Scalar or Vector Tetraquark State Candidate: Z_c(4100)*

Abstract

In this article, we separate the vector and axialvector components of the tensor diquark operators explicitly, construct the axialvector-axialvector type and vector-vector type scalar tetraquark currents and scalar-tensor type tensor tetraquark current to study the scalar, vector and axialvector tetraquark states with the QCD sum rules in a consistent way. The present calculations do not favor assigning the Zc(4100) to be a scalar or vector tetraquark state. If the Zc(4100) is a scalar tetraquark state without mixing effects, it should have a mass about 3.9 GeV or 4.0 GeV rather than 4.1 GeV; on the other hand, if the Zc(4100) is a vector tetraquark state, it should have a mass about 4.2 GeV rather than 4.1 GeV. However, if we introduce mixing, a mixing scalar tetraquark state can have a mass about 4.1 GeV. As a byproduct, we obtain an axialvector tetraquark candidate for the Zc(4020).

Light isovector resonances in π−p→π−π−π+p at Aghasyan1, Alexeev2, Alexeev3 et al. 2018Phys. Rev. D717970View full textAdd to dashboardCite

“…Fit model with 11 resonances to describe the elements of the spin-density matrix of the selected 14 partial waves from six J PC sectors using Eq. (20). The relative intensities listed in the second column are evaluated as a sum over the 11 t 0 bins and are normalized to the total number of acceptance-corrected events [30].…”

“…Here, b and the c i are the free shape parameters for the nonresonant component j. 20 The parameters m norm and m thr are the same for all nonresonant components and are empirically fixed to 1 GeV=c 2 and 0.5 GeV=c 2 , respectively. The quasi-two-body breakup momentum for the decay X − → ξ 0 π − is represented byq ξπ ðm 3π Þ.…”

“…Our recent observation of a new axial-vector resonancelike structure, the a 1 ð1420Þ, with the same quantum numbers as the elusive a 1 ð1260Þ [19] has spurred much work on the interpretation of states (including heavy-quark states), for which the assignment to quark-model multiplets is unclear; see e.g., Refs. [20][21][22][23][24][25][26][27][28][29]. The present study uses the same data but yields more accurate resonance parameters.…”

“…We follow this approach and have chosen the 3π production probability in Eq. (20) to be proportional to the probability of Pomeron emission by the target proton:…”

The Spectrum of Light Isovector Mesons with C = +1 from the COMPASS Experiment

“…Similarly, the interpretation of many states is controversial, as is the case e.g. for the new axial-vector state a 1 (1420) observed by COMPASS [5], which appears with the same quantum numbers as the elusive a 1 (1260) [6][7][8][9][10]. Mesons are characterized by their quantum numbers, isospin I and J P C , with J being the total spin, P the parity and C the charge conjugation quantum number [a] .…”