Upsilon Production Research Articles

Elastic and large t rapidity gap vector meson production in ultraperipheral proton–ion collisions

We evaluate the cross sections for the production of vector mesons in exclusive ultraperipheral proton-ion collisions at LHC. We find that the rates are high enough to study the energy and momentum transfer dependence of vector mesons - rho,phi, J/psi, Upsilon photoproduction in gamma p scattering in a wide energy range extending the measurements which were performed at HERA, providing new information about interplay of soft and hard physics in diffraction. Also, we calculate the contributions to the vector meson yield due to production of vector mesons off nuclear target by photons emitted by proton. We find, that least in the case of Upsilon production it is feasible to observe simultaneously both these processes. Such measurements would increase the precision with which the A-dependence of exclusive onium production can be determined. This would also enable one to estimate the amount of nuclear gluon shadowing of generalized gluon distributions at much smaller x than that is possible in AA collisions and to measure the cross sections for photoproduction processes in a significantly wider energy range than that achieved in experiments with fixed nuclear targets. We also present the cross section for vector meson production in pA collisions at RHIC. In addition, we consider production of vector mesons off protons with large rapidity gaps and large t. These processes probe small x dynamics of the elastic interaction of small dipoles at high energies and large but finite t, that is in the kinematics where DGLAP evolution is strongly suppressed. We estimate that this process could be studied at LHC up to W ~1 TeV with detectors which will be available at LHC.

Dielectron Widths of theΥ(1S,2S,3S)Resonances

We determine the di-electron widths of the Upsilon(1S), Upsilon(2S), and Upsilon(3S) resonances with better than 2% precision by integrating the cross-section of e+e- -> Upsilon over the e+e- center-of-mass energy. Using e+e- energy scans of the Upsilon resonances at the Cornell Electron Storage Ring and measuring Upsilon production with the CLEO detector, we find di-electron widths of 1.354 +- 0.004 (stat) +- 0.020 (syst) keV, 0.619 +- 0.004 +- 0.010 keV, and 0.446 +- 0.004 +- 0.007 keV for the Upsilon(1S), Upsilon(2S), and Upsilon(3S), respectively.

First observation of aΥ(1D)state

We present the first evidence for the production of Upsilon(1D) states in the four-photon cascade, Upsilon(3S)-->gamma chib(2P), chib(2P)-->gamma Upsilon(1D), Upsilon(1D)-->gamma chib(1P), chib(1P)-->gamma Upsilon(1S), followed by the Upsilon(1S) annihilation into e+e- or mu+mu-. The signal has a significance of 10.2 standard deviations. The measured product branching ratio for these five decays, (2.5+-0.5+-0.5)x10^(-5), is consistent with the theoretical estimates. The data are dominated by the production of one Upsilon(1D) state consistent with the J=2 assignment. Its mass is determined to be (10161.1+-0.6+-1.6) MeV, which is consistent with the predictions from potential models and lattice QCD calculations. We also searched for Upsilon(3S)-->gammachib(2P), chib(2P)-->gammaUpsilon(1D), followed by either Upsilon(1D)-->eta Upsilon(1S) or Upsilon(1D)-->pi+pi- Upsilon(1S). We find no evidence for such decays and set upper limits on the product branching ratios.

Onset of perturbative color opacity at smallxand Υ coherent photoproduction off heavy nuclei at LHC

We study photon-induced coherent production of Upsilon in ultraperipheral heavy ion collisions at LHC and demonstrate that the counting rates will be sufficient to measure nuclear shadowing of generalized gluon distributions. This will establish the transition from the regime of color transparency to the regime of perturbative color opacity in an unambiguous way. We argue that such measurements will provide the possibility to investigate the interaction of ultra-small color dipoles with nuclei in QCD at large energies, which are beyond the reach of the electron-nucleon (nucleus) colliders, and will unambiguously discriminate between the leading twist and higher twist scenarios of gluon nuclear shadowing.

Search for associated production of Upsilon and vector boson in pp collisions at sqrt[s]=1.8 TeV.

We present a search for associated production of the Upsilon(1S) and a vector boson in 83 pb(-1) of ppmacr; collisions at sqrt[s]=1.8 TeV collected by the CDF experiment in 1994-1995. We find no evidence of the searched signal in the data, and set upper limits to the production cross sections.

Upsilon production and polarization in p p macro collisions at square root of s = 1.8 TeV.

We report on measurements of the Upsilon(1S), Upsilon(2S), and Upsilon(3S) differential cross sections (d(2)sigma/dp(T)dy)(/y/<0.4), as well as on the Upsilon(1S) polarization in p p macro collisions at square root of s = 1.8 TeV using a sample of 77+/-3 pb(-1) collected by the collider detector at Fermilab. The three resonances were reconstructed through the decay Upsilon-->mu(+)mu(-). The measured angular distribution of the muons in the Upsilon(1S) rest frame is consistent with unpolarized meson production.

Uses and Abuses of Quarkonium Theory

We survey a few applications of recent theoretical ideas to problems in heavy quarkonium physics. We discuss the utility and limitations of fragmentation approximations for studying Psi and Upsilon production at several collider facilities. We also review the circumstances under which color-octet contributions to quarkonium cross sections are important. We emphasize that results obtained from methods stretched beyond their domains of validity should be regarded with caution.

