P-wave Bottomonium Research Articles

Charmonia and bottomonia in asymmetric magnetized hot nuclear matter

We investigate the mass-shift of P-wave charmonium ( , ), and S and P-wave bottomonium ( , , , and ) states in magnetized hot asymmetric nuclear matter using the unification of QCD sum rules (QCDSR) and the chiral model. Within QCDSR, we use two approaches, i.e., the moment sum rule and the Borel sum rule. The magnetic field induced scalar gluon condensate and the twist-2 gluon operator calculated in the chiral ) model are utilised in QCD sum rules to calculate the in-medium mass-shift of the above mesons. The attractive mass-shift of these mesons is observed, which is more sensitive to magnetic field in the high density regime for charmonium, however less so for bottomonium. These results may be helpful to understand the decay of higher quarkonium states to the lower quarkonium states in asymmetric heavy ion collision experiments.

In-medium P-wave quarkonium from the complex lattice QCD potential

We extend our lattice QCD potential based study arXiv:1509.07366 (JHEP 1512 (2015) 101) of the in-medium properties of heavy quark bound states to P-wave bottomonium and charmonium. Similar to the behavior found in the S-wave channel their spectra show a characteristic broadening, as well as mass shifts to lower energy with increasing temperature. In contrast to the S-wave states, finite angular momentum leads to the survival of spectral peaks even at temperatures, where the continuum threshold reaches below the bound state remnant mass. We elaborate on the ensuing challenges in defining quarkonium dissolution, present estimates of melting temperatures for the spin averaged $\chi_b$ and $\chi_c$ states and contrast the findings to recent direct lattice NRQCD studies of P-wave quarkonium. As an application to heavy-ion collisions we estimate the contribution of feed down to S-wave quarkonium through the P-wave states after freezeout.

Lattice NRQCD study of S- and P-wave bottomonium states in a thermal medium withNf=2+1light flavors

We investigate the properties of $S$- and $P$-wave bottomonium states in the vicinity of the deconfinement transition temperature. The light degrees of freedom are represented by dynamical lattice quantum chromodynamics (QCD) configurations of the HotQCD collaboration with ${N}_{f}=2+1$ flavors. Bottomonium correlators are obtained from bottom quark propagators, computed in nonrelativistic QCD under the background of these gauge field configurations. The spectral functions for the ${^{3}S}_{1}$ ($\mathrm{\ensuremath{\Upsilon}}$) and ${^{3}P}_{1}$ (${\ensuremath{\chi}}_{b1}$) channel are extracted from the Euclidean time correlators using a novel Bayesian approach in the temperature region $140\text{ }\text{ }\mathrm{MeV}\ensuremath{\le}T\ensuremath{\le}249\text{ }\text{ }\mathrm{MeV}$ and the results are contrasted to those from the standard maximum entropy method. We find that the new Bayesian approach is far superior to the maximum entropy method. It enables us to study reliably the presence or absence of the lowest state signal in the spectral function of a certain channel, even under the limitations present in the finite temperature setup. We find that ${\ensuremath{\chi}}_{b1}$ survives up to $T=249\text{ }\text{ }\mathrm{MeV}$, the highest temperature considered in our study, and put stringent constraints on the size of the medium modification of $\mathrm{\ensuremath{\Upsilon}}$ and ${\ensuremath{\chi}}_{b1}$ states.

NLO corrections toχbJto two-J/ψexclusive decay processes

The next-to-leading order QCD corrections for $\chi_{bJ}$, the p-wave bottomonium, to $J/\psi$ pair decay processes are evaluated utilizing NRQCD factorization formalism. The scale dependence of $\chi_{b2}\rightarrow J/\psi J/\psi$ process is depressed with NLO corrections, and hence the uncertainties in the leading order results are greatly reduced. The total branch ratios are found to be the order of $10^{-5}$ for all three $\chi_{bJ}\rightarrow J/\psi J/\psi$ processes, indicating that they are observable in the LHC and super-B experiments.

J/Ψ inclusive production in χbJ(nP) decays

We study J/Ψ inclusive production in the decays of P-wave bottomonium χbJ(1P, 2P) for J = 0,1,2. Within the framework of the non-relativistic QCD (NRQCD) factorization method we calculate the contributions coming from four relevant processes including one color-singlet process and three color-octet ones, which are and . Our calculation shows that the color-octet processes, especially the gluon fragmentation one, contribute the most in the decays of χb0 and χb1. However, the J/Ψ production in the χb2 decay is dominated by the color-singlet process. Furthermore, the gluon fragmentation process gives a δ function in the energy fraction distribution of J/Ψ, which can be considered to be another characteristic for its identification. From our estimation the branching ratio for these processes is about 10−4 – 10−5, which indicates that J/Ψ inclusive production is detectable at B-factories. Studying these processes would help us to gain a deeper understanding of the color-octet mechanism.

Associated production ofΥand weak gauge bosons in hadron colliders

We calculate the rate of production of W+Upsilon and Z+Upsilon at the Tevatron. We find the cross sections at a center-of-mass energy of 1.8 TeV to be roughly 450 pb for W+Upsilon and 150 pb for Z+Upsilon. The dominant production mechanism involves the binding of a color-octet b-bbar pair into a P-wave bottomonium state which subsequently decays into Upsilon. The purely leptonic decay modes of Upsilon, W, and Z provide signatures with small backgrounds. In Run I of the Tevatron, the number of events in the purely leptonic decay channels before allowing for detector acceptances and efficiencies should be about 500 for W+Upsilon and about 60 for Z+Upsilon. We conclude that W+Upsilon events may be observable in the Run I data.

Decay rates of various bottomonium systems

Using the Bodwin—Braaten—Lepage factorization theorem in heavy quarkonium decay and production processes, we calculated matrix elements associated with S- and P-wave bottomonium decays via lattice QCD simulation' methods. In this work, we report preliminary results on the operator matching between the lattice expression and the continuum expression at one loop level. Phenomenological implications are discussed using these preliminary M S ¯ matrix elements.

Decays rates for S- and P-wave bottomonium

The authors use the Bodwin-Braaten-Lepage factorization scheme to separate the long- and short-distance factors that contribute to the decay rates of {Upsilon}, {eta}{sub b} (S-wave) and {chi}{sub b},h{sub b} (P-wave). The long distance matrix elements are calculated on the lattice in the quenched approximation using a non-relativistic formulation of the b quark dynamics.