e+e− → f0(980)ψ(2S) process is found for the first time and its cross-section is measured. In the e+e− → f0(980)ψ(2S) cross-section no particular structures can be recognised as the statistical uncertainty prevents any conclusion. The result poses a constraint on the Y (4660) state contribution to the e+e− → π+π−ψ(2S) cross-section since it is evident that the f0(980) contribution largely dominates the total production cross-section. More data is needed to see whether the Y(4660) resonance also appears in e+e− → f0(980)ψ(2S) data to further investigate its nature. Finally, a search for the Zc(4430)± exotic state is performed studying the π±ψ(2S) invariant mass, but no significant signal is found; a Bayesian upper limit at the 90% confidence level is set on the e+e− → π±Zc(4430)∓ process, leading to a production ratio R = σ(e+e− → π±Zc(4430)∓ → π+π−ψ(2S))/σ(e+e− → π+π−ψ(2S)) < 1.1%.Utilizzando sei campioni di dati con una luminosità integrata totale di ~5 fb−1 raccolti dal rivelatore BESIII, si è studiato il processo e+e− → π+π−ψ(2S) a energie del centro di massa comprese tra 4.6121 GeV e 4.6984 GeV. La sezione d’urto della reazione e+e− → π+π−ψ(2S) è in accordo con i risultati della letteratura confermando un aumento intorno a 4.660 GeV, identificato come lo stato Y(4660). Ciò rappresenta una misura indipendente dei precedenti risultati di BESIII, rafforzandone l’osservazione. Il processo e+e− → π+π−ψ(2S) è quindi analizzato tramite la massa invariante π+π− studiando l’interazione e+e− → f0(980)ψ(2S). Il contributo del processo e+e− → f0(980)ψ(2S) viene misurato per la prima volta. Nella sezione d’urto e+e− → f0(980)ψ(2S) non si riconoscono strutture particolari e l’incertezza statistica impedisce qualsiasi conclusione. I risultati pongono un vincolo sulla produzione dello stato Y(4660) all’interno del processo e+e− → π+π−ψ(2S), poiché è evidente che il contributo del mesone f0(980) domina largamente la sezione d’urto totale. Per investigare ulteriormente la natura della risonanza Y(4660) tramite il processo e+e− → f0(980)ψ(2S) è necessario raccogliere una quantità maggiore di dati. Infine, la ricerca dello stato esotico Zc(4430)± → π±ψ(2S) non ha prodotto alcun segnale significativo; viene posto, quindi, un limite bayesiano al livello di confidenza del 90% sul processo e+e− → π±Zc(4430)∓, che permette di stimare il rapporto di produzione R = σ(e+e− → π±Zc(4430)∓ → π+π−ψ(2S))/σ(e+e− → π+π−ψ(2S)) < 1.1%

The tilt of the Fundamental Plane of Early-type galaxies: wavelength dependence

The photometric parameters R_e and mu_e of 74 early-type (E+S0+S0a) galaxies in the Coma cluster are derived for the first time in the near IR H band. These are used, coupled with measurements of the central velocity dispersion found in the literature, to determine the H band Fundamental Plane (FP) relation of this cluster. The same procedure is applied to previously available photometric data in the B, V, r, I, and K bands, to perform a multi-wavelength study of the FP. Because systematic uncertainties in the value of the FP parameters are introduced both by the choice of the fitting algorithm, and by the presence of statistical biases connected with the sample selection procedure, we emphasize the importance of deriving the FP parameters in the six photometric bands using an identical fitting algorithm, and appropriate corrections to eliminate the effects of sample incompleteness. We find that the FP mu_e coefficient is stable with wavelength, while the sigma coefficient increases significantly with increasing wavelength, in agreement with an earlier result presented by Pahre & Djorgovski. The slope of the FP relation, although changing with wavelength, never approaches the virial theorem expectation. We also find that the magnitude of the slope change can be entirely explained by the presence of the well known relation between color and magnitude among early-type galaxies. We conclude that the tilt of the Fundamental Plane is significant, and must be due to some form of broken homology among early-type galaxies, while its wavelength dependence derives from whatever mechanism (currently the preferred one is the existence of a mass-metal content sequence) produces the color-magnitude relation in those galaxies.Comment: 8 pages, 7 figures, 6 tables; table 3 should be printed in landscape mode, and inserted into the text. Accepted for publication in MNRA

