Sean Fleming
University of Arizona

Thomas Mehen
Duke University

Anna Stasto
Pennsylvania State University

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Inge Dolan
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INT Program INT-11-3

Frontiers in QCD

September 19 - November 18, 2011

Week 5 Schedule - All talks in seminar room C421

Monday October 17

11 am: Eugene Levin, "Title: Geometric scaling violation: running QCD coupling and DIS with nuclei"
    Abstract: The geometric scaling behaviour is a natural consequence of conformal invariance of B-K non-linerar equation. We demonstrate two examples in which there are violation of conformal symmetry and geometric scaling behaviour due to a new dimensional scales (ΛQCD) and the saturation scale at low energy.

Tuesday October 18

11 am: Andrey Grabovsky, "Transfer of gauge invariant operators from complete to Moebius representation and vice versa"

    Abstract: We study the connection between complete representations of gauge invariant operators and their Mobius representations. The possibility to restore the complete representations from Mobius forms in the coordinate space is proven and a method of restoration is worked out. The operators for transition from the standard BFKL kernel to the quasi-conformal one are found both in Mobius and total representations.

Wednesday October 19

11 am: Matt Sievert, "At the Intersection of Spin and Saturation Physics"

    Abstract: The observation of large single transverse spin asymmetries at forward rapidities in p↑ + p scattering has generated exciting developments in spin physics in high-energy QCD. Contributions to the observed asymmetries come from an asymmetric parton distribution function in a polarized proton (Sivers effect), the fragmentation of a polarized final-state quark into an asymmetric distribution of hadrons (Collins effect), and twist-3 scattering interactions between the partons. We analyze the light-cone wave function and gluon exchanges using light-cone perturbation theory, which provides a picture that is different from but complementary to the usual collinear factorization methods, and is readily generalized to incorporate saturation effects. We discuss the coupling of the C-even and C-odd parts of the wave function to 2- and 3-gluon exchange interactions; we also make a connection between single transverse spin asymmetries and the QCD odderon. Finally we discuss how the magnitude of the effect when saturation plays a bigger role, as in p↑ + A scattering.

Thursday October 20

11 am: Mickey Chiu, "Probing the Low-x Structure of the Nucleus with the PHENIX Detector"

    Abstract: One of the fundamental goals of the PHENIX experiment is to understand the structure of cold nuclear matter, since this serves as the initial state for heavy-ion collisions. Knowing the initial state is vital for interpreting measurements from heavy-ion collisions. Moreover, the structure of the cold nucleus by itself is interesting since it is a test-bed for our understanding of QCD, and in particular there is the possibility of novel QCD effects such as gluon saturation at low-x in the nucleus. At RHIC we can probe the structure of cold nuclear matter using d+Au collisions or ultra-peripheral Au+Au collisions. We will present a variety of measurements from PHENIX, of J/Psi, forward di-hadron correlations, single particles, and jets, which all seem to show some interesting effects in the cold nucleus, especially as one probes down to lower Bjorken x, to as low as ~10-3 in the Au nucleus.

Friday October 21

11 am: Francois Gelis, "Factorization in high energy nucleus-nucleus collisions"

    Abstract: I will discuss the factorization of leading logs of 1/x in nucleus-nucleus collisions at high energy. In this regime, the extraction of these logarithms is made complicated by the non-perturbative nature of the strong classical fields produced in a collision. I'll illustrate by several examples how these logarithms can shown to be universal for inclusive observables. I will also emphasize the difficulties that one encounters in the case of exclusive observables.