J/ψspin asymmetries in the color-octet model

We investigate the pattern of asymmetries in the colour-octet model for inclusive production of charmonium with polarised initial state hadrons and photons. We find that singly polarised asymmetries vanish. The double polarised asymmetry for J/psi involves a new combination of long-distance matrix element. We also investigate the asymmetries for eta_c, chi_c and Upsilon production. The asymmetries distinguish well between different models of charmonium production.

Color-octet quarkonia production. II.

We calculate the lowest order hadronic cross sections for producing colored heavy quark-antiquark pairs in $L=S=0$ and $L=S=1$ configurations. Such $Q\Qbar[{}^1S_0^{(8)}]$ and $Q\Qbar[{}^3P_J^{(8)}]$ states hadronize into $\psi_\Q$ quarkonia at the same order in the NRQCD velocity expansion as previously considered $Q\Qbar[{}^3S_1^{(8)}]$ pairs. Their contributions to prompt Psi and Upsilon production at the Tevatron bring the shapes of theoretical transverse momentum distributions into line with recent CDF measurements. We find that the best fit values for the linear combinations of $Q\Qbar[{}^1S_0^{(8)}]$ and $Q\Qbar[{}^3P_J^{(8)}]$ long distance matrix elements which can be extracted from the data are generally consistent with NRQCD scaling rules.

Prompt psi and Upsilon production at LEP

Color-octet contributions to quarkonia production at LEP are studied herein. The short distance formation of heavy quark-antiquark pairs in color-octet configurations via gluon fragmentation processes is significantly enhanced relative to the creation of color-singlet pairs via heavy quark fragmentation. But the subsequent long distance hadronization of these colored pairs into physical quarkonium bound states is suppressed compared to the non-perturbative evolution of their colorless counterparts. We find that the overall LEP rates for gluon fragmentation into psi and Upsilon vector bosons exceed those from heavy quark fragmentation. Inclusion of the dominant color-octet quarkonium production channel reduces sizable discrepancies between previous predictions and recent measurements of prompt Z → J gy + X , Z → ψ′ + X and Z → Y + X branching fractions.

Aspects of psi and Upsilon production at supercollider energies.

We extend previous calculations of large-transverse-momentum $\ensuremath{\psi}$ and $\ensuremath{\Upsilon}$ production to Superconducting Super Collider energies. We then consider $\ensuremath{\psi}\ensuremath{\psi}$, $\ensuremath{\Upsilon}\ensuremath{\Upsilon}$, and $\ensuremath{\psi}\ensuremath{\Upsilon}$ production, both from the lowest-order (single-parton-interaction) gluon-fusion diagrams and from multiple-parton interactions. Finally, we discuss combined quarkonium and weak-boson production arising from both single- and multiple-parton interactions. Standard-model $W\ensuremath{\psi}$ and $W\ensuremath{\Upsilon}$ production is a potential background to the detection of charged Higgs bosons through their rare decays ${H}^{\ifmmode\pm\else\textpm\fi{}}\ensuremath{\rightarrow}{W}^{\ifmmode\pm\else\textpm\fi{}}V$.

Muon pairs and upper limit for upsilon production by 280 GeV muons

The high mass μ + μ − pairs produced by 280 GeV μ + on a carbon target are studied in a search for the Y production. The high mass continuum in the region 2–18 GeV is interpreted in terms of QED pair production and of μ pairs originating from the decay of hidden and open charm particles as well as of hadrons ( π, K) from deep inelastic interactions. The upper limit for the upsilon production by muons is found to be, at the 90% confidence level, σ γ·(γ→μ +μ −)<13·10 −39 cm 2/nucleon.

Measurement of Dimuon Production ats12=62GeV

Prompt dimuon production has been measured. Events with mass up to 25 GeV/c/sup 2/ are observed, as well as the J and UPSILON resonances. Cross sections are given for J and UPSILON production. For the continuum, the scaling function F(tau) is measured at very small values of ..sqrt..tau=m/..sqrt..s covering the range 0.05<..sqrt..tau<0.20.

First evidence for upsilon production by pions

We have measured the production of massive muon pairs in hadronic collisions at the CERN Super Proton Synchrotron (SPS). A clear signal of production of the ϒ resonance by π + of 200 GeV/ c and π − of 200 and 280 GeV/ c on a platinum target is observed.

Transverse-momentum distributions forϒand dimuon production in quantum chromodynamics

The effects of hard-gluon bremsstrahlung in dimuon and UPSILON production are studied. It is shown that in pp interactions the transverse-momentum distribution is broader for UPSILON production than for dimuon production. Furthermore, this difference increases markedly with energy. On the contrary, this effect should not be present for p-barp interactions. Predictions for ..pi../sup + -/ and K/sup + -/ beams are also discussed.

Γ production from duality and the charge of the new quark

Duality ideas are applied to estimate the upsilon production in e +e − annihilation, hadronic collisions and photoproduction. Simple scaling rules for the cross sections are obtained and compared with experiments. Our results suggest the charge of the new constituent quark is likely to be −1 3 .