We study the transverse single-spin asymmetry (TSSA) in p↑p → J/ψX reaction, incorporating both transverse momentum and spin effects. To predict production cross section of prompt J/ψ, we use two ...different approaches, the color-singlet model and the improved color evaporation model, and show how the predicted results for TSSAs depend on the choice of hadronization model. For initial-state factorization, we also consider two options: the standard generalized parton model and the color gauge-invariant version of it. Estimates for the TSSAs in p↑p → J/ψX process for the conditions of the future Spin Physics Detector Nuclotron-based Ion Collider fAcility (NICA) experiment are presented for the first time.
Transverse single-spin asymmetries in the production of direct photons at the Nuclotron-based Ion Collider fAcility (NICA) are studied within the generalized parton model and its color ...gauge-invariant extension. Predictions for the possible asymmetry values at various NICA energies are presented. A kinematical region where the contribution of the gluon Sivers function to the asymmetry in question is dominant over the quark Sivers function is found.
The hadroproduction of the radially excited heavy-quarkonium states ψ(2S) and ϒ(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 αs and the relative heavy-quark velocity v. A satisfactory description of the ψ(2S) transverse-momentum (pT) distributions measured by ATLAS, CMS, and LHCb at center-of-mass energy S=7 TeV is obtained using the color-octet long-distance matrix elements (LDMEs) extracted from CDF data at S=1.96 TeV. The importance of the fragmentation mechanism and the scale evolution of the fragmentation functions in the upper pT range, beyond 30 GeV, is demonstrated. The ϒ(3S) pT distributions measured by CDF at S=1.8 TeV and by LHCb at S=7 TeV and forward rapidities are well described using LDMEs fitted to ATLAS data at S=7 TeV. Comparisons of polarization measurements by CDF and CMS at large pT values with our predictions consolidate the familiar problem in the ψ(2S) case, but yield reasonable agreement in the ϒ(3S) case.
We discuss production of D0D0 (and D¯0D¯0) pairs related to the LHCb Collaboration results for s=7 TeV in proton–proton scattering. We consider double-parton scattering (DPS) mechanisms of double cc¯ ...production and subsequent cc→D0D0 hadronization as well as double g and mixed gcc¯ production with gg→D0D0 and gc→D0D0 hadronization calculated with the help of the scale-dependent hadronization functions of Kniehl et al. Single-parton scattering (SPS) mechanism of digluon production is also taken into account. We compare our results with several correlation observables in azimuthal angle φD0D0 between D0 mesons or in dimeson invariant mass MD0D0. The inclusion of new mechanisms with g→D0 fragmentation leads to larger cross sections, than when including only DPS mechanism cc→D0D0 with standard scale-independent fragmentation functions. Some consequences of the presence of the new mechanisms are discussed. In particular a larger σeff is needed to describe the LHCb data. There is a signature that σeff may depend on transverse momentum of c quarks and/or c¯ antiquarks.
Based on the notion that the local dark-matter field of axions or axionlike particles (ALPs) in our Galaxy induces oscillating couplings to the spins of nucleons and nuclei (via the electric dipole ...moment of the latter and/or the paramagnetic axion-wind effect), we establish the feasibility of a new method to search for ALPs in storage rings. Based on previous work that allows us to maintain the in-plane polarization of a stored deuteron beam for a few hundred seconds, we perform a first proof-of-principle experiment at the Cooler Synchrotron (COSY) to scan momenta near 970 MeV/c. This entails a scan of the spin-precession frequency. At resonance between the spin-precession frequency of deuterons and the ALP-induced electric dipole moment (EDM) oscillation frequency, there is an accumulation of the polarization component out of the ring plane. Since the axion frequency is unknown, the momentum of the beam and, consequently, the spin-precession frequency are ramped to search for a vertical polarization change that occurs when the resonance is crossed. At COSY, four beam bunches with different polarization directions are used to make sure that no resonance is missed because of the unknown relative phase between the polarization precession and the axion or ALP field. A frequency window of 1.5 kHz width around the spin-precession frequency of 121 kHz is scanned. We describe the experimental procedure and a test of the methodology with the help of a radio-frequency Wien filter located on the COSY ring. No ALP resonance is observed. As a consequence, an upper limit of the oscillating EDM component of the deuteron as well as its axion coupling constants are provided.
We study double prompt J/ψ 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/ψ meson and the J/ψ pair. Already at leading order in αs, these predictions as well as those for the total cross section and its distributions in the invariant mass mψψ and the rapidity separation |Y| of the J/ψ pair nicely agree with recent ATLAS and CMS Collaboration measurements, except for the large-mψψ and large−|Y| regions, where the predictions substantially undershoot the data. In the latter regions, Balitsky-Fadin-Kuraev-Lipatov resummation is shown to enhance the cross sections by up to a factor of 2 and so to improve the description of the data.
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