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Register a new userDouble prompt $J/psi$ hadroproduction in the parton Reggeization approach with high-energy resummation
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We study double prompt $J/psi$ hadroproduction within the nonrelativistic-QCD factorization formalism adopting the parton Reggeization approach to treat initial-state radiation in a gauge invariant and infrared-safe way. We present first predictions for the cross section distributions in the transverse momenta of the subleading $J/psi$ meson and the $J/psi$ pair. Already at leading order in $alpha_s$, these predictions as well as those for the total cross section and its distributions in the invariant mass $m_{psipsi}$ and the rapidity separation $|Y|$ of the $J/psi$ pair nicely agree with recent ATLAS and CMS measurements, except for the large-$m_{psipsi}$ and large-$|Y|$ regions, where the predictions substantially undershoot the data. In the latter regions, BFKL resummation is shown to enhance the cross sections by up to a factor of two and so to improve the description of the data.
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The hadroproduction of the radially excited heavy-quarkonium states $psi(2S)$ and $Upsilon(3S)$ at high energies is studied in the parton reggeization approach and the factorization formalism of nonrelativistic QCD at lowest order in the strong-coupling constant $alpha_s$ and the relative heavy-quark velocity $v$. A satisfactory description of the $psi(2S)$ transverse-momentum ($p_T$) distributions measured by ATLAS, CMS, and LHCb at center-of-mass energy $sqrt{S}=7$ TeV is obtained using the color-octet long-distance matrix elements (LDMEs) extracted from CDF data at $sqrt{S}=1.96$ TeV. The importance of the fragmentation mechanism and the scale evolution of the fragmentation functions in the upper $p_T$ range, beyond 30 GeV, is demonstrated. The $Upsilon(3S)$ $p_T$ distributions measured by CDF at $sqrt{S}=1.8$ TeV and by LHCb at $sqrt{S}=7$ TeV and forward rapidities are well described using LDMEs fitted to ATLAS data at $sqrt{S}=7$ TeV. Comparisons of polarization measurements by CDF and CMS at large $p_T$ values with our predictions consolidate the familiar problem in the $psi(2S)$ case, but yield reasonable agreement in the $Upsilon(3S)$ case.
We study the photoproduction of isolated prompt photons associated with hadron jets in the framework of the parton Reggeization approach. The main improvements with respect to previous studies in the k_T-factorization framework include the application of the Reggeized-quark formalism, the generation of exactly gauge-invariant amplitudes with off-shell initial-state quarks, and the exact treatment of the gamma+R -> gamma+g box contribution with off-shell initial-state gluons. In this proceedings, the new data set, published recently by ZEUS collaboration is analyzed, were the distributions in photon and jet rapidity, transverse energy, azimuthal angle between photon and jet and proton momentum fraction are presented for different values of measured photon momentum fraction x_gamma <0.7, 0.8 and x_gamma>0.8$. The good agreement of measured distributions with our predictions is observed for the direct-dominating part of the data set. The comparison with the previous calculations in k_T-factorization, role of nonfactorizable higher-order and hadronization corrections is discussed.
We compute fragmentation corrections to hadroproduction of the quarkonium states $J/psi$, $chi_{cJ}$, and $psi(2S)$ at leading power in $m_c^2/p_T^2$, where $m_c$ is the charm-quark mass and $p_T$ is the quarkonium transverse momentum. The computation is carried out in the framework of nonrelativistic QCD. We include corrections to the parton-production cross sections through next-to-leading order in the strong coupling $alpha_s$ and corrections to the fragmentation functions through second order in $alpha_s$. We also sum leading logarithms of $p_T^2/m_c^2$ to all orders in perturbation theory. We find that, when we combine these leading-power fragmentation corrections with fixed-order calculations through next-to-leading order in $alpha_s$, we are able to obtain good fits for $p_Tgeq 10$ GeV to hadroproduction cross sections that were measured at the Tevatron and the LHC. Using values for the nonperturbative long-distance matrix elements that we extract from the cross-section fits, we make predictions for the polarizations of the quarkonium states. We obtain good agreement with measurements of the polarizations, with the exception of the CDF Run II measurement of the prompt $J/psi$ polarization, for which the agreement is only fair. In the predictions for the prompt-$J/psi$ cross sections and polarizations, we take into account feeddown from the $chi_{cJ}$ and $psi(2S)$ states.
In this work, we investigate the prompt $J/psi$ production in associated with top quark pair to leading order in the nonrelativistic QCD factorization formalism at the LHC with $sqrt{s} =13$ TeV. In addition to the contribution from direct $J/psi$ production, we also include the indirect contribution from the directly produced heavier charmmonia $chi_{cJ}$ and $psi^prime$. We present the numerical results for the total and differential cross sections and find that the $sideset{^3}{^{(8)}_1}{mathop{{S}}}$ states give the dominant contributions. The prompt $tbar t J/psi$ signatures at the LHC are analyzed in the tetralepton channel $ppto (tto W^+(ell^+ u)b) (bar t to W^-(ell^- bar u)bar b) (J/psitomu^+mu^-)$ and trilepton channel $ppto (tto W(q q^prime)b) ( t to W(ell u) b) (J/psitomu^+mu^-)$, with the $J/psi$ mesons decaying into muon pair, and the top quarks decaying leptonically or hadronically. We find that $tbar t J/psi$ proudction can be potentially detected at the LHC, whose measurement is useful to test the heavy quarkonium production mechanism.
Using the standard Balitsky-Fadin-Kuraev-Lipatov (BFKL) approach, with partial inclusion of next-to-leading order effects, we propose the inclusive hadroproduction of a Higgs boson and of a jet, featuring large transverse momenta and well separated in rapidity, as a new channel to probe the BFKL dynamics. Predictions are presented for cross-sections and azimuthal angle correlations in different kinematics configurations for the final-state transverse momenta. We find that the large energy scales provided by the emission of a Higgs boson stabilize the BFKL series.
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