Photon structure studied at an electron ion collider

Abstract

A future Electron Ion Collider (EIC) will be able to provide collisions of polarized electrons with protons and heavy ions over a wide range of center-of-mass energies (20 GeV to 140 GeV) at an instantaneous luminosity of 10 33 −10 34 cm −2 s −1 . One of its promising physics programs is the study of the partonic structure of quasi-real photons. Measuring di-jets in quasi-real photoproduction events, one can effectively access the underlying parton dynamics of the photons. In this paper, we discuss the feasibility of tagging resolved photon processes and measuring the di-jet cross section as a function of jet transverse momentum in the range of 0.01 < x rec γ < 1 at an EIC. It will be shown that both unpolarized and polarized parton distributions in the photon can be extracted, and that the flavor of the parton can be tagged at an EIC.

Experimental aspects of jet physics at a future EIC

“…The CTEQ5m PDF is used for the proton, because contrary to modern PDFs (i.e., CT, NNPDF, HERAPDF, MSTW) its value is not frozen at its input scale Q 2 0 , but allows description of the partonic structure of the proton at Q 2 ≤ Q 2 0 . In addition, this set reproduces the low Q 2 HERA cross sections quite well (see Figure 2 in [21]).…”

Nuclear parton density functions from dijet photoproduction at the EIC

“…Subsequently, other NLO parametrizations of the photon PDFs in the DIS γ [32] andMS scheme [33] have been proposed. In the absence of experimental constraints, their spread must be considered a contribution to the theoretical uncertainty that a future EIC might also help to reduce [26]. As we will see, the constraints on nuclear and photon PDFs come from complementary kinematic regions.…”

“…, where they are dominated by the pointlike (quark) contribution [25] and gluon-initiated contributions are small [26], is advantageous, as it reduces the photon PDF uncertainty on the determination of the nuclear PDFs.…”

“…Then not only direct but also resolved photons contribute [25], so that jet photoproduction at the EIC also has the potential to finally better constrain the PDFs in the photon [26]. We consider dijet instead of inclusive jet photoproduction, so that the probed x values in the heavy ion and the photon can be reconstructed (at LO exactly and beyond LO approximately) from the final state.…”

Quark matter symmetry energy effect on equation of state for neutron stars

“…In this work, we use an extended TM1 parameter set with L = 50 MeV to describe hadronic matter [12], where the model parameters were determined by the properties of finite nuclei. On the other hand, the u-d quark isospin asymmetry plays an important role in the QCD phase diagram [13,14,15] and quark matter symmetry energy [16,17,18,19,20,21,22]. We use the three flavor Nambu-Jona-Lasinio (NJL) model with isovector-vector and hypercharge-vector couplings to describe the quark matter.…”