Abstract
Associated production of prompt $\Upsilon(1S)$ and $D^{+,0}$ mesons has been proposed as a golden channel for the search of Double Parton Scattering, because Single Parton Scattering contribution to the cross-section is believed to be negligible on a basis of leading order calculations in the Collinear Parton Model. We study this process in the leading order approximation of the Parton Reggeization Approach. Hadronization of $b\bar{b}$-pair into bottomonium states is described within framework of the NRQCD-factorization approach while production of $D$ mesons is described in the fragmentation model with scale-dependent fragmentation functions. We have found good agreement with LHCb data for various normalized differential distributions, except for the case of spectra on azimuthal angle differences at the small $\Delta\varphi$ values. Crucially, the total cross-section in our Single Parton Scattering model accounts for more than one half of observed cross-section, thus dramatically shrinking the room for Double Parton Scattering mechanism.
Highlights
Double parton scattering (DPS) mechanism attracts a lot of attention, both theoretically and experimentally
Recent advances in theory of DPS include computation [1] of nextto-leading-order (NLO) corrections to 1 → 2 splitting functions, contributing to the scale evolution of two parton collinear parton distribution functions (PDFs) and filling remaining gaps in the proof of the transverse momentum dependent-factorization theorem for the double Drell-Yan process [2]
While for single-scale observables, such as the total inclusive cross section of some hard process with hard scale Q, the DPS contribution is always suppressed by powers of Λ2=Q2, where Λ is some typical hadronic scale, and the DPS contribution can be comparable with the single parton scattering contribution for the differential distributions in some regions of phase space [3]
Summary
Double parton scattering (DPS) mechanism attracts a lot of attention, both theoretically and experimentally. The leading-order [LO, Oðα4sÞ in this case] calculations in the collinear parton model [6,7] and color-singlet approximation for the hadronization of bb → Υ lead to a very small SPS total cross section of this process, compared with the cross section of inclusive production of Υ mesons, calculated in the same approximation: RðSLPOSÞ 1⁄4 σðSLPOS;CSÞðΥ þ ccÞ=σðSLPOS;CSÞðΥÞ 1⁄4 ð0.2–p0.ffi6ffiffiÞ%, while experimentally this ratio reaches almost 8% at S 1⁄4 8 TeV [5]. Such a large discrepancy was interpreted in Ref.
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