Speaker
Description
Parton Reggeization approach (PRA) is based on $k_T$-factorization of hard processes at multi-Regge kinematics. In PRA, initial state partons are treated as Reggeized gluons and Reggeized quarks, which are quantum fields of Lipatov's Effective Theory [1]. This one guarantees gauge invariance for off-shell hard amplitudes. As it was shown in [2], unintegrated (transverse momentum dependent) parton distribution functions (uPDFs) of off-shell partons $\Phi(x,{\bf q}_T^2,\mu^2)$ is naturally described by the Kimber-Martin-Ryskin (KMR) model [3].
Inclusive production of isolated photon is described in the leading order (LO) of PRA via $2\to 1$ parton subprocess $Q\bar Q\to \gamma$. The gauge invariant amplitude of this process is proportional to Fadin-Sherman effective vertex $\Gamma_{QQ\gamma}^\mu$ [4].
At first, we study single photon production in LO PRA in $pp(p\bar p)$ collisions at the energies of LHC and Tevatron Colliders using original KMR model for uPDFs. To study processes at sufficiently low energies (from $\sqrt{S}=20$ to $\sqrt{S}=200$ GeV), we suggest modified multi-Regge approximation in which modified KMR model can be used at arbitrary $x$. We describe old data from SPS, RHIC and predict photon spectra for future SPD NICA experiment.
We have studied photon production in LO and NLO PRA in Refs. [5]-[8].
[1] L.N. Lipatov L.N. Gauge invariant effective action for
high energy processes in QCD. Nucl. Phys. {\bf B452} (1995) 369;
L.N. Lipatov, M.I. Vyazovsky. Quasi-multi-Regge processes with a
quark exchange in the t-channel, Nucl. Phys. {\bf B597} (2001) 399.
[2] A.V. Karpishkov, M.A. Nefedov and V.A. Saleev,
$B{\bar B}$ angular correlations at the LHC in parton Reggeization approach merged with higher-order matrix elements, Phys. Rev. D 96 (2017) no.9, 096019.
[3] M. A. Kimber, A. D. Martin, and M. G. Ryskin, Unintegrated
parton distributions and prompt photon hadroproduction, Eur. Phys.
J. C12 (2000) 655.
[4] V. Fadin V and V. Sherman, Fermion reggeization in nonabelian
calibration theories, JETP Lett. 23 (1976) 599.
[5] M. Nefedov and V. Saleev, Diphoton production at the Tevatron and the LHC in the NLO approximation of the parton Reggeization approach, Phys. Rev. D92 (2015) no.9, 094033
[6] B.A. Kniehl, M.A. Nefedov and V.A. Saleev, Prompt-photon plus jet associated photoproduction at HERA in the parton Reggeization approach
Phys. Rev. D89 (2014) no.11, 114016
[7] B.A. Kniehl, V.A. Saleev, A.V. Shipilova and E.V. Yatsenko,
Single jet and prompt-photon inclusive production with multi-Regge kinematics: From Tevatron to LHC, Phys. Rev. D {\bf 84} (2011) 074017
[8] V.A. Saleev, Prompt photon photoproduction at HERA within the
framework of the quark Reggeization hypothesis, Phys. Rev. D78 (2008) 114031.
