Organizers:
Sean Fleming
University of Arizona
fleming@physics.arizona.edu
Thomas Mehen
Duke University
mehen@phy.duke.edu
Anna Stasto
Pennsylvania State University
astasto@phys.psu.edu
Program Coordinator: Inge Dolan
inge@u.washington.edu
(206) 6854286
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INT Program INT113
Frontiers in QCD
September 19  November 18, 2011
Week 3 Schedule  All talks in seminar room C421
Monday, 10/3
11 am: Alexander Pimikov, "QCD sum rules concepts and pion structure"
Abstract: We study the pion structure in terms of the pion Distribution Amplitude (DA), the electromagnetic Form Factor (FF), and the transition pionphoton form factor in framework of QCD sum rules with nonlocal condensate and lightcone sum rules. The significance of the condensate's nonlocality is demonstrated. A global fit of pion DA to the data from different collaborations (CELLO, CLEO, BaBar) on the pionphoton transition form factor is carried out using lightcone sum rules. The analysis includes the nexttoleading QCD radiative corrections and the twistfour contributions, while the main nexttonexttoleading term and the twistsix contribution are taken into account in the form of theoretical uncertainties.
Tuesday, 10/4
11 am: Iain Stewart, "Jet Physics from Static Charges in AdS"
Abstract: The Wilson lines describing soft interactions with jets can be transformed into static charges on an AdS space with a special set of coordinates. Many of the interesting properties of multiWilson line soft functions are easily understood from this point of view. Motivated by this I will introduce a new class of gauges, dubbed conformal gauges, which avoid mixing in AdS, and show how they simplify computations at two loops and beyond.
Wednesday, 10/5
11 am: Randall Kelley, "Towards precision jet observables"
Abstract: Calculating the distribution of jet masses in highenergy collisions is challenging because fixed order perturbation theory breaks down near the peak region, and because multiple scales complicate the resummation. To avoid using a jet veto, one can consider inclusive observables, in which every particle is in a jet. We give an example of such an observable, asymmetric thrust, which can be resummed to nexttonexttoleading logarithmic accuracy. Exclusive observabes with outofjet regions are more complicated. Even for e+e dijet events at energy Q, to calculate the mass m of jets of size R, one must impose a veto on the energy ω of extra jets to force dijet kinematics; then there are both log m/Q and log m/ω singularities. These extra scales prevent the simplest resummation from being valid beyond the leadinglogarithmic level. To proceed, we derive a refactorization of the soft function in the small R and small ω limit which allows us to resum additional logs of the jet mass. The expansion of the resummed distribution is shown to have excellent agreement with fixed order even at moderate R. Prospects for jet mass calculations at hadron colliders are also discussed.
Thursday, 10/6
10 am: Michael Fickinger, "Precision determination of alpha_S(m_Z) from thrust data"
Abstract: I will present an extraction of the strong coupling constant, alpha_S(m_Z), from thrust data using Effective Field Theory techniques. Our calculation yields one of the most precise measurements of alpha_S(m_Z) to date. We perform a simultaneous two parameter fit to all available data at energies Q = 35 GeV to 207 GeV. We find alpha_S(m_Z) = 0.1135 + (0.0002)expt + (0.0005)hadr + (0.0009)pert, with chi^{2}/dof = 0.91, where the displayed 1sigma errors are the total experimental uncertainty, the hadronization uncertainty, and the perturbative theory uncertainty, respectively.
11 am: Ambar Jain, "Rapidity Renormalization Group Formalism"
Abstract: I will talk about some formal aspects of the rapidity renormalization group that is useful for factorization theorems in SCET_II. Several examples of factorization theorems exists in SCET_II, such as Sudakov form factor, Higgs transverse momentum distribution, jet broadening and some exclusive Bdecays. I will include discussion of Sudakov form factor and exclusive decays in the new formalism and other details about calculation and setting up the new RGE.
Friday, 10/7
No seminars