Building a Sample of Distant Clusters of Galaxies

Candidate clusters of galaxies drawn from the sample identified from the moderately deep I-band data of the ESO Imaging Survey (EIS), have been used for follow-up optical/infrared imaging and spectroscopic observations. The observations were conducted to assess the nature of these candidates over a large range of redshifts. Currently, 163 EIS candidates have (V-I) colors, 15 have (I-K) and 65 cluster fields have been observed spectroscopically. From a preliminary analysis of these data, we find that > 65% of the candidates studied show strong evidence of being real physical associations, over the redshift range 0.2<z<1.1. The evidence in some cases comes directly from spectroscopic measurements, in others indirectly from the detection of overdensities of objects with either the same color or the same photometric redshift, or from a combination of color and spectroscopic information. Preliminary results also suggest that the redshift derived from the matched-filter algorithm is a reasonable measure of the cluster's redshift, possibly overestimating it by Delta z ~0.1, at least for systems at z<0.7. Overdensities of red objects have been detected in over 100 candidates, 38 of which with estimated redshifts >0.6, and six candidates in the interval 0.45<z<0.81 have either been identified directly from measured redshifts or have been confirmed by the measurement of at least one redshift for galaxies located along a red-sequence typical of cluster early-type galaxies. Lastly, five candidates among those already observed in the infrared have (I-Ks) colors consistent with them being in the redshift interval 0.8<z<1.1. The sample of "confirmed" clusters, already the largest of its kind in the southern hemisphere, will be further enlarged by ongoing observations.Comment: To appear in "Large Scale Structure in the X-ray Universe", ed. M. Plionis and I. Georgantopoulos (Paris: Editions Frontieres), in pres

The Universality of the Fundamental Plane of E and S0 Galaxies. Spectroscopic data

We present here central velocity dispersion measurements for 325 early-type galaxies in eight clusters and groups of galaxies, including new observations for 212 galaxies. The clusters and groups are the A262, A1367, Coma (A1656), A2634, Cancer and Pegasus clusters, and the NGC 383 and NGC 507 groups. The new measurements were derived from medium dispersion spectra, that cover 600 A centered on the Mg Ib triplet at lambda ~ 5175. Velocity dispersions were measured using the Tonry & Davis cross-correlation method, with a typical accuracy of 6%. A detailed comparison with other data sources is made.Comment: 12 pages, 5 tables, 3 figures, to appear in AJ. Note that tables 2 and 3 are in separate files, as they should be printed in landscape forma

Resolved maps of stellar mass and SED of galaxies from optical/NIR imaging and SPS models

We report on the method developed by Zibetti, Charlot and Rix (2009) to construct resolved stellar mass maps of galaxies from optical and NIR imaging. Accurate pixel-by-pixel colour information (specifically g-i and i-H) is converted into stellar mass-to-light ratios with typical accuracy of 30%, based on median likelihoods derived from a Monte Carlo library of 50,000 stellar population synthesis models that include dust and updated TP-AGB phase prescriptions. Hence, surface mass densities are computed. In a pilot study, we analyze 9 galaxies spanning a broad range of morphologies. Among the main results, we find that: i) galaxies appear much smoother in stellar mass maps than at any optical or NIR wavelength; ii) total stellar mass estimates based on unresolved photometry are biased low with respect to the integral of resolved stellar mass maps, by up to 40%, due to dust obscured regions being under-represented in global colours; iii) within a galaxy, on local scales colours correlate with surface stellar mass density; iv) the slope and tightness of this correlation reflect/depend on the morphology of the galaxy.Comment: 4 pages, 2 figures, to appear in the proceedings of the IAU Symposium 262 "Stellar Populations: Planning for the Next Decade", Charlot & Bruzual ed