Nonrelativistic QCD analysis of bottomonium production at the Fermilab Tevatron

Abstract

Recent data from the CDF collaboration on the production of spin-triplet bottomonium states at the Tevatron pp collider are analyzed within the NRQCD factorization formalism. The color-singlet matrix elements are determined from electromagnetic decays and from potential models. The color-octet matrix elements are determined by fitting the CDF data on the cross sections for Υ(1S), Υ(2S), and Υ(3S) at large p T and the fractions of Υ(1S) coming from χ b (1P ) and χ b (2P ). We use the resulting matrix elements to predict the cross sections at the Tevatron for the spin-singlet states η b (nS) and h b (nP ). We argue that η b (1S) should be observable in Run II through the decay η b → J/ψ + J/ψ.

High transverse momentum quarkonium production and dissociation in heavy ion collisions

“…We take the mass of the charm quark, m charm = 1.4GeV [16]. The values of the color-singlet operators for bottomonia are given in [15], which we reproduce here:…”

“…Since these are short distance operators, they can be calculated in perturbation theory. We use the expressions for the short distance color-singlet cross sections given in [47,48] and the color-octet cross sections given in [13][14][15]. The case of the p-wave bound states (χ c0 , χ c1 , and χ c2 , sometimes collectively referred to as χ cJ , and the corresponding states of the b quark) is slightly different.…”

“…Higher Fock components in the wavefunction have additional partons and are suppressed by positive powers of the small parameter v. In our calculation we will take into account both color-singlet and color-octet QQ contributions in the production. The NRQCD formalism has been used to calculate differential yields of heavy mesons as a function of their transverse momentum, p T , in p+p collisions [12][13][14][15][16]. The picture of the production process in NRQCD is as follows.…”

Which hadronic decay modes are good forηbsearching: DoubleJ/ψor something else?

“…The product of acceptance and efficiency for detecting J/ψ decay to µ + µ − is estimated to be ǫ ≈ 0.1 [16], which is perhaps a conservative estimate for LHC. Multiplying the number of the produced events by ǫ 2 , we expect between 1 and 10 observed events per year.…”

“…Encouraged by the large observed width of η c → V V (V stands for light vector mesons), Braaten, Fleming and Leibovich (hereafter BFL) have suggested that the analogous decay process η b → J/ψJ/ψ, followed by both J/ψ decays to muon pairs, may be used as a very clean trigger to search for η b at Tevatron Run 2 [16]. Assuming Br[η b → J/ψJ/ψ] ∼ 1/m 4 b , they rescale the measured branching ratio of η c → φφ by a factor of (m c /m b ) 4 to estimate 1 Br[η b → J/ψJ/ψ] = 7 × 10 −4±1 .…”