Drell-Yan Scattering and the Structure of Hadrons

Organizers		E-Mail Address:
Paul E. Reimer	Argonne National Laboratory	reimer[at]anl[dot]gov
Oleg Denisov	INFN-Torino	denisov[at]to[dot]infn[dot]it
Marco Radici	INFN-Pavia	radici[at]pv[dot]infn[dot]it
Oleg Teryaev	Joint Institutes for Nuclear Research	teryaev[at]theor[dot]jinr[dot]ru

Program Overview

Since it was first observed, the Drell-Yan reaction has been an important tool, used to determine the substructure of both the beam and target hadrons. Experimentally, we are now working toward extending our knowledge of hadron structure from a single dimension—longitudinal momentum described by x_Bj—to include transverse degrees of freedom in the hadron as well. Traditional deep inelastic scattering (DIS) experiments will offer some answers about the transverse structure of the hadron, but they will necessarily leave some questions unanswered, with a complete answer requiring Drell-Yan measurements as well. This workshop will focus on the future theoretical and experimental work that is necessary to exploit fully the upcoming Drell-Yan measurements that will take place at Fermilab, CERN, Brookhaven and GSI-FAIR. A primary goal of this workshop is to have theoreticians provide input to experimentalists on what should be measured, and for experimentalists to provide feedback to theoreticians on what can be practically measured.  Because the Drell-Yan experiments will be collecting significant data samples in the next few years, we believe that this is the time for this workshop. The ability to measure the transverse structure of hadrons in both DIS and Drell-Yan scattering is enabling a test of the universality of transverse momentum dependent parton distributions (TMD) and, more generally, of the present understanding of (TMD) factorization theorems and color charge flow in QCD. The Sivers’ function, f_1T^⊥, which arises from final-state interactions in DIS, but initial-state interactions in Drell-Yan scattering, is believed to change sign between the two processes. Experimentalists have only recently been able to extract the Sivers’ function from DIS scattering. Soon, a new generation of Drell-Yan experiments will also be able to address this distribution. Questions to be addressed at this workshop include:

• What is the theoretical basis for expecting a change in sign of the Sivers’ function when probed with Drell-Yan scattering? Whatare the implications of an experimental evidence for no sign change?
• Is there only a sign change, with a universal magnitude for the Sivers’ function?
• How much do we know the shape of the Sivers’ function? In order to reconcile the outcome of calculations in TMD- and collinear-factorization, does the Sivers’ function need to have a node?
• What do violations of the Lam-Tung relation for Drell-Yan imply, in general and in terms of TMD?
• What can be measured about the structure of the pion and kaon with Drell-Yan?
• How is the EMC effect manifest in Drell-Yan scattering?
• What is the underlying mechanism of the generation of the hadron’s sea quark distributions?

While the first of these questions are focused on polarized Drell-Yan experiments, it is important to remember that there still remain issues of hadron structure that can only be directly addressed with unpolarized (or polarization averaged) Drell-Yan measurements.

Accommodations in Trento

Accomodations for registered participants will be handled by ECT*. ECT* has obtained a discounted price at several hotels in Trento.  A single room costs between 63 and 71€.  Do not contact the hotels directly as you will not receive the ECT* negotiated price.  These hotels include:

• Hotel America
  
• Hotel Buonconsiglio
  
• Albermonaco
  
• Hotel Accademia.

Please contact Gian Maria Ziglio <[email protected]> if you have questions or need further details.

Photographs

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Paul E. Reimer

[email protected]

25 June 2012