Exploring Jet Properties in p-p Collisions at 200 GeV with STAR

The mechanisms underlying hadronization are not well understood, both in vacuum and in hot QCD matter. Precise characterization of jet fragmentation to hadrons in p-p collisions will help elucidate the fundamental process of hadronization, and will serve as essential reference to measure the modification of hadronization in heavy ion collisions. We present measurements of fragmentation functions for unidentified particles in jets produced in p-p collisions at 200 GeV using the STAR detector at RHIC. The results from different jet reconstruction algorithms are compared, including variations of the resolution parameter. It is found that the results are largely insensitive to details of the jet-finding algorithm at RHIC energies. Particle production inside and outside of these reconstructed jets will be compared to improve our understanding of the hadronization mechanisms for soft and hard particles in p-p events at RHIC energies.Comment: 4 pages, 7 figures - To appear in the conference proceedings for Quark Matter 2009, March 30 - April 4, Knoxville, Tennessee Final version after referee's comment

Initial state nuclear effects for jet production measured in sNN=200GeV\sqrt{s_\mathrm{NN}} = 200 \mathrm{GeV} d+Au collisions by STAR

Full jet reconstruction in heavy-ion collisions is a promising tool for quantitative study of properties of the dense medium produced at RHIC. Measurements of d+Au collisions are important to disentangle initial state nuclear effects from medium-induced $k_\mathrm{T}$ broadening and jet quenching. We report measurements of mid-rapidity ($|\eta_{jet}| < 0.4|$) di-jet correlations in d+Au using high-statistics run 8 RHIC data at $\sqrt{s_\mathrm{NN}} = 200 \mathrm{GeV}$.Comment: 2 pages, 2 figures - To appear in the conference proceedings for Quark Matter 2009, March 30 - April 4, Knoxville, Tennesse

Heavy Quark Production: Theory vs. Experiment

The current status of the comparisons between some experimental results and theoretical predictions for heavy quark production is reviewed. It is shown that the combination of new theoretical tools and better experimental input allows for a good description of charm, bottom and top hadroproduction, with no significant discrepancies between theory and experiment. Theoretical progress in the resummation of large logarithms and inclusion of power corrections for the heavy quark fragmentation function is also discussed.Comment: 6 pages, LaTeX, Talk given at the Workshop on High Energy Physics IFAE 2003, Lecce, Italy, 23-26 April 200

Collinear Subtractions in Hadroproduction of Heavy Quarks

We present a detailed discussion of the collinear subtraction terms needed to establish a massive variable-flavour-number scheme for the one-particle inclusive production of heavy quarks in hadronic collisions. The subtraction terms are computed by convoluting appropriate partonic cross sections with perturbative parton distribution and fragmentation functions relying on the method of mass factorization. We find (with one minor exception) complete agreement with the subtraction terms obtained in a previous publication by comparing the zero-mass limit of a fixed-order calculation with the genuine massles results in the MSbar scheme. This presentation will be useful for extending the massive variable-flavour-number scheme to other processes.Comment: 29 pages, 17 figures include

Mapping the stellar populations of the Milky Way with Gaia

Gaia will be ESA's milestone astrometric mission, and is due for launch at the end of 2013. Gaia will repeatedly map the whole sky measuring about one billion sources to V=20-22 mag. Its data products will be {\mu}as accuracy astrometry, optical spectrophotometry and medium resolution spectroscopy. A description of the Gaia space mission and its characteristics and performance is given. The expected impact on Galactic stellar population studies is discussed, with particular attention to the sources of interest for CoRoT and Kepler.Comment: Proc. of the workshop "Asteroseismology of stellar populations in the Milky Way" (Sesto, 22-26 July 2013), Astrophysics and Space Science Proceedings, (eds. A. Miglio, L. Girardi, P. Eggenberger, J. Montalban

Measurements of jet structure and fragmentation from full jet reconstruction in heavy ion collisions at RHIC

Measurements of inclusive hadron suppression and di-hadron azimuthal correlations have provided important insights into jet quenching in hot QCD matter. However, they do not provide access to the energy of the hard scattering and are limited in their sensitivity since they can be affected by biases toward hard fragmentation and small energy loss. Full jet reconstruction in heavy-ion collisions enables a complete study of the modification of jet structure due to energy loss, but is challenging due to the high-multiplicity environment. We present measurements of fully reconstructed di-jets at mid-rapidity in 200 GeV p+p and central Au+Au collisions performed with the STAR detector. We compare fragmentation functions measured in 200 GeV p+p and central Au+Au collisions and assess the systematic uncertainties of their ratio.Comment: Proceedings of Quark Matter 09 Conferenc

The LEP Trail to Non-Perturbative QCD

This talk summarizes the presentations given in the Hadronic Physics session at the LEPTRE meeting, emphasizing the importance of LEP data in our quest for a successful approach to non-perturbative QCD.Comment: 6 pages, Latex, epsfig. Summary talk of the Hadronic Physics session of the LEPTRE meeting. Rome, April 2001. To be published in the Proceeding