Production of Charged Heavy Quarkonium-Like States at the LHC and Tevatron

Abstract

We study prompt hadroproduction of the charged bottomonium-like states Z ± b (10610) and Z ± b (10650), and the charged charmonium-like states Z ± c (3900) and Z ± c (4020), at the Tevatron and the LHC, provided that these states are S-wave hadronic molecules. Using two Monte Carlo event generators, Herwig and Pythia, to simulate the production of heavy meson pairs, we derive an order-of-magnitude estimate of the production rates for these four particles. Our estimates yield a cross section at the nb level for the Z b (10610) and Z b (10650). The results for the Zc(3900) and Zc(4020) are larger by a factor of 20 − 30. These cross sections are large enough to be observed, and measurements at hadron colliders in the future will supplement the study using electron-positron collisions, and therefore allow to explore the mysterious nature of these exotic states.PACS numbers: 13.85. Ni;14.40.Rt Introduction -In the past decade, a number of X, Y, Z states have been discovered at various experimental facilities, many of which may be exotics beyond the quark model [1]. Among these states, charged charmonium-like and bottomonium-like ones are of particular interest due to their genuine four-quark nature.In 2011, the Belle Collaboration reported a measurement of the π ± Υ(nS)(n = 1, 2, 3) and π ± h b (mP )(m = 1, 2) invariant mass spectra in the processes, in which two unexpected charged bottomonium-like structures Z ± b (10610) and Z ± b (10650) were discovered. Their masses from a fit using a BreitWigner type parameterization are very close to the BB * and B * B * thresholds, respectively. The angular distribution analysis indicates that their quantum numbers areRecently, the BESIII and Belle Collaborations have studied the process e + e − → π + π − J/ψ at the center-of-mass energy around 4.26 GeV, and found a charged charmonium-like state Z ± c (3900), with the central value of the measured mass being about 20 MeV above the DD * threshold [3,4]. The observation was confirmed later on by an analysis based on the CLEO data at the energy of 4.17 GeV [5]. Just above the D * D * threshold, there is evidence for another charged structure from the BESIII data in the h c π ± and D * D * mass distributions [6]. The masses and widths of these four states are collected in Tab. I. Apparently all of them defy a standard bottomonium/charmonium assignment, as they should consist of at least four quarks, e.g. bubd or cucd for the positively charged states.Due to the fact that the masses of the discovered states lie in the vicinity of meson-meson thresholds, it has been suggested that they are S-wave molecular states of heavy meson anti-heavy meson pairs with nearby thresholds, i.e. the B ( * )B * and the D ( * )D * (see Refs. [7][8][9][10][11][12][13] and many references therein). The fact that these four par- Zc(3900) Zc(4020) mass 10607.2 ± 2.0 10652.2 ± 1.5 3891.5 ± 3.5 4023.0 ± 2.3 width 18.4 ± 2.4 11.5 ± 2.2 39.2 ± 10.5 9.7 ± 3.2 ticles have a typical hadronic total width of a few tens of MeV has also triggered another four-qua...

Production of the bottom analogs and the spin partner of the X(3872) at hadron colliders

“…In our explicit realization, the 2 → 3 process can be generated initially through hard scattering, and the parton shower will produce more quarks via soft radiations. Following our previous work [30], we use Madgraph [33] to generate the 2 → 3 partonic events with a pair of a heavy quark and an antiquark (bb orcc) in the final states, and then pass them to the MC event generators for hadronization. We choose Herwig [34] and Pythia [35] as the hadronization generators, whose outputs are analyzed using the Rivet library [36].…”

“…See Reference [27] for a recent search in the ϒω final state. There have been works on the production of the exotic states, especially hadronic molecules, at hadron colliders [16][17][18][19][28][29][30][31]. In this paper, we will follow closely Reference [31], which uses effective field theory (EFT) to cope with the two-body hadronic final state interaction (FSI), and focus primarily on the production of the X b and its spin partner, a B * B * molecule with J PC = 2 ++ , denoted X b2 , at the LHC and the Tevatron.…”

Multiquark resonances

“…In any case, in Figure 3 one can appreciate that the slope of the deuteron is much steeper than the one of hypertriton, which is at odds with the naïve counting (6 quarks versus 9 quarks). The short-range nature of the production would also be inconsistent with the use of final state interactions to get the enhancement of two orders of magnitude needed to reach the experimental value of the cross section [36][37][38][39] -see also Appendix A.…”

“…Very little is know ab initio about the chromo-polarizability 38 . The only two quantities that have been estimated are the off-diagonal elements α However, in light of the definition (D.9), the chromo-polarizability should also satisfy the Schwartz inequality…”

More hidden heavy quarkonium molecules and their discovery decay modes

“…Besides this explanation, these states also have been identified as tetraquark states based on the fact that these particles have a typical hadronic total width of a few tens of MeV [17][18][19][20]. Besides the spectrum study, the production and decay of Z b states have also been investigated extensively [21][22][23][24][25][26][27][28][29][30]. On one hand, the molecular description can explain the existing data on…”