# Directory

**Educational Background:**

M.S. 1997, Milan U., Italy

Ph.D. 2002, Trieste U., Italy

**Research Interests:**

Theoretical Quantum Chromo Dynamics, Nuclear Physics, Elementary Particle Physics

My primary focus is on understanding the structure of the ordinary building blocks of matter, the protons and neutrons (nucleons), in the nucleus of atoms. I am in particular interested in how their constituents, the quarks and the gluons (partons), share the momentum and spin of their parent nucleon. The region of large parton fractional momentum is especially important because there the partons behavior is determined by the effects of a phenomenon called "color confinement", whereby particles carrying a "color" charge, such as quarks and gluons, cannot be detected in isolation but can only live inside a color-neutral particle such as protons, neutrons and pions. This region can be probed in high-energy electron-nucleon or nucleon-nucleon collisions but require a careful study of a number of theoretical corrections to perturbative QCD computations of these processes. I am also interested in collisions on nuclear targets, where parton distributions are modified compared to a nucleon due to an intricate interplay of parton dynamics and nuclear effects which has so far eluded a universally accepted theoretical explanation.

Experimental data from a number of different processes can then be used to produced a global QCD fit of parton distribution functions with greatly increased precision in the large fractional momentum region, and these can then be used in the computation of QCD backgrounds to searches for new physics at Tevatron (Fermilab) and the LHC (CERN, Geneva), and to neutrino oscillation experiments, among others. Likewise, via global fits, data from these high-energy physics experiments can be used to constrain the non perturbative structure of the hadron, and the interactions of proton and neutrons inside a nucleus.

In these investigations, I enjoy a close collaboration with several experimental colleagues at Hampton U., Jefferson Lab, and elsewhere; I also provide theoretical support for experimental data analysis and interpretation, and new experimental proposals at Jefferson Lab and elsewhere.

Furthermore, I am studying the effects of color confinement in the the space-time evolution of the hadronization process in high-energy scatterings on nuclear targets, whereby a parton momentarily freed from its parent nucleus by a hard scattering has to neutralize its color and form one or more hadrons before detection. Understanding the dynamics of color confinement is a complementary approach to hadron spectroscopy, which studies the effects of color confinement long after this has set in.

Yet another way of studying color confinement is to study a deconfined state of quark and gluons, called the Quark-Gluon Plasma, created in ultra-relativistic heavy-ion collisions; its properties can be accessed by utilizing as probes high-energy particles created in the same collision. While I do not actively participate in this research anymore, understanding the hadronization process in ordinary nuclei is essential to unravel the vast amount of data on heavy-ion collisions produced at the SPS accelerator at CERN, and the RHIC accelerator at Brookhaven National Laboratory. With the new LHC data on the highest-energy nucleus-nucleus collisions ever there is plenty to learn about.

Finally, I started my adventure in physics trying to understand color confinement from first principles by rewriting the QCD theory in terms of a topological field theory describing its non perturbative aspects, plus a term which describes the behavior of point-like gluons and quarks. My research interests have changed over time, but the first love is never forgotten.

**I am a member of:**

- The The Theory Group at Jefferson Lab
- The CTEQ-JLab collaboration
- The CTEQ collaboration
- The Electron-Ion Collider collaboration
- The MEIC (Medium-energy Electron Ion Colider) study group at Jefferson Lab

**Selected Publications (Full List on InSPIRE):**

- J.F. Owens, A. Accardi, W. Melnitchouk

“*Global parton distributions with nuclear and finite-Q^2 corrections”*

Phys.Rev.D to appear [arXiv:1212.1702] - P. Monaghan, A. Accardi, M.E. Christy, C.E. Keppel, W. Melnitchouk, L. Zhu

“*Moments of the longitudinal proton structure function F_L from global data in the Q^2 range 0.75-45.0 (GeV/c)^2”*

Phys.Rev.Lett. to appear [arXiv:1209.4542] - A.Accardi et al.

“Electron Ion Collider: The Next QCD Frontier - Understanding the glue that binds us all”

e-Print: arXiv:1212.1701 - S. Abeyratne, A. Accardi, S. Ahmed
*et al.*,

“*Science Requirements and Conceptual Design for a Polarized Medium Energy Electron-Ion Collider at Jefferson Lab,”*

e-Print: arXiv:1209.0757 - V. Guzey, L. Zhu, C.E. Keppel, M.E. Christy, D. Gaskell, P. Solvignon, A. Accardi

“*Impact of nuclear dependence of R=σL/σT on antishadowing in nuclear structure functions”*

