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Register a new user$psi(2S)$ and $Upsilon(3S)$ hadroproduction in the parton Reggeization approach: Yield, polarization, and the role of fragmentation
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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.
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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.
The dipion transitions $Upsilon(2S,3S,4S) to Upsilon(1S,2S)pipi$ are systematically studied by considering the mechanisms of the hadronization of soft gluons, exchanging the bottomoniumlike $Z_b$ states, and the bottom-meson loops. The strong pion-pion final-state interaction, especially including the channel coupling to $Kbar{K}$ in the $S$-wave, is taken into account in a model-independent way using the dispersion theory. Through fitting to the available experimental data, we extract values of the transition chromopolarizabilities $|alpha_{Upsilon(mS)Upsilon(nS)}|$, which measure the chromoelectric couplings of the bottomonia with soft gluons. It is found that the $Z_b$ exchange has a slight impact on the extracted chromopolarizablity values, and the obtained $|alpha_{Upsilon(2S)Upsilon(1S)}|$ considering the $Z_b$ exchange is $(0.29pm 0.20)~text{GeV}^{-3}$. Our results could be useful in studying the interactions of bottomonium with light hadrons.
We have studied the inclusive photon spectra in Upsilon(2S) and Upsilon(3S) decays using a large statistics data sample obtained with the CLEO III detector. We present the most precise measurements of electric dipole (E1) photon transition rates and photon energies for Upsilon(2S)->gamma chi_bJ(1P) and Upsilon(3S)->gamma chi_bJ(2P) J=0,1,2. We measure the rate for a rare E1 transition Upsilon(3S)->gamma chi_b0(1P) for the first time. We also set upper limits on the rates for the hindered magnetic dipole (M1) transitions to the eta_b(1S) and eta_b(2S) states.
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.
The inclusive $Upsilon(1S,2S,3S)$ photoproduction at the future Circular-Electron-Positron-Collider (CEPC) is studied based on the non-relativistic QCD (NRQCD). Including the contributions from both direct and resolved photons, we present different distributions for $Upsilon(1S,2S,3S)$ production and the results show there will be considerable events, which means that a well measurements on the $Upsilon$ photoprodution could be performed to further study on the heavy quarkonium physics at electron-positron collider in addition to hadron colliders. This supplement study is very important to clarify the current situation of the heavy quarkonium production mechanism.
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