Hot Stellar Populations in Globular Clusters: a Photometrist's View

We briefly review the recent results on hot horizontal-branch stars in globular clusters. Since the first Ivanfest, in 1992, there have been a number of new observational lines of evidence which have allowed significant progress in our understanding of blue-tail stars, though new, even more intriguing questions arise. Despite this progress, we still do not know the answer to the main question: why are there blue-HB-tail stars? The new photometric data bases collected in the last few years, and the forthcoming multi-fiber observational campaigns on 10m-class telescopes, might be the key to solve this puzzle. We will show an example of how these data bases can disclose important properties of blue HB stars.Comment: 12 pages, 5 figures, A.S.P. Conf. Ser., in press in Vol. 296, 200

Standard Model Higgs search at LEP in channels other than four jets

The LEP centre of mass energy has been increased since 1996 in the aim of producing the Higgs boson. The SM Higgs boson search has been pursued in the four LEP collaborations exploiting final states with higher branching ratios. In the following we discuss the search in final states with two jets and missing energy or charged leptons.Comment: Proceedings of Moriond QCD, 17-24 march 200

Sensitivity to sgoldstino states at the future linear e+e−e^+e^- and photon colliders

Sensitivity to the supersymmetric scalar states $\phi$ at the future linear $e^+e^-$ and photon colliders is discussed. In particular it is illustrated a search strategy for massive sgoldstinos, the supersymmetric partners of the goldstino

The Contributions of Interactive Binary Stars to Double Main Sequence Turn-Offs and Dual Red Clump of Intermediate-Age Star Clusters

Double or extended main-sequence turn-offs (DMSTOs) and dual red clump (RC) were observed in intermediate-age clusters, such as in NGC 1846 and 419. the DMSTOs are interpreted as that the cluster has two distinct stellar popula- tions with differences in age of about 200-300 Myr but with the same metallicity. The dual RC is interpreted as a result of a prolonged star formation. Using a stellar population-synthesis method, we calculated the evolutions of binary-star stellar population (BSP). We found that binary interactions and merging can reproduce the dual RC in the color-magnitude diagrams of an intermediate-age cluster, whereas in actuality only a single population exists. Moreover, the binary interactions can lead to an extended MSTO rather than DMSTOs. However, the rest of main sequence, subgiant branch and first giant branch are hardly spread by the binary interactions. Part of the observed dual RC and extended MSTO may be the results of binary interactions and merger.Comment: 10 pages, 2 figures; accepted by ApJ

Comparison between Observed and Theoretical Red Giant Branch Luminosity Functions of Galactic Globular Clusters

V-band luminosity functions have been obtained for the upper main-sequence, sub-giant branch and red giant branch of 18 galactic globular clusters from HST data. A comparison with four sets of theoretical models has been performed. In contrast with what was found in several previous works, a Good general agreement has been found between the observed and theoretical LF at any metallicity [M/H]<-0.7. Possible discrepancies at higher metallicity, in the upper part of the RGB, need to be confirmed with further observational data and by extending all the models to the most metal rich regime. The SGB shape has been used to set an upper limit to the cluster age, and consequently a lower limit on the cluster distance. A discussion on the still open problem of the mismatch between the observed and theoretical RGB bump location is also presented.Comment: Accepted for publication in A&

Statistical Study of the Blue Straggler Properties in Galactic Globular Clusters

In this paper we report on the most significant results from a statistical analysis of the main properties of globular cluster blue straggler stars (BSS) extracted from the HST snapshot database of photometrically homogeneous CMDs (Piotto et al. 2002). The BSS relative frequency presents a significant anticorrelation with the collisional rate and with the cluster total absolute luminosity.Comment: 2 pages, 1 figure, A.S.P. Conf. Ser., in press in Vol. 296, 200