Phys.Rev. C86 (2012) 045201 - L.T. Brady, A. Accardi, W. Melnitchouk, J.F. Owens

“*Impact of PDF uncertainties at large x on heavy boson production”*

JHEP 1206 (2012) 019 - O. Hen, A. Accardi, W. Melnitchouk, E. Piasetzky

“*Constraints on the large-x d/u ratio from electron-nucleus scattering at x>1”*

Phys.Rev. D84 (2011) 117501 - A. Accardi, V. Guzey, A. Prokudin, C. Weiss

“*Nuclear physics with a medium-energy Electron-Ion Collider”*

Eur.Phys.J. A48 (2012) 92 - L.T. Brady, A. Accardi, T.J. Hobbs, W. Melnitchouk

“**Next-to leading order analysis of target mass corrections to structure functions and asymmetries”**

Phys.Rev. D84 (2011) 074008, Erratum-ibid. D85 (2012) 039902 - D. Boer, M. Diehl, R. Milner, R. Venugopalan, W. Vogelsang ,D. Kaplan, H. Montgomery, S.Vigdor, A. Accardi, E.C. Aschenauer et al.

“*Gluons and the quark sea at high energies: Distributions, polarization, tomography”*

SLAC-R-995, INT-PUB-11-034, BNL-96164-2011, JLAB-THY-11-1373 - A. Accardi, W. Melnitchouk, J.F. Owens, M.E. Christy, C.E. Keppel, L. Zhu, J.G. Morfin.

“*Uncertainties in determining parton distributions at large x”*

Phys.Rev. D84 (2011) 014008 - A. Accardi, M.E. Christy, C.E. Keppel, P. Monaghan, W. Melnitchouk, J.G. Morfin and J.F. Owens

“*New parton distributions from large-x and low-Q2 data"*

Phys.Rev. D81 (2010) 034016 - A. Accardi, F. Arleo, W. K. Brooks, D. D'Enterria and V. Muccifora,

“, invited review*Parton Propagation and Fragmentation in QCD Matter"*

Riv. Nuovo Cim. 032 (2010) 439 - A. Accardi, A. Bacchetta, W. Melnitchouk and M. Schlegel,

“*What can break the Wandzura- Wilczek relation?"*

JHEP 0911 (2009) 093 - A. Accardi, T. Hobbs and W. Melnitchouk,

“*Hadron mass corrections in semi-inclusive deep inelastic scattering"*

JHEP 0911 (2009) 084 - A. Accardi and W. Melnitchouk,

“*Target mass corrections for spin-dependent structure functions in collinear factorization"*

Phys. Lett. B 670 (2008) 114 - A. Accardi and J. W. Qiu,

“*Collinear factorization for deep inelastic scattering structure functions at large Bjorken xB"*

JHEP 0807 (2008) 090 - A. Accardi,

”*Final state interactions and hadron quenching in cold nuclear matter”*

Phys. Rev. C 76 (2007) 034902 - A. Accardi,

“*Space-time evolution of hadronization"*

Eur. Phys. J. C 49 (2007) 347 - A. Accardi,

“*Formation time scaling and hadronization in cold nuclear matter”*

Phys. Lett. B 649 (2007) 384 - A. Accardi, D. Grunewald, V. Muccifora and H. J. Pirner,

“*Atomic mass dependence of hadron production in deep inelastic scattering on nuclei”*

Nucl. Phys. A 761 (2005) 67 - A. Accardi,

“*'Naked' Cronin effect in A + A collisions from SPS to RHIC”*

Eur. Phys. J. C 43 (2005) 121 - A. Accardi and M. Gyulassy,

“*Cronin effect vs. geometrical shadowing in d + Au collisions at RHIC”*

Phys. Lett. B 586 (2004) 244 - A. Accardi,

“*Cronin effect in proton nucleus collisions: A survey of theoretical models”*

[contribution to CERN Yellow Report on “ Hard probes in heavy ion collisions at the LHC”, CERN-2004-009-A]

arXiv:hep-ph/0212148 - A. Accardi, V. Muccifora and H. J. Pirner,

“*Hadron production in deep inelastic lepton nucleus scattering”*

Nucl. Phys. A 720 (2003) 131 - A. Accardi,

“*Initial conditions and charged multiplicities in ultrarelativistic heavy ion collisions”*

Phys. Rev. C 64 (2001) 064905 - A. Accardi and D. Treleani,

“*Minijet transverse spectrum in high-energy hadron nucleus collisions”*

Phys. Rev. D 64 (2001) 116004 - A. Accardi, A. Belli, M. Martellini and M. Zeni,

“*Topological Yang-Mills cohomology in pure Yang-Mills theory”*

Phys. Lett. B 431 (1998) 127 - A. Accardi, A. Belli, M. Martellini and M. Zeni,

“*Cohomology and renormalization of BFYM theory in three dimensions”*

Nucl. Phys. B 505 (1997) 540